CN100413205C - Driving circuit for controlling fan - Google Patents

Abstract

The drive circuit for controlling a fan comprises a magnetic pole position sensor for generating a magnetic pole position sensing signal; a first waveform generator for generating a first waveform according to the magnetic pole position sensing signal generated by the magnetic pole position sensor; a second waveform generator for generating a second waveform; a comparator circuit for comparing the first waveform with the second waveform to generate a third waveform; a control signal generator for generating a control signal according to the third waveform generated by the comparison circuit and an external signal; and a current generator for outputting current to the coil of the motor stator of the fan according to the magnetic pole position sensing signal generated by the magnetic pole position sensor and the control signal generated by the control signal generator.

Description

A drive circuit for controlling a fan

technical field

The invention relates to a drive circuit for controlling a fan, in particular to a drive circuit which can reduce high-frequency noise, protect the motor and prolong the service life of the fan.

Background technique

The computer system is one of the most important hardware foundations of the modern information society. As the computing speed of the computer system increases day by day, the heat energy generated by each circuit (especially the central processing unit) in the computer system under high-speed operation is also higher. It is necessary to effectively dissipate the heat energy in order to maintain the stable and continuous operation of the computer system. Therefore, in a computer system, it is unavoidable to arrange a plurality of cooling fans to reduce the temperature of devices such as a central processing unit and a display card. Although these cooling fans can effectively discharge the heat in the casing of the computer system to the outside of the casing, the noise produced by the cooling fans during operation is very annoying. In order to reduce the running noise of the cooling fan, the prior art provides a driving circuit for controlling the rotation speed of the cooling fan with Pulse Width Modulation (PWM) technology, which is used to control the rotation speed of the cooling fan according to the temperature.

Please refer to FIG. 1 , which is a schematic diagram of a driving circuit 10 of a conventional cooling fan. The driving circuit 10 drives the cooling fan with pulse width modulation technology, and includes a magnetic pole position sensor 100 , a timing controller 102 , a triangular wave generator 104 , a control signal generator 106 , and a driving stage 108 . The magnetic pole position sensor 100 can be a Hall sensor, which is used to sense the magnetic pole position of the motor rotor of the cooling fan, and transmit the sensing result to the timing controller 102 . The control signal generator 106 is used for generating the control signal V _PWMC according to the triangular wave signal V _TRI generated by the triangular wave generator 104 and an external signal V _PWM . The timing controller 102 sequentially outputs the control signal V _PWMC to the gates of the transistors V1P, V1N, V2P, and V2N of the driving stage 108 according to the magnetic pole position sensing signal output by the magnetic pole position sensor 100 . The driving stage 108 is a full-bridge driving circuit, which can output currents in different directions from the terminals O1 and O2 to the coil 110 of the motor stator by switching the on and off of the transistors V1P, V1N, V2P, and V2N. The silicon steel sheets wound by the coil 110 generate magnetic poles in different directions to drive the motor rotor to rotate.

For variable speed operation of the fan, the drive circuit 10 can adjust the duty cycle of the control signal V _PWMC through the signal V _PWM according to the temperature, so as to control the speed of the cooling fan. Please refer to FIG. 2 . FIG. 2 is a schematic waveform diagram of the signals V _TRI , V _PWM , and V _PWMC in FIG. 1 . It can be seen from FIG. 2 that the signal V _PWM can adjust the duty cycle of the control signal V _PWMC to control the output current time to control the fan speed. In addition, when the temperature inside the casing is too high, the driving circuit 10 can operate the cooling fan at full speed mode, that is, the current supplied to the coil 110 is a full waveform current; and when the temperature is low, the cooling fan can be operated at speed control mode. Please refer to FIG. 3 and FIG. 4 . FIG. 3 and FIG. 4 are schematic diagrams of signal waveforms of terminals O1 and O2 when the driving circuit 10 operates the cooling fan in the speed control mode and the full speed mode respectively. It can be seen from FIG. 3 that when operating in the speed control mode, the driving circuit 10 can adjust the duty cycles of the signals V _O1A and V _O2A of the terminals O1 and O2 to control the speed of the cooling fan. However, since the frequencies of the signals V _O1A and V _O2A are fixed, high-frequency noises are likely to be generated when the rotation speed of the cooling fan is changed. In addition, in FIG. 4, when the driving circuit 10 switches the speed of the cooling fan to the full speed mode, the signals V _O1B and V _O2B of the terminals O1 and O2 will generate pulses (Impulse), which will not only emit high-frequency electromagnetic sounds, but also It will cause damage to the driver IC and reduce the life of the fan.

Contents of the invention

Therefore, the main object of the present invention is to provide a driving circuit for controlling a fan.

The present invention discloses a driving circuit for controlling a fan, which includes: a magnetic pole position sensor, which is used to generate a magnetic pole position sensing signal according to a magnetic change of a motor rotor of the fan; a first waveform generator, electrically connected to the magnetic pole position sensor, used to generate a first waveform according to the magnetic pole position sensing signal generated by the magnetic pole position sensor; a second waveform generator, used to generate a second waveform; a comparison circuit, electrically connected to The first waveform generator and the second waveform generator are used to compare the first waveform and the second waveform to generate a third waveform; a control signal generator is electrically connected to the comparison circuit and the second waveform a generator, the control signal generator is used to generate a control signal to the current generator according to the second waveform generated by the second waveform generator, the third waveform generated by the comparison circuit, and the external signal; and a current generator A device, electrically connected to the magnetic pole position sensor and the control signal generator, is used to output current to the motor stator of the fan according to the magnetic pole position sensing signal generated by the magnetic pole position sensor and the control signal generated by the control signal generator coil.

Description of drawings

FIG. 1 is a schematic diagram of a driving circuit of a conventional cooling fan.

FIG. 2 is a schematic diagram of waveforms of related signals in FIG. 1 .

FIG. 3 is a schematic diagram of waveforms of related signals when the driving circuit of FIG. 1 operates the cooling fan in a speed control mode.

FIG. 4 is a schematic diagram of waveforms of related signals when the driving circuit of FIG. 1 operates the cooling fan in a full speed mode.

FIG. 5 is a schematic diagram of a driving circuit for controlling a fan according to a preferred embodiment of the present invention.

FIG. 6 is a schematic diagram of an adjustable gain amplifier of the present invention.

FIG. 7 is a schematic waveform diagram of the magnetic pole position sensing signal and the signal output by the first waveform generator in FIG. 5 .

FIG. 8 is a schematic diagram of waveforms of input and output signals of the comparison circuit when the driving circuit of FIG. 5 operates in the speed control mode.

FIG. 9 is a schematic waveform diagram of an output signal when the driving circuit of FIG. 5 operates in a speed control mode.

FIG. 10 is a schematic waveform diagram of an output signal when the driving circuit of FIG. 5 operates in a full speed mode.

Description of reference symbols

10, 50 Drive circuit

100, 500 Magnetic pole position sensor

102 Timing controller

104 Triangular wave generator

106 Control signal generator

108 driver stage

110 Coil

V1P, V1N, V2P, V2N Transistors

O1, O2, O1’, O2’ Endpoints

502 The first waveform generator

504 Second waveform generator

506 comparison circuit

508 Control Signal Generator

510 Current generator

512 timing controller

514 Adjustable gain driver stage

OP1, OP2 Operational Amplifiers

60 Adjustable gain amplifier

600 Coil

I _CL current

V _TRI , V _PWM , V _PWM , V _O1A , V _O2A , V _O1B , V _O2B , V _MAG , V _W1 , V _W2 , V _PWM , V _PWMC , V _{O1A , V O2A} , V _O1B , _{V O2B ,} V _GC , V ₁ , V ₂ , V ₃ , V ₄ , V _MS signal

Detailed ways

Please refer to FIG. 5 , which is a schematic diagram of a driving circuit 50 for controlling a fan according to a preferred embodiment of the present invention. The driving circuit 50 includes a magnetic pole position sensor 500 , a first waveform generator 502 , a second waveform generator 504 , a comparison circuit 506 , a control signal generator 508 , and a current generator 510 . The magnetic pole position sensor 500 can generate a magnetic pole position sensing signal V _MAG according to the magnetic variation of the motor rotor of the fan. The first waveform generator 502 can output the signal V _W1 to the comparison circuit 506 according to the magnetic pole position sensing signal V _MAG generated by the magnetic pole position sensor 500 , and the second waveform generator 504 can generate a signal V _W2 to the comparison circuit 506 and a control signal Generator 508 . Wherein, the signal V _W1 and the signal V _W2 are preferably trapezoidal waves and triangular waves respectively, and the period of the signal V _W2 is much smaller than the period of the signal V _W1 . The comparison circuit 506 is used for comparing the signal V _W1 and the signal V _W2 , and outputs the modulation signal V _MS to the control signal generator 508 , and the control signal generator 508 can generate the control signal V _PWMC accordingly. The control signal V _PWMC' is controlled by an external signal V _PWM' , and its duty cycle is related to the voltage level of the external signal V _PWM . The current generator 510 includes a timing controller 512 and an adjustable-gain driver stage 514 for outputting current according to the magnetic pole position sensing signal V _MAG generated by the magnetic pole position sensor 500 and the control signal V _PWMC generated by the control signal generator 508 Coils to the motor stator of the fan.

Please continue to refer to FIG. 6 , which is a schematic diagram of an adjustable gain amplifier 60 . The adjustable gain amplifier 60 is used to implement the adjustable gain driving stage 514 in FIG. 5 , which can output current to the coil 600 of the motor stator of the fan through the terminals O1 ′ and O2 ′. The adjustable gain amplifier 60 includes operational amplifiers OP1 and OP2 , and the gains of the operational amplifiers OP1 and OP2 are changed according to the control signal V _GC generated by the control signal generator 508 . When the driving circuit 50 operates in the full speed mode, the gains of the operational amplifiers OP1 and OP2 are low, and when the driving circuit 50 operates in the speed control mode, the gains of the operational amplifiers OP1 and OP2 are high. Therefore, through the signals V1, V2, V3, and V4 output by the timing controller 512, the adjustable gain amplifier 60 can output currents in different directions from the terminals O1', O2' to the coil 600 of the motor stator, so that through electromagnetic induction, the coil 600 The wound silicon steel sheets produce magnetic poles in different directions to drive the motor rotor to rotate.

For the waveform changes of related signals in FIG. 5 and FIG. 6 , please refer to FIG. 7 to FIG. 10 . 7 is a schematic diagram of the waveforms of the magnetic pole position sensing signal V _MAG and the signal V _W1 output by the first waveform generator 502; FIG. 8 is the input and output signals (V _W1 , V _W2 , V _MS ) waveform schematic diagram; Figure 9 is a schematic waveform diagram of the signals V _O1A and V _O2A of the terminals O1', O2' when operating in the speed control mode; Figure 10 is a schematic diagram of the waveforms of the terminals O1', O2' when operating in the full speed mode Schematic diagram of waveforms of signals V _O1B and V _O2B' of O2'. It can be seen from FIG. 8 and FIG. 9 that the duty cycle of the modulation signal V _MS output by the comparison circuit 506 is not fixed, and it changes with the relationship between the signal V _W1 and the signal V _W2 , so that the current transmitted to the coil 600 of the motor stator I _CL tends to change linearly, so it can reduce the high-frequency noise in the speed control mode. In addition, it can be seen from FIG. 10 that when the driving circuit 50 operates in the full speed mode, the gain of the operational amplifiers OP1 and OP2 of the adjustable gain amplifier 60 will be reduced, so that the signals at the terminals O1' and O2' will not generate pulses (Impulse) environment, thus reducing noise and protecting the motor for longer life.

To sum up, when operating in the speed control mode, the duty cycle of the modulation signal V _MS output by the comparison circuit 506 is not fixed, but changes with the relationship between the signal V _W1 and the signal V _W2 . Therefore, when operating in the speed control mode, the current I _CL transmitted to the motor stator tends to change linearly, thereby reducing the high frequency noise in the speed control mode. In addition, when operating in the full speed mode, the present invention reduces the gain of the operational amplifiers OP1 and OP2, so that the signal output to the coil of the motor stator does not generate pulses (Impulse), so it can reduce noise and protect the motor, prolonging the service life . It should be noted that the driving circuit 50 in FIG. 5 is used for illustration to control the speed of the fan, and those skilled in the art can make various possible changes without departing from the scope of the present invention.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the claims of the present invention shall fall within the scope of the present invention.

Claims (5)

1. drive circuit that is used for controlling a fan includes:

One magnetic pole position sensor is used for changing according to the magnetic of a motor rotor of this fan, produces position of magnetic pole sensing signal;

One first waveform generator is electrically connected in this magnetic pole position sensor, is used for the position of magnetic pole sensing signal that produces according to this magnetic pole position sensor, produces one first waveform;

One second waveform generator is used for producing one second waveform;

One comparison circuit is electrically connected in this first waveform generator and this second waveform generator, is used for relatively this first waveform and this second waveform to produce one the 3rd waveform;

One controlling signal generator, be electrically connected in this comparison circuit and this second waveform generator, second waveform that this controlling signal generator is used for being produced according to this second waveform generator, the 3rd waveform that this comparison circuit produces, and an outside signal produce controlling signal; And

One current generator, be electrically connected in this magnetic pole position sensor and this controlling signal generator, be used for outputing current to the coil of the motor stator of this fan according to the position of magnetic pole sensing signal of this magnetic pole position sensor generation and the controlling signal of this controlling signal generator generation.

2. drive circuit as claimed in claim 1, wherein this current generator includes:

One driving stage is electrically connected in the coil of the motor stator of this fan, is used for output current; And

Time schedule controller, be electrically connected in this magnetic pole position sensor, this controlling signal generator, reach this driving stage, be used for cycle of the position of magnetic pole sensing signal that produces according to this magnetic pole position sensor, the controlling signal that this controlling signal generator is produced is sent to this driving stage.

3. drive circuit as claimed in claim 2, wherein this driving stage is a full bridge driving circuit.

4. drive circuit as claimed in claim 1, wherein this current generator includes:

One driving stage, include one first operational amplifier and one second operational amplifier, be electrically connected in the two ends of coil of the motor stator of this fan, be used for output current, the gain of this first operational amplifier and this second operational amplifier can change according to the controlling signal that this controlling signal generator produces; And

Time schedule controller, be electrically connected in this magnetic pole position sensor, this controlling signal generator, reach this driving stage, be used for cycle of the position of magnetic pole sensing signal that produces according to this magnetic pole position sensor, the controlling signal that this controlling signal generator is produced is sent to this first operational amplifier and this second operational amplifier in regular turn.

5. drive circuit as claimed in claim 4, the gain of this first operational amplifier and this second operational amplifier when wherein the gain of this first operational amplifier and this second operational amplifier is less than the non-full-speed operation of this fan during this fan full-speed operation.

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