A direct current blocking capacitor protection circuit

Abstract

This utility model relates to the field of electronic circuit technology and discloses a DC blocking capacitor protection circuit, including a power transformer primary side, a DC blocking capacitor protection module, a fault detection module, and an alarm module. The power transformer primary side is electrically connected to the DC blocking capacitor protection module, the DC blocking capacitor protection module is electrically connected to the fault detection module, and the fault detection module is signal-connected to the alarm module. In this utility model, the power transformer primary side is a critical node for electrical energy input and also the "source" of DC bias problems. By connecting the DC blocking capacitor in series with the primary side, the DC component can be precisely blocked from entering the transformer without affecting the transfer of AC energy.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuit technology, and in particular to a DC blocking capacitor protection circuit. Background Technology

[0002] In the field of modern power electronics, phase-shifted full-bridge circuits are widely used in switching power supplies, new energy vehicle charging piles, industrial motor drives, and many other scenarios due to their high efficiency, high power density, and good electrical isolation performance. However, this circuit has a problem that cannot be ignored: the DC bias magnetization phenomenon of the power transformer.

[0003] Due to factors such as inconsistencies in the parameters of power devices in the circuit, asymmetry in the drive signal, and minor errors in the control circuit, a DC component can flow into the primary winding of the power transformer. The presence of this DC component causes unidirectional magnetization of the transformer core, i.e., magnetic deflection. Once the magnetic deflection intensifies, the core will rapidly saturate, causing a sharp decrease in the transformer's inductance and a significant increase in the magnetizing current. This not only leads to severe transformer overheating and reduced efficiency but may also cause overcurrent damage to power devices, or even paralyze the entire circuit system. Therefore, it is necessary to develop a DC blocking capacitor protection circuit. Utility Model Content

[0004] To overcome the above deficiencies, this utility model provides a DC blocking capacitor protection circuit, which aims to improve the problem in the prior art where DC components flow into the primary side of the power transformer due to factors such as inconsistency of power device parameters, asymmetry of drive signals, and minor errors in the control circuit, causing magnetic deflection of the transformer core.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a DC blocking capacitor protection circuit, comprising a power transformer primary side, a DC blocking capacitor protection module, a fault detection module, and an alarm module, wherein the power transformer primary side is electrically connected to the DC blocking capacitor protection module, the DC blocking capacitor protection module is electrically connected to the fault detection module, and the fault detection module is signal-connected to the alarm module.

[0006] Preferably, the DC blocking capacitor protection module includes a 4.7μF / 630V film capacitor and a 100kΩ voltage equalization resistor, with the 4.7μF / 630V film capacitor connected in series with the primary side of the power transformer.

[0007] Preferably, the 4.7μF / 630V film capacitor is connected in parallel with a 100kΩ equalizing resistor.

[0008] Preferably, the fault detection module includes a voltage sensor and a deviation comparator.

[0009] Preferably, the two sampling terminals of the voltage sensor are connected in parallel to the positive and negative terminals of the 4.7μF / 630V film capacitor, respectively, to monitor the differential voltage signal across the 4.7μF / 630V film capacitor.

[0010] Preferably, the output signal of the voltage sensor is connected to the input of the deviation comparator.

[0011] Preferably, the output signal of the deviation comparator is connected to the input of the alarm module.

[0012] Preferably, the alarm module includes an indicator light and a buzzer, used to provide an audible and visual alarm when a trigger signal is received.

[0013] This utility model has the following beneficial effects:

[0014] 1. In this utility model, the primary side of the power transformer is the key node for electrical energy input and the "source" of DC bias problem. By connecting the DC blocking capacitor in series on the primary side, the DC component can be precisely blocked from entering the transformer without affecting the transmission of AC energy. Furthermore, through a real-time monitoring and alarm mechanism, early warning can be given in the early stage of capacitor failure to prevent the fault from worsening, thereby significantly extending the service life of the capacitor and ensuring the stable operation of the phase-shifted full-bridge circuit.

[0015] 2. In this utility model, the modular design clearly demonstrates the working process of the DC blocking capacitor protection circuit, forming a complete protection chain from hardware connection to signal processing, which facilitates circuit debugging and later maintenance, and can improve the stability and reliability of the entire circuit system. Attached Figure Description

[0016] Figure 1 This is a schematic block diagram of a DC blocking capacitor protection circuit proposed in this utility model.

[0017] Figure 2 This is a schematic block diagram of a DC blocking capacitor protection module for a DC blocking capacitor protection circuit proposed in this utility model.

[0018] Figure 3 This is a schematic block diagram of a fault detection module for a DC blocking capacitor protection circuit proposed in this utility model. Detailed Implementation

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

[0020] Reference Figures 1-3 The present invention provides an embodiment of a DC blocking capacitor protection circuit, comprising a power transformer primary side, a DC blocking capacitor protection module, a fault detection module, and an alarm module. The power transformer primary side is electrically connected to the DC blocking capacitor protection module, the DC blocking capacitor protection module is electrically connected to the fault detection module, and the fault detection module is signal-connected to the alarm module.

[0021] Specifically, the 4.7μF / 630V film capacitor connected in series in the DC blocking capacitor protection module exhibits high impedance characteristics to the DC component. After being connected to the primary side of the power transformer, it can effectively prevent DC current from flowing into the transformer. This is because DC current entering the transformer will cause DC bias in the magnetic core, leading to core saturation, increased losses, overheating, and even damage to the transformer. By blocking DC, the magnetic bias phenomenon in the transformer can be avoided, ensuring the normal operation of the transformer. The fault detection module can monitor the capacitor voltage difference in real time. When it exceeds the 10% threshold, it triggers an audible and visual alarm and system signal transmission. The alarm module can execute alarm actions after the deviation comparator determines the fault.

[0022] Reference Figures 1-3 The DC blocking capacitor protection module includes a 4.7μF / 630V film capacitor and a 100kΩ voltage equalizing resistor. The 4.7μF / 630V film capacitor is connected in series with the primary side of the power transformer; the 4.7μF / 630V film capacitor is connected in parallel with the 100kΩ voltage equalizing resistor.

[0023] Specifically, by connecting a 4.7μF / 630V film capacitor in the DC blocking capacitor protection module in series with the primary side of the power transformer in the phase-shifted full-bridge main circuit, DC current can be effectively blocked from entering the primary side of the power transformer. This prevents core saturation of the transformer due to DC bias, avoiding problems such as increased heating, increased losses, or even damage, and ensuring stable operation of the transformer. By connecting a 100kΩ voltage-equalizing resistor in parallel with the film capacitor in the DC blocking capacitor protection module, the voltage can be evenly distributed when multiple capacitors are connected in series, preventing damage to the capacitors due to uneven voltage distribution and improving the reliability of the DC blocking capacitor and the entire circuit.

[0024] Reference Figures 1-3 The fault detection module includes a voltage sensor and a deviation comparator; the two sampling terminals of the voltage sensor are connected in parallel to the positive and negative terminals of a 4.7μF / 630V film capacitor, respectively, to monitor the voltage difference signal across the 4.7μF / 630V film capacitor.

[0025] Specifically, the voltage sensor can monitor the voltage difference across the thin-film capacitor in real time, thereby enabling timely detection of voltage fluctuations caused by changes in capacitor performance, aging, or circuit abnormalities.

[0026] Reference Figures 1-3The output signal of the voltage sensor is connected to the input of the deviation comparator; the output signal of the deviation comparator is connected to the input of the alarm module; the alarm module includes an indicator light and a buzzer, which are used to provide audible and visual alarms when a trigger signal is received.

[0027] Specifically, the voltage sensor transmits the collected differential pressure signal to the deviation comparator in the fault detection module, providing a data basis for subsequent judgment. This allows the system to accurately grasp the working status of the capacitor. The deviation comparator compares the received differential pressure signal with a preset value. When the deviation is greater than 10%, a trigger signal is sent to the alarm module, prompting the alarm module to execute an alarm action. Then, the alarm module issues an alarm through indicator lights, buzzers, etc., to remind staff that there is a problem with the capacitor or circuit, so that it can be dealt with in a timely manner, prevent the fault from escalating, extend the service life of the DC blocking capacitor, and ensure the safe and stable operation of the entire circuit system.

[0028] Working Principle: In operation, the electrical energy generated by the phase-shifted full-bridge main circuit is first transmitted to the primary side of the power transformer. Then, a 4.7μF / 630V film capacitor in the DC blocking capacitor protection module is connected in series with the primary side of the power transformer. Utilizing the capacitor's high impedance to DC and low impedance to AC, it blocks DC components from entering the transformer, preventing magnetic deflection. A 100kΩ voltage equalization resistor is connected in parallel with the film capacitor to ensure uniform voltage distribution, preventing damage to the capacitor due to uneven voltage. The voltage sensor in the fault detection module samples the voltage difference across the 4.7μF / 630V film capacitor, acquiring the voltage difference signal and transmitting it to the deviation comparator. The deviation comparator compares this signal with a preset value. If the voltage difference deviation is greater than 10%, it determines that the capacitor or circuit is abnormal and sends a control signal to the alarm module. The alarm module then triggers a local alarm by flashing an indicator light and sounding a buzzer, alerting staff to handle the situation promptly, preventing the fault from escalating and extending the capacitor's lifespan. Through the coordinated operation of the voltage sensor, deviation comparator, and alarm module, from signal acquisition and analysis to alarm execution, real-time monitoring of the capacitor's status and fault early warning are achieved.

[0029] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A DC blocking capacitor protection circuit, comprising a power transformer primary winding, a DC blocking capacitor protection module, a fault detection module, and an alarm module, characterized in that: The primary side of the power transformer is electrically connected to a DC blocking capacitor protection module, which is electrically connected to a fault detection module. The fault detection module is signal-connected to an alarm module. The DC blocking capacitor protection module includes a 4.7μF / 630V film capacitor and a 100kΩ voltage equalization resistor. The 4.7μF / 630V film capacitor is connected in series with the primary side of the power transformer. The 4.7μF / 630V film capacitor is connected in parallel with the 100kΩ voltage equalization resistor. The fault detection module includes a voltage sensor and a deviation comparator. The two sampling terminals of the voltage sensor are connected in parallel with the positive and negative terminals of the 4.7μF / 630V film capacitor, respectively, to monitor the voltage difference signal across the 4.7μF / 630V film capacitor. The alarm module includes an indicator light and a buzzer for audible and visual alarms when a trigger signal is received.

2. The DC blocking capacitor protection circuit according to claim 1, characterized in that: The output signal of the voltage sensor is connected to the input of the deviation comparator.

3. The DC blocking capacitor protection circuit according to claim 1, characterized in that: The output signal of the deviation comparator is connected to the input of the alarm module.

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