Thermal protection of controller for on-vehicle alternators

• US 7,847,525 B2
• Filed: 09/04/2007
• Issued: 12/07/2010
• Est. Priority Date: 09/01/2006
• Status: Expired due to Fees

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Okamoto, Nobuhito
• Primary Examiner(s): GONZALEZ, JULIO CESAR
• Application Number:
  US11/896,575
• Publication Number:
  US 20080067983A1
• Time in Patent Office: 1,190 Days
• Field of Search: 322/33, 322/25, 322/19, 322/28, 322/24, 322/44
• US Class Current: 322/33
• 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 a controller of an alternator, the thermal protecting circuit comprising:

a switching member for controlling an amount of power to be applied to the alternator according to an on-duty ratio of the switching member;

a sensor sensing a temperature of the switching member; and

a control circuit configured to;

reduce the on-duty ratio of the switching member when the temperature of the switching member sensed by the sensor is changed from a first temperature range to a second temperature range that is higher than the first temperature range; and

further lower the reduced on-duty ratio of the switching member when the temperature of the switching member sensed by the sensor is changed from the second temperature range to a third temperature range that is higher than the second temperature range.

2. The 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 a temperature of the switching circuit as the temperature of the switching member.

3. The thermal protecting circuit of claim 1, wherein the first temperature range and the second temperature range are contiguous to each other via a first predetermined temperature, the second temperature range and the third temperature range are contiguous to each other via a second predetermined temperature, and the second predetermined temperature is substantially equal to an upper limit of the second temperature range within which the switching member is able to operate without malfunction.

4. The thermal protecting circuit of claim 1, wherein a first predetermined temperature and a second predetermined temperature are each set so that the temperature of the switching member sensed by the sensor is maintained by the thermal protecting circuit between the first and second predetermined temperatures 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 protecting circuit of claim 1, wherein

the first temperature range and the second temperature range are contiguous to each other via a first predetermined temperature, the second temperature range and the third temperature range are contiguous to each other via a second predetermined temperature, and

the control circuit is further configured to:

substantially lower the on-duty ratio of the switching member when the temperature of the switching circuit sensed by the sensor exceeds the first predetermined temperature, and

substantially raise the on-duty ratio of the switching member when the temperature of the switching circuit sensed by the sensor is lower than the second predetermined temperature.

6. The thermal protecting circuit of claim 1, further comprising an excitation current control circuit that controls an excitation current of the alternator.

7. The thermal protecting circuit of claim 6, wherein

the first temperature range and the second temperature range are contiguous to each other via a first predetermined temperature, the second temperature range and the third temperature range are contiguous to each other via a second predetermined temperature,

the control circuit performs a feedback control when the temperature of the switching member sensed by the sensor is within the second temperature range 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, and the predetermined voltage being lowered when the temperature of the switching member sensed by the sensor exceeds the first predetermined temperature, while also raising the predetermined voltage when the temperature of the switching member sensed by the sensor is lower than the second predetermined temperature.

8. The thermal protecting circuit of claim 7, wherein the control circuit turns off the switching member based on the on-duty ratio of the switching member to thereby perform thermal protection of the switching member while the control circuit turns on the switching member based on the on-duty ratio of the switching member to thereby release the thermal protection of the switching member.

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