A control method for a DC fan drive circuit with soft start and overcurrent protection functions

Abstract

The invention discloses a control method for a DC fan drive circuit with soft start and overcurrent protection functions, including: a low-voltage DC fan, and further including: a single-chip microcomputer, an enable control unit, a soft start unit, a drive unit, and a fault protection and automatic restart unit; this circuit has the functions of soft start, overcurrent protection, and automatic restart. The entire hardware circuit is composed of basic diodes, triodes, resistors, and capacitors, without the need for a dedicated drive protection chip. It has the advantages of low cost, stability, and reliability.

Description

Technical Field

[0001] The present invention belongs to the field of DC fan drive, and particularly relates to a control method for a DC fan drive circuit with soft start and overcurrent protection functions. Background Art

[0002] In products such as servo drivers, industrial computers, and instrumentation, low-voltage DC fans are widely used for internal chassis cooling. Due to the long-term operation of industrial products under abnormal application conditions such as high temperature, dust, and foreign objects falling in, fan products are prone to failures such as short circuits and locked rotors. When the above problems occur, the hardware drive protection circuit can effectively detect the occurrence of the fault and make a response for protection.

[0003] Existing solutions are as follows:

[0004] Use a dedicated power switch drive chip, such as Infineon's BTS462T, STMicroelectronics' VN820B5TR-E, etc. Such chips integrate protection and drive circuits internally.

[0005] Select a DC fan product with fault protection and soft start functions, and the drive and protection circuits are integrated inside the fan.

[0006] Whether choosing a dedicated drive chip or a DC fan with integrated internal functions is not friendly to products sensitive to hardware costs. Moreover, for a power switch drive chip, if soft start of the fan is to be achieved, the PWM drive method needs to be sampled, which requires resource configuration of the single-chip microcomputer pins. Summary of the Invention

[0007] In order to solve the technical problems existing in the background art, the present invention aims to provide a control method for a DC fan drive circuit with soft start and overcurrent protection functions.

[0008] To solve the technical problems, the technical solution of the present invention is as follows:

[0009] A control method for a DC fan drive circuit with soft start and overcurrent protection functions, including: a fan, and further including: a single-chip microcomputer, an enable control unit, a soft start unit, a drive unit, and a fault protection automatic restart unit;

[0010] The single-chip microcomputer is signal-connected to the input end of the fault protection automatic restart unit and the input end of the enable control unit. The output end of the enable control unit and the output end of the fault protection automatic restart unit are signal-connected to the input end of the soft start unit. The output end of the soft start unit is signal-connected to the input end of the drive unit. The output end of the drive unit is electrically connected to the fan and the input end of the fault protection automatic restart unit;

[0011] The enabling control unit performs level and logic conversion on the enabling control instruction of the single-chip microcomputer for the fan to obtain a converted signal, and enables the driving unit to start and stop according to the converted signal;

[0012] After receiving the converted signal, the driving unit drives the fan to start and stop according to the correct control logic and bears the load current of the fan working circuit;

[0013] The soft start unit samples the load current of the fan working circuit in real time. At each moment when the fan starts, it limits the starting current of the fan until the current of the fan working circuit reaches the stable working current. And when an overcurrent fault occurs, it pulls down the converted signal received by the driving unit to disconnect the fan working circuit in time, achieving the function of overcurrent protection;

[0014] The fault protection and automatic restart unit monitors the state of the fan working circuit, shuts off the fan circuit of the driving unit, and automatically restarts the driving unit to form the fan working circuit after receiving the fault elimination signal sent by the soft start unit; when the fan is in an abnormal working state, it controls the converted signal to make the driving unit form the fan working circuit, achieving the function of automatic restart.

[0015] The fan soft start driving circuit composed of the triode Q5, the triode Q3 and the sampling resistor R8 solves the problem of the power supply stability caused by the excessive power at the moment when the fan starts; the protection function of the driving circuit when the fan has a continuous overcurrent fault brought by the fault protection and automatic restart unit circuit; and the function that the driving circuit automatically restarts without power-off restart or manual reset after the overcurrent fault is eliminated.

[0016] Further, the fault protection and automatic restart unit includes: resistor R1, resistor R2, resistor R3, resistor R4, capacitor C3, capacitor C2, zener diode DZ1, triode Q1 and triode Q2; one end of the resistor R2 inputs a +24V voltage, the other end of the resistor R2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the capacitor C3 and the base of the triode Q2, one end of the resistor R3 inputs the enabling control signal of the fan, the other end of the capacitor C3 is connected to the emitter of the triode Q2, the other end of the capacitor C2, the other end of the resistor R4 and the emitter of the triode Q1, the collector of the triode Q2 is connected to one end of the capacitor C2, one end of the resistor R1 and the output end of the zener diode DZ1, the input end of the zener diode DZ1 is connected to one end of the resistor R4 and the base of the triode Q1, and the other end of the resistor R4 is grounded.

[0017] Further, the enabling control unit includes: resistor R5, resistor R6, resistor R7, capacitor C4, and NPN transistor Q4. One end of resistor R5 and one end of resistor R7 input the enabling control signal of the fan. The other end of resistor R5 is connected to the +24V voltage. One end of resistor R6 is connected to the other end of resistor R5. The other end of resistor R6 is connected to the collector of NPN transistor Q4. The other end of resistor R7 is connected to the base of NPN transistor Q4 and one end of capacitor C4. The other end of capacitor C4 is connected to the emitter of NPN transistor Q4.

[0018] Further, the soft start unit includes: resistor R8 and transistor Q5. The collector of transistor Q5 is connected to the collector of NPN transistor Q4 and the collector of transistor Q1. The emitter of transistor Q5 is connected to the emitter of NPN transistor Q4 and the other end of resistor R8. One end of resistor R8 is connected to the base of transistor Q5. The other end of resistor R8 is grounded.

[0019] Further, the driving unit includes: transistor Q3, capacitor C1, and fan interface CNF1. The base of transistor Q3 is connected to the collector of transistor Q1. The emitter of transistor Q3 is connected to one end of resistor R8. The collector of transistor Q3 is connected to port 2 of capacitor C1, the other end of resistor R1, and pin 2 of fan interface CNF1. Port 1 of capacitor C1 is connected to the +24V voltage. Port 1 of capacitor C1 is connected to pin 1 of fan interface CNF1.

[0020] Further, when the enabling control signal input to the fan is at a high level, NPN transistor Q4 is turned on, and the base voltage of transistor Q3 is pulled down. At this time, the CE poles of transistor Q3 are turned off, and there is no complete circuit for the fan, that is, the fan cannot start. When the enabling control signal input to the fan is at a low level, the CE poles of transistor Q4 are turned off, and the base voltage of transistor Q3 is determined by the states of transistor Q1 and transistor Q5. When both transistor Q1 and transistor Q5 are in the off state, the base level of transistor Q3 is pulled up. At this time, the CE poles of transistor Q3 are turned on, and the fan forms a complete circuit, that is, the fan starts. At the moment of startup, transistor Q3 operates in the saturation region.

[0021] Further, when the enable control signal of the input fan is at a high level, the CE pole of the triode Q2 is turned on, and the voltage at the C pole of the triode Q2 is the voltage drop Vce of the triode Q2; when the enable control signal of the fan is converted to a low level and there is no overcurrent fault in the fan working circuit, the triode Q3 is turned on and the fan is started; at the same time, the CE pole of the triode Q2 is turned off, the CE pole of the triode Q3 is turned on, and the voltage at the C pole of the triode Q3 is pulled down; the voltage of the capacitor C2 is lower than the stable voltage of the zener diode DZ1, and the triode Q1 will not be turned on; then the fan working circuit driven by the triode Q3 works normally;

[0022] If there are factors such as fan stalling or short circuit, causing continuous overcurrent in the fan working circuit; the resistor R8 samples the current to turn on the triode Q5, the CE pole of the triode Q3 is closed and cut off, the voltage at the C pole of the triode Q3 rises, and the capacitor C2 is charged through the resistor R1. When the voltage accumulated by the C2 capacitor exceeds the stable voltage of the zener diode DZ1, the base current of the triode Q1 flows through, the CE pole of the triode Q1 is turned on, pulling down the base voltage of the triode Q3, turning off the CE terminal of the triode Q3, and disconnecting the fan circuit;

[0023] When the factors of stalling or short circuit are removed, the current sampled by the resistor R8 decreases, and the fan circuit automatically enters the soft start working state.

[0024] Further, when the fan has an overcurrent abnormality in the working circuit due to excessive instantaneous starting current, the resistor R8 samples the current in the fan working circuit, raises the base voltage of the triode Q5, turns on the CE pole of the triode Q5, and at the same time pulls down the base voltage of the triode Q3, reducing the CE pole current of the triode Q3 to achieve the effect of current limiting; at this time, the triode Q3 and the triode Q5 work in the amplification region or the cut-off region;

[0025] When the overcurrent abnormality in the fan working circuit is eliminated, the resistor R8 samples the current in the fan working circuit, and the base voltage of the triode Q5 drops to turn off the CE pole of the triode Q5; at this time, the base voltage of the triode Q3 rises, and the CE pole current of the triode Q3 rises to achieve the function of current limiting soft start; when the fan is turned on instantaneously, the triode Q3 works in the saturation region.

[0026] Further, pin 1 of the fan interface CNF1 is connected to the positive pole of the fan, pin 2 of the fan interface CNF1 is connected to the negative pole of the fan, and the capacitor C1 is a fan power supply filter capacitor, which is used to eliminate the voltage sag and overshoot caused by the fan turning on and off.

[0027] Compared with the prior art, the advantages of the present invention are:

[0028] The present invention has soft start, overcurrent protection, and automatic restart functions. The entire hardware circuit is composed of basic diodes, triodes, resistors, and capacitors, without the need for a dedicated driver protection chip. It has the advantages of low cost, stability, and reliability. The hardware circuit solution provided by the present invention only needs to use discrete components such as resistors, capacitors, diodes, and triodes to achieve the overcurrent protection function of the fan, with a large cost advantage. After the locked-rotor anomaly is removed, the hardware circuit can drive the fan to work again without power-off or reset. And each startup method of the fan is soft start, avoiding power interference problems such as voltage sag and output overload caused by excessive instantaneous power at startup, which affects the working reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 , System block diagram of the control method of a DC fan drive circuit with soft start and overcurrent protection functions according to the present invention;

[0030] Figure 2 , Circuit connection diagram of the control method of a DC fan drive circuit with soft start and overcurrent protection functions according to the present invention.

[0031] Figure 3 , Circuit simulation diagram without soft start function;

[0032] Figure 4 , Circuit simulation diagram with soft start function;

[0033] Figure 5 , Simulation diagram of simulating the open-circuit fault of the fan. DETAILED DESCRIPTION OF THE INVENTION

[0034] The following describes the specific embodiments of the present invention in conjunction with the embodiments:

[0035] It should be noted that the structures, ratios, sizes, etc. shown in this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the implementation conditions of the present invention. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0036] At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of description and are not used to limit the scope of implementation of the present invention. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope of implementation of the present invention.

[0037] Embodiment 1:

[0038] As Figure 1As shown in the figure, a control method for a DC fan drive circuit with soft start and overcurrent protection functions, including: the fan, i.e., a low-voltage DC fan, further including: a single-chip microcomputer, an enable control unit, a soft start unit, a drive unit, and a fault protection and automatic restart unit;

[0039] The input end of the fault protection and automatic restart unit and the input end of the enable control unit are signal-connected to the single-chip microcomputer. The output end of the enable control unit and the output end of the fault protection and automatic restart unit are signal-connected to the input end of the soft start unit. The output end of the soft start unit is signal-connected to the input end of the drive unit. The output end of the drive unit is electrically connected to the fan and the input end of the fault protection and automatic restart unit;

[0040] The enable control unit performs level and logic conversion on the fan enable control instruction sent by the single-chip microcomputer to obtain a converted signal, so that the drive unit starts and stops according to the converted signal;

[0041] After receiving the converted signal, the drive unit drives the fan to start and stop according to the correct control logic and bears the load current of the fan working circuit;

[0042] The soft start unit samples the load current of the fan working circuit in real time. At the moment of each fan start, it limits the start current of the fan until the current of the fan working circuit reaches the stable working current. And when an overcurrent fault occurs, it pulls down the converted signal received by the drive unit to disconnect the fan working circuit in time to achieve the function of overcurrent protection;

[0043] The fault protection and automatic restart unit monitors the state of the fan working circuit, shuts off the fan circuit of the drive unit, and automatically restarts the drive unit to form the fan working circuit after receiving the fault elimination signal sent by the soft start unit; when the fan is in an abnormal working state of normal start but not started, it controls the converted signal to make the drive unit form the fan working circuit to achieve the function of automatic restart.

[0044] The fan soft start drive circuit composed of triode Q5, triode Q3 and sampling resistor R8 solves the problem of excessive power at the moment of fan start causing power supply instability; the protection function of the drive circuit when the fan has a continuous overcurrent fault brought by the fault protection and self-restart unit circuit; and the function of automatically restarting the drive circuit without power-off restart or manual reset after the overcurrent fault is eliminated.

[0045] Further, as Figure 2As shown in the figure, the fault protection automatic restart unit includes: resistor R1, resistor R2, resistor R3, resistor R4, capacitor C3, capacitor C2, zener diode DZ1, triode Q1 and triode Q2; one end of resistor R2 inputs a +24V voltage, the other end of resistor R2 is connected to one end of resistor R3, the other end of resistor R3 is connected to one end of capacitor C3 and the base of triode Q2, one end of resistor R3 inputs the enable control signal of the fan, the other end of capacitor C3 is connected to the emitter of triode Q2, the other end of capacitor C2, the other end of resistor R4 and the emitter of triode Q1, the collector of triode Q2 is connected to one end of capacitor C2, one end of resistor R1 and the output end of zener diode DZ1, the input end of zener diode DZ1 is connected to one end of resistor R4 and the base of triode Q1, and the other end of resistor R4 is grounded.

[0046] Further, as Figure 2 shown, the enable control unit includes: resistor R5, resistor R6, resistor R7, capacitor C4 and NPN type triode Q4, one end of resistor R5 and one end of resistor R7 input the enable control signal of the fan, the other end of resistor R5 is connected to the +24V voltage, one end of resistor R6 is connected to the other end of resistor R5, the other end of resistor R6 is connected to the collector of NPN type triode Q4, the other end of resistor R7 is connected to the base of NPN type triode Q4 and one end of capacitor C4, and the other end of capacitor C4 is connected to the emitter of NPN type triode Q4.

[0047] Further, as Figure 2 shown, the soft start unit includes: resistor R8 and triode Q5, the collector of triode Q5 is connected to the collector of NPN type triode Q4 and the collector of triode Q1, the emitter of triode Q5 is connected to the emitter of NPN type triode Q4 and the other end of resistor R8, one end of resistor R8 is connected to the base of triode Q5, and the other end of resistor R8 is grounded.

[0048] Further, as Figure 2 shown, the drive unit includes: triode Q3, capacitor C1 and fan interface CNF1, the base of triode Q3 is connected to the collector of triode Q1, the emitter of triode Q3 is connected to one end of resistor R8, the collector of triode Q3 is connected to port 2 of capacitor C1, the other end of resistor R1 and pin 2 of fan interface CNF1, port 1 of capacitor C1 is connected to the +24V voltage, and port 1 of capacitor C1 is connected to pin 1 of fan interface CNF1.

[0049] Further, when the enable control signal input to the fan is at a high level, the NPN transistor Q4 is turned on, and the base voltage of the transistor Q3 is pulled down. At this time, the CE pole of the transistor Q3 is turned off, and there is no complete circuit for the fan, that is, the fan cannot start. When the enable control signal input to the fan is at a low level, the CE pole of the transistor Q4 is turned off, and the base voltage of the transistor Q3 is determined by the states of the transistors Q1 and Q5. When both the transistors Q1 and Q5 are in the off state, the base level of the transistor Q3 is pulled up. At this time, the CE pole of the transistor Q3 is turned on, and the fan forms a complete circuit, that is, the fan starts. At the moment of startup, the transistor Q3 operates in the saturation region.

[0050] Further, when the enable control signal input to the fan is at a high level, the CE pole of the transistor Q2 is turned on, and the C - pole voltage of the transistor Q2 is the voltage drop Vce of the transistor Q2. When the enable control signal of the fan is converted to a low level and there is no over - current fault in the fan working circuit, the transistor Q3 is turned on, and the fan starts. At the same time, the CE pole of the transistor Q2 is turned off, the CE pole of the transistor Q3 is turned on, and the C - pole voltage of the transistor Q3 is pulled down. The voltage of the capacitor C2 is lower than the stable voltage of the zener diode DZ1, and the transistor Q1 will not be turned on. Then the fan working circuit driven by the transistor Q3 works normally.

[0051] If there are factors such as fan stalling or short - circuit, causing continuous over - current in the fan working circuit; the resistor R8 samples the current, turning on the transistor Q5, turning off and cutting off the CE pole of the transistor Q3, increasing the C - pole voltage of the transistor Q3, charging the capacitor C2 through the resistor R1. When the voltage accumulated by the C2 capacitor exceeds the stable voltage of the zener diode DZ1, the base current of the transistor Q1 flows through, the CE pole of the transistor Q1 is turned on, pulling down the base voltage of the transistor Q3, turning off the CE end of the transistor Q3, and disconnecting the fan circuit.

[0052] After the stalling or short - circuit factors are removed, the current sampled by the resistor R8 decreases, and the fan circuit automatically enters the soft - start working state.

[0053] Further, when the fan has an over - current anomaly in the working circuit due to excessive instantaneous startup current, the resistor R8 samples the current in the fan working circuit, increasing the base voltage of the transistor Q5, turning on the CE pole of the transistor Q5, and at the same time pulling down the base voltage of the transistor Q3, decreasing the CE - pole current of the transistor Q3, achieving the effect of current limiting. At this time, the transistors Q3 and Q5 operate in the amplification region or the cut - off region.

[0054] When the overcurrent anomaly in the working circuit of the fan is eliminated, the resistor R8 samples the current of the fan working circuit, and the base voltage of the triode Q5 drops to turn off the CE pole of the triode Q5; at this time, the base voltage of the triode Q3 rises, and the CE pole current of the triode Q3 rises, achieving the function of current-limiting soft start; when the fan is turned on instantaneously, the triode Q3 operates in the saturation region.

[0055] Further, pin 1 of the fan interface CNF1 is connected to the positive pole of the fan, pin 2 of the fan interface CNF1 is connected to the negative pole of the fan, and the capacitor C1 is a fan power supply filter capacitor, which is used to eliminate the voltage sag and overshoot caused when the fan is turned on and off.

[0056] Embodiment 2:

[0057] As Figure 3 shown, in the circuit schematic simulation without the soft start function, at the moment when the fan starts, the peak value of the collector current of the driving triode is 2.75A.

[0058] As Figure 4 shown, in the soft start function of this embodiment, at the moment when the fan starts, the peak value of the collector current of the driving triode is 0.33A.

[0059] As Figure 5 shown, simulate the fan open circuit fault; during the fan enabling period, when a fault occurs, enter the overcurrent protection; after the fault is eliminated, automatically enter the soft start recovery, which meets the design requirements. The actual application test is consistent with the simulation result.

[0060] The fan soft start driving circuit composed of the triode Q5, the triode Q3 and the sampling resistor R8 solves the problem of the power supply stability caused by the excessive power at the moment when the fan starts;

[0061] When the fan has a continuous overcurrent fault, the protection function of the driving circuit brought by the fault protection self-restart unit circuit; and the function that the driving circuit automatically restarts without power-off restart or manual reset after the overcurrent fault is eliminated;

[0062] For the same circuit principle in the circuit diagram of the present invention, the circuit design can also be realized by replacing other similar parameter components. For example, replace the zener diode DZ1 to modify the voltage threshold for triggering the overcurrent protection; or replace the specifications of the resistor R1 and the capacitor C2 to reduce or increase the delay time for triggering the overcurrent protection.

[0063] / FAN_EN is the enabling control signal of the fan. When a low level is input, the fan is enabled and turned on; when a high level +24V is input, the fan is disabled and turned off.

[0064] Fan drive unit: CNF1 is the interface of the fan. Pin 1 is connected to the positive pole of the DC fan, and Pin 2 is connected to the negative pole of the DC fan. Capacitor C1 is the power filter capacitor of the fan, which is used to eliminate the voltage sag and overshoot caused by the fan turning on and off.

[0065] Fan enable control unit: It consists of resistors R5, R6, R7, capacitor C4, and NPN transistor Q4. When the / FAN_EN signal is at a high level, transistor Q4 is turned on, and the base B voltage of transistor Q3 is pulled low, and the CE poles of transistor Q3 are turned off, and the fan has no complete circuit, so the fan cannot start. When the / FAN_EN signal is at a low level, the CE poles of transistor Q4 are turned off, and the base voltage of transistor Q3 depends on the states of transistors Q1 and Q5. When both Q1 and Q5 are in the off state, the base B level of Q3 is pulled high, and the CE poles of Q3 are turned on, and the fan forms a complete circuit, and the fan starts. At the moment of starting, transistor Q3 works in the saturation region.

[0066] Fan soft start unit: It consists of resistor R8 and transistor Q5. When the fan has an overcurrent anomaly in the working circuit due to excessive instantaneous starting current. Resistor R8 samples the current, causing the base B voltage of transistor Q5 to rise, and the CE poles to turn on. At the same time, it pulls down the base voltage of transistor Q3, causing the CE pole current of Q3 to decrease, achieving the effect of current limiting. When the overcurrent anomaly is eliminated, resistor R8 samples the current, the base B voltage of transistor Q5 drops to turn off the CE poles, the base voltage of transistor Q3 rises, and the CE pole current rises, achieving the function of current limiting soft start. At this stage, when the fan is turned on instantaneously, Q3 works in the saturation region; during the current limiting action, Q3 and Q5 work in the amplification region or the cut-off region.

[0067] Fault protection automatic restart unit: It consists of resistors R1, R2, R3, R4, capacitors C1, C2, zener diode DZ1, and transistors Q1 and Q2. When the fan enable control signal / FAN_EN signal is at a high level, the CE poles of transistor Q2 are turned on, and the voltage at the C pole of transistor Q2 is only the voltage drop Vce of Q2. When the fan enable control signal / FAN_EN signal switches to a low level and there is no overcurrent fault in the fan working circuit, transistor Q3 turns on the fan, and at the same time, the CE poles of transistor Q2 are turned off. Since the CE poles of Q3 are turned on, the voltage at the C pole of Q3 is pulled down, and the voltage of capacitor C2 is lower than the stable voltage of zener diode DZ1, which will not cause Q1 to turn on; the fan working circuit driven by Q3 works normally. If factors such as fan blockage or short circuit cause continuous overcurrent in the fan working circuit, resistor R8 samples the current to turn on Q5. After the CE poles of Q3 are turned off, the voltage at the C pole of Q3 rises, and capacitor C2 is charged through resistor R1. When the voltage accumulated in capacitor C2 exceeds the stable voltage of zener diode DZ1, the base current of transistor Q1 flows through, and the CE poles are turned on, pulling down the base voltage of transistor Q3 to turn off the CE terminals of Q3, disconnecting the fan circuit. After the blockage or short circuit state is removed, the current sampled by resistor R8 decreases, and the fan circuit automatically enters the soft start working state.

[0068] The above has described the preferred embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

[0069] Many other changes and modifications can be made without departing from the concept and scope of the present invention. It should be understood that the present invention is not limited to specific embodiments, and the scope of the present invention is defined by the appended claims.

Claims

1. A control method for a DC fan drive circuit with soft start and overcurrent protection functions, comprising: A fan, characterized in that it further comprises: a single-chip microcomputer, an enable control unit, a soft start unit, a drive unit, and a fault protection automatic restart unit; The input end of the fault protection automatic restart unit and the input end of the enable control unit are signal-connected to the single-chip microcomputer. The output end of the enable control unit and the output end of the fault protection automatic restart unit are signal-connected to the input end of the soft start unit. The output end of the soft start unit is signal-connected to the input end of the drive unit. The output end of the drive unit is electrically connected to the fan and the input end of the fault protection automatic restart unit; The enable control unit performs level and logic conversion on the fan enable control instruction sent by the single-chip microcomputer to obtain a converted signal, so that the drive unit starts and stops starting according to the converted signal; After receiving the converted signal, the drive unit drives the fan to start and stop starting according to the correct control logic and bears the load current of the fan working circuit; The soft start unit samples the load current of the fan working circuit in real time. At the moment of each fan start, it limits the start current of the fan until the current of the fan working circuit reaches the stable working current. And when an overcurrent fault occurs, it pulls down the converted signal received by the drive unit to timely disconnect the fan working circuit; The fault protection automatic restart unit monitors the state of the fan working circuit, shuts off the fan circuit of the drive unit, and automatically restarts the drive unit to form the fan working circuit after receiving the fault elimination signal sent by the soft start unit; when the fan is in an abnormal working state, it controls the converted signal to make the drive unit form the fan working circuit to achieve the function of automatic restart; The fault protection automatic restart unit includes: resistor R1, resistor R2, resistor R3, resistor R4, capacitor C3, capacitor C2, zener diode DZ1, triode Q1 and triode Q2; One end of the resistor R2 inputs a +24V voltage, the other end of the resistor R2 is connected to one end of the resistor R3, the other end of the resistor R3 is connected to one end of the capacitor C3 and the base of the triode Q2, the enable control signal of the fan is input to one end of the resistor R3, the other end of the capacitor C3 is connected to the emitter of the triode Q2, the other end of the capacitor C2, the other end of the resistor R4 and the emitter of the triode Q1, the collector of the triode Q2 is connected to one end of the capacitor C2, one end of the resistor R1 and the output end of the zener diode DZ1, the input end of the zener diode DZ1 is connected to one end of the resistor R4 and the base of the triode Q1, and the other end of the resistor R4 is grounded.

2. The control method of a DC fan drive circuit with soft start and overcurrent protection functions according to claim 1, characterized in that, The enable control unit includes: resistor R5, resistor R6, resistor R7, capacitor C4 and NPN-type triode Q4. One end of the resistor R5 and one end of the resistor R7 input the fan enable control signal. The other end of the resistor R5 is connected to the +24V voltage. One end of the resistor R6 is connected to the other end of the resistor R5. The other end of the resistor R6 is connected to the collector of the NPN-type triode Q4. The other end of the resistor R7 is connected to the base of the NPN-type triode Q4 and one end of the capacitor C4. The other end of the capacitor C4 is connected to the emitter of the NPN-type triode Q4.

3. The control method of a DC fan drive circuit with soft start and overcurrent protection functions according to claim 2, characterized in that, The soft start unit includes: resistor R8 and triode Q5. The collector of triode Q5 is connected to the collectors of NPN-type triode Q4 and triode Q1. The emitter of triode Q5 is connected to the emitters of NPN-type triode Q4 and the other end of resistor R8. One end of resistor R8 is connected to the base of triode Q5, and the other end of resistor R8 is grounded.

4. The control method of a DC fan drive circuit with soft start and overcurrent protection functions according to claim 3, characterized in that, The drive unit includes: triode Q3, capacitor C1 and fan interface CNF1. The base of triode Q3 is connected to the collector of triode Q1. The emitter of triode Q3 is connected to one end of resistor R8. The collector of triode Q3 is connected to port 2 of capacitor C1, the other end of resistor R1 and pin 2 of fan interface CNF1. Port 1 of capacitor C1 is connected to +24V voltage, and port 1 of capacitor C1 is connected to pin 1 of fan interface CNF1.

5. The control method of a DC fan drive circuit with soft start and overcurrent protection functions according to claim 4, characterized in that, When the enable control signal input to the fan is at a high level, the NPN-type triode Q4 is turned on, and the base voltage of triode Q3 is pulled down. At this time, the CE poles of triode Q3 are turned off, and there is no complete circuit for the fan, that is, the fan cannot start. When the enable control signal input to the fan is at a low level, the CE poles of triode Q4 are turned off, and the base voltage of triode Q3 is determined by the states of triode Q1 and triode Q5. When both triode Q1 and triode Q5 are in the off state, the base level of triode Q3 is pulled up. At this time, the CE poles of triode Q3 are turned on, and the fan forms a complete circuit, that is, the fan starts. At the moment of startup, triode Q3 works in the saturation region.

6. The control method of a DC fan drive circuit with soft start and overcurrent protection functions according to claim 4, characterized in that, When the enable control signal input to the fan is at a high level, the CE poles of triode Q2 are turned on, and the C-pole voltage of triode Q2 is the voltage drop Vce of triode Q2. When the enable control signal of the fan is converted to a low level and there is no overcurrent fault in the fan working circuit, triode Q3 is turned on and the fan starts. At the same time, the CE poles of triode Q2 are turned off, the CE poles of triode Q3 are turned on, and the C-pole voltage of triode Q3 is pulled down. The voltage of capacitor C2 is lower than the stable voltage of zener diode DZ1, and triode Q1 will not be turned on. Then the fan working circuit driven by triode Q3 works normally. If there are factors such as fan stalling or short circuit, resulting in continuous overcurrent in the fan working circuit; Use resistor R8 to sample the current, turn on triode Q5, turn off and cut off the CE poles of triode Q3, raise the C-pole voltage of triode Q3, charge capacitor C2 through resistor R1. When the voltage accumulated by capacitor C2 exceeds the stable voltage of zener diode DZ1, the base current of triode Q1 flows through, the CE poles of triode Q1 are turned on, pull down the base voltage of triode Q3, and turn off the CE ends of triode Q3, disconnecting the fan circuit; After the factors of stalling or short circuit are removed, the current sampled by resistor R8 decreases, and the fan circuit automatically enters the soft start working state.

7. The control method of a DC fan drive circuit with soft start and overcurrent protection functions according to claim 4, characterized in that, When the fan experiences an overcurrent anomaly in its working circuit due to excessive starting instantaneous current, the resistor R8 samples the current in the fan working circuit, causing the base voltage of the triode Q5 to rise. The CE poles of the triode Q5 turn on, and at the same time, the base voltage of the triode Q3 is pulled down, causing the CE pole current of the triode Q3 to decrease, achieving a current limiting effect. At this time, the triodes Q3 and Q5 operate in the amplification region or the cut-off region. When the overcurrent anomaly in the fan's working circuit is eliminated, the resistor R8 samples the current in the fan working circuit, and the base voltage of the triode Q5 drops to turn off the CE poles of the triode Q5. At this time, the base voltage of the triode Q3 rises, and the CE pole current of the triode Q3 rises, achieving the function of current limiting soft start. When the fan is turned on instantaneously, the triode Q3 operates in the saturation region.

8. The control method of a DC fan drive circuit with soft start and overcurrent protection functions according to claim 4, characterized in that, Pin 1 of the fan interface CNF1 is connected to the positive pole of the fan, and pin 2 of the fan interface CNF1 is connected to the negative pole of the fan. The capacitor C1 is a fan power supply filter capacitor, which is used to eliminate voltage dips and overshoots caused by the turning on and off of the fan.

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