Fan power supply circuit and photovoltaic inverter

Abstract

The utility model is applicable to the technical field of inverters, and provides a fan power supply circuit and a photovoltaic inverter, the fan power supply circuit comprises a sampling resistor, a sampling circuit, a judgment signal holding circuit and a driving protection circuit; the first input end of the sampling circuit is connected with one end of the sampling resistor and a power supply, the second input end of the sampling circuit is connected with the other end of the sampling resistor, and the output end of the sampling circuit is connected with the first input end of the judgment signal holding circuit; the second input end of the judgment signal holding circuit receives input reference voltage, and the output end of the judgment signal holding circuit is connected with the first controlled end of the driving protection circuit; the second controlled end of the driving protection circuit receives the input control signal, the input end of the driving protection circuit is connected with a power supply through a sampling resistor, and the output end of the driving protection circuit is connected with a fan. According to the technical scheme, the power supply can be prevented from being damaged due to repeated starting of the power supply circuit when the fan breaks down.

Description

Technical Field

[0001] This utility model belongs to the field of inverter technology, and in particular relates to a fan power supply circuit and a photovoltaic inverter. Background Technology

[0002] With the development of the photovoltaic industry, the single-unit power of photovoltaic inverters is getting larger and larger. String inverters have developed from the original 3KW to the current 350KW, and centralized inverters have developed from the original 500KW to the current 4MW. The larger the single-unit power, the higher the power density, and the greater the heat generated by the inverter itself.

[0003] To ensure the reliable long-term operation of the internal components of the inverter, the heat generated during operation needs to be dissipated to the outside of the inverter. A fan, being a device that converts electrical energy into mechanical energy, can dissipate this heat. However, for the fan to operate, a corresponding power supply circuit is required to provide power. If the power supply circuit is not properly protected, it can easily overload the power supply, leading to a power system failure in the equipment.

[0004] The traditional approach is to use MOSFETs, IGBTs, or transistors as switching devices to power the fan. The voltage drop across the resistor caused by the current is used to detect fan malfunctions and provide protection.

[0005] However, after a traditional protection circuit performs a protection action, the fault current is cut off, the overcurrent signal disappears, and the protection signal also disappears. This leads to the fan repeatedly performing protection actions and then disappearing while in a short-circuit state. If this state lasts for too long, it can easily cause a short circuit in the system power supply or overheating or even fire of the faulty fan. Utility Model Content

[0006] This utility model provides a fan power supply circuit, which aims to solve the problem of repeated starting of the power supply circuit when the fan fails, thus damaging the power supply.

[0007] This utility model embodiment is implemented as follows: a fan power supply circuit, the fan power supply circuit including a sampling resistor, a sampling circuit, a judgment signal holding circuit and a drive protection circuit;

[0008] The first input terminal of the sampling circuit is connected to one end of the sampling resistor and a power supply, the second input terminal of the sampling circuit is connected to the other end of the sampling resistor, and the output terminal of the sampling circuit is connected to the first input terminal of the judgment signal holding circuit.

[0009] The second input terminal of the judgment signal holding circuit receives the input reference voltage, and the output terminal of the judgment signal holding circuit is connected to the first controlled terminal of the drive protection circuit.

[0010] The second controlled terminal of the drive protection circuit receives the input control signal, the input terminal of the drive protection circuit is connected to the power supply through the sampling resistor, and the output terminal of the drive protection circuit is connected to a fan.

[0011] Furthermore, the sampling circuit includes a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a first operational amplifier;

[0012] One end of the second resistor is the first input terminal of the sampling circuit, and the other end of the second resistor is connected to one end of the third resistor and the positive input terminal of the first operational amplifier. The other end of the third resistor is grounded.

[0013] One end of the fourth resistor is the second input terminal of the sampling circuit, and the other end of the fourth resistor is connected to one end of the fifth resistor and the negative input terminal of the first operational amplifier. The output terminal of the first operational amplifier is connected to the other end of the fifth resistor, and the output terminal of the first operational amplifier is the output terminal of the sampling circuit.

[0014] Furthermore, the determination signal holding circuit includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a second operational amplifier;

[0015] One end of the sixth resistor is the first input terminal of the judgment signal holding circuit, and the other end of the sixth resistor is connected to the positive input terminal of the second operational amplifier and one end of the seventh resistor.

[0016] One end of the eighth resistor is the second input terminal of the judgment signal holding circuit, the other end of the eighth resistor is connected to the negative input terminal of the second operational amplifier and one end of the ninth resistor, and the other end of the ninth resistor is grounded.

[0017] The output terminal of the second operational amplifier is the output terminal of the judgment signal holding circuit. The output terminal of the second operational amplifier is connected to the other end of the seventh resistor and one end of the tenth resistor. The other end of the tenth resistor is connected to the power supply.

[0018] Furthermore, the drive protection circuit includes an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a first electron tube, a second electron tube, and a third electron tube;

[0019] One end of the eleventh resistor is the first controlled end of the drive protection circuit, and the other end of the eleventh resistor is connected to the first end of the first electron tube.

[0020] The second end of the first electron tube is connected to one end of the twelfth resistor, one end of the thirteenth resistor, and the first end of the second electron tube. The other end of the twelfth resistor is the second controlled end of the drive protection circuit. The third end of the first electron tube and the other end of the thirteenth resistor are grounded.

[0021] The second end of the second electron tube is connected to one end of the fourteenth resistor and one end of the fifteenth resistor, and the third end of the second electron tube is grounded;

[0022] The other end of the fourteenth resistor is connected to the second end of the third electron tube, which is the input terminal of the drive protection circuit. The first end of the third electron tube is connected to the other end of the fifteenth resistor, and the third end of the third electron tube is the output terminal of the drive protection circuit.

[0023] Furthermore, the first electron tube is an NPN transistor, with the base of the NPN transistor being the first terminal of the first electron tube, the collector of the NPN transistor being the second terminal of the first electron tube, and the emitter of the NPN transistor being the third terminal of the first electron tube.

[0024] Furthermore, the second electron tube is characterized in that the base of the NPN transistor is the first end of the second electron tube, the collector of the NPN transistor is the second end of the second electron tube, and the emitter of the NPN transistor is the third end of the second electron tube.

[0025] Furthermore, the third electron tube is a PNP transistor, with the base of the PNP transistor being the first terminal of the third electron tube, the emitter of the PNP transistor being the second terminal of the third electron tube, and the collector of the PNP transistor being the third terminal of the third electron tube.

[0026] Furthermore, the fan power supply circuit also includes a controller;

[0027] The controller is connected to the second controlled terminal of the drive protection circuit;

[0028] The controller is used to provide control signals to the drive protection circuit.

[0029] Furthermore, the fan power supply circuit also includes a reference voltage source;

[0030] The reference voltage source is connected to the second input terminal of the judgment signal holding circuit;

[0031] The reference voltage source is used to provide a reference voltage for the judgment signal holding circuit.

[0032] This utility model also provides a photovoltaic inverter, which includes a fan and a fan power supply circuit as described in any of the above claims;

[0033] The fan is connected to the output terminal of the drive protection circuit in the fan power supply circuit.

[0034] The technical solution of this utility model involves a sampling circuit acquiring the load current and performing differential processing to generate a sampling signal, which is then sent to a judgment signal holding circuit. In the event of a fan failure, the judgment signal holding circuit generates a shutdown level signal based on the sampling signal and locks this shutdown level signal. The drive protection circuit then performs a shutdown operation based on the shutdown level signal and maintains it in the shutdown state, thus cutting off power to the fan. Because the judgment signal holding circuit can lock the shutdown level signal generated during the fan failure process, keeping the drive protection circuit continuously in the shutdown state, it avoids the power supply circuit repeatedly starting and damaging the power supply during a fan failure. Attached Figure Description

[0035] Figure 1 This is a circuit block diagram of an embodiment of the fan power supply circuit provided by this utility model.

[0036] Figure 2 This is a schematic diagram of the circuit structure of an embodiment of the fan power supply circuit provided by this utility model.

[0037] Figure 3 This is a circuit block diagram of another embodiment of the fan power supply circuit provided by this utility model.

[0038] Figure 4 This is a circuit structure block diagram of another embodiment of the fan power supply circuit provided by this utility model. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0040] The technical solution of this utility model involves sampling the load current through a sampling circuit and generating a sampling signal after differential processing, which is then sent to a judgment signal holding circuit. In the event of a fan failure, the judgment signal holding circuit generates a shutdown level signal based on the sampling signal and locks the shutdown level signal. The drive protection circuit can perform a shutdown operation based on the shutdown level signal and maintain it in the shutdown state, thereby cutting off the power to the fan and preventing the power supply circuit from repeatedly starting and damaging the power supply when the fan fails.

[0041] Example 1

[0042] Reference Figure 1 This utility model provides a fan power supply circuit, which includes a sampling resistor R1, a sampling circuit 10, a judgment signal holding circuit 20, and a drive protection circuit 30. The first input terminal of the sampling circuit 10 is connected to one end of the sampling resistor R1 and a power supply VCC, the second input terminal of the sampling circuit 10 is connected to the other end of the sampling resistor R1, and the output terminal of the sampling circuit 10 is connected to the first input terminal of the judgment signal holding circuit 20.

[0043] The second input terminal of the signal holding circuit 20 receives the input reference voltage. This reference voltage can be provided by an external voltage divider circuit or by a reference voltage source. Of course, it is not limited to these and can be set according to actual needs.

[0044] The output of the signal holding circuit 20 is connected to the first controlled terminal of the drive protection circuit 30; the second controlled terminal of the drive protection circuit 30 receives the input control signal, which can be provided by a controller such as a microprocessor like a microcontroller, DSP, or FPGA. The input of the drive protection circuit 30 is connected to the power supply VCC via a sampling resistor R1, while the output of the drive protection circuit 30 is connected to a fan.

[0045] The sampling circuit 10 can be a single-stage differential proportional operation circuit, a multi-stage differential proportional operation circuit, or other implementable circuit structures, which are not limited here.

[0046] The decision signal holding circuit 20 can be composed of an operational amplifier and a feedback network.

[0047] The drive protection circuit 30 can be composed of switching devices such as MOSFETs, IGBTs, or transistors.

[0048] The working principle of this technical solution is as follows:

[0049] The sampling circuit 10 collects the load current from the sampling resistor R1 connected in series in the main circuit, then performs differential processing on the load current to generate a sampling signal, and transmits the sampling signal to the judgment signal holding circuit 20.

[0050] During normal operation of the circuit, the sampling circuit 10 generates a first sampling signal and transmits it to the judgment signal holding circuit 20. The judgment signal holding circuit 20 generates a conduction level signal based on the first sampling signal and sends it to the drive protection circuit 30. At this time, the drive protection circuit 30 will maintain the conduction state according to the control command of the control signal. The power supply VCC supplies power to the fan through the drive protection circuit 30. The fan runs to dissipate heat from the internal components of the inverter, so that the internal components of the inverter can work stably for a long time.

[0051] When a fan malfunctions, the sampling circuit 10 generates a second sampling signal and transmits it to the judgment signal holding circuit 20. The judgment signal holding circuit 20 generates a shutdown level signal based on this second sampling signal and locks the shutdown level signal. At this time, the drive protection circuit 30 is turned off under the trigger of the shutdown level signal and remains in the shutdown state until the fault is resolved. The on-level signal and the off-level signal have opposite levels; furthermore, the on-level signal is low and the off-level signal is high.

[0052] Since the signal holding circuit 20 can lock the shutdown level signal when the fan fails, the drive protection circuit 30 can perform the shutdown operation and remain in the shutdown state. Therefore, the power supply circuit will not be repeatedly started during the fault process, thus avoiding damage to the power supply due to repeated startup of the power supply circuit when the fan fails, and effectively reducing the risk of damage to the power supply.

[0053] The technical solution of this utility model involves sampling circuit 10 acquiring load current and performing differential processing to generate a sampling signal, which is then sent to judgment signal holding circuit 20. In the event of a fan failure, judgment signal holding circuit 20 generates a shutdown level signal based on the sampling signal and locks the shutdown level signal. The drive protection circuit can perform a shutdown operation based on the shutdown level signal and maintain it in the shutdown state, thus cutting off power to the fan. Since judgment signal holding circuit 20 can lock the shutdown level signal generated during the fan failure process, it can prevent the power supply circuit from repeatedly starting up and damaging the power supply when the fan fails.

[0054] Example 2

[0055] Reference Figure 2 In one specific embodiment, the sampling circuit 10 includes a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and a first operational amplifier U1.

[0056] The connection is as follows: one end of the second resistor R2 is the first input terminal of the sampling circuit 10, that is, one end of the second resistor R2 is connected to one end of the sampling resistor R1, the other end of the second resistor R2 is connected to one end of the third resistor R3 and the positive input terminal of the first operational amplifier U1, and the other end of the third resistor R3 is grounded.

[0057] One end of the fourth resistor R4 is the second input terminal of the sampling circuit 10, that is, one end of the fourth resistor R4 is connected to the other end of the sampling resistor R1. The other end of the fourth resistor R4 is connected to one end of the fifth resistor R5 and the negative input terminal of the first operational amplifier U1. The output terminal of the first operational amplifier U1 is connected to the other end of the fifth resistor R5. The output terminal of the first operational amplifier U1 is the output terminal of the sampling circuit 10, that is, the output terminal of the first operational amplifier U1 is connected to the first input terminal of the judgment signal holding circuit 20.

[0058] The working principle of the sampling circuit is as follows:

[0059] The second resistor R2 and the third resistor R3 divide the voltage of the power supply and use it as the positive input voltage of the first operational amplifier U1. The load current provides voltage to the negative input of the first operational amplifier U1 through the fourth resistor R4.

[0060] The first operational amplifier U1 calculates the difference between its positive and negative input voltages and amplifies it proportionally. Specifically, during normal circuit operation, the first operational amplifier U1 outputs a first sampling signal to the judgment signal holding circuit 20, which generates a conduction level signal accordingly. When the fan malfunctions, the load current increases, and the first operational amplifier U1 outputs a second sampling signal to the judgment signal holding circuit 20, which generates a shutdown level signal and locks the shutdown level signal. In this embodiment, the third resistor R3 is a balancing resistor, and the fifth resistor R5 is a feedback resistor.

[0061] Example 3

[0062] Reference Figure 2 In one specific embodiment, the determination signal holding circuit 20 includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, and a second operational amplifier U2.

[0063] The connection is as follows: one end of the sixth resistor R6 is the first input terminal of the judgment signal holding circuit 20, which is connected to the output terminal of the sampling circuit 10; the other end of the sixth resistor R6 is connected to the positive input terminal of the second operational amplifier U2 and one end of the seventh resistor R7.

[0064] One end of the eighth resistor R8 is the second input terminal of the judgment signal holding circuit 20, and the other end of the eighth resistor R8 is connected to the negative input terminal of the second operational amplifier U2 and one end of the ninth resistor R9. The other end of the ninth resistor R9 is grounded.

[0065] The output terminal of the second operational amplifier U2 is the output terminal of the judgment signal holding circuit 20, which is connected to the first controlled terminal of the drive protection circuit 30; the output terminal of the second operational amplifier U2 is connected to the other end of the seventh resistor R7 and one end of the tenth resistor R10, and the other end of the tenth resistor R10 is connected to the power supply VCC.

[0066] Understandably, since the output of the second operational amplifier U2 is connected to its positive input via the seventh resistor R7, the output of the second operational amplifier U2 is affected by the voltage at its positive input. The voltage at the negative input of the second operational amplifier U2 is obtained by dividing the reference voltage source VREF using the eighth resistor R8 and the ninth resistor R9, and is a fixed voltage value.

[0067] The specific working principle is as follows:

[0068] When the circuit is working normally, the sampling circuit 10 outputs the first sampling signal to the positive input terminal of the second operational amplifier U2. At this time, the voltage at the positive input terminal of the second operational amplifier U2 is less than the voltage at its negative input terminal. The second operational amplifier U2 outputs a conduction level signal, i.e. a low level signal, to the drive protection circuit 30.

[0069] When the fan fails, the load current increases, and the sampling circuit 10 outputs a second sampling signal to the positive input terminal of the second operational amplifier U2. Since the second operational amplifier U2 has extremely high gain, the voltage at the positive input terminal of the second operational amplifier U2 is greater than the voltage at its negative input terminal. The second operational amplifier U2 outputs a turn-off level signal, i.e. a high-level signal, to the drive protection circuit 30.

[0070] Under the feedback effect of the seventh resistor R7, the voltage at the positive input terminal of the second operational amplifier U1 further increases. Therefore, even if the fault phenomenon in the previous stage disappears, the voltage at the positive input terminal of the second operational amplifier U2 is still higher than the voltage at its negative input terminal. The second operational amplifier U2 continuously outputs a shutdown level signal to continuously lock the fault signal and prevent the power supply circuit from repeatedly starting and damaging the power supply during the fan fault process.

[0071] Example 4

[0072] Reference Figure 2 In one specific embodiment, the drive protection circuit 30 includes an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a first electron tube Q1, a second electron tube Q2, and a third electron tube Q3.

[0073] The connection relationship is as follows: one end of the eleventh resistor R11 is the first controlled terminal of the drive protection circuit 40, which is connected to the output terminal of the judgment signal holding circuit 20, and the other end of the eleventh resistor R11 is connected to the first terminal of the first electron tube Q1.

[0074] The second end of the first electron tube Q1 is connected to one end of the twelfth resistor R12, one end of the thirteenth resistor R13, and the first end of the second electron tube Q2. The other end of the twelfth resistor R12 is the second controlled end of the drive protection circuit 30. The third end of the first electron tube Q1 and the other end of the thirteenth resistor R13 are grounded.

[0075] The second terminal of the second electron tube Q2 is connected to one end of the fourteenth resistor R14 and one end of the fifteenth resistor R15, and the third terminal of the second electron tube Q2 is grounded.

[0076] The other end of the fourteenth resistor R14 is connected to the second end of the third electron tube Q3, which is the input terminal of the drive protection circuit 30. The first end of the third electron tube Q3 is connected to the other end of the fifteenth resistor R15, and the third end of the third electron tube Q3 is the output terminal of the drive protection circuit 30, which is connected to the fan.

[0077] The specific working principle is as follows:

[0078] When the circuit is operating normally, the signal holding circuit 20 outputs a low-level signal to the first vacuum tube Q1, causing Q1 to turn off. When Q1 is off, Q2 turns on according to the controller's control signal FAN_DRV, and Q3 also turns on, supplying power to the fan via the third vacuum tube Q3.

[0079] When the fan malfunctions, the signal holding circuit 20 outputs a high-level signal (off level) to the first vacuum tube Q1, causing Q1 to conduct. When Q1 is on, the level at the first terminal of the second vacuum tube Q2 is pulled low, turning Q2 off. At the same time, the third vacuum tube Q3 also turns off, thus stopping the power supply VCC from supplying power to the fan, thereby protecting the power supply.

[0080] Example 5

[0081] Reference Figure 2 In one specific embodiment, the first electron tube Q1 is an NPN transistor, wherein the base of the NPN transistor is the first terminal of the first electron tube Q1, the collector of the NPN transistor is the second terminal of the first electron tube Q1, and the emitter of the NPN transistor is the third terminal of the first electron tube Q1.

[0082] The second electron tube Q2 is an NPN transistor. The base of the NPN transistor is the first terminal of the second electron tube Q2, the collector of the NPN transistor is the second terminal of the second electron tube Q2, and the emitter of the NPN transistor is the third terminal of the second electron tube Q2.

[0083] The third electron tube Q3 is a PNP transistor. The base of the PNP transistor is the first terminal of the third electron tube Q3, the emitter of the PNP transistor is the second terminal of the third electron tube Q3, and the collector of the PNP transistor is the third terminal of the third electron tube Q3.

[0084] To more clearly illustrate the technical concept of this utility model, the following will be used as an example. Figure 2 Explanation of the overall concept:

[0085] The sampling circuit 10 collects the load current from the sampling resistor R1 connected in series in the main circuit. When the circuit is working normally, the first operational amplifier U1 outputs the first sampling signal to the positive input terminal of the second operational amplifier U2. At this time, the voltage at the positive input terminal of the second operational amplifier U2 is less than the voltage at its negative input terminal, and the output terminal of the second operational amplifier U2 is at a low level. At this time, the NPN transistor Q1 is turned off, and the NPN transistor Q2 is turned on according to the control signal of the controller. When the NPN transistor Q2 is turned on, the PNP transistor Q3 is also turned on, and the power supply VCC supplies power to the fan through the PNP transistor Q3.

[0086] When the fan fails, the load current increases. The first operational amplifier U1 outputs a second sampling signal to the positive input of the second operational amplifier U2. Utilizing the extremely high gain of the second operational amplifier U2, the voltage at the positive input of the second operational amplifier U2 is greater than the voltage at its negative input. The output of the second operational amplifier U2 is a high-level signal. At this time, the NPN transistor Q1 is turned on. The turn-on of the NPN transistor Q1 will pull the base of the NPN transistor Q2 low, and the NPN transistor Q2 will turn off. When the NPN transistor Q2 is turned off, the PNP transistor Q3 will also turn off, and the power supply VCC will stop supplying power to the fan.

[0087] During the process, under the feedback effect of the seventh resistor R7, the voltage at the positive input terminal of the second operational amplifier U1 further increases. Therefore, even if the fault phenomenon in the previous stage disappears, the voltage at the positive input terminal of the second operational amplifier U2 is still higher than the voltage at its negative input terminal. The second operational amplifier U2 continuously outputs a high level, locking the fault signal. Then, during the fault process, NPN transistor Q1 continues to conduct, while NPN transistor Q2 and PNP transistor Q3 continue to be turned off until the fault is resolved. In this way, the power supply circuit can be repeatedly started and damaged when the fan fails.

[0088] Example 6

[0089] Reference Figure 3 In one specific embodiment, the fan power supply circuit further includes a controller 40; the controller 40 is connected to the second controlled terminal of the drive protection circuit 20.

[0090] The controller 40 is used to provide control signals to the drive protection circuit 30. In this embodiment, the controller 40 can be a microprocessor such as a microcontroller, DSP, or FPGA, and is not limited thereto.

[0091] Example 7

[0092] Reference Figure 4 The fan power supply circuit also includes a reference voltage source 50, which is connected to the second input terminal of the judgment signal holding circuit 20.

[0093] The reference voltage source 50 is used to provide a reference voltage signal for the decision signal holding circuit 20.

[0094] This utility model also provides a photovoltaic inverter, which includes a fan and a fan power supply circuit as described in any of the preceding claims. The fan is connected to the output terminal of the drive protection circuit in the fan power supply circuit. The detailed structure of the fan power supply circuit can be found in the above embodiments and will not be repeated here. It is understood that since the above-mentioned fan power supply circuit is used in the photovoltaic inverter of this utility model, the embodiments of the photovoltaic inverter of this utility model include all the technical solutions of all the embodiments of the above-mentioned fan power supply circuit, and the achieved technical effects are completely the same, and will not be repeated here.

[0095] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A fan power supply circuit, characterized in that, The fan power supply circuit includes a sampling resistor, a sampling circuit, a judgment signal holding circuit, and a drive protection circuit. The first input terminal of the sampling circuit is connected to one end of the sampling resistor and a power supply, the second input terminal of the sampling circuit is connected to the other end of the sampling resistor, and the output terminal of the sampling circuit is connected to the first input terminal of the judgment signal holding circuit. The second input terminal of the judgment signal holding circuit receives the input reference voltage, and the output terminal of the judgment signal holding circuit is connected to the first controlled terminal of the drive protection circuit. The second controlled terminal of the drive protection circuit receives the input control signal, the input terminal of the drive protection circuit is connected to the power supply through the sampling resistor, and the output terminal of the drive protection circuit is connected to a fan.

2. The fan power supply circuit as described in claim 1, characterized in that, The sampling circuit includes a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a first operational amplifier; One end of the second resistor is the first input terminal of the sampling circuit, and the other end of the second resistor is connected to one end of the third resistor and the positive input terminal of the first operational amplifier. The other end of the third resistor is grounded. One end of the fourth resistor is the second input terminal of the sampling circuit, and the other end of the fourth resistor is connected to one end of the fifth resistor and the negative input terminal of the first operational amplifier. The output terminal of the first operational amplifier is connected to the other end of the fifth resistor, and the output terminal of the first operational amplifier is the output terminal of the sampling circuit.

3. The fan power supply circuit as described in claim 1, characterized in that, The judgment signal holding circuit includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a second operational amplifier; One end of the sixth resistor is the first input terminal of the judgment signal holding circuit, and the other end of the sixth resistor is connected to the positive input terminal of the second operational amplifier and one end of the seventh resistor. One end of the eighth resistor is the second input terminal of the judgment signal holding circuit, the other end of the eighth resistor is connected to the negative input terminal of the second operational amplifier and one end of the ninth resistor, and the other end of the ninth resistor is grounded. The output terminal of the second operational amplifier is the output terminal of the judgment signal holding circuit. The output terminal of the second operational amplifier is connected to the other end of the seventh resistor and one end of the tenth resistor. The other end of the tenth resistor is connected to the power supply.

4. The fan power supply circuit as described in claim 1, characterized in that, The drive protection circuit includes an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a first electron tube, a second electron tube, and a third electron tube; One end of the eleventh resistor is the first controlled end of the drive protection circuit, and the other end of the eleventh resistor is connected to the first end of the first electron tube. The second end of the first electron tube is connected to one end of the twelfth resistor, one end of the thirteenth resistor, and the first end of the second electron tube. The other end of the twelfth resistor is the second controlled end of the drive protection circuit. The third end of the first electron tube and the other end of the thirteenth resistor are grounded. The second end of the second electron tube is connected to one end of the fourteenth resistor and one end of the fifteenth resistor, and the third end of the second electron tube is grounded; The other end of the fourteenth resistor is connected to the second end of the third electron tube, which is the input terminal of the drive protection circuit. The first end of the third electron tube is connected to the other end of the fifteenth resistor, and the third end of the third electron tube is the output terminal of the drive protection circuit.

5. The fan power supply circuit as described in claim 4, characterized in that, The first electron tube is an NPN transistor, with the base of the NPN transistor being the first terminal of the first electron tube, the collector of the NPN transistor being the second terminal of the first electron tube, and the emitter of the NPN transistor being the third terminal of the first electron tube.

6. The fan power supply circuit as described in claim 4, characterized in that, The second electron tube is an NPN transistor, with the base of the NPN transistor being the first terminal of the second electron tube, the collector of the NPN transistor being the second terminal of the second electron tube, and the emitter of the NPN transistor being the third terminal of the second electron tube.

7. The fan power supply circuit as described in claim 4, characterized in that, The third electron tube is a PNP transistor, with the base of the PNP transistor being the first terminal, the emitter of the PNP transistor being the second terminal, and the collector of the PNP transistor being the third terminal.

8. The fan power supply circuit as described in claim 1, characterized in that, The fan power supply circuit also includes a controller; The controller is connected to the second controlled terminal of the drive protection circuit; The controller is used to provide control signals to the drive protection circuit.

9. The fan power supply circuit as described in any one of claims 1-8, characterized in that, The fan power supply circuit also includes a reference voltage source; The reference voltage source is connected to the second input terminal of the judgment signal holding circuit; The reference voltage source is used to provide a reference voltage for the judgment signal holding circuit.

10. A photovoltaic inverter, characterized in that, The photovoltaic inverter includes a fan and a fan power supply circuit as described in any one of claims 1-9; The fan is connected to the output terminal of the drive protection circuit in the fan power supply circuit.

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