Fan speed control system

• US 6,188,189 B1
• Filed: 12/23/1999
• Issued: 02/13/2001
• Est. Priority Date: 12/23/1999
• Status: Expired due to Term

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Analog Devices, Inc.
• Inventors: Blake, John
• Primary Examiner(s): Ro, Bentsu
• Application Number:
  US09/470,800
• Time in Patent Office: 418 Days
• Field of Search: 318/34, 318/268, 318/272, 318/471, 318/472, 318/473, 388/934
• 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 for an electronic equipment enclosure comprises 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. 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.

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

a plurality of temperature sensors;

a plurality of voltage divider networks;

wherein the temperature sensors and voltage divider networks provide operating parameters to the fan speed control system;

an analog multiplexer coupled to the temperature sensors and the voltage divider networks;

an A/D converter coupled to the analog multiplexer;

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

an arithmetic logic unit 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 ones of the operating parameters; and

a serial bus interface that provides an interconnection over data signal and clock signal lines between the fan speed control system and an external controller.

15. The fan speed control system of claim 14, 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.

16. The fan speed control system of claim 14, wherein the serial bus interface comprises:

monitoring logic that detects a START condition on the serial communications bus;

a shift register that converts serially transmitted data signals on the data signal communication line from the external controller into parallel data signals;

a logic circuit that acknowledges receipt of the serially transmitted data signals from the external controller; and

a logic element that operates in conjunction with the control logic to serially transmit requested data to the external controller from the fan speed control system.

17. 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.

18. The method in accordance with claim 17, 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.

19. The method in accordance with claim 18, 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.

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

(a) measuring a minimum control temperature value;

(b) determining a temperature increment value;

(c) storing the minimum control temperature value and the temperature increment value in predetermined storage registers;

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

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

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

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

(h) 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

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

21. The method in accordance with claim 20, wherein the step of determining a temperature increment value comprises reading the temperature increment value from a predetermined one of the storage registers.

22. The method in accordance with claim 20, wherein the step of determining a temperature increment value comprises reading an output voltage from an external voltage divider network.

23. The method in accordance with claim 20, 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.