Method and apparatus for controlling a fan

• US 20030193307A1
• Filed: 04/10/2002
• Published: 10/16/2003
• Est. Priority Date: 04/10/2002
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Standard Microsystems Corporation (Microchip Technology Incorporated)
• Inventors: Burstein, Steven
• Granted Patent: US 7,075,261 B2
• Time in Patent Office: Days
• US Class Current: 318/473
• CPC Class Codes: F04D 27/008 Stop safety or alarm devices, e.g. stop-and-go control; Disposition of check-valves
• CPC Class Codes: H02P 1/04 Means for controlling progress of starting sequence in dependence upon time or upon current, speed, or other motor parameter
• CPC Class Codes: Y10S 388/911 Phase locked loop

Abstract

A method and apparatus for controlling a fan is disclosed. In one embodiment, a method for controlling a fan includes applying power to the fan at startup. The fan may be supplied a predetermined amount of current, which may break the inertia of the fan propeller and begin its rotation. As the propeller begins rotating, the speed at which it rotates may be monitored. The fan startup routine may continue until the fan reaches or exceeds a minimum fan speed threshold. Once the fan has at least reached the minimum speed, the amount of current supplied to the fan may be reduced such that the fan rotates at minimum speed, and an automatic fan control algorithm may begin executing. By reducing the current such that the fan operates at a minimum speed, the amount of audible noise generated by the fan during startup may be kept to a minimum level.

Claims

1. A method for controlling a fan, the method comprising:

applying power to the fan;

monitoring the speed of the fan; and

entering an automatic fan control mode responsive to the fan speed reaching or exceeding a minimum fan speed threshold.

2. The method as recited in claim 1, wherein said applying power includes supplying a maximum amount of current to the fan.

3. The method as recited in claim 2, wherein said entering and automatic fan control mode includes reducing the amount of current supplied to the fan.

4. The method as recited in claim 1, wherein said monitoring the speed of the fan includes measuring a time interval for a blade of the fan to make one complete revolution.

5. The method as recited in claim 4, wherein the automatic fan control mode is entered responsive to the time interval no longer exceeding a maximum allowable limit.

6. The method as recited as recited in claim 1 further including setting an interrupt status bit if said reaching or exceeding the minimum fan speed threshold exceeds a predetermined time limit.

7. The method as recited in claim 1, wherein said automatic fan control mode includes:

monitoring a temperature;

increasing the fan speed if the temperature exceeds a preset temperature threshold; and

shutting down the fan if the temperature falls below a minimum temperature threshold, wherein said shutting down the fan includes exiting the automatic control mode.

8. The method as recited in claim 7 further comprising monitoring the temperature subsequent to said shutting down the fan.

9. The method as recited in claim 8 further comprising repeating said applying power to the fan responsive to the temperature exceeding the minimum temperature threshold.

10. The method as recited in claim 7 further comprising reducing the fan speed if the temperature falls below the preset temperature threshold but exceeds the minimum temperature threshold.

11. The method as recited in claim 1, wherein said controlling the fan is performed by a fan control unit.

12. The method as recited in claim 10, wherein the fan control unit is implemented on an integrated circuit.

13. A fan control unit comprising:

a temperature monitor, wherein the temperature monitor is configured to monitor a temperature in a control zone;

a tachometer, wherein the tachometer is configured to determine a speed of a fan; and

a speed controller, wherein the speed controller is configured to, upon a startup of the fan, to allow a predetermined amount of current to be applied to the fan, and wherein the speed controller is further configured to reduce the amount of current applied to the fan responsive to the fan reaching or exceeding a minimum fan speed threshold.

14. The fan control unit as recited in claim 13, wherein the predetermined amount of current is a maximum rated current amount.

15. The fan control unit as recited in claim 13, wherein the tachometer is configured to determine the speed of the fan by measuring a time interval for a blade of the fan to make one complete revolution.

16. The fan control unit as recited in claim 15, wherein the fan control unit is configured to being operating in an automatic control mode responsive to the time interval no longer exceeding a maximum allowable limit.

17. The fan control unit as recited in claim 15, wherein, during the automatic fan control mode, the fan control unit is configured to:

monitor the temperature;

cause the speed of the fan to increase responsive to the temperature exceeding a predetermined temperature threshold; and

shut down the fan if the temperature falls below a minimum temperature threshold, wherein shutting down the fan includes exiting the automatic control mode.

18. The fan control unit as recited in claim 17 wherein the fan control unit is further configured to monitor the temperature after the fan has been shut down.

19. The fan control unit as recited in claim 18, wherein the fan control unit is configured to restart the fan responsive to the temperature exceeding the minimum temperature threshold.

20. The fan control unit as recited in claim 17, wherein the fan control unit is configured to reduce the speed of the fan responsive to the temperature falling below the predetermined temperature threshold but exceeding the minimum temperature threshold.

21. The fan control unit as recited in claim 13, wherein the fan control unit includes a status register configured to store an interrupt status bit.

22. The fan control unit as recited in claim 21, wherein the interrupt status bit is set responsive to an amount of time to reach the minimum fan speed threshold exceeds a predetermined time limit.

23. The fan control unit as recited in claim 13, wherein the fan control unit is implemented in an integrated circuit.