TW202205799A - Fan brake circuit - Google Patents

Abstract

A fan brake circuit includes a semiconductor switch unit, a motor, a motor drive circuit, an isolation unit, a charging/discharging unit and a control unit. One end of the motor, the semiconductor switch unit and the control unit serves to receive an input power. The motor drive circuit is electrically connected with the other ends of the motor and the control unit. The isolation unit is electrically connected with the other end of the semiconductor switch unit and the motor drive circuit and the charging/discharging unit. When the fan is powered off, the semiconductor switch unit disconnects from the motor and the motor drive circuit receives the operation voltage provided by the charging/discharging unit and transmits the drive signal to the motor, whereby the motor forms a short-circuit to brake. By means of the design of the fan brake circuit, when the fan is powered off, the fan can quickly brake and stop and the cost is lowered.

Description

fan brake circuit

The present invention relates to a fan braking circuit, in particular to a fan braking circuit which can achieve quick braking and stop when the fan is powered off and reduce cost.

Please refer to FIG. 1A, the conventional fan power-off brake circuit 1 is mainly electrically connected to an input power Vin through a capacitor 11 (usually an aluminum electrolytic capacitor), and the capacitor 11 is used for receiving and storing the input power Vin, and When the fan is powered off, the capacitor 11 releases the stored voltage to directly switch on the upper bridge (upper arm) MOS transistor 121 in the motor 12, so that the motor coil 122 forms a short circuit, and then the phenomenon of fan motor braking is obtained. At the same time, in the process of braking, a counter electromotive force will be generated and then charged back to the capacitor 11, so that the braking function is generated by converting the kinetic energy into electrical energy, until the kinetic energy of the fan blade rotation or the stored voltage is consumed first. If the rotational kinetic energy is consumed first, it means that the fan blade will be braked first, otherwise the stored voltage will be consumed first, and the fan blade will continue to rotate until the inertial force is eliminated (the friction will continue to consume it). The main requirement of the fan power-off braking function is to quickly stop the fan blade completely, so as to avoid safety problems caused by the operator accidentally touching the fan blade, but the existing original design is first consumed in the capacitor 11 It is difficult to effectively meet the demand for rapid (or emergency stop) braking of the fan when it is powered off. In Fig. 1B, it is a conventional actual measurement waveform diagram of the input power Vin, the voltage of the capacitor 11, the voltage of the motor coil 122 and the fan current, the waveform symbol of the input power Vin in the figure is V, and the waveform of the input power Vin is V The arrow Vup in the middle represents the power-on of the input power Vin (that is, the fan is powered on) and the arrow Vdown represents the power-off of the input power Vin (that is, the fan is powered off). The voltage waveform symbol of the capacitor 11 is C, and the voltage waveform C of the capacitor 11 is in the The arrow Cv represents that after the fan is powered off, the stored voltage released by the capacitor 11 is quickly consumed by the motor coil 122 and is lower than the turn-on voltage of the upper arm MOS transistor switch 121, so it cannot be effectively braked and stopped quickly; the waveform symbol of the motor coil voltage is: M, the virtual frame area Moff in the motor coil voltage waveform M presents a sloping down line, which means that the fan motor is still running (that is, the fan blade is still rotating) and the back EMF voltage is continuously generated; the fan current waveform symbol is F Therefore, according to the above-mentioned actual measurement waveform results, the conventional capacitor 11 can only make the fan motor 12 brake for a short time and then lose the braking function, so that the fan blade itself must be rotated until the inertial force is eliminated before it can completely stop. In addition, the problem of reaction potential will also occur during the process of the fan blade itself rotating until the inertial force is eliminated. Therefore, at present, if manufacturers want to improve this part, they generally enlarge the size of the capacitor size of the capacitor 11 to increase the capacitance, but the design space of the fan is often limited, so it is necessary to choose a larger size within the limited space specification. inch/larger capacitance value capacitor 11 or use multiple capacitors 11 in parallel, but it is impossible to choose a larger size and bulky capacitor 11 that can quickly stop the fan. Due to the above factors, the overall cost will be caused Lifting and fan power-off brake circuit 1. The overall fan cannot be miniaturized, and the improvement effect is not obvious.

An object of the present invention is to provide a fan braking circuit that can achieve rapid braking and cost reduction when the fan is powered off. Another object of the present invention is to provide a fan brake circuit capable of miniaturization. In order to achieve the above object, the present invention provides a fan brake circuit, comprising a semiconductor switch unit, a motor, a motor drive circuit, an isolation unit, a charge and discharge unit and a control unit, wherein the semiconductor switch unit has a first One end and a second end, the first end is used for receiving an input power, the motor is electrically connected to the input power and the first end, the motor drive circuit is electrically connected to the motor, and the motor drive circuit is used for A drive signal is output to the motor, the isolation unit is electrically connected between the semiconductor switch unit and the motor drive circuit, the isolation unit has a plurality of resistance elements, and the plurality of resistance elements are respectively electrically connected to the motor drive circuit and the motor drive circuit At the second end, the charging/discharging unit is electrically connected to the plurality of resistive elements for receiving and storing an operating voltage, the control unit is electrically connected to the input power source, the motor driving circuit and the motor, and the control unit is used for Outputting a plurality of control signals to control the motor driving circuit and the motor respectively, wherein when the fan is powered off, the semiconductor switch unit disconnects the connection between the first end and the motor, and the motor driving circuit receives the power provided by the charging and discharging unit. The operating voltage transmits the driving signal to the motor, so that the motor forms a short circuit and brakes. Through the design of the fan brake circuit of the present invention, the fan can effectively achieve the effects of fast braking after power failure, miniaturization and cost reduction.

The above-mentioned objects of the present invention and their structural and functional characteristics will be described with reference to the preferred embodiments of the accompanying drawings. The present invention provides a fan brake circuit. Please refer to Fig. 2A for a block diagram of a fan brake circuit according to an embodiment of the present invention; Fig. 2B for a circuit diagram of the fan brake circuit of Fig. 2A of the present invention; A circuit diagram of a fan brake circuit according to a possible embodiment; Fig. 3A is a block diagram of a fan brake circuit according to an alternative embodiment of the present invention; Fig. 3B is a circuit diagram of the fan brake circuit of Fig. 3A of the present invention; Fig. 4 is the present invention An actual measurement waveform diagram of the input power supply, the capacitor voltage of the charging and discharging unit, the motor coil voltage and the fan current according to an embodiment. As shown in FIGS. 2A and 2B , the fan brake circuit 2 includes a semiconductor switch unit 21 , a motor 22 , a motor drive circuit 23 , an isolation unit 24 , a charging and discharging unit 25 and a control unit 26 , which are implemented in FIG. 2B . In the example, the semiconductor switch unit 21 can choose a diode for illustration, the semiconductor switch unit 21 has a first terminal 211 and a second terminal 212, an anode terminal of the semiconductor switch unit 21 is the first terminal 211 to receive An input power Vin (for example, the input power Vin output by the power supply is 10 volts), a cathode terminal of the semiconductor switch unit 21 is the second terminal 212 , and the semiconductor switch unit 21 and the input power Vin are electrically connected Connect a protection unit 27, the protection unit 27 is provided with a circuit breaker 271 and a first diode 272, the circuit breaker 271 is such as a fuse, one end of the circuit breaker 271 is electrically connected to the input power Vin, the circuit breaker 271 is used for In order to allow the input power Vin to pass through when the fan is normal, and open circuit protection when the fan is abnormal (such as overload or line failure), an anode end and a cathode end of the first diode 272 are respectively electrically connected to the circuit breaker 271 and the anode terminal (ie, the first terminal 211 ) of the semiconductor switch unit 21 . The motor 22 is electrically connected to the input power Vin and the first end 211 of the semiconductor switch unit 21 . The motor 22 can be a three-phase motor or a single-phase motor. In this embodiment, the motor 22 is a single-phase motor. , the motor 22 includes a plurality of upper arm switch parts 221, a plurality of lower arm switch parts 222 and a motor coil 223, the plurality of upper and lower arm switch parts 221, 222 are respectively represented as two upper arm switch parts 221 in this embodiment, such as PMOS The transistor and the two lower arm switching elements 222 are NMOS transistors, but not limited to this. The plurality of upper arm switch elements 221 are correspondingly connected to the plurality of lower arm switch elements 222 , that is, the drain terminals of the two upper arm switch elements 221 are electrically connected to the input power Vin and the anode terminal (ie, the first terminal 211 ) of the semiconductor switch unit 21 . connected, and the drain terminals of the two upper arm switch members 221 are the motor power terminals, the source terminals of the two upper arm switch members 221 are respectively electrically connected to the drain terminals of the corresponding two lower arm switch members 222, and the two upper arm switches The connection point between the element 221 and the two lower arm switch elements 222 is connected to the motor coil 223, and the source terminals of the two lower arm switch elements 222 are electrically connected to a ground terminal Gnd. The motor driving circuit 23 is electrically connected to the motor 22 and the control unit 26 , the motor driving circuit 23 is used for outputting a driving signal to the motor 22 , and the motor driving circuit 23 includes a first motor driving unit 231 and A second motor driving unit 232. In this embodiment, the first and second motor driving units 231 and 232 each comprise a plurality of resistors and at least one transistor (such as an NMOS transistor), and the first and second motor driving units The other ends of the units 231 and 232 are respectively electrically connected to the gate terminals of the plurality of lower arm switching elements 222 of the motor 22 , and the first and second motor driving units 231 and 232 respectively transmit driving signals to the plurality of the motor 22 . The lower arm switch member 222 . In the actual implementation of the present invention, the number of the motor driving unit and the plurality of upper and lower arm switching elements 221 and 222 is adjusted and changed according to the phase number of the motor 22 , for example, the motor 22 is a three-phase motor, and the aforementioned motor driving unit The quantity is adjusted to 3 motor drive units to match the 3 upper arm switch parts 221 and the 3 lower arm switch parts 222 , and so on. The isolation unit 24 is electrically connected between the semiconductor switch unit 21 and the motor driving circuit 23 . The isolation unit 24 has a plurality of resistance elements, and the plurality of resistance elements are electrically connected to the motor driving circuit 23 and the second terminal respectively. 212. In this embodiment, the plurality of resistance elements represent four resistance elements, that is, the plurality of resistance elements have a first resistance element 241, a second resistance element 242, a third resistance element 243 and a fourth resistance element 244, one end of the first and second resistive elements 241, 242 is electrically connected to the other end of the first motor driving unit 231 and the gate terminal of the first lower arm switch element 222 of the motor 22, the third, fourth One end of the resistors 243 and 244 is electrically connected to the other end of the second motor driving unit 232 and the gate terminal of the second lower arm switch 222 of the motor 22 , and the other ends of the first and third resistors 241 and 243 are electrically connected. One end is electrically connected to the second end 212 of the semiconductor switch unit 21 and an operating voltage Vc (such as 5 volts), and the other ends of the second and fourth resistors 242 and 244 are electrically connected to each other, so through the complex resistors The components (ie, the first, second, third, and fourth resistance components 241 , 242 , 243 , 244 ) are used to separate the driving signals for normally driving the fan motor 22 (single-phase motor or three-phase motor). In the actual implementation of the present invention, the number of the plurality of resistance elements is matched with the number of the motor drive units, for example, 3 motor drive units are matched with 3 sets of resistance elements, and each group of resistance elements is, for example, 2 resistance elements or more than 2 resistors. piece composition. The charging and discharging unit 25 is electrically connected to the plurality of resistive elements of the isolation unit 24 for receiving and storing the operating voltage Vc. The charging and discharging unit 25 includes a capacitive element 251 and a charging and discharging resistive element 252 . One end of the resistance element 252 is electrically connected to the other end of the second resistance element 242 and the other end of the fourth resistance element 244 respectively. The other end of the charge-discharge resistance element 252 is electrically connected to one end of the capacitor element 251 . The other end of the capacitor 251 is electrically connected to the ground terminal Gnd, and the first and second motor driving units 231 and 232 receive the high-voltage operating voltage Vc released by the charging and discharging unit 25 to transmit respective driving signals to the plurality of lower arms The switch element 222 is turned on, so by adjusting the capacitance value of the capacitor element 251 in the charge-discharge unit 25 and the resistance value of the charge-discharge resistance element 252, the time for charging and discharging the adjusted potential can be controlled, and then the complex number can be controlled and driven. The conduction time of the lower arm switch member 222 and the braking time of the fan can effectively achieve good adjustment flexibility. In addition, the semiconductor switch unit 21 of the present invention can prevent the voltage (potential) of the capacitor 251 of the charge-discharge unit 25 from being affected by the connection path between the first terminal 211 and the motor power terminal after the fan is powered off. The voltage of the capacitor 251 of the charging and discharging unit 25 can be continuously supplied to the first and second motor driving units 231 and 232 for a long time, so that the first and second motor driving units 231 and 232 transmit the The driving signal drives the corresponding lower arm switches 222 to conduct to form a short circuit with both ends of the motor coil 223 , so that the fan motor 22 can achieve the effect of rapid braking and complete stop. Referring to FIG. 4, it is an actual measurement waveform diagram of the input power Vin, the voltage of the capacitor 251 of the charging and discharging unit 25, the voltage of the motor coil 223 and the fan current according to an embodiment of the present invention. The symbol of the waveform of the power Vin is V, and the arrow Vup in the waveform V of the input power Vin represents that the input power Vin is powered on (that is, the fan is powered on), and the arrow Vdown represents that the input power Vin is powered off (that is, the fan is powered off). The symbol of the 251 voltage waveform is C, and the arrow Cv in the voltage waveform C of the capacitor 251 represents that after the fan is powered off, the operating voltage Vc released and stored by the capacitor 251 can be maintained above and below the turn-on voltage of the plurality of lower arm switching devices 222. The arm switch member 222 has a relatively long conduction time; the voltage waveform symbol of the motor coil 223 is M, and the dashed frame area Moff in the voltage waveform M of the motor coil 223 presents a horizontal smooth line, which means that the fan motor has been quickly braked and stopped (that is, the fan blades have been quickly stopped). stop completely stationary) and no back EMF voltage; the fan current waveform symbol is F, so according to the above-mentioned actual measurement waveform results, the present invention can indeed achieve the effect of fast braking of the fan. In one embodiment, the charge-discharge unit 25 includes a plurality of capacitive elements 251 and a plurality of charge-discharge resistance elements 252 . The control unit 26 is a central processing unit (CPU) or a microcontroller (MCU) or a digital signal processor (DSP). The control unit 26 is connected to the input power Vin and the motor 22 for outputting complex control A signal (such as a PWM signal) controls the motor driving circuit 23 and the motor 22 respectively, and in this embodiment, a second diode 273 is provided between the control unit 26 and the input power Vin, and the second diode 273 The anode terminal of the second diode 273 is electrically connected to the input power source Vin, and the cathode terminal of the second diode 273 is electrically connected to the control unit 26 . The control unit 26 has a plurality of pins, wherein a first and fourth pins 261 and 264 are electrically connected to the gate terminals of the plurality of upper arm switching elements 221 of the motor 22 , and a second and third pins 262 and 263 are electrically connected to each other. One end of the first and second motor driving units 231 and 232 is electrically connected, a fifth pin 265 is electrically connected to the cathode end of the second diode 273, and the four pins of the control unit 26 (ie the first The first, second, third, and fourth pins 261, 262, 263, 264) each output control signal (Pulse Width Modulation; PWM signal) to control the switching action of the plurality of upper arm switching elements 221 (such as whether the switch is on or off) and control The first and second motor driving units 231 and 232 respectively drive the switching actions (eg, whether the switches are on or off) corresponding to the plurality of lower arm switch elements 222 , so as to make the fan motor 22 run. Therefore, when the fan is powered off, the semiconductor switch unit 21 will disconnect the first terminal 211 from the motor 22 (ie, disconnect the connection between the first terminal 211 and the motor power terminal), and at the same time the semiconductor switch unit 21 will prevent the voltage (potential) of the capacitive element 251 of the rear charging and discharging unit 25 from being consumed in reverse, and at this time the charging and discharging unit 25 will release the stored operating voltage Vc to the first and second motor driving units 231 and 232 , so that the first and second motor driving units 231 and 232 drive the corresponding first and second lower arm switching elements 222 to maintain conduction to form the short circuit with both ends of the motor coil 223 , so that the motor 22 can achieve rapid braking Effect. In a possible embodiment, referring to FIG. 2C , a capacitor 28 is disposed between the first diode 272 and the semiconductor switch unit 21 , and one end of the capacitor 28 is connected to the cathode end of the first diode 272 . Electrically connected to the anode terminal of the semiconductor switch unit 21 and the power terminal of the motor 22 , the capacitor 28 receives and stores the input power Vin, and provides the input power Vin to the fan when the fan is powered off through the capacitor 28 The plurality of upper-arm switch elements 221 are turned on, so that the plurality of upper-arm switch elements 221 and the motor coil 223 are short-circuited and braked. Since the motor coil 223 will quickly consume the input power Vin provided by the capacitor element 28, the plurality of upper-arm switch elements 221 are in an inactive state. turn on, at the same time, the charging and discharging unit 25 will provide the operating voltage Vc to the first and second motor driving units 231, 232 to drive the plurality of lower arm switching elements 222 to maintain conduction (turn on), so as to continuously short-circuit the motor coil 223 to achieve The effect of fast fan braking and double braking. In an alternative embodiment, referring to FIGS. 3A and 3B, the semiconductor switch unit 21 is a semiconductor transistor, and the semiconductor transistor is a field-effect transistor (eg, a MOS transistor) or an IGBT transistor. In this embodiment, The semiconductor switch unit 21 is a MOS transistor with switching function, which is used to disconnect the connection between the first terminal 211 of the semiconductor switch unit 21 and the motor power terminal when the fan is powered off, but is not limited to Therefore, any semiconductor transistor that can disconnect the connection between the first terminal and the motor power terminal when the fan is powered off is referred to as the semiconductor switch unit 21 in the present invention. In addition, the semiconductor switch unit 21 has at least one semiconductor switch element. In this alternative embodiment, the semiconductor switch unit 21 is shown as composed of two semiconductor switch elements for illustration, that is, the semiconductor switch unit 21 has a first semiconductor switch. The first and second semiconductor switching devices 21a and 21b are respectively represented as an N-type metal oxide semiconductor (MOS) transistor and a P-type metal oxide semiconductor (MOS) in this embodiment. transistors, and the first and second semiconductor switching elements 21a, 21b each have a first terminal 211a, 211b, a second terminal 212a, 212b and a third terminal 213a, 213b, the first semiconductor switching element 21a One terminal 211a (ie, the third terminal 213 of the semiconductor switch unit 21 ) is the gate terminal electrically connected to the control unit 26 and the input power source Vin, and the third terminal 213a of the first semiconductor switch element 21a is the drain terminal electrically The first terminal 211b connected to the second semiconductor switching element 21b is a gate terminal, the second terminal 212a of the first semiconductor switching element 21a is a source terminal and is electrically connected to the ground terminal Gnd. The second terminal 212b (ie the first terminal 211 of the semiconductor switch unit 21 ) is the source terminal electrically connected to the input power Vin and the motor power terminal, and the third terminal 213b of the second semiconductor switch 21b (ie the semiconductor switch The second terminal 212) of the unit 21 is the drain terminal electrically connected to the other terminals of the first and third resistance elements 241, 243. When the fan is powered off, the first terminal (gate terminal) of the first semiconductor switching element 21a When the voltage is lower than the voltage of the second terminal 212a (source terminal), the voltage of the first terminal 211b (gate terminal) of the second semiconductor switching device 21b is higher than the voltage of the second terminal 212b (source terminal), and the The resistance from the second terminal 212b to the third terminal 213b is very large, so that the second semiconductor switch element 21b is disconnected (non-conductive). The voltage (potential) of the capacitor 251 of the discharge unit 25 will not be discharged from the path between the first terminal 211 and the motor power terminal. Therefore, through the design of the fan braking circuit 2 of the present invention, the effects of fast braking and cost reduction when the fan is powered off can be effectively achieved, and the capacitor value in the charging and discharging unit 25 does not need to be large in size. Therefore, the capacitor 251 of the charging and discharging unit 25 in this case can use small capacitors (such as small ceramic chip capacitors of 0402, 0603, 0805 size, but not limited to this), so as to It is beneficial to install the fan on the circuit board (PCB) without space restrictions, or in the limited space on the circuit board, it can free up more space for other electronic parts (such as IC chips, heat dissipation components or transistors) to set up It can effectively achieve the miniaturization of the fan brake circuit 2, and the overall fan of this case can also achieve the effect of miniaturization with the design of small size and small size of the capacitor.

2: Fan brake circuit 21: Semiconductor switching unit 211, 212, 213: first, second, third end 21a, 21b: first and second semiconductor switching devices 211a, 211b: The first extreme 212a, 212b: second extreme 213a, 213b: The third extreme 22: Motor 221: Upper arm switch parts 222: Lower arm switch parts 223: Motor coil 23: Motor drive circuit 231: The first motor drive unit 232: Second motor drive unit 24: Isolation unit 241, 242, 243, 244: first, second, third, and fourth resistors 25: Charge and discharge unit 251, 28: Capacitive parts 252: Charge and discharge resistors 26: Control unit 261: first pin 262: second pin 263: The third pin 264: Fourth pin 265: fifth pin 27: Protection unit 271: Circuit Breaker 272, 273: first and second diodes Gnd: ground terminal Vin: input power Vc: operating voltage

FIG. 1A is a block diagram of a conventional fan power-off brake circuit. FIG. 1B is an actual measurement waveform diagram of the conventional input power supply, capacitor voltage, motor coil voltage and fan current. FIG. 2A is a block diagram of a fan brake circuit according to an embodiment of the present invention. FIG. 2B is a circuit diagram of the fan brake circuit of FIG. 2A of the present invention. FIG. 2C is a circuit diagram of a fan brake circuit according to a possible embodiment of the present invention. FIG. 3A is a block diagram of a fan brake circuit according to an alternative embodiment of the present invention. FIG. 3B is a circuit diagram of the fan brake circuit of FIG. 3A of the present invention. FIG. 4 is an actual measurement waveform diagram of the input power supply, the capacitor voltage of the charging and discharging unit, the motor coil voltage and the fan current according to an embodiment of the present invention.

2: Fan brake circuit

21: Semiconductor switching unit

211, 212: first and second ends

22: Motor

23: Motor drive circuit

231: The first motor drive unit

232: Second motor drive unit

24: Isolation unit

25: Charge and discharge unit

26: Control unit

27: Protection unit

271: Circuit Breaker

272, 273: first and second diodes

Vin: input power

Claims (10)

A fan brake circuit comprising: a semiconductor switch unit, having a first end and a second end, the first end is used for receiving an input power; a motor electrically connected to the input power source and the first end; a motor driving circuit electrically connected to the motor for outputting a driving signal to the motor; an isolation unit electrically connected between the semiconductor switch unit and the motor driving circuit, the isolation unit has a plurality of resistance elements, and the plurality of resistance elements are respectively electrically connected to the motor driving circuit and the second terminal; a charge-discharge unit electrically connected to the plurality of resistive elements for receiving and storing an operating voltage; a control unit, electrically connected to the input power source, the motor driving circuit and the motor, for outputting a plurality of control signals to control the motor driving circuit and the motor respectively; and When the fan is powered off, the semiconductor switch unit disconnects the connection between the first end and the motor, and the motor drive circuit receives the operating voltage provided by the charge and discharge unit and transmits the drive signal to the motor to make the motor Form a short circuit and brake. The fan braking circuit as claimed in claim 1, wherein the plurality of resistive elements comprises a first resistive element, a second resistive element, a third resistive element and a fourth resistive element, the first, second, third, and fourth resistive elements One end of the resistor is electrically connected to the corresponding motor driving circuit, the other ends of the first and third resistors are electrically connected to the second end of the semiconductor switch unit, and the other ends of the second and fourth resistors are electrically connected to each other . The fan braking circuit of claim 2, wherein the charging and discharging unit comprises a capacitive element and a charging and discharging resistive element, and the charging and discharging resistive element is electrically connected to the other end of the second resistor and one end of the capacitive element, respectively, The other end of the capacitor is electrically connected to a ground. The fan braking circuit of claim 3, wherein the semiconductor switch unit is a diode, an anode terminal of the semiconductor switch unit is the first terminal, and a cathode terminal of the semiconductor switch unit is the second terminal. The fan braking circuit of claim 3, wherein the semiconductor switch unit has a third terminal, a first semiconductor switch element and a second semiconductor switch element, and the first and second semiconductor switch elements each have a first terminal , a second terminal and a third terminal, the third terminal of the semiconductor switch unit is the first terminal of the first semiconductor switch element is electrically connected to the control unit and the input power supply, the first semiconductor switch element The third terminal is electrically connected to the first terminal of the second semiconductor switch element, the second terminals of the first and second semiconductor switch elements are electrically connected to the ground terminal and the input power supply respectively, and the second semiconductor switch element is electrically connected to the ground terminal. The second terminal of the switch element is the first terminal of the semiconductor switch unit, the second terminal of the semiconductor switch unit is the third terminal of the second semiconductor switch element and is electrically connected to the first and third resistance elements the other end of the . The fan braking circuit as claimed in claim 5, wherein the first and second semiconductor switching devices are an N-type metal-oxide-semiconductor transistor and a P-type metal-oxide-semiconductor transistor, respectively, and the first and second semiconductor switching devices are Both the first terminals of the first and second semiconductor switching elements are gate terminals, the second terminals of the first and second semiconductor switching elements are both source terminals, and the third terminals of the first and second semiconductor switching elements are both drain terminals. The fan braking circuit of claim 5, wherein the first and second semiconductor switching elements are semiconductor transistors, and the semiconductor transistors are field effect transistors or IGBT transistors. The fan braking circuit according to claim 2, wherein the control unit has a plurality of pins, the motor driving circuit comprises a first motor driving unit and a second motor driving unit, one end of the first and second motor driving units are respectively A second pin and a third pin of the plurality of pins are electrically connected, and the other end of the first motor driving unit is respectively electrically connected to one end of the first and second resistance elements and the motor, and the second motor The other end of the driving unit is respectively electrically connected to one end of the third and fourth resistive elements and the motor, and a first pin and a fourth pin of the plurality of pins are respectively electrically connected to the motor. The fan brake circuit according to claim 8, wherein the motor has a plurality of upper arm switch parts, a plurality of lower arm switch parts and a motor coil, the plurality of upper arm switch parts are correspondingly connected to the plurality of lower arm switch parts, and the plurality of upper arm switch parts are connected with The connection point between the plurality of lower arm switch parts is connected to the motor coil, the other end of the first motor drive unit is electrically connected to the lower arm switch part of the plurality of lower arm switch parts, and the other end of the second motor drive unit The other lower arm switch part of the plurality of lower arm switches is electrically connected. The fan braking circuit of claim 1, wherein the control unit is a central processing unit, a microcontroller, or a digital signal processor.

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