Isolation circuit and terminal product

Abstract

The embodiment of the application provides an isolation circuit, comprising a transformer and an isolation chip; the transformer comprises a primary circuit and a secondary circuit; two ends of the primary circuit are used for connecting two ends of an alternating current power supply, and the isolation chip is located in the primary circuit; two ends of the secondary circuit are used for connecting two ends of a terminal communication module. The isolation circuit is used for isolating the alternating current power supply and the terminal communication module circuit, so that the two share a common ground but do not exist the electric shock problem. When the terminal product equipped with the isolation circuit needs to be operated, the electric shock situation occurring when the terminal communication module is replaced can be reduced.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to an isolation circuit and terminal product. Background Technology

[0002] In existing technology, the reference ground of the AC power supply is connected to the neutral wire of the AC power supply, while the terminal communication module is directly connected to the AC power supply, meaning the reference ground of the terminal communication module is also directly connected to the neutral wire of the AC circuit. This connection method results in the reference ground of the terminal communication module of the terminal product being directly electrified. If the terminal product is operated without interrupting the AC power supply, electric shock can easily occur. Summary of the Invention

[0003] This application provides an isolation circuit and terminal product for isolating AC power and terminal communication module, which can reduce the risk of electric shock when replacing terminal communication module.

[0004] This application provides an isolation circuit, including a transformer and an isolation chip; The transformer includes a primary circuit and a secondary circuit; The two ends of the primary circuit are used to connect to the two ends of the AC power supply, and the isolation chip is located inside the primary circuit; The two ends of the secondary circuit are used to connect to the two ends of the terminal communication module.

[0005] In some embodiments, the primary-side circuit includes a first filter circuit, a voltage divider circuit, and an absorption circuit; The first terminal of the first filter circuit is connected to the AC power input terminal and the first terminal of the primary winding of the transformer, and the second terminal of the first filter circuit is grounded. The first end of the voltage divider circuit is connected to the AC power input terminal and the first end of the primary winding of the transformer; the second end of the voltage divider circuit is grounded; and the middle node of the voltage divider circuit is connected to the control pin of the isolation chip. The first end of the absorption circuit is connected to the AC power input terminal and the first end of the primary winding of the transformer, and the second end of the absorption circuit is connected to the second end of the primary winding of the transformer. The second phase of the primary winding of the transformer is grounded through the isolation chip.

[0006] In some embodiments, the first filter circuit includes one or more first capacitors, and the plurality of first capacitors are connected in parallel.

[0007] In some embodiments, the voltage divider circuit includes a first resistor and a second resistor connected in series; the first end of the first resistor is connected to the AC power input terminal and the first end of the primary winding of the transformer, and the second end of the second resistor is grounded.

[0008] In some embodiments, the absorption circuit includes a primary protection unit, a current limiting unit, and a secondary protection unit; The first end of the primary protection unit is connected to the AC power input terminal and the first end of the primary winding of the transformer, and the second end of the primary protection unit is connected to the first end of the current limiting unit. The second end of the current limiting unit is connected to the first end of the secondary protection unit, and the second end of the secondary protection unit is connected to the second end of the primary winding of the transformer.

[0009] In some embodiments, the primary protection unit includes a third resistor, a second capacitor, and a first diode connected in parallel; The current limiting unit includes multiple fourth resistors connected in parallel; The secondary protection unit includes a second diode.

[0010] In some embodiments, the secondary circuit includes a buffer circuit and a second filter circuit; The buffer circuit is connected between the first end of the secondary winding of the transformer and the input end of the terminal communication module. The second filter circuit is connected between the input terminal of the terminal communication module and the reference ground of the terminal communication module.

[0011] In some embodiments, the buffer circuit includes a first buffer branch and a second buffer branch connected in parallel; The first buffer branch includes a third capacitor and a fifth resistor connected in series; The second buffer branch includes a third diode; The second filter circuit includes a fourth capacitor and a sixth resistor, which are connected in parallel.

[0012] In some embodiments, the isolation circuit further includes a seventh resistor, an eighth resistor, and a fifth capacitor; The seventh resistor and the eighth resistor are connected in series between the switch pin and the feedback pin of the first chip, and are connected to the second end of the primary winding of the transformer. The fifth capacitor is connected between the input terminal of the terminal communication module and the reference ground of the terminal communication module.

[0013] This application also provides a terminal product, including the isolation circuit and terminal communication module described in any of the above embodiments.

[0014] This application provides an isolation circuit and terminal product for isolating the AC power supply and the terminal communication module circuit, ensuring that both share a common ground while eliminating the risk of electric shock. This reduces the likelihood of electric shock when replacing the terminal communication module during operation. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a block diagram of an isolation circuit configuration system according to an embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the isolation circuit structure according to an embodiment of this application.

[0018] In the diagram: 10. Primary circuit; 20. Secondary circuit; T1. Transformer; U1. Isolation chip; 11. First filter circuit; 12. Voltage divider circuit; 13. Absorption circuit; 131. First-level protection unit; 132. Current limiting unit; 133. Second-level protection unit; 21. Buffer circuit; 211. First buffer branch; 212. Second buffer branch; 22. Second filter circuit. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0020] This application provides an isolation circuit, as referenced in the embodiments. Figure 1 and Figure 2 The isolation circuit includes transformer T1 and isolation chip U1; The transformer T1 includes a primary circuit 10 and a secondary circuit 20; The two ends of the primary circuit 10 are used to connect to the two ends of the AC power supply, and the isolation chip U1 is located inside the primary circuit 10; The two ends of the secondary circuit 20 are used to connect to the two ends of the terminal communication module.

[0021] In one example, the isolation circuit is used to isolate the terminal communication module from the AC power supply, and includes an isolation chip U1, a transformer T1, a primary circuit 10, and a secondary circuit 20.

[0022] In practical applications, the isolation chip U1 can be a PWM chip with a built-in 75V low-voltage MOS, and the transformer T1 can be an EE10 high-frequency transformer, forming the core of the isolation circuit. Specifically, the fifth terminal of the isolation chip U1 is the power input pin VIN, used to power the chip; the first terminal is the control pin EN / UVLO, used to pull the chip high to operate and pull it low to turn it off; the second terminal is the ground pin GND; the fourth terminal is the switching pin SW, used to switch the energy conversion of the chip's power supply; and the third terminal is the feedback pin RFB, used to set the final output voltage.

[0023] The primary circuit 10 is connected between the AC power input terminal VIN and the AC power reference ground PGND. The isolation chip U1 is integrated into the primary circuit 10, serving as the control core of the isolation circuit. Transformer T1 is a high-frequency isolation transformer; its primary winding is connected to the primary circuit 10, and its secondary winding is connected to the secondary circuit 20, achieving energy transfer through magnetic coupling. The secondary circuit 20 is connected between the input terminal VCC of the terminal communication module and the reference ground GND of the terminal communication module, achieving electrical isolation between the AC power supply and the terminal communication module.

[0024] In practical applications, the isolation circuit reduces the voltage of the input circuit to the voltage level required for the terminal communication module to operate. At the same time, through the isolation effect of transformer T1, the AC power reference ground PGND is completely separated from the terminal communication module reference ground GND, thus achieving electric shock protection during uninterrupted operation.

[0025] This isolation circuit uses transformer T1 to electrically isolate the AC power supply reference ground PGND from the terminal communication module's reference ground GND, overcoming the electric shock problem caused by direct connection between the two reference grounds. This circuit requires only a PWM chip with a built-in low-voltage MOS and an EE10 high-frequency transformer, resulting in fewer components, a simpler structure, and significantly reduced implementation cost and design complexity. Furthermore, based on a mature flyback topology, it offers high reliability.

[0026] In some embodiments, the primary-side circuit 10 includes a first filter circuit 11, a voltage divider circuit 12, and an absorption circuit 13; The first terminal of the first filter circuit 11 is connected to the AC power input terminal VIN and the first terminal of the primary winding of the transformer T1, and the second terminal of the first filter circuit 11 is grounded. The first end of the voltage divider circuit 12 is connected to the AC power input terminal VIN and the first end of the primary winding of the transformer T1. The second end of the voltage divider circuit 12 is grounded. The middle node of the voltage divider circuit 12 is connected to the control pin EN / UVLO of the isolation chip U1. The first end of the absorption circuit 13 is connected to the AC power input terminal VIN and the first end of the primary winding of the transformer T1, and the second end of the absorption circuit 13 is connected to the second end of the primary winding of the transformer T1. The second end of the primary winding of the transformer T1 is grounded through the isolation chip U1.

[0027] In one example, the primary-side circuit 10 specifically includes a first filter circuit 11, a voltage divider circuit 12, and an absorption circuit 13.

[0028] The first filter circuit 11 is connected between the AC power input terminal VIN and the voltage divider circuit 12. It is used to provide the subsequent stage with a pre-filtered voltage. It is mainly used to filter out any residual ripple or noise in the output of the isolation circuit, so as to provide a more stable power supply environment for the subsequent stage circuit.

[0029] Voltage divider circuit 12 connects isolation chip U1 and absorption circuit 13. Voltage divider circuit 12 extracts a suitable voltage signal from the voltage of the input circuit and provides it to the control pin EN / UVLO of isolation chip U1 to enable isolation chip U1 to determine its working state.

[0030] The first terminal of the absorption circuit 13 is connected to the AC power input terminal VIN and the first terminal of the primary winding of transformer T1. The second terminal of the absorption circuit 13 is connected to the second terminal of the primary winding of transformer T1 and then connected to the switching pin SW of isolation chip U1 to form a loop. The absorption circuit 13 is used to absorb the high voltage spikes generated by the leakage inductance of transformer T1 during the switching of the MOSFET inside isolation chip U1, preventing these spikes from damaging the power devices inside isolation chip U1, thereby ensuring the reliability of the entire circuit.

[0031] By configuring a first filter circuit 11, a voltage divider circuit 12, and an absorption circuit 13, the input power supply of the primary circuit 10 is pre-processed and protected. The first filter circuit 11 effectively filters out the ripple and noise of the input power supply, providing a cleaner power environment for subsequent circuits. The voltage divider circuit 12 provides a precise operating reference voltage for the isolation chip U1, ensuring stable startup and operation of the isolation chip U1. The absorption circuit 13 clamps the voltage spikes generated by the leakage inductance of the transformer T1, ensuring that the low-voltage MOSFET inside the isolation chip U1 is not damaged, thereby further improving the working stability and service life of the entire isolation circuit.

[0032] In some embodiments, the first filter circuit 11 includes one or more first capacitors C11, and the plurality of first capacitors C11 are connected in parallel.

[0033] In one example, the first filter circuit 11 can select capacitors with different capacitance values ​​and characteristics to combine according to the actual noise spectrum. For example, the first filter circuit 11 may include two first capacitors C11 connected in parallel.

[0034] Multiple first capacitors C11 connected in parallel can be combined to form capacitors with different capacitance values ​​and characteristics as needed, thereby enhancing the ability to suppress noise in different frequency bands, providing a more stable voltage for the primary circuit 10, and helping to improve the output quality of the isolation circuit.

[0035] In some embodiments, the voltage divider circuit 12 includes a first resistor R1 and a second resistor R2 connected in series; the first end of the first resistor R1 is connected to the AC power input terminal VIN and the first end of the primary winding of the transformer T1, and the second end of the second resistor R2 is grounded.

[0036] In one example, the voltage divider circuit 12 specifically includes a first resistor R1 and a second resistor R2 connected in series. These resistors are connected in series between the AC power input terminal VIN and the AC power reference ground PGND, forming a resistor voltage divider circuit 12.

[0037] Meanwhile, the intermediate node of the voltage divider circuit 12 is connected to the control pin EN / UVLO of the isolation chip U1. By setting the resistance ratio of the series resistor, the higher input voltage can be proportionally attenuated to a voltage range that the isolation chip U1 can withstand or recognize, ensuring that the isolation chip U1 starts up and works normally.

[0038] In some embodiments, the absorption circuit 13 includes a primary protection unit 131, a current limiting unit 132, and a secondary protection unit 133; The first end of the primary protection unit 131 is connected to the AC power input terminal VIN and the first end of the primary winding of the transformer T1, and the second end of the primary protection unit 131 is connected to the first end of the current limiting unit 132. The second end of the current limiting unit 132 is connected to the first end of the secondary protection unit 133, and the second end of the secondary protection unit 133 is connected to the second end of the primary winding of the transformer T1.

[0039] In one example, the absorption circuit 13 is designed as a multi-stage structure, specifically including a first-stage protection unit 131, a current-limiting unit 132, and a second-stage protection unit 133.

[0040] The primary protection unit 131 is used to absorb and clamp voltage spikes. The current limiting unit 132 is used to limit the amplitude of the spike current. When the secondary protection unit 133 is turned on, the current limiting unit 132 can control the current flowing to the primary protection unit 131, preventing excessive transient current from damaging the device, and also works with the primary protection unit 131 and the secondary protection unit 133 to distribute power dissipation. The secondary protection unit 133 is used to clamp the voltage within a safe range, protecting the internal switching transistor of the isolation chip U1.

[0041] The absorption circuit 13 adopts a multi-stage structure of primary protection unit 131, current limiting unit 132 and secondary protection unit 133, which can clamp and absorb energy step by step, more reliably suppress voltage spikes generated by leakage inductance of transformer T1, protect the internal diodes of isolation chip U1, and significantly improve the circuit's shock resistance.

[0042] In some embodiments, the primary protection unit 131 includes a third resistor R3, a second capacitor C2, and a first diode D1 connected in parallel; The current limiting unit 132 includes a plurality of fourth resistors R4 connected in parallel; The secondary protection unit 133 includes a second diode D2.

[0043] In one example, the primary protection unit 131 mainly consists of a third resistor R3, a second capacitor C2, and a first diode D1 connected in parallel. The upper end of the parallel structure of the third resistor R3, the second capacitor C2, and the first diode D1 is connected to the first terminal of the primary winding of the transformer T1, and the lower end is connected to the current limiting unit 132. The third resistor R3 consumes some energy, the second capacitor C2 is used to store energy for high-frequency spikes, and the first diode D1 limits the voltage across the primary protection unit 131 to prevent excessive voltage.

[0044] One end of the current limiting unit 132 is connected to the primary protection unit 131, and the other end is connected to the secondary protection unit 133. It is used to limit the residual surge current after being clamped by the previous stage. The current limiting unit 132 can be composed of two parallel fourth resistors R4. The parallel connection of the two resistors can improve the power withstand capability, consume the pulse impulse energy, isolate the front and rear protection circuits, prevent the large current from breaking down the downstream devices, and achieve surge buffering and electrical isolation.

[0045] The first terminal of the secondary protection unit 133 is connected to the current limiting unit 132, and the second terminal is connected to the second terminal of the primary winding of transformer T1. This is used to clamp the voltage to ground at the chip input node after current limiting, thus constraining the chip's pin voltage within a safe range. The secondary protection unit 133 includes a second diode D2, which features a fast response speed, enabling it to detect abnormal voltage increases first and quickly conduct.

[0046] In some embodiments, the secondary circuit 20 includes a buffer circuit 21 and a second filter circuit 22; The buffer circuit 21 is connected between the first end of the secondary winding of the transformer T1 and the input terminal VCC of the terminal communication module. The second filter circuit 22 is connected between the input terminal VCC of the terminal communication module and the reference ground GND of the terminal communication module.

[0047] In one example, the secondary circuit 20 specifically includes a buffer circuit 21 and a second filter circuit 22. The buffer circuit 21 is connected between the secondary winding of the transformer T1 and the input terminal VCC of the terminal communication module to prevent excessively high voltage spikes from being transmitted to subsequent circuits and causing damage to the terminal communication module.

[0048] The second filter circuit 22 is connected between the input terminal VCC of the terminal communication module and the reference ground GND of the terminal communication module. The second filter circuit 22 uses energy storage components to smooth and regulate the voltage, ultimately outputting a DC voltage with extremely low ripple, providing a high-quality power supply for the internal circuitry of the terminal communication module. By setting a buffer circuit 21 and a second filter circuit 22 in the secondary circuit 20, the voltage output from transformer T1 can be processed to provide a smoother and more stable supply to the terminal communication module. The buffer circuit 21 can effectively protect the downstream terminal communication module from overvoltage damage; the second filter circuit 22 further filters out residual ripple, ensuring the power supply quality of the terminal communication module and helping to improve the stability and reliability of the communication signal.

[0049] In some embodiments, the buffer circuit 21 includes a first buffer branch 211 and a second buffer branch 212 connected in parallel; The first buffer branch 211 includes a third capacitor C3 and a fifth resistor R5 connected in series; The second buffer branch 212 includes a third diode D3; The second filter circuit 22 includes a fourth capacitor and a sixth resistor R6, wherein the fourth capacitor and the sixth resistor R8 are connected in parallel.

[0050] In one example, the buffer circuit 21 specifically includes a third capacitor C3, a fifth resistor R5, and a third diode D3. The third capacitor C3 and the fifth resistor R5 are connected in series to form a first buffer branch 211, which is connected in parallel across the secondary winding of transformer T1. When a voltage spike occurs on the secondary winding of transformer T1, the energy is coupled through the third capacitor C3 and dissipated by the fifth resistor R5, thereby suppressing ringing.

[0051] The second buffer branch 212 includes a third diode D3. The second buffer branch 212 is connected in parallel with the first buffer branch 211. Its function is to achieve synchronous rectification or active clamping. This can not only further clamp the spikes, but also reduce the conduction loss on the rectification path and improve the overall power supply efficiency.

[0052] The buffer circuit 21 uses a combination of a first buffer branch 211 and a second buffer branch 212. It can absorb secondary-side spikes in a passive damping manner, and can also achieve synchronous rectification or active clamping through an active switch when needed. This not only further reduces the spike voltage, but also reduces rectification losses, improves power conversion efficiency, and thus reduces the overall power consumption and heat generation of the terminal communication module.

[0053] The second filter circuit 22 specifically includes one or more fourth capacitors C41 and a sixth resistor R6, for example, it consists of three fourth capacitors C41 and one sixth resistor R6. These fourth capacitors C41 and sixth resistor R6 are connected in parallel between the input terminal VCC of the terminal communication module and the reference ground GND of the terminal communication module.

[0054] The parallel connection of multiple fourth capacitors C41, similar to the first filter circuit 11, can accommodate filtering requirements at different frequencies, effectively reducing output ripple and noise. The sixth resistor R6 can be connected in parallel between the input VCC of the terminal communication module and its reference ground GND. When the terminal communication module is under light load or no load, it provides a minimum output current to prevent abnormal voltage increases due to no-load conditions, thus ensuring that the voltage output to the terminal communication module remains stable and meets requirements under any load conditions.

[0055] By connecting multiple fourth capacitors C41 in parallel and setting a sixth resistor R6, the second filter circuit 22 can effectively filter out noise across the entire frequency band and maintain a stable output voltage under no-load or light-load conditions, preventing voltage drift. This ensures that the circuit always obtains the rated voltage under various load conditions and avoids damage caused by abnormal voltage.

[0056] In some embodiments, the isolation circuit further includes a seventh resistor R7, an eighth resistor R8, and a fifth capacitor C5; The seventh resistor R7 and the eighth resistor R8 are connected in series between the switch pin SW and the feedback pin RFB of the isolation chip U1, and are connected to the second end of the primary winding of the transformer T1; the fifth capacitor C5 is connected between the input terminal VCC of the terminal communication module and the reference ground GND of the terminal communication module.

[0057] In one example, the isolation circuit also includes a seventh resistor R7 and an eighth resistor R8. These two resistors are connected in series between the switch pin SW and the feedback pin RFB of the isolation chip U1, and are connected to the second end of the primary winding of the transformer T1, to cooperate with the internal chip circuitry of the isolation chip U1. By precisely selecting the values ​​of the seventh resistor R7 and the eighth resistor R8, the operating frequency or gain of the isolation circuit can be adjusted, and it has good dynamic response characteristics, making the isolation circuit more stable, avoiding subharmonic oscillations, and ensuring that the isolation circuit can work reliably under various load conditions.

[0058] The isolation circuit may also include a fifth capacitor, C5. The fifth capacitor C5 is connected between the input terminal VCC of the terminal communication module and the reference ground GND of the terminal communication module, and can perform energy storage and filtering. A large-capacity energy storage capacitor can be selected for the fifth capacitor C5. When a load transient occurs inside the terminal communication module requiring a large current draw, the energy stored in the fifth capacitor C5 can be quickly replenished, reducing the instantaneous voltage drop of the output voltage and further improving the transient response performance of the terminal communication module's power supply, making its wireless communication function more stable and reliable.

[0059] This application also provides a terminal product, including the isolation circuit and terminal communication module described in any of the above embodiments. The terminal product can reduce the risk of electric shock when replacing the terminal communication module during operation; to avoid repetition, it will not be described in detail here.

[0060] In the description of this application, it should be understood that terms such as “first” and “second” are used only to distinguish similar objects and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0061] It should be noted that in the embodiments of this application, "connection" can be understood as electrical connection. The connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0062] The isolation circuit and terminal product provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. An isolation circuit, characterized in that, Including transformers and isolation chips; The transformer includes a primary circuit and a secondary circuit; The two ends of the primary circuit are used to connect to the two ends of the AC power supply, and the isolation chip is located inside the primary circuit; The two ends of the secondary circuit are used to connect to the two ends of the terminal communication module.

2. The isolation circuit according to claim 1, characterized in that, The primary-side circuit includes a first filter circuit, a voltage divider circuit, and an absorption circuit; The first terminal of the first filter circuit is connected to the AC power input terminal and the first terminal of the primary winding of the transformer, and the second terminal of the first filter circuit is grounded. The first end of the voltage divider circuit is connected to the AC power input terminal and the first end of the primary winding of the transformer; the second end of the voltage divider circuit is grounded; and the middle node of the voltage divider circuit is connected to the control pin of the isolation chip. The first end of the absorption circuit is connected to the AC power input terminal and the first end of the primary winding of the transformer, and the second end of the absorption circuit is connected to the second end of the primary winding of the transformer. The second phase of the primary winding of the transformer is grounded through the isolation chip.

3. The isolation circuit according to claim 2, characterized in that, The first filter circuit includes one or more first capacitors, and the plurality of first capacitors are connected in parallel.

4. The isolation circuit according to claim 2, characterized in that, The voltage divider circuit includes a first resistor and a second resistor connected in series; the first end of the first resistor is connected to the AC power input terminal and the first end of the primary winding of the transformer, and the second end of the second resistor is grounded.

5. The isolation circuit according to claim 2, characterized in that, The absorption circuit includes a primary protection unit, a current limiting unit, and a secondary protection unit; The first end of the primary protection unit is connected to the AC power input terminal and the first end of the primary winding of the transformer, and the second end of the primary protection unit is connected to the first end of the current limiting unit. The second end of the current limiting unit is connected to the first end of the secondary protection unit, and the second end of the secondary protection unit is connected to the second end of the primary winding of the transformer.

6. The isolation circuit according to claim 2, characterized in that, The primary protection unit includes a third resistor, a second capacitor, and a first diode connected in parallel. The current limiting unit includes multiple fourth resistors connected in parallel; The secondary protection unit includes a second diode.

7. The isolation circuit according to claim 1, characterized in that, The secondary circuit includes a buffer circuit and a second filter circuit. The buffer circuit is connected between the first end of the secondary winding of the transformer and the input end of the terminal communication module. The second filter circuit is connected between the input terminal of the terminal communication module and the reference ground of the terminal communication module.

8. The isolation circuit according to claim 7, characterized in that, The buffer circuit includes a first buffer branch and a second buffer branch connected in parallel. The first buffer branch includes a third capacitor and a fifth resistor connected in series; The second buffer branch includes a third diode; The second filter circuit includes a fourth capacitor and a sixth resistor, which are connected in parallel.

9. The isolation circuit according to claim 1, characterized in that, The isolation circuit also includes a seventh resistor, an eighth resistor, and a fifth capacitor; The seventh resistor and the eighth resistor are connected in series between the switch pin and the feedback pin of the first chip, and are connected to the second end of the primary winding of the transformer. The fifth capacitor is connected between the input terminal of the terminal communication module and the reference ground of the terminal communication module.

10. A terminal product, characterized in that, Includes the isolation circuit and terminal communication module as described in any one of claims 1-9.

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