A bidirectional AC voltage conversion circuit

Abstract

A bidirectional AC voltage conversion circuit comprises an input terminal CN1, wherein the input terminal CN1 is connected to a common mode filter TX1, and one end of the common mode filter TX1 is provided with an endpoint A and an endpoint B, wherein the endpoint A is connected to the source of a MOS tube M1, the gate of the MOS tube M1 is connected to a control signal of a control circuit, the drain of the MOS tube M1 is connected to one end of a common mode filter TX2 through an endpoint C, and the other end of the common mode filter TX2 is connected to an output terminal CN2; the endpoint A is also connected to the drain of the MOS tube M2, the source of which is grounded, and the gate is connected to the control signal of the control circuit; the endpoint B is also connected to the drain of the MOS tube M3, the source of which is grounded, and the gate is connected to the control signal of the control circuit; the endpoint B is also connected to the source of the MOS tube M4, the drain of which is connected to one end of the common mode filter TX2 through an endpoint D, and the gate is connected to the control signal of the control circuit.

Description

Technical Field

[0001] The invention relates to the field of LED power supplies, and in particular to a bidirectional AC voltage conversion circuit. Background Art

[0002] There is a considerable market demand for AC voltage regulators, AC voltage stabilizers, and AC voltage matching converters. In particular, there are multiple global voltage standards, and electrical products are basically circulated around the world. Travelers often face the situation that the voltage specifications of the purchased electrical appliances do not meet the current grid voltage specifications, such as a common scenario: using 110V electrical appliances in a 220V environment. An AC voltage converter is needed to complete the matching.

[0003] At present, the mainstream of such products is to use power frequency common mode filter for voltage transformation. A 1KW voltage converter weighs two or three kilograms, so it is large in size, medium in weight, inconvenient to carry and high in cost. The overload protection is not flexible, and most of them only have overcurrent fuse. Summary of the invention

[0004] In order to solve the above problems, the present technical solution provides a bidirectional AC voltage conversion circuit.

[0005] To achieve the above purpose, the technical solution is as follows:

[0006] A bidirectional AC voltage conversion circuit comprises an input terminal CN1, the input terminal CN1 is connected to a common mode filter TX1, one end of the common mode filter TX1 is provided with an end point A and an end point B, wherein the end point A is connected to a source of a MOS tube M1, the gate of the MOS tube M1 is connected to a control signal of a control circuit, the drain of the MOS tube M1 is connected to one end of a common mode filter TX2 via an end point C, and the other end of the common mode filter TX2 is connected to an output terminal CN2;

[0007] The terminal A is also connected to the drain of the MOS tube M2, the source of which is grounded, and the gate of which is connected to the control signal of the control circuit;

[0008] The terminal B is also connected to the drain of the MOS tube M3, the source of which is grounded, and the gate of which is connected to the control signal of the control circuit;

[0009] The terminal B is also connected to the source of the MOS tube M4, the drain of which is connected to one end of the common mode filter TX2 through the terminal D, and the gate is connected to the control signal of the control circuit.

[0010] In some embodiments, an inductor L1 is provided between the endpoint A and the MOS transistor M1, an inductor L2 is provided between the endpoint B and the MOS transistor M3, an inductor L3 is provided between the endpoint C and the common mode filter TX2, and an inductor L4 is provided between the endpoint D and the common mode filter TX2.

[0011] In some embodiments, a sampling resistor RCS1 is disposed at the source of the MOS transistor M2 , and a sampling resistor RCS2 is disposed at the source of the MOS transistor M3 .

[0012] In some embodiments, a resistor R1 is provided at the gate of the MOS transistor M1, and a resistor R5 is provided between the gate and the source of the MOS transistor M1;

[0013] A resistor R2 is provided at the gate of the MOS tube M2, and a resistor R6 is provided between the gate and the source of the MOS tube M2;

[0014] A resistor R3 is provided at the gate of the MOS tube M3, and a resistor R7 is provided between the gate and the source of the MOS tube M3;

[0015] A resistor R4 is disposed at the gate of the MOS transistor M4 , and a resistor R8 is disposed between the gate and the source of the MOS transistor M4 .

[0016] In some embodiments, a fuse F1 is provided at the L phase end of the input terminal CN1, and a capacitor CX1 is provided between the L phase end and the N phase end;

[0017] The L-phase end of the output terminal CN2 is provided with a fuse F2, and a capacitor CX5 is provided between the L-phase end and the N-phase end.

[0018] In some embodiments, a capacitor CX2 is provided between the endpoint A and the endpoint B.

[0019] In some embodiments, a capacitor CX3 is provided between the endpoint C and the endpoint D.

[0020] In some embodiments, a capacitor CX4 is provided between two ends of the common mode filter TX2.

[0021] The beneficial effects of this application are:

[0022] The present application uses a high-frequency energy conversion method to replace the industrial frequency common-mode filter, and uses a digital control method to achieve more complete overload protection, and realizes the functions of voltage stabilization output and power limitation through closed-loop control. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for describing the embodiments are briefly introduced below.

[0024] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0025] Figure 2 It is a schematic diagram of the working waveform of the boost positive half cycle shown by the simulation waveform of an embodiment of the present invention;

[0026] Figure 3 It is a schematic diagram of the working waveform of the positive half cycle of the step-down shown by the simulation waveform of an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] Please refer to Figure 1-3 As shown, a bidirectional AC voltage conversion circuit comprises an input terminal CN1, the input terminal CN1 is connected to a common mode filter TX1, one end of the common mode filter TX1 is provided with an end point A and an end point B, wherein the end point A is connected to a source of a MOS tube M1, a gate of the MOS tube M1 is connected to a control signal of a control circuit, a drain of the MOS tube M1 is connected to one end of a common mode filter TX2 via an end point C, and the other end of the common mode filter TX2 is connected to an output terminal CN2;

[0029] The terminal A is also connected to the drain of the MOS tube M2, the source of which is grounded, and the gate of which is connected to the control signal of the control circuit;

[0030] The terminal B is also connected to the drain of the MOS tube M3, the source of which is grounded, and the gate of which is connected to the control signal of the control circuit;

[0031] The terminal B is also connected to the source of the MOS tube M4, the drain of which is connected to one end of the common mode filter TX2 through the terminal D, and the gate is connected to the control signal of the control circuit.

[0032] Furthermore, an inductor L1 is provided between the endpoint A and the MOS tube M1, an inductor L2 is provided between the endpoint B and the MOS tube M3, an inductor L3 is provided between the endpoint C and the common mode filter TX2, and an inductor L4 is provided between the endpoint D and the common mode filter TX2.

[0033] Furthermore, a sampling resistor RCS1 is provided at the source of the MOS transistor M2 , and a sampling resistor RCS2 is provided at the source of the MOS transistor M3 .

[0034] Furthermore, a resistor R1 is provided at the gate of the MOS tube M1, and a resistor R5 is provided between the gate and the source of the MOS tube M1;

[0035] A resistor R2 is provided at the gate of the MOS tube M2, and a resistor R6 is provided between the gate and the source of the MOS tube M2;

[0036] A resistor R3 is provided at the gate of the MOS tube M3, and a resistor R7 is provided between the gate and the source of the MOS tube M3;

[0037] A resistor R4 is disposed at the gate of the MOS transistor M4 , and a resistor R8 is disposed between the gate and the source of the MOS transistor M4 .

[0038] Furthermore, a fuse F1 is provided at the L phase end of the input terminal CN1, and a capacitor CX1 is provided between the L phase end and the N phase end;

[0039] The L-phase end of the output terminal CN2 is provided with a fuse F2, and a capacitor CX5 is provided between the L-phase end and the N-phase end.

[0040] Furthermore, a capacitor CX2 is provided between the endpoint A and the endpoint B.

[0041] Furthermore, a capacitor CX3 is provided between the endpoint C and the endpoint D.

[0042] Furthermore, a capacitor CX4 is provided between two ends of the common mode filter TX2.

[0043] refer to Figure 1 The main structure of the circuit of the present invention is an H-bridge composed of four MOS tubes. The left and right half bridges have equal functions. The left side is the low-voltage side. The AC voltage on the low-voltage side is connected to the midpoint of the left and right half bridge arms through the filter circuit. The right side is the high-voltage side. The high-voltage side is connected to the drain of the top upper tube of the left and right bridge arms through the filter circuit. This circuit has a bidirectional conversion function. If a slightly lower AC voltage is input from the left side, it can be converted to a relatively high-voltage AC voltage from the right output. Conversely, if a relatively high AC voltage is input from the right side, it can be converted to a relatively low AC voltage from the left output.

[0044] refer to Figure 2When CN1 inputs AC voltage, and its polarity is positive at the top and negative at the bottom, the control circuit determines it as a positive half-cycle of the power frequency. The control logic of this cycle is that the right bridge arm M3 and M4 are turned on at the same time, the left bridge arm works in the BOOST modulation state, the lower tube M2 is modulated by PWM, M1 is turned on for freewheeling when M2 is turned off, and the voltage after BOOST boost is output from the drain of M1 according to the duty cycle relationship. Under normal circumstances, the power frequency is 50-60HZ, the positive or negative half-cycle of the power frequency is 10mS, and the PWM modulation frequency is 20-120kHz. If the PWM modulation duty cycle is fixed at 50%, after the entire positive half-cycle of the power frequency ends, a sine positive half-cycle with an amplitude of the input voltage amplitude*2 will be obtained at both ends of the capacitor CX3, and the polarity is C positive and D negative. When CN1 inputs AC voltage, and its polarity is negative at the top and positive at the bottom, the control circuit determines that it is a negative half-cycle of the power frequency. The control logic of this cycle is that the left bridge arm M1 and M2 are turned on at the same time, and the right bridge arm works in the BOOST modulation state. The lower tube M3 is switched through PWM modulation, and M4 is turned on for freewheeling when M3 is turned off. The voltage after BOOST boost is output from the drain of M4 according to the duty cycle relationship. Similarly, after the negative half-cycle of the power frequency ends, a sinusoidal negative half-cycle with an amplitude of the input voltage amplitude * 2 will be obtained at both ends of the capacitor CX3, and the polarity is D positive and C negative. Finally, the voltage at both ends of the CX3 capacitor is coupled to the output terminal CN2 through L3, L4, CX4, TX2, CX5, and F2 to complete the boost process.

[0045] refer to Figure 3 When CN2 is connected to an AC voltage, and its polarity is positive at the top and negative at the bottom, the control circuit determines that it is a positive half-cycle of the power frequency. The control logic of this cycle is that the right bridge arms M3 and M4 are turned on at the same time, and the left bridge arm works in the BUCK modulation state. The upper tube M1 is modulated by PWM, and the lower tube M2 is turned on for freewheeling when M1 is turned off. The BUCK switch generates a high-frequency modulation waveform between the midpoint of the left bridge arm and the grounded midpoint of the right bridge arm. The energy is output from CX2, and the output voltage is A positive and B negative. The amplitude is proportional to the duty cycle of M1. When CN2 is connected to an AC voltage, and its polarity is negative on the top and positive on the bottom, the control circuit determines that it is a negative half-cycle of the power frequency. The control logic of this cycle is that the left bridge arm M1 and M2 are turned on at the same time, and the right bridge arm works in the BUCK modulation state. The upper tube M4 is modulated by PWM, and the lower tube M3 is turned on when M4 is turned off. The BUCK switch generates a high-frequency modulation waveform between the grounded midpoint of the left bridge arm and the midpoint of the right bridge arm. Energy is output from CX2, and the output voltage is B positive and A negative, and the amplitude is proportional to the duty cycle of M4. At this point, the input AC voltage of CN2 is output from CX2 to CN1 through the filter network loop TX1 and CX1 after the circuit step-down process.

[0046] In addition, this circuit adopts digital control method, which can achieve functions such as voltage regulation output, constant power output and overload protection by sampling current from RCS1 and RCS2, combined with simple input and output voltage sampling, and closed-loop control. Because the bulky power frequency common mode filter is abandoned, this type of finished product has the characteristics of small size, light weight, high power density, and relatively low cost.

[0047] The above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application. Other principles and basic structures that are the same or similar to those of the present application are within the protection scope of the present application.

Claims

1. A bidirectional AC voltage conversion circuit, characterized in that: It includes an input terminal CN1, the input terminal CN1 is connected to a common mode filter TX1, one end of the common mode filter TX1 is provided with an end point A and an end point B, wherein the end point A is connected to the source of the MOS tube M1, the gate of the MOS tube M1 is connected to the control signal of the control circuit, the drain of the MOS tube M1 is connected to one end of the common mode filter TX2 through the end point C, and the other end of the common mode filter TX2 is connected to the output terminal CN2; The terminal A is also connected to the drain of the MOS tube M2, the source of which is grounded, and the gate of which is connected to the control signal of the control circuit; The terminal B is also connected to the drain of the MOS tube M3, the source of which is grounded, and the gate of which is connected to the control signal of the control circuit; The terminal B is also connected to the source of the MOS tube M4, the drain of which is connected to one end of the common mode filter TX2 through the terminal D, and the gate is connected to the control signal of the control circuit.

2. The bidirectional AC voltage conversion circuit according to claim 1, characterized in that: An inductor L1 is provided between the endpoint A and the MOS transistor M1, an inductor L2 is provided between the endpoint B and the MOS transistor M3, an inductor L3 is provided between the endpoint C and the common mode filter TX2, and an inductor L4 is provided between the endpoint D and the common mode filter TX2.

3. The bidirectional AC voltage conversion circuit according to claim 2, characterized in that: The source of the MOS tube M2 is provided with a sampling resistor RCS1, and the source of the MOS tube M3 is provided with a sampling resistor RCS2.

4. The bidirectional AC voltage conversion circuit according to claim 1, characterized in that: A resistor R1 is provided at the gate of the MOS tube M1, and a resistor R5 is provided between the gate and the source of the MOS tube M1; A resistor R2 is provided at the gate of the MOS tube M2, and a resistor R6 is provided between the gate and the source of the MOS tube M2; A resistor R3 is provided at the gate of the MOS tube M3, and a resistor R7 is provided between the gate and the source of the MOS tube M3; A resistor R4 is disposed at the gate of the MOS transistor M4 , and a resistor R8 is disposed between the gate and the source of the MOS transistor M4 .

5. The bidirectional AC voltage conversion circuit according to claim 1, characterized in that: The L-phase end of the input terminal CN1 is provided with a fuse F1, and a capacitor CX1 is provided between the L-phase end and the N-phase end; The L-phase end of the output terminal CN2 is provided with a fuse F2, and a capacitor CX5 is provided between the L-phase end and the N-phase end.

6. The bidirectional AC voltage conversion circuit according to claim 1, characterized in that: A capacitor CX2 is provided between the endpoint A and the endpoint B.

7. The bidirectional AC voltage conversion circuit according to claim 1, characterized in that: A capacitor CX3 is provided between the endpoint C and the endpoint D.

8. The bidirectional AC voltage conversion circuit according to claim 1, characterized in that: A capacitor CX4 is provided between two ends of the common mode filter TX2.

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