Battery voltage regulator protection circuits

• US 6,288,881 B1
• Filed: 08/17/1999
• Issued: 09/11/2001
• Est. Priority Date: 08/17/1999
• Status: Expired due to Fees

• Current Assignee: James D. Sullivan, John A. Melvin
• Original Assignee: James D. Sullivan, John A. Melvin
• Inventors: Sullivan, James D., Melvin, John A.
• Primary Examiner(s): SHERRY, MICHAEL JUDE
• Application Number:
  US09/375,884
• Time in Patent Office: 756 Days
• Field of Search: 361/18, 361/84, 361/86, 361/93.8, 361/93.9, 361/103, 361/104, 361/91.1, 361/91.5, 307/127, 307/130, 323/273-276, 323/282-285
• US Class Current: 361/18
• CPC Class Codes: H02H 3/087 for dc applications
• CPC Class Codes: H02H 7/18 for batteries; for accumulators
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/00308 Overvoltage protection
• CPC Class Codes: H02J 7/14 for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries

Abstract

A voltage regulator protecting both the regulator and the electrical system. A flyback diode is protected by an autoprotected MOSFET in series with the flyback diode and controlling it by a drive circuit connected to the vehicle ignition switch. Protection against overcurrent is provided by a resettable fuse, having a thermal protection circuit, in series with the power switch. A relay is in series with the resettable fuse. The controlled switch is controlled by the output of a voltage detector. A latching circuit holds it open as long as the circuit remains connected to the battery. Overvoltage protection is provided by a voltage detector which opens the relay if the battery voltage exceeds a pre-selected voltage. To accommodate lead-acid and maintenance-free batteries, the regulator has two input ignition terminals one of which controls the set point voltage. The resettable fuse is physically mounted in thermal connection to the power switch which switches the field.

Claims

1. A flyback diode protection circuit for a battery voltage regulator, the regulator having (i) a controlled power switch in series in a circuit branch between a battery terminal and a field coil terminal for, at times, applying battery voltage to the field coil, (ii) a voltage regulating circuit having a battery voltage detection circuit connected between a battery terminal and a ground terminal and a power switch control circuit connected to the voltage detecting circuit for turning the power switch off when the battery voltage exceeds a set value and turning the power switch on when the battery voltage is less than a set value, and (iii) a flyback diode connected in series in a circuit branch between the field coil terminal and the ground terminal for conducting field coil current when the controlled power switch is open, wherein the improvement comprises:

a) a power transistor interposed in series in the diode circuit branch for protecting the diode and having a control input; and

b) a power transistor drive circuit having an output connected to the control input of the power transistor and an input connected to a regulator ignition terminal, the regulator ignition terminal being for electrical connection to an ignition terminal of a vehicle ignition switch for turning on the power transistor when a voltage is present at the ignition terminal of the vehicle ignition switch and for turning the power transistor off when a voltage is not present.

2. A protection circuit in accordance with claim 1, wherein the power transistor is a power, MOSFET transistor and the control input is a gate terminal of the power MOSFET transistor.

3. A protection circuit in accordance with claim 2 wherein the MOSFET transistor is an autoprotected power MOSFET integrated circuit having temperature and overcurrent protection circuits.

4. A protection circuit in accordance with claim 1 or 2 or 3 wherein the regulator further has a second regulator ignition terminal also connected to the input of said power transistor drive circuit, the first and second regulator ignition terminals being for alternative connection of a selected one of the regulator ignition terminals to an ignition terminal of a vehicle ignition switch, one regulator ignition terminal connected for a battery of a first type and the other regulator ignition terminal connected for a battery of a second type.

5. A protection circuit in accordance with claim 4 wherein the power transistor drive circuit includes a bipolar transistor having input bias resistors and an output connected to the control input of the power transistor for isolating the power transistor from the regulating circuit.

6. An overcurrent protection circuit for a battery voltage regulator having (i) a controlled power switch in series in a circuit branch between a battery terminal and a field coil terminal for, at times, applying battery voltage to the field coil, (ii) a regulating circuit having a battery voltage detection circuit connected between a battery terminal and a ground terminal and a power switch control circuit connected to the voltage detecting circuit for turning the power switch off when the battery voltage exceeds a set value and turning the power switch on when the battery voltage is less than a set value, and (iii) a diode connected in series in a circuit branch between the field coil terminal and the ground terminal for conducting field coil current when the power switch is opened, wherein the protection circuit comprises:

a) a resettable fuse including thermal protection for opening the fuse in response to heating above a selected temperature and closing the fuse when the fuse temperature falls below a selected temperature, the resettable fuse being interposed in series in the controlled power switch circuit branch between the battery terminal and the field coil terminal;

b) a controlled switch having a control input and having switched terminals connected in series with the resettable fuse and interposed in series in the controlled power switch circuit branch between the battery terminal and the field terminal; and

c) a voltage detector having an input terminal connected between the field coil terminal and the series combination of (i) the resettable fuse and (ii) the controlled power switch, the voltage detector having an output connected to the control input of the controlled switch for opening the controlled switch when the resettable fuse is opened.

7. A protection circuit in accordance with claim 6 further comprising a latching circuit connected to the controlled switch for holding the controlled switch open after the controlled switch has been opened.

8. A protection circuit in accordance with claim 7 wherein the controlled switch comprises normally closed terminals of a relay and wherein the latching circuit includes a pair of normally open terminals on the relay connected in series between the battery terminal an actuating coil of the relay.

9. A protection circuit in accordance with claim 7 and further comprising a resettable overvoltage protection circuit having a voltage detector including a voltage reference circuit having a reference voltage, the voltage detector having an input terminal connected between the battery terminal and the ground terminal for applying a voltage to the voltage reference circuit and having an output terminal connected to the control input of the controlled switch for opening the controlled switch when the applied voltage exceeds the reference voltage.

10. A protection circuit in accordance with claim 9 wherein the controlled switch is a relay having normally closed and normally open terminals and wherein the controlled switch includes the normally closed terminals and the latching circuit includes the normally open terminals connected in series between the battery terminal and an actuating coil of the relay.

11. A protection circuit in accordance with claim 10 wherein the voltage detector comprises a voltage divider circuit connected to a Zener shunt regulator.

12. A resettable overvoltage protection circuit for a battery voltage regulator having a (i) controlled power switch in series in a circuit branch between a battery terminal and a field coil terminal for, at times, applying battery voltage to the field coil, (ii) a regulating circuit having a battery voltage detection circuit connected between a battery terminal and a ground terminal and a power switch control circuit connected to the voltage detecting circuit for turning the power switch off when the battery voltage exceeds a set value and turning the power switch on when the battery voltage is less than a set value, and (iii) a diode connected in series in a circuit branch between the field coil terminal and the ground terminal for conducting field coil current when the power switch is opened, the protection circuit comprising:

a) a controlled switch having a control input and having switched terminals connected in series in the controlled power switch circuit branch between the battery terminal and the field terminal; and

b) a voltage detector including a voltage reference circuit having a reference voltage, the voltage detector having an input terminal connected between the battery terminal and the ground terminal for applying a voltage to the voltage reference circuit and having an output terminal connected to the control input of the controlled switch for opening the controlled switch when the applied voltage exceeds the reference voltage; and

c) a latching circuit connected to the controlled switch and to the battery terminal for holding the controlled switch open after the controlled switch is opened by the voltage detector.

13. A protection circuit in accordance with claim 12 wherein the controlled switch is a relay having normally closed and normally open terminals and wherein the controlled switch includes the normally closed terminals of a relay and the latching circuit includes the normally open terminals on the relay connected in series between the battery terminal an actuating coil of the relay.

14. A protection circuit in accordance with claim 13 wherein the voltage detector comprises a voltage divider circuit connected to a Zener shunt regulator.

15. An improved battery voltage regulator having a regulating circuit for maintaining a battery at a selected voltage, the regulating circuit including a component upon which the magnitude of the selected voltage is dependent, wherein the improvement is a battery voltage selection circuit comprising:

a) a pair of input ignition terminals for alternative electrical connection to an ignition terminal of a vehicle ignition switch, one ignition terminal for connection to a battery of a first type and one ignition terminal for connection to a battery of a second type;

b) a switch having a control input connected to a first one of the input ignition terminals, the switch connected to said component of the regulating circuit for switching the component into one of two alternatively selected states, one state being effective connection in the regulating circuit and the other state being effective disconnection from the regulating circuit, one state being selected when the first input ignition terminal is connected to the vehicle ignition switch and another state being selected when the first input ignition terminal is not connected to the vehicle ignition switch.

16. A regulator in accordance with claim 15 wherein said switch is a bipolar transistor switching circuit.

17. A regulator in accordance with claim 15 wherein said component of the regulating circuit is one of at least two resistances.

18. A regulator in accordance with claim 17 wherein said resistances are a part of a voltage divider circuit for sensing the battery voltage and said switch is connected parallel to said one of resistances.

19. A regulator in accordance with claim 18 wherein said switch is a bipolar transistor switching circuit.

20. A regulator in accordance with claim 19 wherein the regulating circuit includes a Zener shunt regulator having the voltage divider connected to the Zener shunt regulator'"'"'s reference input terminal.

22. A regulator in accordance with claim 20 wherein the resettable fuse is mounted in direct physical contact with the controlled power switch.

23. A regulator in accordance with claim 22 wherein the controlled power switch is a power MOSFET.

24. A regulator in accordance with claim 22 wherein the controlled power switch is mounted in a horizontal operable orientation on a printed circuit board and the resettable fuse is mounted above it.

21. An improved battery voltage regulator having a controlled power switch connected in series in a circuit branch between a first terminal for connection to a battery and a field coil terminal for, at times, applying battery voltage to the field coil, wherein the improvement comprises:

a resettable fuse including thermal protection for opening the fuse in response to heating above a selected temperature and closing the fuse when the fuse temperature falls below a selected temperature, the resettable fuse being interposed in series electrical connection in said circuit branch, the resettable fuse being physically mounted in thermal connection to the controlled power switch.