WO1990016024A1 - Computer with provision for continued operation during battery change - Google Patents

Computer with provision for continued operation during battery change Download PDF

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Publication number
WO1990016024A1
WO1990016024A1 PCT/US1990/003203 US9003203W WO9016024A1 WO 1990016024 A1 WO1990016024 A1 WO 1990016024A1 US 9003203 W US9003203 W US 9003203W WO 9016024 A1 WO9016024 A1 WO 9016024A1
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WO
WIPO (PCT)
Prior art keywords
battery
computer
main
bridge
power
Prior art date
Application number
PCT/US1990/003203
Other languages
French (fr)
Inventor
Ken Dulaney
Phillip Todd Nash
Original Assignee
Grid Systems Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Grid Systems Corporation filed Critical Grid Systems Corporation
Publication of WO1990016024A1 publication Critical patent/WO1990016024A1/en

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Classifications

    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/26Power supply means, e.g. regulation thereof
    • G06F1/263Arrangements for using multiple switchable power supplies, e.g. battery and AC
    • GPHYSICS
    • G06COMPUTING; CALCULATING OR COUNTING
    • G06FELECTRIC DIGITAL DATA PROCESSING
    • G06F1/00Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00
    • G06F1/26Power supply means, e.g. regulation thereof
    • G06F1/30Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations

Definitions

  • This invention relates to computers, other processor based controllers, and generally to any electrical device requiring an uninterrupted power supply for uninterrupted data and status retention.
  • the invention is concerned with battery powered portable, hand held or laptop computers which require a change of battery from time to time or other logic circuitry which must be maintained through main power supply interruptions.
  • portable computers rely on batteries for power.
  • portable is intended to include all types of relatively compact computers which rely on or could rely on batteries, including those commonly known as portable computers, laptop computers, hand held computers or clipboard type computers (as described in copending application Serial No. ' 5G5..A.7. entitled "Hand Held
  • Most battery powered portable computers include an indicator, such as an LED, to signal to the operator when the battery is low in charge.
  • an indicator such as an LED
  • the operator may have approximately ten to fifteen minutes to finish the project on which he is working, without computer failure.
  • the computer must then be turned off, and the battery removed and replaced. Such a required change of battery can be disruptive if the operator does not have a chance to finish a project.
  • a "bridge battery” is provided, embedded in a computer and not routinely changeable, for allowing the main computer battery to be removed and replaced without turning off the computer.
  • the bridge battery powers the computer or just the necessary circuitry within the computer during the short time it is without a main battery.
  • the bridge battery preferably is always connected to power the computer, during times when the computer is turned on. When the main battery is present there is essentially no power drain on the bridge battery in spite of its connection to the computer, because the computer draws from the main battery.
  • the bridge battery is not removed from the computer, and accordingly it must be charged in situ. Therefore, to maintain a charge at all times, the bridge battery must be charged from the main battery.
  • the charging of the bridge battery can be accomplished, i.e. by trickle charging or by fast charging.
  • fast charging is used, as preferable over the small but constant power drain required for charging solely by trickle charging.
  • trickle charging may not provide enough gain in charge before the next change of main battery is required. Therefore a quick charge circuit for the bridge battery is included in the preferred embodiment of the present invention.
  • the circuit draws power from the main battery for a short time (e.g. five minutes), to charge the bridge battery at a high rate each time a new main battery is inserted into the computer.
  • the high rate quick charge is of very short duration, lasting only long enough to guarantee a sufficient charge on the bridge battery.
  • the charging circuit also outputs a very low trickle charge, to keep the bridge battery at full charge until it is again needed.
  • a further object is to accomplish this using an embedded bridge battery having short endurance but adequate to provide a power bridge during the short period when the battery is being changed.
  • the bridge battery is charged in a fast charge by power from the new battery, upon the new battery's being installed in the computer.
  • Figure 1 is a simplified schematic view in block diagram form, indicating basic operation of the bridge battery system of the present invention for a computer.
  • Figure 2 is a circuit diagram showing an example of a bridge battery charging circuit for fast charge followed by trickle charge.
  • Figures 2A, 2B and 2C are simple graphs demonstrating operation of the circuit of Figure 2.
  • Figure 3 is a circuit diagram showing a main power supply of a computer, including the bridge battery charging circuit of Figure 2.
  • Figure 1 indicates in simplified block diagram form a system in accordance with the invention for enabling an instrument such as a portable computer to continue operating during battery replacement.
  • a computer is indicated at 10, shown as normally connected to a main battery pack 12 or in the alternative an external power source 14. Both the main battery pack 12 and the external power source 14 can be removed or can fail. For field use without main battery recharging, the main battery pack 12 will have to be replaced with a freshly charged battery pack at certain intervals.
  • a "bridge" battery 22 is shown connected to the computer.
  • the small, relatively low-capacity bridge battery 22 may be connected continuously to the computer as indicated, for powering the computer for those short periods of time, e.g. several minutes, when the main battery pack 12 is being removed and replaced. This enables the computer 10 to continue operating without interruption.
  • the bridge battery can be large enough, if desired, to power the computer in a quiescent mode for a much longer period than required to change batteries. E.g. if battery power goes very low and the computer is automatically put i a standby mode, the prolonged powering of the standby mode by the bridge battery could be made to give the operator time to go out and purchase new dry cell batteries, or even to charge a rechargeable battery pack.
  • Figure 1 shows a provision for charging the bridge battery 22 using a newly replaced battery pack 12 or newly connected external power source 14.
  • the main switch including connection of external power when the battery is low
  • a charged power source is available (as indicated in the block 18)
  • a charge control circuit 30 effects the fast charge.
  • the charge control 30 then applies a slow charge, continuously permitting the flow of a low current trickle charge to the bridge battery 22 from the main battery 12 or from the external source, whenever the main switch is on.
  • the initial fast charge is desirable to assure that the bridge battery will be available when needed.
  • the event of replacement of the main battery 12, indicated in the block 18 in Figure 1 is indicated as triggering the activation of a fast charge via the charge controlling circuitry 30. This could alternatively be by mechanical linkage or an electric sensing device actuated upon insertion of a charged battery pack.
  • Figure 1 shows the bridge battery 22 supplying temporary power only to RAM 24 of the computer 10. As further explained below, all active programs and data preferably are unloaded to RAM 24 when the main battery is to be replaced (or goes too low to operate the computer) , via a manual or automatic standby switch 26.
  • Figure 2 shows a battery charging circuit 30 of the system of the invention, with Figure 2A, 2B and 2C being graphs demonstrating operation of the circuit 30.
  • the fast charging is applied to the bridge battery 22 whenever a main power switch 32 is closed and also whenever a new main battery is placed in the computer 10 or other device or external power is applied, at a time when the main power switch 32 is on. If the main power switch 32 is open, changing of the main battery will not have any effect, and no charging (fast or trickle) will occur so long as the switch 32 is open. When the switch 32 is closed, fast charging of the bridge battery 22 will commence so long as there is a source of power connected to the computer, whether that source is the main battery 20 or an externally applied power source, i.e. a DC converter connected to the computer or the device 10.
  • a source of power connected to the computer whether that source is the main battery 20 or an externally applied power source, i.e. a DC converter connected to the computer or the device 10.
  • the computer 10 must first be put in a "standby" mode.
  • the standby switch and standby mode are effective to save the active programs and data in RAM while shutting down the remainder of the computer.
  • the operator of the device can use the standby switch to place the computer in the standby mode, then change the main battery, and then reactivate the computer by again using the standby switch.
  • the standby mode can be activated automatically whenever the main battery is removed, or whenever an external source is removed in the absence of a charged main battery. In any event the standby mode preferably is activated whenever the computer is run beyond a "low battery” warning light and approaches going too low to maintain the video memory and program memory.
  • Figure 1 shows this function with a block 33, which indicates detection of low battery and a signal being sent to the computer or to the standby switch 26 (or both) , to implement the function through software and/or hardware.
  • the bridge battery can slow the drain on the main battery in this period, or, if the user removes the battery pack 12, the bridge battery alone will be used.
  • the circuit 30 will supply approximately three minutes of fast charge to the bridge battery 22, in this preferred embodiment of the invention.
  • the switching on of the computer at the main power switch 32, or the replacement of the main battery with the power switch on, causes a jump in voltage in the circuit 30 at the location 34 shown in Figure 2, this jump being indicated schematically in the graph of Figure 2A.
  • the capacitor 36 resists the jump in voltage, and at the other side of the capacitor (location 38 in Figure 2) the voltage steps up in response. This is shown schematically in the graph of Figure 2B. As indicated in Figure 2B, this stepped-up voltage will only last for a short period which may be about three minutes. The stepped-up voltage will be bled off by a grounded resistor 40 (shown as 10 megohms) in Figure 2.
  • a fast charge at the high current level can be maintained on the bridge battery 22 for about three minutes without substantial risk to the battery 22 (which may comprise two 3.6 NiCad battery cells in series).
  • the input voltage may vary from about 11 volts to 18 volts.
  • the lowest voltage will occur when a main battery 20 is at low charge in the computer.
  • the highest voltage of 18 volts can occur when an external power source, i.e. a DC converter, is connected to the computer.
  • FIG. 2 shows one embodiment of a charging circuit for a bridge battery according to the invention, providing for a fast charge of short duration and then a continued trickle charge
  • Figure 3 shows the circuit 30 in one environment with which it may be used, the environment of a hand held notebook style computer as in the copending application referenced above.
  • Figure 3 shows main PC board power supply circuitry for a computer 10 with which the bridge battery circuit of the invention may be used.
  • the bridge battery charging circuit 30 is seen at the lower left in Figure 3.
  • a DC input jack 50 leads through noise filtering circuitry 52 and a common mode transformer 54 to an OR-ing diode D10.
  • a detector 56 detects when an external power source is connected at 50, as opposed to a battery.
  • a line 58 leads down to the main power circuitry, which is diode OR-ed in with the batteries — primarily cells (e.g. alkaline battery cells) at BC4 or NiCad battery cells at BC5.
  • the diode OR-ing is accomplished by diodes D10, D5 and D4, and it OR's all three power sources, i.e. primary cells, NiCad cells or the external source.
  • the circuit will always use the external source, through the diode OR-ing, when the external source is connected, since it is a higher voltage source than either type of batteries.
  • the contacts BC1-BC5 are in a battery compartment which may be configured in accordance with the disclosure of copending application Serial No. entitled “BATTERY COMPARTMENT” filed concurrently herewith, assigned to the same assignee as the present invention and incorporated herein by reference.
  • the main power switch SWl is a double pole, double throw (DPDT) switch. When the main switch is closed it connects the battery or external power (or power from a connected expansion module, indicated at 62 in Figure 3) to a location 64 labeled SWTCHD DC in Figure 3. This goes out toward a DC to DC converter which creates the voltages needed for running the machine.
  • DPDT double pole, double throw
  • the main power switch SWl also switches power into the bridge battery circuit 30, and connects the bridge battery circuit 30 with a 5 volt regulator labeled Q33.
  • a 5 volt regulator labeled Q33 To the right of the regulator Q33 is another diode OR-ing situation at D6 and D7.
  • the line into D7 receives power from the converter fed by 64, and this system voltage is OR-ed in by D6 and D7.
  • the regulator Q33 will not operate until the system is put in the standby mode and the main battery 13 removed, in which case the DC to DC converter is shut down, and the bridge battery 22 takes over operation of the RAM (see RAM VCC) , through the regulator Q33. Only the RAM is supplied through the bridge battery 22 and the regulator Q33.
  • D6 and D7 provide another OR-ing circuit between a plus 5 volt source from the DC to DC converter and the 5 volt regulator Q33, which is supplied by the bridge battery 22.
  • the auxiliary regulator at Q33 is fed by the bridge battery only if the power switch is closed and the main battery and external power sources are missing.
  • the standby mode which may be generated by a standby switch or automatically as mentioned above, is read by software.
  • the software goes about shutting down the DC to DC converter and taking all of the critical parameters out of the machine. It takes the program memory being run and the machine status and stores it in the main RAM. When this is completed, then the software shuts down the DC to DC converter. Following this, the main battery if installed, or otherwise the bridge battery, keeps the main RAM alive.
  • the diode VSK 140 comes into play to provide the current path from Q33 to ground.
  • FIG. 3 also indicates that an item 66 identified as VRAM PU may be powered by the main battery or the bridge battery during the standby mode. This is to put the video memory chip into a low power mode during standby mode.
  • Power distributing capacitors 68 are shown at the lower right in Figure 3, to reduce noise on the RAM VCC line. These do not absorb any power, but have the purpose of providing a low impedance source or reservoir of stored power.

Abstract

In a battery powered computer (10), a bridge battery circuit (18, 22, 30, 33) provides power to the computer (10) for a short period of time while the main battery (12) is removed and changed. This enables the computer (10) to be left partially on, but in a quiescent state, without committing the active program and data to disk or card memory while the battery (12) is being changed. A very small embedded battery or bridge battery (22) automatically powers the RAM (24) of the computer (10) upon removal of the main battery (12), following transfer of the computer (10) to a standby mode wherein all active programs are temporarily stored in RAM (24). A quick charge circuit (30) in the computer (10) provides several minutes of fast charging of the bridge battery (22) whenever a new battery is inserted. A very low trickle charge may be applied continuously after fast charging.

Description

APPLICATION FOR A UNITED STATES PATENT
COMPUTER WITH PROVISION FOR CONTINUED
OPERATION DURING BATTERY CHANGE
S P E C I F I C A T I O N
BACKGROUND OF THE INVENTION
This invention relates to computers, other processor based controllers, and generally to any electrical device requiring an uninterrupted power supply for uninterrupted data and status retention. In a particular form the invention is concerned with battery powered portable, hand held or laptop computers which require a change of battery from time to time or other logic circuitry which must be maintained through main power supply interruptions.
Many portable computers rely on batteries for power. As used herein, the term "portable" is intended to include all types of relatively compact computers which rely on or could rely on batteries, including those commonly known as portable computers, laptop computers, hand held computers or clipboard type computers (as described in copending application Serial No. '5G5..A.7. entitled "Hand Held
Computer", filed concurrently with this application assigned to the same assignee as the present invention and hereby incorporated in this application by reference) .
Most battery powered portable computers include an indicator, such as an LED, to signal to the operator when the battery is low in charge. Typically, when the low battery signal light is activated, the operator may have approximately ten to fifteen minutes to finish the project on which he is working, without computer failure. The computer must then be turned off, and the battery removed and replaced. Such a required change of battery can be disruptive if the operator does not have a chance to finish a project.
Other electrical implements, whether or not including microprocessors, often need an uninterrupted power supply. These include portable battery powered devices and also equipment normally run on line power, such as traffic light controllers, where the status and timing should be kept running at low power draw, even through a power failure which makes the traffic lights themselves temporarily inoperable.
SUMMARY OF THE INVENTION In accordance with the present invention, a "bridge battery" is provided, embedded in a computer and not routinely changeable, for allowing the main computer battery to be removed and replaced without turning off the computer. The bridge battery powers the computer or just the necessary circuitry within the computer during the short time it is without a main battery. The bridge battery preferably is always connected to power the computer, during times when the computer is turned on. When the main battery is present there is essentially no power drain on the bridge battery in spite of its connection to the computer, because the computer draws from the main battery.
The bridge battery is not removed from the computer, and accordingly it must be charged in situ. Therefore, to maintain a charge at all times, the bridge battery must be charged from the main battery. There are several ways the charging of the bridge battery can be accomplished, i.e. by trickle charging or by fast charging. In a preferred embodiment of the invention, fast charging is used, as preferable over the small but constant power drain required for charging solely by trickle charging. On any occasion when the bridge battery becomes fully discharged, trickle charging may not provide enough gain in charge before the next change of main battery is required. Therefore a quick charge circuit for the bridge battery is included in the preferred embodiment of the present invention. The circuit draws power from the main battery for a short time (e.g. five minutes), to charge the bridge battery at a high rate each time a new main battery is inserted into the computer. The high rate quick charge is of very short duration, lasting only long enough to guarantee a sufficient charge on the bridge battery.
In one preferred embodiment, the charging circuit also outputs a very low trickle charge, to keep the bridge battery at full charge until it is again needed.
It is therefore among the objects of the present invention to enhance the utility of a battery powered portable computer, by enabling the battery to be replaced while the computer continues to operate. A further object is to accomplish this using an embedded bridge battery having short endurance but adequate to provide a power bridge during the short period when the battery is being changed. In preferred embodiments the bridge battery is charged in a fast charge by power from the new battery, upon the new battery's being installed in the computer.
Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show preferred embodiments of the present invention and the principles thereof and what are now considered to be the best modes contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.
DESCRIPTION OF THE DRAWINGS Figure 1 is a simplified schematic view in block diagram form, indicating basic operation of the bridge battery system of the present invention for a computer. Figure 2 is a circuit diagram showing an example of a bridge battery charging circuit for fast charge followed by trickle charge.
Figures 2A, 2B and 2C are simple graphs demonstrating operation of the circuit of Figure 2.
Figure 3 is a circuit diagram showing a main power supply of a computer, including the bridge battery charging circuit of Figure 2.
DESCRIPTION OF PREFERRED EMBODIMENTS
In the drawings. Figure 1 indicates in simplified block diagram form a system in accordance with the invention for enabling an instrument such as a portable computer to continue operating during battery replacement. In Figure 1 a computer is indicated at 10, shown as normally connected to a main battery pack 12 or in the alternative an external power source 14. Both the main battery pack 12 and the external power source 14 can be removed or can fail. For field use without main battery recharging, the main battery pack 12 will have to be replaced with a freshly charged battery pack at certain intervals.
A "bridge" battery 22 is shown connected to the computer. The small, relatively low-capacity bridge battery 22 may be connected continuously to the computer as indicated, for powering the computer for those short periods of time, e.g. several minutes, when the main battery pack 12 is being removed and replaced. This enables the computer 10 to continue operating without interruption. As explained below, the bridge battery can be large enough, if desired, to power the computer in a quiescent mode for a much longer period than required to change batteries. E.g. if battery power goes very low and the computer is automatically put i a standby mode, the prolonged powering of the standby mode by the bridge battery could be made to give the operator time to go out and purchase new dry cell batteries, or even to charge a rechargeable battery pack. Figure 1 shows a provision for charging the bridge battery 22 using a newly replaced battery pack 12 or newly connected external power source 14. When either event occurs with the main switch on (including connection of external power when the battery is low) , or if the main switch is turned on while a charged power source is available (as indicated in the block 18) , this causes a fast charge to be applied to the bridge battery 22 for a short period, e.g. 3 minutes. A charge control circuit 30 effects the fast charge. In one embodiment, the charge control 30 then applies a slow charge, continuously permitting the flow of a low current trickle charge to the bridge battery 22 from the main battery 12 or from the external source, whenever the main switch is on. Upon replacement of the main battery pack 12, as discussed above, the initial fast charge is desirable to assure that the bridge battery will be available when needed. Thus, the event of replacement of the main battery 12, indicated in the block 18 in Figure 1, is indicated as triggering the activation of a fast charge via the charge controlling circuitry 30. This could alternatively be by mechanical linkage or an electric sensing device actuated upon insertion of a charged battery pack.
Figure 1 shows the bridge battery 22 supplying temporary power only to RAM 24 of the computer 10. As further explained below, all active programs and data preferably are unloaded to RAM 24 when the main battery is to be replaced (or goes too low to operate the computer) , via a manual or automatic standby switch 26. Figure 2 shows a battery charging circuit 30 of the system of the invention, with Figure 2A, 2B and 2C being graphs demonstrating operation of the circuit 30.
As can be seen from Figure 2, the fast charging is applied to the bridge battery 22 whenever a main power switch 32 is closed and also whenever a new main battery is placed in the computer 10 or other device or external power is applied, at a time when the main power switch 32 is on. If the main power switch 32 is open, changing of the main battery will not have any effect, and no charging (fast or trickle) will occur so long as the switch 32 is open. When the switch 32 is closed, fast charging of the bridge battery 22 will commence so long as there is a source of power connected to the computer, whether that source is the main battery 20 or an externally applied power source, i.e. a DC converter connected to the computer or the device 10.
If the main battery 20 is to be replaced with the main power switch on, in accordance with one embodiment of the invention, the computer 10 must first be put in a "standby" mode. The standby switch and standby mode are effective to save the active programs and data in RAM while shutting down the remainder of the computer. The operator of the device can use the standby switch to place the computer in the standby mode, then change the main battery, and then reactivate the computer by again using the standby switch. In one preferred embodiment, the standby mode can be activated automatically whenever the main battery is removed, or whenever an external source is removed in the absence of a charged main battery. In any event the standby mode preferably is activated whenever the computer is run beyond a "low battery" warning light and approaches going too low to maintain the video memory and program memory. This is implemented by sensors and software, and prevents loss of active programs and data inadvertently. Figure 1 shows this function with a block 33, which indicates detection of low battery and a signal being sent to the computer or to the standby switch 26 (or both) , to implement the function through software and/or hardware. The bridge battery can slow the drain on the main battery in this period, or, if the user removes the battery pack 12, the bridge battery alone will be used.
When the main power switch 32 is closed, or the main battery is replaced with the switch 32 on, the circuit 30 will supply approximately three minutes of fast charge to the bridge battery 22, in this preferred embodiment of the invention.
The switching on of the computer at the main power switch 32, or the replacement of the main battery with the power switch on, causes a jump in voltage in the circuit 30 at the location 34 shown in Figure 2, this jump being indicated schematically in the graph of Figure 2A. The capacitor 36 resists the jump in voltage, and at the other side of the capacitor (location 38 in Figure 2) the voltage steps up in response. This is shown schematically in the graph of Figure 2B. As indicated in Figure 2B, this stepped-up voltage will only last for a short period which may be about three minutes. The stepped-up voltage will be bled off by a grounded resistor 40 (shown as 10 megohms) in Figure 2.
Meanwhile, until this charge bleeds down to a certain level 42 in Figure 2B, an N-channel FET 44 turns "on" due to the increased voltage, effectively becoming a short in the circuit 30. Thus, the charge current path through the bridge battery 22, while the N-channel FET 44 is on, is through a resistor 46 (shown as 1000 ohms in Figure 2) but not through a 2.2 kiloh resistor shown at 48. Thus, the charge current is determined by the resistor 46 and is at the high level for a fast charge, or .25C as indicated in the graph of Figure 2C.
However, as shown in the curve of Figure 2B, when the voltage in the line 38 drops to the point 42 the transistor 44 begins to turn off, going to high impedance and effectively becoming an open switch. At this point, the principal current path is through both the resistor 46 (e.g. 1000 ohms) and the resistor 48 (e.g. 2.2 kilohms) . This establishes the secondary charge current, or about 0.04C as shown in Figure 2C. This is the trickle charge which is constantly applied to the bridge battery 22 whenever the computer or the device 10 is on, and after a short duration of fast charge. Figure 2B indicates that the time constant T of the fast charge is determined by the rate at which the resistor 40 bleeds the charge from the line 38.
A fast charge at the high current level can be maintained on the bridge battery 22 for about three minutes without substantial risk to the battery 22 (which may comprise two 3.6 NiCad battery cells in series).
In one embodiment of the invention, and as indicated in Figure 2, the input voltage may vary from about 11 volts to 18 volts. The lowest voltage will occur when a main battery 20 is at low charge in the computer. The highest voltage of 18 volts can occur when an external power source, i.e. a DC converter, is connected to the computer.
Although the circuit 30 shown in Figure 2 explains one embodiment of a charging circuit for a bridge battery according to the invention, providing for a fast charge of short duration and then a continued trickle charge, Figure 3 shows the circuit 30 in one environment with which it may be used, the environment of a hand held notebook style computer as in the copending application referenced above.
Figure 3 shows main PC board power supply circuitry for a computer 10 with which the bridge battery circuit of the invention may be used.
The bridge battery charging circuit 30 is seen at the lower left in Figure 3.
Starting from the top of the circuit diagram of Figure 3, a DC input jack 50 leads through noise filtering circuitry 52 and a common mode transformer 54 to an OR-ing diode D10. A detector 56 detects when an external power source is connected at 50, as opposed to a battery.
A line 58 leads down to the main power circuitry, which is diode OR-ed in with the batteries — primarily cells (e.g. alkaline battery cells) at BC4 or NiCad battery cells at BC5. The diode OR-ing is accomplished by diodes D10, D5 and D4, and it OR's all three power sources, i.e. primary cells, NiCad cells or the external source. The circuit will always use the external source, through the diode OR-ing, when the external source is connected, since it is a higher voltage source than either type of batteries.
A circuit 60 shown in Figure 3, and comprising Q27, R8132, D9 and RB 131, shunts D4. This is the circuit for charging the battery if it happens to be the NiCad rechargeable battery. The contacts BC1-BC5 are in a battery compartment which may be configured in accordance with the disclosure of copending application Serial No. entitled "BATTERY COMPARTMENT" filed concurrently herewith, assigned to the same assignee as the present invention and incorporated herein by reference.
The main power switch SWl is a double pole, double throw (DPDT) switch. When the main switch is closed it connects the battery or external power (or power from a connected expansion module, indicated at 62 in Figure 3) to a location 64 labeled SWTCHD DC in Figure 3. This goes out toward a DC to DC converter which creates the voltages needed for running the machine.
As indicated the main power switch SWl also switches power into the bridge battery circuit 30, and connects the bridge battery circuit 30 with a 5 volt regulator labeled Q33. To the right of the regulator Q33 is another diode OR-ing situation at D6 and D7. The line into D7 receives power from the converter fed by 64, and this system voltage is OR-ed in by D6 and D7. The regulator Q33 will not operate until the system is put in the standby mode and the main battery 13 removed, in which case the DC to DC converter is shut down, and the bridge battery 22 takes over operation of the RAM (see RAM VCC) , through the regulator Q33. Only the RAM is supplied through the bridge battery 22 and the regulator Q33.
Thus, D6 and D7 provide another OR-ing circuit between a plus 5 volt source from the DC to DC converter and the 5 volt regulator Q33, which is supplied by the bridge battery 22. The auxiliary regulator at Q33 is fed by the bridge battery only if the power switch is closed and the main battery and external power sources are missing. The standby mode, which may be generated by a standby switch or automatically as mentioned above, is read by software. The software goes about shutting down the DC to DC converter and taking all of the critical parameters out of the machine. It takes the program memory being run and the machine status and stores it in the main RAM. When this is completed, then the software shuts down the DC to DC converter. Following this, the main battery if installed, or otherwise the bridge battery, keeps the main RAM alive. When the bridge battery is being discharged while powering the memory, the diode VSK 140 comes into play to provide the current path from Q33 to ground.
When the operator hits the standby switch again, this has the effect of restoring all of the programs, previous video display, etc. All of the parameters are restored throughout all of the hardware, after the power supply has been brought up again by insertion of a new battery, connection of an external source, etc.
Figure 3 also indicates that an item 66 identified as VRAM PU may be powered by the main battery or the bridge battery during the standby mode. This is to put the video memory chip into a low power mode during standby mode.
Power distributing capacitors 68 are shown at the lower right in Figure 3, to reduce noise on the RAM VCC line. These do not absorb any power, but have the purpose of providing a low impedance source or reservoir of stored power.
While we have illustrated and described the preferred embodiments of our invention, it is to be understood that these are capable of variation and modification, and we therefore do not wish to be limited to the precise details set forth, but desire to avail ourselves of such changes and alterations as fall within the purview of the following claims.

Claims

We claim:
1. In a computer having a housing and a display and operable on a main battery, a system for preventing loss of
5 active memory and data in the computer during periods when the main battery is being replaced, comprising, battery replacement means for enabling removal and replacement of the main battery, bridge battery means within the computer housing and 10 connected to the computer, with sufficient storage capability for powering at least a portion of the computer for a short period of time sufficient to enable replacement of the main battery, and charging means for recharging the bridge battery means 15 after it has been drawn down by powering the computer during main battery replacement.
2. The invention of claim 1, wherein the charging means includes means for charging the bridge battery using
20 power from the newly replaced main battery.
3. The invention of claim 2, wherein the charging means includes fast charge means for applying a fast charge to the bridge battery means from the main battery for a
25. short time after replacement of the main battery.
4. The invention of claim 3, further including trickle charge means for applying a very low and continuous trickle charge to the bridge battery from the main battery,
30 following application of said fast charge.
5. The invention of claim 1, wherein the charging means includes means for charging the bridge battery means using power from the main battery, and for charging.the
35 bridge battery means within about 3 minutes to a point sufficient to allow the bridge battery means to provide enough power to support said portion of the computer for said short period of time.
6. The invention of claim 1, wherein the computer includes standby means for placing the computer in a standby mode wherein the power-drawing components of the computer are all shut down except the display memory and the main RAM, which serves as said portion of the computer, and the bridge battery means being connected to power the main RAM and display memory during the standby mode when the main battery is removed so that display memory and active memory are preserved, and the standby means including restore means for restoring the computer to full operation after replacement of the main battery.
7. The invention of claim 6, wherein the standby means includes means for automatically placing the computer in the standby mode when the main battery goes to a preselected low level of charge and then maintaining the RAM with the bridge battery means.
8. In a computer operable on a main battery, a circuit for retaining a main random access memory or RAM powered and active during change of the main battery, comprising, a bridge battery in the circuit, of smaller capacity than the main battery, means in the circuit for sensing the switching on of the computer at a main power switch, or a change to a higher voltage source powering the computer when the main power switch is closed, means for initiating a fast charge of the bridge battery for a short period of time in response to the switching on of the main switch or the sensing of said higher voltage source, and means for engaging the bridge battery to power the computer's main RAM when the main power switch is closed and no other source of power is present.
9. The invention of claim 8, further including means in the circuit for applying a slow, trickle charge to the bridge battery using the higher voltage source, following the fast charge.
10. The invention of claim 8, further including standby means for placing the computer in a standby mode wherein the main RAM is maintained but substantially all other power-drawing components of the computer are all shut down, whenever the main battery is removed from the computer.
11. The invention of claim 10, wherein the standby means includes means for automatically placing the computer in the standby mode when the battery goes to a preselected low level of charge, and then maintaining the RAM with the bridge battery.
PCT/US1990/003203 1989-06-12 1990-06-06 Computer with provision for continued operation during battery change WO1990016024A1 (en)

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US36495089A 1989-06-12 1989-06-12
US364,950 1989-06-12

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AU5921990A (en) 1991-01-08
CA2018651A1 (en) 1990-12-12
CN1050100A (en) 1991-03-20

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