System and method of controlling cooling fan speeds

• US 6,801,004 B2
• Filed: 06/20/2002
• Issued: 10/05/2004
• Est. Priority Date: 06/20/2002
• Status: Expired due to Term

• Current Assignee: Minebea Mitsumi, Inc.
• Original Assignee: Minebea Company Limited (MinebeaMitsumi Inc.)
• Inventors: Frankel, Scott, Hardt, Eric
• Primary Examiner(s): Masih, Karen
• Application Number:
  US10/175,654
• Publication Number:
  US 20030234624A1
• Time in Patent Office: 838 Days
• Field of Search: 318/809, 318/729, 318/786, 318/778, 318/549, 318/138, 318/254, 318/439, 318/810
• US Class Current: 318/268
• CPC Class Codes: G06F 1/206 comprising thermal management
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence

Abstract

A cooling fan includes a fan, a motor a motor coupled to the fan to drive the fan and a microcontroller. The microcontroller is connected to the motor and is capable of detecting a speed of the fan in real time and maintaining a constant speed of the fan regardless of changes in input voltage.

Claims

1. A cooling fan, comprising:

a fan;

a motor coupled to the fan to drive the fan;

a speed sensor to magnetically monitor a fan speed; and

a microcontroller, coupled to the motor and to the speed sensor, to receive the fan speed from the speed sensor, and to control a duty cycle of a stator signal based on the fan speed, wherein the stator signal provides an energy transfer to the motor.

2. The cooling fan accordingly to claim 1, wherein the microcontroller terminates a transmission of a stator signal to the motor if a current flowing through motor windings is above a threshold.

3. The cooling fan according to claim 1, wherein if the speed sensor detects an increase in the fan speed, the microcontroller reduces the duty cycle of the stator signal.

4. The cooling fan according to claim 1, wherein the speed sensor is a Hall sensor.

5. The cooling fan according to claim 1, wherein the microcontroller maintains a desired fan speed of the fan regardless of changes in motor load.

6. A method of operating a cooling fan, comprising:

driving a fan by a motor;

magnetically monitoring a fan speed;

transmitting the fan speed to a microcontroller; and

adjusting a duty cycle of a stator signal to maintain controlled speed of the fan.

7. The method according to claim 6, wherein adjusting the duty cycle of the stator signal reduces the duty cycle to maintain a desired speed of the fan if the fan speed is greater than the desired fan speed.

8. The method according to claim 6, wherein the magnetic monitoring of the fan speed is performed by a Hall sensor.

9. The method according to claim 6, further including maintaining the a desired speed of the fan regardless of changes in motor load.

10. The method of claim 6, further including terminating transmission of a stator signal from the microcontroller to the motor if a current measurement in windings of the motor is above a threshold.

11. A cooling fan, comprising:

a fan;

a motor coupled to the fan to drive the fan;

a speed sensor to detect a fan speed;

a microcontroller, coupled to the speed sensor, to receive the fan speed from the speed sensor, and to transmit a driving signal having a duty cycle based on the fan speed;

a driving circuit, connected to the microcontroller and to the motor, to receive the driving signal and to transmit a motor driving signal to the motor to drive the fan,

wherein the speed sensor is electrically independent of the driving circuit the motor.

12. The cooling fan according to claim 11, wherein if the speed sensor detects an increase in fan speed, the microcontroller reduces the duty cycle of the driving signal which is transmitted to the driving circuit.

13. The cooling fan according to claim 11, wherein the speed sensor is a Hall sensor.

14. The cooling fan according to claim 11, wherein the microcontroller terminates transmission of the driving signal to the driving circuit if a current flowing through motor windings is above a threshold.

15. A method of driving a cooling fan, comprising:

driving a fan with a motor;

sensing a fan speed by a speed sensor which is electrically independent of both the motor and a driving circuit;

receiving the sensed fan speed at a microcontroller;

adjusting a duty cycle of a driving signal and transmitting the driving signal to a driving circuit; and

receiving the driving signal at the driving circuit and transmitting a motor driving signal to the motor.

16. The method of claim 15, wherein adjusting the duty cycle is reducing the duty cycle of the driving signal to maintain a desired fan speed of the fan if the sensed fan speed is greater than the desired fan speed.

17. The method of claim 15, wherein the sensing of the fan speed is performed by a Hall sensor.

18. The method of claim 15, further including maintaining a desired fan speed regardless of changes in motor load.

19. The method of claim 15, further including terminating the transmission of the driving signal to the driving circuit, by the microcontroller, if a current flowing through windings of the motor is above a threshold.

20. A cooling fan comprising:

a fan;

a motor coupled to the fan to drive the fan, wherein a current through a stator drives the motor;

a speed sensor to magnetically monitor a fan speed;

a microcontroller, connected to the speed sensor, to receive the fan speed from the speed sensor, transmit a first driving signal having a first duty cycle based on the fan speed; and

to transmit a second driving signal having a second duty cycle based on the fan speed;

a first driving circuit, connected to the microcontroller, to receive the first driving signal and to transmit a first motor driving signal;

a second driving circuit, connected to the microcontroller, to receive the second driving signal and to transmit a second motor driving signal;

a first field effect transistor (FET) and a third FET to receive the first motor driving signal and to transmit the current through the stator to drive the motor; and

a second FET and a fourth FET to receive the second motor driving signal and to transmit the current through the stator to drive the motor.

21. The cooling fan of claim 20, wherein if the speed sensor detects on increase in the fan speed, the microcontroller reduces the first duty cycle of the first driving signal and reduces the second duty cycle of the second driving signal to maintain a desired speed of the fan.

22. The cooling fan according to claim 20, wherein the speed sensor is a Hall sensor.

23. The cooling fan according to claim 20, wherein the microcontroller is further capable of maintaining a desired fan speed of the fan regardless of changes in motor load.

24. The cooling fan according to claim 20, wherein the microcontroller terminates transmission of the first driving signal and the second driving signal if a current measurement for windings of the motor is above a threshold value.

25. A method of driving a cooling fan, including:

coupling a motor to a fan, wherein the motor drives the fan;

magnetically sensing a fan speed by a speed sensor;

receiving the fan speed at a microcontroller;

adjusting a first duty cycle of a first driving signal based on the fan speed and transmitting the first driving signal to a first driving circuit;

adjusting a second duty cycle of a second driving signal based on the fan speed and transmitting the second driving signal to a second driving circuit;

receiving the first driving signal at the first driving circuit and transmitting a first motor driving signal to the motor; and

receiving the second driving signal at the second driving circuit and transmitting a second motor driving signal to the motor.

26. The method of claim 25, adjusting the first duty cycle and the second duty cycle is reducing the first duty cycle and reducing the second duty cycle to maintain a desired fan speed of the cooling fan if the fan speed is greater than the desired fan speed.

27. The method of claim 25, wherein the magnetic monitoring of the fan speed is performed by a Hall sensor.

28. The method of claim 25, further including maintaining the desired fan speed regardless of changes in a load of the motor.

29. The method of claim 25, further including terminating the transmission of the first driving signal and the second driving signal, by the microcontroller, to the first driving circuit and the second driving circuit if a current flowing through windings of the motor is above a certain threshold.