PROTECTIVE CIRCUITS FOR SECONDARY BATTERY PACKS

• US 20090315517A1
• Filed: 12/07/2006
• Published: 12/24/2009
• Est. Priority Date: 12/07/2005
• Status: Active Grant

• Current Assignee: BYD Company Limited
• Original Assignee: BYD Company Limited
• Inventors: Chen, Fang
• Granted Patent: US 8,129,948 B2
• Time in Patent Office: Days
• US Class Current: 320/134
• CPC Class Codes: H02J 7/00302 Overcharge protection
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00306 Overdischarge protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

This invention discloses a charging/discharging protective circuit for a secondary battery pack, having an over-charging/discharging voltage comparator, a reference voltage source and a battery status decision circuit. There is also a sampling circuit having a sequential pulse generator for generating pulses for selecting one of the batteries in the battery pack for testing purposes. The pulse generator provides M-channel gating pulses to the selection circuit of the battery under test and provides sampling pulses to the over-charging/discharging voltage comparators. The reference voltage source has a regulated output circuit. This invention uses time division inspection methods to provide a cost-effective solution for inspecting batteries in a battery pack.

Claims

1. A protective circuit for a secondary battery pack having a plurality of batteries, comprising:

a sampling circuit generating pulses for selecting one or more of the batteries for inspection;

a selection circuit for receiving said pulses and selecting a battery in the battery pack;

a reference voltage source providing one or more reference levels;

a plurality of voltage comparators each receiving one of the reference levels to compare with the level of the selected battery and generating one or more compared levels;

a battery status decision circuit connected to the comparators generating control signals as a function of the compared levels; and

a battery charging/discharging control circuit for controlling the charging or discharging of the selected battery in response to the control signals.

2. The protective circuit of claim 1 wherein the reference voltage source has a regulated output circuit allowing the calibration of protection thresholds.

3. The protective circuit of claim 2 wherein in the regulated output circuit, there is a multi-stage voltage divider with adjustable-ratio resistors and fixed-ratio resistors providing stepwise adjusted resistance for calibrating the protective circuit to be within predetermined inspection ranges.

4. The protective circuit of claim 1 wherein the sampling circuit includes a sequential pulse generator.

5. The protective circuit of claim 1 wherein the sampling circuit includes a sequential pulse generator generating pulses for the inspecting the batteries at predetermined time intervals.

6. The protective circuit of claim 4 wherein the sampling circuit further includes a square wave generator, cascaded oscillator, frequency divider and amplifier.

7. The protective circuit of claim 1 wherein the sampling circuit causes the intermittently inspection the voltages of the batteries at set time intervals.

8. The protective circuit of claim 1 wherein the batteries of the secondary battery pack are lithium ion batteries.

9. The protective circuit of claim 1 wherein the battery pack is configured in multiples of M batteries where M is an integer between 2 and 8.

10. The protective circuit of claim 1 further including a level conversion circuit connected between the selection circuit and the comparators.

11. The protective circuit of claim 10 wherein the level conversion circuit is a differential operational amplifier.

12. The protective circuit of claim 1 the protective circuit is a discrete hybrid digital/analogue circuit.

13. The protective circuit of claim 1 the protective circuit is a hybrid integrated digital/analogue circuit.

14. A protective circuit for a secondary battery pack having a plurality of batteries, comprising:

a sampling circuit generating pulses for selecting one or more of the batteries for inspection, wherein the sampling circuit includes a sequential pulse generator generating pulses for inspecting selected one of the batteries at predetermined time intervals;

a selection circuit receiving the pulses and for selecting a battery in the battery pack;

a reference voltage source providing one or more reference levels, wherein the reference voltage source has a regulated output circuit allowing the calibration of protection thresholds;

a plurality of voltage comparators each receiving one of the reference levels to compare with the level of the selected battery and generating one or more compared levels;

a battery status decision circuit connected to the comparators generating control signals as a function of the compared levels; and

a battery charging/discharging control circuit for controlling the charging or discharging of the selected battery in response to the control signals.

15. The protective circuit of claim 14 wherein in the regulated output circuit, there is a multi-stage voltage divider with adjustable-ratio resistors and fixed-ratio resistors providing stepwise adjusted resistance for calibrating the protective circuit to be within predetermined inspection ranges.

16. The protective circuit of claim 14 wherein the batteries of the secondary battery pack are lithium ion batteries.

17. The protective circuit of claim 14 wherein the battery pack is configured in multiples of M batteries where M is an integer between 2 and 8.

18. The protective circuit of claim 14 further including a level conversion circuit connected between the selection circuit and the comparators.

19. The protective circuit of claim 14 the protective circuit is a discrete hybrid digital/analogue circuit.

20. The protective circuit of claim 14 the protective circuit is a hybrid integrated digital/analogue circuit.