Inverter key detection system based on pi-type filtering and flyback isolation feedback

Abstract

The invention belongs to the technical field of inverter man-machine interaction and power supply feedback control, and discloses an inverter key detection system based on pi-type filtering and flyback isolation feedback, which comprises an external mechanical switch module, a flyback power supply circuit module, a flyback power supply feedback module and a signal conditioning detection module which are electrically connected in sequence, the external mechanical switch module is used for receiving key operation of a user, generating an original key electric signal and performing pi-type filtering on the original key electric signal to suppress electromagnetic interference, and the output end of the external mechanical switch module is connected with the input end of the flyback power supply circuit module; the output end of the flyback power supply circuit module is connected with the sampling end of the flyback power supply feedback module and the power supply end of the signal conditioning detection module. Through quadruple technical innovation of pi-type filtering source noise suppression, flyback isolation intermediate voltage stabilization, optocoupler feedback accurate regulation and control and secondary operational amplifier terminal conditioning, three core pain points in the field of inverter key detection are solved: the anti-interference performance is weak, the power supply fluctuation is large, and the signal driving is insufficient.

Description

Technical Field

[0001] This invention belongs to the field of inverter human-machine interaction and power feedback control technology, and more specifically, it relates to an inverter button detection system based on π-type filtering and flyback isolation feedback. Background Technology

[0002] In the field of inverter human-machine interaction and power feedback control technology, the reliability of the auxiliary button detection system directly affects the overall stability of the machine and the user experience. Existing technologies for inverter button detection solutions generally suffer from three major pain points: weak anti-interference capability, large power supply fluctuations, and insufficient signal drive. Specifically, mechanical switches are prone to generating high-frequency electromagnetic noise and inrush current when activated, leading to misjudgments of button states by the control chip. Industry statistics show a high false trigger rate, severely impacting operational accuracy. Simultaneously, due to the wide input voltage range of inverters, traditional linear power supplies or feedback-free switching power supplies struggle to provide stable operating voltages, resulting in high output ripple and load regulation. Power supply fluctuations further exacerbate the uncertainty of the button detection circuit. Furthermore, existing designs often directly connect the reference signal to the microcontroller's I / O port, leading to insufficient drive capability, significant signal attenuation, and a lack of effective transient overvoltage protection mechanisms. This makes them unable to withstand surge impacts such as electrostatic discharge, increasing the risk of control chip damage.

[0003] While some technologies have attempted to improve performance from a single dimension—such as using simple RC filters or EMC structures to suppress interference, or using primary-side feedback for voltage regulation—these solutions often fail to achieve end-to-end coordinated optimization from signal input, power isolation, feedback control to terminal conditioning. For example, existing inverter fault detection circuits primarily focus on power fault diagnosis, without addressing the deep integration of button human-machine interaction signals and isolated feedback power supplies; existing EMC button circuits only suppress noise through local filtering, lacking optocoupler isolation feedback and secondary precise voltage regulation stages, thus failing to systematically solve the problems of grounding interference and low voltage accuracy.

[0004] Therefore, the present invention provides an inverter key detection system based on π-type filtering and flyback isolation feedback. Summary of the Invention

[0005] In view of the above-mentioned problems of existing technologies, the purpose of this invention is to provide an inverter button detection system based on π-type filtering and flyback isolation feedback. Through four technological innovations—π-type filtering for source noise suppression, flyback isolation for intermediate voltage regulation, optocoupler feedback for precise control, and two-stage operational amplifier for terminal conditioning—this invention solves three core pain points in the field of inverter button detection: weak anti-interference, large power supply fluctuations, and insufficient signal drive. It reduces system false triggering and output ripple, improves signal drive capability, and is based entirely on mature commercial components, possessing the advantages of high reliability and low cost for industrialization.

[0006] The objective of this invention can be achieved through the following technical solutions: An inverter key detection system based on π-type filtering and flyback isolation feedback includes an external mechanical switch module, a flyback power supply circuit module, a flyback power supply feedback module, and a signal conditioning and detection module that are connected in sequence. The external mechanical switch module is used to receive user key operation and generate original key electrical signal, and performs π-type filtering on it to suppress electromagnetic interference. The output terminal of the external mechanical switch module is connected to the input terminal of the flyback power supply circuit module. The output terminal of the flyback power supply circuit module is connected to the sampling terminal of the flyback power supply feedback module and the power supply terminal of the signal conditioning and detection module. The flyback power supply circuit module is used to perform isolated DC-DC conversion on the filtered power supply signal and output a stable isolated working voltage. The flyback power supply feedback module is connected to the secondary output terminal of the flyback power supply circuit module. The flyback power supply feedback module is used to sample the output voltage of the flyback power supply circuit module and compare it with the internal reference to generate a feedback signal. The feedback signal is fed back to the control terminal of the flyback power supply circuit module through optocoupler isolation to form a closed-loop voltage regulation. The signal conditioning and detection module shares a reference with the flyback power supply feedback module. The signal conditioning and detection module is used to buffer, enhance the driving capability and limit the amplitude of the button signal before outputting it to the control chip for detection.

[0007] As a further preferred technical solution of the present invention, the external mechanical switch module includes a mechanical switch S1, a filter inductor L7 and a filter capacitor C32. One end of the mechanical switch S1 is connected to the input power supply BATV+, and the other end of the mechanical switch S1 is connected in series with the filter inductor L7 as the output of the external mechanical switch module. The filter inductor L7 is connected in parallel with the filter capacitor C32, and one end of the filter capacitor C32 is grounded to BAT_GND. The filter inductor L7 and filter capacitor C32 form a π-type filter network, which is used to filter out high-frequency noise and surge current generated when the mechanical switch S1 is activated.

[0008] As a further preferred technical solution of the present invention, the flyback power supply circuit module includes a control chip U7, a power MOSFET Q13, and a high-frequency transformer TX2. The control chip U7 is configured with a drive pin DRV, a current sampling pin CT, and a feedback pin FB. The gate of the power MOSFET Q13 is connected to the drive pin DRV of the control chip U7. The source of the power MOSFET Q13 is grounded through a current sampling resistor network. The drain of the power MOSFET Q13 is connected to the primary winding of the high-frequency transformer TX2. The primary winding of the high-frequency transformer TX2 receives the input voltage filtered by the external mechanical switch module, and its secondary winding outputs an isolated DC voltage +BAT BUS.

[0009] As a further preferred technical solution of the present invention, the flyback power supply feedback module includes a precision reference source U11, an optocoupler U9, and a voltage divider resistor network. The voltage divider resistor network is composed of several resistors connected in series and in parallel. The voltage divider resistor network is connected between the secondary side output voltage +BAT BUS and ground. The voltage divider node of the voltage divider resistor network is connected to the reference electrode of the precision reference source U11. The cathode of the precision reference source U11 is connected to the anode of the light-emitting diode in the optocoupler U9, the cathode of the light-emitting diode in the optocoupler U9 is grounded, the collector of the phototransistor in the optocoupler U9 is connected to the feedback pin FB of the control chip U7, and the emitter of the phototransistor in the optocoupler U9 is grounded, thereby isolating and feeding back the voltage error signal on the secondary side to the control chip U7 on the primary side, forming a closed-loop voltage regulation.

[0010] As a further preferred technical solution of the present invention, the signal conditioning and detection module includes a first-stage operational amplifier U30C, a second-stage operational amplifier U30D, and a limiting diode D37. The first-stage operational amplifier U30C is connected in the form of a voltage follower. The non-inverting input terminal of the first-stage operational amplifier U30C receives the sampling signal from the voltage divider resistor network or the reference signal from the precision reference source U11. The output terminal of the first-stage operational amplifier U30C is connected to the non-inverting input terminal of the second-stage operational amplifier U30D through a resistor R354. The second-stage operational amplifier U30D is also connected in the form of a voltage follower. The output terminal of the second-stage operational amplifier U30D is connected to the I / O port of the MCU through a resistor R353. The cathode of the limiting diode D37 is connected between the resistor R353 and the I / O port of the MCU, and the anode of the limiting diode D37 is grounded. The limiting diode D37 is used to clamp the signal voltage input to the MCU within a safe range.

[0011] As a further preferred technical solution of the present invention, the first-stage operational amplifier U30C and the second-stage operational amplifier U30D are integrated into the same dual operational amplifier or quad operational amplifier chip.

[0012] As a further preferred technical solution of the present invention, the limiting diode D37 is a Zener diode, and the Zener voltage of the limiting diode D37 is not greater than the maximum voltage that the I / O port of the MCU can withstand.

[0013] As a further preferred technical solution of the present invention, the inductance value of the filter inductor L7 is 100μH, the capacitance value of the filter capacitor C32 is 10μF, the cutoff frequency of the π-type filter network is designed to be 1.6kHz, and the π-type filter network is used to effectively filter out switching electromagnetic interference from 10kHz to 100kHz.

[0014] An inverter comprising the aforementioned inverter key detection system based on π-type filtering and flyback isolation feedback.

[0015] An electronic device comprising the inverter described above.

[0016] As described above, the inverter key detection system based on π-type filtering and flyback isolation feedback provided by the present invention has the following beneficial effects: 1. This invention utilizes an inverter key detection system based on π-type filtering and flyback isolation feedback. Compared with existing technologies, it innovatively integrates a π-type filter network composed of filter inductor L7 and filter capacitor C32 into the external mechanical switch module. Its cutoff frequency is carefully designed to effectively filter out high-frequency electromagnetic interference and surge current generated when mechanical switch S1 is activated. This design suppresses noise from the signal source, solves the problem of control chip misjudgment caused by switch noise, and reduces the key false trigger rate. At the same time, the flyback power supply circuit module achieves electrical isolation between the primary and secondary sides through high-frequency transformer TX2. Combined with the isolation feedback of optocoupler U9, it completely blocks the common ground interference from the high-voltage side to the low-voltage detection side, forming a double anti-interference guarantee.

[0017] 2. This invention utilizes an inverter key detection system based on π-type filtering and flyback isolation feedback. Compared with existing technologies, it employs a flyback switching power supply topology, which can adapt to fluctuations in the wide range of inverter input voltage. More importantly, through a flyback power supply feedback module composed of a precision reference source U11 and an optocoupler U9, the output voltage is directly sampled on the secondary side and compared with a high-precision reference. The error signal is then fed back to the primary-side control chip U7 via optocoupler isolation, forming a precise closed-loop voltage regulation control. Compared with traditional primary-side feedback, this secondary feedback mechanism improves the voltage regulation accuracy of the output voltage, reduces output ripple, optimizes load regulation, and provides an extremely stable and clean operating voltage for the subsequent signal conditioning and detection module, solving the problem of unreliable key detection caused by power supply fluctuations.

[0018] 3. This invention utilizes the aforementioned inverter key detection system based on π-type filtering and flyback isolation feedback. Compared with existing technologies, the signal conditioning and detection module of this invention is ingeniously designed. It shares the same precision reference source U11 with the flyback power supply feedback module, ensuring the accuracy of the detection reference. The module employs a voltage follower circuit composed of two operational amplifiers. The first stage achieves high input impedance buffering, and the second stage significantly enhances the signal driving capability, thereby improving its load-carrying capacity. This effectively solves the problem of signal attenuation and distortion caused by insufficient load capacity when the reference signal directly drives the MCU. In addition, a limiting protection circuit composed of limiting diode D37 is set at the end of the module, which can reliably clamp the signal voltage input to the MCU I / O port within a safe range, effectively preventing transient overvoltages such as surge voltage or electrostatic discharge from damaging the expensive control chip, and greatly improving the robustness and service life of the system.

[0019] 4. This invention utilizes the aforementioned inverter key detection system based on π-type filtering and flyback isolation feedback. Compared with existing technologies, it organically integrates key detection, power conversion, voltage regulation feedback, and signal conditioning functions through modular design. The circuit structure is clear and the functions are well-defined. Core components such as operational amplifiers, TL431, and optocouplers are all mature and universal commercial devices, resulting in minimal increase in material costs. Furthermore, the circuit layout is compatible with conventional PCB design processes, which is highly conducive to large-scale production and rapid promotion, and has good industrial application value.

[0020] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The diagram shows the overall circuit structure of an inverter key detection system based on π-type filtering and flyback isolation feedback, as per this invention application. Figure 2 This is an overall circuit diagram of an inverter key detection system based on π-type filtering and flyback isolation feedback, which is the subject of this invention application. Figure 3 This is a circuit diagram of the external mechanical switch module of an inverter key detection system based on π-type filtering and flyback isolation feedback, which is the subject of this invention application. Figure 4 The circuit structure diagram of the flyback power supply circuit module of an inverter key detection system based on π-type filtering and flyback isolation feedback is provided in this invention application. Figure 5 The circuit diagram of the flyback power feedback module of an inverter key detection system based on π-type filtering and flyback isolation feedback is provided in this invention application. Figure 6 This is a circuit diagram of a signal conditioning and detection module for an inverter key detection system based on π-type filtering and flyback isolation feedback, as per this invention application.

[0023] Summary of figure labels and their descriptions: ① External mechanical switch module; ② Flyback power supply circuit module; ③ Flyback power supply feedback module; ④ Signal conditioning and detection module. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0025] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art and are not intended to limit the scope of the invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention. Specific structures can be described with reference to the accompanying drawings of the patent application.

[0026] This invention provides an inverter key detection system based on π-type filtering and flyback isolation feedback. Please refer to [link to relevant documentation]. Figures 1 to 6 As shown, it includes an external mechanical switch module, a flyback power supply circuit module, a flyback power supply feedback module, and a signal conditioning and detection module that are connected in sequence. The external mechanical switch module is used to receive user key operation and generate original key electrical signal, and performs π-type filtering on it to suppress electromagnetic interference. The output terminal of the external mechanical switch module is connected to the input terminal of the flyback power supply circuit module. The output terminal of the flyback power supply circuit module is connected to the sampling terminal of the flyback power supply feedback module and the power supply terminal of the signal conditioning and detection module. The flyback power supply circuit module is used to perform isolated DC-DC conversion on the filtered power supply signal and output a stable isolated working voltage. The flyback power supply feedback module is connected to the secondary output terminal of the flyback power supply circuit module. The flyback power supply feedback module is used to sample the output voltage of the flyback power supply circuit module and compare it with the internal reference to generate a feedback signal. The feedback signal is fed back to the control terminal of the flyback power supply circuit module through optocoupler isolation to form a closed-loop voltage regulation. The signal conditioning and detection module shares a reference with the flyback power supply feedback module. The signal conditioning and detection module is used to buffer, enhance the driving capability and limit the amplitude of the button signal before outputting it to the control chip for detection.

[0027] It should be noted that: This invention suppresses high-frequency electromagnetic interference and surge current generated by mechanical switch operation through π-type filtering, reducing the false trigger rate of buttons; furthermore, the flyback power supply circuit module achieves electrical isolation between the primary and secondary sides through the high-frequency transformer TX2, completely blocking the common ground interference from the high-voltage side to the low-voltage detection side. Combined with the secondary feedback closed loop formed by optocoupler U9 and precision reference source U11, the output voltage ripple and load regulation are reduced, providing a stable and clean operating voltage for the subsequent circuits; in addition, the signal conditioning module and the feedback module share the reference source, improve the signal driving capability through two-stage operational amplifier followers, and use limiting diode D37 to achieve overvoltage protection of the MCU I / O port, significantly enhancing the system robustness.

[0028] Combination Figure 3 As shown, the external mechanical switch module includes a mechanical switch S1, a filter inductor L7, and a filter capacitor C32. One end of the mechanical switch S1 is connected to the input power supply BATV+, and the other end of the mechanical switch S1 is connected in series with the filter inductor L7 as the output of the external mechanical switch module. The filter inductor L7 is connected in parallel with the filter capacitor C32, and one end of the filter capacitor C32 is grounded to BAT_GND. The filter inductor L7 and filter capacitor C32 constitute a π-type filter network, which is used to filter out high-frequency noise and surge current generated when the mechanical switch S1 is activated. The cutoff frequency of the π-type filter network is designed to be 1.6kHz, which can specifically filter out high-frequency switching noise from 10kHz to 100kHz. Compared with single capacitor filtering or RC filtering, this design improves insertion loss and effectively suppresses transient electromagnetic interference generated by mechanical switch arcing, reducing the risk of false triggering from the hardware level. At the same time, the network structure is simple, low-cost, and easy to integrate into the existing inverter PCB layout.

[0029] Combination Figure 4As shown, the flyback power supply circuit module includes a control chip U7, a power MOSFET Q13, and a high-frequency transformer TX2. The control chip U7 is configured with a drive pin DRV, a current sampling pin CT, and a feedback pin FB. The gate of the power MOSFET Q13 is connected to the drive pin DRV of the control chip U7, the source of the power MOSFET Q13 is grounded through a current sampling resistor network, and the drain of the power MOSFET Q13 is connected to the primary winding of the high-frequency transformer TX2. The primary winding of the high-frequency transformer TX2 receives the input voltage filtered by the external mechanical switch module, and its secondary winding outputs an isolated DC voltage +BAT BUS. This application adopts a flyback switching power supply topology, which is compatible with the wide input voltage range of the inverter. It achieves overcurrent and overvoltage protection through a current sampling resistor network. Furthermore, the isolation design of the high-frequency transformer TX2 not only improves system safety but also solves the industry pain point of strong and weak current ground interference, providing an isolated and stable +BAT BUS voltage for the subsequent button detection circuit.

[0030] Combination Figure 5 As shown, the flyback power supply feedback module includes a precision reference source U11, an optocoupler U9, and a voltage divider resistor network. The voltage divider resistor network is composed of several resistors connected in series and parallel. The voltage divider resistor network is connected between the secondary side output voltage +BAT BUS and ground. The voltage divider node of the voltage divider resistor network is connected to the reference terminal of the precision reference source U11, which is a TL431. The cathode of the precision reference source U11 is connected to the anode of the light-emitting diode inside the optocoupler U9, the cathode of the light-emitting diode inside the optocoupler U9 is grounded, the collector of the phototransistor inside the optocoupler U9 is connected to the feedback pin FB of the control chip U7, and the emitter of the phototransistor inside the optocoupler U9 is grounded. This isolates and feeds back the voltage error signal on the secondary side to the control chip U7 on the primary side, forming a closed-loop voltage regulation. This application constructs a secondary-side feedback closed loop through the precision reference source U11—TL431 and the optocoupler U9. After comparing the output voltage sample value with a 2.5V reference, it is fed back to the FB pin of the primary-side control chip U7 via optocoupler isolation. Compared with the traditional primary-side feedback scheme, this design has better voltage regulation accuracy, and the optocoupler isolation ensures that the feedback loop is electrically independent from the high-voltage side, thus improving the system's EMC performance.

[0031] Combination Figure 6As shown, the signal conditioning and detection module includes a first-stage operational amplifier U30C, a second-stage operational amplifier U30D, and a limiting diode D37. The first-stage operational amplifier U30C is configured as a voltage follower. Its non-inverting input receives a sampling signal from the voltage divider network or a reference signal from the precision reference source U11. The output of the first-stage operational amplifier U30C is connected to the non-inverting input of the second-stage operational amplifier U30D via resistor R354. The second-stage operational amplifier U30D is also configured as a voltage follower. Its output is connected to the I / O port of the MCU via resistor R353. The cathode of the limiting diode D37... Connected between resistor R353 and the MCU's I / O port, the anode of the limiting diode D37 is grounded. The limiting diode D37 is used to clamp the signal voltage input to the MCU within a safe range. The first-stage operational amplifier U30C and the second-stage operational amplifier U30D are integrated into the same dual or quad operational amplifier chip. The signal conditioning module uses two-stage op-amp followers U30C and U30D. The first stage achieves high input impedance buffering, and the second stage significantly enhances the load-carrying capacity, solving the signal attenuation problem caused by insufficient drive of traditional single-stage op-amps. The limiting diode D37 clamps the output signal to the MCU's safe voltage range, effectively protecting against transient overvoltages such as ESD. If the op-amps are integrated into a single chip, the PCB area occupied can be further reduced.

[0032] The limiting diode D37 is a Zener diode. The Zener voltage of the limiting diode D37 is not greater than the maximum voltage that the I / O port of the MCU can withstand. The Zener diode D37 is selected with a Zener voltage that does not exceed the withstand voltage of the MCU I / O port to ensure that the signal voltage is always within the safe threshold, avoid damage to expensive control chips, and extend the system life.

[0033] The filter inductor L7 has an inductance of 100μH, the filter capacitor C32 has a capacitance of 10μF, and the cutoff frequency of the π-type filter network is designed to be 1.6kHz. The π-type filter network is used to effectively filter out switching electromagnetic interference from 10kHz to 100kHz. Through the combination of the 100μH filter inductor L7 and the 10μF filter capacitor C32, the π-type filter network achieves a suppression ratio of over 40dB for interference from 10kHz to 100kHz at a cutoff frequency of 1.6kHz.

[0034] An inverter comprising the aforementioned inverter key detection system based on π-type filtering and flyback isolation feedback.

[0035] An electronic device comprising the inverter described above.

[0036] Integrating this system into inverters or electronic devices, such as photovoltaic energy storage devices, can significantly improve the reliability of human-machine interface button detection, while reducing the system failure rate caused by power fluctuations or interference. The modular design makes the circuit compatible with conventional PCB processes, reducing material costs and offering high cost-effectiveness and industrialization potential.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. An inverter key detection system based on π-type filtering and flyback isolation feedback, characterized by, The external mechanical switch module, the flyback power supply circuit module, the flyback power supply feedback module and the signal conditioning detection module are connected in sequence. The external mechanical switch module is used for receiving user key operation and generating original key electrical signal, and performing π type filtering to suppress electromagnetic interference. The output end of the external mechanical switch module is connected with the input end of the flyback power supply circuit module. The output end of the flyback power supply circuit module is connected with the sampling end of the flyback power supply feedback module and the power supply end of the signal conditioning detection module. The flyback power supply feedback module is connected with the secondary side output end of the flyback power supply circuit module.

2. The inverter key detection system based on π-type filter and flyback isolation feedback according to claim 1, characterized in that, The signal conditioning detection module shares reference with the flyback power supply feedback module. The external mechanical switch module includes a mechanical switch S1, a filter inductor L7 and a filter capacitor C32.

3. The inverter key detection system based on π-type filter and flyback isolation feedback according to claim 1, characterized in that, The filter inductor L7 and the filter capacitor C32 constitute a π type filter network for filtering high frequency noise and inrush current generated when the mechanical switch S1 operates.

4. The inverter key detection system based on π-type filter and flyback isolation feedback according to claim 3, characterized in that, The flyback power supply circuit module includes a control chip U7, a power MOS tube Q13 and a high frequency transformer TX2. The flyback power supply feedback module includes a precision reference source U11, an optoelectronic coupler U9 and a voltage dividing resistor network. The voltage dividing resistor network is composed of a plurality of series and parallel resistors. The voltage dividing resistor network is connected between the secondary side output voltage +BAT BUS and the ground. The cathode of the precision reference source U11 is connected to the anode of the light emitting diode in the optocoupler U9, the cathode of the light emitting diode in the optocoupler U9 is grounded, the collector of the phototransistor in the optocoupler U9 is connected to the feedback pin FB of the control chip U7, and the emitter of the phototransistor in the optocoupler U9 is grounded, so as to isolate and feedback the voltage error signal on the secondary side to the control chip U7 on the primary side, forming a closed-loop voltage stabilizer.

5. The inverter key detection system based on π-type filter and flyback isolation feedback according to claim 4, characterized in that, The signal conditioning and detection module comprises a first-stage operational amplifier U30C, a second-stage operational amplifier U30D and a limiting diode D37, the first-stage operational amplifier U30C is connected in the form of a voltage follower, the non-inverting input terminal of the first-stage operational amplifier U30C receives a sampling signal from the voltage dividing resistor network or a reference signal from the precision reference source U11, the output terminal of the first-stage operational amplifier U30C is connected to the non-inverting input terminal of the second-stage operational amplifier U30D through a resistor R354, the second-stage operational amplifier U30D is also connected in the form of a voltage follower, the output terminal of the second-stage operational amplifier U30D is connected to the I / O port of the MCU through a resistor R353, the cathode of the limiting diode D37 is connected between the resistor R353 and the I / O port of the MCU, the anode of the limiting diode D37 is grounded, and the limiting diode D37 is used to clamp the signal voltage input to the MCU within a safe range.

6. The inverter key detection system based on π-type filter and flyback isolation feedback of claim 5, wherein, The first-stage operational amplifier U30C and the second-stage operational amplifier U30D are integrated in the same dual-operational amplifier or four-operational amplifier chip.

7. The inverter key detection system based on π-type filter and flyback isolation feedback of claim 5, wherein, The limiting diode D37 is a voltage stabilizing diode, and the voltage stabilizing value of the limiting diode D37 is not greater than the maximum voltage that can be borne by the I / O port of the MCU.

8. The inverter key detection system based on π-type filter and flyback isolation feedback of claim 2, wherein, The inductance value of the filter inductor L7 is 100 μH, the capacitance value of the filter capacitor C32 is 10 μF, the cut-off frequency of the π-type filter network is designed to be 1.6 kHz, and the π-type filter network is used to effectively filter out the switching electromagnetic interference of 10 kHz to 100 kHz.

9. An inverter, characterized by comprising: An inverter key detection system based on π-type filtering and flyback isolation feedback, comprising any one of the systems according to claims 1 to 8.

10. An electronic device, comprising: An inverter, comprising the inverter according to claim 9.

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