TWI902613B - Ac-dc conversion circuit and operating method thereof - Google Patents

Abstract

An AC-DC conversion circuit includes a power measurement circuit, a control circuit, and three bridge arm circuits. Each bridge arm circuit includes a plurality of switches. The power measurement circuit is used to measure at least one of an input power and an output power to generate a power measurement value. When the power measurement value is less than a power threshold value, the control circuit controls the switches of the three bridge arm circuits to set the three bridge arm circuits to operate in a light load mode. When the power measurement value is greater than the power threshold value, the control circuit controls the switches of the three bridge arm circuits to set the three bridge arm circuits to operate in a heavy load mode.

Description

AC-DC conversion circuit and its operation method

This disclosure relates to a conversion circuit and its operation method, particularly an AC-DC conversion circuit and its operation method.

Currently, various pulse width modulation (PWM) modes are available for controlling power conversion devices with related technologies (e.g., active neutral point clamped (ANPC) power conversion devices). The power loss of these PWM modes varies at different power levels; some PWM modes exhibit lower power loss below a certain power level but higher power loss at power levels greater than or equal to that level, while others show the opposite.

In conclusion, current pulse width modulation (PWM) modes are not ideal, resulting in insufficient overall power loss for power conversion devices that utilize a single PWM mode to control power at all power levels.

To address the aforementioned problems, the purpose of this disclosure is to provide an AC-DC conversion circuit.

To address the aforementioned problems, another objective of this disclosure is to provide an AC-DC conversion circuit operation method.

To achieve the aforementioned objectives of this disclosure, the disclosed AC-DC conversion circuit for generating a DC output voltage based on a three-phase AC input power supply includes: a power measurement circuit for measuring at least one of an input power and an output power to generate a power measurement value; a control circuit coupled to the power measurement circuit; and three bridge arm circuits, each of which includes: a first switch, comprising a control terminal coupled to the control circuit and a first terminal coupled to a first capacitor. A first output terminal and a second terminal; a second switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch, and a second terminal coupled to a first input inductor; a third switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the second switch, the first input inductor, and a second terminal; a fourth switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the third switch, and a second terminal connected to a second capacitor. Coupled to the first output terminal; a fifth switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch and the first terminal of the second switch, and a second terminal coupled to the first output terminal; and a sixth switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the fifth switch and the first output terminal, and a second terminal coupled to the second terminal of the third switch and the first terminal of the fourth switch, wherein when the power measurement value is less than a power threshold. The control circuit configures the three bridge arm circuits to operate in a light-load mode: during a first positive half-cycle signal of a first single-phase AC power supply of the three-phase AC input power supply, the control circuit configures the second switch coupled to the first bridge arm circuit of the first single-phase AC power supply to be turned on, and configures the third switch and the fourth switch to be turned off; during a charging mode of the first positive half-cycle signal, the control circuit configures the first switch and the sixth switch of the first bridge arm circuit to be turned off, and configures the fifth switch to be turned on. In a discharge mode of the first positive half-cycle signal, the control circuit sets the first switch and the sixth switch of the first bridge arm circuit to be turned on, and sets the fifth switch to be turned off; in a first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch and the second switch of the first bridge arm circuit to be turned off, and sets the third switch to be turned on; in a charging mode of the first negative half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be turned off, and sets the fifth switch to be turned off. The fourth and fifth switches are de-conducting, and the sixth switch is turned on; in a discharge mode of the first negative half-cycle signal, the control circuit turns on the fourth and fifth switches of the first bridge arm circuit, and turns off the sixth switch; wherein when the power measurement value is greater than the power threshold, the control circuit sets the three bridge arm circuits to operate in a heavy load mode; in a second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first bridge arm circuit... The second and sixth switches are turned on, and the fourth switch is turned off; in a charging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be off, and sets the third and fifth switches to be on; in a discharging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be on, and sets the third and fifth switches to be off; in a first single-phase AC power supply of the three-phase AC input power supply... In the two negative half-cycle signals, the control circuit sets the first switch of the first bridge arm circuit to be off, and sets the third switch and the fifth switch to be on; in a charging mode of the second negative half-cycle signal, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be on, and sets the fourth switch to be off; in a discharging mode of the second negative half-cycle signal, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be off, and sets the fourth switch to be on.

To achieve another objective disclosed herein, the AC-DC conversion circuit operation method disclosed herein uses an AC-DC conversion circuit to generate a DC output voltage based on a three-phase AC input power supply. The AC-DC conversion circuit includes a power measurement circuit, a control circuit, and three bridge arm circuits. The control circuit is coupled to the power measurement circuit. Each bridge arm circuit includes: a first switch, comprising a control terminal coupled to the control circuit, a first terminal coupled to a first output terminal via a first capacitor, and a second terminal; a third... A second switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch, and a second terminal coupled to a first input inductor; a third switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the second switch and the first input inductor, and a second terminal; a fourth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the third switch, and a second terminal coupled to the first output terminal via a second capacitor; a fifth switch includes... The circuit includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch and the first terminal of the second switch, and a second terminal coupled to the first output terminal; and a sixth switch, comprising a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the fifth switch and the first output terminal, and a second terminal coupled to the second terminal of the third switch and the first terminal of the fourth switch. The AC-DC conversion circuit operation method includes: the power measurement circuit measuring an input power and an output power. At least one of them generates a power measurement value; when the power measurement value is less than a power threshold, the control circuit sets the three bridge arm circuits to operate in a light-load mode: during a first positive half-cycle signal of a first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the second switch of a first bridge arm circuit coupled to the first single-phase AC power supply to be turned on, and sets the third switch and the fourth switch to be turned off; during a charging mode of the first positive half-cycle signal, the control circuit sets the first bridge arm circuit to operate in a light-load mode. In a discharge mode of the first positive half-cycle signal, the control circuit sets the first switch and the sixth switch of the first bridge arm circuit to conduct, and sets the fifth switch to not conduct; in a first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch and the second switch of the first bridge arm circuit to not conduct, and sets the third switch to conduct; in a charging mode of the first negative half-cycle signal... The control circuit sets the fourth and fifth switches of the first bridge arm circuit to be off, and sets the sixth switch to be on; in a discharge mode of the first negative half-cycle signal, the control circuit sets the fourth and fifth switches of the first bridge arm circuit to be on, and sets the sixth switch to be off; when the power measurement value is greater than the power threshold, the control circuit sets the three bridge arm circuits to operate in a heavy load mode; in a second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control... The circuit configures the second and sixth switches of the first bridge arm circuit to be turned on, and the fourth switch to be turned off; in a charging mode of the second positive half-cycle signal, the control circuit configures the first switch of the first bridge arm circuit to be turned off, and the third and fifth switches to be turned on; in a discharging mode of the second positive half-cycle signal, the control circuit configures the first switch of the first bridge arm circuit to be turned on, and the third and fifth switches to be turned off; in the first single-phase AC input of the three-phase AC power supply... In a second negative half-cycle signal of the current power supply, the control circuit sets the first switch of the first bridge arm circuit to be off, and sets the third switch and the fifth switch to be on; in a charging mode of the second negative half-cycle signal, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be on, and sets the fourth switch to be off; in a discharging mode of the second negative half-cycle signal, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be off, and sets the fourth switch to be on.

The benefit of this disclosure is to reduce the overall power loss of AC-DC conversion circuits.

To further understand the techniques, methods, and effects of this disclosure and to achieve the intended purpose of this disclosure, please refer to the following detailed description and figures; in addition, the purpose, characteristics, and features of this disclosure can be understood more deeply and specifically; however, the figures are provided for reference and description only and are not intended to limit the scope of this disclosure.

This disclosure provides numerous specific details to offer a comprehensive understanding of the embodiments thereof; however, those skilled in the art will understand that this disclosure may be practiced without one or more of these specific details; in other cases, well-known details have not been shown or described to avoid obscuring the features of this disclosure. The technical content and detailed description of this disclosure are as follows, illustrated with accompanying figures.

Please refer to Figure 1, which is a circuit block diagram of a first embodiment of the AC-DC converter 10 disclosed herein. The AC-DC converter 10 disclosed herein is used to generate a DC output voltage 22 based on a three-phase AC input power supply 20. The AC-DC converter 10 includes a power measurement circuit 102, a control circuit 104, and three bridge arm circuits (i.e., a first bridge arm circuit 1062, a second bridge arm circuit 1064, and a third bridge arm circuit 1066). The power measurement circuit 102 includes a plurality of current sensors 1026 and a plurality of voltage sensors 1028. The control circuit 104 includes a power calculation circuit 1022, a power threshold determination circuit 1023, and a control signal generation circuit 1024.

The power calculation circuit 1022 of the control circuit 104 is coupled to the current detectors 1026 and voltage sensors 1028 of the power measurement circuit 102; for the sake of simplification, the wiring from the power calculation circuit 1022 of the control circuit 104 to the current detectors 1026 and voltage sensors 1028 is omitted in FIG1. In each bridge arm circuit, the current sensor 1026 and the voltage sensor 1028 measure the current and voltage respectively so that the power calculation circuit 1022 of the control circuit 104 calculates the input power (e.g., using the formula: power equals current multiplied by voltage). The power calculation circuit 1022 can calculate one or more of the input power of the three bridge arm circuits (e.g., calculate the sum of the input power of the three bridge arm circuits).

Each of the bridge arm circuits includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, and a sixth switch S6; these switches may be transistor switches (e.g., all of these switches are N-channel metal-oxide-semiconductor field-effect transistors, NPN bipolar transistors, silicon carbide transistors, gallium nitride transistors, insulated gate bipolar transistors).

Figure 1 omits the wiring from the control signal generation circuit 1024 of the control circuit 104 to the control terminals of all the switches. Taking the first bridge arm circuit 1062 as an example: the first switch S1 includes a control terminal coupled to the control signal generation circuit 1024 of the control circuit 104, a first terminal coupled to a first output terminal 108 via a first capacitor C1, and a second terminal. The second switch S2 includes a control signal generating circuit 1024 with a control terminal coupled to the control circuit 104, a first terminal coupled to the second terminal of the first switch S1, and a second terminal coupled to a first input inductor L1 (for the second bridge arm circuit 1064, the second terminal 2E is coupled to a second input inductor L2; for the third bridge arm circuit 1066, the second terminal 2E is coupled to a third input inductor L3). The third switch S3 includes a control signal generating circuit 1024 with a control terminal coupled to the control circuit 104, a first terminal coupled to the second terminal of the second switch S2 and the first input inductor L1 (for the second bridge arm circuit 1064, the first terminal is coupled to the second terminal of the second switch S2 and the second input inductor L2; for the third bridge arm circuit 1066, the first terminal is coupled to the second terminal of the second switch S2 and the third input inductor L3), and a second terminal. The fourth switch S4 includes a control signal generating circuit 1024 with a control terminal coupled to the control circuit 104, a first terminal coupled to the second terminal of the third switch S3, and a second terminal coupled to the first output terminal 108 via a second capacitor C2. The fifth switch S5 includes a control signal generating circuit 1024 with a control terminal coupled to the control circuit 104, a first terminal coupled to the second terminal of the first switch S1 and the first terminal of the second switch S2, and a second terminal coupled to the first output terminal 108. The sixth switch S6 includes a control signal generating circuit 1024 with a control terminal coupled to the control circuit 104, a first terminal coupled to the second terminal of the fifth switch S5 and the first output terminal 108, and a second terminal coupled to the second terminal of the third switch S3 and the first terminal of the fourth switch S4. The AC-DC conversion circuit 10 disclosed herein may also be referred to as an active neutral point clamped (ANPC) power converter.

Please refer to Figure 2, which is a power-power loss comparison diagram of an embodiment of the first pulse width modulation mode (PWM1) and the second pulse width modulation mode (PWM2) of this disclosure; and also refer to Figure 1. This disclosure provides a first pulse width modulation mode (PWM1) and a second pulse width modulation mode (PWM2) to control the switches to generate the DC output voltage 22 according to the three-phase AC input power supply 20, and Figure 2 shows an embodiment of the AC-DC conversion circuit 10 in the first pulse width modulation mode (PWM1) and the second pulse width modulation mode (PWM2).

For example, when the power is 400 watts, the AC-DC converter 10 has a power loss of 1.5 watts in the first pulse width modulation mode (PWM1), and a power loss of 4 watts in the second pulse width modulation mode (PWM2); when the power is 3200 watts, the AC-DC converter 10 has a power loss of 9 watts in the first pulse width modulation mode (PWM1). The AC-DC converter 10 has a power loss of 9.5 watts in the second pulse width modulation mode (PWM2) when the power is 4000 watts; the AC-DC converter 10 has a power loss of 14.5 watts in the first pulse width modulation mode (PWM1) when the power is 4000 watts, and a power loss of 11.5 watts in the second pulse width modulation mode (PWM2) when the power is 5 watts.

As shown in the power-power loss comparison diagram in Figure 2, when the power is less than 3200 watts, the power loss of the AC-DC converter 10 in the first pulse width modulation mode (PWM1) can be lower than the power loss of the AC-DC converter 10 in the second pulse width modulation mode (PWM2); however, when the power is greater than or equal to 3200 watts, the power loss of the AC-DC converter 10 in the second pulse width modulation mode (PWM2) can be lower than the power loss of the AC-DC converter 10 in the first pulse width modulation mode (PWM1).

Therefore, in the embodiment shown in Figure 2, this disclosure uses a power threshold of 3200 watts. When the power is less than 3200 watts, the AC-DC converter 10 is operated using the first pulse width modulation mode (PWM1), and when the power is greater than or equal to 3200 watts, the AC-DC converter 10 is operated using the second pulse width modulation mode (PWM2), thereby minimizing the overall power loss. Thus, the effectiveness of this disclosure lies in reducing the overall power loss of the AC-DC converter. In the following text, the first pulse width modulation mode (PWM1) is referred to as the light-load mode LL, and the second pulse width modulation mode (PWM2) is referred to as the heavy-load mode HL.

Please refer to Figure 3, which is a waveform comparison diagram of the present disclosure in light-load mode LL; and also refer to Figure 1. The power threshold determination circuit 1023 of the control circuit 104 is coupled to the power calculation circuit 1022, and compares the input power calculated by the power calculation circuit 1022 with a preset power threshold. When the power threshold determination circuit 1023 determines that the power measurement value is less than the power threshold (e.g., 3200 watts as shown in Figure 2), the control signal generation circuit 1024 of the control circuit 104 correspondingly generates a control signal to set the three bridge arm circuits to operate in a light-load mode LL (i.e., the first pulse width modulation mode PWM1 shown in Figure 2), as detailed below. Taking the first bridge arm circuit 1062 as an example, the control signal generating circuit 1024 of the control circuit 104 generates a first control signal Q1, a second control signal Q2, a third control signal Q3, a fourth control signal Q4, a fifth control signal Q5, and a sixth control signal Q6 to control the conduction state of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, and the sixth switch S6 of the first bridge arm circuit 1062, respectively. FIG3 also shows the first inductance current IL1 of the first input inductor L1.

In the first positive half-cycle signal 1P of the first single-phase AC power AC1 of the three-phase AC input power supply 20, regardless of whether it is in charging mode CM (charging the inductor) or discharging mode DM (discharging the inductor), the control signal generating circuit 1024 of the control circuit 104 sets the second switch S2 coupled to the first bridge arm circuit 1062 of the first single-phase AC power supply AC1 to be turned on, and sets the third switch S3 and the fourth switch S4 to be turned off; wherein in the charging mode CM of the first positive half-cycle signal 1P, the control signal generating circuit 1024 of the control circuit 104 sets the first bridge arm circuit... In circuit 1062, the first switch S1 and the sixth switch S6 are not turned on, and the fifth switch S5 is turned on (where the conduction frequency of the fifth switch S5 is different from the conduction frequency of the second switch S2); while in a discharge mode DM of the first positive half-cycle signal 1P, the control signal generating circuit 1024 of the control circuit 104 sets the first switch S1 and the sixth switch S6 of the first bridge arm circuit 1062 to be turned on (where the conduction frequency of the first switch S1 is the same as the conduction frequency of the sixth switch S6, but different from the conduction frequency of the second switch S2), and sets the fifth switch S5 to be turned off.

In a first negative half-cycle signal 1N of the first single-phase AC power AC1 of the three-phase AC input power supply 20, regardless of whether it is in charging mode CM or discharging mode DM, the control signal generating circuit 1024 of the control circuit 104 sets the first switch S1 and the second switch S2 of the first bridge arm circuit 1062 to be de-conducting, and sets the third switch S3 to be on; wherein in a charging mode CM of the first negative half-cycle signal 1N, the control signal generating circuit 1024 of the control circuit 104 sets the fourth switch S4 of the first bridge arm circuit 1062 to... The fifth switch S5 is not turned on, and the sixth switch S6 is turned on (where the conduction frequency of the sixth switch S6 is different from the conduction frequency of the third switch S3); while in a discharge mode DM of the first negative half-cycle signal 1N, the control signal generating circuit 1024 of the control circuit 104 sets the fourth switch S4 and the fifth switch S5 of the first bridge arm circuit 1062 to be turned on (where the conduction frequency of the fourth switch S4 is the same as the conduction frequency of the fifth switch S5, but different from the conduction frequency of the third switch S3), and sets the sixth switch S6 to be turned off.

Please refer to Figure 4, which is a waveform comparison diagram of the present disclosure in heavy-load mode HL; and also refer to Figure 1. When the power measurement value is greater than the power threshold, the control signal generating circuit 1024 of the control circuit 104 sets the three bridge arm circuits to operate in a heavy-load mode HL (that is, the second pulse width modulation mode PWM2 shown in Figure 2), as detailed below, taking the first bridge arm circuit 1062 as an example:

In a second positive half-cycle signal 2P of the first single-phase AC power AC1 of the three-phase AC input power supply 20, regardless of whether it is in charging mode CM or discharging mode DM, the control signal generating circuit 1024 of the control circuit 104 sets the second switch S2 and the sixth switch S6 of the first bridge arm circuit 1062 to be turned on, and sets the fourth switch S4 to be turned off; wherein in a charging mode CM of the second positive half-cycle signal 2P, the control signal generating circuit 1024 of the control circuit 104 sets the first switch S1 of the first bridge arm circuit 1062 to be turned off, and sets the third switch S... 3. The fifth switch S5 is turned on (where the second switch S2, the third switch S3, the fifth switch S5 and the sixth switch S6 have the same conduction frequency; turning on the four switches can share the charging current and reduce conduction loss); while in the discharge mode DM of the second positive half-cycle signal 2P, the control signal generating circuit 1024 of the control circuit 104 sets the first switch S1 of the first bridge arm circuit 1062 to be turned on (where the first switch S1, the second switch S2 and the sixth switch S6 have the same conduction frequency), and sets the third switch S3 and the fifth switch S5 to be turned off.

In a second negative half-cycle signal 2N of the first single-phase AC power AC1 of the three-phase AC input power supply 20, regardless of whether it is in charging mode CM or discharging mode DM, the control signal generating circuit 1024 of the control circuit 104 sets the first switch S1 of the first bridge arm circuit 1062 to be non-conducting, and sets the third switch S3 and the fifth switch S5 to be conducting; wherein in a charging mode CM of the second negative half-cycle signal 2N, the control signal generating circuit 1024 of the control circuit 104 sets the second switch S2 and the sixth switch S6 of the first bridge arm circuit 1062 to be conducting (its In the first bridge arm circuit 1062, the second switch S2, the third switch S3, the fifth switch S5, and the sixth switch S6 all have the same conduction frequency; turning on the four switches can share the charging current and reduce conduction losses, and the fourth switch S4 is set to be off; in the discharge mode DM of the second negative half-cycle signal 2N, the control signal generating circuit 1024 of the control circuit 104 sets the second switch S2 and the sixth switch S6 of the first bridge arm circuit 1062 to be off, and sets the fourth switch S4 to be on (wherein the third switch S3, the fourth switch S4, and the fifth switch S5 all have the same conduction frequency).

The operation of each phase of the bridge arm circuit is similar or the same (therefore, it will not be described in detail here), but the phase difference is 120 degrees; that is, the phase difference of the first single-phase AC power supply AC1, the second single-phase AC power supply AC2 and the third single-phase AC power supply AC3 of the three-phase AC input power supply 20 is 120 degrees, and the phase difference of the control signal generating circuit 1024 of the control circuit 104 is 120 degrees for the control signals Q0 of the three bridge arm circuits (that is, the first control signal Q1, the second control signal Q2, the third control signal Q3, the fourth control signal Q4, the fifth control signal Q5 and the sixth control signal Q6).

For example, in the charging mode CM, when the first bridge arm circuit 1062 is in the first positive half-cycle signal 1P of the first single-phase AC power supply AC1, the second bridge arm circuit 1064 may also be in the first positive half-cycle signal 1P of the second single-phase AC power supply AC2, and the third bridge arm circuit 1066 may be in the first negative half-cycle signal 1N of the third single-phase AC power supply AC3. Therefore, as described above, the second switch S2 and the fifth switch S5 of the first bridge arm circuit 1062 will be turned on, the second switch S2 and the fifth switch S5 of the second bridge arm circuit 1064 will also be turned on, and the third switch S3 and the sixth switch S6 of the third bridge arm circuit 1066 will be turned on.

When the input power is less than the power threshold, the power measurement circuit 102 and the control signal generation circuit 1024 of the control circuit 104 set the power measurement value to a low potential, causing the control signal generation circuit 1024 of the control circuit 104 to set the three bridge circuits to operate in the light-load mode LL. When the input power is greater than or equal to the power threshold, the power measurement circuit 102 and the control signal generation circuit 1024 of the control circuit 104 set the power measurement value to a high potential, causing the control signal generation circuit 1024 of the control circuit 104 to set the three bridge circuits to operate in the heavy-load mode HL.

Please refer to Figure 5, which is a circuit block diagram of a second embodiment of the AC-DC conversion circuit 10 disclosed herein. The components shown in Figure 5 are the same as those shown in Figure 1; for simplicity, their descriptions will not be repeated here. Unlike Figure 1, the current sensor 1026 and voltage sensor 1028 of the power measurement circuit 102 in Figure 5 are used to measure an output power to generate the power measurement value. That is, the power measurement circuit 102 disclosed herein is used to measure at least one of the input power shown in Figure 1 and the output power shown in Figure 5 to generate the power measurement value.

When the output power is less than the power threshold, the power measurement circuit 102 and the control signal generation circuit 1024 of the control circuit 104 set the power measurement value to a low potential, causing the control signal generation circuit 1024 of the control circuit 104 to set the three bridge circuits to operate in the light-load mode LL. When the output power is greater than or equal to the power threshold, the power measurement circuit 102 and the control signal generation circuit 1024 of the control circuit 104 set the power measurement value to a high potential, causing the control signal generation circuit 1024 of the control circuit 104 to set the three bridge circuits to operate in the heavy-load mode HL.

Please refer to Figure 6, which is a circuit block diagram of a third embodiment of the AC-DC converter circuit 10 disclosed herein; the components shown in Figure 6 are the same as those shown in Figure 1, and for simplicity, their descriptions will not be repeated here; please refer to Figure 7, which is a block diagram of an embodiment of the logic circuit 110 disclosed herein; please refer to both Figure 6 and Figure 7. Unlike Figure 1, the AC-DC converter circuit 10 of Figure 6 further includes a logic circuit 110, which includes a plurality of gates 1101 and a plurality of gates 1102. For the sake of simplicity, Figure 6 omits the wiring from the logic circuit 110 to the control terminals of all the switches.

In the embodiment shown in Figure 7, the logic circuit 110 generates a discharge pulse width modulation (PWM) signal D, a charging PWM signal C, a positive half-cycle PWM signal P, and a negative half-cycle PWM signal N based on the control signal of the control circuit 104 and the generation circuit 1024. Based on the power measurement value (referred to as L in the following logical relationship), it correspondingly generates a first control signal Q1 and a second control signal Q2. Signals Q2, Q3, Q4, Q5, and Q6 respectively control the conduction states of the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, and the sixth switch S6 of the first bridge arm circuit 1062; wherein the logical relationship between the above signals, values, and conduction states is as follows:

Q1 = P and D

Q2 = (L and C) or P

Q3 = (L and C) or N

Q4 = N and D

Q5 = Q4 or (L and Q3) or (P and C) or (L and C)

Q6 = Q1 or (L and Q2) or (N and C) or (L and C)

In the charging mode CM of the first positive half-cycle signal 1P, in the charging mode CM of the first negative half-cycle signal 1N, in the charging mode CM of the second positive half-cycle signal 2P, and in the charging mode CM of the second negative half-cycle signal 2N, the control signal generating circuit 1024 of the control circuit 104 sets the charging pulse width modulation signal C to a high potential and the discharging pulse width modulation signal D to a low potential. In the discharge mode DM of the first positive half-cycle signal 1P, in the discharge mode DM of the first negative half-cycle signal 1N, in the discharge mode DM of the second positive half-cycle signal 2P, and in the discharge mode DM of the second negative half-cycle signal 2N, the control signal generating circuit 1024 of the control circuit 104 sets the charging pulse width modulation signal C to a low potential and the discharge pulse width modulation signal D to a high potential. In the first positive half-cycle signal 1P of the first single-phase AC power AC1 of the three-phase AC input power supply 20 and in the second positive half-cycle signal 2P of the first single-phase AC power AC1 of the three-phase AC input power supply 20, the control signal generating circuit 1024 of the control circuit 104 sets the positive half-cycle pulse width modulation signal P to a high potential and the negative half-cycle pulse width modulation signal N to a low potential. In the first negative half-cycle signal 1N of the first single-phase AC power supply AC1 of the three-phase AC input power supply 20 and in the second negative half-cycle signal 2N of the first single-phase AC power supply AC1 of the three-phase AC input power supply 20, the control signal generating circuit 1024 of the control circuit 104 sets the positive half-cycle pulse width modulation signal P to low potential and the negative half-cycle pulse width modulation signal N to high potential. When the power measurement value (L) is low potential, the control signal generating circuit 1024 of the control circuit 104 sets the three bridge arm circuits to operate in the light load mode LL. When the power measurement value (L) is high, the control signal generating circuit 1024 of the control circuit 104 sets the three bridge arm circuits to operate in the heavy load mode HL.

The control circuit 104 disclosed herein can be a digital signal processor. In the embodiments of Figures 1 and 5, the control circuit 104 needs to output a total of eighteen pulse width modulation signals (i.e., signal channels) to control all eighteen switches. Therefore, the design of the control circuit 104 is more complex and the price is more expensive, belonging to the category of high-end digital signal processors. In the embodiment shown in Figure 6, for one bridge arm circuit, the control circuit 104 needs to output four pulse width modulation (PWM) signals (i.e., the discharge PWM signal D, the charging PWM signal C, the positive half-cycle PWM signal P, and the negative half-cycle PWM signal N) and one GPIO signal (i.e., the power measurement value (L)) to control one bridge arm circuit. With six switches and the three bridge arm circuits sharing the GPIO signal, the control circuit 104 only needs to output twelve pulse width modulation signals (4*3=12) plus one GPIO signal to control all eighteen switches of the three bridge arm circuits. Therefore, the design of the control circuit 104 is relatively simple and inexpensive, belonging to the mid-to-low-end digital signal processor category. Thus, the embodiment in Figure 6 achieves the benefit of reducing the cost of the control circuit 104.

Please refer to Figure 8, which is a flowchart of the operation method of the AC-DC conversion circuit disclosed herein. The operation method of the AC-DC conversion circuit disclosed herein uses an AC-DC conversion circuit to generate a DC output voltage based on a three-phase AC input power supply. The AC-DC conversion circuit includes a power measurement circuit, a control circuit, and three bridge arm circuits. The control circuit is coupled to the power measurement circuit. Each bridge arm circuit includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, and a sixth switch.

The first switch includes a control terminal coupled to the control circuit, a first terminal coupled to a first output terminal via a first capacitor, and a second terminal. The second switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch, and a second terminal coupled to a first input inductor. The third switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the second switch and the first input inductor, and a second terminal. The fourth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the third switch, and a second terminal coupled to the first output terminal via a second capacitor. The fifth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch and the first terminal of the second switch, and a second terminal coupled to the first output terminal. The sixth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the fifth switch and the first output terminal, and a second terminal coupled to the second terminal of the third switch and the first terminal of the fourth switch.

The operation method of this AC-DC conversion circuit includes the following steps:

Step S02: The power measurement circuit measures at least one of an input power and an output power to generate a power measurement value. Then, the AC-DC conversion circuit operation method proceeds to step S04.

Step S04: The control circuit determines the power measurement value. When the power measurement value is less than a power threshold, the AC-DC conversion circuit operation method proceeds to step S06; when the power measurement value is greater than the power threshold, the AC-DC conversion circuit operation method proceeds to step S08.

Step S06: The control circuit configures the three bridge arm circuits to operate in a light-load mode. Step S06 specifically includes the following: In a first positive half-cycle signal of a first single-phase AC power supply of the three-phase AC input power supply, the control circuit configures the second switch coupled to the first bridge arm circuit of the first single-phase AC power supply to be turned on, and configures the third switch and the fourth switch to be turned off; In a charging mode of the first positive half-cycle signal, the control circuit configures the first switch and the sixth switch of the first bridge arm circuit to be turned off, and configures the fifth switch to be turned on; In a discharging mode of the first positive half-cycle signal, the control circuit configures the first switch and the sixth switch of the first bridge arm circuit to be turned on, and configures the fifth switch to be turned off. In a first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch and the second switch of the first bridge arm circuit to be off, and sets the third switch to be on; in a charging mode of the first negative half-cycle signal, the control circuit sets the fourth switch and the fifth switch of the first bridge arm circuit to be off, and sets the sixth switch to be on; in a discharging mode of the first negative half-cycle signal, the control circuit sets the fourth switch and the fifth switch of the first bridge arm circuit to be on, and sets the sixth switch to be off.

Step S08: The control circuit sets the three bridge arm circuits to operate in a heavy-load mode. Step S08 specifically includes the following: In a second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be turned on, and sets the fourth switch to be turned off; In a charging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be turned off, and sets the third switch and the fifth switch to be turned on; In a discharging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be turned on, and sets the third switch and the fifth switch to be turned off. In a second negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch of the first bridge arm circuit to be off, and sets the third switch and the fifth switch to be on; in a charging mode of the second negative half-cycle signal, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be on, and sets the fourth switch to be off; in a discharging mode of the second negative half-cycle signal, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be off, and sets the fourth switch to be on.

The phases of the first single-phase AC power supply, the second single-phase AC power supply, and the third single-phase AC power supply of the three-phase AC input power supply are 120 degrees apart, and the phases of the control signals of the three bridge arm circuits of the control circuit are 120 degrees apart.

In one embodiment: when the input power is less than the power threshold, the power measurement circuit sets the power measurement value to a low potential, causing the control circuit to set the three bridge circuits to operate in the light-load mode; when the input power is greater than or equal to the power threshold, the power measurement circuit sets the power measurement value to a high potential, causing the control circuit to set the three bridge circuits to operate in the heavy-load mode.

In another embodiment: when the output power is less than the power threshold, the power measurement circuit sets the power measurement value to a low potential, causing the control circuit to set the three bridge circuits to operate in the light-load mode; when the output power is greater than or equal to the power threshold, the power measurement circuit sets the power measurement value to a high potential, causing the control circuit to set the three bridge circuits to operate in the heavy-load mode.

In addition, the AC-DC conversion circuit may further include a logic circuit that, based on a discharge pulse width modulation signal (D), a charging pulse width modulation signal (C), a positive half-cycle pulse width modulation signal (P), and a negative half-cycle pulse width modulation signal (N) generated by the control circuit, and based on the power measurement value (L), correspondingly generates a first control signal (Q1), a second control signal (Q2), a third control signal (Q3), a fourth control signal (Q4), a fifth control signal (Q5), and a sixth control signal (Q6) to control the conduction state of the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch of the first bridge arm circuit, respectively; wherein:

Q1 = P and D

Q2 = (L and C) or P

Q3 = (L and C) or N

Q4 = N and D

Q5 = Q4 or (L and Q3) or (P and C) or (L and C)

Q6 = Q1 or (L and Q2) or (N and C) or (L and C)

In the charging mode of the first positive half-cycle signal, the charging mode of the first negative half-cycle signal, the charging mode of the second positive half-cycle signal, and the charging mode of the second negative half-cycle signal, the control circuit sets the charging pulse width modulation signal (C) to a high potential and the discharging pulse width modulation signal (D) to a low potential; in the discharging mode of the first positive half-cycle signal... In the discharge mode of the first negative half-cycle signal, the discharge mode of the second positive half-cycle signal, and the discharge mode of the second negative half-cycle signal, the control circuit sets the charging pulse width modulation signal (C) to a low potential and the discharging pulse width modulation signal (D) to a high potential; in the first positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply... And in the second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the positive half-cycle pulse width modulation signal (P) to a high potential and the negative half-cycle pulse width modulation signal (N) to a low potential; in the first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply and in the first single-phase AC power supply of the three-phase AC input power supply In the second negative half-cycle signal, the control circuit sets the positive half-cycle pulse width modulation signal (P) to low potential and the negative half-cycle pulse width modulation signal (N) to high potential; when the power measurement value (L) is low potential, the control circuit sets the three bridge arm circuits to operate in the light load mode; when the power measurement value (L) is high potential, the control circuit sets the three bridge arm circuits to operate in the heavy load mode.

The remaining technical contents of the AC-DC conversion circuit operation method disclosed herein are similar to the technical contents of the AC-DC conversion circuit 10 disclosed herein, and therefore will not be repeated here.

Although this disclosure has been described with reference to embodiments thereof, it should be understood that this disclosure is not limited to its details; various substitutions and modifications have been proposed in the foregoing description, and other substitutions and modifications will be apparent to those skilled in the art; therefore, all such substitutions and modifications are intended to be included within the scope of this disclosure.

1N: First negative half-cycle signal 1P: First positive half-cycle signal 2N: Second negative half-cycle signal 2P: Second positive half-cycle signal 10: AC-DC conversion circuit 20: Three-phase AC input power supply 22: DC output voltage 102: Power measurement circuit 104: Control circuit 108: First output terminal 110: Logic circuit 1022: Power calculation circuit 1023: Power threshold judgment circuit 1024: Control signal generation circuit 1026: Current sensor 1028: Voltage sensor 1062: First bridge arm circuit 1064: Second bridge arm circuit 1066: Third bridge arm circuit 1101: Interlock gate 1102: Alternating gate AC1: First single-phase AC power supply AC2: Second single-phase AC power supply AC3: Third single-phase AC power supply C: Charging pulse width modulation signal C1: First capacitor C2: Second capacitor D: Discharge pulse width modulation signal HL: Heavy load mode IL1: First inductor current L1: First input inductor L2: Second input inductor L3: Third input inductor LL: Light load mode N: Negative half-cycle pulse width modulation signal P: Positive half-cycle pulse width modulation signal PWM1: First pulse width modulation mode PWM2: Second pulse width modulation mode Q0: Control signal Q1: First control signal Q2: Second control signal Q3: Third control signal Q4: Fourth control signal Q5: Fifth control signal Q6: Sixth control signal S02: Step S04: Step S06: Step S08: Step S1: First switch S2: Second switch S3: Third switch S4: Fourth switch S5: Fifth switch S6: Sixth switch

Figure 1 is a circuit block diagram of a first embodiment of the AC-DC conversion circuit disclosed herein.

Figure 2 is a power-power loss comparison diagram of an embodiment of the first and second pulse width modulation modes disclosed herein.

Figure 3 is a waveform comparison diagram of the present disclosure in light load mode.

Figure 4 is a waveform comparison diagram of the disclosed method in overload mode.

Figure 5 is a circuit block diagram of a second embodiment of the AC-DC conversion circuit disclosed herein.

Figure 6 is a circuit block diagram of a third embodiment of the AC-DC conversion circuit disclosed herein.

Figure 7 is a block diagram of an embodiment of the logic circuit disclosed herein.

Figure 8 is a flowchart of the operation method of the AC-DC conversion circuit disclosed herein.

10: AC-DC conversion circuit

20: Three-phase AC input power supply

22: DC output voltage

102: Power Measurement Circuit

104: Control Circuit

108: First Output Terminal

1022: Power Calculation Circuit

1023: Power Threshold Determination Circuit

1024: Control signal generation circuit

1026: Flu Detector

1028: Voltage Sensor

1062: First Bridge Arm Circuit

1064: Second Bridge Arm Circuit

1066: Third bridge arm circuit

AC1: First single-phase AC power supply

AC2: Second single-phase AC power supply

AC3: Third single-phase AC power supply

C1: First capacitor

C2: Second capacitor

L1: First input inductor

L2: Second input inductor

L3: Third input inductor

Q0: Control signal

Q1: First control signal

Q2: Second control signal

Q3: Third control signal

Q4: Fourth control signal

Q5: Fifth control signal

Q6: Sixth control signal

S1: First Switch

S2: Second Switch

S3: Third Switch

S4: Fourth Switch

S5: The Fifth Stage

S6: The Sixth Switch

Claims (10)

An AC-DC converter circuit for generating a DC output voltage based on a three-phase AC input power supply, comprising: a power measurement circuit for measuring at least one of an input power and an output power to generate a power measurement value; a control circuit coupled to the power measurement circuit; and three bridge arm circuits, each of the bridge arm circuits comprising: a first switch, including a control terminal coupled to the control circuit, a first terminal coupled to a first output terminal via a first capacitor, and a second terminal; a second switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch, and a second terminal coupled to a first input inductor; A third switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the second switch and the first input inductor, and a second terminal; A fourth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the third switch, and a second terminal coupled to the first output terminal via a second capacitor; A fifth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch and the first terminal of the second switch, and a second terminal coupled to the first output terminal; and A sixth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the fifth switch and the first output terminal, and a second terminal coupled to the second terminal of the third switch and the first terminal of the fourth switch; When the measured power value is less than a power threshold, the control circuit configures the three bridge arm circuits to operate in a light-load mode: During a first positive half-cycle signal of a first single-phase AC power supply of the three-phase AC input power supply, the control circuit configures the second switch coupled to the first bridge arm circuit of the first single-phase AC power supply to be turned on, and the third and fourth switches to be turned off; During a charging mode of the first positive half-cycle signal, the control circuit configures the first and sixth switches of the first bridge arm circuit to be turned off, and the fifth switch to be turned on; During a discharging mode of the first positive half-cycle signal, the control circuit configures the first and sixth switches of the first bridge arm circuit to be turned on, and the fifth switch to be turned off; In a first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch and the second switch of the first bridge arm circuit to be de-energized, and sets the third switch to be energized; in a charging mode of the first negative half-cycle signal, the control circuit sets the fourth switch and the fifth switch of the first bridge arm circuit to be de-energized, and sets the sixth switch to be energized; in a discharging mode of the first negative half-cycle signal, the control circuit sets the fourth switch and the fifth switch of the first bridge arm circuit to be energized, and sets the sixth switch to be de-energized; When the measured power value is greater than the power threshold, the control circuit sets the three bridge arm circuits to operate in a heavy-load mode: In a second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be turned on, and sets the fourth switch to be turned off; in a charging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be turned off, and sets the third switch and the fifth switch to be turned on; in a discharging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be turned on, and sets the third switch and the fifth switch to be turned off. In a second negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch of the first bridge arm circuit to be off, and sets the third and fifth switches to be on; in a charging mode of the second negative half-cycle signal, the control circuit sets the second and sixth switches of the first bridge arm circuit to be on, and sets the fourth switch to be off; in a discharging mode of the second negative half-cycle signal, the control circuit sets the second and sixth switches of the first bridge arm circuit to be off, and sets the fourth switch to be on. For example, in the AC-DC conversion circuit of claim 1, the phases of the first single-phase AC power supply, the second single-phase AC power supply, and the third single-phase AC power supply of the three-phase AC input power supply are 120 degrees apart, and the phases of the control signals of the three bridge arm circuits of the control circuit are 120 degrees apart. As in the AC-DC conversion circuit of claim 1, when the input power is less than the power threshold, the power measurement circuit sets the power measurement value to a low potential, causing the control circuit to set the three bridge circuits to operate in the light-load mode; when the input power is greater than or equal to the power threshold, the power measurement circuit sets the power measurement value to a high potential, causing the control circuit to set the three bridge circuits to operate in the heavy-load mode. As in the AC-DC conversion circuit of claim 1, when the output power is less than the power threshold, the power measurement circuit sets the power measurement value to a low potential, causing the control circuit to set the three bridge circuits to operate in the light-load mode; when the output power is greater than or equal to the power threshold, the power measurement circuit sets the power measurement value to a high potential, causing the control circuit to set the three bridge circuits to operate in the heavy-load mode. The AC-DC converter circuit of claim 1 further includes a logic circuit that, based on a discharge pulse width modulation (D), a charging pulse width modulation (C), a positive half-cycle pulse width modulation (P), and a negative half-cycle pulse width modulation (N) generated by the control circuit, and based on the power measurement value (L), correspondingly generates a first control signal (Q1), a second control signal (Q2), a third control signal (Q3), a fourth control signal (Q4), a fifth control signal (Q5), and a sixth control signal (Q6) to control the conduction state of the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch of the first bridge arm circuit, respectively; wherein: Q1 = P and D Q2 = (L and C) or P Q3 = (L and C) or N Q4 = N and D Q5 = Q4 or (L and Q3) or (P and C) or (L and C) Q6 = Q1 or (L and Q2) or (N and C) or (L and C) Whereinin the charging mode of the first positive half-cycle signal, the charging mode of the first negative half-cycle signal, the charging mode of the second positive half-cycle signal, and the charging mode of the second negative half-cycle signal, the control circuit sets the charging pulse width modulation signal (C) to a high potential and the discharging pulse width modulation signal (D) to a low potential; in the discharging mode of the first positive half-cycle signal... In the discharge mode of the first negative half-cycle signal, the discharge mode of the second positive half-cycle signal, and the discharge mode of the second negative half-cycle signal, the control circuit sets the charging pulse width modulation signal (C) to a low potential and the discharging pulse width modulation signal (D) to a high potential; in the first positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply... And in the second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the positive half-cycle pulse width modulation signal (P) to a high potential and the negative half-cycle pulse width modulation signal (N) to a low potential; in the first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply and in the first single-phase AC power supply of the three-phase AC input power supply In the second negative half-cycle signal, the control circuit sets the positive half-cycle pulse width modulation signal (P) to low potential and the negative half-cycle pulse width modulation signal (N) to high potential; when the power measurement value (L) is low potential, the control circuit sets the three bridge arm circuits to operate in the light load mode; when the power measurement value (L) is high potential, the control circuit sets the three bridge arm circuits to operate in the heavy load mode. An AC-DC converter circuit operation method, wherein an AC-DC converter circuit generates a DC output voltage based on a three-phase AC input power supply. The AC-DC converter circuit includes a power measurement circuit, a control circuit, and three bridge arm circuits. The control circuit is coupled to the power measurement circuit. Each bridge arm circuit includes: a first switch, including a control terminal coupled to the control circuit, a first terminal coupled to a first output terminal via a first capacitor, and a second terminal; a second switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch, and a second terminal coupled to a first input inductor; a third switch, including a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the second switch, the first input inductor, and a second terminal; A fourth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the third switch, and a second terminal coupled to the first output terminal via a second capacitor; A fifth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the first switch and the first terminal of the second switch, and a second terminal coupled to the first output terminal; A sixth switch includes a control terminal coupled to the control circuit, a first terminal coupled to the second terminal of the fifth switch and the first output terminal, and a second terminal coupled to the second terminal of the third switch and the first terminal of the fourth switch; The AC-DC conversion circuit operation method includes: The power measurement circuit measures at least one of an input power and an output power to generate a power measurement value; When the measured power value is less than a power threshold, the control circuit configures the three bridge arm circuits to operate in a light-load mode: During a first positive half-cycle signal of a first single-phase AC power supply of the three-phase AC input power supply, the control circuit configures the second switch coupled to the first bridge arm circuit of the first single-phase AC power supply to be turned on, and configures the third and fourth switches to be turned off; During a charging mode of the first positive half-cycle signal, the control circuit configures the first and sixth switches of the first bridge arm circuit to be turned off, and configures the fifth switch to be turned on; During a discharging mode of the first positive half-cycle signal, the control circuit configures the first and sixth switches of the first bridge arm circuit to be turned on, and configures the fifth switch to be turned off; In a first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch and the second switch of the first bridge arm circuit to be de-energized, and sets the third switch to be energized; in a charging mode of the first negative half-cycle signal, the control circuit sets the fourth switch and the fifth switch of the first bridge arm circuit to be de-energized, and sets the sixth switch to be energized; in a discharging mode of the first negative half-cycle signal, the control circuit sets the fourth switch and the fifth switch of the first bridge arm circuit to be energized, and sets the sixth switch to be de-energized; When the measured power value is greater than the power threshold, the control circuit sets the three bridge arm circuits to operate in a heavy-load mode: In a second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the second switch and the sixth switch of the first bridge arm circuit to be turned on, and sets the fourth switch to be turned off; in a charging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be turned off, and sets the third switch and the fifth switch to be turned on; in a discharging mode of the second positive half-cycle signal, the control circuit sets the first switch of the first bridge arm circuit to be turned on, and sets the third switch and the fifth switch to be turned off. In a second negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the first switch of the first bridge arm circuit to be off, and sets the third and fifth switches to be on; in a charging mode of the second negative half-cycle signal, the control circuit sets the second and sixth switches of the first bridge arm circuit to be on, and sets the fourth switch to be off; in a discharging mode of the second negative half-cycle signal, the control circuit sets the second and sixth switches of the first bridge arm circuit to be off, and sets the fourth switch to be on. As in the AC-DC conversion circuit operation method of claim 6, the phase difference between the first single-phase AC power supply, the second single-phase AC power supply and the third single-phase AC power supply of the three-phase AC input power supply is 120 degrees, and the phase difference between the control signals of the three bridge arm circuits of the control circuit is 120 degrees. As in the AC-DC conversion circuit operation method of claim 6, when the input power is less than the power threshold, the power measurement circuit sets the power measurement value to a low potential, causing the control circuit to set the three bridge circuits to operate in the light-load mode; when the input power is greater than or equal to the power threshold, the power measurement circuit sets the power measurement value to a high potential, causing the control circuit to set the three bridge circuits to operate in the heavy-load mode. As in the AC-DC conversion circuit operation method of claim 6, when the output power is less than the power threshold, the power measurement circuit sets the power measurement value to a low potential, causing the control circuit to set the three bridge circuits to operate in the light-load mode; when the output power is greater than or equal to the power threshold, the power measurement circuit sets the power measurement value to a high potential, causing the control circuit to set the three bridge circuits to operate in the heavy-load mode. As in the AC-DC conversion circuit operation method of claim 6, the AC-DC conversion circuit further includes a logic circuit that, based on a discharge pulse width modulation signal (D), a charging pulse width modulation signal (C), a positive half-cycle pulse width modulation signal (P), and a negative half-cycle pulse width modulation signal (N) generated by the control circuit, and based on the power measurement value (L), correspondingly generates a first control signal (Q1), a second control signal (Q2), a third control signal (Q3), a fourth control signal (Q4), a fifth control signal (Q5), and a sixth control signal (Q6) to control the conduction state of the first switch, the second switch, the third switch, the fourth switch, the fifth switch, and the sixth switch of the first bridge arm circuit, respectively; wherein: Q1 = P and D Q2 = (L and C) or P Q3 = (L and C) or N Q4 = N and D Q5 = Q4 or (L and Q3) or (P and C) or (L and C) Q6 = Q1 or (L and Q2) or (N and C) or (L and C) Whereinin the charging mode of the first positive half-cycle signal, the charging mode of the first negative half-cycle signal, the charging mode of the second positive half-cycle signal, and the charging mode of the second negative half-cycle signal, the control circuit sets the charging pulse width modulation signal (C) to a high potential and the discharging pulse width modulation signal (D) to a low potential; in the discharging mode of the first positive half-cycle signal... In the discharge mode of the first negative half-cycle signal, the discharge mode of the second positive half-cycle signal, and the discharge mode of the second negative half-cycle signal, the control circuit sets the charging pulse width modulation signal (C) to a low potential and the discharging pulse width modulation signal (D) to a high potential; in the first positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply... And in the second positive half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply, the control circuit sets the positive half-cycle pulse width modulation signal (P) to a high potential and the negative half-cycle pulse width modulation signal (N) to a low potential; in the first negative half-cycle signal of the first single-phase AC power supply of the three-phase AC input power supply and in the first single-phase AC power supply of the three-phase AC input power supply In the second negative half-cycle signal, the control circuit sets the positive half-cycle pulse width modulation signal (P) to low potential and the negative half-cycle pulse width modulation signal (N) to high potential; when the power measurement value (L) is low potential, the control circuit sets the three bridge arm circuits to operate in the light load mode; when the power measurement value (L) is high potential, the control circuit sets the three bridge arm circuits to operate in the heavy load mode.