CN108512192B

CN108512192B - Electronic control circuit for undervoltage release

Info

Publication number: CN108512192B
Application number: CN201710118847.3A
Authority: CN
Inventors: 吴海良; 王军; 周婷婷; 周英姿
Original assignee: Zhejiang Chint Electrics Co Ltd; SEARI Electric Technology Co Ltd
Current assignee: Zhejiang Chint Electrics Co Ltd; SEARI Electric Technology Co Ltd
Priority date: 2017-02-28
Filing date: 2017-02-28
Publication date: 2020-11-03
Anticipated expiration: 2037-02-28
Also published as: CN108512192A

Abstract

The invention discloses an electronic control circuit for an undervoltage release, wherein the input end of an EMC circuit is connected with the input end of an external power supply, the output end of the EMC circuit is connected with the input end of a rectifying circuit, the rectifying circuit rectifies the external power supply into direct current, and the output end of the rectifying circuit is respectively connected with a power supply electricity taking and maintaining coil control circuit, a signal sampling circuit, a starting coil and a driving circuit; the output end of the signal sampling circuit is connected with the input end of the power supply electricity taking and maintaining coil control circuit and the input end of the MCU circuit, and the output end of the power supply electricity taking and maintaining coil control circuit is connected with the input ends of the starting coil and the driving circuit; the input end of the power supply conversion circuit is connected with the output end of the power supply electricity taking and maintaining coil control circuit, the output end of the power supply conversion circuit is connected with the input end of the MCU circuit, and the output end of the MCU circuit is connected with the starting coil and the driving circuit and the power supply electricity taking and maintaining coil control circuit.

Description

Electronic control circuit for undervoltage release

Technical Field

The invention relates to the field of low-voltage electrical appliances, in particular to an electronic control circuit for an undervoltage release.

Background

In the existing undervoltage release, when the voltage at the power supply voltage drops (or slowly drops) to the range of 70% to 35% of the rated working voltage of the undervoltage release, the undervoltage release should act to open the circuit breaker. When the voltage at the voltage of the power supply voltage is lower than 35% of the rated working voltage of the release, the under-voltage release should prevent the circuit breaker from being closed, and when the voltage at the voltage of the power supply voltage is equal to or more than 85% of the rated working voltage of the release, the circuit breaker should be ensured to be closed. The undervoltage release is one of the important accessories of the frame circuit breaker, belongs to the accessories for long-term operation, and is required to be capable of long-term stable operation at 110% of rated voltage.

The development of the low-voltage circuit breaker matched with the current undervoltage release is also characterized in that:

first, there is a trend toward more and more miniaturization. The under-voltage release is also required to be miniaturized, and the miniaturized under-voltage release is usually designed to mainly solve the problem of temperature rise control during long-term operation. An electronic control circuit is required to well control the current flowing through the coil, so that the electronic control circuit can keep certain heat balance in a narrow space; in addition, the space in the miniaturized undervoltage release is limited, and the volume of the electronic control circuit board is required to be small enough;

second, the circuit breaker target is getting higher and higher. For example, a higher short-tolerance index requires a larger tripping force (more than 15N) of the circuit breaker to overcome a larger electric repulsive force, which inevitably requires a larger spring force in the under-voltage release and a larger holding power of the electromagnet, and further requires that the temperature rise of the under-voltage release is controlled within a certain range (50K) when the under-voltage release works stably for a long time at 110% of the rated voltage, and meanwhile, the electromagnetic force is enough to overcome the spring force, so that the release is reliably attracted;

thirdly, low voltage circuit breakers have multiple voltage specifications and a wide range span (from AC24V to AC 440V). Especially, the AC440V specification, the small size of the whole undervoltage release product, the high reliability requirement have raised the difficulty for the design of circuits such as power supply electricity getting.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the electronic control circuit for the undervoltage release, which has the advantages of simple and compact structure, safe and stable performance and low cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

an electronic control circuit for an undervoltage release is characterized in that: the power supply comprises an EMC circuit, a rectifying circuit, a signal sampling circuit, a power supply electricity taking and maintaining coil control circuit, a power supply conversion circuit, a starting coil and driving circuit and an MCU circuit; the input end of the EMC circuit is connected with the input end of an external power supply, the output end of the EMC circuit is connected with the input end of the rectifying circuit, the rectifying circuit rectifies the external power supply into direct current, and the output end of the rectifying circuit is respectively connected with the power supply electricity taking and maintaining coil control circuit, the signal sampling circuit, the starting coil and the driving circuit; the output end of the signal sampling circuit is connected with the input end of the power supply electricity taking and maintaining coil control circuit and the input end of the MCU circuit, and the output end of the power supply electricity taking and maintaining coil control circuit is connected with the input ends of the starting coil and the driving circuit; the input end of the power supply conversion circuit is connected with the output end of the power supply electricity taking and maintaining coil control circuit, the output end of the power supply conversion circuit is connected with the input end of the MCU circuit, and the output end of the MCU circuit is connected with the starting coil and the driving circuit and the power supply electricity taking and maintaining coil control circuit.

Further, the power supply electricity taking and maintaining coil control circuit comprises a logic and driving circuit, a maintaining coil T1A, an MOS tube Q3 and a power supply circuit; one end of a maintaining coil T1A is connected with the output end of the rectifying circuit, the other end of the maintaining coil T1A is connected with an MOS transistor Q3, the other end of the maintaining coil T1A is simultaneously connected with the input end of a power circuit, and the output end of the power circuit is connected with the input end of a starting coil and a driving circuit and the input end of a power conversion circuit; the input end of the logic and drive circuit is connected with the output end of the MCU circuit, and the output end of the logic and drive circuit is connected with the MOS tube Q3.

Further, the logic and driving circuit comprises a logic chip U3 and a resistor R10; one end of a resistor R10 is connected with the gate of a MOS tube Q3, the other end of a resistor R10 is connected with a tenth pin of a logic chip U3, an eighth pin and a ninth pin of the logic chip U3 are connected with a third pin of a logic chip U3, a first pin of the logic chip U3 is connected with the drain of the MOS tube Q1, the drain of the MOS tube Q1 is connected with a power supply VDD through a resistor R8, the gate of the MOS tube Q1 is connected with the output end of the MCU circuit, the source of the MOS tube Q1 is grounded, and two ends of the resistor R12 are connected between the gate of the MOS tube Q1 and the source of the MOS tube Q1 in parallel; the second pin of the logic chip U3 is connected with the fourth pin of the logic chip U3, the capacitor C5 is connected in series with the resistor R16, one end of the capacitor C5 is connected with the fourth pin of the logic chip U3 after the series connection, one end of the resistor R16 is connected with the twelfth pin of the logic chip U3 and the thirteenth pin of the logic chip U3, one end of the resistor R15 is connected with the middle node of the capacitor C5 and the resistor R16, the other end is connected with the sixth pin of the logic chip U3 and the eleventh pin of the logic chip U3, the fifth pin of the logic chip U3 is connected to the drain of the MOS tube Q2, the drain of the MOS tube Q2 is connected to the power supply VDD through the resistor R9, the source of the MOS tube Q2 is grounded, the resistor R13 is connected in parallel between the gate of the MOS tube Q2 and the source of the MOS tube Q2, and the gate of the MOS tube Q2 is connected with the output.

Further, the power supply circuit comprises a resistor R5, a resistor R6, a resistor R4, a resistor R7, a capacitor C7, a voltage regulator tube D4, a diode D3 and a polarity capacitor C1; the cathode of the diode D3 is connected with the input end of the power conversion circuit and the input end of the start coil and the drive circuit, the anode of the polar capacitor C1 is connected with the cathode of the diode D3, the cathode of the polar capacitor C1 is connected with the cathode of the diode D3, the anode of the diode D3 is connected to one end of the holding coil T1A through the capacitor C4, and two ends of the resistor R5, the resistor R6, the resistor R4 and the resistor R7 which are connected in series are connected in parallel to two ends of the capacitor C4; the circuit also comprises a diode D2 and a resistor R14, two ends of the diode D2 are connected in parallel with two ends of the holding coil T1A, two ends of the resistor R14 are connected in parallel between the grid of the MOS tube Q3 and the source of the MOS tube Q3, the source of the MOS tube Q3 is grounded, the grid of the MOS tube Q3 is connected with the output end of the logic and driving circuit, and the other end of the holding coil T1A is connected with the output end of the signal sampling circuit.

Further, the starting coil and driving circuit comprises a starting coil T1B, a MOS transistor Q4 and a driving circuit; one end of the starting coil T1B is connected with the output end of the rectifying circuit, the other end of the starting coil T1B is connected with one end of the MOS tube Q4, the other end of the MOS tube Q4 is connected with the output end of the driving circuit, and the input end of the driving circuit is connected with the output end of the power supply electricity taking and maintaining coil control circuit and the output end of the MCU circuit.

Further, the driving circuit comprises a driving chip U5, a resistor R24, a resistor R22, a resistor R25 and a capacitor C10; the drain of the MOS transistor Q4 is connected with the other end of the starting coil T1B, the resistor R24 is connected in parallel with the gate of the MOS transistor Q4 and the source of the MOS transistor Q4, the source of the MOS transistor Q4 is grounded, one end of the resistor R22 is connected with the gate of the MOS transistor Q4, the other end of the resistor R22 is connected with the fifth pin of the driving chip U5, the fourth pin of the driving chip U5 is grounded, the first pin of the driving chip U5 is grounded, the second pin of the driving chip U5 is grounded through the capacitor C10, and the second pin of the driving chip U5 is grounded through the resistor R25.

Further, the EMC circuit comprises a voltage dependent resistor RV1, a resistor R1, a resistor R3 and a capacitor C2, an external power supply is divided into two paths and connected to the input end of the rectifying circuit through the resistor R1 and the resistor R3, the voltage dependent resistor RV1 is connected to the front ends of the resistor R1 and the resistor R3 in parallel, and the capacitor C2 is connected to the rear end of the resistor R1 and the rear end of the resistor R3 in parallel. The rectifying circuit comprises a rectifying bridge B1, the input end of the rectifying bridge B1 is connected with the output end of the EMC circuit, and the output end of the rectifying bridge B1 is connected with the power supply electricity taking and maintaining coil control circuit, the signal sampling circuit and the starting coil and the driving circuit.

Further, the signal sampling circuit comprises a diode D5, a resistor R17, a resistor R21, a resistor R23, a resistor R30, a capacitor C11, a resistor R26 and a diode D7; the anode of the diode D5 is connected with the output end of the rectifying circuit, the cathode of the diode D5 is connected with the power supply power taking and maintaining coil control circuit, the resistor R17, the resistor R21, the resistor R23 and the resistor R30 are connected in series, the other end of the resistor R17 is connected with the anode of the diode D5, the other end of the resistor R30 is grounded, one end of the resistor R26 is connected with the middle node of the resistor R23 and the resistor R30, the other end of the resistor R26 is connected with the input end of the power supply power taking and MCU circuit, the anode of the diode D7 is connected with the other end of the resistor R26, and the cathode of the diode D7 is connected with the power.

Further, the power conversion circuit comprises a power conversion chip U4, a polar capacitor C9, a resistor R11, a polar capacitor C6 and a capacitor C7; the input end of a power conversion chip U4 is connected with the output end of a power circuit, the positive electrode of a polarity capacitor C9 is connected with the input end of a power conversion chip U4, the negative electrode of a polarity capacitor C9 is grounded, the output end of the power conversion chip U4 is connected with one end of a resistor R11, the other end of the resistor R11 is connected with one end of a polarity capacitor C6 and one end of a capacitor C7 which are connected in parallel, one end of the polarity capacitor C6 and one end of the capacitor C7 which are connected in parallel are simultaneously connected with an MCU circuit, and the other end of the polarity capacitor C6 and the other end of the capacitor C36.

Further, the MCU circuit is a programmable logic device or a DSP chip or a singlechip.

The electronic control circuit for the undervoltage release has the advantages of simple and compact integral structure and low cost; the EMC circuit is used for protecting the control circuit from impact interference such as external surge and the like and reducing the external radiation level of the product; the signal sampling circuit realizes the partial pressure sampling of input voltage and the amplitude limiting processing of a sampling signal; the power supply conversion circuit converts the larger voltage (8.2V) of the front stage into VCC (about 3.3V) which can be matched with the singlechip for use; the MCU circuit is used for digitizing an effective value of the output voltage value S1 of the sampling circuit into a voltage value through an ADC (analog-to-digital conversion), judging a logic value through a voltage threshold value, realizing accurate sampling of voltage, ensuring the accuracy of a voltage action value and realizing accurate under-voltage protection of a power grid, and is used for generating adjustable PWM waves in a product pull-in maintaining stage, so that a maintaining coil is reliably pulled in through a switch tube control circuit, a power supply circuit keeps certain output capacity and the whole control panel is maintained to work; in addition, the double coils are designed in a matched manner, the starting coil and the maintaining coil are combined to act, the realization of an under-voltage function is ensured, only the maintaining coil works when the device works for a long time, the impact of working current, external conduction interference and the like is greatly reduced, and the EMC (electro magnetic compatibility) characteristic of the whole product is improved; particularly, the power supply of the power supply conversion circuit, the MCU circuit, the starting coil and the driving circuit is provided by the power supply electricity taking and maintaining coil control circuit, so that the heat power consumption of components on an electronic circuit control board is at a lower level, and the long-term stable work of the under-voltage release can be ensured when the under-voltage release is 110 percent of the rated voltage. The maintenance coil is connected with the switch MOS tube in series and connected with the power circuit in series to take electricity for external high-voltage input, the operation mode solves the electricity taking problem of a microcontroller and related circuits of the control panel, and the electricity taking mode applies voltage drop to the maintenance coil so that the heat power consumption of components on the electronic circuit control panel is in a lower level; the tripping device is provided with larger starting torque, and meanwhile, the under-voltage tripping device can be ensured to stably work for a long time when the rated voltage is 110 percent.

Drawings

Fig. 1 is a schematic diagram of the overall structure of an electronic control circuit for an undervoltage release according to the present invention;

FIG. 2 is a circuit diagram of the logic and driver circuit of the present invention;

FIG. 3 is a circuit diagram of the connection relationship between the sustaining coil, the power circuit and the MOS transistor according to the present invention;

FIG. 4 is a circuit diagram of the power conversion circuit of the present invention;

FIG. 5 is a circuit diagram of the start coil and drive circuit of the present invention;

FIG. 6 is a circuit diagram of an EMC circuit and a rectifier circuit of the present invention;

fig. 7 is a circuit diagram of the signal utilization circuit of the present invention.

Detailed Description

The following describes a specific embodiment of the electronic control circuit for the undervoltage trip device according to the present invention with reference to the embodiments shown in fig. 1 to 7. The electronic control circuit for the undervoltage trip of the present invention is not limited to the description of the following embodiments.

As shown in fig. 1, the electronic control circuit for the undervoltage release of the present invention comprises an EMC circuit, a rectifying circuit, a signal sampling circuit, a power supply power taking and maintaining coil control circuit, a power supply conversion circuit, a start coil and driving circuit, and an MCU circuit; the input end of the EMC circuit is connected with the input end of an external power supply, the output end of the EMC circuit is connected with the input end of the rectifying circuit, the rectifying circuit rectifies the external power supply into direct current, and the output end of the rectifying circuit is respectively connected with the power supply electricity taking and maintaining coil control circuit, the signal sampling circuit, the starting coil and the driving circuit; the output end of the signal sampling circuit is connected with the input end of the power supply electricity taking and maintaining coil control circuit and the input end of the MCU circuit, and the output end of the power supply electricity taking and maintaining coil control circuit is connected with the input ends of the starting coil and the driving circuit; the input end of the power supply conversion circuit is connected with the output end of the power supply electricity taking and maintaining coil control circuit, the output end of the power supply conversion circuit is connected with the input end of the MCU circuit, and the output end of the MCU circuit is connected with the starting coil and the driving circuit. The electronic control circuit for the undervoltage release has the advantages of simple and compact integral structure and low cost; the EMC circuit is used for protecting the control circuit from impact interference such as external surge and the like and reducing the external radiation level of the product; the signal sampling circuit realizes the partial pressure sampling of input voltage and the amplitude limiting processing of a sampling signal; the power supply conversion circuit converts the larger voltage (8.2V) of the front stage into VCC3.3V (about 3.3V) which can be matched with the singlechip for use; the MCU circuit is used for digitizing an effective value of the output voltage value S1 of the sampling circuit into a voltage value through an ADC (analog-to-digital conversion), judging a logic value through a voltage threshold value, realizing accurate sampling of voltage, ensuring the accuracy of a voltage action value and realizing accurate under-voltage protection of a power grid, and is used for generating adjustable PWM waves in a product pull-in maintaining stage, so that a maintaining coil is reliably pulled in through a switch tube control circuit, a power supply circuit keeps certain output capacity and the whole control panel is maintained to work; in addition, the double coils are designed in a matched manner, the starting coil and the maintaining coil are combined to act, the realization of an under-voltage function is ensured, only the maintaining coil works when the device works for a long time, the impact of working current, external conduction interference and the like is greatly reduced, and the EMC (electro magnetic compatibility) characteristic of the whole product is improved; particularly, the power supplies of the power supply conversion circuit, the MCU circuit, the start coil and the drive circuit are provided by the power supply and maintaining coil control circuit, so that the heat power consumption of components on an electronic circuit control board is at a lower level, the long-term stable work of the under-voltage release at the rated voltage of 110 percent is ensured, and the power supplies of the subsequent circuits in the prior art are usually directly supplied by the power supply circuit, so that corresponding voltage stabilizing elements are added, and the cost is high.

The MCU circuit is a programmable logic device or a DSP chip or a singlechip. The embodiment is a single chip microcomputer. The single chip microcomputer samples the input voltage in real time, and the signal sampling circuit provides a sampling signal S1. The invention adopts real-time voltage sampling based on a single chip microcomputer to monitor the current voltage input condition, if the current voltage input condition is met, a control signal (PWMStart) is generated to act on a starting coil T1B through a driving circuit, the starting coil is electrified in a short time, a larger electromagnetic force is formed, a spring is overcome, and a trip bar is sucked back.

As shown in fig. 2 and 3, the power supply and sustain coil control circuit includes a logic and driving circuit, a sustain coil T1A, a MOS transistor Q3, and a power supply circuit; one end of a maintaining coil T1A is connected with the output end of the rectifying circuit, the other end of the maintaining coil T1A is connected with an MOS transistor Q3, the other end of the maintaining coil T1A is simultaneously connected with the input end of a power circuit, and the output end of the power circuit is connected with the input end of a starting coil and a driving circuit and the input end of a power conversion circuit; the input end of the logic and drive circuit is connected with the output end of the MCU circuit, and the output end of the logic and drive circuit is connected with the MOS tube Q3. The maintenance coil is connected with the switch MOS tube in series and connected with the power circuit in series to take electricity for external high-voltage input, the operation mode solves the electricity taking problem of a microcontroller and related circuits of the control panel, and the electricity taking mode applies voltage drop to the maintenance coil so that the heat power consumption of components on the electronic circuit control panel is in a lower level; the tripping device is provided with larger starting torque, and meanwhile, the under-voltage tripping device can be ensured to stably work for a long time when the rated voltage is 110 percent.

As shown in fig. 2, the logic and driving circuit includes a logic chip U3 and a resistor R10; one end of a resistor R10 is connected with the gate of a MOS tube Q3, the other end of a resistor R10 is connected with a tenth pin of a logic chip U3, an eighth pin and a ninth pin of the logic chip U3 are connected with a third pin of a logic chip U3, a first pin of the logic chip U3 is connected with the drain of the MOS tube Q1, the drain of the MOS tube Q1 is connected with a power supply VDD through a resistor R8, the gate of the MOS tube Q1 is connected with the output end of the MCU circuit, the source of the MOS tube Q1 is grounded, and two ends of the resistor R12 are connected between the gate of the MOS tube Q1 and the source of the MOS tube Q1 in parallel; the second pin of the logic chip U3 is connected with the fourth pin of the logic chip U3, the capacitor C5 is connected in series with the resistor R16, one end of the capacitor C5 is connected with the fourth pin of the logic chip U3 after the series connection, one end of the resistor R16 is connected with the twelfth pin of the logic chip U3 and the thirteenth pin of the logic chip U3, one end of the resistor R15 is connected with the middle node of the capacitor C5 and the resistor R16, the other end is connected with the sixth pin of the logic chip U3 and the eleventh pin of the logic chip U3, the fifth pin of the logic chip U3 is connected to the drain of the MOS tube Q2, the drain of the MOS tube Q2 is connected to the power supply VDD through the resistor R9, the source of the MOS tube Q2 is grounded, the resistor R13 is connected in parallel between the gate of the MOS tube Q2 and the source of the MOS tube Q2, and the gate of the MOS tube Q2 is connected with the output. The logic and drive circuit is composed of a logic chip, the control input of the logic and drive circuit is output signals C1 and C2 at the control end of the singlechip, the C1 signal is a PWM signal given by the singlechip, the C2 signal is an enable signal of an internal 1kHz square wave oscillator, and VDD is the output of the power circuit; the logic chip U3 adopts an MC14011 chip, and the MC14011 chip generates a 1kHz control signal by self-excitation, so that continuous pulsating voltage is generated at a pin D of an MOS tube Q3, a stable voltage VDD is formed on a voltage regulator tube D4, and a power supply conversion circuit generates stable VCC3.3V.

As shown in fig. 3, the power supply circuit includes a resistor R5, a resistor R6, a resistor R4, a resistor R7, a capacitor C7, a voltage regulator D4, a diode D3, and a polarity capacitor C1; the cathode of the diode D3 is connected with the input end of the power conversion circuit and the input end of the start coil and the drive circuit, the anode of the polar capacitor C1 is connected with the cathode of the diode D3, the cathode of the polar capacitor C1 is connected with the cathode of the diode D3, the anode of the diode D3 is connected to one end of the holding coil T1A through the capacitor C4, and two ends of the resistor R5, the resistor R6, the resistor R4 and the resistor R7 which are connected in series are connected in parallel to two ends of the capacitor C4; the circuit also comprises a diode D2 and a resistor R14, two ends of the diode D2 are connected in parallel with two ends of the holding coil T1A, two ends of the resistor R14 are connected in parallel between the grid of the MOS tube Q3 and the source of the MOS tube Q3, the source of the MOS tube Q3 is grounded, the grid of the MOS tube Q3 is connected with the output end of the logic and driving circuit, and the other end of the holding coil T1A is connected with the output end of the signal sampling circuit.

As shown in fig. 1 and 5, the starting coil and driving circuit includes a starting coil T1B, a MOS transistor Q4 and a driving circuit; one end of the starting coil T1B is connected with the output end of the rectifying circuit, the other end of the starting coil T1B is connected with one end of the MOS tube Q4, the other end of the MOS tube Q4 is connected with the output end of the driving circuit, and the input end of the driving circuit is connected with the output end of the power supply electricity taking and maintaining coil control circuit and the output end of the MCU circuit. The starting coil and the control circuit are composed of a switching tube driving circuit, a switching tube and a starting coil, and the whole structure is simple and compact.

As shown in fig. 5, the driving circuit includes a driving chip U5, a resistor R24, a resistor R22, a resistor R25 and a capacitor C10; the drain of the MOS transistor Q4 is connected with the other end of the starting coil T1B, the resistor R24 is connected in parallel with the gate of the MOS transistor Q4 and the source of the MOS transistor Q4, the source of the MOS transistor Q4 is grounded, one end of the resistor R22 is connected with the gate of the MOS transistor Q4, the other end of the resistor R22 is connected with the fifth pin of the driving chip U5, the fourth pin of the driving chip U5 is grounded, the first pin of the driving chip U5 is grounded, the second pin of the driving chip U5 is grounded through the capacitor C10, and the second pin of the driving chip U5 is grounded through the resistor R25.

As shown in fig. 6, the EMC circuit includes a voltage dependent resistor RV1, a resistor R1, a resistor R3 and a capacitor C2, an external power supply is connected to the input end of the rectifier circuit in two paths through a resistor R1 and a resistor R3, a voltage dependent resistor RV1 is connected in parallel to the front ends of the resistor R1 and the resistor R3, and a capacitor C2 is connected in parallel to the rear ends of the resistor R1 and the resistor R3. The rectifying circuit comprises a rectifying bridge B1, the input end of the rectifying bridge B1 is connected with the output end of the EMC circuit, and the output end of the rectifying bridge B1 is connected with the power supply electricity taking and maintaining coil control circuit, the signal sampling circuit and the starting coil and the driving circuit. The EMC circuit is used for improving the anti-interference capability of the circuit and mainly comprises two anti-surge power resistors and a piezoresistor.

As shown in fig. 7, the signal sampling circuit includes a diode D5, a resistor R17, a resistor R21, a resistor R23, a resistor R30, a capacitor C11, a resistor R26, and a diode D7; the anode of the diode D5 is connected with the output end of the rectifying circuit, the cathode of the diode D5 is connected with the power supply power taking and maintaining coil control circuit, the resistor R17, the resistor R21, the resistor R23 and the resistor R30 are connected in series, the other end of the resistor R17 is connected with the anode of the diode D5, the other end of the resistor R30 is grounded, one end of the resistor R26 is connected with the middle node of the resistor R23 and the resistor R30, the other end of the resistor R26 is connected with the input end of the MCU circuit, the anode of the diode D7 is connected with the other end of the resistor R26, and the cathode of the diode D7 is connected with the power supply VCC. The signal sampling circuit consists of a divider resistor, and a diode D7 is additionally arranged to protect an IO port. The sampling circuit is composed of voltage-dividing resistors, an additional diode D7 protects the port IO, when the external voltage drops to 50% of rated voltage (or other set values between 35% -70% of rated voltage), the single chip outputs a signal C1(PWM _ Keep) to make C be logic 0 for about 50ms, at this time, the power circuit stops oscillating, no power supply is generated, and the power supply of the whole control circuit is provided by the electric energy stored in the capacitor of the power conversion circuit. At the moment, no current flows through the maintaining coil, the electromagnetic force disappears, and the tripper trips the circuit breaker under the action of the spring, so that the realization of undervoltage tripping is completed. After 50ms, C1(PWM _ Keep) generates the previous PWM wave again, the power circuit starts oscillation again, and the current is generated in the coil again. However, the current voltage value is still in an undervoltage state, and the tripper still maintains a tripping state without the action of a starting coil. As shown in fig. 4, the power conversion circuit includes a power conversion chip U4, a polar capacitor C9, a resistor R11, a polar capacitor C6, and a capacitor C7; the input end of a power conversion chip U4 is connected with the output end of a power circuit, the positive electrode of a polarity capacitor C9 is connected with the input end of a power conversion chip U4, the negative electrode of a polarity capacitor C9 is grounded, the output end of the power conversion chip U4 is connected with one end of a resistor R11, the other end of the resistor R11 is connected with one end of a polarity capacitor C6 and one end of a capacitor C7 which are connected in parallel, one end of the polarity capacitor C6 and one end of the capacitor C7 which are connected in parallel are simultaneously connected with an MCU circuit, and the other end of the polarity capacitor C6 and the other end of the capacitor C36.

The operation of the electronic control circuit for the undervoltage trip unit according to the present invention will be described with reference to fig. 2-6.

The control input of the power supply circuit is MCU circuit (singlechip) control end output signals C1(PWM _ Keep) and C2(Square _ Disable), the C1 signal is a PWM signal given by the singlechip, the C2 signal is an enable signal of an internal 1kHz Square wave oscillator, and VDD is the output of the power supply circuit. The control signal C of the MOS transistor Q3 is a · B, where the signal a is a logical not of C1(PWM _ Keep), the signal B is a self-excited 1kHz Square wave when C2(Square _ Disable) is 0, and is a logical 1 when C2(Square _ Disable) is 1. The power supply gets the electric work process as follows with the maintenance coil control circuit from external power source through EMC circuit access to circuit board:

the pulsating voltage of the pin D of the MOS transistor Q3 forms a voltage VDD on a voltage regulator tube D4 through a voltage unit consisting of a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor C4 and a resistor D4;

2. the voltage VDD is applied to a logic and driving circuit, and because the singlechip is not started at the moment, output signals C1(PWM _ Keep) and C2(Square _ Disable) of a control end of the singlechip are all logic 0, at the moment, the signal A is logic 1, and the signal B is a 1kHz Square wave generated by self-excitation; since the control signal C of the MOS transistor Q3 is a · B, C is also a 1kHz square wave at this time; under the action of the square wave, a pin D of the MOS tube Q3 generates continuous pulsating voltage, a voltage-stabilized VDD is formed on the voltage-stabilizing tube D4, and then the power conversion circuit generates stable VCC3.3V;

3. and then, the singlechip enters a normal working state, and the first operation is to take over the control signal C to separate the control signal C from the control of the 1kHz square wave generated by the self-excitation of the logic circuit, so that the control signal C generates an adjustable PWM wave instead of the square wave with fixed frequency. Under the control of the control signal C, the MOS tube Q3 regulates the current flowing through the holding coil according to the input voltage value to maintain the electromagnetic force in a relatively constant state, so that the movable iron core can be kept in a pull-in state, and the temperature rise of the whole coil can be within a certain range; on the other hand, the oscillating signal is generated later, so that the voltage regulator tube D4 can provide a stable voltage value. When the control signal C is taken over, the single chip microcomputer outputs a PWM signal C1(PWM _ Keep) and sets C2(Square _ Disable) to be logic 1, and the logic circuit stops oscillation. The control signal C at this time is a logical negation of C1(PWM _ Keep).

4. The single chip microcomputer samples the input voltage in real time, and the signal is provided by the signal sampling circuit. The signal sampling circuit consists of a divider resistor, and a diode D7 is additionally arranged to protect an IO port. When the external voltage is reduced to 50% of the rated voltage (or other set values between 35% and 70% of the rated voltage), the singlechip outputs a signal C1(PWM _ Keep) to enable C to be logic 0 for about 50ms, at the moment, the power supply circuit stops oscillating, power supply is not generated, and the power supply of the whole control circuit is provided by the electric energy stored in the capacitor in the power conversion circuit. At the moment, no current flows through the maintaining coil, the electromagnetic force disappears, and the tripper trips the circuit breaker under the action of the spring, so that the realization of undervoltage tripping is completed. After 50ms, C1(PWM _ Keep) generates the previous PWM wave again, the power circuit starts oscillation again, and the current is generated in the coil again. However, the current voltage value is still in an undervoltage state, and the tripper still maintains a tripping state without the action of a starting coil.

5. When the external input voltage is normal, the singlechip generates a control signal (PWM Start) to act on the starting coil T1B through the driving circuit, the starting coil is electrified in a short time to form larger electromagnetic force, the spring is overcome, and the trip rod is sucked back.

The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims

1. An electronic control circuit for an undervoltage release is characterized in that: the power supply comprises an EMC circuit, a rectifying circuit, a signal sampling circuit, a power supply electricity taking and maintaining coil control circuit, a power supply conversion circuit, a starting coil and driving circuit and an MCU circuit;

the input end of the EMC circuit is connected with the input end of an external power supply, the output end of the EMC circuit is connected with the input end of the rectifying circuit, the rectifying circuit rectifies the external power supply into direct current, and the output end of the rectifying circuit is respectively connected with the power supply electricity taking and maintaining coil control circuit, the signal sampling circuit, the starting coil and the driving circuit;

the output end of the signal sampling circuit is connected with the input end of the power supply electricity taking and maintaining coil control circuit and the input end of the MCU circuit, and the output end of the power supply electricity taking and maintaining coil control circuit is connected with the input ends of the starting coil and the driving circuit;

the input end of the power supply conversion circuit is connected with the output end of the power supply electricity taking and maintaining coil control circuit, the output end of the power supply conversion circuit is connected with the input end of the MCU circuit, and the output end of the MCU circuit is connected with the starting coil and the driving circuit and the power supply electricity taking and maintaining coil control circuit; the power supply electricity taking and maintaining coil control circuit comprises a logic and driving circuit, a maintaining coil T1A, an MOS tube Q3 and a power supply circuit; one end of a maintaining coil T1A is connected with the output end of the rectifying circuit, the other end of the maintaining coil T1A is connected with an MOS transistor Q3, the other end of the maintaining coil T1A is simultaneously connected with the input end of a power circuit, and the output end of the power circuit is connected with the input end of a starting coil and a driving circuit and the input end of a power conversion circuit; the input end of the logic and drive circuit is connected with the output end of the MCU circuit, and the output end of the logic and drive circuit is connected with the MOS tube Q3.

2. The electronic control circuit for an undervoltage trip unit of claim 1, wherein: the logic and driving circuit comprises a logic chip U3 and a resistor R10; the logic chip U3 adopts an MC14011 chip, one end of a resistor R10 is connected with the gate of a MOS tube Q3, the other end of the resistor R10 is connected with a tenth pin of the logic chip U3, an eighth pin and a ninth pin of the logic chip U3 are connected with a third pin of a logic chip U3, a first pin of the logic chip U3 is connected with the drain of the MOS tube Q1, the drain of the MOS tube Q1 is connected with a power supply VDD through the resistor R8, the gate of the MOS tube Q1 is connected with the output end of the MCU circuit, the source of the MOS tube Q1 is grounded, and two ends of the resistor R12 are connected between the gate of the MOS tube Q1 and the source of the MOS tube Q1 in parallel; the second pin of the logic chip U3 is connected with the fourth pin of the logic chip U3, the capacitor C5 is connected in series with the resistor R16, one end of the capacitor C5 is connected with the fourth pin of the logic chip U3 after the series connection, one end of the resistor R16 is connected with the twelfth pin of the logic chip U3 and the thirteenth pin of the logic chip U3, one end of the resistor R15 is connected with the middle node of the capacitor C5 and the resistor R16, the other end is connected with the sixth pin of the logic chip U3 and the eleventh pin of the logic chip U3, the fifth pin of the logic chip U3 is connected to the drain of the MOS tube Q2, the drain of the MOS tube Q2 is connected to the power supply VDD through the resistor R9, the source of the MOS tube Q2 is grounded, the resistor R13 is connected in parallel between the gate of the MOS tube Q2 and the source of the MOS tube Q2, and the gate of the MOS tube Q2 is connected with the output.

3. The electronic control circuit for an undervoltage trip unit of claim 1, wherein: the power supply circuit comprises a resistor R5, a resistor R6, a resistor R4, a resistor R7, a capacitor C7, a voltage regulator tube D4, a diode D3 and a polarity capacitor C1; the cathode of the diode D3 is connected with the input end of the power conversion circuit and the input end of the start coil and the drive circuit, the anode of the polar capacitor C1 is connected with the cathode of the diode D3, the cathode of the polar capacitor C1 is connected with the cathode of the diode D3, the anode of the diode D3 is connected to one end of the holding coil T1A through the capacitor C4, and two ends of the resistor R5, the resistor R6, the resistor R4 and the resistor R7 which are connected in series are connected in parallel to two ends of the capacitor C4; the circuit also comprises a diode D2 and a resistor R14, two ends of the diode D2 are connected in parallel with two ends of the holding coil T1A, two ends of the resistor R14 are connected in parallel between the grid of the MOS tube Q3 and the source of the MOS tube Q3, the source of the MOS tube Q3 is grounded, the drain of the MOS tube Q3 is connected with the output end of the logic and driving circuit, and the other end of the holding coil T1A is connected with the output end of the signal sampling circuit.

4. The electronic control circuit for an undervoltage trip unit of claim 1, wherein: the starting coil and driving circuit comprises a starting coil T1B, a MOS tube Q4 and a driving circuit; one end of the starting coil T1B is connected with the output end of the rectifying circuit, the other end of the starting coil T1B is connected with one end of the MOS tube Q4, the other end of the MOS tube Q4 is connected with the output end of the driving circuit, and the input end of the driving circuit is connected with the output end of the power supply electricity taking and maintaining coil control circuit and the output end of the MCU circuit.

5. The electronic control circuit for an undervoltage trip unit of claim 4, wherein: the driving circuit comprises a driving chip U5, a resistor R24, a resistor R22, a resistor R25 and a capacitor C10; the drain of the MOS transistor Q4 is connected with the other end of the starting coil T1B, the resistor R24 is connected in parallel with the gate of the MOS transistor Q4 and the source of the MOS transistor Q4, the source of the MOS transistor Q4 is grounded, one end of the resistor R22 is connected with the gate of the MOS transistor Q4, the other end of the resistor R22 is connected with the fifth pin of the driving chip U5, the fourth pin of the driving chip U5 is grounded, the first pin of the driving chip U5 is grounded, the second pin of the driving chip U5 is grounded through the capacitor C10, and the second pin of the driving chip U5 is grounded through the resistor R25.

6. The electronic control circuit for an undervoltage trip unit of claim 1, wherein: the EMC circuit comprises a voltage dependent resistor RV1, a resistor R1, a resistor R3 and a capacitor C2, an external power supply is divided into two paths and is connected to the input end of the rectifying circuit through the resistor R1 and the resistor R3 respectively, the voltage dependent resistor RV1 is connected to the front ends of the resistor R1 and the resistor R3 in parallel, and the capacitor C2 is connected to the rear ends of the resistor R1 and the resistor R3 in parallel; the rectifying circuit comprises a rectifying bridge B1, the input end of the rectifying bridge B1 is connected with the output end of the EMC circuit, and the output end of the rectifying bridge B1 is connected with the power supply electricity taking and maintaining coil control circuit, the signal sampling circuit and the starting coil and the driving circuit.

7. The electronic control circuit for an undervoltage trip unit of claim 1, wherein: the signal sampling circuit comprises a diode D5, a resistor R17, a resistor R21, a resistor R23, a resistor R30, a capacitor C11, a resistor R26 and a diode D7; the anode of the diode D5 is connected with the output end of the rectifying circuit, the cathode of the diode D5 is connected with the power supply power taking and maintaining coil control circuit, the resistor R17, the resistor R21, the resistor R23 and the resistor R30 are connected in series, the other end of the resistor R17 is connected with the anode of the diode D5, the other end of the resistor R30 is grounded, one end of the resistor R26 is connected with the middle node of the resistor R23 and the resistor R30, the other end of the resistor R26 is connected with the input end of the power supply power taking and MCU circuit, the anode of the diode D7 is connected with the other end of the resistor R26, and the cathode of the diode D7 is connected with the power.

8. The electronic control circuit for an undervoltage trip unit of claim 1, wherein: the power conversion circuit comprises a power conversion chip U4, a polar capacitor C9, a resistor R11, a polar capacitor C6 and a capacitor C7; the input end of a power conversion chip U4 is connected with the output end of a power circuit, the positive electrode of a polarity capacitor C9 is connected with the input end of a power conversion chip U4, the negative electrode of a polarity capacitor C9 is grounded, the output end of the power conversion chip U4 is connected with one end of a resistor R11, the other end of the resistor R11 is connected with one end of a polarity capacitor C6 and one end of a capacitor C7 which are connected in parallel, one end of the polarity capacitor C6 and one end of the capacitor C7 which are connected in parallel are simultaneously connected with an MCU circuit, and the other end of the polarity capacitor C6 and the other end of the capacitor C36.

9. The electronic control circuit for an undervoltage trip unit of claim 1, wherein: the MCU circuit is a programmable logic device or a DSP chip or a singlechip.