Input over / under voltage protection circuit with optical coupling isolation

Abstract

The application relates to an input over-voltage and under-voltage protection circuit with light coupling isolation, which comprises a power module, a sampling circuit, an operational amplifier comparison circuit, a light coupling isolation circuit and a control circuit. The input end of the power module is adapted to be electrically connected with a single-phase alternating-current 220V power supply. The sampling circuit processes the voltage signal of the power module. The input end of the operational amplifier comparison circuit is adapted to be electrically connected with an over-voltage circuit, an under-voltage circuit and the sampling circuit. The output end outputs a high-level signal to drive the light coupling isolation circuit when input over-voltage or input over-voltage and under-voltage occurs. The control circuit judges the voltage signal output by the light coupling isolation circuit. When the voltage signal is high, the power module is disconnected; when the voltage signal is low, the power module is turned on. The power voltage is monitored through the sampling circuit and the operational amplifier comparison circuit. When over-voltage or under-voltage occurs, the power module can be timely cut off through the control circuit, the subsequent load and circuit elements are protected, and damage caused by abnormal voltage is avoided.

Description

Technical Field

[0001] This application relates to the field of switching power supply protection technology, and in particular to an input over / under voltage protection circuit with optocoupler isolation. Background Technology

[0002] Existing switching power supply protection circuits often fail to effectively isolate the front-end power supply from the back-end circuits when the input voltage is abnormal, leading to damage to the back-end circuits or causing safety accidents. Furthermore, due to the lack of effective isolation measures, interference between circuits is also quite severe, affecting the stability and reliability of the equipment. Utility Model Content

[0003] In view of this, this application proposes an input over / under voltage protection circuit with optocoupler isolation.

[0004] To address the issue of unstable control loops in traditional power supply internal circuits, an input over / under voltage protection circuit with optocoupler isolation is provided, comprising: a power supply module, a sampling circuit, an operational amplifier comparator circuit, an optocoupler isolation circuit, and a control circuit.

[0005] The input terminal of the power module is suitable for electrical connection with a single-phase AC 220V power supply;

[0006] The sampling circuit processes the voltage signal of the power module.

[0007] The input terminals of the operational amplifier comparator circuit are respectively adapted to be electrically connected to the overvoltage circuit, the undervoltage circuit, and the sampling circuit. When the input is overvoltage or undervoltage, the output terminal outputs a high-level signal to drive the optocoupler isolation circuit.

[0008] The control circuit judges the voltage signal output by the optocoupler isolation circuit. When the voltage signal is high, the power module is disconnected; when the voltage signal is low, the power module is turned on.

[0009] In one possible implementation, the power module includes: a rectifier bridge, a forward converter, a transformer, and a rectifier output circuit;

[0010] The rectifier bridge, the forward converter circuit, the transformer, and the rectifier output circuit are connected in series in sequence.

[0011] In one possible implementation, the power module further includes: an auxiliary power supply circuit;

[0012] The control circuit is connected in series with the rectifier output circuit;

[0013] The auxiliary power supply circuit is electrically connected to both the power module and the control circuit.

[0014] In one possible implementation, the sampling circuit is electrically connected to both the control circuit and the power module.

[0015] In one possible implementation, the operational amplifier comparator circuit includes: an undervoltage circuit, an overvoltage circuit, a first comparator, a second comparator, a resistor R35, a resistor R42, and a capacitor C30;

[0016] The negative input terminal of the first comparator is electrically connected to the overvoltage circuit, the positive input terminal is electrically connected to the sampling circuit, and the first comparator is electrically connected to the C30 capacitor. The two ends of the R35 resistor are respectively electrically connected to the positive input terminal and the output terminal of the second comparator.

[0017] The positive input of the second comparator is connected to the undervoltage circuit, the negative input is electrically connected to the sampling circuit, and the resistor R42 is electrically connected to the positive input and the output of the second comparator, respectively.

[0018] In one possible implementation, the overvoltage circuit includes resistors R28 and R33, one end of resistor R28 is adapted to a 5V voltage and the other end is electrically connected to the negative input of the first comparator, and one end of resistor R33 is grounded and the other end is electrically connected to the negative input of the first comparator.

[0019] The overvoltage circuit includes resistors R37 and R41. One end of resistor R37 is adapted to a 5V voltage, and the other end is electrically connected to the negative input of the second comparator. One end of resistor R41 is grounded, and the other end is electrically connected to the negative input of the second comparator.

[0020] In one possible implementation, the optocoupler isolation circuit includes: an overvoltage optocoupler isolation circuit and an over / undervoltage optocoupler isolation circuit;

[0021] The overvoltage optocoupler isolation circuit is electrically connected to the output terminal of the first comparator, and when the output of the first comparator is a high-level signal, the overvoltage optocoupler isolation circuit sends an overvoltage signal to the control circuit.

[0022] The over / under optocoupler isolation circuit is electrically connected to the output terminal of the first comparator, and when the output of the second comparator is a high-level signal, the over / under optocoupler isolation circuit sends an over / under signal to the control circuit.

[0023] In one possible implementation, the overvoltage optocoupler isolation circuit includes: resistor R29, overvoltage isolation optocoupler, resistor R34, and capacitor C34. The output terminal of the first comparator, resistor R29, overvoltage isolation optocoupler, and control circuit are connected in series in sequence. One end of resistor R34 is electrically connected to the output terminal of overvoltage isolation optocoupler, and the other end is grounded. One end of capacitor C34 is electrically connected to overvoltage isolation optocoupler, and the other end is grounded.

[0024] The over / under isolation optocoupler circuit includes: resistor R36, over / under isolation optocoupler, resistor R38, and capacitor C37. The output terminal of the second comparator, resistor R36, over / under isolation optocoupler, and control circuit are connected in series. One end of resistor R38 is electrically connected to the output terminal of over / under isolation optocoupler, and the other end is grounded. One end of capacitor C37 is electrically connected to over / under isolation optocoupler, and the other end is grounded.

[0025] In one possible implementation, the control circuit includes: a control chip;

[0026] The control chip is a TMS320F28035;

[0027] Pin 44 of the control chip is electrically connected to the overvoltage optocoupler isolation circuit;

[0028] Pin 34 of the control chip is electrically connected to the over / under optocoupler isolation circuit.

[0029] In one possible implementation, the sampling circuit includes: resistor R15, resistor R16, resistor R19, resistor R20, first diode, second diode, resistor R21, resistor R22, capacitor C24, and resistor R25.

[0030] The resistors R15 and R16 and the first diode are connected in series to form a first sampling circuit. The resistors R19 and R20 and the second diode are connected in series to form a second sampling circuit. The first sampling circuit and the second sampling circuit are rectified and then electrically connected to the resistors R21 and R22 and the operational amplifier comparator circuit.

[0031] The first sampling circuit and the second sampling circuit are shorted and then grounded;

[0032] One end of capacitor C24 is electrically connected to resistor R22, and the other end is grounded;

[0033] One end of the resistor R25 is electrically connected to the resistor R22, and the other end is grounded.

[0034] The beneficial effects of the input over / under voltage protection circuit with optocoupler isolation in this application embodiment are as follows: By monitoring the power supply voltage through the sampling circuit and the operational amplifier comparator circuit, overvoltage or undervoltage can be detected in time and the power module can be cut off through the control circuit to protect the subsequent load and circuit components and avoid damage due to abnormal voltage. In addition, the optocoupler isolation circuit electrically isolates the high voltage side and the low voltage side to prevent interference signals or faults on the high voltage side from affecting the control circuit, thereby improving the reliability and stability of the entire system.

[0035] Other features and aspects of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0036] The accompanying drawings, which are included in and form part of this specification, illustrate exemplary embodiments, features, and aspects of this application together with the specification and serve to explain the principles of this application.

[0037] Figure 1 The diagram shows the operational amplifier comparator circuit and optocoupler isolation circuit of an embodiment of this application.

[0038] Figure 2 A circuit diagram illustrating the sampling circuit of an embodiment of this application is shown;

[0039] Figure 3 A circuit diagram of a power module according to an embodiment of this application is shown;

[0040] Figure 4 A schematic diagram of a power supply chip according to an embodiment of this application is shown. Detailed Implementation

[0041] Various exemplary embodiments, features, and aspects of this application will now be described in detail with reference to the accompanying drawings. The same reference numerals in the drawings denote elements that have the same or similar functions. Although various aspects of the embodiments are shown in the drawings, they are not necessarily drawn to scale unless specifically indicated otherwise.

[0042] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0043] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0044] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0045] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0046] like Figures 1-4 As shown, the input over / under voltage protection circuit with optocoupler isolation in this embodiment includes: a power supply module, a sampling circuit, an operational amplifier comparator circuit, an optocoupler isolation circuit, and a control circuit 43. The input terminal of the power supply module is suitable for electrical connection to a single-phase AC 220V power supply. The sampling circuit processes the voltage signal of the power supply module. The input terminal of the operational amplifier comparator circuit is suitable for electrical connection to the overvoltage circuit, the undervoltage circuit, and the sampling circuit, respectively. When the input is overvoltage or undervoltage, the output terminal outputs a high-level signal to drive the optocoupler isolation circuit. The control circuit 43 judges the voltage signal output by the optocoupler isolation circuit. When it is high, the power supply module is disconnected; when it is low, the power supply module is turned on.

[0047] In this specific embodiment, the power supply voltage is monitored by a sampling circuit and an operational amplifier comparator circuit. When overvoltage or undervoltage occurs, it can be detected in time and the power module can be cut off by the control circuit 43 to protect the subsequent load and circuit components and avoid damage due to abnormal voltage. In addition, the optocoupler isolation circuit electrically isolates the high voltage side and the low voltage side to prevent interference signals or faults on the high voltage side from affecting the control circuit 43, thereby improving the reliability and stability of the entire system.

[0048] In one specific embodiment, the power supply module includes a rectifier bridge 39, a forward converter 40, a transformer 41, and a rectifier output circuit 42, which are connected in series. A single-phase 220V AC power supply is used as input, and the AC power is converted into the required DC voltage through the rectifier bridge 39, forward converter 40, transformer 41, and rectifier output circuit 42.

[0049] The rectifier bridge 39 rectifies the single-phase 220V AC power supply, converting AC into pulsating DC, which is the first step in power conversion and provides the DC foundation for subsequent circuits. The forward converter circuit 40 plays the role of power conversion and isolation in DC conversion. In conjunction with the transformer 41, it transforms the rectified DC voltage to meet different output voltage requirements. The transformer 41, driven by the forward converter circuit 40, realizes voltage rise and fall, converting the input voltage into a suitable secondary voltage. The rectifier output circuit 42 rectifies the AC voltage output from the transformer 41 and converts it into a stable DC voltage output, which is the final part that supplies power to the load.

[0050] In this specific embodiment, the power module further includes: an auxiliary power circuit 44, the control circuit 43 and the rectifier output circuit 42 are connected in series, the auxiliary power circuit 44 is electrically connected to the power module and the control circuit 43 respectively, and the auxiliary power circuit 44 provides power support for the control circuit 43.

[0051] In one specific embodiment, the sampling circuit is electrically connected to the control circuit 43 and the power module respectively, samples the voltage of the power module, and divides the sampled signal into two paths, which are compared and judged by the first comparator 11 and the second comparator 12 of the operational amplifier comparator circuit respectively, so as to monitor whether overvoltage or undervoltage occurs.

[0052] In one specific embodiment, the operational amplifier comparator circuit includes: an undervoltage circuit, an overvoltage circuit, a first comparator 11, a second comparator 12, a resistor R35 13, a resistor R42 14, and a capacitor C30 19. The negative input terminal of the first comparator 11 is electrically connected to the overvoltage circuit, and the positive input terminal is electrically connected to the sampling circuit. The first comparator 11 is also electrically connected to the capacitor C30 19. The two ends of the resistor R35 13 are electrically connected to the positive input terminal and the output terminal of the second comparator 12, respectively. The positive input terminal of the second comparator 12 is connected to the undervoltage circuit, and the negative input terminal is electrically connected to the sampling circuit. The resistor R42 14 is also electrically connected to the positive input terminal and the output terminal of the second comparator 12, respectively.

[0053] In one specific embodiment, the overvoltage circuit includes resistors R28 (15) and R33 (16). One end of resistor R28 (15) is adapted to a 5V voltage, and the other end is electrically connected to the negative input of the first comparator 11. One end of resistor R33 (16) is grounded, and the other end is electrically connected to the negative input of the first comparator 11. The overvoltage circuit also includes resistors R37 (17) and R41 (18). One end of resistor R37 (17) is adapted to a 5V voltage, and the other end is electrically connected to the negative input of the second comparator 12. One end of resistor R41 (18) is grounded, and the other end is electrically connected to the negative input of the second comparator 12.

[0054] The overvoltage circuit includes resistors R28 (15) and R33 (16). One end of R28 is connected to 5V, and one end of R33 is grounded. Together, they provide a voltage divider to the negative input of the first comparator 11 to determine the overvoltage reference voltage. When the power module output voltage is too high, causing the sampling circuit voltage to exceed this reference voltage, the first comparator 11 will activate accordingly. The negative input of the first comparator 11 is connected to the overvoltage circuit, and the positive input is connected to the sampling circuit. When the sampling voltage at the positive input is higher than the overvoltage reference voltage at the negative input, its output will change. Simultaneously, the first comparator 11 is electrically connected to capacitor C30 (19), which serves to filter or stabilize the comparator output.

[0055] The undervoltage circuit, likely similar in structure to the overvoltage circuit, utilizes the principle of resistor voltage division to set an undervoltage reference voltage. It is constructed using resistors R37 (R37) and R41 (R41), with R37 connected to 5V and R41 grounded, providing the undervoltage reference voltage to the negative input of the second comparator 12. When the power module output voltage is too low, falling below this reference voltage, the second comparator 12 will react accordingly. The positive input of the second comparator 12 is connected to the undervoltage circuit, and the negative input is connected to the sampling circuit. When the sampled voltage at the negative input is lower than the undervoltage reference voltage at the positive input, its output will change. Resistor R35 (R35) is electrically connected to the positive input and output of the second comparator 12, respectively, and resistor R42 (R42) is also electrically connected to the positive input and output of the second comparator 12, serving as feedback or stabilizing the comparator's operating state.

[0056] In one specific embodiment, the optocoupler isolation circuit includes an overvoltage isolation optocoupler circuit and an over / undervoltage isolation optocoupler circuit. The overvoltage isolation optocoupler circuit is electrically connected to the output terminal of the first comparator 11. When the output of the first comparator 11 is a high-level signal, the overvoltage isolation optocoupler circuit sends an overvoltage signal to the control circuit 43. The over / undervoltage isolation optocoupler circuit is electrically connected to the output terminal of the first comparator 11. When the output of the second comparator 12 is a high-level signal, the over / undervoltage isolation optocoupler circuit sends an over / undervoltage signal to the control circuit 43. The optocoupler isolation circuit mainly serves as an electrical isolation circuit, converting the high-voltage signal into a low-voltage signal through optocoupler isolation, preventing high voltage from damaging the control circuit 43, and ensuring reliable signal transmission. The overvoltage isolation optocoupler circuit receives the output from the first comparator 11, and the over / undervoltage isolation optocoupler circuit receives the output from the second comparator 12. When a high-level signal is received, it sends a corresponding overvoltage or over / undervoltage signal to the control circuit 43.

[0057] The overvoltage isolation optocoupler circuit consists of resistor R29 20, overvoltage isolation optocoupler 21, resistor R34 22, and capacitor C34 23. The high-level signal output by the first comparator 11 drives the overvoltage isolation optocoupler 21 through resistor R29 20, making it conduct and transmitting the overvoltage signal from the high-voltage side to the low-voltage side. Resistor R34 22 and capacitor C34 23 play the roles of current limiting and filtering, ensuring the stability of the optocoupler output signal, and at the same time transmitting the overvoltage signal to the control circuit 43.

[0058] The over / under isolation optocoupler circuit consists of resistor R36 27, over / under isolation optocoupler 26, resistor R38 25, and capacitor C37 24. When the second comparator 12 outputs a high-level signal, it drives the over / under isolation optocoupler 26 through resistor R36 27. After current limiting and filtering by resistor R38 25 and capacitor C37 24, the over / under signal is reliably transmitted to the control circuit 43.

[0059] In one specific embodiment, the overvoltage isolation optocoupler circuit includes: resistor R29 20, overvoltage isolation optocoupler 21, resistor R34 22, and capacitor C34 23. The output terminal of the first comparator 11, resistor R29 20, overvoltage isolation optocoupler 21, and control circuit are connected in series in sequence. One end of resistor R34 22 is electrically connected to the output terminal of overvoltage isolation optocoupler 21, and the other end is grounded. One end of capacitor C34 23 is electrically connected to overvoltage isolation optocoupler 21, and the other end is grounded. The over- and under-voltage isolation optocoupler circuit includes: resistor R36 27, over- and under-voltage isolation optocoupler 26, resistor R38 25, and capacitor C37 24. The output terminal of the second comparator 12, resistor R36 27, over- and under-voltage isolation optocoupler 26, and control circuit are connected in series in sequence. One end of resistor R38 25 is electrically connected to the output terminal of over- and under-voltage isolation optocoupler 26, and the other end is grounded. One end of capacitor C37 24 is electrically connected to over- and under-voltage isolation optocoupler 26, and the other end is grounded.

[0060] In one specific embodiment, the control circuit 43 includes: a control chip, specifically a TMS320F28035; pin 44 of the control chip is electrically connected to an overvoltage isolation optocoupler circuit, and pin 34 of the control chip is electrically connected to an over- and undervoltage isolation optocoupler circuit. The control chip's internal program or logic controls the power module's on / off state. When an overvoltage or undervoltage signal is received, the power module is disconnected to prevent damage to the load or other parts of the circuit from excessively high or low voltage. When the signal is low, the power module is turned on to ensure normal power supply to the circuit, achieving intelligent protection and control of the power supply.

[0061] In one specific embodiment, the sampling circuit includes: resistors R15 (28), R16 (29), R19 (31), R20 (32), a first diode (30), a second diode (33), R21 (34), R22 (35), capacitor C24 (36), and resistor R25 (37). Resistors R15 (28), R16 (29), and the first diode (30) are connected in series to form a first sampling circuit. Resistors R19 (31), R20 (32), and the second diode (33) are connected in series to form a second sampling circuit. The first and second sampling circuits are rectified and then electrically connected to resistors R21 (34), R22 (35), and the operational amplifier comparator circuit. The first and second sampling circuits are shorted and then grounded. One end of capacitor C24 (36) is electrically connected to resistor R22 (35), and the other end is grounded. One end of resistor R25 (37) is electrically connected to resistor R22 (35), and the other end is grounded. Specifically, the sampling circuit for single-phase AC power firstly uses half-wave rectification. Half-wave rectification is a circuit that uses the unidirectional conduction characteristic of diodes to rectify the AC signal. It retains only the positive half-cycle of the AC signal and filters out the negative half-cycle, thereby converting AC power into DC power and converting the sine wave into an effective DC voltage.

[0062] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An input over / under voltage protection circuit with optocoupler isolation, characterized in that, include: Power supply module, sampling circuit, operational amplifier comparator circuit, optocoupler isolation circuit and control circuit; The input terminal of the power module is suitable for electrical connection with a single-phase AC 220V power supply; The sampling circuit processes the voltage signal of the power module. The input terminals of the operational amplifier comparator circuit are respectively adapted to be electrically connected to the overvoltage circuit, the undervoltage circuit, and the sampling circuit. When the input is overvoltage or undervoltage, the output terminal outputs a high-level signal to drive the optocoupler isolation circuit. The control circuit judges the voltage signal output by the optocoupler isolation circuit. When the voltage signal is high, the power module is disconnected; when the voltage signal is low, the power module is turned on.

2. The input over / under voltage protection circuit with optocoupler isolation according to claim 1, characterized in that, The power module includes: a rectifier bridge, a forward converter circuit, a transformer, and a rectifier output circuit; The rectifier bridge, the forward converter circuit, the transformer, and the rectifier output circuit are connected in series in sequence.

3. The input over / under voltage protection circuit with optocoupler isolation according to claim 2, characterized in that, The power module further includes: an auxiliary power circuit; The control circuit is connected in series with the rectifier output circuit; The auxiliary power supply circuit is electrically connected to both the power module and the control circuit.

4. The input over / under voltage protection circuit with optocoupler isolation according to claim 3, characterized in that, The sampling circuit is electrically connected to both the control circuit and the power module.

5. The input over / under voltage protection circuit with optocoupler isolation according to claim 4, characterized in that, The operational amplifier comparator circuit includes: an undervoltage circuit, an overvoltage circuit, a first comparator, a second comparator, a resistor R35, a resistor R42, and a capacitor C30; The negative input terminal of the first comparator is electrically connected to the overvoltage circuit, the positive input terminal is electrically connected to the sampling circuit, and the first comparator is electrically connected to the C30 capacitor. The two ends of the R35 resistor are respectively electrically connected to the positive input terminal and the output terminal of the second comparator. The positive input of the second comparator is connected to the undervoltage circuit, the negative input is electrically connected to the sampling circuit, and the resistor R42 is electrically connected to the positive input and the output of the second comparator, respectively.

6. The input over / under voltage protection circuit with optocoupler isolation according to claim 5, characterized in that, The overvoltage circuit includes resistors R28 and R33. One end of resistor R28 is suitable for electrical connection to 5V voltage, and the other end is electrically connected to the negative input of the first comparator. One end of resistor R33 is grounded, and the other end is electrically connected to the negative input of the first comparator. The overvoltage circuit includes resistors R37 and R41. One end of resistor R37 is suitable for electrical connection to 5V voltage, and the other end is electrically connected to the negative input of the second comparator. One end of resistor R41 is grounded, and the other end is electrically connected to the negative input of the second comparator.

7. The input over / under voltage protection circuit with optocoupler isolation according to claim 5, characterized in that, The optocoupler isolation circuit includes: an overvoltage optocoupler isolation circuit and an over / undervoltage optocoupler isolation circuit; The overvoltage optocoupler isolation circuit is electrically connected to the output terminal of the first comparator, and when the output of the first comparator is a high-level signal, the overvoltage optocoupler isolation circuit sends an overvoltage signal to the control circuit. The over / under optocoupler isolation circuit is electrically connected to the output terminal of the first comparator, and when the output of the second comparator is a high-level signal, the over / under optocoupler isolation circuit sends an over / under signal to the control circuit.

8. The input over / under voltage protection circuit with optocoupler isolation according to claim 7, characterized in that, The overvoltage optocoupler isolation circuit includes: resistor R29, overvoltage isolation optocoupler, resistor R34, and capacitor C34. The output terminal of the first comparator, resistor R29, overvoltage isolation optocoupler, and control circuit are connected in series. One end of resistor R34 is electrically connected to the output terminal of overvoltage isolation optocoupler, and the other end is grounded. One end of capacitor C34 is electrically connected to overvoltage isolation optocoupler, and the other end is grounded. The over / under isolation optocoupler circuit includes: resistor R36, over / under isolation optocoupler, resistor R38, and capacitor C37. The output terminal of the second comparator, resistor R36, over / under isolation optocoupler, and control circuit are connected in series. One end of resistor R38 is electrically connected to the output terminal of over / under isolation optocoupler, and the other end is grounded. One end of capacitor C37 is electrically connected to over / under isolation optocoupler, and the other end is grounded.

9. The input over / under voltage protection circuit with optocoupler isolation according to claim 7, characterized in that, The control circuit includes: a control chip; The control chip is a TMS320F28035; Pin 44 of the control chip is electrically connected to the overvoltage optocoupler isolation circuit; Pin 34 of the control chip is electrically connected to the over / under optocoupler isolation circuit.

10. The input over / under voltage protection circuit with optocoupler isolation according to claim 5, characterized in that, The sampling circuit includes: resistor R15, resistor R16, resistor R19, resistor R20, first diode, second diode, resistor R21, resistor R22, capacitor C24, and resistor R25; The resistors R15 and R16 and the first diode are connected in series to form a first sampling circuit. The resistors R19 and R20 and the second diode are connected in series to form a second sampling circuit. The first sampling circuit and the second sampling circuit are rectified and then electrically connected to the resistors R21 and R22 and the operational amplifier comparator circuit. The first sampling circuit and the second sampling circuit are shorted and then grounded; One end of capacitor C24 is electrically connected to resistor R22, and the other end is grounded; One end of the resistor R25 is electrically connected to the resistor R22, and the other end is grounded.

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