TWI426700B - Control circuit for fan - Google Patents

Description

Fan control circuit

The present invention relates to a fan control circuit.

With the continuous development of electronic technology, hard disk drives have become an important part of products such as computers. The design direction is mainly toward increasing the accessible capacity and access speed, but the hard disk is made with increasing access speed. The heat generated by the machine during access operation is greatly increased. It is necessary to use a fan and control the fan to lower its temperature. At present, the way to control the fan is to let the fan work all the time, or according to the detected temperature. Control whether the fan works, sometimes to save power and reduce noise, but also add a controller to control the fan, but this way of controlling the fan needs to increase the control of the software and the controller, making the control work complicated and costly .

In view of the above, it is necessary to provide a fan control circuit that is simple in structure and low in cost.

A fan control circuit for controlling a fan to dissipate heat to an electronic device, comprising: a comparator and an electric switch, wherein the non-inverting input end of the comparator receives the working current of the electronic device and is connected to the first power source through the first resistor, and the same The input end is connected to the power supply through a second resistor and is grounded through a third resistor. The first end of the electrical switch is connected to the output end of the comparator, the second end is grounded, and the third end is connected to the second power source through the fourth resistor. The fan is connected between the second and third ends of the electric switch, and the comparator compares the voltage at the non-inverting input end with the voltage at the inverting input end thereof, and outputs a control signal to control the closing and closing of the electric switch. Turning on to control the fan to operate when the electronic device is in an operational state and to stop working when the electronic device is in a standby state.

The fan control circuit utilizes the current of the hard disk drive to control the voltage at the non-inverting input end of the comparator, compares the voltage of the non-inverting input end of the comparator with the inverting input end thereof, and outputs a control signal to control the switch of the electric switch. The fan is controlled to operate when the electronic device is in an operating state and is stopped when in the standby state. The fan control circuit of the present invention has a simpler structure and lower cost than the prior art, and also has the effects of saving electric energy, reducing noise, and simplifying control work.

Referring to FIG. 1, the fan control circuit of the present invention is used to control the fan 20 to dissipate heat to an electronic device (such as the hard disk drive 10). The preferred embodiment includes a comparator U1 and an electrical switch Q1. The non-inverting input of the comparator U1. The hard disk drive 10 is connected to the 12V power supply through the resistor R1, and the inverting input terminal is connected to the 12V power supply through the resistor R2 and grounded through the resistor R3. The power supply terminal of the comparator U1 is connected to the 12V power supply, and the ground terminal is grounded. The first end of the electric switch Q1 is connected to the output end of the comparator U1, the second end thereof is grounded, the third end is connected to the 12V power supply through the resistor R4, and the resistor R5 is connected to the first end of the electric switch Q1 and the 12V power supply. The fan 20 is connected in parallel with the capacitor C1 and connected between the second end and the third end of the electric switch Q1. The capacitor C2 is connected between the 12V power source and the ground.

In the preferred embodiment, the electrical switch Q1 is an NPN transistor, and the first, second, and third ends are respectively a base, an emitter, and a collector; and the resistors R1, R2, and R3 are voltage dividing resistors. The two resistors R4 and R5 are pull-up resistors; The two capacitors C1 and C2 both generate a voltage stabilizing effect and can be omitted; the 12V power supply provides an operating voltage for the entire circuit. In addition, the power supplies connected to the two resistors R2 and R4 may also be different.

The working state of the hard disk drive 10 is divided into five states, namely, start, no load, operation, pause, and sleep state; the working current value of the hard disk drive 10 in the five states is described in the specifications of the hard disk drive. The start, idle, and operational states are operational states, and the pause and sleep states are standby states. The operating current value of the hard disk drive 10 in the operating state is greater than the current value of the hard disk drive 10 in the standby state. If the operating current value of the hard disk drive 10 is I, and the resistance value of the resistor R1 is R, the voltage value of the non-inverting input terminal of the comparator U1 is V=12V-I×R, so the hard disk drive 10 The operating current and the operating current in the standby state can be obtained from the voltage value of the non-inverting input terminal of the comparator U1. It can be seen that the voltage value of the non-inverting input terminal of the comparator U1 in the operating state of the hard disk drive 10 is smaller than that in the hard state. The voltage value of the disc drive 10 in the standby state, according to the above situation, the reference voltage can be set at the inverting input end of the comparator U1, such that the value is greater than the non-inverting input end of the comparator U1 in the operating state of the hard disk drive 10 The voltage value is lower than the voltage value of the hard disk drive 10 in the standby state (the resistance value of the two resistors R2 and R3 can be adjusted to satisfy the voltage value required by the reference voltage).

When the hard disk drive 10 is in operation, if the voltage value of the non-inverting input terminal of the comparator U1 is greater than the reference voltage value of the inverting input terminal of the comparator U1, the hard disk drive 10 operates in a standby state, and the comparator U1 The output terminal outputs a high level, the electric switch Q1 is turned on, the fan 20 is grounded at both ends, and the fan 20 stops working.

If the voltage value at the non-inverting input of the comparator U1 is less than the reference voltage value of the inverting input terminal of the comparator U1, the hard disk drive 10 operates in the operating state, and the output of the comparator U1 is low. Level, the electrical switch Q1 is turned off, and the fan 20 receives the voltage supplied by the 12V power supply.

In a preferred embodiment of the present invention, the user can set different values for the reference voltage according to the needs thereof, and the fan control circuit utilizes the current of the hard disk drive 10 to determine the state of its operation to control the state of the fan 20, thereby It saves power, reduces noise and makes control work easier.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

U1‧‧‧ comparator

Q1‧‧‧Electric switch

10‧‧‧ Hard disk drive

20‧‧‧Fan

C1, C2‧‧‧ capacitor

R1, R2, R3, R4, R5‧‧‧ resistors

1 is a circuit diagram of a preferred embodiment of a fan control circuit of the present invention.

U1‧‧‧ comparator

Q1‧‧‧Electric switch

10‧‧‧ Hard disk drive

20‧‧‧Fan

C1, C2‧‧‧ capacitor

R1, R2, R3, R4, R5‧‧‧ resistors

Claims (7)

A fan control circuit for controlling a fan to dissipate heat to an electronic device, comprising: a comparator and an electric switch, wherein the non-inverting input end of the comparator receives the working current of the electronic device and is connected to the first power source through the first resistor, and the same The input end is connected to the power supply through a second resistor and is grounded through a third resistor. The first end of the electrical switch is connected to the output end of the comparator, the second end is grounded, and the third end is connected to the second power source through the fourth resistor. The fan is connected between the second and third ends of the electric switch, and the comparator compares the voltage at the non-inverting input end with the voltage at the inverting input end thereof, and outputs a control signal to control the closing and opening of the electric switch. Thereby controlling the fan to operate when the electronic device is in an operational state and to stop working when the electronic device is in a standby state. The fan control circuit of claim 1, wherein the electric switch is an NPN transistor, and the first, second and third ends are a base, an emitter and a collector, respectively. The fan control circuit of claim 1, wherein the fifth resistor is connected between the first end of the electrical switch and the second power source. The fan control circuit of claim 1, wherein the first and second power sources are both 12V. The fan control circuit of claim 1, wherein the fan further has a capacitor in parallel. The fan control circuit of claim 1, wherein a capacitor is further connected between the power source and the ground. The fan control circuit of claim 1, wherein the electronic device is a hard disk drive.