WO2006005241A1

WO2006005241A1 - A micropower supply converter capable of soft start

Info

Publication number: WO2006005241A1
Application number: PCT/CN2005/000480
Authority: WO
Inventors: Xiangyang Yin
Original assignee: Mornsun Guangzhou Science & Technology Ltd.
Priority date: 2004-07-14
Filing date: 2005-04-11
Publication date: 2006-01-19

Abstract

A micropower supply converter capable of soft start comprises an input filter capacitor, a drive transformer, a transistor, a coupling output transformer and a rectification and output circuit, in which a soft start circuit is provided between the center tap of the secondary winding of the drive transformer and the input of the supply voltage.

Description

Soft startable micro power converter

Technical field

The present invention relates to a micropower DC/DC power converter, and more particularly to a soft start DC power DC/DC power converter.

Background technique

The existing commonly used micro-power DC/DC power converter (shown in FIG. 1) includes an input filter capacitor, a drive transformer, a transistor, a coupled-output transformer, and a rectified output circuit. The working principle is: when the access voltage Vs is filtered After capacitor C, the forward bias is provided to transistor TR1, TR2 by driving transformer T2. Since the characteristics of the two tubes are not exactly the same, one of them will be turned on first. Assume that TR2 is turned on first, generating collector current 2, and the voltage on winding Nb2 is up-down and down-down. According to the same name, each winding will have the polarity shown in Figure 1. At this time, the winding Nb2 acts to increase the base current of the transistor TR2, and the winding Nb1 acts to reduce the base current of TR1. According to this cycle, the transistor TR2 is quickly turned on and the transistor TR1 is completely turned off. This process is repeated in this way to form an oscillation, realizing the self-oscillation frequency and the driving function. The energy is then coupled to the output transformer Tl, the diode D2 of the rectified output circuit, and the rectified output of D1 to realize energy conversion, and complete the entire working process of the DC/DC power converter. The automatic oscillation frequency is determined by the core characteristics of the transformer T2 and the voltage between the base and emitter of the transistor. The advantage of this circuit is that the circuit structure is simple and requires fewer components. However, the bias voltage is supplied to the transistors TR1 and TR2 through the winding of the transformer T2, resulting in a large starting current and a slow starting speed. And the magnitude of the driving voltage is proportional to the source voltage. When designing, if the input/output is fluctuating in the worst case (ie, the source voltage Vs is the smallest, the load current is the largest), it can provide enough basic driving current ( That is, when the base resistor R1 is provided, sufficient voltage can be supplied, so that the switch still enters full saturation state. Then, when Vs is maximum and the converter load current is minimum, the switch is driven by a large overvoltage, and the tube is easily broken down. .

Summary of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide a micropower DC/DC power converter that can improve circuit starting characteristics, increase starting speed, and prevent breakdown of the life of the tube and the components.

The object of the present invention can be achieved by the following techniques: including input filter capacitor C, 3⁄4 dynamic change The voltage regulator T2, the transistors TR1, TR2, the coupled output transformer T1 and the rectified output circuit are characterized in that: a soft start circuit is provided between the intermediate winding of the secondary winding of the driving transformer and the input terminal of the source voltage.

The soft start circuit is composed of a resistor R1 and a capacitor C1. The resistor R1 and the capacitor C1 are connected in series. The series branch of the resistor R1 and the capacitor C1 is connected between the source voltage input terminal and the ground, and the series terminal of the resistor R1 and the capacitor C1. Connected to the center tap of the secondary winding of the drive transformer.

The soft start circuit is composed of a resistor R1, a resistor R2 and a capacitor C1. The resistor R1 and the resistor R2 are connected in series, and the series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground, and the resistor R1 and the resistor R2 are connected. The series end is connected to the center tap of the secondary winding of the drive transformer, which is also connected to ground via capacitor C1.

The soft start circuit is composed of a resistor R1, a resistor R2 and an inductor L1. The resistor R1, the resistor R2 and the inductor L1 are sequentially connected in series. The series branch is connected between the source voltage input terminal and the ground, and the resistor R1 and the resistor R2 are connected. The series end is connected to the center tap of the secondary winding of the drive transformer.

The soft start circuit is composed of resistors R1, R2, R3, R4, capacitor CI and capacitor C3. The resistor R1 and the resistor R2 are connected in series, and the series branch of the resistor R1 and the resistor R2 is connected to the source voltage input terminal and the ground. The series end of the resistor R1 and the resistor R2 is connected to the center tap of the secondary winding of the driving transformer, and the resistor R3 is connected between the connecting end of the secondary winding of the driving transformer and the base of the transistor TR1, and the capacitor C 1 is connected at one end. The other end of the transistor TR1 is grounded; the resistor R4 is connected between the other connection terminal of the secondary winding of the driving transformer and the base of the transistor TR2, and the capacitor C3 is terminated with the base of the transistor TR2. The other end is grounded.

The soft start circuit is composed of a resistor R1 and a capacitor C1. The resistor R1 and the capacitor C1 are connected in parallel. The parallel branch of the resistor R1 and the capacitor C1 is connected between the source voltage input terminal and the intermediate tap of the secondary winding of the drive transformer.

The soft start circuit is composed of a resistor R1, a resistor R2 and a capacitor C1. The resistor R1 and the resistor R2 are connected in series, and the series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground, and the resistor R1 and the resistor R2 are connected. The series terminal is connected to the center tap of the secondary winding of the drive transformer, and the series terminal is also connected to the source voltage input via a capacitor C1. The soft start circuit is composed of a resistor R1, a resistor R2 and a Zener diode D1. The resistor R1 and the resistor R2 are connected in series, and the series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground, the resistor R1 and The series end of the resistor R2 is connected to the center tap of the secondary winding of the drive transformer, the series terminal is also connected to the cathode of the Zener diode D1, and the anode of the Zener diode D1 is grounded.

The soft start circuit is composed of a capacitor C1 and a Zener diode D1. The capacitor C1 and the Zener diode D1 are connected in parallel. The parallel branch of the capacitor C1 and the Zener diode D1 are connected to the source voltage input terminal and the secondary winding of the drive transformer. Between the intermediate taps, wherein the cathode of the Zener diode D1 is connected to the source voltage input terminal, and the anode of the Zener diode D1 is connected to the middle tap of the secondary winding of the drive transformer.

The soft start circuit is a Zener diode D1 connected between the source voltage input end and the middle tap of the secondary winding of the drive transformer, wherein the cathode of the Zener diode PI is connected to the source voltage input terminal, and the anode connection of the Zener diode D1 Drive the center tap of the secondary winding of the transformer.

The soft start circuit is a resistor R1 connected between the source voltage input terminal and the intermediate tap of the secondary winding of the drive transformer.

Since the soft start circuit is provided in the present invention, after the voltage is applied, the two transistors TR1 and TR2 are not turned on immediately. By selecting the component parameters in the soft start circuit, the parameters of the resistor R1 and the capacitor C1 can be selected. It not only conveniently controls the transistor to conduct after the input current and voltage are stable, but also accelerates the on-time of the transistor at the start-up instant, thereby greatly improving the startup characteristics of the circuit. At the same time, this circuit structure can ensure that the voltage applied to the bases of transistors TR1 and TR2 does not exceed its limit value, which improves the service life of components and better ensures the stability of product quality. In addition, there is no requirement for the input voltage. This circuit can work normally when the input voltage is high. The resistor in the soft-start circuit provides the soft-start voltage to the transistor and optimizes the static characteristics of the transistor.

DRAWINGS

1 is a circuit schematic diagram of a conventional micro power DC/DC power converter;

2 is a schematic circuit diagram of a first embodiment of the present invention;

3 is a circuit schematic diagram of Embodiment 2 of the present invention;

Figure 4 is a schematic diagram of the circuit of the third embodiment of the present invention - Figure 5 3⁄4 does not explain the circuit schematic of the purchase of four;

6 is a circuit schematic diagram of Embodiment 5 of the present invention;

7 is a circuit schematic diagram of Embodiment 6 of the present invention;

Figure 8 is a circuit schematic diagram of Embodiment 7 of the present invention;

9 is a circuit schematic diagram of Embodiment 8 of the present invention;

Figure 10 is a circuit schematic diagram of Embodiment 9 of the present invention;

Figure 11 is a circuit schematic diagram of Embodiment 10 of the present invention;

Figure 12 is a circuit schematic diagram of Embodiment 11 of the present invention.

detailed description

As shown in FIG. 2, the input filter capacitor (:, the drive transformer T2, the transistor TR1, the TR2, the output transformer T1, and the rectified output circuit are connected, the filter capacitor C is connected between the voltage input terminal and the ground, and the source voltage input terminal is connected to the output transformer. The middle tap of the T1 primary winding, the primary winding of the driving transformer T2 is connected to the collectors of the transistors TR1 and TR2, the secondary winding of the driving transformer T2 is connected to the bases of the transistors TR1 and TR2, and the emitters of the transistors TR1 and TR2 are grounded. The collectors of the transistors TR1 and TR2 are connected to the two ends of the primary winding of the output transformer T1, and the rectifier windings D1 and D2 are respectively connected to the two ends of the secondary winding of the output transformer T1, and the intermediate tap of the secondary winding of the output transformer T1 is the output voltage reference terminal, and is rectified. The cathodes of the diodes D1 and D2 are connected to the output voltage terminal.

A soft start circuit is provided between the secondary winding of the drive transformer and the source voltage input terminal. The soft start circuit is composed of a resistor R1 and a capacitor C1. The resistor R1 and the capacitor C1 are connected in series. The series branch of the resistor R1 and the capacitor C1 is connected between the source voltage input terminal and the ground, and the series terminal and the resistor R1 and the capacitor C1 are connected. The middle tap of the secondary winding of the transformer is connected.

When the voltage is applied, it is applied to the capacitor via resistor R1. For a short period of time just after the voltage is applied, since the C1 is in a charging state, the two transistors TR1, TR2 are not turned on immediately. Only when C1 is charged to a certain voltage, it is possible to provide a forward bias voltage through the secondary winding P 2 of the drive transformer to turn the transistor on. The length of this time can be controlled by the selection of the size of the C1 parameter. The other input voltage is applied directly to the collector of the two transistors through the primary winding of the output transformer T1. Provides a collector voltage that works properly. When the circuit is working normally, the secondary winding P3 of the output transformer T1 is coupled with the primary winding P1 to gradually output energy, thereby completing the function of the entire converter. By selecting the parameters of the resistor R1 and the capacitor C1, it is convenient to control the transistor to be turned on after the input current and voltage are stabilized, and the starting current is small, so that the starting characteristics of the circuit can be greatly improved. At the same time, it is also ensured that the voltage applied to the bases of the transistors TR1 and TR2 does not exceed its limit value, which provides a good protection for the components. In addition, the resistor in the soft-start circuit provides a DC bias voltage to the transistor, optimizing the static characteristics of the transistor.

As shown in FIG. 3, the second embodiment differs from the first embodiment in a soft start circuit. The soft start circuit is composed of a resistor R1, a resistor R2 and a capacitor C1. The resistor R1 and the resistor R2 are connected in series. The series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ,, and the resistor R1 and the resistor R2 are connected in series. The terminal is connected to the center tap of the secondary winding of the drive transformer, and the series terminal is also connected to the ground via a capacitor C1. Using the voltage divider of resistors R1 and R2, the voltage on resistor R2 is set to determine the voltage applied to capacitor C1. By selecting the size of resistor R1, R2 and capacitor CI, the transistor can be conveniently controlled at the input. The current and voltage are stabilized and turned on to improve the starting characteristics. As shown in FIG. 4, the difference between the third embodiment and the second embodiment is that a resistor R3 is further disposed in the soft start circuit, and the resistor R3 is connected to the series end of the resistor R1 and the resistor R2 and the middle tap of the secondary winding of the driving transformer. between. The third embodiment has the same principle as the second embodiment and can achieve the same soft start effect.

As shown in FIG. 5, the fourth embodiment differs from the first embodiment in a soft start circuit. The soft start circuit is composed of a resistor R1, a resistor R2 and an inductor L1. The resistor R1, the resistor R2 and the inductor L1 are sequentially connected in series. The series branch is connected between the source voltage input terminal and the ground, and the series terminal of the resistor R1 and the resistor R2. Connected to the center tap of the secondary winding of the drive transformer. When the input voltage first charges the inductor L1, when the current on the resistor R1 reaches a certain value after charging for a certain period of time, the transistor is turned on, so that the soft start effect can be achieved, thereby protecting the transistors TR1 and TR2.

As shown in FIG. 6, the fifth embodiment differs from the first embodiment in a soft start circuit. The soft start circuit is composed of resistors R1, R2, R3, R4, capacitor CI and capacitor C3. The resistor R1 and the resistor R2 are connected in series, and the series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground. Resistor R1 and electricity The series end of the resistor R2 is connected to the center tap of the secondary winding of the driving transformer, the resistor R3 is connected between the connecting end of the secondary winding of the driving transformer and the base of the transistor TR1, and the end of the capacitor C1 is connected to the base of the transistor TR1. The other end is grounded; the resistor R4 is connected between the other connection terminal of the secondary winding of the driving transformer and the base of the transistor TR2, and the capacitor C3 is terminated to the base of the transistor TR2, and the other end thereof is grounded.

After the voltage is divided by the resistors R1 and R2, the voltage is applied to the winding and the resistor R3, and is divided into a transistor TR1 branch and a capacitor C1 branch. At the instant of startup, transistor TR1 is in the off state, and the voltage first charges capacitor C1. When charged to a certain voltage, transistor TR1 can be supplied with a forward bias voltage to turn it on. Therefore, as long as the parameters of the resistors R1, R2, R3, and the capacitor CI are properly set, the on-time of the transistor can be easily controlled to achieve the protection of the circuit components. After branching, the branch connected to the other end of the winding is the same.

As shown in FIG. 7, the input filter capacitor C, the drive transformer T2, the transistors TR1, TR2, the output transformer T1 and the rectified output circuit are connected. The filter capacitor C is connected between the voltage input terminal and the ground, and the source voltage input terminal is connected to the output transformer. The middle tap of the primary winding, the primary winding of the driving transformer T2 is connected to the collectors of the transistors TR1 and TR2, the secondary winding of the driving transformer T2 is connected to the bases of the transistors TR1 and TR2, and the emitters of the transistors TR1 and TR2 are grounded. The collectors of the transistors TR1 and TR2 are connected to the two ends of the primary winding of the output transformer T1, and the rectifier windings D1 and D2 are respectively connected to the two ends of the secondary winding of the output transformer T1, and the intermediate tap of the secondary winding of the output transformer T1 is the output voltage reference terminal, and the rectifier diode The cathodes of D1 and D2 are connected to the output voltage terminal.

A soft start circuit is provided between the center tap of the secondary winding of the drive transformer T2 and the source voltage input terminal. The soft start circuit is composed of a resistor R1 and a capacitor C1. The resistor R1 and the capacitor C1 are connected in parallel. The parallel branch of the resistor R1 and the capacitor C1 is connected between the source voltage input terminal and the intermediate tap of the secondary winding of the drive transformer T2.

At the moment of voltage connection, since the capacitor C1 is in the off state, the voltage can be directly applied to the transistors TR1, TR2 via the resistor R1. When the capacitor C1 is charged to a certain voltage, the base current of the transistors TR1, TR2 can be increased by driving the coil of the transformer T2. The length of this time can be controlled by selecting the size of the capacitor C1 parameter. The other input voltage is directly applied to the primary coil P1 of the output transformer T1. The collectors of the transistors provide them with a collector voltage that works properly. When the circuit is working normally, the secondary winding P3 of the output transformer T1 is coupled with the primary coil P1 to gradually output energy, thereby completing the function of the entire converter. By selecting the parameters of the resistor R1 and the capacitor C1, it is convenient to control the transistor to conduct after the input current and voltage are stabilized, and to accelerate the on-time of the transistor at the start-up instant, thereby greatly improving the startup characteristics of the circuit. At the same time, this circuit can also ensure that the voltage applied to the base of the transistors TR1, TR2 does not exceed its limit value, which provides a good protection for the components.

As shown in FIG. 8, the second embodiment differs from the first embodiment in a soft start circuit. The soft start circuit is composed of a resistor R1, a resistor R2 and a capacitor C1. The resistor R1 and the resistor R2 are connected in series. The series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground, and the series terminal of the resistor R1 and the resistor R2. Connected to the center tap of the secondary winding of the drive transformer, the series terminal is also connected to the source voltage input via capacitor C1. Using the voltage divider of resistors R1 and R2, the voltage on resistor R2 is set to determine the voltage applied to capacitor C1. By selecting the size of resistor R1, R2 and capacitor CI, the transistor can be conveniently controlled at the input. The current and voltage are stabilized and then turned on, and the soft start of the actual circuit.

As shown in FIG. 9, the third embodiment differs from the first embodiment in a soft start circuit. The soft start circuit is composed of a resistor R1, a resistor R2 and a Zener diode D1. The resistor R1 and the resistor R2 are connected in series, and the series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground, and the resistor R1 and the resistor R2 are connected. The series end is connected to the center tap of the secondary winding of the drive transformer, the series end is also connected to the cathode of the Zener diode D1, and the anode of the Zener diode D1 is grounded. The working principle is the same as above, the voltage divider of the resistors R1 and R2 is used, and the voltage regulator D1 is further stabilized. By selecting the parameters of R1, R2 and D1, the transistor can be conveniently controlled at the input current and voltage. Through, improve the startup characteristics.

As shown in FIG. 10, the fourth embodiment differs from the first embodiment in a soft start circuit. The soft start circuit is composed of a capacitor C1 and a Zener diode D1. The capacitor C1 and the Zener diode D1 are connected in parallel. The parallel branch of the capacitor C1 and the Zener diode D1 are connected to the source voltage input terminal and the middle tap of the secondary winding of the drive transformer. Wherein the cathode of the Zener diode D1 is connected to the source voltage input terminal, and the anode of the Zener diode D1 is connected to the center tap of the secondary winding of the drive transformer. The working principle of this circuit is to avoid the hard start of the transistors TR1 and TR2 and the voltage regulation through the charging process of the capacitor C1. Diode D1 further stabilizes the voltage, better providing a stable operating voltage for transistors TR1, TR2 at the start-up instant.

As shown in FIG. 11, the soft start circuit of the fifth embodiment is a Zener diode D1 connected between the source voltage input terminal and the center tap of the secondary winding of the drive transformer, wherein the cathode of the Zener diode D1 is connected to the source voltage input terminal. The anode of the Zener diode D1 is connected to the center tap of the secondary winding of the drive transformer. The Zener diode D1 is used to provide a soft-start voltage to the transistor to improve the startup characteristics.

As shown in Fig. 12, the soft start circuit of the sixth embodiment is a resistor Ri connected between the source voltage input terminal and the center tap of the secondary winding of the drive transformer. The resistor R1 is used to provide a soft-start voltage to the transistor to improve the startup characteristics.

Claims

Rights request

1. A soft start micropower power converter comprising an input filter capacitor C, a drive transformer T2, a transistor TR1, a TR2, a coupled output transformer T1 and a rectified output circuit, characterized in that: a secondary winding and a source of the drive transformer A soft start circuit is provided between the voltage input terminals.

2. The soft-startable micropower power converter according to claim 1, wherein: said soft start circuit is composed of a resistor R1 and a capacitor C1, and the resistor R1 and the capacitor C1 are connected in series, and the resistor and the capacitor C1 are connected. The series branch is connected between the source voltage input terminal and the ground, and the series connection of the resistor R1 and the capacitor C1 is connected to the center tap of the secondary winding of the drive transformer.

3. The soft-startable micropower power converter according to claim 1, wherein: the soft start circuit is composed of a resistor R1, a resistor R2 and a capacitor C1, and the resistor R1 and the resistor R2 are connected in series, and the resistor is connected. The series connection branch of R1 and resistor R2 is connected between the source voltage input terminal and the ground, and the series connection end of the resistor R1 and the resistor R2 is connected to the intermediate tap of the secondary winding of the drive transformer, and the series connection terminal is also connected to the ground through the capacitor C1 and the ground. Connected.

4. The soft-startable micropower power converter according to claim 1, wherein: the soft start circuit is composed of a resistor R1, a resistor R2 and an inductor L1, and the resistor R1, the resistor R2 and the inductor L1 are sequentially connected. Connected, the series branch is connected between the source voltage input terminal and the ground, and the series connection of the resistor R1 and the resistor R2 is connected to the center tap of the secondary winding of the drive transformer.

5. The soft-startable micropower power converter according to claim 1, wherein: said soft start circuit is composed of resistors R1, R2, R3, R4, capacitor CI and capacitor C3, resistor R1 and resistor. R2 is connected in series, the series connection of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground, and the series connection end of the resistor R1 and the resistor R2 is connected to the intermediate tap of the secondary winding of the drive transformer, and the resistor R3 is connected to Between the connection terminal of the secondary winding of the driving transformer and the base of the transistor TR1, one end of the capacitor C1 is connected to the base of the transistor TR1, and the other end thereof is grounded; the resistor R4 is connected to the other connection end of the secondary winding of the driving transformer. Between the base of the transistor TR2 and the base of the transistor TR2, the capacitor C3 terminates the base of the transistor TR2, and the other end thereof is grounded.

The soft startable micro power converter according to claim 1, wherein: the DC bias circuit is composed of a resistor R1 and a capacitor C:, and the resistor is connected in parallel with the capacitor C1. The parallel branch of R1 and capacitor CI is connected between the source voltage input terminal and the center tap of the secondary winding of the drive transformer.

7. The soft-startable micropower power converter according to claim 1, wherein: said DC bias circuit is composed of a resistor R1, a resistor R2 and a capacitor C1, and the resistor R1 and the resistor R2 are connected in series, and the resistor A series branch of R1 and resistor R2 is connected between the source voltage input terminal and ground, and a series terminal of the resistor R1 and the resistor R2 is connected to a center tap of the secondary winding of the drive transformer, and the series terminal is also connected to the source voltage input terminal through the capacitor C1. Connected.

8. The soft-startable micropower power converter according to claim 1, wherein: said DC bias circuit is composed of a resistor R1, a resistor R2 and a Zener diode D1, and the resistor R1 and the resistor R2 are connected in series. The series branch of the resistor R1 and the resistor R2 is connected between the source voltage input terminal and the ground, and the series end of the resistor R1 and the resistor R2 is connected to the center tap of the secondary winding of the driving transformer, and the series terminal is also connected to the Zener diode D1. Cathode connection, anode of Zener diode D1 is grounded.

9. The soft-startable micropower power converter according to claim 1, wherein the DC bias circuit is composed of a capacitor C1 and a Zener diode D1, and the capacitor C1 and the Zener diode D1 are connected in parallel. A parallel branch of the capacitor C1 and the Zener diode D1 is connected between the source voltage input terminal and the center tap of the secondary winding of the drive transformer, wherein the cathode of the Zener diode D1 is connected to the source voltage input terminal, and the anode connection of the Zener diode D1 is driven. The center tap of the secondary winding of the transformer.

10. The soft-startable micropower power converter of claim 1 wherein: said DC bias circuit is stable between a source voltage input terminal and a center tap of a secondary winding of the drive transformer. The diode D1, wherein the cathode of the Zener diode D1 is connected to the source voltage input terminal, and the anode of the Zener diode D1 is connected to the center tap of the secondary winding of the driving transformer.

11. The soft-startable micropower power converter of claim 1 wherein: said DC bias circuit is a resistor connected between a source voltage input terminal and a center tap of a secondary winding of the drive transformer. Rl.