CN104253954A

CN104253954A - Low-power-consumption constant-current and backlight control circuit and television

Info

Publication number: CN104253954A
Application number: CN201410476651.8A
Authority: CN
Inventors: 吴永芳; 刘威河; 廖武; 杨达富
Original assignee: Guangzhou Shiyuan Electronics Thecnology Co Ltd
Current assignee: Guangzhou Kun Electronic Technology Co. Ltd.
Priority date: 2014-09-17
Filing date: 2014-09-17
Publication date: 2014-12-31
Anticipated expiration: 2034-09-17
Also published as: CN104253954B

Abstract

The invention discloses a low-power-consumption constant-current and backlight control circuit. The low-power-consumption constant-current and backlight control circuit comprises a front-end power supply circuit and a rear-end linear constant-current circuit, wherein the front-end power supply circuit comprises a power supply circuit and a feedback adjusting circuit; the rear-end linear constant-current circuit is provided with a connecting reference signal input end which is used for connecting constant-current reference voltage and for conducting/disconnecting the connection between the rear-end linear constant-current circuit and an LED (Light Emitting Diode) lamp string to be supplied with power according to the constant-current reference voltage; a loop of voltage acquisition output end is led out through a voltage detection circuit from the connecting position of the rear-end linear constant-current circuit and the LED lamp string to be supplied with power to acquire the voltage at the connecting position, the voltage value of a control signal input end is adjusted according to the acquisition result, the voltage detection circuit comprises a diode and a pull-up resistor, a cathode of the diode is connected with the cathode of the LED lamp string, an anode of the diode is connected with one end of the pull-up resistor and the other end of the pull-up resistor is connected with a high level; the anode of the diode is connected with the voltage acquisition output end.

Description

The constant current of low-power consumption and backlight control circuit and television set

Technical field

The present invention relates to Energy control technical field, particularly relate to a kind of constant current and backlight control circuit of low-power consumption and there is the constant current of this low-power consumption and the television set of backlight control circuit.

Background technology

Linear constant-current modulation circuit is widely used a kind of element circuit in analog integrated circuit, has a wide range of applications in practice.Wherein, in the Energy control technical field of LED television, often utilize the power supply that front-end circuit exports constant voltage, back-end circuit realizes boosting or step-down constant current realizes TV SKD and LED-backlit.

Carrying out in integration process to television components, TV SKD and backlight lamp bar need to form a complete production network usually, and the different backlight LED light bars of quantity exports different magnitudes of voltage by needing linear constant-current modulation circuit adaptability.Adopt in prior art one and TV SKD to power the feedback loop that output is connected, the change in voltage of timely monitoring television main board power supply output.

As shown in Figure 1, be the schematic diagram of a kind of linear constant-current modulation circuit that prior art provides.When the output voltage of main board power supply output raises, be linked in the reference input R0 of voltage-stabiliser tube TL431 by the voltage signal after resistance RB135 and resistance RB134 dividing potential drop, and the reference voltage (as 2.5V) of this voltage signal and voltage-stabiliser tube TL431 inside is made comparisons, voltage between voltage-stabiliser tube TL431 anode and cathode is reduced, and then the ER effect of optocoupler diode PCB101A is large, dynamic electric resistor between collector electrode and emitter diminishes, voltage step-down between collector electrode and emitter, internal transformer output voltage thereupon in power supply circuits is reduced to the voltage of setting.Therefore, along with the increase of resistance RB134 resistance, LED power output and main board power supply output output voltage reduce, otherwise voltage raise.

Due to the difference of application scenario, in actual production process, often need linear constant current circuit to export different magnitudes of voltage, and prior art is in order to satisfied different occasion needs, needs to adjust the resistance of the resistance RB135 in hardware circuit.Therefore, there is trivial operations, precision is low, power consumption is high and cost is high defect in prior art.In addition, in actual applications, backlight LED light bars is formed by multiple LED strip connection, and controls by the switching tube of metal-oxide-semiconductor or triode the constant current hold adjusting LED string.When after linear constant current circuit work, switching tube both end voltage can (general single LEDs scope be 2.8 ~ 3.4 because of LED string voltage error, owing to connecting many, so the difference of the upper and lower bound of the voltage range of LED string can be larger), because the intermodulation (general range is 7%) of transformer affects, the higher power consumption of voltage is larger, and this can cause the cost increase of device and the reduction of circuit efficiency.In addition, in order to reduce the temperature of switching tube, general switching tube can be managed by multiple mos or triode parallel connection uses, and which results in the increase of cost.

Summary of the invention

Technical problem to be solved by this invention is, provides a kind of constant current and backlight control circuit of low-power consumption, adjusts LED adaptively and to power the magnitude of voltage of output, without the need to adjusting hardware circuit, and the phenomenon of still glimmer when can prevent LED-backlit from closing.

For solving above technical problem, the invention provides a kind of constant current and backlight control circuit of low-power consumption, it is characterized in that, comprising: front end power circuit and rear end linear constant current circuit;

Described front end power circuit comprises power supply circuits and feedback adjusting circuit; Described power supply circuits comprise the first power supply output, the second power supply output and FEEDBACK CONTROL end; Described feedback adjusting circuit comprises feedback input end, control signal input and feedback signal output; Described feedback input end and described second output of powering is connected, and described feedback signal output is connected with described power supply circuits; Described feedback adjusting circuit is according to the magnitude of voltage of described control signal input, the signal received described feedback input end adjusts with to described power supply circuits output feedback signal, thus controls the magnitude of voltage of described power supply circuits to described first power supply output and described second power supply output and adjust;

Described rear end linear constant current circuit is connected with the negative electrode of LED string to be powered, and the anode and described first of described LED string to be powered output of powering is connected;

Described rear end linear constant current circuit is provided with a connection reference signal input to access constant current reference voltage, and the connection of rear end linear constant current circuit and described LED string to be powered according to the size ON/OFF of described constant current reference voltage;

A road voltage acquisition output is drawn to gather the voltage of this junction by voltage detecting circuit in linear constant-current circuit and described LED string junction to be powered in the rear, and adjusts the magnitude of voltage of described control signal input according to collection result;

Described voltage detecting circuit comprises diode and pull-up resistor, and the negative electrode of described diode is connected to the negative electrode of described LED string, and anode is connected to one end of pull-up resistor, the other end access high level of pull-up resistor; The anode of described diode connects described voltage acquisition output.

Preferably, the anode of described diode also connects described voltage acquisition output by a resistance.

Preferably, the anode of described diode also connects described voltage acquisition output by another diode; The anode of another diode described is connected with the anode of described diode; The negative electrode of another diode described is as described voltage acquisition output.

Preferably, described voltage detecting circuit also comprises a filter circuit of pressure-stabilizing; Described filter circuit of pressure-stabilizing is connected between described voltage acquisition output and ground;

Described filter circuit of pressure-stabilizing comprises voltage stabilizing didoe in parallel, filter capacitor and filter resistance; And the negative electrode of described voltage stabilizing didoe is connected on described voltage acquisition output, the plus earth of described voltage stabilizing didoe.

Preferably, described rear end linear constant current circuit comprises and compares Circuit tuning and constant-current control circuit; Described constant-current control circuit at least comprises a switching tube and control circuit module; The described Circuit tuning that compares comprises operational amplifier, the reverse input end of described operational amplifier connects described reference signal input, positive input connection detects grounding through resistance by constant current, and the output of described operational amplifier passes through the control end of switching tube described in described control circuit model calling; The input of described switching tube is connected with the negative electrode of described LED string to be powered, and the output of described switching tube detects grounding through resistance by described constant current.

Preferably, when described switching tube is triode, the collector electrode of described triode is connected with one end of described LED string to be powered, and emitter detects grounding through resistance by described constant current, and base stage is connected with the output of described operational amplifier by described control circuit module;

When described switching tube is field-effect transistor, the drain electrode of described field-effect transistor is connected with one end of described LED string to be powered, source electrode detects grounding through resistance by described constant current, and grid is by the output of described control circuit module and described operational amplifier.

Preferably, described constant current detect resistance primarily of resistance (RB6), resistance (RB7), resistance (RB8) is in parallel with resistance (RB9) forms.

Preferably, the normal phase input end of described operational amplifier detects resistance by resistance (RB5) with described constant current and is connected, and the output of described switching tube is connected to the junction that described resistance (RB5) and described constant current detect resistance.

Preferably, the normal phase input end of described operational amplifier is also by electric capacity (CB5) ground connection.

Preferably, the described Circuit tuning that compares also comprises a clamp diode;

The minus earth of described clamp diode; The anode of described clamp diode is connected with the output of described switching tube.

Preferably, only when the voltage of this junction that described voltage acquisition output collects is more than or equal to default threshold value, just adjust the magnitude of voltage of described control signal input, thus adjust the output voltage of described first power supply output, the second power supply output further, be less than default threshold value to make the voltage of this junction.

Preferably, a control master chip is also comprised;

Described control master chip is connected respectively with described control signal input, described reference signal input and described voltage acquisition output;

Described control master chip, according to the change in voltage of described voltage acquisition output, adjusts the output to the signal magnitude of described control signal input, to control the first power supply output of described front end power circuit, the output voltage values of the second power supply output; And input described constant current reference voltage by described reference signal input to described rear end linear constant current circuit.

Preferably, when described control master chip detects that the voltage difference of described voltage acquisition output and described reference signal input is greater than default threshold value, the voltage signal duty ratio exporting described control signal input to reduces by described control master chip.

Preferably, described control master chip comprises analog to digital converter, for the voltage signal of described control master chip access is converted to digital signal.

Preferably, described power supply circuits comprise power supply input circuit, switching power circuit, multiple-channel output transformer, LED power output circuit and main board power supply output circuit;

The power supply signal of access is transferred to described multiple-channel output transformer by described power supply input circuit under the control of described switching power circuit;

Described multiple-channel output transformer comprises main winding and auxiliary winding; Described main winding transfers to described main board power supply output circuit by after described power supply signal transformation, and is exported by described second power supply output; Described auxiliary winding to be powered transferring to described LED after synchronous for described power supply signal transformation output circuit, and is exported by described first power supply output; The coil ratio of described main winding and described auxiliary winding is 1:N, N > 0.

Preferably, described feedback adjusting circuit comprises opto-coupled feedback unit, voltage stabilizing reference cell, voltage sampling unit and voltage-adjusting unit;

Described opto-coupled feedback unit comprises optocoupler, and described optocoupler comprises the light-emitting diode being positioned at former limit and the optical signal converter being positioned at secondary, and the signal input part of described light-emitting diode connects described feedback input end by the first resistance (RB131); The signal output part of described optical signal converter connects described feedback signal output;

Described voltage sampling unit comprises the 4th resistance (RB134) and the 5th resistance (RB135) of the series connection be connected between described feedback input end and ground;

Described voltage stabilizing reference cell comprises voltage stabilizing standard and is connected to the voltage stabilizing feedback circuit between the reference input of voltage stabilizing standard and negative electrode; The reference input of described voltage stabilizing standard is connected to place between the 4th resistance (RB134) and the series connection of the 5th resistance (RB135), plus earth, and negative electrode connects the signal output part of described light-emitting diode;

Described voltage-adjusting unit comprises the 6th resistance (RB150), one end of described 6th resistance (RB150) is connected to place between described 4th resistance (RB134) and the series connection of the 5th resistance (RB135), and the other end connects described control signal input.

Preferably, described voltage stabilizing feedback circuit comprises the first electric capacity (CB109) and the 3rd resistance (RB133);

One end of described first electric capacity (CB109) is connected on the negative electrode of described voltage stabilizing standard, and the other end is connected with one end of the 3rd resistance (RB133); The other end of the 3rd resistance (RB133) is connected on the reference input of described voltage stabilizing standard.

Preferably, described voltage stabilizing feedback circuit comprises the second electric capacity (CB110);

One end of described second electric capacity (CB110) is connected on the negative electrode of described voltage stabilizing standard, and the other end is connected on the reference input of described voltage stabilizing standard.

Preferably, described voltage stabilizing feedback circuit comprises the first electric capacity (CB109), the 3rd resistance (RB133) and the second electric capacity (CB110);

One end of described first electric capacity (CB109) is connected on the negative electrode of described voltage stabilizing standard, and the other end is connected with one end of the 3rd resistance (RB133); The other end of the 3rd resistance (RB133) is connected on the reference input of described voltage stabilizing standard;

Preferably, the output voltage corresponding relation of the magnitude of voltage of described control signal input and the power supply output of described power supply circuits is: during every stepping 1% duty ratio of the magnitude of voltage of described control signal input, the output voltage change 0.01V of described first power supply output, and the output voltage change 0.1V of described second power supply output.

Preferably, the scope of the magnitude of voltage of described control signal input is voltage signal or the PWM ripple of 0V ~ 3.3V, the output voltage correspondence of described first power supply output is adjustable as 11.5V ~ 12.5V, and the output voltage automatic adaptation of described second power supply output.

Present invention also offers a kind of television set, comprising: TV SKD, backlight LED light string, and the constant current of low-power consumption as above and backlight control circuit;

The constant current of described low-power consumption and backlight control circuit are connected respectively with described TV SKD and described backlight LED light string, for when turning on the power supply of described television set, according to the operating voltage of described backlight LED light string, Automatic adjusument supplies the voltage signal of described TV SKD, described backlight LED light string; When closing the power supply of described television set, turn off the electric current flowing through described backlight LED light string.

The constant current of a kind of low-power consumption provided by the invention and backlight control circuit and television set, be provided with front end power circuit and rear end linear constant current circuit, front end power circuit is utilized to regulate the supply power voltage of two-way output, and feedback adjusting circuit is set up in the power circuit of front end, and in feedback adjusting circuit, be provided with control signal input, to realize controlling the front end power circuit voltage at the first power supply output and the second power supply output, and the change by setting up rear end linear constant current circuit automatically to adapt to the LED backlight quantity of connecting, the magnitude of voltage of described control signal input can be adjusted according to the magnitude of voltage after LED backlight series connection, thus by the first power supply output described in front end power circuit and feedback adjusting control circui thereof, the output voltage of the second power supply output, and the first power supply output is connected to LED backlight and powers, achieve the voltage automation adapted with LED backlight quantity to regulate, reduce the power consumption of circuit switch element, also contacted by the diode (DB2) of voltage detecting circuit and backlight LED light and connect, when LED string is opened, diode (DB2) conducting, voltage detecting circuit detects the operating voltage of LED string, thus the described first power supply output of described feedback circuit adjustment can be controlled, the output voltage of the second power supply output, when described LED string is closed, diode (DB2) oppositely ends, turn off the electric current flowing through described LED string completely, therefore the present invention can when backlight open, the operating voltage of normal acquisition LED string, when receiving the order of closing backlight LED, LED string two ends are equivalent to open circuit, LED, without glimmer phenomenon, avoids the useful life of unnecessary power consumption penalty and raising backlight LED.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of a kind of linear constant-current modulation circuit that prior art provides.

Fig. 2 is the structural representation of the constant current of low-power consumption provided by the invention and an embodiment of backlight control circuit.

Fig. 3 is that a kind of of front end provided by the invention power circuit can the schematic diagram of implementation.

Fig. 4 is a kind of physical circuit schematic diagram of front end provided by the invention power circuit.

Fig. 5 is that a kind of of rear end provided by the invention linear constant current circuit can the circuit theory diagrams of implementation.

Fig. 6 is that the another kind of rear end provided by the invention linear constant current circuit can the circuit theory diagrams of implementation.

Fig. 7 is that a kind of of voltage detecting circuit provided by the invention can the physical circuit figure of implementation.

Fig. 8 is that the another kind of voltage detecting circuit provided by the invention can the physical circuit figure of implementation.

Fig. 9 is the structural representation of the constant current of low-power consumption provided by the invention and the another embodiment of backlight control circuit.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described.

See Fig. 2, it is the structural representation of the constant current of low-power consumption provided by the invention and an embodiment of backlight control circuit.

In the present embodiment, the constant current of described low-power consumption and backlight control circuit comprise front end power circuit 101, rear end linear constant current circuit 103 and voltage detecting circuit 104.

Described front end power circuit 101 comprises power supply circuits 1011, first power supply output OUT1, the second power supply output OUT2 and feedback adjusting circuit 1012;

Wherein, described feedback adjusting circuit 1012 comprises feedback input end A_in, control signal input Cont and feedback signal output B_out; Described feedback input end A_in and the described second output OUT2 that powers is connected, and described feedback signal output B_out is connected with described power supply circuits 1011; Described feedback adjusting circuit 1012 is according to the magnitude of voltage of described control signal input Cont, to described power supply circuits 1011 output feedback signal, adjust to control the magnitude of voltage of described power supply circuits 1011 to described first power supply output OUT1 and described second power supply output OUT2.

Described rear end linear constant current circuit 103 is connected with the negative electrode LED-of LED string to be powered, and the anode LED+ and described first of the described LED string to be powered output OUT1 that powers is connected.

Described rear end linear constant current circuit 103 is provided with a connection reference signal input PWM_REF to access constant current reference voltage, and the connection of rear end linear constant current circuit 103 and described LED string to be powered according to the size ON/OFF of described constant current reference voltage.

Linear constant-current circuit 103 draws a road voltage acquisition output terminals A DC to gather the voltage of this junction with described LED string junction P to be powered by voltage detecting circuit 104 in the rear, and adjust the magnitude of voltage of described control signal input Cont according to collection result, thus adjust the output voltage of described first power supply output OUT1, the second power supply output OUT2 further;

Described voltage detecting circuit 104 comprises diode DB2 and pull-up resistor RB18, the negative electrode of described diode DB2 is connected to the negative electrode LED-of described LED string, the anode of diode DB2 is connected to one end of pull-up resistor RB18, the other end access high level of pull-up resistor RB18; The anode of described diode DB2 connects described voltage acquisition output terminals A DC.As shown in Figure 2, a road output is drawn in rear end linear constant current circuit 103 and the junction P of LED string negative electrode, be connected with diode DB2 negative electrode, when described LED string is opened, diode DB2 conducting, described voltage detecting circuit 104 detects the operating voltage of described LED string by diode DB2, thus controls the output voltage that described feedback circuit 1012 adjusts described first power supply output OUT1, the second power supply output OUT2; When described LED string is closed, diode DB2 oppositely ends, and turns off the electric current flowing through described LED string.

Particularly, the constant current of the low-power consumption that the present embodiment provides and the main operational principle of backlight control circuit are: when opening backlight of television power supply, the contact voltage of the P point connect of rear end linear constant current circuit 103 and LED is less than 3.3V usually, meanwhile, the access of high level VCC makes the voltage V of the tie point of diode DB2 and resistance RB18 _ahigher than the voltage of P point, therefore, diode DB2 conducting, circuit carries out work by resistance RB18, diode DB2 and switching tube QB1 loop.Now, the voltage V of the tie point of diode DB2 and resistance RB18 _a=V _dB2+ V _qB1, wherein, V _dB2when representing that electric current flows through diode DB2 in the input of diode DB2, export the pressure drop that two ends are formed, V _qB1when representing that electric current flows through switching tube QB1 in the input of switching tube QB1, export the pressure drop that two ends are formed.When closing television machine backlight electric power, rear end linear constant current circuit 103 and LED string disconnect, LED string two ends are subject to the impact of constant voltage circuit and there is the high level much larger than 3.3V at LED-end, therefore diode DB2 oppositely ends, open circuit is equivalent between LED string and voltage detecting circuit 104, namely LED string will pass through without weak current, thus also can not produce glimmer phenomenon.

Referring to Fig. 3, be that a kind of of front end provided by the invention power circuit can the schematic diagram of implementation.

As shown in Figure 3, feedback adjusting circuit 1012 can be provided with optocoupler PCB101, pressurizer UB102 and be connected to described second power supply output OUT and ground between and primarily of series connection resistance RB134 and resistance RB135 form voltage sampling circuit.

Wherein, described optocoupler PCB101 comprises the light-emitting diode (i.e. the pin 1 of optocoupler PCB101 and the assembly of pin 2) being positioned at former limit and the optical signal converter (i.e. the pin 3 of optocoupler PCB101 and the assembly of pin 4) being positioned at secondary.

The control signal that described control signal input inputs is accessed to the light-emitting diode being positioned at former limit of optocoupler PCB101 by pressurizer UB102; Described light-emitting diode is passed to the optical signal converter being positioned at secondary of described optocoupler PCB101 after control signal is converted to light signal; Described optical signal converter exports described feedback signal output to after light signal is converted to the signal of telecommunication.

Wherein, described optocoupler PCB101 comprises the Light-Emitting Diode being positioned at former limit and the optical signal converter being positioned at secondary, the input (pin 1) being positioned at the Light-Emitting Diode on former limit is connected as feedback input end A_in and the second output OUT that powers by resistance R131, and the two ends, former limit of optocoupler PCB101 (pin 1 and pin 2) is in parallel with resistance R132; The output (pin 4) being positioned at the optical signal converter of the secondary of optocoupler PCB101 connects and is connected with the FEEDBACK CONTROL end feedback of power supply circuits 1011 as feedback signal output B_out, the other end (pin 3) ground connection of optical signal converter.It should be noted that, resistance RB132 is not the necessary electronic component in the feedback circuit in the present embodiment.

Pressurizer UB102 preferably adopts the accurate pressurizer of adjustable, and the reference voltage of built-in 2.5V (volt), particularly, model can be adopted to be that the pressurizer of TL431 realizes.Wherein, the anode A ground connection of described adjustable precision shunt pressurizer, negative electrode K is connected with the light-emitting diode being positioned at former limit of described optocoupler PCB101; Reference input R is for accessing the control signal of described control signal input Cont.

As shown in Figure 3, the negative electrode K of pressurizer UB102 is connected with Light-Emitting Diode 2 pin on the former limit of optocoupler PCB101, the anode A ground connection of pressurizer UB102; Voltage stabilizing feedback circuit is provided with between the reference input (pin 1) of voltage stabilizing standard UB102 and negative electrode (pin 3); The reference input reference input (pin 1) of described voltage stabilizing standard UB102 is connected to place between resistance RB134 and resistance RB135 series connection, anode (pin 2) ground connection of voltage stabilizing standard UB102, the negative electrode (pin 3) of voltage stabilizing standard UB102 connects the former limit other end (pin 2) of described optocoupler PCB101.

In the attainable mode of one, described voltage stabilizing feedback circuit comprises electric capacity CB109 and resistance RB133; One end of described electric capacity CB109 is connected on the negative electrode K of described adjustable precision shunt pressurizer, and the other end is connected with one end of resistance RB133; The other end of resistance RB133 is connected on the reference input R of described adjustable precision shunt pressurizer.

In the attainable mode of another kind, described voltage stabilizing feedback circuit comprises electric capacity CB110; One end of described electric capacity CB110 is connected on the negative electrode K of described adjustable precision shunt pressurizer, and the other end is connected on the reference input R of described adjustable precision shunt pressurizer.

Further, above two kinds of implementations can combine by the present embodiment, to realize described voltage stabilizing feedback circuit.Namely described voltage stabilizing feedback circuit is provided with electric capacity CB109, resistance RB133 and electric capacity CB110 simultaneously.

As shown in Figure 3, the negative electrode K of pressurizer UB102 is connected with light-emitting diode 2 pin on the former limit of optocoupler PCB101, the anode A ground connection of pressurizer UB102; One end of resistance RB134 is connected with the reference input R of pressurizer UB102, other end ground connection; One end of electric capacity CB109 is connected on the negative electrode K of described adjustable precision shunt pressurizer, and the other end is connected with one end of resistance RB133; The other end of resistance RB133 is connected on the reference input R of described adjustable precision shunt pressurizer; One end of described electric capacity CB110 is connected on the negative electrode K of described adjustable precision shunt pressurizer, and the other end is connected on the reference input R of described adjustable precision shunt pressurizer.

Further, the reference input R of described adjustable precision shunt pressurizer is connected with described control signal input by a voltage divider.In the present embodiment, preferably, described voltage divider is a resistance RB150.

As shown in Figure 3, electric capacity CB109 one end is connected with 2 pin of optocoupler PCB101 feedback input end A_in, and be connected with one end of resistance RB150 after the other end and resistance RB133 connect, the other end of resistance RB150 is as described control signal input Cont; One end of electric capacity CB110 is connected with the negative electrode K of pressurizer UB102, and the other end is connected with the reference input R of pressurizer UB102; One end of resistance RB135 is connected with feedback input end A_in, and the other end is connected with the reference input R of pressurizer UB102.Thus, a kind of concrete execution mode of feedback circuit 1012 is constituted.

Feedback adjusting circuit 1012 shown in Fig. 3 is with the main improvement of the existing feedback adjusting circuit shown in Fig. 1, the reference input R of pressurizer UB102 increases a resistance RB150, introduce the output voltage values of a control signal to the negative electrode K of pressurizer UB102 by control signal input Cont simultaneously and carry out Automated condtrol, thus the adjustment to power supply circuits 1011 and output voltage thereof can be realized.

Referring to Fig. 4, it is a kind of physical circuit schematic diagram of front end provided by the invention power circuit.

Described power supply circuits 1011 comprise power supply input circuit 11, switching power circuit 12, multiple-channel output transformer TB101, LED power output circuit 13 and main board power supply output circuit 14;

The power supply signal of access is transferred to described multiple-channel output transformer TB101 by described power supply input circuit 11 under the control of described switching power circuit 12; As shown in Figure 4, described multiple-channel output transformer TB101 comprises main winding and auxiliary winding.Wherein, the coil of 9 pin ~ 11 pin of multiple-channel output transformer TB101 forms elementary main winding, and the coil of 1 pin ~ 2 pin of multiple-channel output transformer TB101 forms secondary main winding; The coil of 7 pin ~ 8 pin of multiple-channel output transformer TB101 forms elementary auxiliary winding, the coil of 1 pin ~ 6 pin of multiple-channel output transformer TB101 forms secondary auxiliary winding (coil wherein between 1,2 pin shares), and can common sparing winding between secondary major-minor winding, also can not share.During concrete enforcement, described main winding transfers to described main board power supply output circuit 14 by after described power supply signal transformation, and is exported by described second power supply output OUT2; Described auxiliary winding to be powered transferring to described LED after synchronous for described power supply signal transformation output circuit 13, and is exported by described first power supply output OUT1; Therefore, multiple-channel output transformer TB101 in Fig. 4 has two output voltage, especially, in technical field of television sets, first power supply output OUT1 is preferably the power supply output of supply LED backlight, and the second power supply output OUT2 is preferably the power supply output of supply TV SKD.

In the present embodiment, the output voltage of multiple-channel output transformer TB101 every circle coil is identical, and when changing the output voltage on a wherein road, so the output voltage on another road also synchronously will follow change.Such as, the coil of main winding is 2 circles, and output voltage is 12V, and namely the output voltage of every circle coil is 6V; Suppose that the output voltage of auxiliary winding is 120V, then the coil turn of auxiliary winding is 20 circles.And the coil turn of main winding and auxiliary winding can adjust according to practical application, namely the coil ratio of described main winding and described auxiliary winding is 1:N, N > 0, namely when the output voltage of main winding is V1, the output voltage of auxiliary winding is V2=N*V1.

It should be noted that, the feedback input end A_in of feedback adjusting circuit 1012 can connect the first power supply output OUT1 or second power supply output OUT2 of described power supply circuits 1011, does not affect the enforcement of the present embodiment.

The size of the external control signal that the present invention accesses by the control signal input Cont of feedback adjusting circuit 1012, thus the magnitude of voltage controlling the first power supply output OUT1 or second power supply output OUT2.Particularly, be connected to the second power supply output OUT2 of described power supply circuits 1011 for the feedback input end A_in of described feedback adjusting circuit 1012, the basic functional principle of the present embodiment is mainly:

When the output voltage of power supply circuits 1011 raises (the first power supply output OUT1 and second power supply output OUT2 raises) simultaneously, the control signal of the control signal input Cont voltage transmission after resistance RB135 and resistance RB134, resistance RB150 dividing potential drop compares to the reference input R of pressurizer UB102, pressurizer UB102 with reference to the signal value of input R and its internal reference voltage.When the signal value of reference input R is greater than reference voltage, voltage between pressurizer UB102 anode and cathode reduces, and then the electric current of optocoupler PCB101A increases, between optocoupler PCB101B collector electrode and emitter, dynamic electric resistor diminishes (4 pin of the current collection of optocoupler PCB101 very optocoupler, launch 3 pin of very optocoupler), the voltage step-down between collector electrode and emitter; PWM (the Pulse Width Modulation thereupon connected, pulse width modulation) the level step-down of feedback pin COMP of control chip UB101, pwm chip UB101 output duty cycle reduces, thus the output voltage of multiple-channel output transformer TB101 is reduced.Otherwise, when the signal value of reference input R is less than reference voltage, the output voltage of multiple-channel output transformer TB101 can be made to raise.

Therefore, the size of voltage signal accessed for regulating the reference input R of pressurizer UB102 thus the output voltage of control transformer TB101, the present invention is by increasing resistance RB150 and realizing this purpose at the side incoming control signal of resistance RB150.Particularly, to power the output voltage of output OUT2 when needing modulation second, and the internal reference voltage of pressurizer UB102 is when being 2.5V, the output voltage values computing formula of the second power supply output is: Vout2=reference voltage * (1+R135/R134), wherein, reference voltage is preferably 2.5V.Preferably, export a PWM_12V signal to described control signal input Cont by external control chip, via resistance RB150 by PWM_12V Signal transmissions to series connection point between resistance RB134 and resistance RB135 (i.e. the reference input R of pressurizer UB102).

During concrete enforcement, the PWM_12V signal of control signal input Cont can adopt any one constant voltage values in 0-3.3V, or, adopt PWM (Pulse Width Modulation, the pulse width modulation) ripple of certain waveform.Output voltage values computing formula according to the second power supply output: Vout2=reference voltage * (1+R135/R134), when PWM_12V signal exports as 3.3V, the output voltage of the second power supply output OUT2 is minimum, because the input voltage (3.3v) of control signal input Cont is greater than the reference voltage 2.5V (when circuit stability work 1 pin voltage and reference voltage almost equal) of pressurizer UB102, so be the equal of now that resistance RB150 receives on the power supply of 3.3V, resistance RB150 is namely equivalent to be connected in parallel on resistance RB135, according to the voltage equation of Vout2, due to resistance RB135 resistance RB150 in parallel, the equivalent resistance being equivalent to resistance RB135 reduces, thus output voltage Vout2 is reduced.When PWM_12V signal exports as 0V, the output voltage values of the second power supply output OUT2 is maximum, because when PWM_12V signal is 0V, be equivalent to control signal input Cont ground connection, resistance RB150 is in parallel with resistance RB134, and according to Output Voltage Formula, the equivalent resistance of resistance RB134 diminishes, the voltage of the reference input R of pressurizer UB102 diminishes, and therefore the output voltage of the second power supply output OUT2 raises.

Visible, the control signal (voltage signal of 0V ~ 3.3V as escribed above or PWM ripple) inputted by the control signal input Cont of linear regulation feedback adjusting circuit 1012, the output voltage of the second power supply output OUT2 can be made to carry out regulating (Vout2_max=12.5V between actual common voltage scope 11.5V ~ 12.5V, Vout2_min=11.5V), thus realize fine setting; In like manner, under the effect of multiple-channel output transformer TB101, the output voltage of the first power supply output OUT1 also will realize synchronous automatic adaptation and regulate.

In embody rule occasion, under product ideal case (power supply circuits export and reduce), the control signal inputted to the control signal input Cont of feedback adjusting circuit 1012 by linear regulation external control chip is high level (as 3.3V), thus the voltage that second of power supply circuits 1011 the power supply output OUT2 can be made to export is minimum output voltage, can reduce the stand-by power consumption of TV SKD.

In addition, described LED string to be powered is in series by multiple LED, along with the increasing of quantity of LED string to be powered, after multiple LED strip connection, required supply power voltage constantly increases, therefore, require that the output voltage of the first power supply output OUT1 can respond the number change of LED adaptively, automatically regulate its output voltage values.

Referring to Fig. 5 ~ 6, be two kinds of rear end provided by the invention linear constant current circuit can the circuit theory diagrams of implementation.

Described rear end linear constant current circuit 103 comprises and compares Circuit tuning 1031 and constant-current control circuit 1032; The described Circuit tuning 1031 that compares comprises operational amplifier UB1A, and the reverse input end of described operational amplifier UB1A is connected with described reference signal input PWM_REF by a resistance RB12; The positive input of described operational amplifier UB1A is connected with current feedback circuit, and the output of described operational amplifier UB1A passes through the control end of a control circuit model calling switching tube QB1.Particularly, as shown in Figure 5,6, this current feedback circuit comprises the constant current composed in parallel by resistance RB6, resistance RB7, resistance RB8 and resistance RB9 and detects resistance, also comprises resistance RB5 and electric capacity CB5.Wherein, one end that the constant current be made up of resistance RB6, resistance RB7, resistance RB8 and resistance RB9 detects resistance is connected on one end of resistance RB5, other end ground connection; The other end of resistance RB5 is connected on the normal phase input end of described operational amplifier UB1A.One end ground connection of described electric capacity CB5, the other end is connected on the normal phase input end of described operational amplifier UB1A.The circuit that wherein resistance RB5 and electric capacity CB5 forms can carry out filtering to the signal of the positive input being input to operational amplifier UB1A.

Preferably, the positive input of described operational amplifier UB1A is also connected with a clamp diode DB1, to protect described normal work of comparing Circuit tuning 1031.

In the rear in linear constant-current circuit 103, described constant-current control circuit 1032 comprises control circuit module and switching tube QB1.Switching tube QB1 can be triode or MOS (Metal-Oxid-Semiconductor, metal-oxide semiconductor (MOS)) field-effect transistor, is called for short metal-oxide-semiconductor or field-effect transistor.Wherein, the conducting of switching tube QB1, cut-off or conducting level state are associated with the physical characteristic of himself.Such as, when switching tube QB1 is triode, according to the volt-ampere characteristic of triode, there is saturation region, amplification region and cut-off region, respectively from the voltage signal between collector electrode, different impacts is produced to the emitter of triode, as when triode operation is in saturation region, between the emitter of triode and collector electrode, be equivalent to short circuit (conducting state).

Described rear end linear constant current circuit 103 by reference to signal input part PWM_REF, to access constant current reference voltage V _rEF, and according to described constant current reference voltage V _rEFsize control the conducting of described switching tube QB1, cut-off or conducting degree, thus the connection of rear end linear constant current circuit 103 described in ON/OFF and described LED string to be powered

In the present embodiment, as shown in Figure 5, when described switching tube QB1 is triode, described constant-current control circuit 1032 is connected with one end (LED-) of described LED string to be powered by the collector electrode of described triode; The emitter of described triode is connected with the anode of described clamp diode DB1, and the base stage of described triode is connected by the output of described control circuit module with described operational amplifier UB1A; As shown in Figure 6, when described switching tube QB1 is field-effect transistor, described constant-current control circuit 1032 is connected with one end (LED-) of described LED string to be powered by the drain electrode of described field-effect transistor; The source electrode of described field-effect transistor is connected with the anode of described clamp diode DB1, and the grid of described field-effect transistor is by the output of described control circuit module and described operational amplifier UB1A.

During concrete enforcement, the minus earth of clamp diode DB1, anode is connected to the positive input of operational amplifier UB1A by resistance RB5.After rear end linear constant current circuit 103 starts, through the adjustment of operational amplifier UB1A, its positive input institute connects the constant current detection magnitude of voltage got of resistance and it oppositely inputs the constant current reference voltage V accessed _rEFequal, then as constant current reference voltage V _rEFduring turn-on voltage (about 0.7V) higher than clamp diode DB1; clamp diode DB1 will conducting ground connection; namely the magnitude of voltage that the constant current that composed in parallel by resistance RB6, resistance RB7, resistance RB8 and resistance RB9 detects resistance two ends limit by clamp diode DB1; therefore, clamp diode DB1 serves certain protective effect.

And, because the emitter (switching tube QB1 is triode) of switching tube QB1 or source electrode (switching tube QB1 is metal-oxide-semiconductor) are connected with the anode of clamp diode DB1, the constant current value of the switching tube QB1 that therefore circulates can pass through following formulae discovery:

As constant current reference voltage V _rEFduring turn-on voltage higher than clamp diode DB1, the constant current signal of circulation switching tube QB1 is I _{constant current}turn-on voltage/the constant current of=DB1 detects the resistance of resistance; As constant current reference voltage V _rEFduring turn-on voltage lower than clamp diode DB1, the constant current signal of circulation switching tube QB1 is I _{constant current}=constant current reference voltage V _rEF/ constant current detects the resistance of resistance.Usually, the turn-on voltage of clamp diode DB1 is 0.7V, and the resistance of constant current detection resistance is the equivalent resistance after resistance RB6, resistance RB7, resistance RB8 and resistance RB9 parallel connection.

In the present embodiment, first power supply output is connected to the positive pole LED+ of LED string, by the current constant control of switching tube QB1, be connected in series constant current again and detect resistance (parallel resistance of resistance RB6, resistance RB7, resistance RB8 and resistance RB9) to ground, the size of current of LED string is converted to voltage signal and is linked into operational amplifier UB1A and constant current reference voltage V by constant current detection resistance _rEF(controlled by outside master chip, or access fixed voltage, if the constant current value I that fixed voltage then exports _{constant current}be then fixed value, the adjustment of constant current size can not be carried out) compare and amplify, thus control switch pipe QB1 adjusts the constant current hold of LED string.

During concrete enforcement, LED string generally can be connected plurality of LEDs lamp, and wherein the operating voltage of single LEDs is generally 2.8V ~ 3.4V, and the operating voltage after the series connection of plurality of LEDs lamp is by corresponding increase.For switching tube QB1 for metal-oxide-semiconductor, the voltage V between the drain electrode of switching tube QB1 and source electrode _dS=V _oUT1-LED string operating voltage-constant current reference voltage V _rEF.Therefore, after rear end linear constant current circuit 103 enters operating state, the voltage V between the drain electrode of switching tube QB1 and source electrode _dSthe impact of the operating voltage size of LED string will be subject to, the impact of the cross modulation (general range is 7%) of multiple-channel output transformer TB101 may be subject in addition.

In the prior art, along with the change of LED crosstalk pressure, the drain-source voltage V of switching tube QB1 _dSvoltage also synchronously changes, this part power (V of switching tube QB1 _dS* constant current value I _{constant current}) form that will convert heat to comes out, V _dSvoltage is larger, and the power consumption of switching tube QB1 is larger, and temperature is higher.Therefore the switching tube QB1 that power consumption is excessive can reduce power-efficient and causes switching tube QB1 overheated and easily damage.In order to reduce the temperature of switching tube QB1, multiple metal-oxide-semiconductor or triode parallel connection can be adopted to use as switching tube QB1, but this technical scheme result in the increase of cost.

See Fig. 2, Fig. 7 ~ Fig. 8, the present embodiment effectively can solve the power problems of above-described switching tube QB1.Particularly, by drawing a road voltage acquisition output terminals A DC with described LED string junction P to be powered by voltage detecting circuit 104 at described constant-current control circuit 1032, to detect the change in voltage of LED string to be powered in real time, for the pressure drop between voltage acquisition output terminals A DC and reference signal input PWM_REF sets a threshold value, or the output voltage for voltage acquisition output terminals A DC sets a steady state value (the voltage V of reference signal input PWM_REF _rEFgeneral less), pressure drop between voltage acquisition output terminals A DC and reference signal input PWM_REF is greater than described threshold value, or when the output voltage of voltage acquisition output terminals A DC is greater than described steady state value, by the control signal PWM_12V of the control signal input Cont in adjustment front end power circuit 101, control optocoupler PCB101 and the situation of change (i.e. the change in voltage situation of the first power supply output OUT1) of the operating voltage of LED string is fed back to pwm chip UB101, pwm chip UB101 control switch pipe QB101 changes duty ratio, thus the magnitude of voltage making the magnitude of voltage of voltage acquisition output terminals A DC deduct reference signal input PWM_REF equals or close to the described threshold value (or the magnitude of voltage of voltage acquisition output terminals A DC equals or close to described steady state value) preset, therefore, the present embodiment can by the control signal PWM_12V of control signal input Cont, stop voltage gathers the pressure drop between output terminals A DC and reference signal input PWM_REF, thus reduce the drain-source voltage V of switching tube QB1 _dSbe subject to the impact of the change in voltage of LED string, reduce the power consumption of switching tube QB1 and ensure that power-efficient.

This voltage detecting circuit 104 comprises diode DB2 and pull-up resistor RB18, the negative electrode of described diode DB2 is connected to the negative electrode LED-of described LED string, the anode of diode DB2 is connected to one end of pull-up resistor RB18, the other end access high level (being preferably 3.3V) of pull-up resistor RB18; During concrete enforcement, the constant-current control circuit 1032 that high level VCC can be controlled by the control end identical with switching tube QB1 provides.

The anode of described diode DB2 connects described voltage acquisition output terminals A DC.The anode of described diode DB2 also connects described voltage acquisition output terminals A DC by resistance RB16.Now, the output voltage of voltage acquisition output terminals A DC is: V _aDC=V _a* RB17/ (RB16+RB17).When described LED string is opened, diode DB2 conducting, described voltage detecting circuit 104 detects the operating voltage of described LED string by diode DB2, thus controls the output voltage that described feedback adjusting circuit 1012 adjusts described first power supply output OUT1, the second power supply output OUT2; When described LED string is closed, diode DB2 oppositely ends, and turns off the electric current flowing through described LED string.

Draw a road output terminals A DC_12V at constant-current control circuit 1032 with the junction P of LED string negative electrode to be connected with diode DB2 negative electrode, when described LED string is opened, diode DB2 conducting, detect that the operating voltage of described LED string flows through resistance RB16 and transfers to external control devices or chip by diode DB2, thus adjust the output voltage of described first power supply output OUT1, the second power supply output OUT2 by controlling described feedback circuit; When described LED string is closed, when namely switching tube QB1 ends, diode DB2 oppositely ends, and turns off the electric current flowing through described LED string.

Particularly, the main operational principle of the backlight control circuit of low-power consumption that the present embodiment provides is:

When opening backlight of television power supply, switching tube QB1 conducting enters operating state, be limited in collector electrode (when switching tube QB1 is triode) by with the contact voltage of the P point connect of LED or drain on the magnitude of voltage (being usually less than 3.3V) of (when switching tube QB1 is field-effect transistor), meanwhile, the access of high level VCC makes the voltage V of the tie point of diode DB2 and resistance RB18 _ahigher than the voltage of P point, therefore, diode DB2 conducting, circuit carries out work by resistance RB18, diode DB2 and switching tube QB1 loop.Now, the voltage V of the tie point of diode DB2 and resistance RB18 _a=V _dB2+ V _qB1; Now, the output voltage of voltage detecting output terminals A DC is: V _aDC=V _a* RB17/ (RB16+RB17).When closing television machine backlight electric power, switching tube QB1 enters cut-off state, LED string two ends keep constant voltage and there is the high level much larger than 3.3V at LED-end, therefore diode DB2 oppositely ends, open circuit is equivalent between LED string and voltage detecting circuit 104, namely LED string will pass through without weak current, thus can not produce glimmer phenomenon.

Preferably, the described voltage detecting circuit 104 that the present embodiment provides also comprises a filter circuit of pressure-stabilizing 1042; Described filter circuit of pressure-stabilizing 1042 is connected between described voltage acquisition output terminals A DC and ground.

Described filter circuit of pressure-stabilizing 1042 comprises voltage stabilizing didoe D1, electric capacity CB7 and resistance RB17; And one end of the negative electrode of voltage stabilizing didoe D1, electric capacity CB7 and one end of resistance RB17 are connected on described voltage acquisition output terminals A DC jointly; The other end common ground of the anode of voltage stabilizing didoe D1, the other end of electric capacity CB7 and resistance RB17.Wherein, the Main Function of voltage stabilizing didoe D1 prevents voltage detecting circuit 104 from causing the output voltage of port ADC excessive at operation irregularity or when switching tube QB1 turns off because high level VCC voltage is greater than 3.3V, thus the situation of burning the device that voltage acquisition output terminals A DC connects occurs.

This voltage detecting circuit 104 comprises diode DB2 and pull-up resistor RB18, the negative electrode of described diode DB2 is connected to the negative electrode LED-of described LED string, the anode of diode DB2 is connected to one end of pull-up resistor RB18, the other end access high level (being preferably 3.3V) of pull-up resistor RB18; The anode of described diode DB2 also connects described voltage acquisition output terminals A DC by diode DB3.The anode of described diode DB3 is connected with the anode of diode DB2; The negative electrode of described diode DB3 is as described voltage acquisition output terminals A DC, and now, the output voltage of voltage acquisition output terminals A DC is: V _aDC=V _a-V _dB3.

The output voltage V of voltage acquisition output terminals A DC _aDCexternal control devices will be transferred to and carry out Treatment Analysis, to control the operating state of front end power circuit 101 according to analysis result, thus control the output voltage of the first power supply output OUT1 and second power supply output OUT2.

In the present embodiment, the main operational principle of the voltage stabilizing backlight control circuit of the low-power consumption that the present embodiment provides is identical with the basic functional principle of Fig. 7 illustrated embodiment, mainly comprise: when opening backlight of television power supply, switching tube QB1 conducting enters operating state, the access of high level VCC makes diode DB2 conducting, circuit carries out work by resistance RB18, diode DB2 and switching tube QB1 loop, the voltage V of the tie point of diode DB2 and resistance RB18 _a=V _dB2+ V _qB1; Meanwhile, diode DB3 conducting, by voltage V _atransfer to voltage detecting output terminals A DC, now, the output voltage of voltage detecting output terminals A DC is: V _aDC=V _a-V _dB3.When closing television machine backlight electric power, switching tube QB1 enters cut-off state, LED string two ends keep constant voltage thus to there is the high level much larger than 3.3V at LED-end, therefore diode DB2 oppositely ends, open circuit is equivalent between LED string and voltage detecting circuit 104, namely LED string will pass through without weak current, thus can not produce glimmer phenomenon.

The constant current of a kind of low-power consumption that the present embodiment provides and backlight control circuit, be provided with front end power circuit, rear end linear constant current circuit and voltage detecting circuit, front end power circuit is utilized to regulate the supply power voltage of two-way output, and feedback circuit is set up in the power circuit of front end, and be provided with control signal input in a feedback circuit, to realize controlling the front end power circuit voltage at the first power supply output and the second power supply output, and the change by setting up rear end linear constant current circuit automatically to adapt to the LED backlight quantity of connecting, the magnitude of voltage of described control signal input can be adjusted according to the magnitude of voltage after LED backlight series connection, thus control described first power supply output by front end power circuit and feedback circuit thereof, the output voltage of the second power supply output, and the first power supply output is connected to LED backlight and powers, achieve the voltage automation adapted with LED backlight quantity to regulate, reduce the power consumption of circuit switch element, and ensure that the stability of the supply power voltage of motherboard circuit.

The present embodiment has set up voltage detecting circuit, contacted by diode DB2 and backlight LED light and connect, when LED string is opened, diode DB2 conducting, voltage detecting circuit detects the operating voltage of LED string, thus can control the output voltage of the described first power supply output of described feedback circuit adjustment, the second power supply output; When described LED string is closed, diode DB2 oppositely ends, and turn off the electric current flowing through described LED string completely, therefore the present invention can when backlight open, the operating voltage of normal acquisition LED string; When on-off switching tube QB1 is to close LED backlight, LED string two ends are equivalent to open circuit, and LED, without glimmer phenomenon, avoids the useful life of unnecessary power consumption penalty and raising backlight LED.

Referring to Fig. 9, it is the structural representation of the constant current of low-power consumption provided by the invention and the another embodiment of backlight control circuit.

The distinctive points of the present embodiment and previously described embodiment is, on the basis of previously described embodiment, further, the constant current of the low-power consumption that the present embodiment provides and backlight control circuit also comprise a control master chip 105.Wherein, front end power circuit 101 is identical with previously described embodiment with operation principle with the essential structure of voltage detecting circuit 104 with rear end linear constant current circuit 103, does not repeat them here.

Described control master chip 105 is connected respectively with described control signal input Cont, described reference signal input PWM_REF and described voltage acquisition output terminals A DC;

Described control master chip 105 is according to the change in voltage of described voltage acquisition output terminals A DC, adjust the output to the signal magnitude of described control signal input Cont, to control the first power supply output OUT1 of described front end power circuit 101, the output voltage values of the second power supply output OUT2; And input described constant current reference voltage V by described reference signal input PWM_REF to described rear end linear constant current circuit 103 _rEF.

Particularly, when described control master chip 105 detects that the voltage difference of described voltage acquisition output terminals A DC and described reference signal input PWM_REF is greater than default threshold value, the voltage signal duty ratio exporting described control signal input Cont to reduces by described control master chip 105.During concrete enforcement, described control master chip 105 is built-in with analog to digital converter, is converted to digital signal for the voltage signal accessed by described control master chip 105.Gather the voltage signal that obtains first after the conversion of analog to digital converter from voltage acquisition output terminals A DC, obtain corresponding digital signal, then by controlling the process of other processing unit in master chip 105.Because too high input voltage value can affect the normal work of analog to digital converter, and the magnitude of voltage of P point easily makes the resistance between former connection mode number converter of the prior art produce low current signal when closing LED string, thus LED backlight is made to produce glimmer phenomenon.Because the present embodiment is provided with voltage detecting circuit 104, when turning off backlight electric power, can move back in LED string by controlling diode DB2 thus effectively cutting off the current signal of voltage detecting circuit 104, avoiding the generation of " glimmer phenomenon ".

The present embodiment processes owing to have employed the signal of same control master chip to control signal input Cont, described reference signal input PWM_REF and described voltage acquisition output terminals A DC tri-terminals, therefore on the basis of previously described effective effect, further can in real time according to the signal intensity of reference signal input PWM_REF and voltage acquisition output terminals A DC, and send corresponding control signal to control signal input Cont, therefore can reach the beneficial effect rapidly to the response for changing of LED string operating voltage.

The present invention also discloses a kind of television set, comprising: TV SKD, backlight LED light string, and the constant current of low-power consumption as shown in Fig. 2 or Fig. 9 and backlight control circuit.

The constant current of described low-power consumption and backlight control circuit are connected respectively with described TV SKD and described backlight LED light string, for when turning on the power supply of described television set, according to the operating voltage of described backlight LED light string, Automatic adjusument supplies the voltage signal of described TV SKD, described backlight LED light string; When closing the power supply of described television set, turn off the electric current flowing through described backlight LED light string.Wherein, the constant current of low-power consumption and the basic comprising of backlight control circuit, do not repeat them here with described identical above with operation principle.

The above is the preferred embodiment of the present invention; it should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention; can also make some improvements and modifications, these improvements and modifications are also considered as protection scope of the present invention.

Claims

1. the constant current of low-power consumption and a backlight control circuit, is characterized in that, comprising: front end power circuit and rear end linear constant current circuit;

2. the constant current of low-power consumption as claimed in claim 1 and backlight control circuit, it is characterized in that, the anode of described diode also connects described voltage acquisition output by a resistance.

3. the constant current of low-power consumption as claimed in claim 1 and backlight control circuit, it is characterized in that, the anode of described diode also connects described voltage acquisition output by another diode; The anode of another diode described is connected with the anode of described diode; The negative electrode of another diode described is as described voltage acquisition output.

4. the constant current of the low-power consumption as described in any one of claims 1 to 3 and backlight control circuit, is characterized in that, described voltage detecting circuit also comprises a filter circuit of pressure-stabilizing; Described filter circuit of pressure-stabilizing is connected between described voltage acquisition output and ground;

5. the constant current of low-power consumption as claimed in claim 1 and backlight control circuit, it is characterized in that, described rear end linear constant current circuit comprises and compares Circuit tuning and constant-current control circuit; Described constant-current control circuit at least comprises a switching tube and control circuit module; The described Circuit tuning that compares comprises operational amplifier, the reverse input end of described operational amplifier connects described reference signal input, positive input connection detects grounding through resistance by constant current, and the output of described operational amplifier passes through the control end of switching tube described in described control circuit model calling; The input of described switching tube is connected with the negative electrode of described LED string to be powered, and the output of described switching tube detects grounding through resistance by described constant current.

6. the constant current of low-power consumption as claimed in claim 5 and backlight control circuit, is characterized in that:

When described switching tube is triode, the collector electrode of described triode is connected with one end of described LED string to be powered, and emitter detects grounding through resistance by described constant current, and base stage is connected with the output of described operational amplifier by described control circuit module;

When described switching tube is field-effect transistor, the drain electrode of described field-effect transistor is connected with one end of described LED string to be powered, source electrode detects grounding through resistance by described constant current, and grid is connected with the output of described operational amplifier by described control circuit module.

7. the constant current of low-power consumption as claimed in claim 5 and backlight control circuit, is characterized in that: described constant current detect resistance primarily of resistance (RB6), resistance (RB7), resistance (RB8) is in parallel with resistance (RB9) forms.

8. the constant current of low-power consumption as claimed in claim 5 and backlight control circuit, it is characterized in that: the normal phase input end of described operational amplifier detects resistance by resistance (RB5) with described constant current and is connected, the output of described switching tube is connected to the junction that described resistance (RB5) and described constant current detect resistance.

9. the constant current of low-power consumption as claimed in claim 5 and backlight control circuit, is characterized in that: the normal phase input end of described operational amplifier is also by electric capacity (CB5) ground connection.

10. the constant current of low-power consumption as claimed in claim 5 and backlight control circuit, is characterized in that: the described Circuit tuning that compares also comprises a clamp diode;

11. constant current of low-power consumption and backlight control circuits as claimed in claim 1, it is characterized in that: only when the voltage of this junction that described voltage acquisition output collects is more than or equal to default threshold value, just adjust the magnitude of voltage of described control signal input, thus adjust the output voltage of described first power supply output, the second power supply output further, be less than default threshold value to make the voltage of this junction.

The constant current of 12. low-power consumption as claimed in claim 1 and backlight control circuit, is characterized in that, also comprise a control master chip;

13. constant current of low-power consumption and backlight control circuits as claimed in claim 12, it is characterized in that, when described control master chip detects that the voltage difference of described voltage acquisition output and described reference signal input is greater than default threshold value, the voltage signal duty ratio exporting described control signal input to reduces by described control master chip.

14. constant current of low-power consumption and backlight control circuits as claimed in claim 13, it is characterized in that, described control master chip comprises analog to digital converter, for the voltage signal of described control master chip access is converted to digital signal.

The constant current of 15. low-power consumption as described in any one of claim 1 ~ 14 and backlight control circuit, it is characterized in that, described power supply circuits comprise power supply input circuit, switching power circuit, multiple-channel output transformer, LED power output circuit and main board power supply output circuit;

16. constant current of low-power consumption and backlight control circuits as claimed in claim 1, it is characterized in that, described feedback adjusting circuit comprises opto-coupled feedback unit, voltage stabilizing reference cell, voltage sampling unit and voltage-adjusting unit;

17. constant current of low-power consumption and backlight control circuits as claimed in claim 16, it is characterized in that, described voltage stabilizing feedback circuit comprises the first electric capacity (CB109) and the 3rd resistance (RB133);

18. constant current of low-power consumption and backlight control circuits as claimed in claim 16, it is characterized in that, described voltage stabilizing feedback circuit comprises the second electric capacity (CB110);

19. constant current of low-power consumption and backlight control circuits as claimed in claim 16, it is characterized in that, described voltage stabilizing feedback circuit comprises the first electric capacity (CB109), the 3rd resistance (RB133) and the second electric capacity (CB110);

20. constant current of low-power consumption and backlight control circuits as claimed in claim 1, it is characterized in that, the output voltage corresponding relation of the magnitude of voltage of described control signal input and the power supply output of described power supply circuits is: during every stepping 1% duty ratio of the magnitude of voltage of described control signal input, the output voltage change 0.01V of described first power supply output, and the output voltage change 0.1V of described second power supply output.

21. constant current of low-power consumption and backlight control circuits as claimed in claim 13, it is characterized in that, the input of described control signal input for range of voltage values be voltage signal or the PWM ripple of 0V ~ 3.3V, the output voltage correspondence of described first power supply output is adjustable as 11.5V ~ 12.5V, and the output voltage automatic adaptation of described second power supply output.

22. 1 kinds of television sets, comprising: TV SKD, backlight LED light string, and the constant current of low-power consumption as described in any one of claim 1 ~ 21 and backlight control circuit;