Motor drive device with lock protection function

• US 8,274,249 B2
• Filed: 12/30/2010
• Issued: 09/25/2012
• Est. Priority Date: 04/12/2007
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: ROHM Co., Ltd.
• Inventors: Mishima, Tomofumi
• Primary Examiner(s): Ip, Paul
• Application Number:
  US12/981,627
• Publication Number:
  US 20110089878A1
• Time in Patent Office: 635 Days
• Field of Search: 318/254, 318/430, 318/434, 318/447, 318/472, 318/400.21, 361/30, 361/56
• US Class Current: 318/400.21
• CPC Class Codes: H02H 7/0858 by reversing, cycling or reducing the power supply to the motor
• CPC Class Codes: H02H 7/093 against increase beyond, or decrease below, a predetermined level of rotational speed centrifugal switches H01H35/10
• CPC Class Codes: H02P 29/032 Preventing damage to the motor, e.g. setting individual current limits for different drive conditions
• CPC Class Codes: H02P 6/14 Electronic commutators

Abstract

A cooling system is provided with a motor drive device, a fan motor, and a Hall element. The motor drive device includes a lock protection circuit and a lock controller. When a control signal instructing rotation of the fan motor that is to be driven instructs stoppage of the motor for a predetermined time-period or longer, the lock controller has the lock protection circuit inactive. At an occasion when the control signal has continued to instruct stoppage of the fan motor for a first time-period or longer, a standby controller starts time measurement, and after a further predetermined second time-period has elapsed, makes at least a part of the motor drive device transition to a standby mode.

Claims

1. A motor drive device comprising:

a control input terminal which receives a control signal instructing rotation of a fan motor that is to be driven;

an oscillator which has a predetermined oscillating frequency and generates a periodical signal of triangular form or sawtooth form;

a comparator which compares the periodical signal with the control signal so as to generate a pulse width modulation signal subjected to pulse width modulation according to a target rotational frequency of the fan motor;

a drive unit which controls energization of the fan motor, based on the pulse width modulation signal;

a lock protection circuit which stops energization of the fan motor, when rotation of the fan motor is stopped;

a lock controller which has the lock protection circuit inactive, in cases in which the pulse width modulation signal continues to instruct stoppage of the fan motor for at least a predetermined first time-period; and

a standby controller which starts time measurement at an occasion when the control signal has continued to instruct stoppage of the motor for at least the first time-period, and after a further predetermined second time-period has elapsed, stops at least part of the motor drive device, and makes the motor drive device transit to a standby mode,

wherein the first time-period is longer than the period of the pulse width modulation signal occurring when the pulse width modulation signal has a lower-limit frequency and shorter than a verification time-period necessary for the lock protection circuit to confirm that the fan motor has stopped.

2. A motor drive device according to claim 1, wherein

the standby controller, in the standby mode, stops a voltage source generating a reference voltage for the motor drive device.

3. A motor drive device according to claim 1, wherein

the standby controller, in the standby mode, stops supplying of voltage to a Hall element for detecting rotation of the motor.

4. A motor drive device according to claim 1, wherein

the standby controller, in the standby mode, fixes electrical potential of a control terminal of a transistor of an output stage connected to a coil of the motor, to turn the transistor fully OFF.

5. A motor drive device according to claim 1, wherein

the standby controller, at an occasion when the control signal instructs driving of the motor, resets from the standby mode to normal mode.

6. A motor drive device according to claim 1, wherein

the motor drive device is monolithically integrated on one semiconductor substrate.

7. A cooling system comprising:

a fan motor; and

the motor drive device according to claim 1, which drives, as the motor to be driven, the fan motor.

8. A motor drive device comprising:

a drive unit which controls energization of a motor that is to be driven, based on a duty ratio of a control signal instructing rotation of the fan motor and subjected to pulse width modulation according to a target rotational frequency;

a lock protection circuit which stops energization of the fan motor, when rotation of the fan motor is stopped;

a lock controller which has the lock protection circuit inactive, in cases in which the control signal continues to be placed at a level instructing stoppage of the fan motor for at least a predetermined first time-period, and

a standby controller which starts time measurement at an occasion when the control signal continues to be placed at a level instructing stoppage of the fan motor for at least a predetermined first time-period, and after a further predetermined second time-period has elapsed, stops at least part of the motor drive device, and makes the motor drive device transit to a standby mode,

wherein the first time-period is longer than the period of the control signal occurring when the control has a lower-limit frequency and shorter than a verification time-period necessary for the lock protection circuit to confirm that the fan motor has stopped.

9. A motor drive device according to claim 8, wherein

the standby controller, in the standby mode, stops a voltage source generating a reference voltage for the motor drive device.

10. A motor drive device according to claim 8, wherein

the standby controller, in the standby mode, stops supplying of voltage to a Hall element for detecting rotation of the motor.

11. A motor drive device according to claim 8, wherein

the standby controller, in the standby mode, fixes electrical potential of a control terminal of a transistor of an output stage connected to a coil of the motor, to turn the transistor fully OFF.

12. A motor drive device according to claim 8, wherein

the standby controller, at an occasion when the control signal instructs driving of the motor, resets from the standby mode to normal mode.

13. A motor drive device according to claim 8, wherein the motor drive device is monolithically integrated on one semiconductor substrate.

14. A cooling system comprising:

a fan motor; and

the motor drive device according to claim 8, which drives, as the motor to be driven, the fan motor.

15. A lock protection method of stopping energization of a fan motor to be driven, when rotation of the fan motor is stopped, comprising:

comparing a control signal instructing stoppage of the fan motor with a period signal of triangular form or sawtooth form of a predetermined oscillating frequency so as to generate a pulse width modulation signal subjected to pulse width modulation according to a target rotational frequency of the fan motor;

measuring a time-period for which the pulse width modulation signal continues to be placed at a level instructing stoppage of the fan motor;

releasing lock protection when the measured time-period exceeds a predetermined first time-period; and

starting time measurement at an occasion when the predetermined first time-period has elapsed, and after a further predetermined second time-period has elapsed, making at least part of the motor drive device transit to a standby mode,

wherein the first time-period is longer than the period of the pulse width modulation signal occurring when the pulse width modulation signal has a lower-limit frequency and shorter than a verification time-period necessary to confirm that the fan motor has stopped for lock protection.

16. A lock protection method of stopping energization of a fan motor to be driven, when rotation of the fan motor is stopped, comprising:

measuring a time-period for which a control signal instructing rotation of the fan motor and subjected to pulse width modulation according to a target rotational frequency continues to be placed at a level instructing stoppage of the fan motor;

releasing lock protection when the measured time-period exceeds a predetermined first time-period; and

starting time measurement at an occasion when the predetermined first time-period has elapsed, and after a further predetermined second time-period has elapsed,

making at least part of the motor drive device transit to a standby mode,

wherein the first time-period is longer than the period of the control signal occurring when the control signal has a lower-limit frequency and shorter than a verification time-period necessary to confirm that the fan motor has stopped for lock protection.