Inverter cooling fan speed regulation circuit

Abstract

The utility model relates to the technical field of inverters, in particular to a speed regulation circuit for a cooling fan of an inverter, which comprises an operational amplifier U16 and a step-down conversion chip U14, the normal phase input end of the operational amplifier U16 is electrically connected with the PWM signal end of an external controller, and the normal phase input end of the operational amplifier U16 is electrically connected with the PWM signal end of the external controller. The output end of the operational amplifier U16 is electrically connected with the inverted input end of the operational amplifier U16 and the voltage sampling end of the step-down conversion chip U14, and the signal output end of the step-down conversion chip U14 is electrically connected with the inverter cooling fan, so that the rotating speed of the inverter cooling fan can be controlled by regulating and controlling the duty ratio of the PWM signal end of the controller.

Description

Technical Field

[0001] The utility model relates to the technical field of inverters, in particular to a speed regulating circuit of a cooling fan of an inverter. Background Art

[0002] After continuous updates and iterations, the high efficiency and low noise of photovoltaic storage inverters are increasingly valued by customers. Photovoltaic storage inverters generate a lot of heat when using power conversion devices, and need to rely on the rotation of fans to take away the heat to avoid continuous high temperature damage to components. At present, in order to be able to adjust the fan speed, the inverter generally uses a fan speed control circuit (generally by designing a BUCK type circuit composed of transistors, resistors and capacitors) to intelligently adjust the fan speed; in the BUCK type circuit, it generally includes a power stage circuit and a control circuit. The control circuit is used to control the switching state of the main power switch tube of the power stage circuit to adjust the output voltage so that the output voltage is lower than the input voltage. The control circuit needs to feedback and control the switching state of the main power switch tube according to the change of the output voltage.

[0003] However, most of the existing BUCK type circuits (step-down conversion circuits) use voltage mode and peak current mode control methods. These control methods are linear control. The bandwidth of the loop is limited by the switching frequency, and the switching frequency is limited by the efficiency. Therefore, the dynamic response speed is difficult to improve and the power consumption is large. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide an inverter cooling fan speed regulating circuit, which can control the rotation speed of the fan, thereby not only reducing power consumption but also reducing high noise time.

[0005] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0006] An inverter cooling fan speed control circuit includes an operational amplifier U16 and a buck conversion chip U14, wherein the non-phase input terminal of the operational amplifier U16 is electrically connected to the PWM signal terminal of an external controller, the output terminal of the operational amplifier U16 is electrically connected to the inverting input terminal of the operational amplifier U16 and the voltage sampling terminal of the buck conversion chip U14, respectively, and the signal output terminal of the buck conversion chip U14 is electrically connected to the inverter cooling fan.

[0007] Furthermore, the operational amplifier U16 includes a first-stage voltage follower U16A and a second-stage voltage follower U16B, the non-phase input terminal of the first-stage voltage follower U16A is electrically connected to the PWM signal terminal of the peripheral controller, the output terminal of the first-stage voltage follower U16A is electrically connected to the inverting input terminal of the first-stage voltage follower U16A and the non-phase input terminal of the second-stage voltage follower U16B, respectively, the inverting input terminal of the second-stage voltage follower U16B is electrically connected to the output terminal of the second-stage voltage follower U16B, and the output terminal of the second-stage voltage follower U16B is electrically connected to the voltage sampling terminal of the buck conversion chip U14.

[0008] Furthermore, it also includes a transistor Q1 and a photocoupler U15, the base of the transistor Q1 is electrically connected to the PWM signal end of the external controller, the collector of the transistor Q1 is electrically connected to the second pin of the photocoupler U15, the emitter of the transistor Q1 is grounded, the first pin of the photocoupler U15 is connected to the first power supply, the third pin of the photocoupler U15 is electrically connected to the non-phase input end of the first-stage voltage follower U16A, and the fourth pin of the photocoupler U15 is connected to the second power supply.

[0009] Furthermore, it also includes a resistor R270 and a capacitor C46, ​​one end of the resistor R270 is electrically connected to the third pin of the photocoupler U15, the other end of the resistor R270 is electrically connected to one end of the capacitor C46 and the non-phase input end of the first-stage voltage follower U16A, and the other end of the capacitor C46 is grounded.

[0010] Furthermore, it also includes a resistor R274 and a resistor R276, one end of the resistor R274 is electrically connected to the output end of the first-stage voltage follower U16A, the other end of the resistor R274 is electrically connected to one end of the resistor R276 and the non-phase input end of the second-stage voltage follower U16B respectively, and the other end of the resistor R276 is grounded.

[0011] Furthermore, it also includes a resistor R264 and a resistor R44, one end of the resistor R264 is electrically connected to the PWM signal end of the external controller, the other end of the resistor R264 is electrically connected to the base of the transistor Q1 and one end of the resistor R44 respectively, the other end of the resistor R44 is electrically connected to the emitter of the transistor Q1 and the other end of the resistor R44 is grounded.

[0012] Furthermore, a resistor R265 is included, one end of the resistor R265 is connected to the first power supply, and the other end of the resistor R265 is electrically connected to the first pin of the photocoupler U15.

[0013] Furthermore, it also includes a resistor R271 and a resistor R273, one end of the resistor R271 is grounded, the other end of the resistor R271 is electrically connected to one end of the resistor R273 and the inverting input end of the first-stage voltage follower U16A respectively, and the other end of the resistor R273 is electrically connected to the output end of the first-stage voltage follower U16A.

[0014] Furthermore, it also includes a resistor R272, one end of which is electrically connected to the output end of the operational amplifier U16, and the other end of which is electrically connected to the voltage sampling end of the buck conversion chip U14.

[0015] Furthermore, it also includes a resistor R268, one end of which is electrically connected to the output end of the operational amplifier U16 and the voltage sampling end of the buck conversion chip U14, and the other end of the resistor R268 is electrically connected to the signal output end of the buck conversion chip U14 and the inverter cooling fan.

[0016] The beneficial effects of the utility model are:

[0017] The speed regulation circuit designed in this scheme includes an operational amplifier U16 and a buck converter chip U14. The non-phase input terminal of the operational amplifier U16 is electrically connected to the PWM signal terminal of the external controller, and the output terminal of the operational amplifier U16 is electrically connected to the inverting input terminal of the operational amplifier U16 and the voltage sampling terminal of the buck converter chip U14 respectively. The signal output by the PWM signal terminal of the controller passes through the operational amplifier U16. Since at any time, the sum of the currents flowing into any node in the circuit is always equal to the sum of the currents flowing out of the node, the output voltage of the output terminal of the operational amplifier U16 can be regulated by adjusting the duty cycle of the PWM signal terminal of the controller. The output voltage of the output terminal of the operational amplifier U16 is regulated by adjusting the duty cycle of the PWM signal terminal of the controller. The output voltage passes through the voltage sampling end of the buck conversion chip U14 and is output from the output end of the buck conversion chip U14. The buck conversion chip U14 can convert the input voltage into a stable output voltage. Since the signal output end of the buck conversion chip U14 is electrically connected to the inverter cooling fan, the speed of the inverter cooling fan can be controlled by adjusting the duty cycle of the PWM signal end of the controller. This solution controls the speed of the inverter cooling fan by adjusting the duty cycle of the PWM signal end of the controller and then adjusting the size of the operational amplifier node current, which can not only reduce power consumption but also reduce high noise time. Moreover, its circuit is simpler, cost-effective, has a long service life, and is more reliable in application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The utility model is a circuit schematic diagram of the inverter cooling fan speed regulating circuit. DETAILED DESCRIPTION

[0019] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0020] Please refer to Figure 1 , the technical solution adopted by the utility model is:

[0021] An inverter cooling fan speed control circuit includes an operational amplifier U16 and a buck conversion chip U14, wherein the non-phase input terminal of the operational amplifier U16 is electrically connected to the PWM signal terminal of an external controller, the output terminal of the operational amplifier U16 is electrically connected to the inverting input terminal of the operational amplifier U16 and the voltage sampling terminal of the buck conversion chip U14, respectively, and the signal output terminal of the buck conversion chip U14 is electrically connected to the inverter cooling fan.

[0022] From the above description, it can be seen that the beneficial effects of the utility model are:

[0023] The speed regulation circuit designed in this scheme includes an operational amplifier U16 and a buck converter chip U14. The non-phase input terminal of the operational amplifier U16 is electrically connected to the PWM signal terminal of the external controller, and the output terminal of the operational amplifier U16 is electrically connected to the inverting input terminal of the operational amplifier U16 and the voltage sampling terminal of the buck converter chip U14 respectively. The signal output by the PWM signal terminal of the controller passes through the operational amplifier U16. Since at any time, the sum of the currents flowing into any node in the circuit is always equal to the sum of the currents flowing out of the node, the output voltage of the output terminal of the operational amplifier U16 can be regulated by adjusting the duty cycle of the PWM signal terminal of the controller. The output voltage of the output terminal of the operational amplifier U16 is regulated by adjusting the duty cycle of the PWM signal terminal of the controller. The output voltage passes through the voltage sampling end of the buck conversion chip U14 and is output from the output end of the buck conversion chip U14. The buck conversion chip U14 can convert the input voltage into a stable output voltage. Since the signal output end of the buck conversion chip U14 is electrically connected to the inverter cooling fan, the speed of the inverter cooling fan can be controlled by adjusting the duty cycle of the PWM signal end of the controller. This solution controls the speed of the inverter cooling fan by adjusting the duty cycle of the PWM signal end of the controller and then adjusting the size of the operational amplifier node current, which can not only reduce power consumption but also reduce high noise time. Moreover, its circuit is simpler, cost-effective, has a long service life, and is more reliable in application.

[0024] Furthermore, the operational amplifier U16 includes a first-stage voltage follower U16A and a second-stage voltage follower U16B, the non-phase input terminal of the first-stage voltage follower U16A is electrically connected to the PWM signal terminal of the peripheral controller, the output terminal of the first-stage voltage follower U16A is electrically connected to the inverting input terminal of the first-stage voltage follower U16A and the non-phase input terminal of the second-stage voltage follower U16B, respectively, the inverting input terminal of the second-stage voltage follower U16B is electrically connected to the output terminal of the second-stage voltage follower U16B, and the output terminal of the second-stage voltage follower U16B is electrically connected to the voltage sampling terminal of the buck conversion chip U14.

[0025] Furthermore, it also includes a transistor Q1 and a photocoupler U15, the base of the transistor Q1 is electrically connected to the PWM signal end of the external controller, the collector of the transistor Q1 is electrically connected to the second pin of the photocoupler U15, the emitter of the transistor Q1 is grounded, the first pin of the photocoupler U15 is connected to the first power supply, the third pin of the photocoupler U15 is electrically connected to the non-phase input end of the first-stage voltage follower U16A, and the fourth pin of the photocoupler U15 is connected to the second power supply.

[0026] From the above description, it can be seen that the transistor Q1 is set to play the role of control signal, and the photocoupler U15 plays the role of isolation.

[0027] Furthermore, it also includes a resistor R270 and a capacitor C46, ​​one end of the resistor R270 is electrically connected to the third pin of the photocoupler U15, the other end of the resistor R270 is electrically connected to one end of the capacitor C46 and the non-phase input end of the first-stage voltage follower U16A, and the other end of the capacitor C46 is grounded.

[0028] It can be seen from the above description that by setting the resistor R270 and the capacitor C46, ​​the inverting input terminal of the operational amplifier U16 can be made to have a stable voltage.

[0029] Furthermore, it also includes a resistor R274 and a resistor R276, one end of the resistor R274 is electrically connected to the output end of the first-stage voltage follower U16A, the other end of the resistor R274 is electrically connected to one end of the resistor R276 and the non-phase input end of the second-stage voltage follower U16B respectively, and the other end of the resistor R276 is grounded.

[0030] From the above description, it can be seen that the resistors R274 and R276 are set to play a role of voltage division.

[0031] Furthermore, it also includes a resistor R264 and a resistor R44, one end of the resistor R264 is electrically connected to the PWM signal end of the external controller, the other end of the resistor R264 is electrically connected to the base of the transistor Q1 and one end of the resistor R44 respectively, the other end of the resistor R44 is electrically connected to the emitter of the transistor Q1 and the other end of the resistor R44 is grounded.

[0032] It can be seen from the above description that the resistor R264 and the resistor R44 can play the role of current limiting and preventing false triggering.

[0033] Furthermore, a resistor R265 is included, one end of the resistor R265 is connected to the first power supply, and the other end of the resistor R265 is electrically connected to the first pin of the photocoupler U15.

[0034] From the above description, it can be seen that setting the resistor R265 plays a role in current limiting.

[0035] Furthermore, it also includes a resistor R271 and a resistor R273, one end of the resistor R271 is grounded, the other end of the resistor R271 is electrically connected to one end of the resistor R273 and the inverting input end of the first-stage voltage follower U16A respectively, and the other end of the resistor R273 is electrically connected to the output end of the first-stage voltage follower U16A.

[0036] It can be seen from the above description that the resistor R271 and the resistor R273 are pull-down resistors.

[0037] Furthermore, it also includes a resistor R272, one end of which is electrically connected to the output end of the operational amplifier U16, and the other end of which is electrically connected to the voltage sampling end of the buck conversion chip U14.

[0038] From the above description, it can be seen that the resistor R272 can adjust the output current of the node (the output end of the operational amplifier U16).

[0039] Furthermore, it also includes a resistor R268, one end of which is electrically connected to the output end of the operational amplifier U16 and the voltage sampling end of the buck conversion chip U14, and the other end of the resistor R268 is electrically connected to the signal output end of the buck conversion chip U14 and the inverter cooling fan.

[0040] From the above description, it can be known that the resistor R268 can adjust the output voltage of the signal output terminal of the buck converter chip U14.

[0041] Please refer to Figure 1 , Embodiment 1 of the present utility model is:

[0042] An inverter cooling fan speed control circuit includes an operational amplifier U16 and a buck conversion chip U14, wherein the non-phase input terminal of the operational amplifier U16 is electrically connected to the PWM signal terminal of an external controller, the output terminal of the operational amplifier U16 is electrically connected to the inverting input terminal of the operational amplifier U16 and the voltage sampling terminal of the buck conversion chip U14, respectively, and the signal output terminal of the buck conversion chip U14 is electrically connected to the inverter cooling fan.

[0043] The operational amplifier U16 includes a first-stage voltage follower U16A and a second-stage voltage follower U16B, the non-phase input terminal of the first-stage voltage follower U16A is electrically connected to the PWM signal terminal of the peripheral controller, the output terminal of the first-stage voltage follower U16A is electrically connected to the inverting input terminal of the first-stage voltage follower U16A and the non-phase input terminal of the second-stage voltage follower U16B respectively, the inverting input terminal of the second-stage voltage follower U16B is electrically connected to the output terminal of the second-stage voltage follower U16B, and the output terminal of the second-stage voltage follower U16B is electrically connected to the voltage sampling terminal of the buck conversion chip U14.

[0044] It also includes a transistor Q1 and a photocoupler U15, wherein the base of the transistor Q1 is electrically connected to the PWM signal end of the peripheral controller, the collector of the transistor Q1 is electrically connected to the second pin of the photocoupler U15, the emitter of the transistor Q1 is grounded, the first pin of the photocoupler U15 is connected to the first power supply, the third pin of the photocoupler U15 is electrically connected to the non-phase input end of the first-stage voltage follower U16A, and the fourth pin of the photocoupler U15 is connected to the second power supply.

[0045] It also includes a resistor R270 and a capacitor C46, ​​one end of the resistor R270 is electrically connected to the third pin of the photocoupler U15, the other end of the resistor R270 is electrically connected to one end of the capacitor C46 and the non-phase input end of the first-stage voltage follower U16A, and the other end of the capacitor C46 is grounded.

[0046] It also includes a resistor R274 and a resistor R276, one end of the resistor R274 is electrically connected to the output end of the first-stage voltage follower U16A, the other end of the resistor R274 is electrically connected to one end of the resistor R276 and the non-phase input end of the second-stage voltage follower U16B respectively, and the other end of the resistor R276 is grounded.

[0047] It also includes a resistor R264 and a resistor R44, one end of the resistor R264 is electrically connected to the PWM signal end of the external controller, the other end of the resistor R264 is electrically connected to the base of the transistor Q1 and one end of the resistor R44 respectively, the other end of the resistor R44 is electrically connected to the emitter of the transistor Q1 and the other end of the resistor R44 is grounded.

[0048] It also includes a resistor R265, one end of which is connected to the first power supply, and the other end of which is electrically connected to the first pin of the photocoupler U15.

[0049] It also includes a resistor R271 and a resistor R273, one end of the resistor R271 is grounded, the other end of the resistor R271 is electrically connected to one end of the resistor R273 and the inverting input end of the first-stage voltage follower U16A respectively, and the other end of the resistor R273 is electrically connected to the output end of the first-stage voltage follower U16A.

[0050] It also includes a resistor R272, one end of which is electrically connected to the output end of the operational amplifier U16, and the other end of which is electrically connected to the voltage sampling end of the buck conversion chip U14.

[0051] It also includes a resistor R268, one end of which is electrically connected to the output end of the operational amplifier U16 and the voltage sampling end of the buck converter chip U14, and the other end of which is electrically connected to the signal output end of the buck converter chip U14 and the inverter cooling fan.

[0052] The inverter cooling fan speed control circuit also includes a resistor R269, a capacitor C48, a capacitor C90, a capacitor C91, a resistor R275, a capacitor C19, a diode D18, an inductor L6, a resistor R266, a resistor R267, a capacitor C92, a capacitor C93 and a capacitor C20. For the specific connection relationship between the components, please refer to Figure 1 .

[0053] The working principle of the inverter cooling fan speed control circuit mentioned above is:

[0054] The PWM_FAN signal is connected to the base of the transistor Q1 through the resistor R264. When PWM_FAN is at a high level, the first power supply (+5.0VP) is connected through the resistor R265 and the first pin, the second pin and the transistor Q1 of the photocoupler U15, so that the third pin and the fourth pin of the photocoupler U15 are turned on; at this time, the second power supply (+15V) is charged through the third pin of the photocoupler U15, the fourth pin of the photocoupler U15, the resistor R270 and the capacitor C46. The larger the PWM_FAN duty cycle, the higher the voltage across the capacitor C46; according to the virtual short principle of the operational amplifier, the voltage of the third pin and the second pin of the operational amplifier U16 are equal, and the voltage follower composed of the second pin of the operational amplifier U16, the resistor R273 and the resistor R271 can obtain the voltage of the first pin of the operational amplifier U16; through the resistor R27 4 and the resistor R276 can be divided to obtain the voltage of the fifth pin of the operational amplifier U16. According to the virtual short principle of the operational amplifier, the voltage of the sixth pin of the operational amplifier U16 can be obtained. Since the sixth pin and the seventh pin of the operational amplifier U16 are connected, the voltage of the seventh pin of the operational amplifier U16 can be obtained; the model of the buck conversion chip U14 is TPS5430DDAR, which is a DC-DC buck converter. The voltage of the voltage sampling end (i.e., the fourth pin) of the buck conversion chip U14 is fixed at 1.2V. At any time, the sum of the currents flowing into any node in the circuit is always equal to the sum of the currents flowing out of the node. The voltage of the seventh pin of the operational amplifier U16 controls the current flowing through the resistor R272, thereby controlling the current flowing through the resistor R268, thereby achieving the purpose of controlling VCCFAN, and then controlling the speed of the inverter cooling fan.

[0055] The specific control methods are as follows:

[0056] When the inverter detects that the radiator temperature is less than 50°C, it starts the wind speed at level 0, that is, by adjusting the duty cycle of the PWM_FAN signal to D1, the voltage of VCCFAN is controlled to 0V;

[0057] When the inverter detects that the radiator temperature is greater than 50°C, it starts the wind speed 1, that is, by adjusting the duty cycle of the PWM_FAN signal to D2, the voltage of VCCFAN is controlled to 8V;

[0058] When the inverter detects that the radiator temperature is greater than 60°C, it starts the wind speed 2, that is, by adjusting the duty cycle of the PWM_FAN signal to D3, the voltage of VCCFAN is controlled to 9.6V;

[0059] When the inverter detects that the radiator temperature is greater than 70°C, it starts the wind speed 3, that is, by adjusting the duty cycle of the PWM_FAN signal to D4, the voltage of VCCFAN is controlled to 12.2V;

[0060] When the inverter heat sink drops from more than 70°C to less than 68°C for more than 30s, the VCCFAN voltage is controlled to 9.6V by adjusting the duty cycle of the PWM_FAN signal to D3;

[0061] When the inverter heat sink drops from more than 60°C to less than 58°C for more than 30s, the VCCFAN voltage is controlled to 8V by adjusting the duty cycle of the PWM_FAN signal to D2;

[0062] When the inverter heat sink drops from more than 50°C to less than 48°C for more than 30s, the voltage of VCCFAN is controlled to 0V by adjusting the duty cycle of the PWM_FAN signal to D1.

[0063] In summary, the utility model provides an inverter cooling fan speed control circuit, including an operational amplifier U16 and a buck conversion chip U14, the non-phase input terminal of the operational amplifier U16 is electrically connected to the PWM signal terminal of the external controller, the output terminal of the operational amplifier U16 is electrically connected to the inverting input terminal of the operational amplifier U16 and the voltage sampling terminal of the buck conversion chip U14, respectively, the signal output by the PWM signal terminal of the controller passes through the operational amplifier U16, at any time, the sum of the currents flowing into any node in the circuit is always equal to the sum of the currents flowing out of the node, therefore, the output voltage of the output terminal of the operational amplifier U16 can be controlled by adjusting the duty cycle of the PWM signal terminal of the controller, the operational amplifier The output voltage at the output end of U16 passes through the voltage sampling end of the buck converter chip U14 and is output from the output end of the buck converter chip U14. The buck converter chip U14 can convert the input voltage into a stable output voltage. Since the signal output end of the buck converter chip U14 is electrically connected to the inverter cooling fan, the speed of the inverter cooling fan can be controlled by adjusting the duty cycle of the PWM signal end of the controller. This solution controls the speed of the inverter cooling fan by adjusting the duty cycle of the PWM signal end of the controller and then adjusting the size of the operational amplifier node current, which can not only reduce power consumption but also reduce high noise time. Moreover, its circuit is simpler, cost-effective, has a longer service life, and is more reliable in application.

[0064] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical field, are also included in the patent protection scope of the present invention.

Claims

1. An inverter cooling fan speed control circuit, It is characterized in that It includes an operational amplifier U16 and a buck conversion chip U14, wherein the non-phase input terminal of the operational amplifier U16 is electrically connected to the PWM signal terminal of the peripheral controller, the output terminal of the operational amplifier U16 is electrically connected to the inverting input terminal of the operational amplifier U16 and the voltage sampling terminal of the buck conversion chip U14 respectively, and the signal output terminal of the buck conversion chip U14 is electrically connected to the inverter cooling fan.

2. The inverter cooling fan speed regulating circuit according to claim 1, It is characterized in that The operational amplifier U16 includes a first-stage voltage follower U16A and a second-stage voltage follower U16B, the non-phase input terminal of the first-stage voltage follower U16A is electrically connected to the PWM signal terminal of the peripheral controller, the output terminal of the first-stage voltage follower U16A is electrically connected to the inverting input terminal of the first-stage voltage follower U16A and the non-phase input terminal of the second-stage voltage follower U16B respectively, the inverting input terminal of the second-stage voltage follower U16B is electrically connected to the output terminal of the second-stage voltage follower U16B, and the output terminal of the second-stage voltage follower U16B is electrically connected to the voltage sampling terminal of the buck conversion chip U14.

3. The inverter cooling fan speed regulating circuit according to claim 2, It is characterized in that It also includes a transistor Q1 and a photocoupler U15, wherein the base of the transistor Q1 is electrically connected to the PWM signal end of the peripheral controller, the collector of the transistor Q1 is electrically connected to the second pin of the photocoupler U15, the emitter of the transistor Q1 is grounded, the first pin of the photocoupler U15 is connected to the first power supply, the third pin of the photocoupler U15 is electrically connected to the non-phase input end of the first-stage voltage follower U16A, and the fourth pin of the photocoupler U15 is connected to the second power supply.

4. The inverter cooling fan speed regulating circuit according to claim 3, It is characterized in that It also includes a resistor R270 and a capacitor C46, ​​one end of the resistor R270 is electrically connected to the third pin of the photocoupler U15, the other end of the resistor R270 is electrically connected to one end of the capacitor C46 and the non-phase input end of the first-stage voltage follower U16A, and the other end of the capacitor C46 is grounded.

5. The inverter cooling fan speed regulating circuit according to claim 3, It is characterized in that It also includes a resistor R274 and a resistor R276, one end of the resistor R274 is electrically connected to the output end of the first-stage voltage follower U16A, the other end of the resistor R274 is electrically connected to one end of the resistor R276 and the non-phase input end of the second-stage voltage follower U16B respectively, and the other end of the resistor R276 is grounded.

6. The inverter cooling fan speed regulating circuit according to claim 3, It is characterized in that It also includes a resistor R264 and a resistor R44, one end of the resistor R264 is electrically connected to the PWM signal end of the external controller, the other end of the resistor R264 is electrically connected to the base of the transistor Q1 and one end of the resistor R44 respectively, the other end of the resistor R44 is electrically connected to the emitter of the transistor Q1 and the other end of the resistor R44 is grounded.

7. The inverter cooling fan speed regulating circuit according to claim 3, It is characterized in that It also includes a resistor R265, one end of which is connected to the first power supply, and the other end of which is electrically connected to the first pin of the photocoupler U15.

8. The inverter cooling fan speed regulating circuit according to claim 2, It is characterized in that It also includes a resistor R271 and a resistor R273, one end of the resistor R271 is grounded, the other end of the resistor R271 is electrically connected to one end of the resistor R273 and the inverting input end of the first-stage voltage follower U16A respectively, and the other end of the resistor R273 is electrically connected to the output end of the first-stage voltage follower U16A.

9. The inverter cooling fan speed regulating circuit according to claim 1, It is characterized in that It also includes a resistor R272, one end of which is electrically connected to the output end of the operational amplifier U16, and the other end of which is electrically connected to the voltage sampling end of the buck conversion chip U14.

10. The inverter cooling fan speed regulating circuit according to claim 1, It is characterized in that It also includes a resistor R268, one end of which is electrically connected to the output end of the operational amplifier U16 and the voltage sampling end of the buck converter chip U14, and the other end of which is electrically connected to the signal output end of the buck converter chip U14 and the inverter cooling fan.

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