Thermal protection of controller for on-vehicle alternators

• US 20080067983A1
• Filed: 09/04/2007
• Published: 03/20/2008
• Est. Priority Date: 09/01/2006
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Okamoto, Nobuhito
• Granted Patent: US 7,847,525 B2
• Time in Patent Office: Days
• US Class Current: 322/28
• CPC Class Codes: H02H 5/044 using a semiconductor device to sense the temperature
• CPC Class Codes: H02H 7/1213 for DC-DC converters
• CPC Class Codes: H02J 7/14 for charging batteries from dynamo-electric generators driven at varying speed, e.g. on vehicle
• CPC Class Codes: H02P 29/60 Controlling or determining the temperature of the motor or of the drive H02P29/02 takes precedence
• CPC Class Codes: H02P 29/66 Controlling or determining the temperature of the rotor
• CPC Class Codes: H02P 9/10 Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
• CPC Class Codes: H02P 9/30 using semiconductor devices
• CPC Class Codes: H02P 9/48 Arrangements for obtaining a constant output value at varying speed of the generator, e.g. on vehicle H02P9/04 - H02P9/46 take precedence

Abstract

A thermal protecting circuit is provided for an alternator controller. The protecting circuit comprises a switching member switching on/off the alternator; a sensor sensing a temperature of the switching member; and a switching control circuit. This switching control circuit switches off the switching member when the temperature of the switching member exceeds a first predetermined temperature. This switching control circuit switches on the switching member when the temperature of the switching member is lower than a second predetermined temperature. The second predetermined temperature is set to be higher than the first predetermined temperature.

Claims

1. A thermal protecting circuit for an alternator controller comprising:

a switching member switching on/off the alternator;

a sensor sensing a temperature of the switching member; and

a switching control circuit switching off the switching member when the temperature of the switching member exceeds a first predetermined temperature, while switching on the switching member when the temperature of the switching member is lower than a second predetermined temperature, the second predetermined temperature being set to be higher than the first predetermined temperature.

2. A thermal protecting circuit of claim 1, further comprising a switching circuit comprising the switching member and a circular diode connected between an output terminal of the alternator and a terminal of the switching member,

wherein the sensor senses temperature of the switching circuit.

3. The thermal protection circuit of claim 1, wherein the second predetermined temperature is substantially equal to an upper limit of a temperature range within which the switching member is assured to be able to operate without malfunction.

4. The thermal protection circuit of claim 1, wherein the first and the second temperature are set so that the sensed temperature can be maintained by the thermal protection circuit between the first and the second temperature when an ambient temperature around the switching member and a heat generated by the switching member are an expected maximum temperature and an expected maximum heat, respectively.

5. The thermal protection circuit of claim 1, wherein the switching control circuit

substantially lowering an on-duty ratio of the switching member when the temperature of the switching member exceeds the first predetermined temperature,

while substantially raising an on-duty ratio of the switching member when the temperature of the switching member is lower than the second predetermined temperature.

6. The thermal protection circuit of claim 1, further comprising an excitation current control circuit, controlling an excitation current of the alternator, and comprising the switching member and the switching control circuit.

7. The thermal protection circuit of claim 6, wherein

the switching control circuit performs a feedback control so as to substantially lower the on-duty ratio when a battery voltage exceeds a predetermined voltage and substantially raise the on-duty ratio when the battery voltage is lower than the predetermined voltage,

the predetermined voltage being lowered when the sensed temperature exceeds the first temperature, while being raised when the sensed temperature lowers the second temperature.

8. The thermal protection circuit of claim 7, wherein the switching control circuit turns off the switching member when the switching member is turning off, while the switching control circuit turns on the switching member when the switching member is turning on.

9. The thermal protection circuit of claim 8, wherein the switching member is Pulse-Wave-Modulation (PWM) controlled.