A switching power supply fault monitoring circuit

Abstract

The present invention discloses a switching power supply fault monitoring circuit, comprising a rectifier, a DC-DC converter and an MCU. The rectifier is used for rectifying a three-phase AC input voltage, and then outputting the voltage after high-frequency conversion and voltage reduction through the DC-DC converter. A sampling detection unit is also arranged between the rectifier and the MCU. The sampling detection unit comprises a voltage sampling circuit, an amplifying and conditioning circuit and a comparative stabilization circuit connected in sequence. The MCU controls the working state of the DC-DC converter according to the output level signal received from the comparative stabilization circuit, and plays a good protective role when a switching power supply fails. The present invention designs a fault detection circuit and adopts a voltage sensor to perform real-time sampling on the output voltage of the rectifier, so as to effectively eliminate the influence of ripple interference and voltage source disturbance on the voltage sampling process, and effectively improve the accuracy of switching power supply fault monitoring.

Description

Technical Field

[0001] The invention relates to the technical field of switching power supplies, and mainly relates to a switching power supply fault monitoring circuit. Background Art

[0002] Switching power supplies are mainly divided into DC switching power supplies and AC switching power supplies, that is, the input is a DC power supply or AC power supply with poor power quality, which is converted into a DC voltage or AC voltage with higher quality that meets the requirements of the equipment. Among them, the core of the DC switching power supply is the DC-DC converter. The switching power supply is generally controlled by the controller MCU through pulse width modulation (PWM) to control the working state of the switching power supply, so as to keep the output voltage stable. During use, the switching power supply is affected by factors such as corrosion from the external environment, its own electrical insulation performance and stability. It is necessary to design a fault detection circuit in the control circuit to play a certain role in fault monitoring of the switching power supply. However, the switching power supply often has ripple interference and voltage source disturbance during the rectification and inversion process, resulting in the presence of clutter in the process of sampling the control circuit voltage, which affects the accuracy of detection. Therefore, the accuracy of switching power supply fault monitoring needs to be improved. Summary of the invention

[0003] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a switching power supply fault monitoring circuit.

[0004] The object of the present invention is achieved through the following technical solutions: A switching power supply fault monitoring circuit, comprising a rectifier, a DC-DC converter and an MCU, wherein the rectifier is used to rectify a three-phase AC input voltage, and then the voltage is converted at high frequency and stepped down by the DC-DC converter for output, a sampling detection unit is also arranged between the rectifier and the MCU, the sampling detection unit comprises a voltage sampling circuit, an amplification and conditioning circuit and a comparative stability circuit connected in sequence, and the MCU controls the working state of the DC-DC converter according to the output level signal received from the comparative stability circuit.

[0005] Preferably, the voltage sampling circuit includes a voltage sensor J1, a pin 1 of the voltage sensor J1 is connected to resistors R1, R2, and one end of a capacitor C1, a pin 2 of the voltage sensor J1 is connected in parallel with the other ends of the resistor R1 and the capacitor C1 and is grounded, the other end of the resistor R2 is connected to one end of the capacitor C2, the collector of the transistor VT1 and the gate of the MOS tube Q1, the other end of the capacitor C2 is grounded, the emitter of the transistor VT1 is connected to a +5V power supply, the base of the transistor VT1 is connected to the drain of the MOS tube Q1, the source of the MOS tube Q1 is grounded through the resistor R3, and is connected to the input end of the amplification and conditioning circuit through the capacitor C3.

[0006] Preferably, the amplification and conditioning circuit includes an op amp U1A, the inverting input terminal of the op amp U1A is connected to the output terminal of the voltage sampling circuit through a resistor R4, the non-inverting input terminal of the op amp U1A is connected to a resistor R6 and one end of a capacitor C4, and is grounded through a resistor R5, the output terminal of the op amp U1A is connected to a resistor R7, one end of a capacitor C5 and a base of a transistor VT2, the collector of the transistor VT2 and the other end of the resistor R7 are connected to a +5V power supply, the emitter of the transistor VT2 is connected to the other ends of resistors R6, capacitors C4 and C5, and is connected to the input terminal of the relatively stable circuit through a capacitor C6.

[0007] Preferably, the relatively stable circuit includes an op amp U1B, the inverting input terminal of the op amp U1B is connected to the output terminal of the amplification and conditioning circuit, the non-inverting input terminal of the op amp U1B is connected to one end of the resistor R8 and the cathode of the voltage zener diode DZ1, the other end of the resistor R8 is connected to a +10V power supply, the anode of the voltage zener diode DZ1 is grounded, the output terminal of the op amp U1B is connected to the non-inverting input terminal of the op amp U2A, and the inverting input terminal of the op amp U2A is connected to the output terminal of the op amp U2A and the voltage detection port of the MCU through a capacitor C7.

[0008] Preferably, an EMI filter is also provided between the three-phase AC input voltage and the rectifier.

[0009] Through the above technical solution, the beneficial effects of the present invention are:

[0010] 1. The present invention designs a fault detection circuit, uses a voltage sensor J1 to sample the output voltage of the rectifier in real time, and uses the principle of a π-type RC filter circuit to perform noise reduction on the sampled signal to reduce the interference of the ripple voltage;

[0011] 2. The amplifier and conditioning circuit uses RC feedback to compensate the output signal of the op amp U1A, effectively eliminating the interference of the voltage source disturbance on the sampling signal, and plays a good stabilizing role. Effectively improve the accuracy of switching power supply fault monitoring;

[0012] 3. The operational amplifier U1B uses the comparator principle to compare and output the output signal of the amplification and conditioning circuit. The MCU controls the working state of the DC-DC converter according to the output level signal of the receiving comparatively stable circuit, which plays a good protective role when the switching power supply fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a structural schematic diagram of the present invention.

[0014] Figure 2 This is a schematic diagram of the voltage sampling circuit of the present invention.

[0015] Figure 3This is the schematic diagram of the amplification and conditioning circuit of the present invention.

[0016] Figure 4 This is a relatively stable circuit schematic diagram of the present invention. DETAILED DESCRIPTION

[0017] The above and other technical contents, features and effects of the present invention are described in detail below with reference to the attached Figure 1 To Attachment Figure 4 The detailed description of the embodiments will clearly show that the structural contents mentioned in the following embodiments are all based on the drawings in the specification.

[0018] Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

[0019] like Figure 1 As shown, a switching power supply fault monitoring circuit includes a rectifier, a DC-DC converter and an MCU. The rectifier is used to rectify the three-phase AC input voltage, and then the DC-DC converter converts it at high frequency and outputs it after voltage reduction. An EMI filter is also provided between the three-phase AC input voltage and the rectifier, which has a good inhibitory effect on the high-frequency interference in the three-phase AC input voltage. When used specifically, the three-phase AC input voltage is set to an AC 690V input, which is converted into a DC 960V output after filtering by the EMI filter and three-phase rectification by the rectifier, and then a 400V DC voltage is output after high-frequency conversion and voltage reduction by the DC-DC converter.

[0020] In order to improve the accuracy of switching power supply fault monitoring, a sampling detection unit is arranged between the rectifier and the MCU. The sampling detection unit includes a voltage sampling circuit, an amplification and conditioning circuit and a comparative stability circuit connected in sequence. The MCU controls the working state of the DC-DC converter according to the output level signal received from the comparative stability circuit.

[0021] like Figure 2As shown, the voltage sampling circuit includes a voltage sensor J1, and the voltage sensor J1 is used to sample the output voltage after three-phase rectification. Pin 1 of the voltage sensor J1 is connected to one end of the resistors R1, R2, and capacitor C1, and pin 2 of the voltage sensor J1 is connected to the other end of the resistor R1 and capacitor C1 in parallel and grounded, and the other end of the resistor R2 is connected to one end of the capacitor C2, the collector of the transistor VT1, and the gate of the MOS tube Q1, and the other end of the capacitor C2 is grounded, the emitter of the transistor VT1 is connected to the +5V power supply, the base of the transistor VT1 is connected to the drain of the MOS tube Q1, and the source of the MOS tube Q1 is grounded through the resistor R3, and connected to the input end of the amplification and conditioning circuit through the capacitor C3. Among them, the sampling signal output by the voltage sensor J1 is first sent to the π-type RC filter circuit formed by the capacitors C1, C2, and the resistor R2 for noise reduction processing to reduce the interference of the ripple voltage. Then, a combined amplifier tube formed by transistor VT1 and MOS tube Q1 is used to amplify the sampling signal. Since the MOS tube itself has good temperature characteristics, the temperature noise in the sampling signal is reduced while the amplification efficiency is improved, thereby effectively improving the accuracy of voltage sampling.

[0022] In order to avoid disturbances in the internal control circuit of the switching power supply that interfere with the stability of the sampling signal, the output signal of the MOS tube Q1 is coupled by capacitor C3 and sent to the amplification and conditioning circuit for adjustment. Figure 3 As shown, the amplification and conditioning circuit includes an amplifier U1A, the inverting input end of the amplifier U1A is connected to the output end of the voltage sampling circuit through a resistor R4, the in-phase input end of the amplifier U1A is connected to a resistor R6, one end of a capacitor C4, and grounded through a resistor R5, the output end of the amplifier U1A is connected to a resistor R7, one end of a capacitor C5 and the base of a transistor VT2, the collector of the transistor VT2 and the other end of the resistor R7 are connected to a +5V power supply, the emitter of the transistor VT2 is connected to the other end of the resistor R6, the capacitor C4, and the C5, and connected to the input end of a relatively stable circuit through a capacitor C6. The transistor VT2 forms an emitter follower at the output end of the amplifier U1A to improve the driving ability of the sampling signal, and at the same time, during the amplification process of the amplifier U1A, the resistor R6 and the capacitor C4 form a resistor-capacitor feedback to compensate the output signal of the amplifier U1A, effectively eliminating the interference of the voltage source disturbance on the sampling signal, and playing a good stabilizing role.

[0023] like Figure 4As shown, the output signal of the amplification and conditioning circuit is sent to a relatively stable circuit for potential comparison. The relatively stable circuit includes an op amp U1B, the inverting input of the op amp U1B is connected to the output of the amplification and conditioning circuit, the non-inverting input of the op amp U1B is connected to one end of the resistor R8 and the cathode of the voltage zener diode DZ1, the other end of the resistor R8 is connected to the +10V power supply, the anode of the voltage zener diode DZ1 is grounded, the output of the op amp U1B is connected to the non-inverting input of the op amp U2A, and the inverting input of the op amp U2A is connected to the output of the op amp U2A and the voltage detection port of the MCU through the capacitor C7. Among them, the op amp U1B uses the comparator principle to compare and output the output signal of the amplification and conditioning circuit, the +10V power supply potential is used as the preset safety potential value of the non-inverting input of the op amp U1B, and the voltage zener diode DZ1 stabilizes the preset safety potential value. The op amp U2A isolates the output level signal of the op amp U1B and outputs it to the MCU to improve the stability of voltage sampling detection.

[0024] When the present invention is used in a specific manner, when the output voltage after the rectifier is within 1000V, the potential value of the sampling signal of the voltage sensor J1 input to the inverting input terminal of the operational amplifier U1B after processing is less than the preset safety potential value, so the operational amplifier U1B outputs a high-level signal, and this high-level signal is sent to the MCU after being isolated and output by the operational amplifier U2A. After receiving the high-level signal, the MCU controls the DC-DC converter to work normally; on the contrary, when the output voltage after the rectifier is higher than 1000V, the potential value of the inverting input terminal of the operational amplifier U1B is greater than the preset safety potential value, thereby outputting a low-level signal. After receiving the low-level signal, the MCU controls the DC-DC converter to stop working and cut off the output, thereby playing a good protective role when a switching power supply fails. Among them, the above-mentioned specific voltage values ​​are set according to the corresponding three-phase AC input voltage values, and the above-mentioned embodiment cannot determine that the specific implementation of the present invention is limited to this.

[0025] In summary, the present invention designs a fault detection circuit, uses a voltage sensor J1 to sample the output voltage of the rectifier in real time, uses the principle of a π-type RC filter circuit to perform noise reduction processing on the sampled signal, and reduces the interference of the ripple voltage; the amplifier and conditioning circuit uses resistance-capacitance feedback to compensate the output signal of the operational amplifier U1A, effectively eliminating the interference of the voltage source disturbance on the sampled signal, and plays a good stabilizing role; the operational amplifier U1B uses the comparator principle to compare and output the output signal of the amplifier and conditioning circuit, and the MCU controls the working state of the DC-DC converter according to the output level signal of the receiving comparatively stable circuit, and plays a good protective role when the switching power supply fails. The circuit design is simple and ingenious, and can effectively eliminate the influence of ripple interference and voltage source disturbance on the voltage sampling process, and effectively improve the accuracy of switching power supply fault monitoring.

[0026] The above is a further detailed description of the present invention in combination with a specific implementation method, and it cannot be determined that the specific implementation of the present invention is limited to this; for technical personnel in the technical field to which the present invention belongs and related technical fields, based on the technical solution of the present invention, the expansion and replacement of operating methods and data should all fall within the protection scope of the present invention.

Claims

1. A switching power supply fault monitoring circuit, characterized in that: It includes a rectifier, a DC-DC converter and an MCU. The rectifier is used to rectify the three-phase AC input voltage, and then the DC-DC converter performs high-frequency conversion and outputs the voltage after stepping down. A sampling detection unit is also arranged between the rectifier and the MCU. The sampling detection unit includes a voltage sampling circuit, an amplification and conditioning circuit and a comparative stability circuit connected in sequence. The MCU controls the working state of the DC-DC converter according to the output level signal of the comparative stability circuit received; The voltage sampling circuit includes a voltage sensor J1, wherein a pin 1 of the voltage sensor J1 is connected to resistors R1, R2, and one end of a capacitor C1, a pin 2 of the voltage sensor J1 is connected in parallel with the other ends of the resistor R1 and the capacitor C1 and is grounded, the other end of the resistor R2 is connected to one end of the capacitor C2, the collector of the transistor VT1, and the gate of the MOS transistor Q1, the other end of the capacitor C2 is grounded, the emitter of the transistor VT1 is connected to a +5V power supply, the base of the transistor VT1 is connected to the drain of the MOS transistor Q1, the source of the MOS transistor Q1 is grounded through a resistor R3, and is connected to the input end of the amplification and conditioning circuit through a capacitor C3; The amplification and conditioning circuit includes an operational amplifier U1A, an inverting input terminal of the operational amplifier U1A is connected to the output terminal of the voltage sampling circuit through a resistor R4, a non-inverting input terminal of the operational amplifier U1A is connected to a resistor R6 and one end of a capacitor C4, and is grounded through a resistor R5, an output terminal of the operational amplifier U1A is connected to a resistor R7, one end of a capacitor C5 and a base of a transistor VT2, a collector of the transistor VT2 and the other end of the resistor R7 are connected to a +5V power supply, an emitter of the transistor VT2 is connected to the other ends of the resistors R6, capacitors C4 and C5, and is connected to the input terminal of the comparatively stable circuit through a capacitor C6; The relatively stable circuit includes an op amp U1B, an inverting input terminal of the op amp U1B is connected to the output terminal of the amplification and conditioning circuit, a non-inverting input terminal of the op amp U1B is connected to one end of a resistor R8 and a cathode of a voltage-stabilizing diode DZ1, the other end of the resistor R8 is connected to a +10V power supply, an anode of the voltage-stabilizing diode DZ1 is grounded, an output terminal of the op amp U1B is connected to the non-inverting input terminal of the op amp U2A, and an inverting input terminal of the op amp U2A is connected to the output terminal of the op amp U2A and a voltage detection port of the MCU via a capacitor C7.

2. The switching power supply fault monitoring circuit according to claim 1, characterized in that: An EMI filter is also provided between the three-phase AC input voltage and the rectifier.

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