Small circuit breaker switching power supply circuit

Abstract

A small circuit breaker switching power supply circuit, comprising an input power protection circuit, a standby current limiting circuit, an AC-DC switching power supply circuit, a motor working circuit, a power supply step-down circuit and a control circuit including an MCU; the input power protection circuit, the standby current limiting circuit and the AC-DC switching power supply circuit are connected in sequence, the AC-DC switching power supply circuit is respectively connected to the motor working circuit and the power supply step-down circuit, the motor working circuit is used to drive the motor and provide working current for the motor, the power supply step-down circuit steps down the power supply provided by the AC-DC switching power supply circuit and supplies power to the control circuit, the MCU is connected to the motor working circuit, and controls the motor to work through the motor working circuit, and the standby current limiting circuit is used to limit current when the MCU is in standby. The present invention has a simplified circuit structure and occupies a small space while meeting the power requirements.

Description

Technical Field

[0001] The present invention relates to the field of low-voltage circuit breakers, and particularly to a switching power supply circuit for a miniature circuit breaker. Background Art

[0002] With the gradual advancement of the construction of smart grids, an external miniature circuit breaker for an electric energy meter is a key device for realizing the intelligent fee control function in cooperation with an intelligent electric energy meter. When a user is in an arrears state, the intelligent electric energy meter controls the external circuit breaker of the electric energy meter to trip and cut off the power. When the user renews the fee, the intelligent electric energy meter controls the external circuit breaker of the electric energy meter to close and energize. However, since the external circuit breaker connected to the electric energy meter also serves as part of the load, the power consumption thereof will also be included in the measurement of the electric energy meter. If the self-power consumption of the external circuit breaker is too large, even if there is no user load, the electric energy meter will generate charges.

[0003] The existing external circuit breaker for an electric energy meter consists of five parts: a power input circuit, a switching power supply circuit, a linear power supply circuit, a microcontroller (MCU) and its peripheral circuit, and a motor power drive circuit (see Figure 8 ). The microcontroller (MCU) realizes the safety protection control of the circuit breaker and can also be used for functions such as communication with the electric energy meter. The external circuit breaker for an electric energy meter is equipped with a drive module with a motor for remotely controlling the closing and tripping of the circuit breaker. The power input circuit directly takes power from the main circuit. One loop is connected to the switching power supply circuit to generate the motor power and the power for the drive chip, and the other loop is connected to the linear power supply circuit to generate the power required for the MCU and its peripheral circuit. Among them, a dedicated AC-DC power chip flyback switching circuit is adopted in the switching power supply circuit to achieve ultra-low power consumption. The chip integrates a high-voltage power MOSFET inside and can provide a zero standby mode. The output of the MCU is connected to the switching power supply circuit to control the working mode of the switching power supply chip. At the same time, the MCU is connected to the motor power drive circuit to control the working state of the motor. This solution requires two power supply loops: the switching power supply circuit and the linear power supply circuit. Among them, the switching power supply circuit requires a dedicated power chip, which greatly limits the selection of components, and the circuit is relatively complex. Due to the input voltage range of 60% to 120% of the rated voltage in the linear power supply circuit, the power supply fluctuation range provided to the MCU is large, which greatly affects the reliability of the MCU's operation. In the structure of a miniature circuit breaker, especially a 1P+N circuit breaker, there are strict requirements for space and volume. The existing power supply scheme cannot fully meet the requirements. Therefore, it has practical value and practical significance to design a power supply circuit with a smaller volume, a more concise circuit, and meeting the power consumption requirements for the external circuit breaker of the electric energy meter. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a switching power supply circuit for a miniature circuit breaker with a simple structure and capable of meeting the power consumption requirements.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A small circuit breaker switching power supply circuit includes an input power protection circuit, a standby current limiting circuit, an AC-DC switching power supply circuit, a motor working circuit, a power supply step-down circuit, and a control circuit including an MCU;

[0007] The input power protection circuit, the standby current limiting circuit, and the AC-DC switching power supply circuit are connected in sequence. The AC-DC switching power supply circuit is respectively connected to the motor working circuit and the power supply step-down circuit. The motor working circuit is used to drive the motor and provide working current for the motor. The power supply step-down circuit steps down the power supply provided by the AC-DC switching power supply circuit and supplies power to the control circuit. The MCU is connected to the motor working circuit and controls the motor to work through the motor working circuit. The standby current limiting circuit is used to limit the current when the MCU is in standby.

[0008] Further, the standby current limiting circuit includes a voltage protection device and at least one current limiting resistor, and the at least one current limiting resistor is connected in parallel with the voltage protection device; when the MCU is in the standby state, the input current is small, the voltage protection device is cut off so that the current flows through the current limiting resistor and is limited. When the MUC is in the working state, the input current is large, and the voltage protection device is turned on to short-circuit the current limiting resistor.

[0009] Further, the standby current limiting circuit includes a current limiting resistor R1 and a bidirectional TVS tube D6, and the bidirectional TVS tube D6 is connected in parallel with the current limiting resistor R1.

[0010] The input current of the standby current limiting circuit is I1, the current flowing through the current limiting resistor R1 is I2, and the current flowing through the bidirectional TVS tube D6 is I3, and I1 = I2 + I3;

[0011] When the MCU is in the standby state, I1 * R1 is less than the breakdown voltage of the bidirectional TVS tube D6, and the bidirectional TVS tube D6 is cut off so that the current flows through the current limiting resistor R1 and is limited;

[0012] When the MCU is in the working state, the voltage I2 * R1 is greater than the breakdown voltage of the bidirectional TVS tube D6, and the bidirectional TVS tube D6 is in the conducting state to short-circuit the current limiting resistor R1.

[0013] Further, the standby current limiting circuit is connected in series on the L-phase line between the input power protection circuit and the AC-DC switching power supply circuit.

[0014] Further, the AC-DC switching power supply circuit includes a rectification circuit, a switching power supply chip U1, a transformer T1, a clamping circuit, and a voltage dividing and feedback circuit. The switching power supply chip U1 integrates a high-voltage power MOSFET inside. The rectification circuit is connected to the standby current limiting circuit, and the rectification circuit is connected to the drain of the switching power supply chip U1 at the primary winding of the transformer T1. The clamping circuit is connected between the drain of the switching power supply chip U1 and the primary winding of the transformer T1 to absorb the spike voltage generated inside the power supply chip U1. A load circuit is connected to the secondary winding of the transformer T1, and direct current is output at the secondary winding of the transformer T1. A voltage dividing and feedback circuit is also provided on the secondary winding side of the transformer T1. The voltage dividing and feedback circuit is connected to the switching power supply chip U1 to feedback and regulate the output voltage.

[0015] Furthermore, the AC-DC switching power supply circuit includes a rectifier bridge D5, a diode D1, a diode D2, a diode D3, a diode D4, a diode D7, a transformer T1, a switching power supply chip U1, a resistor R2, a resistor R4, a capacitor C1, a capacitor C2, a polarized capacitor C3, a polarized capacitor C4, a capacitor C5, and a capacitor C6. One AC input terminal of the rectifier bridge D5 is connected to the standby current limiting circuit, and the other AC input terminal of the rectifier bridge D5 is connected to the input power protection circuit. The positive pole of the DC output terminal of the rectifier bridge D5 is connected to the anode of the diode D1, and the negative pole of the DC output terminal of the rectifier bridge D5 is connected to the negative pole of the polarized capacitor C4. The negative pole of the polarized capacitor C4 is connected to GND. The cathode of the diode D1 is connected to the positive pole of the polarized capacitor C4. The first pin of the chip U1 is connected to one end of the capacitor C6 and one end of the resistor R3. The second pin of the chip U1 is connected to one end of the resistor R2, one end of the resistor R4, and one end of the capacitor C5. The third and fourth pins of the chip U1 are connected to GND. The fifth, sixth, seventh, and eighth pins of the chip U1 are connected together and then respectively connected to the anode of the diode D4 and the second pin of the primary winding of the transformer T1. The cathode of the diode D4 is connected to the cathode of the diode D3 and one end of the capacitor C1. The first pin of the primary winding of the transformer T1, the other end of the capacitor C1, the anode of the diode D3, and the positive pole of the polarized capacitor C4 are connected to the cathode of the diode D1. The third pin of the secondary winding of the transformer T1 is connected to the anode of the diode D2. The cathode of the diode D2 is connected to the anode of the diode D7, the other end of the resistor R2, and one end of the capacitor C2. The cathode of the diode D7 is connected to the other end of the resistor R3. The positive pole of the polarized capacitor C3 is connected to the cathode of the diode D2, and the positive pole of the polarized capacitor C3 serves as the output terminal of the AC-DC switching power supply circuit. The negative pole of the polarized capacitor C3 is connected to GND. The fourth pin of the secondary winding of the transformer T1 is connected to GND. The other end of the capacitor C6, the other end of the resistor R4, the other end of the capacitor C5, and the other end of the capacitor C2 are connected to GND.

[0016] Furthermore, the input power protection circuit includes an NTC thermistor VR1, a wire-wound resistor RF1, and a varistor VR2. One end of the NTC thermistor VR1 is connected to the L-phase line. The other end of the NTC thermistor VR1 is connected to one end of the varistor VR2 and the standby current limiting circuit. One end of the wire-wound resistor RF1 is connected to the N-phase line. The other end of the wire-wound resistor RF1 is connected to the other end of the varistor VR2 and the AC-DC switching power supply circuit.

[0017] Further, the motor working circuit includes chip U2, resistor R6, resistor R7, and capacitor C7. The first pin of chip U2 is connected to the AC-DC switching power supply circuit. The second and third pins of chip U2 are respectively connected to the MCU. The second pin of chip U2 is connected to one end of resistor R6. The third pin of chip U2 is connected to one end of resistor R7. The fourth and fifth pins of chip U2, the other end of resistor R6, and the other end of resistor R7 are connected to GND. The seventh and eighth pins of chip U2 are connected to the motor for driving the motor. The eighth pin of chip U2 is connected to one end of capacitor C7, and the other end of capacitor C7 is connected to GND.

[0018] Further, the power supply bucking circuit includes chip U3, capacitor C9, capacitor C10, resistor R5, resistor R9, resistor R8, capacitor C8, inductor L2, polarized capacitor C11, polarized capacitor C12, and diode D8. The first pin of chip U3 is connected to one end of capacitor C8. The second pin of chip U3 is connected to GND. The third pin of chip U3 is respectively connected to one end of resistor R8 and one end of resistor R9. The fourth pin of chip U3 is connected to one end of resistor R5. The fifth pin of chip U3 is connected to the AC-DC switching power supply circuit, and the fifth pin of chip U3 is respectively connected to the other end of resistor R5, one end of capacitor C10, and one end of capacitor C9. The other ends of capacitor C9 and capacitor C10 are connected to GND. The sixth pin of chip U3 is connected to the other end of capacitor C8 and one end of inductor L2. The other end of inductor L2 is connected to the other end of resistor R8, the positive electrode of polarized capacitor C11, and the anode of diode D8. The cathode of diode D8 is connected to the positive electrode of polarized capacitor C12. The positive electrode of polarized capacitor C12 serves as the power supply terminal of the power supply bucking circuit. The negative electrodes of polarized capacitor C11 and polarized capacitor C12 are connected to GND.

[0019] Further, the chip U3 is an LDO chip or a DC / DC chip.

[0020] A switching power supply circuit for a miniature circuit breaker according to the present invention does not require two power supply loops. The control circuit provided with the MCU is powered from the AC-DC switching power supply circuit through the power supply bucking circuit. Compared with the prior art, there is no need to separately set up a linear loop for powering the MCU, which simplifies the circuit structure, is conducive to reducing the occupied space, and reduces power loss through the standby current limiting circuit. When the MCU is in the standby state, the motor working circuit does not drive the motor to rotate, and the standby current limiting circuit limits the current in the power supply loop to reduce the power loss in the power supply loop. When the MCU is in the working state, the motor working circuit drives the motor to rotate, and the standby current limiting circuit does not limit the current in the power supply loop to meet the power demand of the power supply loop. Description of the Drawings

[0021] Figure 1 It is a schematic diagram of a switching power supply circuit for a miniature circuit breaker according to the present invention;

[0022] Figure 2 It is a circuit diagram of a power supply module in a switching power supply circuit for a miniature circuit breaker according to the present invention;

[0023] Figure 3 It is a circuit diagram of a standby current limiting circuit in a switching power supply circuit for a miniature circuit breaker according to the present invention;

[0024] Figure 4 It is a circuit diagram of an AC-DC switching power supply circuit in a switching power supply circuit for a miniature circuit breaker according to the present invention;

[0025] Figure 5 It is a circuit diagram of an input power supply protection circuit in a switching power supply circuit for a miniature circuit breaker according to the present invention;

[0026] Figure 6 It is a circuit diagram of a motor working circuit in a switching power supply circuit for a miniature circuit breaker according to the present invention;

[0027] Figure 7 It is a circuit diagram of a power supply bucking circuit in a switching power supply circuit for a miniature circuit breaker according to the present invention;

[0028] Figure 8 It is a schematic diagram of a switching power supply circuit for a miniature circuit breaker in the background art. Specific Embodiments

[0029] The following, in combination with the embodiments given, further describes the specific embodiments of a switching power supply circuit for a miniature circuit breaker according to the present invention. The switching power supply circuit for a miniature circuit breaker according to the present invention is not limited to the description of the following embodiments. Figures 1 to 7

[0030] A switching power supply circuit for a miniature circuit breaker includes an input power supply protection circuit, a standby current limiting circuit, an AC-DC switching power supply circuit, a motor working circuit, a power supply bucking circuit, and a control circuit including an MCU;

[0031] The input power supply protection circuit, the standby current limiting circuit, and the AC-DC switching power supply circuit are connected in sequence. The AC-DC switching power supply circuit is respectively connected to the motor working circuit and the power supply bucking circuit. The motor working circuit is used to drive the motor and provide working current for the motor. The power supply bucking circuit steps down the power supply provided by the AC-DC switching power supply circuit and supplies power to the control circuit. The MCU is connected to the motor working circuit and controls the motor to work through the motor working circuit. The standby current limiting circuit is used to limit current when the MCU is in standby;

[0032] ​When the MCU is in the standby state, the motor working circuit does not drive the motor to rotate, the input current is small, and the standby current limiting circuit limits the current of the power supply loop; when the MCU is in the working state, the motor working circuit drives the motor to rotate, and the standby current limiting circuit does not limit the current of the power supply loop and has no current limiting effect.

[0033] A switching power supply circuit for a miniature circuit breaker of the present invention does not need to set two power supply loops. The control circuit provided with the MCU is powered by the AC-DC switching power supply circuit through the power supply step-down circuit. Compared with the prior art, it does not need to separately set a linear loop for powering the MCU, simplifies the circuit structure, is beneficial to reducing the occupied space, and reduces power loss through the standby current limiting circuit. When the MCU is in the standby state, the motor working circuit does not drive the motor to rotate, and the standby current limiting circuit limits the current in the power supply loop to reduce the power loss in the power supply loop; when the MCU is in the working state, the motor working circuit drives the motor to rotate, and the standby current limiting circuit does not limit the current in the power supply loop to meet the power demand of the power supply loop.

[0034] Combined with the attached Figures 1 - 7 Detailed introduction, a switching power supply circuit for a miniature circuit breaker, includes an input power protection circuit, a standby current limiting circuit, an AC-DC switching power supply circuit, a motor working circuit, a power supply step-down circuit and an MCU; the input power protection circuit, the standby current limiting circuit, and the AC-DC switching power supply circuit are sequentially connected to form a power supply module that supplies power to the motor working circuit and the power supply step-down circuit respectively. The input power protection circuit is connected to the main circuit for providing power protection, such as including but not limited to suppressing inrush current and transient voltage. The AC-DC switching power supply circuit is respectively connected to the motor working circuit and the power supply step-down circuit. The motor working circuit is used to drive the motor and provide working current for the motor. The power supply step-down circuit is used as an output terminal to supply power outward. The power supply step-down circuit is connected to the control circuit and steps down the power provided by the AC-DC switching power supply circuit to supply power to the control circuit; the control circuit includes an MCU and an MCU peripheral circuit. The MCU is connected to the motor working circuit and controls the motor operation through the motor working circuit. The input power protection circuit, the standby current limiting circuit, the AC-DC switching power supply circuit, the motor working circuit, and the power supply step-down circuit form a power supply loop for supplying power to the control circuit and the motor.

[0035] The standby current limiting circuit is used to limit the current to reduce power consumption when the MCU is in standby. When the MCU is in the standby state, the motor working circuit does not drive the motor to rotate. At this time, the circuit load in the power supply loop is small, the input current of the standby current limiting circuit is small, and the standby current limiting circuit further limits the current of the power supply loop;

[0036] When the MCU is in the working state, the motor working circuit drives the motor to rotate. The circuit load in the power supply loop is large, and the input current of the standby current limiting circuit is relatively large. The standby current limiting circuit has no current limiting effect on the current in the power supply loop, which is used to meet the demand for the increase in current power consumption caused by load changes.

[0037] The standby current limiting circuit includes a voltage protection device and at least one current limiting resistor. The at least one current limiting resistor is connected in parallel with the voltage protection device. The standby current limiting circuit is connected in series on the L-phase line or N-phase line between the input power supply protection circuit and the AC-DC switching power supply circuit. When the MCU is in the standby state, the input current of the standby current limiting circuit is small, and the voltage protection device is cut off, so that the current in the power supply loop flows through the current limiting resistor and is limited. When the MUC is in the working state, the input current of the standby current limiting circuit is large, and the voltage protection device conducts to short-circuit the current limiting resistor, so that the current in the power supply loop does not flow through the current limiting resistor and is not limited. As Figure 2 、 3 shown in the embodiment, the voltage protection device is a bidirectional TVS tube.

[0038] As Figure 2 、 5 shown, the input power supply protection circuit includes an NTC thermistor VR1, a wire-wound resistor RF1 and a varistor VR2. One end of the NTC thermistor VR1 is connected to the L-phase line. The other end of the NTC thermistor VR1 is connected to one end of the varistor VR2 and the standby current limiting circuit. One end of the wire-wound resistor RF1 is connected to the N-phase line. The other end of the wire-wound resistor RF1 is connected to the other end of the varistor VR2 and the AC-DC switching power supply circuit. The NTC thermistor VR1 is used to suppress the inrush current at startup. The function of the wire-wound resistor RF1 is that when the current in the power supply loop is too large or a short-circuit fault occurs, when the current flowing through the wire-wound resistor RF1 exceeds the limit, it will be burned out, so that the wire-wound resistor RF1 is in an open state, which is used to disconnect the input power supply loop. Of course, the wire-wound resistor RF1 can also be a fuse. The varistor VR2 is used to suppress the transient overvoltage in the power supply loop.

[0039] As Figure 2 、 3 shown, in a preferred embodiment of the standby current limiting circuit, the voltage protection device is a bidirectional TVS tube. The standby current limiting circuit includes a current limiting resistor R1 and a bidirectional TVS tube D6. Preferably, as Figure 2 、 3As shown, the two ends after the parallel connection of the bidirectional TVS tube D6 and the current-limiting resistor R1 are connected in series on the L-phase line between the input power protection circuit and the AC-DC switching power supply circuit. Specifically, one end after the parallel connection of the bidirectional TVS tube D6 and the current-limiting resistor R1 is connected to the node of the NTC thermistor VR1 and the varistor VR2 of the input power protection circuit. In the figure, the input current of the standby current-limiting circuit is I1, the current flowing through the current-limiting resistor R1 is I2, and the current flowing through the bidirectional TVS tube D6 is I3. When the MCU is in the standby state, the motor does not work, the circuit load of the power supply loop is small, and the input current is small, that is, the current I1 flowing through the NTC thermistor VR1 from the main circuit L-line is small. Most of the current passes through the current-limiting resistor R1. Since I1 = I2 + I3, the voltage across the resistor R1 is less than I1 * R1. Also, because I1 * R1 is less than the breakdown voltage of the bidirectional TVS tube D6, the bidirectional TVS tube D6 is in the cut-off state, and its impedance is much larger than R1, affecting the power factor of the power supply loop. The current of the power supply loop flowing through the current-limiting resistor R1 is further current-limited; when the MCU is in the working state, the motor is in the running state, the circuit load of the power supply loop is large, and the input current is large, that is, the current I1 flowing through the NTC thermistor VR1 from the main circuit L-line is large. The voltage I2 * R1 across the resistor R1 is greater than the breakdown voltage of the bidirectional TVS tube D6, and the bidirectional TVS tube D6 is in the conducting state, that is, the two ends of the resistor R1 are in a short-circuit state. The current of the power supply loop is not current-limited by the current-limiting resistor R1, meeting the requirement of the increased current power consumption caused by the load change.

[0040] An embodiment of the AC-DC switching power supply circuit is that the AC-DC switching power supply circuit includes a rectifier circuit and a transformer T1, which is used to convert alternating current into direct current and step down the voltage.

[0041] As Figure 2 , 4 In a preferred embodiment as shown, the AC-DC switching power supply circuit includes a rectifier circuit, a switching power supply chip U1, a transformer T1, a clamping circuit, and a voltage dividing feedback circuit. The model of the switching power supply chip U1 is MP173, and a high-voltage power MOSFET is integrated inside the chip. The rectifier circuit is connected to the standby current-limiting circuit. The rectifier circuit and the drain of the MOSFET inside the switching power supply chip U1 are connected to the primary winding of the transformer T1. The clamping circuit is connected between the drain of the switching power supply chip U1 and the primary winding of the transformer T1 to absorb the spike voltage generated inside the power supply chip U1. Direct current is output from the secondary winding of the transformer T1 for connecting the load. The load includes the MCU, the motor, and external circuits, etc. A voltage dividing feedback circuit is also provided on the secondary winding side of the transformer T1, and the voltage dividing feedback circuit is connected to the switching power supply chip U1 for feedback adjustment of the output voltage.

[0042] Specifically asFigure 2 , 4 As shown, the AC-DC switching power supply circuit includes a rectifier bridge D5, a diode D1, a diode D2, a diode D3, a diode D4, a diode D7, a transformer T1, a switching power supply chip U1, a resistor R2, a resistor R4, a capacitor C1, a capacitor C2, a polarized capacitor C3, a polarized capacitor C4, a capacitor C5, and a capacitor C6. The rectifier circuit includes the rectifier bridge D5. The voltage division feedback circuit includes the resistor R2, the resistor R4, and the capacitor C5. The clamping circuit includes the diode D3, the capacitor C1, and the diode D4. The rectifier circuit is preferably formed by connecting multiple diodes to form the rectifier bridge D5. One AC input terminal of the rectifier bridge D5 is connected to the standby current limiting circuit, and the other AC input terminal of the rectifier bridge D5 is connected to the input power protection circuit. The positive pole of the DC output terminal of the rectifier bridge D5 is connected to the anode of the diode D1, and the negative pole of the DC output terminal of the rectifier bridge D5 is connected to the negative pole of the polarized capacitor C4. The negative pole of the polarized capacitor C4 is connected to GND, and the negative pole of the polarized capacitor C4 serves as the reference ground of the entire circuit; the cathode of the diode D1 is connected to the positive pole of the polarized capacitor C4; the first pin of the chip U1 is connected to one end of the capacitor C6 and one end of the resistor R3. The second pin of the chip U1 is connected to one end of the resistor R2, one end of the resistor R4, and one end of the capacitor C5. The third and fourth pins of the chip U1 are connected to GND. After the fifth, sixth, seventh, and eighth pins of the chip U1 are connected together, they are respectively connected to the anode of the diode D4 and the second pin of the primary winding of the transformer T1. The cathode of the diode D4 is connected to the cathode of the diode D3 and one end of the capacitor C1. The first pin of the primary winding of the transformer T1, the other end of the capacitor C1, the anode of the diode D3, and the positive pole of the polarized capacitor C4 are connected to the cathode of the diode D1; the third pin of the secondary winding of the transformer T1 is connected to the anode of the diode D2. The cathode of the diode D2 is connected to the anode of the diode D7, the other end of the resistor R2, and one end of the capacitor C2. The cathode of the diode D7 is connected to the other end of the resistor R3. The polarized capacitor C3 is connected to the secondary winding of the transformer T1. The polarized capacitor C3 serves as an energy storage device to provide energy for the load. The positive pole of the polarized capacitor C3 is connected to the cathode of the diode D2, and the positive pole of the polarized capacitor C3 serves as the output terminal of the AC-DC switching power supply circuit. The negative pole of the polarized capacitor C3 is connected to GND; the fourth pin of the secondary winding of the transformer T1 is connected to GND. The other end of the capacitor C6, the other end of the resistor R4, the other end of the capacitor C5, and the other end of the capacitor C2 are connected to GND.

[0043] As Figure 6As shown, the motor working circuit includes chip U2, resistor R6, resistor R7, and capacitor C7. The first pin of chip U2 is connected to the AC-DC switching power supply circuit, specifically to the positive electrode of the polar capacitor C3 in the AC-DC switching power supply circuit. Chip U2 draws power from the positive electrode of the polar capacitor C3. The second and third pins of chip U2 are respectively connected to the MCU. The second pin of chip U2 is connected to one end of resistor R6, and the third pin of chip U2 is connected to one end of resistor R7. The fourth and fifth pins of chip U2, the other end of resistor R6, and the other end of resistor R7 are connected to GND. The seventh and eighth pins of chip U2 are connected to the motor for driving the motor. Preferably, the motor is connected to chip U2 through the motor interface J1. The eighth pin of chip U2 is connected to one end of capacitor C7, and the other end of capacitor C7 is connected to GND.

[0044] As Figure 7 shown, the power supply bucking circuit includes chip U3, capacitor C9, capacitor C10, resistor R5, resistor R9, resistor R8, capacitor C8, inductor L2, polar capacitor C11, polar capacitor C12, and diode D8. Chip U3 is used for bucking. The first pin of chip U3 is connected to one end of capacitor C8. The second pin of chip U3 is connected to GND. The third pin of chip U3 is respectively connected to one end of resistor R8 and one end of resistor R9. The fourth pin of chip U3 is connected to one end of resistor R5. The fifth pin of chip U3 is connected to the AC-DC switching power supply circuit, specifically to the positive electrode of the polar capacitor C3 in the AC-DC switching power supply circuit. Chip U3 draws power from the positive electrode of the polar capacitor C3. And the fifth pin of chip U3 is respectively connected to the other end of resistor R5, one end of capacitor C10, and one end of capacitor C9. The other ends of capacitor C9 and capacitor C10 are connected to GND. The sixth pin of chip U3 is connected to the other end of capacitor C8 and one end of inductor L2. The other end of inductor L2 is connected to the other end of resistor R8, the positive electrode of polar capacitor C11, and the anode of diode D8. The cathode of diode D8 is connected to the positive electrode of polar capacitor C12. The positive electrode of polar capacitor C12 serves as the power supply terminal of the power supply bucking circuit. The negative electrodes of polar capacitor C11 and polar capacitor C12 are connected to GND. Preferably, chip U3 is an LDO chip or a DC / DC chip.

[0045] In this application, the model of chip U1 is MP173, the model of chip U2 is HT7126A, and the model of chip U3 is LA1631.

[0046] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A switching power supply circuit for a miniature circuit breaker, characterized in that: It includes an input power protection circuit, a standby current limiting circuit, an AC-DC switching power supply circuit, a motor working circuit, a power supply step-down circuit and a control circuit including an MCU; The input power protection circuit, the standby current limiting circuit and the AC-DC switching power supply circuit are connected in sequence. The AC-DC switching power supply circuit is respectively connected to the motor working circuit and the power supply step-down circuit. The motor working circuit is used to drive the motor and provide working current for the motor. The power supply step-down circuit steps down the power supply provided by the AC-DC switching power supply circuit and supplies power to the control circuit. The MCU is connected to the motor working circuit and controls the motor operation through the motor working circuit. The standby current limiting circuit is used to limit current when the MCU is in standby; The standby current limiting circuit includes a current limiting resistor R1 and a bidirectional TVS tube D6. The bidirectional TVS tube D6 and the current limiting resistor R1 are in parallel; The input current of the standby current limiting circuit is I1, the current flowing through the current limiting resistor R1 is I2, and the current flowing through the bidirectional TVS tube D6 is I3. I1 = I2 + I3; When the MCU is in the standby state, I1*R1 is less than the breakdown voltage of the bidirectional TVS tube D6, and the bidirectional TVS tube D6 is cut off so that the current flows through the current limiting resistor R1 and is current-limited; When the MCU is in the working state, the voltage I2*R1 is greater than the breakdown voltage of the bidirectional TVS tube D6, and the bidirectional TVS tube D6 is in the conducting state so that the current limiting resistor R1 is short-circuited; The standby current limiting circuit is connected in series on the L-phase line between the input power protection circuit and the AC-DC switching power supply circuit.

2. The switching power supply circuit for a miniature circuit breaker according to claim 1, characterized in that: The AC-DC switching power supply circuit includes a rectifying circuit, a switching power supply chip U1, a transformer T1, a clamping circuit and a voltage dividing feedback circuit. The switching power supply chip U1 internally integrates a high-voltage power MOSFET. The rectifying circuit is connected to the standby current limiting circuit. The rectifying circuit and the drain of the switching power supply chip U1 are connected to the primary winding of the transformer T1. The clamping circuit is connected between the drain of the switching power supply chip U1 and the primary winding of the transformer T1 to absorb the spike voltage generated inside the power supply chip U1. A load circuit is connected to the secondary winding of the transformer T1. DC power is output from the secondary winding of the transformer T1. A voltage dividing feedback circuit is also provided on the secondary winding side of the transformer T1. The voltage dividing feedback circuit is connected to the switching power supply chip U1 for feedback adjustment of the output voltage.

3. The switching power supply circuit for a miniature circuit breaker according to claim 1 or 2, characterized in that: The AC-DC switching power supply circuit includes a rectifier bridge D5, diodes D1, D2, D3, D4, D7, a transformer T1, a switching power supply chip U1, resistors R2, R4, capacitors C1, C2, polarized capacitors C3, C4, C5 and C6. One AC input terminal of the rectifier bridge D5 is connected to the standby current limiting circuit, and the other AC input terminal of the rectifier bridge D5 is connected to the input power protection circuit. The positive pole of the DC output terminal of the rectifier bridge D5 is connected to the anode of the diode D1, and the negative pole of the DC output terminal of the rectifier bridge D5 is connected to the negative pole of the polarized capacitor C4. The negative pole of the polarized capacitor C4 is connected to GND; the cathode of the diode D1 is connected to the positive pole of the polarized capacitor C4; the first pin of the chip U1 is connected to one end of the capacitor C6 and one end of the resistor R3. The second pin of the chip U1 is connected to one end of the resistor R2, one end of the resistor R4 and one end of the capacitor C5. The third and fourth pins of the chip U1 are connected to GND. The fifth, sixth, seventh and eighth pins of the chip U1 are connected together and then respectively connected to the anode of the diode D4 and the second pin of the primary winding of the transformer T1. The cathode of the diode D4 is connected to the cathode of the diode D3 and one end of the capacitor C1. The first pin of the primary winding of the transformer T1, the other end of the capacitor C1, the anode of the diode D3 and the positive pole of the polarized capacitor C4 are connected to the cathode of the diode D1; the third pin of the secondary winding of the transformer T1 is connected to the anode of the diode D2. The cathode of the diode D2 is connected to the anode of the diode D7, the other end of the resistor R2 and one end of the capacitor C2. The cathode of the diode D7 is connected to the other end of the resistor R3. The positive pole of the polarized capacitor C3 is connected to the cathode of the diode D2, and the positive pole of the polarized capacitor C3 serves as the output terminal of the AC-DC switching power supply circuit. The negative pole of the polarized capacitor C3 is connected to GND; the fourth pin of the secondary winding of the transformer T1 is connected to GND. The other end of the capacitor C6, the other end of the resistor R4, the other end of the capacitor C5 and the other end of the capacitor C2 are connected to GND.

4. The switching power supply circuit for a miniature circuit breaker according to claim 1, characterized in that: The input power protection circuit includes an NTC thermistor VR1, a wire-wound resistor RF1 and a varistor VR2. One end of the NTC thermistor VR1 is connected to the L-phase line. The other end of the NTC thermistor VR1 is connected to one end of the varistor VR2 and the standby current limiting circuit. One end of the wire-wound resistor RF1 is connected to the N-phase line. The other end of the wire-wound resistor RF1 is connected to the other end of the varistor VR2 and the AC-DC switching power supply circuit.

5. The switching power supply circuit for a miniature circuit breaker according to claim 1, characterized in that: The motor working circuit includes chip U2, resistor R6, resistor R7, and capacitor C7. The first pin of chip U2 is connected to the AC-DC switching power supply circuit. The second and third pins of chip U2 are respectively connected to the MCU. The second pin of chip U2 is connected to one end of resistor R6. The third pin of chip U2 is connected to one end of resistor R7. The fourth and fifth pins of chip U2, the other end of resistor R6, and the other end of resistor R7 are connected to GND. The seventh and eighth pins of chip U2 are connected to the motor for driving the motor. The eighth pin of chip U2 is connected to one end of capacitor C7, and the other end of capacitor C7 is connected to GND.

6. The switching power supply circuit for a miniature circuit breaker according to claim 1, characterized in that: The power supply bucking circuit includes chip U3, capacitor C9, capacitor C10, resistor R5, resistor R9, resistor R8, capacitor C8, inductor L2, polarized capacitor C11, polarized capacitor C12, and diode D8. The first pin of chip U3 is connected to one end of capacitor C8. The second pin of chip U3 is connected to GND. The third pin of chip U3 is respectively connected to one end of resistor R8 and one end of resistor R9. The fourth pin of chip U3 is connected to one end of resistor R5. The fifth pin of chip U3 is connected to the AC-DC switching power supply circuit, and the fifth pin of chip U3 is respectively connected to the other end of resistor R5, one end of capacitor C10, and one end of capacitor C9. The other end of capacitor C9 and the other end of capacitor C10 are connected to GND. The sixth pin of chip U3 is connected to the other end of capacitor C8 and one end of inductor L2. The other end of inductor L2 is connected to the other end of resistor R8, the positive electrode of polarized capacitor C11, and the anode of diode D8. The cathode of diode D8 is connected to the positive electrode of polarized capacitor C12. The positive electrode of polarized capacitor C12 serves as the power supply terminal of the power supply bucking circuit. The negative electrode of polarized capacitor C11 and the negative electrode of polarized capacitor C12 are connected to GND.

7. The switching power supply circuit for a miniature circuit breaker according to claim 6, characterized in that: The chip U3 is an LDO chip or a DC / DC chip.

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