TWI416863B - Thermal control variable speed circuit without switch noise - Google Patents

Description

Temperature-controlled shifting circuit without switching noise

The present invention relates to a temperature controlled shifting circuit, and more particularly to a temperature controlled shifting circuit without switch noise.

In recent years, the control method of the cooling fan motor speed is mainly achieved by using a Pulse Width Modulation (PWM) signal, and the control method thereof will be described with reference to FIGS. 1 and 2 . The principle of the pulse width modulation control mainly uses a reference voltage signal V _ref and a triangular wave signal TW to adjust the duty time. As shown in FIG. 2, V _ref1 and V _ref2 respectively represent the reference voltage signal V _{ref in} different states. When the reference voltage signal V _ref is V _ref1 , the corresponding working time is T ₁ , and the output PWM signal P is Is P ₁ . When the reference voltage signal V _ref is V _ref2 , its corresponding working time is T ₂ , and the output PWM signal P is P ₂ . The drive circuit 12 then controls the timing of operation of the fan motor 13 in accordance with the PWM signal P.

For example, when the ambient temperature is high, the corresponding reference voltage signal V _ref is generated as V _ref2 , and the triangular signal TW is input to the PWM signal generating module 11 , and the PWM signal generating module 11 generates the P ₂ PWM signal P output and driven. The circuit 12 controls the operation time of the fan motor 13 in accordance with the PWM signal P of P ₂ . Since the operation time T ₂ per unit time is long, the average operation time of the fan motor 13 is long, so the rotation speed of the fan motor 13 is fast. Conversely, when the ambient temperature is lowered, the corresponding reference voltage signal V _ref is generated as V _ref1 , and the PWM signal P outputted by the PWM signal generating module 11 is P ₁ , and the fan is short due to the working time T ₁ per unit time. The average running time of the motor 13 is short, so that the rotational speed of the fan motor 13 is slow, and the purpose of controlling the rotational speed of the fan motor 13 is achieved.

However, the manner in which the fan motor speed is controlled by the PWM signal has the following disadvantages. The driving circuit 12 must constantly receive the PWM signal P to control the fan motor, and the PWM signal P changes in the high and low levels, that is, the occurrence of switching noise, which causes slight noise. When the fan motor is at high speed, this noise is covered by the noise of the fan motor itself, but when the fan motor speed is reduced, the noise is not able to meet the requirements of the system manufacturer. In addition, the operating time of the PWM signal P must be limited to a range of 30% to 85%, thereby ensuring that the driving circuit 12 and the fan motor 13 can be appropriately controlled by the PWM signal P, so that the temperature and the rotational speed range of the fan motor are limited. No adjustments can be made.

In summary, how to avoid switching noise when controlling the speed of the fan motor, and to expand the controllable range of the fan motor speed is an urgent problem to be solved.

In view of the above problems, it is an object of the present invention to provide a temperature-controlled shifting circuit without switching noise, which can avoid switching noise when controlling the fan motor speed.

Another object of the present invention is to provide a temperature-controlled shifting circuit without switching noise, which has a larger controllable range for the rotational speed of the fan motor than the pulse width modulation control method.

In order to achieve the above object, the temperature-controlled shifting power of the invention without switching noise The circuit is connected to a driving circuit, and the driving circuit controls the rotation speed of a fan motor. The temperature-controlled shifting circuit is connected to a power source and outputs a corresponding one of the driving voltages as the ambient temperature changes. The driving circuit drives the fan motor with a driving voltage output from the temperature-controlled shifting circuit to control the rotational speed of the fan motor.

The temperature-controlled shifting circuit includes a reference voltage output circuit and a driving voltage control circuit. The reference voltage output circuit is connected to the power source and outputs a corresponding reference voltage signal according to the ambient temperature change, wherein a first resistor is connected in series with the output end of the reference voltage signal, and a second resistor is connected in parallel to make the reference voltage The signal is more sensitive to changes in ambient temperature. The driving voltage control circuit receives the reference voltage signal output by the reference voltage output circuit, and outputs the corresponding driving voltage according to the size of the reference voltage signal. That is, when the ambient temperature is low, the reference voltage output circuit outputs a relatively low reference voltage signal, and the driving voltage control circuit receives the relatively low reference voltage signal and outputs a relatively low driving voltage, and the fan motor The speed is therefore relatively slow. When the ambient temperature is high, the reference voltage output circuit outputs a relatively high reference voltage signal, and the driving voltage control circuit receives the relatively high reference voltage signal and outputs a relatively high driving voltage, and the speed of the fan motor is Relatively fast. In this way, the rotational speed of the fan motor can be controlled at ambient temperature.

According to the temperature-controlled shifting circuit without switching noise of the present invention, since the rotational speed of the fan motor is controlled only by the magnitude of the driving voltage, a control signal of high and low level mutual conversion is not generated, for example, a pulse width modulation control method is used. So as to avoid switching noise when controlling the fan motor speed News. At the same time, the speed of the fan motor has a larger controllable range than the pulse width modulation control mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a temperature-controlled shifting circuit without switching noise according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein the same elements will be described with the same reference numerals.

Referring to FIG. 3, the temperature-controlled shifting circuit 31 of the present invention is connected to a driving circuit 32, and the driving circuit 32 controls the rotational speed of a fan motor 13. The temperature-controlled shifting circuit 31 is connected to a power source V _cc and outputs a corresponding one of the driving voltages V _D as the ambient temperature changes. The function of the driving circuit 32 is similar to that of the prior art. The difference is only that the driving circuit in the prior art receives the PWM signal, thereby controlling the rotational speed of the fan motor. The driving circuit 32 of the present invention receives the driving voltage V _D . The fan motor 13 is driven by the drive voltage V _D . The function of the fan motor 13 is the same as that of the prior art, and will not be described herein.

Please refer to FIG. 4 , which is a circuit diagram of the temperature-controlled shifting circuit 31 , including a reference voltage output circuit 311 and a driving voltage control circuit 312 . The reference voltage output circuit 311 includes a first resistor R ₁ , a second resistor R ₂ , a thermistor R _th , a third resistor R _{3 ,} and a fourth resistor R ₄ . One end of the third resistor R ₃ is connected to the power source V _cc , and one end of the fourth resistor R ₄ is connected to the other end of the third resistor R ₃ , and the thermistor R _th has a positive temperature coefficient, that is, when the ambient temperature rises, The resistance value of the thermistor R _th rises, one end of which is connected to the other end of the fourth resistor R _{4 , and} the other end of the thermistor R _th is connected to the ground. One end of the first resistor R ₁ is connected between the fourth resistor R ₄ and the thermistor R _th , the other end outputs a reference voltage signal V _ref , and one end of the second resistor R ₂ is connected to the output end of the first resistor R ₁ . The other end is connected to the ground. It should be noted that the second resistor R ₂ can be a variable resistor, and the sensitivity of the reference voltage signal V _ref to changes in ambient temperature can be controlled by adjusting the impedance of the second resistor R ₂ .

The driving voltage control circuit 312 includes an operational amplifier OP, a fifth resistor R ₅ , a sixth resistor R _{6 ,} and a transistor. The non-inverting input terminal of the operational amplifier OP is connected to the output end of the reference voltage output circuit 311, that is, the reference voltage signal V _ref is received, and the fifth resistor R _{5 is} connected to the inverting input terminal of the operational amplifier OP and the output end of the operational amplifier OP. Between the sixth resistor R _{6 is} connected between the inverting input of the operational amplifier OP and the ground. The base of the transistor is connected to the output of the operational amplifier OP, the collector is connected to the power supply V _cc , and the emitter output is driven by the voltage V _D .

Next, the temperature-controlled shifting circuit of the present invention without switching noise is controlled to control the driving speed of the fan motor. Since the thermistor R _th in the reference voltage output circuit 311 is a thermistor having a positive temperature coefficient, when the ambient temperature rises, the resistance value of the thermistor R _th rises, and the position of the point A in FIG. 4 The reference voltage signal V _ref then rises. The reference voltage signal V _ref received by the driving voltage control circuit 312 rises, and the driving voltage V _D outputted by the driving voltage control circuit 312 also rises. Since the driving voltage V _{D of the} driving fan motor 13 rises, the rotation speed of the fan motor 13 rises, and the purpose of controlling the rotation speed of the fan motor 13 is achieved. In short, as shown in FIG. 5, when the ambient temperature is low, the resistance value of the thermistor R _th decreases, and the reference voltage output circuit 311 outputs a correspondingly lower reference voltage signal V _ref-L , and the driving voltage control circuit 312 receives the reference voltage signal V _ref-L and outputs a relatively low driving voltage V _DL , and the fan motor 13 receives the driving voltage V _DL and its rotational speed is relatively slow. When the ambient temperature is high, the resistance value of the thermistor R _th rises, the reference voltage output circuit 311 outputs a relatively high reference voltage signal V _ref-H , and the driving voltage control circuit 312 receives the reference voltage signal V _ref-H . And outputting a relatively high driving voltage V _DH , the fan motor 13 is driven by the driving voltage V _DH , and its rotational speed is relatively fast.

According to the temperature-controlled shifting circuit without switching noise of the present invention, it is not necessary to generate a control signal of high and low level mutual transformation, such as a pulse width modulation control mode, and the speed of the fan motor can be controlled according to the ambient temperature change, so Avoid switching noise when controlling fan motor speed. At the same time, the speed of the fan motor is only controlled by the magnitude of the driving voltage, so the speed of the fan motor has a larger controllable range than the control mode of the pulse width modulation.

The above is intended to be illustrative only and not limiting. Equivalent modifications may be made to the embodiments of the invention described above without departing from the spirit and scope of the invention. For example, at least one capacitor can be connected to the power supply end of the fan motor to filter noise, which can further reduce noise caused by noise. Therefore, any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

11‧‧‧Pulse width modulation signal generation module

12‧‧‧Drive circuit

13‧‧‧Fan motor

12‧‧‧Drive circuit

31‧‧‧temperature controlled shifting circuit

311‧‧‧reference voltage output circuit

312‧‧‧Drive voltage control circuit

32‧‧‧Drive circuit

OP‧‧‧Operational Amplifier

P, P ₁ , P ₂ ‧‧‧ pulse width modulation signal

R ₁ ‧‧‧first resistance

R ₂ ‧‧‧second resistance

R ₃ ‧‧‧third resistor

R ₄ ‧‧‧fourth resistor

R ₅ ‧‧‧ fifth resistor

R ₆ ‧‧‧6th resistor

R _th ‧‧‧Thermistor

T ₁ , T ₂ ‧ ‧ working hours

TW‧‧‧ triangle wave signal

V _cc ‧‧‧ power supply

V _D ‧‧‧Drive voltage signal

V _ref , V _ref1 , V _ref2 ‧‧‧ reference voltage signal

FIG. 1 is a block diagram of a conventional pulse width modulation control fan motor speed.

2 is a schematic diagram of the principle of a conventional pulse width modulation control method.

3 is a block diagram of a temperature-controlled variable speed fan motor without switching noise in accordance with a preferred embodiment of the present invention.

4 is a circuit diagram of a temperature-controlled shifting circuit without switching noise according to a preferred embodiment of the present invention.

Figure 5 is a diagram showing the relationship between a reference voltage signal and a driving voltage in a preferred embodiment of the present invention.

31‧‧‧temperature controlled shifting circuit

311‧‧‧reference voltage output circuit

312‧‧‧Drive voltage control circuit

OP‧‧‧Operational Amplifier

R ₁ ‧‧‧first resistance

R ₂ ‧‧‧second resistance

R ₃ ‧‧‧third resistor

R ₄ ‧‧‧fourth resistor

R ₅ ‧‧‧ fifth resistor

R ₆ ‧‧‧6th resistor

R _th ‧‧‧Thermistor

V _cc ‧‧‧ power supply

V _D ‧‧‧Drive voltage signal

V _ref ‧‧‧reference voltage signal

Claims (5)

A temperature-controlled shifting circuit with no switching noise is connected to a driving circuit, and the driving circuit controls the rotation speed of a fan motor. The temperature-controlled shifting circuit comprises: a reference voltage output circuit connected to the power source and The ambient temperature change output corresponds to one of the reference voltage signals, wherein a first resistor is connected in series with the output end of the reference voltage signal, and a second resistor is connected in parallel; and a driving voltage control circuit includes an operational amplifier, wherein the operation An inverting input end of the amplifier is coupled to an output end of the operational amplifier, and a non-inverting input end of the operational amplifier is connected to an output end of the reference voltage output circuit, receives the reference voltage signal, and outputs an output according to the magnitude of the reference voltage signal One of the driving voltages, the driving circuit drives the fan motor to control the rotational speed of the fan motor. The temperature-controlled shifting circuit of the non-switching noise of claim 1, wherein the reference voltage output circuit further comprises: a third resistor, one end of which is connected to the power source; and a fourth resistor, one end of which is connected to the third The other end of the resistor; and a thermistor having a positive temperature coefficient, one end of which is connected to the other end of the fourth resistor, and the other end of which is connected to the ground; wherein one end of the first resistor is connected to the fourth resistor and The other end of the thermistor outputs the reference voltage signal; one end of the second resistor is connected to the output end of the first resistor, and the other end is connected to the ground. For example, the temperature-controlled shifting circuit without switching noise is applied in the first item of the patent scope, The second resistor is a variable resistor. The temperature-controlled shifting circuit of the non-switching noise of claim 1, wherein the driving voltage control circuit further comprises: a fifth resistor connected to the inverting input terminal of the operational amplifier and the output end of the operational amplifier a sixth resistor connected between the inverting input of the operational amplifier and the ground; and a transistor having a base connected to the output of the operational amplifier, a collector connected to the power source, and an emitter outputting the driver Voltage. For example, the temperature-controlled shifting circuit of the switchless noise without switching noise of the first application of the patent scope is matched with at least one capacitor, and the at least one capacitor is connected to the power supply end of the fan motor for filtering noise.