Battery charging circuit and battery pack

Abstract

A battery charging circuit includes: a switching circuit having a charging switch and a protection switch connected in series, an isolation element, and a protection circuit. The charging switch, with its end near the high side of the battery module, is connected to the negative terminal of a bias voltage source. The isolation element is connected to the positive terminal of the bias voltage source and a logic drive source. The protection circuit is connected across the isolation element and the protection switch. When the logic drive source provides a drive current to the isolation element, the isolation element conducts, causing the bias voltage source to turn on the charging switch. The protection circuit is configured to control the on and off of the protection switch based on the voltage drop across it.

Claims

1. A battery charging circuit, detachably connected to a charger and connected to a bias voltage source, a logic drive source, and a battery module, the battery charging circuit comprising: A switching circuit is detachably connected between a positive charging terminal of the charger and a high side of the battery module. The switching circuit includes a charging switch and a protection switch connected back-to-back in series, wherein the end of the charging switch near the high side of the battery module is connected to a negative terminal of the bias voltage source; an isolation element is connected to a positive terminal of the bias voltage source, the logic drive source, and a control terminal of the charging switch; and a protection circuit is connected to both ends of the isolation element and the protection switch. When the charger is connected to the battery charging circuit and is charging normally, and the logic drive source provides a drive current to the isolation element, the isolation element is turned on, causing a bias voltage provided by the bias voltage source to turn on the charging switch. The protection circuit turns on the protection switch based on a voltage drop across the protection switch. When a short circuit occurs during charging, the protection circuit turns off the protection switch based on the voltage drop across the protection switch.

2. The battery charging circuit as described in claim 1, wherein, The charging switch is disposed between the positive charging terminal and the protection switch. The protection circuit includes: an NPN bipolar transistor, one emitter terminal of which is connected to a node connecting the charging switch and the protection switch; a first resistor, one end of which is connected to a collector terminal of the NPN bipolar transistor and a control terminal of the protection switch; a second resistor, one end of which is connected to the other end of the first resistor, and the other end of which is connected to a base terminal of the NPN bipolar transistor; a first diode, one anode of which is connected to the other end of the second resistor; and a third resistor, one end of which is connected to a cathode of the first diode, and the other end of which is connected to the end of the protection switch away from the charging switch. Specifically, when the charger is connected to the battery charging circuit and is charging normally, and the logic drive source provides the drive current to the isolation element, the isolation element is turned on, causing the charging switch to turn on and the NPN bipolar transistor to turn off. The protection circuit turns on the protection switch based on the voltage drop across the protection switch being greater than the voltage drop across the third resistor. When a short circuit occurs in the charger during the charging process, the NPN bipolar transistor is turned on, and the protection circuit turns off the protection switch based on the voltage drop across the protection switch being greater than the voltage drop across the third resistor.

3. The battery charging circuit as claimed in claim 2 further includes a fourth resistor, one end of which is connected to one end of the charging switch connected to the protection switch, and the other end of which is connected to the control terminal of the charging switch.

4. The battery charging circuit as claimed in claim 2 further includes a fifth resistor, one end of which is connected to one end of the protection switch connected to the charging switch, and the other end of which is connected to the control terminal of the protection switch.

5. The battery charging circuit as described in claim 2, wherein, The charging switch is an N-channel metallic oxide semiconductor field effect transistor (NMOSFET) with a body diode. One gate of the NMOSFET is the control terminal of the charging switch, one drain of the NMOSFET is one end of the charging switch connected to the positive charging terminal of the charger, and one source of the NMOSFET is one end of the charging switch connected to the protection switch.

6. The battery charging circuit as described in claim 2, wherein, The protection switch is an NMOSFET with a body diode. One gate of the NMOSFET is the control terminal of the protection switch, one drain of the NMOSFET is connected to the high side of the battery module, and one source of the NMOSFET is connected to the charging switch.

7. The battery charging circuit as described in claim 2, wherein, The isolation element is an optocoupler. One primary side of the optocoupler has a light-emitting diode (LED), and the secondary side has a phototransistor. One end of the LED is connected to the logic drive source, and the other end is grounded. One end of the phototransistor is connected to the positive terminal of the bias voltage source, and the other end is connected to the control terminal of the charging switch and a node connecting the first resistor and the second resistor. When the logic drive source provides the driving current to the LED, the LED becomes forward biased, the phototransistor conducts, and the bias voltage turns on the charging switch.

8. The battery charging circuit as claimed in claim 1, wherein, The isolation element is an optical coupler, a digital isolator, or an opto-emulator.

9. The battery charging circuit as claimed in claim 1, wherein, The charging switch is positioned between the high side of the battery module and the protection switch. The protection circuit includes: an NPN bipolar transistor, one emitter of which is connected to the end of the protection switch connected to the positive charging terminal of the charger; a first resistor, one end of which is connected to the collector of the NPN bipolar transistor and a control terminal of the protection switch; a second resistor, one end of which is connected to the other end of the first resistor and the other end of which is connected to the base of the NPN bipolar transistor; a first diode, one anode of which is connected to the other end of the second resistor; a third resistor, one end of which is connected to the cathode of the first diode and the other end of which is connected to the end of the protection switch connected to the charging switch; a fourth resistor, one end of which is connected to the end of the charging switch connected to the high side of the battery module; a fifth resistor, one end of which is connected to the other end of the fourth resistor; and a sixth resistor, one end of which is connected to the other end of the fifth resistor and the isolation element. A PNP bipolar transistor, one emitter terminal of which is connected to the other end of the sixth resistor, and one base terminal of which is connected to a node connecting the fourth and fifth resistors; and a second diode, one anode of which is connected to one collector terminal of the PNP bipolar transistor, and one cathode of which is connected to a node connecting the first and second resistors; wherein, when the charger is connected to the battery charging circuit and is charging normally, and the logic drive source provides the drive current to the isolation element, the isolation element is turned on to conduct the charging switch through the fourth and fifth resistors, and the NPN bipolar transistor is turned off, and the protection circuit turns on the protection switch based on the voltage drop across the protection switch being greater than the voltage drop across the third resistor; when the charger experiences a short circuit during the charging process, the NPN bipolar transistor is turned on, and the protection circuit turns off the protection switch based on the voltage drop across the protection switch being less than the voltage drop across the third resistor.

10. The battery charging circuit as claimed in claim 9 further includes a seventh resistor, one end of which is connected to one end of the protection switch connected to the charging switch, and the other end of which is connected to the control terminal of the protection switch.

11. The battery charging circuit as described in claim 9, wherein, The charging switch is an N-channel metallic oxide semiconductor field effect transistor (NMOSFET) with a body diode. One gate of the NMOSFET is the control terminal of the charging switch, one drain of the NMOSFET is one end of the charging switch connected to the protection switch, and one source of the NMOSFET is one end of the charging switch connected to the high side of the battery module.

12. The battery charging circuit as described in claim 9, wherein, The protection switch is an N-channel metallic oxide semiconductor field effect transistor (NMOSFET) with a body diode. One gate of the NMOSFET is the control terminal of the protection switch, one drain of the NMOSFET is one end of the protection switch connected to the charging switch, and one source of the NMOSFET is one end of the protection switch connected to the positive charging terminal of the charger.

13. The battery charging circuit as described in claim 9, wherein, The isolation element is an optocoupler. The primary side of the optocoupler has a light-emitting diode (LED), and the secondary side of the optocoupler has a phototransistor. One end of the LED is connected to the logic drive source, and the other end of the LED is grounded. One end of the phototransistor is connected to the positive terminal of the bias voltage source, and the other end of the phototransistor is connected to the control terminal of the charging switch, the fifth resistor, and the sixth resistor. When the logic drive source provides the drive current to the LED, the LED becomes forward biased, the phototransistor conducts, and the bias voltage turns on the charging switch.

14. A battery pack detachably connected to a charger and a load, the battery pack comprising: A battery module; a battery management system including a bias voltage source, a charging controller, and a discharging controller, wherein the charging controller includes a logic drive source; a battery discharging circuit connecting the discharging controller and the battery module, and detachably connected to the load; a battery charging circuit separate from the battery discharging circuit, detachably connected to the charger, and connected to the bias voltage source, the logic drive source, and the battery module, the battery charging circuit including: a switching circuit detachably connected between a positive charging terminal of the charger and a high side of the battery module, the switching circuit including a charging switch and a protection switch connected back-to-back in series, wherein one end of the charging switch near the high side of the battery module is connected to a negative terminal of the bias voltage source; an isolation element connecting a positive terminal of the bias voltage source, the logic drive source, and a control terminal of the charging switch; and a protection circuit connecting the two ends of the isolation element and the protection switch; Specifically, when the charger is connected to the battery charging circuit and is charging normally, and the logic drive source provides a drive current to the isolation element, the isolation element is turned on, causing the bias voltage provided by the bias voltage source to turn on the charging switch. The protection circuit turns on the protection switch based on a voltage drop across the protection switch. When a short circuit occurs during the charging process, the protection circuit turns off the protection switch based on the voltage drop across the protection switch.

15. The battery pack as claimed in claim 14, wherein, The battery module includes multiple battery cells.

16. The battery pack as claimed in claim 14, wherein, Both the charging controller and the discharging controller include at least one of a microcontroller, a microprocessor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and a programmable logic controller.

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