Discharging circuit of electric control board

Abstract

The utility model relates to a discharging circuit of an electric control board, comprising a power supply conversion unit used for converting an input power supply into a working voltage of the electric control board; the discharging circuit is connected with the power supply conversion unit and is used for discharging the residual electric energy of the electric control board through the discharging circuit when the power supply is powered down; the single chip microcomputer is connected with the power conversion unit and the discharge circuit and used for controlling the start and stop of the discharge circuit; the alternating current zero-crossing detection circuit is connected with the single-chip microcomputer and is used for detecting a zero-crossing signal of an alternating current power supply and providing a signal for the single-chip microcomputer when power failure is detected; when the single-chip microcomputer receives a power-down signal provided by the alternating-current zero-cross detection circuit, the discharging circuit is started, so that residual electric energy in the electric control board is discharged through the discharging circuit. According to the discharge circuit of the electric control board provided by the utility model, rapid discharge of the primary side of the power supply is realized by adding the discharge circuit, and a special discharge chip is not needed, so that the manufacturing cost is reduced, and the economical efficiency is high.

Description

Technical Field

[0001] This utility model belongs to the field of microwave oven technology, specifically relating to a discharge circuit for an electronic control board. Background Technology

[0002] Traditional microwave ovens consist of a cavity, control system, cooling system, lighting system, magnetron, and magnetron drive power supply, among which the magnetron drive power supply is a traditional power frequency leakage transformer. With technological advancements and increased energy conservation awareness, a new type of switching power supply is gradually replacing the traditional power frequency leakage transformer, commonly known as an electronic transformer or frequency converter. Microwave ovens using electronic transformers offer advantages such as energy saving, lighter weight, better cooking results, and quieter operation; however, because of the use of switching power supplies, electromagnetic emissions increase significantly, necessitating the redesign of new filters.

[0003] To achieve better EMI suppression when using electronic transformers or frequency converters, larger-capacity X capacitors are typically used in new filters. These X capacitors usually have a capacitance of 2.2uF or higher. According to national safety regulations, after a microwave oven power plug is unplugged, the residual voltage on the plug should drop to below 34V within one second to prevent injury from excessive voltage after contact with the plug. However, the use of large-capacity X capacitors necessitates a reduction in the resistance value of the associated discharge resistor, which in turn increases standby power consumption. Therefore, at least one discharge chip needs to be installed on the filter board of the electronic transformer or frequency converter to replace the discharge resistor, meeting national safety regulations and standby power consumption requirements. However, discharge chips are expensive, significantly increasing manufacturing costs and making them uneconomical.

[0004] Therefore, this utility model provides a discharge circuit for an electronic control board to solve the above-mentioned technical problems. Utility Model Content

[0005] To address the aforementioned problems, the purpose of this utility model is to provide a discharge circuit for an electronic control board, which achieves rapid discharge to the primary side of the power supply by adding a discharge circuit, without the need for a dedicated discharge chip, thereby reducing manufacturing costs and achieving high economic efficiency.

[0006] This utility model provides a discharge circuit for an electronic control board, which includes...

[0007] A power conversion unit is used to convert the input power into the voltage at which the electronic control board operates.

[0008] A discharge circuit, connected to the power conversion unit, is used to discharge the remaining electrical energy of the electronic control board when the power is lost.

[0009] A microcontroller is connected to the power conversion unit and the discharge circuit to control the start and stop of the discharge circuit.

[0010] An AC zero-crossing detection circuit, connected to the microcontroller, is used to detect the zero-crossing signal of the AC power supply and to provide a signal to the microcontroller when a power failure is detected.

[0011] When the microcontroller receives the power-down signal provided by the AC zero-crossing detection circuit, it activates the discharge circuit to release the remaining electrical energy in the electronic control board.

[0012] Preferably, the power conversion unit includes an inductor connected to an external filter board, a rectifier assembly connected to the inductor, a bus capacitor connected to the rectifier assembly, and a converter connected to the bus capacitor; the discharge circuit is connected to the converter.

[0013] Preferably, the rectifier assembly includes a first rectifier assembly connected to the inductor and a second rectifier assembly connected in parallel with the first rectifier assembly and connected to the bus capacitor; the first rectifier assembly includes a first rectifier tube and a second rectifier tube connected in series, with the negative terminal of the first rectifier tube and the positive terminal of the second rectifier tube connected to the inductor; the second rectifier assembly includes a third rectifier tube and a fourth rectifier tube connected in series, with the positive terminal of the third rectifier tube connected to the positive terminal of the first rectifier tube and the bus capacitor, the negative terminal of the third rectifier tube connected to the positive terminal of the fourth rectifier tube, and the negative terminal of the fourth rectifier tube connected to the negative terminal of the second rectifier tube and the bus capacitor.

[0014] Preferably, the discharge circuit includes a first resistor, a transistor, and a second resistor. One end of the first resistor is connected to the converter, and the other end of the first resistor is connected to the collector of the transistor. The base of the transistor is connected to one end of the second resistor, and the other end of the second resistor is connected to the microcontroller.

[0015] Preferably, the AC zero-crossing circuit includes a fifth rectifier diode, a third resistor, a fourth resistor, an optocoupler unit, and a fifth resistor. The positive terminal of the fifth rectifier diode is connected to the inductor, the negative terminal of the fifth rectifier diode is connected to one end of the third resistor, the other end of the third resistor is connected to the fourth resistor, the other end of the fourth resistor is connected to the optocoupler unit, the other end of the optocoupler unit is connected to both the fifth resistor and the microcontroller, and the other end of the fifth resistor is connected to the converter.

[0016] Preferably, the filter board includes a resistance wire and a filtering circuit connected in series with the resistance wire. The filtering circuit includes a varistor, a discharge resistor, a first X capacitor, a common-mode inductor, a Y capacitor assembly, and a second X capacitor connected in parallel in sequence, and the output terminal of the second X capacitor is connected to the inductor. The Y capacitor assembly includes a first Y capacitor and a second Y capacitor connected in series.

[0017] Preferably, the discharge circuit of the electronic control board further includes a display unit, a relay unit, a buzzer unit, a key input unit, and a gate control signal input unit. The display unit, the relay unit, and the buzzer unit are simultaneously connected to the converter and the microcontroller, and the key input unit and the gate control signal input unit are interconnected with the microcontroller.

[0018] Compared with related technologies, the present invention provides a discharge circuit for an electronic control board, which includes a power conversion unit for converting the input power supply into the voltage for the electronic control board to operate; a discharge circuit connected to the power conversion unit for discharging the remaining electrical energy of the electronic control board when the power supply fails; a microcontroller connected to the power conversion unit and the discharge circuit for controlling the start and stop of the discharge circuit; and an AC zero-crossing detection circuit connected to the microcontroller for detecting the zero-crossing signal of the AC power supply and providing a signal to the microcontroller when a power failure is detected. When the microcontroller receives the power failure signal provided by the AC zero-crossing detection circuit, it starts the discharge circuit, allowing the remaining electrical energy in the electronic control board to be discharged through the discharge circuit. In the above structure, by adding a discharge circuit to the control terminal of the microcontroller, when the microcontroller receives the AC zero-crossing signal from the AC zero-crossing circuit, it detects the AC power failure. After detecting the power failure signal, it starts the discharge circuit. The discharge circuit uses the load terminal of the power supply to achieve rapid discharge on the primary side of the power supply. It does not require a dedicated discharge chip for discharge, thereby reducing manufacturing costs and improving economy. Moreover, the structure of the discharge circuit is simple and has wide applicability. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the discharge circuit of an electronic control board according to the present invention.

[0020] Figure 2 This is a schematic diagram of the circuit structure of the filter board described in this utility model.

[0021] Reference numerals: Power conversion unit-10; Rectifier tube assembly-1; Display unit-2; Relay unit-3; Buzzer unit-4; Discharge circuit-5; Microcontroller-6; Key input unit-7; Gate control signal input unit-8; AC zero-crossing circuit-9; Y capacitor assembly-20. Detailed Implementation

[0022] This invention provides a discharge circuit for an electronic control board, aiming to solve the problems of high manufacturing cost and poor economic efficiency of filter boards used in electronic transformers.

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0024] Please also refer to the appendix. Figure 1-2 This utility model provides a discharge circuit for an electronic control board, comprising a power conversion unit 10 for converting input power into the operating voltage of the electronic control board; a discharge circuit 5 connected to the power conversion unit 10 for discharging residual electrical energy of the electronic control board when the power is lost; a microcontroller 6 connected to the power conversion unit 10 and the discharge circuit 5 for controlling the start and stop of the discharge circuit 5; and an AC zero-crossing detection circuit 9 connected to the microcontroller 6 for detecting the zero-crossing signal of the AC power supply and providing a signal to the microcontroller 6 when a power loss is detected. When the microcontroller 6 receives the power loss signal provided by the AC zero-crossing detection circuit 9, it activates the discharge circuit 5, allowing the residual electrical energy in the electronic control board to be discharged through the discharge circuit 5.

[0025] In the above structure, by adding a discharge circuit 5 to the control terminal of the microcontroller 6, when the microcontroller 6 receives the AC zero-crossing signal from the AC zero-crossing circuit, it detects the AC power failure. After detecting the power failure signal, it starts the discharge circuit 5. The discharge circuit 5 uses the load end of the power supply to achieve rapid discharge on the primary side of the power supply. It does not require a dedicated discharge chip for discharge, thereby reducing manufacturing costs and improving economy. Moreover, the structure of the discharge circuit is simple and has wide applicability.

[0026] Specifically, the power conversion unit 10 includes an inductor L2 connected to an external filter board, a rectifier assembly 1 connected to the inductor L2, a bus capacitor EC1 connected to the rectifier assembly 1, and a converter M1 connected to the bus capacitor EC1; the discharge circuit 5 is connected to the converter M1.

[0027] Furthermore, the rectifier assembly 1 includes a first rectifier assembly 11 connected to the inductor L2 and a second rectifier assembly 12 connected in parallel with the first rectifier assembly 11 and connected to the bus capacitor EC1; the first rectifier assembly 11 includes a first rectifier D1 and a second rectifier D2 connected in series, the negative terminal of the first rectifier D1 and the positive terminal of the second rectifier D2 are connected to the inductor L2; the second rectifier assembly 12 includes a third rectifier D3 and a fourth rectifier D4 connected in series, the positive terminal of the third rectifier D3 is connected to the positive terminal of the first rectifier D1 and the bus capacitor EC1, the negative terminal of the third rectifier D3 is connected to the positive terminal of the fourth rectifier D4, and the negative terminal of the fourth rectifier D4 is connected to the negative terminal of the second rectifier D2 and the bus capacitor EC1.

[0028] In this embodiment, the discharge circuit 5 includes a first resistor R1, a transistor Q1, and a second resistor R2. One end of the first resistor R1 is connected to the converter M1, and the other end of the first resistor R1 is connected to the collector of the transistor Q1. The base of the transistor Q1 is connected to one end of the second resistor R2, and the other end of the second resistor R2 is connected to the microcontroller 6.

[0029] Furthermore, the AC zero-crossing circuit 9 includes a fifth rectifier diode D5, a third resistor R3, a fourth resistor R4, an optocoupler unit U2, and a fifth resistor R5. The positive terminal of the fifth rectifier diode D5 is connected to the inductor L2, the negative terminal of the fifth rectifier diode D5 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to the fourth resistor R4, the other end of the fourth resistor R4 is connected to the optocoupler unit U2, the other end of the optocoupler unit U2 is connected to both the fifth resistor R5 and the microcontroller 6, and the other end of the fifth resistor R5 is connected to the first terminal of the converter M1.

[0030] In this embodiment, the filter board includes a resistance wire F1 and a filtering circuit connected in series with the resistance wire F1. The filtering circuit includes a varistor ZR1, a discharge resistor R6, a first X capacitor C1, a common mode inductor L1, a Y capacitor assembly 20, and a second X capacitor C2 connected in parallel in sequence, and the output terminal of the second X capacitor C2 is connected to the inductor L2. The Y capacitor assembly 20 includes a first Y capacitor CY1 and a second Y capacitor CY2 connected in series.

[0031] It is worth mentioning that the discharge circuit of the electronic control board also includes a display unit 2, a relay unit 3, a buzzer unit 4, a key input unit 7, and a gate control signal input unit 8. The display unit 2, the relay unit 3, and the buzzer unit 4 are connected to the converter M1 and the microcontroller 6, and the key input unit 7 and the gate control signal input unit 8 are interconnected with the microcontroller 6.

[0032] It should be noted that the converter M1 is a DC-DC converter, typically a flyback circuit, outputting two voltages: 12V and 5V. The 12V supply powers the relay unit 3, buzzer unit 4, and discharge circuit 5. The relay unit 3 provides AC power to the electronic transformer or frequency converter, as well as controls the furnace lamp and AC cooling fan. The 5V supply powers the optocoupler U2, microcontroller 6, and display unit 2. An AC zero-crossing circuit 9 is connected to the input port of the microcontroller 6. This circuit consists of the fifth rectifier diode D5, the third resistor R3, the fourth resistor R4, the optocoupler U2, and the fifth resistor R5. When the microcontroller 6 receives the AC zero-crossing signal, it uses an appropriate delay to control the conduction of the relay unit 3, reducing the inrush current when the relay unit 3 engages. The microcontroller 6 is also connected to a key input unit 7 and a door control signal input unit 8. The key input unit 7 is typically a matrix scanning circuit used to receive key commands from the panel. The door control signal input unit 8 detects the opening and closing of the furnace door, preventing microwave and other functions from operating when the furnace door is open to ensure user safety.

[0033] It is worth mentioning that the working principle of the above discharge circuit is as follows: When the power plug of the microwave oven is unplugged, the AC zero-crossing signal is lost. After the microcontroller detects the loss of the AC zero-crossing signal, it sends a high-level command, the transistor Q1 conducts, and the 12V power supply is discharged through the first resistor R1. The capacitance of the bus capacitor EC1 is usually 4.7-10uF, and the electrical energy stored in it can be expressed by the formula W = 1 / 2 * CU^2. Taking an input voltage of 240V, a bus capacitor EC1 capacitance of 10uF, and a total capacitance of 3.2uF for the first X capacitor C1 and the second X capacitor C2 as an example, the total electrical energy stored at the input terminal is W = 0.5 * 13.2uF * (240 * 1.414)^2 = 0.76J. If this electrical energy is to be released completely within 0.5 seconds, the required discharge power is 0.76J / 0.5S = 1.512W. Without considering converter efficiency, the designed discharge power is 1.5W, resulting in a discharge resistor R6 of 96 ohms. Therefore, a 100-ohm, 1W resistor can be used as the discharge resistor. Typically, a well-designed converter can achieve normal voltage output at DC voltages above 40V. After the converter stops working, the residual voltage at the input continues to discharge through the filter board's discharge resistor to keep it below 34V.

[0034] In addition, the chip model used in the discharge circuit of the electronic control board provided by this utility model is SC95F8616BP44R. The microcontroller 6 is model PN8200SEC-R1.

[0035] Compared with related technologies, the present invention provides a discharge circuit for an electronic control board, which includes a power conversion unit for converting the input power supply into the voltage for the electronic control board to operate; a discharge circuit connected to the power conversion unit for discharging the remaining electrical energy of the electronic control board when the power supply fails; a microcontroller connected to the power conversion unit and the discharge circuit for controlling the start and stop of the discharge circuit; and an AC zero-crossing detection circuit connected to the microcontroller for detecting the zero-crossing signal of the AC power supply and providing a signal to the microcontroller when a power failure is detected. When the microcontroller receives the power failure signal provided by the AC zero-crossing detection circuit, it starts the discharge circuit, allowing the remaining electrical energy in the electronic control board to be discharged through the discharge circuit. In the above structure, by adding a discharge circuit to the control terminal of the microcontroller, when the microcontroller receives the AC zero-crossing signal from the AC zero-crossing circuit, it detects the AC power failure. After detecting the power failure signal, it starts the discharge circuit. The discharge circuit uses the load terminal of the power supply to achieve rapid discharge on the primary side of the power supply. It does not require a dedicated discharge chip for discharge, thereby reducing manufacturing costs and improving economy. Moreover, the structure of the discharge circuit is simple and has wide applicability.

[0036] It should be noted that the above-described embodiments should be understood as illustrative, not as limiting the scope of protection of this utility model, which is defined by the claims. For those skilled in the art, non-essential improvements and adjustments made to this utility model without departing from its essence and scope still fall within the scope of protection of this utility model.

Claims

1. A discharge circuit for an electronic control board, characterized in that, The discharge circuit of the electronic control board includes: A power conversion unit is used to convert the input power into the voltage at which the electronic control board operates. A discharge circuit, connected to the power conversion unit, is used to discharge the remaining electrical energy of the electronic control board when the power is lost. A microcontroller is connected to the power conversion unit and the discharge circuit to control the start and stop of the discharge circuit. An AC zero-crossing detection circuit, connected to the microcontroller, is used to detect the zero-crossing signal of the AC power supply and to provide a signal to the microcontroller when a power failure is detected. When the microcontroller receives the power-down signal provided by the AC zero-crossing detection circuit, it activates the discharge circuit to release the remaining electrical energy in the electronic control board.

2. The discharge circuit of the electronic control board according to claim 1, characterized in that, The power conversion unit includes an inductor connected to an external filter board, a rectifier assembly connected to the inductor, a bus capacitor connected to the rectifier assembly, and a converter connected to the bus capacitor; the discharge circuit is connected to the converter.

3. The discharge circuit of the electronic control board according to claim 2, characterized in that, The rectifier assembly includes a first rectifier assembly connected to the inductor and a second rectifier assembly connected in parallel with the first rectifier assembly and connected to the bus capacitor. The first rectifier assembly includes a first rectifier tube and a second rectifier tube connected in series, with the negative terminal of the first rectifier tube and the positive terminal of the second rectifier tube connected to the inductor. The second rectifier assembly includes a third rectifier tube and a fourth rectifier tube connected in series, with the positive terminal of the third rectifier tube connected to the positive terminal of the first rectifier tube and the bus capacitor, the negative terminal of the third rectifier tube connected to the positive terminal of the fourth rectifier tube, and the negative terminal of the fourth rectifier tube connected to the negative terminal of the second rectifier tube and the bus capacitor.

4. The discharge circuit of the electronic control board according to claim 3, characterized in that, The discharge circuit includes a first resistor, a transistor, and a second resistor. One end of the first resistor is connected to the converter, and the other end of the first resistor is connected to the collector of the transistor. The base of the transistor is connected to one end of the second resistor, and the other end of the second resistor is connected to the microcontroller.

5. The discharge circuit of the electronic control board according to claim 4, characterized in that, The AC zero-crossing detection circuit includes a fifth rectifier diode, a third resistor, a fourth resistor, an optocoupler unit, and a fifth resistor. The positive terminal of the fifth rectifier diode is connected to the inductor, the negative terminal of the fifth rectifier diode is connected to one end of the third resistor, the other end of the third resistor is connected to the fourth resistor, the other end of the fourth resistor is connected to the optocoupler unit, the other end of the optocoupler unit is connected to both the fifth resistor and the microcontroller, and the other end of the fifth resistor is connected to the converter.

6. The discharge circuit of the electronic control board according to claim 5, characterized in that, The filter board includes a resistance wire and a filtering circuit connected in series with the resistance wire. The filtering circuit includes a varistor, a discharge resistor, a first X capacitor, a common-mode inductor, a Y capacitor assembly, and a second X capacitor connected in parallel in sequence, and the output terminal of the second X capacitor is connected to the inductor. The Y capacitor assembly includes a first Y capacitor and a second Y capacitor connected in series.

7. The discharge circuit of the electronic control board according to claim 2, characterized in that, The discharge circuit of the electronic control board also includes a display unit, a relay unit, a buzzer unit, a key input unit, and a gate control signal input unit. The display unit, the relay unit, and the buzzer unit are connected to both the converter and the microcontroller. The key input unit and the gate control signal input unit are interconnected with the microcontroller.

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