AC-AC conversion circuit and converter

Abstract

The invention discloses an AC-AC conversion circuit and a converter. The conversion circuit comprises an MCU and an AC conversion module. The alternating current conversion module comprises an optocoupler OP1, resistors R1, R2 and R3, diodes MD1, MD2, MD3 and MD4, and switching tubes Q1 and Q2; the input end of the optical coupler OP1 is connected with a power supply voltage VIN and the MCU. One output end of the optocoupler OP1 is connected with a first end of first alternating current and one power supply end of a load through a circuit formed by MD1, MD3, R2 and Q1; the other output end of the optical coupler OP1 is connected with the second end of the first alternating current and the other power supply end of the load through a circuit formed by MD2, MD4, R3 and Q2; and the alternating current conversion module converts the first alternating current into second alternating current and outputs the second alternating current to a load based on the PWM control signal sent by the MCU. The problems that an existing circuit is low in conversion efficiency and high in cost are solved.

Description

Technical Field

[0001] The present application relates to the technical field of voltage conversion, and in particular to an AC-AC conversion circuit and a converter. Background Art

[0002] In the field of power electronics, an AC-AC (alternating current-alternating current) conversion circuit is a device used to convert one form of alternating current into another form of alternating current. This conversion process may not only involve the adjustment of voltage and current amplitude, but also the change of frequency or phase, so as to meet the diverse requirements of various loads on power supply characteristics. In the prior art, circuits for AC-AC conversion generally adopt an indirect conversion method of first converting AC to DC and then converting it to AC. This method has the disadvantages of low conversion efficiency and high circuit cost. Summary of the invention

[0003] In order to solve the problems of low conversion efficiency and high circuit cost of existing circuits used for AC-AC conversion, the present application provides an AC-AC conversion circuit and a converter.

[0004] In a first aspect, the present application provides an AC-AC conversion circuit, which adopts the following technical solution: The AC-AC conversion circuit comprises an MCU and an AC power conversion module; the input end of the AC power conversion module is connected to the MCU, and the output end is connected to the load; The AC power conversion module is used to receive the first AC power, and is also used to convert the first AC power into the second AC power and output it to the load based on the PWM control signal sent by the MCU; The AC power conversion module includes an optical coupler OP1, a resistor R1, a resistor R2, a resistor R3, a diode MD1, a diode MD2, a diode MD3, a diode MD4, a switch tube Q1, and a switch tube Q2; the optical coupler OP1 is a bidirectional thyristor output optical coupler; The first input terminal of the optical coupler OP1 is connected to the power supply voltage VIN through the resistor R1, and the second input terminal is connected to the MCU; The first output end of the optical coupler OP1 is respectively connected to the first end of the diode MD1, the first end of the resistor R2 and the driving end of the switch tube Q1; the first end of the first alternating current is respectively connected to the second end of the diode MD1, the second end of the resistor R2, the first end of the switch tube Q1 and the first end of the diode MD3; the second end of the switch tube Q1 is respectively connected to the second end of the diode MD3 and a power supply end of the load; The second output end of the optocoupler OP1 is respectively connected to the first end of the diode MD2, the first end of the resistor R3 and the driving end of the switch tube Q2; the second end of the first alternating current is respectively connected to the first end of the diode MD4, the first end of the switch tube Q2, the second end of the resistor R3 and the second end of the diode MD2; the second end of the switch tube Q2 is respectively connected to the second end of the diode MD4 and another power supply end of the load.

[0005] By adopting the above technical solution, the AC voltage conversion module is designed so that the AC voltage conversion module receives the first AC power and converts it into the second AC power to power the load, and the MCU is used to output a PWM control signal to the AC voltage conversion module to control the voltage of the output second AC power. Through such a design, AC-AC conversion can be directly realized. Compared with the traditional method of first converting AC power into DC power and then converting it into AC power, the energy loss of the system is reduced, the conversion efficiency is improved, and the circuit structure is easy to implement, which reduces the cost and is convenient for large-scale promotion and application.

[0006] In a specific implementation scheme, the MCU is used to control the on and off of the optical coupler OP1 by sending a PWM control signal to the input end of the optical coupler OP1; When the optocoupler OP1 is turned on, and the first end of the first alternating current outputs a forward current, the first end of the first alternating current, the resistor R2, the optocoupler OP1, the diode MD2, and the second end of the first alternating current form a current loop, driving the switch tube Q1 to be turned on, so that the first end of the first alternating current, the switch tube Q1, the load, the diode MD4, and the second end of the first alternating current form a current loop, forming a positive half cycle of the second alternating current on the load; When the optocoupler OP1 is turned on and the second end of the first alternating current outputs a forward current, the second end of the first alternating current, the resistor R3, the optocoupler OP1, the diode MD1 and the first end of the first alternating current form a current loop, driving the switch tube Q2 to be turned on, so that the second end of the first alternating current, the switch tube Q2, the load, the diode MD3 and the first end of the first alternating current form a current loop, forming a negative half cycle of the second alternating current on the load.

[0007] In a specific possible implementation scheme, the AC-AC conversion circuit further includes a first alternating current detection module; The MCU is connected to the output end of the first alternating current detection module, and is used to detect the cycle of the first alternating current through the first alternating current detection module; Wherein, the first AC power detection module includes: a resistor R4, a resistor R5, a resistor R6, a resistor R7, a diode MD5, an optical coupler OP2 and a transistor Q3; The first input end of the optical coupler OP2 is connected to the first end of the first alternating current through the resistor R4 and the resistor R5, and the second input end of the optical coupler OP2 is connected to the second end of the first alternating current; the diode MD5 is connected to the two input ends of the optical coupler OP2 respectively; The first output end of the optical coupler OP2 is connected to the driving end of the transistor Q3 and the first end of the resistor R6 respectively; the first end of the transistor Q3 is connected to the MCU and the first end of the resistor R7 respectively, and the second end of the resistor R6 and the second end of the resistor R7 are both connected to the power supply voltage VCC; the second end of the transistor Q3 is grounded; the second output end of the optical coupler OP2 is grounded.

[0008] By adopting the above technical solution, the first AC power detection module can output a square wave signal to the MCU according to the first AC power. By continuously detecting the voltage at the output end of the first AC power detection module, the MCU can accurately obtain the time interval between two adjacent rising edges of the square wave signal, thereby obtaining the period of the first AC power.

[0009] In a specific possible implementation scheme, the AC-AC conversion circuit further includes an output voltage detection module and a metering chip; The metering chip is connected to the output voltage detection module and the MCU respectively; the metering chip is used to detect the voltage value of the second alternating current output by the alternating current conversion module through the output voltage detection module, and output the voltage value to the MCU; Wherein, the output voltage detection module includes: a resistor R8, a resistor R9, a resistor R10, a voltage transformer PT1 and a capacitor C1; The first input end of the voltage transformer PT1 is connected to an output end of the AC power conversion module outputting the second AC power through the resistor R8 and the resistor R9; the second input end of the voltage transformer PT1 is connected to another output end of the AC power conversion module outputting the second AC power; The first output end of the voltage transformer PT1 is respectively connected to the first end of the resistor R10, the first end of the capacitor C1 and the metering chip; the second output end of the voltage transformer PT1 is respectively connected to the second end of the resistor R10 and the second end of the capacitor C1, and the second output end of the voltage transformer PT1 is also grounded.

[0010] In a specific possible implementation scheme, the AC-AC conversion circuit further includes an output current detection module; The metering chip is also connected to the output current detection module; the metering chip is used to detect the current value of the second alternating current output by the alternating current conversion module through the output current detection module, and output the current value to the MCU; Wherein, the output current detection module includes: a current transformer CT1, a resistor R11, a resistor R12, a resistor R13, a capacitor C2 and a capacitor C3; The input end of the current transformer CT1 is connected between the AC power conversion module and the load; the first output end of the current transformer CT1 is connected to the metering chip through the resistor R11, and the second output end of the current transformer CT1 is connected to the metering chip through the resistor R12; One end of the resistor R13 is connected to the first output end of the current transformer CT1 and the connection node of the resistor R11, and the other end of the resistor R13 is connected to the second output end of the current transformer CT1 and the connection node of the resistor R12; after the capacitor C2 and the capacitor C3 are connected in series, one end is connected to the connection node between the resistor R11 and the metering chip, and the other end is connected to the connection node between the resistor R12 and the metering chip; the intermediate connection node between the capacitor C2 and the capacitor C3 is also grounded.

[0011] In a specific implementation scheme, the AC-AC conversion circuit further includes a signal enhancement module; the signal enhancement module is connected between the MCU and the AC power conversion module, and is used to enhance the driving capability of the PWM control signal issued by the MCU; The signal enhancement module includes: a resistor R14, a resistor R15, a resistor R16, a resistor R17, a transistor Q4 and a transistor Q5; The first end of the resistor R14 is connected to the MCU, and the second end is connected to the driving end of the transistor Q4; the first end of the transistor Q4 is respectively connected to the first end of the resistor R16 and the first end of the transistor Q5, and the second end of the transistor Q4 is grounded; the control end of the transistor Q5 is connected to the first end of the resistor R15, and the second end of the resistor R15 and the second end of the resistor R16 are both connected to the power supply voltage VCC; the second end of the transistor Q5 is connected to the power supply voltage VIN through the resistor R17, and the second end of the transistor Q5 is also connected to the AC conversion module.

[0012] By adopting the above technical solution, since the high-level voltage of the PWM control signal output by the MCU is relatively small and the driving ability is relatively weak, a signal enhancement module is used to enhance the amplitude of the PWM control signal issued by the MCU through the cascade amplification effect of transistors Q4 and Q5, so that the AC power conversion module can respond to the control instructions of the MCU more reliably and effectively, thereby realizing a more accurate AC-AC conversion function.

[0013] In a specific implementation scheme, the AC-AC conversion circuit also includes a DC conversion module; the DC conversion module is used to convert the power supply voltage VIN into a power supply voltage VCC; wherein the power supply voltage VIN is DC12V, and the power supply voltage VCC is DC3.3V.

[0014] In a second aspect, the present application provides a converter, which adopts the following technical solution: the converter includes the AC-AC conversion circuit in the above-mentioned first aspect or any feasible implementation scheme of the first aspect.

[0015] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: The present application designs an AC voltage conversion module so that the AC voltage conversion module receives a first AC power and converts it into a second AC power to power a load, and uses an MCU to output a PWM control signal to the AC voltage conversion module to control the voltage of the output second AC power. In this way, AC-AC conversion can be directly realized. Compared with the traditional method of first converting AC power into DC power and then converting it into AC power, the energy loss of the system is reduced, the conversion efficiency is improved, and the circuit structure is easy to implement, which reduces the cost and is convenient for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the overall structure of the AC-AC conversion circuit in an embodiment of the present application; Figure 2 is a schematic diagram of a specific implementation of the AC power conversion module in the embodiment of the present application; Figure 3 is a schematic diagram of a specific implementation of the first alternating current detection module in the embodiment of the present application; Figure 4 It is a schematic diagram of a specific implementation of the output voltage detection module and the output current detection module in the embodiment of the present application; Figure 5 This is a schematic diagram of a specific implementation of the signal enhancement module in the embodiment of the present application; Figure 6 is a schematic diagram of a specific implementation of a direct current conversion module in an embodiment of the present application; Figure 7 It is a schematic diagram of the connection of the single-chip microcomputer and the peripheral minimum system circuit in the embodiment of the present application.

[0017] Description of reference numerals: 1. MCU; 2. AC power conversion module; 3. First AC power detection module; 4. Output voltage detection module; 5. Output current detection module; 6. Signal enhancement module; 7. DC power conversion module. DETAILED DESCRIPTION

[0018] In order to enable technicians in this field to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments.

[0019] In the description of the embodiments of the present application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. The terms "include", "comprises", "has" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0020] The embodiment of the present application provides an AC-AC conversion circuit, including an MCU1 and an AC power conversion module 2; the input end of the AC power conversion module 2 is connected to the MCU1, and the output end is connected to a load; The AC power conversion module 2 is used to receive the first AC power, and is also used to convert the first AC power into the second AC power based on the PWM control signal sent by the MCU1 and output it to the load; Among them, combined Figure 2 The AC power conversion module 2 includes an optical coupler OP1, a resistor R1, a resistor R2, a resistor R3, a diode MD1, a diode MD2, a diode MD3, a diode MD4, a switch tube Q1, and a switch tube Q2; the optical coupler OP1 is a bidirectional thyristor output optical coupler; The first input terminal of the optical coupler OP1 is connected to the power supply voltage VIN through the resistor R1, and the second input terminal is connected to the MCU1; The first output end of the optical coupler OP1 is respectively connected to the first end of the diode MD1, the first end of the resistor R2 and the driving end of the switch tube Q1; the first end of the first alternating current is respectively connected to the second end of the diode MD1, the second end of the resistor R2, the first end of the switch tube Q1 and the first end of the diode MD3; the second end of the switch tube Q1 is respectively connected to the second end of the diode MD3 and a power supply end of the load; The second output end of the optocoupler OP1 is respectively connected to the first end of the diode MD2, the first end of the resistor R3 and the driving end of the switch tube Q2; the second end of the first alternating current is respectively connected to the first end of the diode MD4, the first end of the switch tube Q2, the second end of the resistor R3 and the second end of the diode MD2; the second end of the switch tube Q2 is respectively connected to the second end of the diode MD4 and another power supply end of the load.

[0021] In a possible implementation, Figure 2 As shown, the first end of the diode MD1 and the first end of the diode MD2 are positive electrodes, and the first end of the diode MD3 and the first end of the diode MD4 are negative electrodes. The first end of the switch tube Q1 is the drain electrode and the second end is the source electrode; the first end of the switch tube Q2 is the drain electrode and the second end is the source electrode; the first end of the first alternating current is the L end and the second end is the N end; the two output ends of the alternating current conversion module 2 are the L end and the N end respectively; the two power supply ends of the load are the L end and the N end respectively, and the two output ends of the alternating current conversion module 2 and the two power supply ends of the load are connected correspondingly.

[0022] Preferably, the switch tube Q1 and the switch tube Q2 are CMOS field effect tubes with a withstand voltage of more than 600V, and the diode MD3 and the diode MD4 are fast transient diodes with a withstand voltage of up to 1000V.

[0023] The working process of the module is explained below: Resistors R2 and R3 are pull-up resistors. On the input side of the optocoupler OP1, MCU1 sends a PWM control signal to the input end of the optocoupler OP1, thereby controlling the on and off of the optocoupler OP1; At the output side of the optocoupler OP1, when the optocoupler OP1 is turned on and the first alternating current is in a positive half cycle, that is, the first end of the first alternating current outputs a forward current, the first end of the first alternating current, the resistor R2, the optocoupler OP1, the diode MD2 and the second end of the first alternating current form a current loop, thereby driving the switch tube Q1 to be turned on, so that the first end of the first alternating current, the switch tube Q1, the load, the diode MD4 and the second end of the first alternating current form a current loop, and a positive half cycle of the second alternating current is formed on the load; When the optocoupler OP1 is turned on and the first alternating current is in the negative half-cycle, that is, the second end of the first alternating current outputs a forward current, the second end of the first alternating current, the resistor R3, the optocoupler OP1, the diode MD1 and the first end of the first alternating current form a current loop, thereby driving the switch tube Q2 to be turned on, so that the second end of the first alternating current, the switch tube Q2, the load, the diode MD3 and the first end of the first alternating current form a current loop, forming a negative half-cycle of the second alternating current on the load.

[0024] Therefore, in this way, when the first alternating current is continuously input into the circuit, the second alternating current can be continuously provided to the load through the PWM signal output by the MCU1 and the conversion by the AC conversion module 2. It can be understood by those skilled in the art that the MCU1 can control the conduction time of the optical coupler OP1 by adjusting the duty cycle of the PWM control signal, thereby adjusting the voltage of the second alternating current, and those skilled in the art can determine the duty cycle of the PWM control signal according to their needs.

[0025] Through the design of the AC power conversion module 2, the AC power conversion module 2 receives the first AC power and converts it into the second AC power to power the load, and the MCU1 is used to output a PWM control signal to the AC power conversion module 2 to control the voltage of the output second AC power. Through such a design, AC-AC conversion can be directly realized. Compared with the traditional method of first converting AC power into DC power and then converting it into AC power, the energy loss of the system is reduced, the conversion efficiency is improved, and the circuit structure is easy to implement, which reduces the cost and is convenient for large-scale promotion and application. In addition, the optical coupler OP1 can also ensure the separation of strong and weak electricity, so as to achieve the purpose of weak electricity controlling strong electricity.

[0026] In one possible implementation, refer to Figure 1 , the AC-AC conversion circuit also includes a first alternating current detection module 3; The MCU1 is connected to the output end of the first alternating current detection module 3, and is used to detect the cycle of the first alternating current through the first alternating current detection module 3; Among them, combined Figure 3 , the first AC power detection module 3 includes: a resistor R4, a resistor R5, a resistor R6, a resistor R7, a diode MD5, an optical coupler OP2 and a transistor Q3; The first input end of the optical coupler OP2 is connected to the first end of the first alternating current through the resistor R4 and the resistor R5, and the second input end of the optical coupler OP2 is connected to the second end of the first alternating current; the diode MD5 is connected to the two input ends of the optical coupler OP2 respectively; The first output end of the optical coupler OP2 is connected to the driving end of the transistor Q3 and the first end of the resistor R6 respectively; the first end of the transistor Q3 is connected to the MCU1 and the first end of the resistor R7 respectively, and the second end of the resistor R6 and the second end of the resistor R7 are both connected to the power supply voltage VCC; the second end of the transistor Q3 is grounded; the second output end of the optical coupler OP2 is grounded.

[0027] Furthermore, the first end of the transistor Q3 is a collector, and the second end is an emitter.

[0028] The following is an explanation of the working process of this module: When the first alternating current is in a positive half cycle, that is, the first end of the first alternating current outputs a forward current, the first end of the first alternating current, the resistor R4, the resistor R5, the optical coupler OP2 and the second end of the first alternating current form a current loop, the optical coupler OP2 is turned on, thereby pulling down the voltage at the driving end of the transistor Q3, the transistor Q3 is not turned on, and the voltage at the node connecting the first alternating current detection module 3 and the MCU1 is at a high level; When the first alternating current is in a negative half cycle, that is, the second end of the first alternating current outputs a positive current, the optical coupler OP2 is not conducting, the transistor Q3 is conducting, and the voltage of the node connecting the first alternating current detection module 3 and the MCU1 is at a low level; MCU1 can obtain the corresponding square wave signal by continuously detecting the voltage at the output end of the first AC detection module 3, and then obtain the period, upper half period and lower half period of the first AC according to the time interval between two adjacent rising edges of the square wave signal.

[0029] Therefore, the first AC detection module 3 can output a square wave signal to MCU1 according to the first AC power. By continuously detecting the voltage at the output end of the first AC detection module 3, MCU1 can accurately obtain the time interval between two adjacent rising edges of the square wave signal, thereby obtaining the period of the first AC power.

[0030] In one possible implementation, continue to refer to Figure 1 , the AC-AC conversion circuit also includes an output voltage detection module 4 and a metering chip; The metering chip is connected to the output voltage detection module 4 and the MCU1 respectively; the metering chip is used to detect the voltage value of the second alternating current output by the alternating current conversion module 2 through the output voltage detection module 4, and output the voltage value to the MCU1; Among them, combined Figure 4 , the output voltage detection module 4 includes: a resistor R8, a resistor R9, a resistor R10, a voltage transformer PT1 and a capacitor C1; The first input end of the voltage transformer PT1 is connected to an output end of the AC power conversion module 2 outputting the second AC power through the resistor R8 and the resistor R9; the second input end of the voltage transformer PT1 is connected to another output end of the AC power conversion module 2 outputting the second AC power; The first output end of the voltage transformer PT1 is respectively connected to the first end of the resistor R10, the first end of the capacitor C1 and the metering chip; the second output end of the voltage transformer PT1 is respectively connected to the second end of the resistor R10 and the second end of the capacitor C1, and the second output end of the voltage transformer PT1 is also grounded.

[0031] The following is an explanation of the working process of this module: In the output voltage detection module 4, resistors R8 and R9 are used for voltage division, the voltage transformer PT1 is used for voltage isolation and conversion, the resistor R10 is a sampling resistor, and the capacitor C1 is used for filtering; therefore, the metering chip detects the voltage of the node connected to the output voltage detection module 4, and after calculation, the voltage value of the second alternating current can be obtained, and then communicated with MCU1 to output the voltage value to MCU1.

[0032] In one possible implementation, continue to refer to Figure 1 , the AC-AC conversion circuit also includes an output current detection module 5; The metering chip is also connected to the output current detection module 5; the metering chip is used to detect the current value of the second alternating current output by the alternating current conversion module 2 through the output current detection module 5, and output the current value to the MCU1; Among them, combined Figure 4 , the output current detection module 5 includes: a current transformer CT1, a resistor R11, a resistor R12, a resistor R13, a capacitor C2 and a capacitor C3; The input end of the current transformer CT1 is connected between the AC power conversion module 2 and the load; specifically, the first input end of the current transformer CT1 is connected to an output end of the AC power conversion module 2 outputting the second AC power; the second input end of the current transformer CT1 is connected to a power supply end of the load; The first output end of the current transformer CT1 is connected to the metering chip through the resistor R11, and the second output end of the current transformer CT1 is connected to the metering chip through the resistor R12; One end of the resistor R13 is connected to the first output end of the current transformer CT1 and the connection node of the resistor R11, and the other end of the resistor R13 is connected to the second output end of the current transformer CT1 and the connection node of the resistor R12; after the capacitor C2 and the capacitor C3 are connected in series, one end is connected to the connection node between the resistor R11 and the metering chip, and the other end is connected to the connection node between the resistor R12 and the metering chip; the intermediate connection node between the capacitor C2 and the capacitor C3 is also grounded.

[0033] The following is an explanation of the working process of this module: In the output current detection module 5, the current transformer CT1 is used to generate a current signal proportional to the input current at its output end, the resistor R13 is a sampling resistor, and the resistor R11, the resistor R12, the capacitor C2 and the capacitor C3 constitute an RC filter circuit. After the metering chip measures the current value, it passes it to the MCU1.

[0034] Furthermore, the model of the metering chip is HLW8110, and the metering chip communicates with MCU1 through the USART communication port to form a feedback path of the second alternating current, so that MCU1 can monitor the current and voltage of the second alternating current in real time, thereby adjusting the duty cycle of the PWM control signal output to the alternating current conversion module 2, realizing real-time adjustment of voltage conversion, and improving the stability of the second alternating current. Of course, MCU1 can also display, control or other purposes according to the voltage and current values ​​of the second alternating current, and this application does not make specific limitations on this.

[0035] In one possible implementation, refer to Figure 1 , the AC-AC conversion circuit also includes a signal enhancement module 6; the signal enhancement module 6 is connected between the MCU1 and the AC power conversion module 2, and is used to enhance the driving ability of the PWM control signal issued by the MCU1; Among them, combined Figure 5 , the signal enhancement module 6 includes: a resistor R14, a resistor R15, a resistor R16, a resistor R17, a transistor Q4 and a transistor Q5; The first end of the resistor R14 is connected to the MCU1, and the second end is connected to the driving end of the transistor Q4; the first end of the transistor Q4 is respectively connected to the first end of the resistor R16 and the first end of the transistor Q5, and the second end of the transistor Q4 is grounded; the control end of the transistor Q5 is connected to the first end of the resistor R15, and the second end of the resistor R15 and the second end of the resistor R16 are both connected to the power supply voltage VCC; the second end of the transistor Q5 is connected to the power supply voltage VIN through the resistor R17, and the second end of the transistor Q5 is also connected to the AC conversion module 2.

[0036] Furthermore, the first end of the transistor Q4 is a collector, and the second end is an emitter; the first end of the transistor Q5 is an emitter, and the second end is a collector.

[0037] The following is an explanation of the working process of this module: In the signal enhancement module 6, resistor R14 is used for current limiting. When the PWM control signal output by MCU1 is at a high level, transistor Q4 and transistor Q5 are turned on, and the voltage at the second end of transistor Q5 is pulled down, and the output end of the signal enhancement module 6 is at a low level; when the PWM control signal output by MCU1 is at a low level, transistor Q4 and transistor Q5 are not turned on, and the power supply voltage VIN passes through resistor R17, so that the output end of the signal enhancement module 6 is at a high level, and the output voltage value is associated with the power supply voltage VIN, thereby realizing the amplification of the PWM control signal.

[0038] Since the high-level voltage of the PWM control signal output by MCU1 is relatively small and the driving capability is relatively weak, a signal enhancement module 6 is used to enhance the amplitude of the PWM control signal issued by MCU1 through the cascade amplification effect of transistors Q4 and Q5, so that the AC power conversion module 2 can respond to the control instructions of MCU1 more reliably and effectively, thereby realizing a more accurate AC-AC conversion function.

[0039] In a possible implementation, the AC-AC conversion circuit further includes a DC conversion module 7, wherein the DC conversion module 7 is used to convert a power supply voltage VIN into a power supply voltage VCC, wherein the power supply voltage VIN is DC12V, and the power supply voltage VCC is DC3.3V.

[0040] In combination with the foregoing, the power supply voltage VIN is used to drive the optocoupler OP1 in the AC power conversion module 2, and is also used to provide power support for the signal enhancement module 6; the power supply voltage VCC is used to provide power support for the first AC power detection module 3, the signal enhancement module 6, and is also used to provide power for the normal operation of the metering chip and MCU1.

[0041] like Figure 6 As shown in FIG. 1 , a specific implementation of the DC power conversion module 7 is shown, which uses a voltage conversion chip to realize the conversion of DC voltage. The model of the voltage conversion chip is MP1470. Figure 6The peripheral circuits involved in the voltage conversion chip are shown, specifically including: the VIN pin of the voltage conversion chip is connected to the power supply voltage VIN, the EN pin is connected to the power supply voltage VIN through a resistor R18, the FB pin is connected in series with a resistor R20, a resistor R21, and a capacitor C5 and then grounded, and the middle node of the resistor R20 and the resistor R21 is connected in series with a resistor R19 and then grounded, and a capacitor E8 is also connected in parallel at both ends of the capacitor C5; the BSP pin of the voltage conversion chip outputs the power supply voltage VCC after being connected in series with a capacitor C4 and an inductor L1; the SW pin of the voltage conversion chip is connected to the middle node of the capacitor C4 and the inductor L1.

[0042] In a possible implementation, MCU1 includes a single chip microcomputer of type STM32F103C8T6, such as Figure 7 As shown, this is a schematic diagram of the connection of the microcontroller and the peripheral minimum system circuit.

[0043] An embodiment of the present application provides a converter, comprising the above-mentioned AC-AC conversion circuit.

[0044] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. An AC-AC conversion circuit, characterized in that: It comprises an MCU (1) and an alternating current conversion module (2); the input end of the alternating current conversion module (2) is connected to the MCU (1), and the output end is connected to a load; The AC power conversion module (2) is used to receive the first AC power, and is also used to convert the first AC power into the second AC power based on the PWM control signal sent by the MCU (1) and output the second AC power to the load; The AC power conversion module (2) comprises an optical coupler OP1, a resistor R1, a resistor R2, a resistor R3, a diode MD1, a diode MD2, a diode MD3, a diode MD4, a switch tube Q1, and a switch tube Q2; the optical coupler OP1 is a bidirectional thyristor output optical coupler; The first input terminal of the optical coupler OP1 is connected to the power supply voltage VIN through the resistor R1, and the second input terminal is connected to the MCU (1); The first output end of the optical coupler OP1 is respectively connected to the first end of the diode MD1, the first end of the resistor R2 and the driving end of the switch tube Q1; the first end of the first alternating current is respectively connected to the second end of the diode MD1, the second end of the resistor R2, the first end of the switch tube Q1 and the first end of the diode MD3; the second end of the switch tube Q1 is respectively connected to the second end of the diode MD3 and a power supply end of the load; The second output end of the optocoupler OP1 is respectively connected to the first end of the diode MD2, the first end of the resistor R3 and the driving end of the switch tube Q2; the second end of the first alternating current is respectively connected to the first end of the diode MD4, the first end of the switch tube Q2, the second end of the resistor R3 and the second end of the diode MD2; the second end of the switch tube Q2 is respectively connected to the second end of the diode MD4 and another power supply end of the load.

2. The AC-AC conversion circuit according to claim 1, characterized in that: The MCU (1) is used to control the on and off of the optical coupler OP1 by sending a PWM control signal to the input end of the optical coupler OP1; When the optocoupler OP1 is turned on, and the first end of the first alternating current outputs a forward current, the first end of the first alternating current, the resistor R2, the optocoupler OP1, the diode MD2, and the second end of the first alternating current form a current loop, driving the switch tube Q1 to be turned on, so that the first end of the first alternating current, the switch tube Q1, the load, the diode MD4, and the second end of the first alternating current form a current loop, forming a positive half cycle of the second alternating current on the load; When the optocoupler OP1 is turned on and the second end of the first alternating current outputs a forward current, the second end of the first alternating current, the resistor R3, the optocoupler OP1, the diode MD1 and the first end of the first alternating current form a current loop, driving the switch tube Q2 to be turned on, so that the second end of the first alternating current, the switch tube Q2, the load, the diode MD3 and the first end of the first alternating current form a current loop, forming a negative half cycle of the second alternating current on the load.

3. The AC-AC conversion circuit according to claim 1, characterized in that: It also includes a first alternating current detection module (3); The MCU (1) is connected to the output end of the first alternating current detection module (3), and is used to detect the cycle of the first alternating current through the first alternating current detection module (3); The first alternating current detection module (3) comprises: a resistor R4, a resistor R5, a resistor R6, a resistor R7, a diode MD5, an optical coupler OP2 and a transistor Q3; The first input end of the optical coupler OP2 is connected to the first end of the first alternating current through the resistor R4 and the resistor R5, and the second input end of the optical coupler OP2 is connected to the second end of the first alternating current; the diode MD5 is connected to the two input ends of the optical coupler OP2 respectively; The first output end of the optical coupler OP2 is connected to the driving end of the transistor Q3 and the first end of the resistor R6 respectively; the first end of the transistor Q3 is connected to the MCU (1) and the first end of the resistor R7 respectively, and the second end of the resistor R6 and the second end of the resistor R7 are both connected to the power supply voltage VCC; the second end of the transistor Q3 is grounded; and the second output end of the optical coupler OP2 is grounded.

4. The AC-AC conversion circuit according to claim 1, characterized in that: It also includes an output voltage detection module (4) and a metering chip; The metering chip is connected to the output voltage detection module (4) and the MCU (1) respectively; the metering chip is used to detect the voltage value of the second alternating current output by the alternating current conversion module (2) through the output voltage detection module (4), and output the voltage value to the MCU (1); The output voltage detection module (4) comprises: a resistor R8, a resistor R9, a resistor R10, a voltage transformer PT1 and a capacitor C1; The first input end of the voltage transformer PT1 is connected to an output end of the AC power conversion module (2) outputting the second AC power through the resistor R8 and the resistor R9; the second input end of the voltage transformer PT1 is connected to another output end of the AC power conversion module (2) outputting the second AC power; The first output end of the voltage transformer PT1 is respectively connected to the first end of the resistor R10, the first end of the capacitor C1 and the metering chip; the second output end of the voltage transformer PT1 is respectively connected to the second end of the resistor R10 and the second end of the capacitor C1, and the second output end of the voltage transformer PT1 is also grounded.

5. The AC-AC conversion circuit according to claim 4, characterized in that: It also includes an output current detection module (5); The metering chip is also connected to the output current detection module (5); the metering chip is used to detect the current value of the second alternating current output by the alternating current conversion module (2) through the output current detection module (5), and output the current value to the MCU (1); The output current detection module (5) comprises: a current transformer CT1, a resistor R11, a resistor R12, a resistor R13, a capacitor C2 and a capacitor C3; The input end of the current transformer CT1 is connected between the AC power conversion module (2) and the load; the first output end of the current transformer CT1 is connected to the metering chip through the resistor R11, and the second output end of the current transformer CT1 is connected to the metering chip through the resistor R12; One end of the resistor R13 is connected to the first output end of the current transformer CT1 and the connection node of the resistor R11, and the other end of the resistor R13 is connected to the second output end of the current transformer CT1 and the connection node of the resistor R12; after the capacitor C2 and the capacitor C3 are connected in series, one end is connected to the connection node between the resistor R11 and the metering chip, and the other end is connected to the connection node between the resistor R12 and the metering chip; the intermediate connection node between the capacitor C2 and the capacitor C3 is also grounded.

6. The AC-AC conversion circuit according to claim 1, characterized in that: It also includes a signal enhancement module (6); the signal enhancement module (6) is connected between the MCU (1) and the AC power conversion module (2) and is used to enhance the driving capability of the PWM control signal sent by the MCU (1); The signal enhancement module (6) includes: a resistor R14, a resistor R15, a resistor R16, a resistor R17, a transistor Q4 and a transistor Q5; The first end of the resistor R14 is connected to the MCU (1), and the second end is connected to the driving end of the transistor Q4; the first end of the transistor Q4 is respectively connected to the first end of the resistor R16 and the first end of the transistor Q5, and the second end of the transistor Q4 is grounded; the control end of the transistor Q5 is connected to the first end of the resistor R15, and the second end of the resistor R15 and the second end of the resistor R16 are both connected to the power supply voltage VCC; the second end of the transistor Q5 is connected to the power supply voltage VIN through the resistor R17, and the second end of the transistor Q5 is also connected to the AC conversion module (2).

7. The AC-AC conversion circuit according to claim 1, characterized in that: It also includes a direct current conversion module (7); the direct current conversion module (7) is used to convert a power supply voltage VIN into a power supply voltage VCC; wherein the power supply voltage VIN is DC12V, and the power supply voltage VCC is DC3.3V.

8. A converter, characterized in that: The AC-AC conversion circuit comprises the AC-AC conversion circuit according to any one of claims 1 to 7.

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