Method and circuit for controlling rotation speed of computer fan

• US 20090003806A1
• Filed: 12/11/2007
• Published: 01/01/2009
• Est. Priority Date: 06/29/2007
• Status: Active Grant

• Current Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Inventors: Wang, Wei, Zou, Hua, He, Feng-Long
• Granted Patent: US 7,756,402 B2
• Time in Patent Office: Days
• US Class Current: 388/811
• CPC Class Codes: F04D 27/004 by varying driving speed
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

An exemplary method for controlling rotation speed of a computer fan includes: judging the type of a fan by comparing two rotation speeds detected before and after changing a duty cycle of a PWM signal respectively; controlling the computer fan as a 4-pin fan the PWM signals if the rotation speeds are different; and controlling the computer fan as a 3-pin fan via voltage signals converted from the PWM signals if the rotation speeds are equal. And an exemplary circuit for controlling rotation speed of a computer fan is capable of controlling rotation speed of the 4-pin fan via PWM signals, and controlling rotation peed of the 3-pin fan via voltage signals converted from PWM signals.

Claims

1. A method for controlling rotation speed of a computer fan, comprising:

detecting a rotation speed of the fan;

changing duty cycle of a PWM signal;

detecting a rotation speed of the fan after the duty cycle of the PWM signal is changed;

comparing the two rotation speeds, if the rotation speeds are different, the fan is a first type computer fan whose rotation speed is controlled by PWM signals;

if the rotation speeds are equal, the fan is a second type fan whose rotation speed is controlled by voltage signals;

transmitting PWM signals to the fan if the fan is the first type computer fan, and converting the PWM signals to voltage signals and transmitting the voltage signals to the fan if the fan is the second type fan.

2. The method as claimed in claim 1, wherein the duty cycle of the PWM signal is cut in half in the step of changing duty cycle of the PWM signal.

3. The method as claimed in claim 2, wherein the rotation speed of the fan detected after changing the duty cycle of the PWM signal is half of the rotation speed of the fan detected before.

4. The method as claimed in claim 1, wherein the first type computer fan is a 4-pin fan, the second type computer fan is a 3-pin fan.

5. A circuit for controlling rotation speed of a computer fan comprising:

an electric switch having a first terminal to receive a first control signal, a second terminal to receive a second control signal, and a third terminal grounded via a first resistor and a capacitor in turn;

an amplifier comprising a positive input terminal grounded via a second resistor, a negative input terminal connected to a node between the first resistor and the capacitor and connected to a first power source via the first resistor, and an output terminal;

a transistor, the base of the transistor connected to the output terminal of the amplifier via a third resistor, the emitter of the transistor connected to a second power source, and the collector of the transistor connected to the positive input terminal of the amplifier via a fourth resistor, the transistor outputting a fan control signal via the collector thereof; and

an output port configured for the computer fan connecting thereto, the output port comprising two pins respectively receiving the second control signal and the fan control signal.

6. The circuit as claimed in claim 5, wherein the transistor is a PNP transistor.

7. The circuit as claimed in claim 5, wherein the second control signal is a PWM signal.

8. The circuit as claimed in claim 5, wherein the electric switch is turned off when the first control signal is at a low level, and turned on when the first control signal is at a high level.

9. The circuit as claimed in claim 8, wherein the electric switch is an NMOS transistor.

10. The circuit as claimed in claim 8, wherein the first control signal is generated by BIOS.