Power supply circuit of passive protection device

Abstract

The utility model discloses a passive protection device power supply circuit, which relates to the technical field of electronic circuits and comprises a power taking circuit, a front-end protection circuit, a main chip control circuit, a rear-end protection circuit and a feedback circuit. The main chip control circuit comprises a constant current source circuit, a clamping protection circuit, a high-frequency transformer and a power supply control chip; the input end of the constant current source circuit, the input end of the clamping protection circuit and the first end of a primary winding of the high-frequency transformer are connected with the output end of the front-end protection circuit, and the input end of the power supply control chip is connected with the output end of the clamping protection circuit and the second end of the primary winding of the high-frequency transformer. The bypass end of the power supply control chip is connected with the output end of the constant current source circuit, and the output end of the power supply control chip is grounded; and the feedback circuit is used for controlling the conduction degree of the power supply control chip according to the direct-current voltage output by the rear-end protection circuit. The surge protection capability of the circuit can be improved, so that the reliability of the circuit and the stability of voltage output are improved.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a power supply circuit for a passive protection device. Background Technology

[0002] Passive protection devices play a crucial role in power systems and various electronic devices. However, the power supplies of currently available passive protection devices generally suffer from poor reliability. When the equipment is running, it is highly susceptible to external interference, especially surges. Surges generate instantaneous high voltage and large current. These abnormal electrical signals can impact the power supply circuit of the passive protection device, leading to unstable power output and, in severe cases, damage to power components. This can cause the passive protection device to malfunction, thereby affecting the safety and stability of the entire equipment system. Once a passive protection device fails, the equipment cannot be effectively protected when encountering faults or abnormal conditions, potentially leading to equipment failure, data loss, or even safety accidents. Utility Model Content

[0003] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a power supply circuit for a passive protection device, which can improve the reliability of the circuit and the stability of the voltage output.

[0004] This application provides a power supply circuit for a passive protection device, including:

[0005] Power supply circuit, used to obtain input voltage from an external source;

[0006] A front-end protection circuit, wherein the input terminal of the front-end protection circuit is connected to the output terminal of the power-taking circuit;

[0007] The main chip control circuit includes a constant current source circuit, a clamping protection circuit, a high-frequency transformer, and a power control chip. The input terminal of the constant current source circuit, the input terminal of the clamping protection circuit, and the first terminal of the primary winding of the high-frequency transformer are respectively connected to the output terminal of the front-end protection circuit. The input terminal of the power control chip is connected to the output terminal of the clamping protection circuit and the second terminal of the primary winding of the high-frequency transformer. The bypass terminal of the power control chip is connected to the output terminal of the constant current source circuit, and the output terminal of the power control chip is grounded.

[0008] The back-end protection circuit has its input terminals connected to the first terminal and the second terminal of the secondary winding of the high-frequency transformer, respectively, and its output terminal is used to output a stable DC voltage.

[0009] A feedback circuit is provided, wherein the input terminal of the feedback circuit is connected to the output terminal of the back-end protection circuit, and the output terminal of the feedback circuit is connected to the control terminal of the power control chip, for controlling the conduction degree of the power control chip according to the DC voltage output by the back-end protection circuit.

[0010] The power supply circuit of the passive protection device according to the first aspect of this application has at least the following beneficial effects: the power supply circuit obtains input voltage from the outside to provide the energy foundation for the entire circuit; the front-end protection circuit preprocesses the input voltage, filters external interference, and prevents excessive voltage and current from impacting subsequent circuits; in the main chip control circuit, the constant current source circuit provides stable current to the power control chip; the clamping protection circuit clamps the abnormally high voltage within a safe range; the high-frequency transformer achieves voltage transformation and isolation through electromagnetic induction; the power control chip controls its own conduction degree according to the signal from the feedback circuit, adjusts the current and voltage of the primary winding of the high-frequency transformer, and achieves stable control of the output voltage; the back-end protection circuit performs secondary processing on the voltage output from the secondary winding of the high-frequency transformer, outputs a stable DC voltage for the load, and the feedback circuit collects the DC voltage signal output from the back-end and feeds it back to the control terminal of the power control chip, adjusting the chip conduction degree according to voltage changes to achieve closed-loop control to ensure stable output voltage. The front-end protection circuit initially blocks the instantaneous high voltage and large current generated by surges. The clamping protection circuit, following the front-end protection circuit, further clamps any leaking abnormal high voltage to a safe value, preventing damage to subsequent circuit components. This effectively resists the impact of surges on the power supply circuit and improves circuit reliability. Simultaneously, a feedback circuit achieves closed-loop control, monitoring the output voltage in real time and adjusting the power control chip to ensure a stable DC output voltage.

[0011] According to some embodiments of this application, the power control chip is model TNY280, and the bypass terminal of the power control chip is grounded to the output terminal of the constant current source circuit through a first capacitor.

[0012] According to some embodiments of this application, the front-end protection circuit includes a rectifier circuit, a first surge protection circuit, a front-end filter circuit, and a second surge protection circuit connected in sequence.

[0013] According to some embodiments of this application, the front-end filtering circuit includes a common-mode filter and an X capacitor. The positive input terminal and the negative input terminal of the common-mode filter are respectively connected to the positive output terminal and the negative output terminal of the first surge protection circuit. The X capacitor is connected between the positive output terminal and the negative output terminal of the common-mode filter, and the positive output terminal and the negative output terminal of the common-mode filter are respectively connected to the second surge protection circuit.

[0014] According to some embodiments of this application, the first surge protection circuit includes a thermistor and a varistor. One end of the thermistor is connected to the positive output terminal of the rectifier circuit, the other end of the thermistor is connected to one end of the varistor, and the other end of the varistor is connected to the negative output terminal of the rectifier circuit. The positive input terminal of the common-mode filter is connected between the thermistor and the varistor, and the negative input terminal of the common-mode filter is connected between the varistor and the negative output terminal of the rectifier circuit.

[0015] According to some embodiments of this application, the second surge protection circuit includes a first Y capacitor, a second Y capacitor, a first inductor, a first transient voltage suppressor transistor, and a first polarized capacitor. One end of the first Y capacitor, one end of the first transient voltage suppressor transistor, and the positive terminal of the first polarized capacitor are respectively connected to the positive output terminal of the common-mode filter. The other end of the first Y capacitor is connected to one end of the second Y capacitor and grounded. The other end of the second Y capacitor, the other end of the first transient voltage suppressor transistor, and the negative terminal of the first polarized capacitor are respectively connected to the negative output terminal of the common-mode filter.

[0016] According to some embodiments of this application, the constant current source circuit includes a first diode, a first resistor, a second resistor, a third resistor, a first switching transistor, a second switching transistor, a Zener diode, and a second diode. The positive terminal of the first diode is connected to an external power supply. The negative terminal of the first diode is connected to one end of the first resistor. The other end of the first resistor is connected to one end of the second resistor. The input terminal of the first switching transistor is connected between the first diode and the first resistor. The control terminal of the first switching transistor is connected between the first resistor and the second resistor. The output terminal of the first switching transistor is connected to one end of the third resistor. The other end of the third resistor is connected to the positive terminals of the Zener diode and the second diode, respectively. The negative terminal of the Zener diode is connected to the other end of the second resistor. The negative terminal of the second diode is connected to the bypass terminal of the power control chip. The input terminal of the second switching transistor is connected to the control terminal of the first switching transistor. The control terminal of the second switching transistor is connected to the other end of the second resistor. The output terminal of the second switching transistor is connected to one end of the third resistor.

[0017] According to some embodiments of this application, the clamping protection circuit includes a fourth resistor, a fifth resistor, a second capacitor, and a third diode. One end of the fourth resistor and one end of the second capacitor are respectively connected to the output terminal of the front-end protection circuit. One end of the fifth resistor is connected to the other end of the second capacitor. The other end of the fifth resistor is connected to the negative terminal of the third diode. The positive terminal of the third diode is connected to the input terminal of the power control chip.

[0018] According to some embodiments of this application, the back-end protection circuit includes a third capacitor, a fourth capacitor, a second polarity capacitor, and a second transient voltage suppressor. One end of the third capacitor, one end of the fourth capacitor, the positive terminal of the second polarity capacitor, and one end of the second transient voltage suppressor are respectively connected to the first end of the secondary winding of the high-frequency transformer. The other end of the third capacitor, the other end of the fourth capacitor, the negative terminal of the second polarity capacitor, and the other end of the second transient voltage suppressor are respectively connected to the second end of the secondary winding of the high-frequency transformer.

[0019] According to some embodiments of this application, the feedback circuit includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a fifth capacitor, an optocoupler, and a Zener diode. One end of the sixth resistor is connected to the output terminal of the back-end protection circuit. One end of the eighth resistor is grounded. The other ends of the sixth and eighth resistors are connected through the seventh resistor. One end of the ninth resistor is connected between the sixth and seventh resistors. The other end of the ninth resistor is connected to the negative terminal of the Zener diode and one end of the fifth capacitor. The other end of the fifth capacitor is connected between the seventh and eighth resistors and the reference terminal of the Zener diode. The positive terminal of the Zener diode is connected to one end of the eighth resistor and grounded. The anode of the optocoupler is connected between the sixth and seventh resistors. The cathode of the optocoupler is connected to one end of the fifth capacitor. The collector of the optocoupler is connected to the control terminal of the power control chip. The emitter of the optocoupler is connected to the output terminal of the power control chip and grounded.

[0020] Additional aspects and advantages of this application 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 this application. Attached Figure Description

[0021] Additional aspects and advantages of this application will become apparent and readily understood in conjunction with the following description of the embodiments, in which:

[0022] Figure 1 A circuit block diagram of the power supply circuit for the passive protection device provided in this application;

[0023] Figure 2 The circuit diagram of the power supply circuit for the passive protection device provided in this application.

[0024] The attached icons are numbered as follows:

[0025] Power supply circuit 100; front-end protection circuit 200; rectifier circuit 210; first surge protection circuit 220; front-end filter circuit 230; second surge protection circuit 240; main chip control circuit 300; constant current source circuit 310; clamping protection circuit 320; high-frequency transformer 330; power control chip 340; back-end protection circuit 400; feedback circuit 500. Detailed Implementation

[0026] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0027] In the description of this application, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., 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 application and 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 application.

[0028] In the description of this application, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0029] In the description of this application, unless otherwise expressly defined, terms such as "setup," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this application in conjunction with the specific content of the technical solution.

[0030] Passive protection devices play a crucial role in power systems and various electronic devices. However, the power supplies of currently available passive protection devices generally suffer from poor reliability. When the equipment is running, it is highly susceptible to external interference, especially surges. Surges generate instantaneous high voltage and large current. These abnormal electrical signals can impact the power supply circuit of the passive protection device, leading to unstable power output and, in severe cases, damage to power components. This can cause the passive protection device to malfunction, thereby affecting the safety and stability of the entire equipment system. Once a passive protection device fails, the equipment cannot be effectively protected when encountering faults or abnormal conditions, potentially leading to equipment failure, data loss, or even safety accidents.

[0031] Based on this, this application provides a power supply circuit for a passive protection device to solve the aforementioned technical problems. The technical solutions provided in this application will be described in detail below.

[0032] Reference Figure 1 This application provides a power supply circuit for a passive protection device, including: a power acquisition circuit 100, a front-end protection circuit 200, a main chip control circuit 300, a back-end protection circuit 400, and a feedback circuit 500. The power acquisition circuit 100 is used to obtain input voltage from an external source. The input terminal of the front-end protection circuit 200 is connected to the output terminal of the power acquisition circuit 100. The main chip control circuit 300 includes a constant current source circuit 310, a clamping protection circuit 320, a high-frequency transformer 330, and a power control chip 340. The input terminal of the constant current source circuit 310, the input terminal of the clamping protection circuit 320, and the first terminal of the primary winding of the high-frequency transformer 330 are respectively connected to the output terminal of the front-end protection circuit 200, and the input terminal of the power control chip 340 is connected to the output terminal of the front-end protection circuit 200. The power control chip 340 is connected to the output of the clamping protection circuit 320 and the second end of the primary winding of the high-frequency transformer 330, respectively. The bypass terminal of the power control chip 340 is connected to the output of the constant current source circuit 310, and the output of the power control chip 340 is grounded. The input terminal of the back-end protection circuit 400 is connected to the first end of the secondary winding and the second end of the secondary winding of the high-frequency transformer 330, respectively. The output of the back-end protection circuit 400 is used to output a stable DC voltage. The input terminal of the feedback circuit 500 is connected to the output terminal of the back-end protection circuit 400, and the output terminal of the feedback circuit 500 is connected to the control terminal of the power control chip 340. It is used to control the conduction degree of the power control chip 340 according to the DC voltage output by the back-end protection circuit 400.

[0033] In the power supply circuit of the passive protection device described above, the power supply circuit 100 obtains input voltage from the outside to provide the energy foundation for the entire circuit. The front-end protection circuit 200 preprocesses the input voltage, filters out external interference, and prevents excessive voltage and current from impacting subsequent circuits. In the main chip control circuit 300, the constant current source circuit 310 provides stable current to the power control chip 340. The clamping protection circuit 320 clamps the abnormally high voltage within a safe range. The high-frequency transformer 330 achieves voltage transformation and isolation through electromagnetic induction. The power control chip 340 controls its own conduction degree according to the signal from the feedback circuit 500, and adjusts the current and voltage of the primary winding of the high-frequency transformer 330 to achieve stable control of the output voltage. The back-end protection circuit 400 performs secondary processing on the voltage output from the secondary winding of the high-frequency transformer 330, and outputs a stable DC voltage for the load. The feedback circuit 500 collects the DC voltage signal output from the back end and feeds it back to the control terminal of the power control chip 340. The chip conduction degree is adjusted according to the voltage change to achieve closed-loop control to ensure stable output voltage. The front-end protection circuit 200 initially blocks the instantaneous high voltage and large current generated by surges. The clamping protection circuit 320, following the front-end protection circuit 200, further clamps any leaking abnormal high voltage to a safe value, preventing damage to subsequent circuit components and effectively resisting the impact of surges on the power supply circuit, thus improving circuit reliability. Simultaneously, closed-loop control is achieved through the feedback circuit 500, which monitors the output voltage in real time and adjusts the power control chip 340 to ensure a stable DC output voltage.

[0034] It is understood that the power control chip 340 is model TNY280, and the bypass terminal of the power control chip 340 is grounded to the output terminal of the constant current source circuit 310 through a first capacitor. The capacitance of the first capacitor can be 100nF, connected to the bypass pin of the TNY280, setting the current limit value to the standard current limit value, enabling high-frequency decoupling and energy storage. Additionally, the enable pin is turned on by the feedback circuit 500.

[0035] Reference Figure 1It is understood that the front-end protection circuit 200 includes a rectifier circuit 210, a first surge protection circuit 220, a front-end filter circuit 230, and a second surge protection circuit 240 connected in sequence. The rectifier circuit 210 converts the input AC power into DC power, providing a stable DC power supply foundation for subsequent circuits. The front-end filter circuit 230 filters the rectified DC voltage, removing noise and ripple, making the voltage input to the downstream circuits smoother and more stable. The first surge protection circuit 220 and the second surge protection circuit 240 work together to form a dual surge protection mechanism. The first surge protection circuit 220 can initially suppress instantaneous high voltage and large current when a surge occurs, reducing its amplitude. The second surge protection circuit 240 further processes any residual surge interference that may still exist after the initial protection, ensuring that the voltage and current entering the subsequent circuits are within a safe range, greatly enhancing the circuit's ability to withstand surges and ensuring the stable operation of the entire power supply circuit in harsh electrical environments.

[0036] Reference Figure 2 It is understood that the front-end filter circuit 230 includes a common-mode filter L1 and an X-capacitor CX1. The positive and negative input terminals of the common-mode filter L1 are connected to the positive and negative output terminals of the first surge protection circuit 220, respectively. The X-capacitor CX1 is connected between the positive and negative output terminals of the common-mode filter L1, and the positive and negative output terminals of the common-mode filter L1 are connected to the second surge protection circuit 240, respectively. The common-mode filter L1 mainly consists of an inductor and a capacitor. When current flows through the common-mode filter L1, for common-mode interference signals, since their magnitude and direction are the same on both wires, the inductor will generate a large impedance, thereby suppressing the transmission of common-mode interference signals. The X-capacitor CX1 is connected between the positive and negative output terminals of the common-mode filter L1 to bypass differential-mode interference. Differential-mode interference refers to interference signals that appear between the positive and negative terminals of the power supply. The X-capacitor CX1 has a low impedance for high-frequency differential-mode interference signals, which can short-circuit the high-frequency differential-mode interference signals to ground, thereby reducing the impact of differential-mode interference on subsequent circuits. With the cooperation of common-mode filter L1 and capacitor CX1, the front-end filter circuit 230 can comprehensively filter the power supply signal and remove common-mode and differential-mode interference.

[0037] Continue to refer to Figure 2It is understood that the first surge protection circuit 220 includes a thermistor NTC1 and a varistor VAR1. One end of the thermistor NTC1 is connected to the positive output terminal of the rectifier circuit 210, and the other end of the thermistor NTC1 is connected to one end of the varistor NTC1. The other end of the varistor NTC1 is connected to the negative output terminal of the rectifier circuit 210. The positive input terminal of the common-mode filter is connected between the thermistor NTC1 and the varistor NTC1, and the negative input terminal of the common-mode filter is connected between the varistor NTC1 and the negative output terminal of the rectifier circuit 210. The thermistor NTC1 has a positive temperature coefficient characteristic. Under normal operating conditions, its resistance is relatively small, and it does not significantly impede current flow in the circuit, allowing current to pass smoothly and ensuring normal power supply. When a surge occurs and the instantaneous current increases rapidly, the thermistor NTC1 will heat up due to the current's thermal effect, causing its resistance to increase rapidly. This limits further current increase, acting as a current limiter and preventing excessive current from damaging subsequent circuit components. Under normal voltage conditions, the varistor NTC1 has a very high resistance, almost like an open circuit, and has virtually no impact on the normal operation of the circuit. However, once a surge occurs and the voltage exceeds its threshold, the resistance of the varistor NTC1 drops sharply, quickly conducting and bypassing the high voltage generated by the surge to ground, thus effectively clamping the voltage and keeping it within a safe range to prevent high voltage from impacting subsequent circuits. In the first surge protection circuit 220, the thermistor NTC1 and the varistor NTC1 work together; the thermistor NTC1 limits the current, and the varistor NTC1 limits the voltage, jointly protecting against surges. The combination of thermistor NTC1 and varistor NTC1 achieves dual limitation of surge current and voltage, greatly improving the protection effect of the first surge protection circuit 220. It can effectively cope with various types of surge interference, providing reliable protection for the subsequent front-end filter circuit 230 and the entire power supply circuit, reducing the risk of surge damage to the circuit.

[0038] Reference Figure 2It is understood that the second surge protection circuit 240 includes a first Y capacitor CY1, a second Y capacitor CY2, a first inductor L2, a first transient voltage suppressor (TVS1), and a first polarized capacitor C2. One end of the first Y capacitor CY1 and one end of the first inductor L2 are connected to the positive output terminal of the common-mode filter L1. One end of the first transient voltage suppressor (TVS1) and the positive terminal of the first polarized capacitor C2 are connected to the other end of the first inductor L2. The other end of the first Y capacitor CY1 is connected to one end of the second Y capacitor CY2 and grounded. The other end of the second Y capacitor CY2, the other end of the first transient voltage suppressor (TVS1), and the negative terminal of the first polarized capacitor C2 are connected to the negative output terminal of the common-mode filter. During normal operation, the first Y capacitor CY1 and the second Y capacitor CY2 exhibit a certain capacitive reactance to AC signals. Since their capacitance values ​​are generally small, their impact on the normal operating current is minimal. When a surge voltage occurs, the first Y capacitor CY1 and the second Y capacitor CY2 can utilize their capacitive characteristics to absorb and bypass a portion of the high-frequency noise and surge energy, diverting it to the ground. Because the voltage across a capacitor cannot change abruptly, it can suppress rapid voltage changes to a certain extent. Meanwhile, the LC filter network composed of the first Y capacitor CY1, the second Y capacitor CY2, and the first inductor L2, in addition to protecting against surges, can effectively filter out high-frequency noise in the circuit, improving circuit stability and signal quality, enabling the circuit to operate more reliably, and reducing circuit failures and malfunctions caused by high-frequency interference.

[0039] Continue to refer to Figure 2 It can be understood that the constant current source circuit 310 includes a first diode D1, a first resistor R1, a second resistor R2, a third resistor R3, a first switch Q1, a second switch Q2, a Zener diode Z1, and a second diode D2. The positive terminal of the first diode D1 is connected to an external power supply, and the negative terminal of the first diode D1 is connected to one end of the first resistor R1. The other end of the first resistor R1 is connected to one end of the second resistor R2. The input terminal of the first switch Q1 is connected between the first diode D1 and the first resistor R1, and the control terminal of the first switch Q1 is connected between the first resistor R1 and the second resistor R2. Between the two resistors R2, the output terminal of the first switch Q1 is connected to one end of the third resistor R3. The other end of the third resistor R3 is connected to the positive terminal of Zener diode Z1 and the positive terminal of the second diode D2. The negative terminal of Zener diode Z1 is connected to the other end of the second resistor R2. The negative terminal of the second diode D2 is connected to the bypass terminal of the power control chip 340. The input terminal of the second switch Q2 is connected to the control terminal of the first switch Q1. The control terminal of the second switch Q2 is connected to the other end of the second resistor R2. The output terminal of the second switch Q2 is connected to one end of the third resistor R3.

[0040] An external power supply is connected to the circuit through a first diode D1. Diode D1 acts as an isolation element, preventing reverse current flow and protecting the power supply and circuit. Current flows through a first resistor R1 and a second resistor R2, forming a voltage divider. The input terminal of the first switch Q1 is connected between the first diode D1 and the first resistor R1, while its control terminal is connected between the first resistor R1 and the second resistor R2. When the voltage at the control terminal of the first switch Q1 reaches its conduction threshold, Q1 conducts, and current flows from its input terminal to its output terminal, passing through a third resistor R3. A Zener diode Z1 is connected in parallel with the second resistor R2. Zener diode Z1 acts as a voltage regulator; when the voltage across the second resistor R2 reaches its breakdown voltage, it reverse-biased, maintaining a stable voltage across it. The input terminal of the second switch Q2 is connected to the control terminal of the first switch Q1, the control terminal is connected to the other end of the second resistor R2, and its output terminal is connected to one end of the third resistor R3. The second switch Q2 assists in regulating the control of the first switch Q1. When the voltage across the second resistor R2 changes, the conduction state of the second switch Q2 also changes accordingly, thus affecting the conduction level of the first switch Q1 and playing a role in fine-tuning the current. The positive terminal of the second diode D2 is connected after the third resistor R3, and the negative terminal is connected to the bypass terminal of the power control chip 340. Through the coordinated work of the above components, the current flowing through the second diode D2 and finally reaching the bypass terminal of the power control chip 340 remains relatively constant. When the external power supply voltage fluctuates or the load changes, the circuit will adjust the conduction state of the first switch Q1 and the second switch Q2, as well as the voltage regulation effect of the Zener diode Z1, to ensure the stability of the output current.

[0041] Continue to refer to Figure 2It can be understood that the clamping protection circuit 320 includes a fourth resistor R4, a fifth resistor R5, a second capacitor C3, and a third diode D3. One end of the fourth resistor R4 and one end of the second capacitor C3 are connected to the output terminal of the front-end protection circuit 200, one end of the fifth resistor R5 is connected to the other end of the second capacitor C3, and the other end of the fifth resistor R5 is connected to the negative terminal of the third diode D3. The positive terminal of the third diode D3 is connected to the input terminal of the power control chip 340. The voltage output by the front-end protection circuit 200 first acts on the fourth resistor R4 and the second capacitor C3. The fourth resistor R4 and the second capacitor C3 form a simple RC circuit, improving the stability of the current. The fifth resistor R5 and the second capacitor C3 are connected in series, jointly dividing the voltage output by the front-end protection circuit 200. The third diode D3 has unidirectional conductivity. If the maximum safe voltage allowed at the input terminal of the power control chip 340 is Vmax, the voltage at the input terminal of the power control chip 340 will be limited to approximately Vmax + 0.7V through the clamping effect of the third diode D3, preventing excessive voltage from damaging the power control chip 340. The clamping protection circuit 320 can promptly limit these excessive voltages to a safe range, ensuring the stable and reliable operation of the power control chip 340, extending the chip's lifespan, and reducing repair and replacement costs caused by overvoltage damage.

[0042] Continue to refer to Figure 2It is understood that the back-end protection circuit 400 includes a third capacitor C5, a fourth capacitor C6, a second polarity capacitor C4, and a second transient voltage suppressor (TVS2). One end of the third capacitor C5, one end of the fourth capacitor C6, the positive terminal of the second polarity capacitor C4, and one end of the second transient voltage suppressor (TVS2) are respectively connected to the first terminal of the secondary winding of the high-frequency transformer T1. The other ends of the third capacitor C5, the other end of the fourth capacitor C6, the negative terminal of the second polarity capacitor C4, and the other end of the second transient voltage suppressor (TVS2) are respectively connected to the second terminal of the secondary winding of the high-frequency transformer T1. The third capacitor C5 and the fourth capacitor C6 are mainly used to filter out high-frequency noise, while the second polarity capacitor C4 is mainly used to smooth the output voltage and filter out low-frequency ripple. When the voltage rises, the capacitor charges and stores energy; when the voltage drops, the capacitor discharges and releases energy, thereby maintaining the relative stability of the output voltage. When a momentary high-voltage surge occurs at the output terminal of the secondary winding of the high-frequency transformer T1, the second transient voltage suppressor (TVS2) will respond quickly. Under normal operating voltage, the second transient voltage suppressor (TVS2) presents a high impedance state, having almost no impact on the normal operation of the circuit. However, when the surge voltage exceeds the breakdown voltage of the second TVS2, it immediately reverse-biased breakdown, rapidly diverting the surge current to ground. This clamps the output voltage within a safe range, protecting downstream load equipment from damage caused by high-voltage surges. The downstream protection circuit 400 reduces equipment failures and performance degradation caused by power fluctuations, improving the stability and reliability of the equipment.

[0043] Continue to refer to Figure 2It is understood that the feedback circuit 500 includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a fifth capacitor C7, an optocoupler U2, and a Zener diode U3. One end of the sixth resistor R6 is connected to the output terminal of the back-end protection circuit 400, one end of the eighth resistor R8 is grounded, and the other ends of the sixth resistor R6 and the eighth resistor R8 are connected through the seventh resistor R7. One end of the ninth resistor R9 is connected between the sixth resistor R6 and the seventh resistor R7, and the other end of the ninth resistor R9 is connected to the negative terminal of the Zener diode U3 and the fifth capacitor C7, respectively. One end of capacitor C7 is connected to the reference terminal of Zener diode U3, and the other end of capacitor C7 is connected between resistors R7 and R8. The positive terminal of Zener diode U3 is connected to one end of resistor R8 and grounded. The anode of optocoupler U2 is connected between resistors R6 and R7, and the cathode of optocoupler U2 is connected to one end of capacitor C7. The collector of optocoupler U2 is connected to the control terminal of power control chip 340, and the emitter of optocoupler U2 is connected to the output terminal of power control chip 340 and grounded. The stable DC voltage output by the back-end protection circuit 400 is first sampled by a voltage divider network composed of resistors R6, R7, and R8. Resistor R9, capacitor C7, and Zener diode U3 together form a voltage regulation and filtering circuit. Optocoupler U2 consists of a light-emitting diode and a phototransistor. A sampling voltage is applied to the anode and cathode of optocoupler U2. When the sampling voltage changes, it alters the luminous intensity of the LED, causing the phototransistor to generate a corresponding current change based on the received light intensity. The collector of optocoupler U2 is connected to the control terminal of power control chip 340, while its emitter is grounded. When the output voltage of the back-end protection circuit 400 changes, the sampling voltage also changes accordingly, affecting the output current of optocoupler U2. Power control chip 340 adjusts its conduction level based on the received current signal, thereby changing the current and voltage of the primary winding of high-frequency transformer 330, ultimately regulating the output voltage of back-end protection circuit 400 to maintain stability. The output voltage can be adjusted by the ratio of the seventh resistor R7 to the eighth resistor R8. Feedback circuit 500 samples the output voltage of back-end protection circuit 400 in real time and feeds it back to power control chip 340, forming a closed-loop control system. This closed-loop control automatically adjusts the power supply output, ensuring stability under different load conditions and input voltage fluctuations, meeting the requirements of passive protection devices for a stable power supply, and improving the stability and reliability of the entire power circuit.

[0044] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

Claims

1. A power supply circuit for a passive protection device, characterized in that, include: Power supply circuit, used to obtain input voltage from an external source; A front-end protection circuit, wherein the input terminal of the front-end protection circuit is connected to the output terminal of the power-taking circuit; The main chip control circuit includes a constant current source circuit, a clamping protection circuit, a high-frequency transformer, and a power control chip. The input terminal of the constant current source circuit, the input terminal of the clamping protection circuit, and the first terminal of the primary winding of the high-frequency transformer are respectively connected to the output terminal of the front-end protection circuit. The input terminal of the power control chip is connected to the output terminal of the clamping protection circuit and the second terminal of the primary winding of the high-frequency transformer. The bypass terminal of the power control chip is connected to the output terminal of the constant current source circuit, and the output terminal of the power control chip is grounded. The back-end protection circuit has its input terminals connected to the first terminal and the second terminal of the secondary winding of the high-frequency transformer, respectively, and its output terminal is used to output a stable DC voltage. A feedback circuit is provided, wherein the input terminal of the feedback circuit is connected to the output terminal of the back-end protection circuit, and the output terminal of the feedback circuit is connected to the control terminal of the power control chip, for controlling the conduction degree of the power control chip according to the DC voltage output by the back-end protection circuit.

2. The power supply circuit of the passive protection device according to claim 1, characterized in that, The power control chip is model TNY280, and the bypass terminal of the power control chip is grounded to the output terminal of the constant current source circuit through a first capacitor.

3. The power supply circuit of the passive protection device according to claim 1, characterized in that, The front-end protection circuit includes a rectifier circuit, a first surge protection circuit, a front-end filter circuit, and a second surge protection circuit connected in sequence.

4. The power supply circuit of the passive protection device according to claim 3, characterized in that, The front-end filtering circuit includes a common-mode filter and an X capacitor. The positive and negative input terminals of the common-mode filter are connected to the positive and negative output terminals of the first surge protection circuit, respectively. The X capacitor is connected between the positive and negative output terminals of the common-mode filter, and the positive and negative output terminals of the common-mode filter are connected to the second surge protection circuit, respectively.

5. The power supply circuit of the passive protection device according to claim 4, characterized in that, The first surge protection circuit includes a thermistor and a varistor. One end of the thermistor is connected to the positive output terminal of the rectifier circuit, and the other end of the thermistor is connected to one end of the varistor. The other end of the varistor is connected to the negative output terminal of the rectifier circuit. The positive input terminal of the common-mode filter is connected between the thermistor and the varistor, and the negative input terminal of the common-mode filter is connected between the varistor and the negative output terminal of the rectifier circuit.

6. The power supply circuit of the passive protection device according to claim 4, characterized in that, The second surge protection circuit includes a first Y capacitor, a second Y capacitor, a first inductor, a first transient voltage suppressor transistor, and a first polarized capacitor. One end of the first Y capacitor and one end of the first inductor are respectively connected to the positive output terminal of the common-mode filter. One end of the first transient voltage suppressor transistor and the positive terminal of the first polarized capacitor are respectively connected to the other end of the first inductor. The other end of the first Y capacitor is connected to one end of the second Y capacitor and grounded. The other end of the second Y capacitor, the other end of the first transient voltage suppressor transistor, and the negative terminal of the first polarized capacitor are respectively connected to the negative output terminal of the common-mode filter.

7. The power supply circuit of the passive protection device according to claim 1, characterized in that, The constant current source circuit includes a first diode, a first resistor, a second resistor, a third resistor, a first switching transistor, a second switching transistor, a Zener diode, and a second diode. The positive terminal of the first diode is connected to an external power supply. The negative terminal of the first diode is connected to one end of the first resistor. The other end of the first resistor is connected to one end of the second resistor. The input terminal of the first switching transistor is connected between the first diode and the first resistor. The control terminal of the first switching transistor is connected between the first resistor and the second resistor. The output terminal of the first switching transistor is connected to one end of the third resistor. The other end of the third resistor is connected to the positive terminals of the Zener diode and the second diode, respectively. The negative terminal of the Zener diode is connected to the other end of the second resistor. The negative terminal of the second diode is connected to the bypass terminal of the power control chip. The input terminal of the second switching transistor is connected to the control terminal of the first switching transistor. The control terminal of the second switching transistor is connected to the other end of the second resistor. The output terminal of the second switching transistor is connected to one end of the third resistor.

8. The power supply circuit of the passive protection device according to claim 1, characterized in that, The clamping protection circuit includes a fourth resistor, a fifth resistor, a second capacitor, and a third diode. One end of the fourth resistor and one end of the second capacitor are respectively connected to the output terminal of the front-end protection circuit. One end of the fifth resistor is connected to the other end of the second capacitor. The other end of the fifth resistor is connected to the negative terminal of the third diode. The positive terminal of the third diode is connected to the input terminal of the power control chip.

9. The power supply circuit of the passive protection device according to claim 1, characterized in that, The back-end protection circuit includes a third capacitor, a fourth capacitor, a second polarity capacitor, and a second transient voltage suppressor. One end of the third capacitor, one end of the fourth capacitor, the positive terminal of the second polarity capacitor, and one end of the second transient voltage suppressor are respectively connected to the first end of the secondary winding of the high-frequency transformer. The other end of the third capacitor, the other end of the fourth capacitor, the negative terminal of the second polarity capacitor, and the other end of the second transient voltage suppressor are respectively connected to the second end of the secondary winding of the high-frequency transformer.

10. The power supply circuit of the passive protection device according to claim 1, characterized in that, The feedback circuit includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a fifth capacitor, an optocoupler, and a Zener diode. One end of the sixth resistor is connected to the output terminal of the back-end protection circuit. One end of the eighth resistor is grounded. The other ends of the sixth and eighth resistors are connected through the seventh resistor. One end of the ninth resistor is connected between the sixth and seventh resistors. The other end of the ninth resistor is connected to the negative terminal of the Zener diode and one end of the fifth capacitor. The other end of the fifth capacitor is connected between the seventh and eighth resistors and the reference terminal of the Zener diode. The positive terminal of the Zener diode is connected to one end of the eighth resistor and grounded. The anode of the optocoupler is connected between the sixth and seventh resistors. The cathode of the optocoupler is connected to one end of the fifth capacitor. The collector of the optocoupler is connected to the control terminal of the power control chip. The emitter of the optocoupler is connected to the output terminal of the power control chip and grounded.

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