Fan speed control system

• US 20030234630A1
• Filed: 06/24/2002
• Published: 12/25/2003
• Est. Priority Date: 12/23/1999
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Inventors: Blake, John
• Granted Patent: US 7,483,270 B2
• Time in Patent Office: Days
• US Class Current: 318/471
• CPC Class Codes: F04D 27/004 by varying driving speed
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: H05K 7/20209 Thermal management, e.g. fan control
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A fan speed control system (200) for an electronic equipment enclosure comprises means for determining temperature (201, 202, 203, 210, 211) at a plurality of locations within the enclosure, means for determining operating parameters (201, 202, 203, 212) for the fan control system, means for setting operating speed (201) of at least one cooling fan, and means for exchanging information signals (205, 217, 218) relating to fan speed control system operation with an external controller. A method is also provided for controlling fan speed for an electronic equipment enclosure comprising the steps of determining temperature at a plurality of locations within the enclosure, determining operating parameters for the fan control system, setting operating speed of at least one cooling fan, and exchanging information signals relating to fan speed control system operation with an external controller.

Claims

1. A fan speed control system for an electronic equipment enclosure comprising:

means for determining temperature at a plurality of locations within the enclosure;

means for determining operating parameters for the fan control system;

means for setting operating speed of at least one cooling fan; and

means for exchanging information signals relating to fan speed control system operation with an external controller.

2. The fan speed control system of claim 1, wherein the means for determining temperature comprises:

a plurality of temperature sensors;

an analog multiplexer coupled to the temperature sensors;

an A/D converter coupled to the analog multiplexer; and

control logic that controls analog multiplexer channel selection and reads A/D converter output.

3. The fan speed control system of claim 1, wherein the means for determining operating parameters for the fan speed control system comprises:

a plurality of voltage divider networks;

an analog multiplexer coupled to the voltage divider networks;

an A/D converter coupled to the analog multiplexer; and

control logic that controls analog multiplexer channel selection and reads A/D converter output.

4. The fan speed control system of claim 3, wherein the voltage divider networks comprise resistive voltage divider networks.

5. The fan speed control system of claim 4, wherein the resistive voltage divider networks include a plurality of series-connected resistors disposed between a regulated supply voltage and ground potential.

6. The fan speed control system of claim 5, wherein resistor values are selected to produce one of a set of eight pre-determined voltages at each tap between two consecutive series-connected resistors.

7. The fan speed control system of claim 1, wherein the means for setting operating speed of at least one cooling fan comprises:

computing means associated with the control logic that computes pulse width modulation duty cycle for a fan control output signal based upon a linear interpolation of selected operating parameters.

8. The fan speed control system of claim 7, wherein the linear interpolation of selected operating parameters comprises:

determining a ratio between a measured operating temperature value and a predetermined range of operating temperature values; and

selecting a fan control output duty cycle by applying said ratio to a range of predetermined fan control output duty cycles.

9. The fan speed control system of claim 1, wherein the means for exchanging information signals comprises:

means for interconnecting data signal and clock signal information streams between the fan speed control system and the external controller to establish a serial communications bus; and

serial bus interface means for managing information signal interchange.

10. The fan speed control system of claim 9, wherein the means for interconnecting data signal and clock signal information streams comprises a dedicated data signal communication line and a dedicated clock signal communication line.

11. The fan speed control system of claim 9, wherein the serial bus interface means comprises:

means for determining a START condition on the serial communications bus;

means for converting serially transmitted data signals on the data signal communication line from the external controller into parallel data signals;

means for acknowledging receipt of the serially transmitted data signals from the external controller; and

means for serially transmitting requested data to the external controller from the fan speed control system.

12. The fan speed control system of claim 11, wherein the means for converting serially transmitted data signals comprises a shift register.

13. The fan speed control system of claim 11, wherein the means for determining a START condition on the serial communications bus comprises means for detecting a high-to-low logic transition on the data signal communication line while detecting a high logic state on the clock signal communication line.

22. The fan speed control system of claim 1, wherein the means for determining operating parameters for the fan speed control system comprises, at least in part:

means for exchanging information signals with the external controller, the information signals including at least a parameter value and a register address; and

means for storing the parameter value in the register designated by the register address.

23. The fan speed control system of claim 22, wherein the means for setting operating speed of at least one cooling comprises:

computing means associated with the control logic that computes pulse width modulation duty cycle for a fan control output signal based upon a linear interpolation of operating parameters derived from the information signals.

14. A method for controlling fan speed for an electronic equipment enclosure, the method comprising the steps of:

(a) determining temperature at a plurality of locations within the enclosure;

(b) determining operating parameters for the fan control system;

(c) setting operating speed of at least one cooling fan; and

(d) exchanging information signals relating to fan speed control system operation with an external controller.

15. The method in accordance with claim 14, wherein the step of setting operating speed further comprises the step of:

computing pulse width modulation duty cycle for a fan control output signal based upon a linear interpolation of selected operating parameters.

16. The method in accordance with claim 15, wherein the step of computing pulse width modulation duty cycle further comprises the steps of:

(a) determining a ratio between a measured operating temperature value and a predetermined range of operating temperature values; and

(b) selecting a fan control output duty cycle by applying said ratio to a range of predetermined fan control output duty cycles.

17. The method in accordance with claim 14 wherein the step of determining operating parameters comprises the step of:

storing a minimum control temperature value and a temperature increment value in predetermined storage registers; and

wherein the operating speed of the cooling fan speed is set to full speed for a predetermined time period; and

on determining the temperature,

if the operating temperature is less than the minimum temperature, the method comprises the step of stopping the cooling fan;

if the operating temperature is greater than a predetermined critical temperature, the method comprises the step of continuing to operate the cooling fan at full speed;

otherwise, the method comprises the step of computing a pulse width for a pulse-width modulated fan control output signal based upon measured temperature, minimum temperature, and temperature increment values; and

applying the pulse width modulated fan control output signal to the cooling fan to control its operating speed.

18. The method in accordance with claim 17, further comprising the step of, prior to the storage of the temperature increment value, determining the temperature increment value by reading an output voltage from an external voltage divider network.

19. The method in accordance with claim 17, further comprising the step of, prior to the storage of the minimum control temperature value, determining the minimum control temperature value by reading an output voltage from an external voltage divider network.

20. The method in accordance with claim 17, further comprising the steps of:

(a) determining a device address for the fan speed control system;

(b) monitoring serial data and clock information signals from an external controller;

(c) determining whether a START condition has occurred;

(d) comparing a received device address to the device address for the fan control system and determining if there is a match; and

(e) if a match occurs, acknowledging the received device address, and responding to further received data signals as required.

21. The method in accordance with claim 14 wherein the step of determining operating parameters comprises the step of:

storing a minimum control temperature value and a temperature range value in predetermined storage registers; and

wherein the operating speed of the cooling fan speed is set to full speed for a predetermined time period; and

on determining the temperature,

if the operating temperature is less than the minimum temperature, the method comprises the step of stopping the cooling fan;

if the operating temperature is greater than a predetermined critical temperature, the method comprises the step of continuing to operate the cooling fan at full speed;

otherwise, the method comprises the step of computing a pulse width for a pulse-width modulated fan control output signal based upon measured temperature, minimum temperature, and range values; and

applying the pulse width modulated fan control output signal to the cooling fan to control its operating speed.

24. A method for controlling fan speed for an electronic equipment enclosure, the method comprising the steps of:

(a) determining temperature at a plurality of locations within the enclosure;

(b) determining operating parameters for the fan control system, at least in part, by exchanging information signals relating to fan speed control system operation with an external controller; and

(c) setting operating speed of at least one cooling fan.

25. The method in accordance with claim 24, wherein the step (c) of setting operating speed of at least one cooling fan further comprises the steps of:

(d) determining whether operating mode is RANGE mode or STEP mode;

(e) if operating mode is STEP mode, computing a fan control output signal pulse width by determining a relationship between a temperature step system parameter and a range of permitted operating temperature values; and

if operating mode is RANGE mode, computing a fan control output signal pulse width by performing a linear interpolation over a range of output signal pulse widths based upon measured operating temperature.

26. The method in accordance with claim 25, wherein the step of determining whether operating mode is RANGE mode or STEP mode comprises determining logic state of a hard-wired control input signal.

27. A method for controlling cooling fan operating speed in an electronic equipment enclosure, the method comprising the steps of:

(a) setting the cooling fan speed to full speed for a predetermined time period;

(b) reading operating temperature information from a temperature sensor;

(c) computing a pulse width for a pulse-width modulated fan control output signal; and

(d) applying the pulse width modulated fan control output signal to the cooling fan to control its operating speed.

28. The method in accordance with claim 27, further comprising the step of:

before the step (a) of setting the cooling fan speed to full speed, determining system operating parameters, including minimum control temperature value and temperature increment value.

29. The method in accordance with claim 28, wherein the step of determining system operating parameters comprises, at least in part, measuring input voltages corresponding to values of selected operating parameters.

30. The method in accordance with claim 28, wherein the step of determining system operating parameters comprises, at least in part, receiving system operating parameters as part of information received over a communication interface.

31. The method in accordance with claim 27, wherein the step (c) of computing a pulse width for a pulse-width modulated fan control output signal further comprises the steps of:

(i) if the operating temperature is less than the minimum temperature, stopping the cooling fan;

(ii) if the operating temperature is greater than a predetermined critical temperature, continuing to operate the cooling fan at full speed;

(iii) otherwise, computing a pulse width for a pulse-width modulated fan control output signal based upon measured temperature, minimum temperature, and temperature increment values; and

(iv) applying the pulse width modulated fan control output signal to the cooling fan to control its operating speed.