Power supply circuit and control method and control apparatus therefor, and refrigeration device

Abstract

The present application discloses a power supply circuit and a control method and control apparatus therefor, and a refrigeration device. The power supply circuit comprises a power supply input end for connecting to a three-phase alternating current voltage, a midpoint switch (20), two PFC diodes (30), two bus switching transistors (40), and a switching circuit (50); a first end of the midpoint switch (20) is electrically connected to the power supply input end; the two PFC diodes (30) are connected in series; a second end of the midpoint switch (20) is electrically connected to a common connection end of the two PFC diodes (30); each bus switching transistor (40) is electrically connected to the midpoint switch (20) and the corresponding PFC diode (30), separately; a first end of the switching circuit (50) is electrically connected to the power supply input end, and a second end of the switching circuit (50) is electrically connected to the common connection end of the two PFC diodes (30); and when the switching circuit (50) is closed, a path between the power supply input end and the common connection end of the two PFC diodes (30) is turned on, so as to bypass the midpoint switch (20).

Description

Power supply circuit, control method and device thereof, and refrigeration equipment

[0001] Related applications

[0002] The present application claims priority to Chinese Patent Application No. 202411364438.8, filed on September 27, 2024, the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0003] The present application relates to the technical field of power electronics, and particularly relates to a power supply circuit, a control method and device thereof, and a refrigeration equipment. BACKGROUND

[0004] In a related PFC (power factor correction) scheme, a bus voltage control value is far greater than a demand of a load on a bus voltage in most operation intervals, so that a high-voltage switching device needs to be selected for an inverter part of a three-phase air conditioner, which increases hardware cost, and in addition, energy loss of the high-voltage switching device is large in the operation process. Although the SWISS-PFC topology proposed in the related technology can reduce the voltage, there are still deficiencies, for example, the voltage stress of the neutral line switch reaches a peak value at the switching moment, so the midpoint switch still needs to use the high-voltage switching device, and the cost and energy loss cannot be effectively reduced. SUMMARY

[0005] The main purpose of the present application is to propose a power supply circuit, a control method and device thereof, and a refrigeration equipment, which aims to reduce the circuit design cost and energy loss, so as to improve the safety and reliability of the refrigeration equipment in operation.

[0006] To achieve the above-mentioned purpose, the present application proposes a power supply circuit, which comprises:

[0007] a power supply input end for connecting a three-phase alternating voltage;

[0008] a midpoint switch, a first end of the midpoint switch being electrically connected with the power supply input end;

[0009] two PFC diodes, the two PFC diodes being connected in series, and a second end of the midpoint switch being electrically connected with a common connection end of the two PFC diodes;

[0010] two bus switch tubes, each of the bus switch tubes being electrically connected with the midpoint switch and the PFC diode;

[0011] A switch circuit, a first end of the switch circuit is electrically connected with the power input end, a second end of the switch circuit is electrically connected with the common connection end of the two PFC diodes; when the switch circuit is closed, the switch circuit turns on the path between the power input end and the common connection end of the two PFC diodes to bypass the midpoint switch.

[0012] In some embodiments, the power supply circuit has a first operating mode and a second operating mode;

[0013] In the first operating mode, the midpoint switch is in a conducting state, and the switch circuit is in a non-conducting state;

[0014] In the second operating mode, the midpoint switch is in a non-conducting state, and the switch circuit is in a conducting state.

[0015] In some embodiments, in the second operating mode, one of the two bus switch tubes is turned on / off with a preset first duty ratio; the other of the two bus switch tubes is turned on / off with a preset second duty ratio.

[0016] In some embodiments, the preset first duty ratio and the preset second duty ratio are calculated by the following formula: md = u dc + i s * R s ;

[0017] V md = d1u max - d2*u min ;

[0018] wherein V md is a target modulation voltage, u dc is a bus voltage, i s is a bus inductance current, R s is a path resistance; d1 is a preset first duty ratio; d2 is a preset second duty ratio; u max is a maximum phase voltage of a three-phase input voltage; u min is a minimum phase voltage of the three-phase input voltage.

[0019] In some embodiments, when the three-phase input voltage connected to the power input end is greater than a preset first voltage threshold, the power supply circuit works in the second working mode; when the three-phase input voltage connected to the power input end is less than the preset first voltage threshold, the power supply circuit works in the first working mode.

[0020] In some embodiments, when the three-phase input voltage connected to the power input terminal is greater than a preset first voltage threshold, the power supply circuit operates in a second operating mode; when the three-phase input voltage connected to the power input terminal is less than a preset second voltage threshold, the power supply circuit operates in a first operating mode.

[0021] In some embodiments, the preset second voltage threshold is less than the preset first voltage threshold.

[0022] In some embodiments, when switching between the first operating mode and the second operating mode, the power supply circuit is further provided with a dead time range, in which the switch circuit and the midpoint switch are both in an off state.

[0023] In some embodiments, the power supply circuit further comprises a neutral line, and the switch circuit is connected in series between the neutral line and the common connection terminal of the two PFC diodes.

[0024] The present application also proposes a control method of a power supply circuit, which is based on the power supply circuit according to any one of the above embodiments. The control method of the power supply circuit comprises:

[0025] obtaining a maximum voltage difference between the three-phase input voltages;

[0026] determining the operating mode of the power supply circuit according to the size relationship between the maximum voltage difference and the preset first voltage threshold;

[0027] controlling the on / off state of the midpoint switch and the switch circuit according to the determined operating mode.

[0028] In some embodiments, the operating mode comprises a first operating mode and a second operating mode.

[0029] determining the operating mode of the power supply circuit according to the size relationship between the maximum voltage difference and the preset first voltage threshold specifically comprises:

[0030] when the maximum voltage difference is less than or equal to the preset first voltage threshold, determining the operating mode of the power supply circuit as the first operating mode; in the first operating mode, the midpoint switch is in an on state, and the switch circuit is in an off state;

[0031] when the maximum voltage difference is greater than the preset first voltage threshold, determining the operating mode of the power supply circuit as the second operating mode; in the second operating mode, the midpoint switch is in an off state, and the switch circuit is in an on state.

[0032] In some embodiments, the step of obtaining the maximum voltage difference among the three-phase input voltages comprises:

[0033] obtaining a maximum phase voltage, an intermediate phase voltage and a minimum phase voltage of the three-phase input voltages;

[0034] calculating a difference between the maximum phase voltage and the intermediate phase voltage as a first voltage difference, and calculating a difference between the intermediate phase voltage and the minimum phase voltage as a second voltage difference;

[0035] obtaining a maximum value between the first voltage difference and the second voltage difference as the maximum voltage difference among the three-phase input voltages.

[0036] In some embodiments, the step of determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference among the three-phase input voltages is less than or equal to a preset first voltage threshold value comprises:

[0037] determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference among the three-phase input voltages is less than a preset second voltage threshold value;

[0038] wherein the preset second voltage threshold value is less than the preset first voltage threshold value.

[0039] In some embodiments, the step of determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference among the three-phase input voltages is less than or equal to a preset first voltage threshold value comprises:

[0040] determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference among the three-phase input voltages is less than a preset second voltage threshold value within a preset first time length;

[0041] wherein the preset second voltage threshold value is less than the preset first voltage threshold value.

[0042] The present application also proposes a control device, which comprises a memory, a processor, and a power supply circuit control program stored in the memory and executable on the processor, and the power supply circuit control program is configured to implement the steps of the power supply circuit control method according to any one of the above.

[0043] The present application also proposes a refrigeration equipment, which comprises the power supply circuit according to any one of the above, and / or comprises the control device according to the above.

[0044] In some embodiments, the refrigeration equipment comprises an air conditioner. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the technical solutions in the related art, the following will briefly introduce the drawings needed to be used in the embodiments or the related art description. Obviously, the drawings described below only show some of the embodiments of the present application, and are not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0046] Fig. 1 is a module schematic diagram of an embodiment of the power supply circuit of the present application;

[0047] Fig. 2 is a related SWISS-PFC topology diagram;

[0048] Fig. 3 is a specific circuit diagram of an embodiment of the power supply circuit of the present application;

[0049] Fig. 4 is a specific circuit diagram of another embodiment of the power supply circuit of the present application;

[0050] Fig. 5 is a state diagram of three-phase input voltage, midpoint switch and bus switch tube under PWM control of the related SWISS-PFC topology;

[0051] Fig. 6 is a state diagram of three-phase input voltage, midpoint switch and bus switch tube under PWM control of an embodiment of the power supply circuit of the present application;

[0052] Fig. 7 is a voltage stress waveform diagram of the midpoint switch of an embodiment of the power supply circuit of the present application;

[0053] Fig. 8 is a flowchart of an embodiment of the control method of the power supply circuit of the present application;

[0054] Fig. 9 is a flowchart of another embodiment of the control method of the power supply circuit of the present application;

[0055] Fig. 10 is a flowchart of still another embodiment of the control method of the power supply circuit of the present application.

[0056] Explanation of reference numerals: 10, power supply input end; 20, midpoint switch; 30, PFC diode; 40, bus switch tube; 50, switching circuit.

[0057] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0059] It should be noted that in this paper, step codes such as S100, S200, etc. are used, the purpose is to more clearly and briefly express the corresponding content, and does not constitute a substantial limitation on the order. The skilled person may perform S200 before performing S100, etc. in the specific implementation, but these should be within the scope of protection of the present application.

[0060] There are two kinds of traditional PFC schemes at present: one is a passive PFC topology, which needs to use a large inductance reactor to suppress current harmonics; the other is a boost type active PFC topology, and the bus voltage is generally greater than the peak value of the line voltage. In most operating conditions, the bus voltage demand is lower than the minimum voltage control value of the boost type active PFC topology. When the PFC topology is applied to the air conditioning scene, the selection of switching devices needs to consider the derating design, and usually a certain safety margin is left when selecting switching devices.

[0061] It can be understood that the SWISS-PFC (Switched-Mode Wide Input Range Soft-switching Power Factor Correction) topology is a soft-switching power factor correction circuit used to improve the power factor and efficiency of the power supply. SWISS-PFC usually includes a front-end rectifier filter circuit, a PFC circuit and a rear-end DC-DC converter. The rectifier filter circuit is used to rectify the alternating input voltage to direct current voltage. The PFC circuit is used to achieve power factor correction through soft switching technology, improve the input current waveform, and make it close to a sine wave, thereby improving the power factor. The rear-end DC-DC converter is used to convert the direct current voltage processed by the PFC circuit into a stable voltage suitable for the load according to the actual demand.

[0062] In the related PFC (Power Factor Correction) scheme, the bus voltage control value is much greater than the demand of the load on the bus voltage in most operating intervals, resulting in the need to select high-voltage switching devices for the inverter part of the three-phase air conditioner. If 800-1200V switching devices are selected, the hardware cost is increased, and in addition, the energy loss of high-voltage switching devices during operation is large. For the SWISS-PFC topology, although the voltage can be reduced, there are still deficiencies, for example, the voltage stress of the neutral line switch reaches a peak value at the switching moment, so the midpoint switch 20 still needs to use high-voltage switching devices, which fails to effectively reduce the cost and energy loss.

[0063] Therefore, with reference to FIG. 1, the present application proposes a power supply circuit, comprising:

[0064] The power supply input end 10 is used to access a three-phase alternating voltage.

[0065] a midpoint switch 20, a first end of the midpoint switch 20 being electrically connected with the power input end 10;

[0066] two PFC diodes 30, the two PFC diodes 30 being connected in series, a second end of the midpoint switch 20 being electrically connected with a common connection end of the two PFC diodes 30;

[0067] two bus switch tubes 40, each of the bus switch tubes 40 being electrically connected with the midpoint switch 20 and the PFC diodes 30 respectively;

[0068] a switch circuit 50, a first end of the switch circuit 50 being electrically connected with the power input end 10, a second end of the switch circuit 50 being electrically connected with the common connection end of the two PFC diodes 30; when the switch circuit 50 is closed, a path between the power input end 10 and the common connection end of the two PFC diodes 30 is turned on, so as to bypass the midpoint switch 20.

[0069] It should be noted that, with reference to FIG. 2, in the PFC topology of the related scheme, the bus switch tube 40 is usually used in cooperation with the midpoint switch 20 to ensure that the current flows in the expected manner. The control method of the related SWISS-PFC topology is as follows: first, the size of the three-phase alternating voltage input into the power input end 10 is sorted to select the midpoint switch 20 connected with the middle phase of the voltage to be turned on, that is, the voltage of the common connection end of the PFC diodes 30 (namely D1 and D2) is anchored at the middle phase voltage; at this time, the two bus switch tubes 40 Q1 and Q2 are alternately turned on in a cycle to form two loops: one loop is from the voltage maximum phase to the middle phase through the rear end inductor Ls and capacitor Cs; the other loop is from the voltage middle phase to the voltage minimum phase through the inductor Ls and the capacitor Cs. The time proportion of the two loops in a switching cycle can be calculated from the required control voltage and / or current, the three-phase input voltage (the three-phase alternating voltage input into the power input end 10), and then the duty cycle corresponding to the bus switch 40 Q1 and Q2 respectively is determined. FIG. 5 is a state diagram of the three-phase input voltage, the midpoint switch 20 and the bus switch tube 40 under the PWM control of the SWISS-PFC of the related scheme. Since the voltage stress after the midpoint switch 20 is turned off is the voltage difference between the phase and the middle phase, in the case of the phase voltage being AC 265V, the maximum voltage difference between the three-phase input voltage is close to 600V, and considering that there are high-frequency harmonics on the capacitors C1, C2 and C3 in the LC filter circuit electrically connected with the power input end 10, it is not appropriate to select a 650V switch device.

[0070] Referring to FIG. 3, the power input end 10 includes A, B, and C three-phase input ends, and the power circuit includes an LC filter circuit, a rectifier bridge composed of six diodes, a midpoint switch 20 S1, S2, and S3 connected to each phase, two bus switch tubes 40 (Q1 and Q2), two PFC diodes 30 (D1 and D2), and a switching circuit 50 S0. The rectifier bridge is a three-phase bridge circuit, each bridge arm of the three-phase bridge arm includes two series-connected diodes, one midpoint switch 20 is connected in series on one side of the midpoint of each bridge arm, the other side of the midpoint of each bridge arm is connected to the power input end 10 through the LC filter circuit, the midpoint switch 20 is connected to the common connection end of the two PFC diodes 30, and the PFC diode 30 is connected to an LC output circuit (including Ls and Cs). The first end of the switching circuit 50 (S0) is connected to the common connection point of the capacitors of the LC filter circuit, and the second end is connected to the common connection end of the PFC diode 30 (i.e., D1 and D2). The common connection end of the capacitors of the LC filter circuit is grounded. By turning on / off of Q1 and Q2, the current i s The three-phase input voltage is followed to obtain the sine control of the three-phase current, and then the power factor regulation is realized.

[0071] In the embodiment, the midpoint switch 20 and the switching circuit 50 can be realized by using a relay, a contactor, or the like, or by using an IGBT tube. In some embodiments, the switching circuit 50 includes a combination switch, and the combination switch includes two series-connected switch components, each of which is composed of a fast recovery diode and an IGBT tube in parallel.

[0072] The power circuit also includes a voltage detection circuit and a control circuit. The voltage detection circuit can be realized by using a Hall sensor, a capacitive voltage sensor, a resistance voltage divider, or the like. The control circuit can be realized by using a main controller, such as an MCU, a DSP (Digital Signal Process), an FPGA (Field Programmable Gate Array), a PLC, a SOC (System On Chip), or the like. The output end of the voltage detection circuit is electrically connected to the control circuit, and the control end of the control circuit is electrically connected to the controlled end of the switching circuit 50 and the controlled end of the midpoint switch 20. The voltage detection circuit is used to detect the three-phase alternating voltage input into the power input end 10 and output a corresponding voltage detection signal to the control circuit, so that the control circuit controls the on / off state of the midpoint switch 20 and the switching circuit 50 according to the received voltage detection signal.

[0073] Specifically, the embodiment can control the on / off of the midpoint switch 20 and the switching circuit 50 by the control circuit, so that the power supply circuit has two operation modes, the voltage detection circuit detects the three-phase alternating voltage connected to the power supply input end 10, and the control circuit outputs corresponding conduction signals / disconnection signals to the midpoint switch 20 and the switching circuit 50 according to the voltage detection signal, so as to switch the operation mode of the power supply circuit. For example, when the control circuit determines that the three-phase alternating voltage connected to the power supply input end 10 is less than the preset voltage threshold according to the voltage detection signal, the power supply circuit works in the first operation mode, the control circuit outputs the conduction signal to the midpoint switch 20 and outputs the disconnection signal to the switching circuit 50, that is, controls the midpoint switch 20 to be closed and controls the switching circuit 50 to be disconnected. When the control circuit determines that the three-phase alternating voltage connected to the power supply input end 10 is greater than the preset voltage threshold according to the voltage detection signal, the power supply circuit works in the second operation mode, at this time, the control circuit controls the switching circuit 50 to be closed and the path between the power supply input end 10 and the common end of the two PFC diodes 30 to be conducted, so as to bypass the midpoint switch 20, that is, the control circuit controls the midpoint switch 20 to be in the disconnected state. The preset voltage threshold is set in advance by the researchers. When the power supply circuit works in the first operation mode, the two bus switch tubes 40 are driven by PWM, and the duty cycle of the PWM driving signal is calculated according to the required control voltage and / or current and the three-phase input voltage, so as to ensure that the bus voltage can meet the system requirements. When the power supply circuit works in the second operation mode, the duty cycle of the PWM driving signal can be calculated according to the preset target modulation voltage, that is, the control circuit can control the bus switch 40 to be conducted / disconnected according to the calculated duty cycle, so that the bus voltage reaches the value of the target modulation voltage, and the control of the bus voltage is realized within the preset voltage range. In this way, when the voltage stress is high, the power supply circuit can work in the second operation mode, so as to control the bus voltage at a low voltage level. FIG. 6 is a switch state diagram of the midpoint return topology in the second operation mode, including the state diagrams of the three-phase input voltage, the midpoint switch 20 and the bus switch tube 40. FIG. 7 is a voltage stress waveform diagram of the midpoint switch 20. As shown in FIG. 7, the voltage stress of the midpoint switch 20 is below 600V, so the voltage resistance requirement of the switching device can be reduced from 800V-1200V to 650V compared with the related SWISS-PFC topology.

[0074] It should be noted that the value of the three-phase input voltage is: max(u max -u mid , u mid -u min ), wherein u max is the maximum phase voltage of the three-phase input voltage; u mid is the middle phase voltage of the three-phase input voltage u minThe minimum phase voltage of the three-phase input voltage. The three-phase input voltage takes the maximum voltage difference between the three-phase input voltage. For example, if the difference between the maximum phase voltage and the intermediate phase voltage is greater than the difference between the intermediate phase voltage and the minimum phase voltage, the three-phase input voltage is the difference between the maximum phase voltage and the intermediate phase voltage. The control circuit controls the on / off state of the switch circuit 50 and the midpoint switch 20 according to the value of the three-phase input voltage, that is, controls the power supply circuit to work in the first operating mode or the second operating mode, thereby realizing the control of the bus voltage.

[0075] In practical applications, the present application adds a switch circuit 50 based on the original SWISS-PFC, so that the power supply circuit switches between the first operating mode and the second operating mode, that is, when the voltage value of the three-phase input voltage is higher than the preset voltage threshold, the switch circuit 50 is turned on, and the midpoint switch 20 is turned off, so that the power supply circuit works in the second working mode, thereby ensuring that the voltage stress is within a controllable range, and the bus voltage can be dynamically adjusted according to the load demand, avoiding maintaining a higher bus voltage when a high voltage is not needed. In this way, the voltage stress borne by the switch device is reduced, allowing the use of lower voltage switch devices, reducing circuit design cost and energy loss.

[0076] In an air conditioning system, SWISS-PFC is usually closely related to rectifiers and inverters. The rectifier is responsible for converting alternating current into direct current, while the inverter converts direct current into alternating current to drive the motor or other loads. The role of SWISS-PFC is to improve the input current waveform of the rectifier to make it close to a sine wave, thereby improving the power factor, which can reduce the requirements on the inverter, because there is no longer a need to compensate for the nonlinear input current, thereby improving the efficiency of the entire system. The power supply circuit proposed in the present application can be applied to devices or power supply systems with PFC function, such as washing machines, refrigerators, air conditioners, UPS (Uninterruptible Power Supply), photovoltaic systems, external power supplies, etc.

[0077] With the above embodiment, after adding a switch circuit 50 to the original SWISS-PFC, the power supply circuit switches between the first operating mode and the second operating mode, i.e. when the voltage value of the three-phase input voltage is higher than the preset voltage threshold, the switch circuit 50 is turned on, and the midpoint switch 20 is turned off, so that the power supply circuit works in the second operating mode, thereby ensuring that the voltage stress is within a controllable range, reducing the voltage stress borne by the switching device, allowing the use of lower voltage switching devices. In this way, the bus voltage is set at a lower voltage level, and the inverter and rectifier part no longer needs to bear high voltage stress, so the high-voltage switching device required by the inverter and rectifier part can be replaced by a low-voltage (e.g. 650V) switching device. In this way, the use of low-voltage switching devices can reduce switching loss, improve the conversion efficiency of the refrigeration equipment, and reduce the design cost of the circuit.

[0078] In some embodiments of the present application, the power supply circuit has a first operating mode and a second operating mode;

[0079] In the first operating mode, the midpoint switch 20 is in the on state, and the switch circuit 50 is in the off state;

[0080] In the second operating mode, the midpoint switch 20 is in the off state, and the switch circuit 50 is in the on state.

[0081] In some embodiments, in the second operating mode, one of the two bus switch tubes 40 is turned on / off with a preset first duty cycle; the other of the two bus switch tubes 40 is turned on / off with a preset second duty cycle.

[0082] With the above embodiment, the bus switch tubes 40Q1 and Q2 in the power supply circuit are alternately turned on, and under PWM (Pulse Width Modulation) control, the current is adjusted according to the duty cycle of the PWM drive signal, thereby controlling the bus voltage. The duty cycle of the PWM drive signal determines the level of the bus voltage. In the first operating mode and the second operating mode, the duty cycles corresponding to Q1 and Q2 are adjusted according to different control logics, thereby controlling the bus voltage within the preset voltage range.

[0083] In the first operating mode, the control circuit controls the switch circuit 50 (So) to be open, and controls the midpoint switch 20 S1 / S2 / S3 to be closed, and the bus switch tube 40 Q1 and Q2 are controlled by PWM driving respectively. The duty cycle of the PWM driving signal is calculated according to the required control voltage and / or current, three-phase input voltage. The control circuit outputs the corresponding PWM driving signal to the bus switch tube 40, so that the two bus switch tubes 40 are alternately turned on. Among them, the required control voltage is the target voltage of the power supply system where the power supply circuit is located, the required control current is the target current of the power supply system where the power supply circuit is located, and the three-phase input voltage is the three-phase alternating voltage connected to the power supply input end 10. The duty cycle of the PWM driving signal determines the opening time and closing time of the bus switch tube 40 Q1 and Q2, and further affects the output voltage and current of the power supply system. Specifically, the target voltage and target current can be set according to the demand of the load or the specification of the power supply system, so that the duty cycle of the PWM can be calculated. In the second operating mode, the control circuit controls the switch circuit 50 (So) to be closed, and controls the midpoint switch 20 S1 / S2 / S3 to be open. At this time, the bus switch tube 40 Q1 and Q2 are still controlled by PWM driving, but the duty cycle of the PWM is calculated according to the target modulation voltage. The control circuit controls one of the bus switch tubes 40 to be turned on / off with a preset first duty cycle; controls the other of the two bus switch tubes 40 to be turned on / off with a preset second duty cycle. Taking the bus switch tube 40 Q1 turned on / off with a preset first duty cycle and the bus switch tube 40 Q2 turned on / off with a preset second duty cycle as an example for description. When the rear-end load is stable, the target modulation voltage is calculated according to the following formula: md = u dc + i s *R s ;

[0084] The duty cycle corresponding to the bus switch tube 40 Q1 and Q2 is calculated according to the following formula: md = d1u max -d2*u min ;

[0085] Among them, V md is the target modulation voltage, u dc is the bus voltage, i s is the bus inductance current, R s is the path resistance; d1 is the preset first duty cycle; d2 is the preset second duty cycle; u max is the maximum phase voltage of the three-phase input voltage; u min is the minimum phase voltage of the three-phase input voltage.

[0086] In the present embodiment, when the power supply circuit operates in the first operation mode, the duty ratio of the PWM driving signal is calculated according to the target voltage and the target current, and the three-phase input voltage, so as to ensure that the bus voltage can meet the demand of the power supply system. This is suitable for the case where the voltage stress is low, in which case, the switching tube can use a low-voltage switching device and will not be damaged; when the power supply circuit operates in the second operation mode, the duty ratio of the PWM driving signal is calculated based on the target modulation voltage V md , and the purpose is to control the bus voltage at a low voltage level (below 450V) to reduce the voltage stress. It should be noted that in the first operation mode, the voltage stress is low, and a switching device with a small voltage resistance value can be used without reducing the voltage stress. In the second operation mode, the bus voltage is controlled within a preset voltage range to reduce the voltage stress, and a switching device with a low voltage resistance value can also be used.

[0087] Through the above setting, the power supply circuit proposed in the present application can reduce the voltage resistance requirement of the switching device by changing the operation mode of the power supply circuit, so as to select a switching device with a lower voltage resistance and reduce the hardware cost of the power supply circuit. Through the switching between the first operation mode and the second operation mode, different power supply demands can be better adapted to, and the stability and reliability of the power supply circuit can be improved, thereby improving the safety and reliability of the refrigeration equipment.

[0088] In some embodiments, when the three-phase input voltage connected to the power supply input end 10 is greater than a preset first voltage threshold, the power supply circuit operates in the second operation mode; when the three-phase input voltage connected to the power supply input end 10 is less than the preset first voltage threshold, the power supply circuit operates in the first operation mode.

[0089] In combination with the above embodiment, the on / off of the switching circuit 50 and the midpoint switch 20 is determined according to the value of the three-phase input voltage, the power supply circuit is controlled to operate in the first operation mode or the second operation mode, and the control of the bus voltage is realized.

[0090] In the present embodiment, the operation mode of the power supply circuit is determined according to the three-phase input voltage in one power supply cycle, that is, the value of the three-phase input voltage is taken as U X , wherein U X = max(u max -u mid , u mid -u min ), at this time, when U X exceeds a preset first voltage threshold (for example, 430V), the switching circuit 50 is turned on, the midpoint switch 20 is turned off, and the power supply circuit operates in the second operation mode; when U XWhen the voltage is less than or equal to a preset first voltage threshold (e.g., 430V), the control circuit controls the switch circuit 50 to open and the control midpoint switch 20 to open, causing the power supply circuit to operate in the first operating mode. It should be noted that the operating mode can be switched multiple times within one power cycle (which can be understood as real-time mode adjustment), making it suitable for semiconductor devices; for example, with a three-phase AC 265V input, the operating mode is adjusted in real-time according to the voltage conditions, and this adjustment will occur multiple times within one power cycle.

[0091] In some embodiments, when the three-phase input voltage connected to the power input terminal 10 is greater than a preset first voltage threshold, the power supply circuit operates in a second operating mode; when the three-phase input voltage connected to the power input terminal 10 is less than a preset second voltage threshold, the power supply circuit operates in a first operating mode.

[0092] The preset second voltage threshold is less than the preset first voltage threshold.

[0093] In this embodiment, when U X When the voltage exceeds the preset first threshold, the switching circuit 50 is turned on, the midpoint switch 20 is turned off, and the power supply circuit operates in the second operating mode; when U X When the voltage drops below a preset second voltage threshold, switching circuit 50 is disconnected, midpoint switch 20 is turned on, and the power supply circuit operates in the first operating mode. For example, the preset first voltage threshold is 430V, and the preset second voltage threshold is 400V. It should be noted that the preset second voltage threshold is lower than the preset first voltage threshold. The preset first and second voltage thresholds are set because the on-time of midpoint switch 20 and / or switching circuit 50 should be relatively long and cannot be ignored. If the switching signal (on or off signal) output by the control circuit is too fast, midpoint switch 20 and / or switching circuit 50 may remain in an on or off state continuously. Due to the frequent triggering of the switching action of midpoint switch 20 and / or switching circuit 50 between on and off, the continuous operating time of the power supply circuit in the first or second operating mode is short, resulting in ineffective control of the bus voltage. This improves the reliability of the power supply circuit operation.

[0094] It should be noted that the peak values ​​of the three-phase input phase voltages can reflect voltage fluctuations originating from the power grid. Under normal circumstances, the voltage fluctuation range of the power grid is very small, and the changes in the peak values ​​of the three-phase input phase voltages are also small. In this case, the peak values ​​of the three-phase input phase voltages can be used as a voltage judgment condition. The sum of the squares of the three-phase voltages is: 1.5V m *V m =V A *V A +V B *V B +V C *VC ;

[0095] wherein, V A is the peak value of the A-phase voltage, V B is the peak value of the B-phase voltage, V C is the peak value of the C-phase voltage, V m is the average value of the three-phase voltage. Under a stable power grid, the average value of the three-phase voltage changes little, and the average value of the stable three-phase voltage calculated by using the sum of squares relationship formula of the three-phase voltage is more conducive to calculation, which can avoid errors caused by power grid voltage fluctuation, thereby improving the calculation accuracy and further improving the reliability of the power supply circuit operation.

[0096] In some embodiments, in order to ensure that the working time of the power supply circuit in the first operating mode and / or the second operating mode reaches the effective time, i.e. within the effective time, the power supply circuit can switch between the first operating mode and the second operating mode to control the bus voltage, thereby reducing the voltage stress borne by the switching device.

[0097] In the embodiment, when the control circuit determines that the maximum voltage difference U X between the three-phase input voltages exceeds the preset first voltage threshold value according to the voltage detection signal, the control switch circuit 50 is turned on, and the midpoint switch 20 is turned off, so that the power supply circuit operates in the second operating mode; when the control circuit determines that U X is continuously lower than the preset second voltage threshold value within the first time length, the control switch circuit 50 is turned off, and the midpoint switch 20 is turned on, so that the power supply circuit is switched from the second operating mode to the first operating mode. The setting of the first time length can ensure the rapid entry and slow exit of the second operating mode. For example, when the preset first voltage threshold value is 430V and the preset second voltage threshold value is 400V, the first time length is 3S, if U X exceeds 430V, the control switch circuit 50 is turned on, the midpoint switch 20 is turned off, and the power supply circuit operates in the second operating mode; only when U X is continuously less than 400V for 3S, the control switch circuit 50 is switched from the on state to the off state, the midpoint switch 20 is switched from the off state to the on state, and the power supply circuit is switched from the second operating mode to the first operating mode. If U X is continuously less than 400V for 2S, the control switch circuit 50 and the midpoint switch 20 maintain the current on / off state, and the power supply circuit is still in the second operating mode. That is, at this time, the operating mode of the power supply circuit is not adjusted in real time, and multiple adjustments cannot be completed within one power supply period. When the three-phase AC 265V input is always in the second operating mode. Until U XThe control device controls the power supply circuit to switch from the second operation mode to the first operation mode only when the condition of being lower than 400V and the duration exceeding the first time length (for example, 3S) is met. In this way, the bus voltage is ensured to be within the preset voltage range as much as possible, so as to reduce the voltage stress of the switching device, reduce the loss of the switching device, and prolong the service life of the switching device.

[0098] In some embodiments of the present application, when switching between the first operation mode and the second operation mode, the power supply circuit is further provided with a dead time range, in which the switching circuit 50 and the midpoint switch 20 are both in an off state.

[0099] Specifically, the dead time range is the time period when the switching circuit 50 and the midpoint switch 20 are both in an off state when the power supply circuit switches between the first operation mode and the second operation mode. In the dead time range, the bidirectional switch So (switching circuit 50) and the midpoint switch 20 S1 / S2 / S3 are all not conducting. The dead time range is set to avoid the phenomenon that the switching device is conducting at the same time when switching between the two operation modes, so as to cause a transient short circuit of the power supply circuit. In the present embodiment, the dead time range is greater than the absolute value of the difference between the off time and the on time of the switching device, so as to ensure that the switching device has enough off time when switching between the two operation modes, thereby avoiding the phenomenon of transient short circuit of the power supply circuit. In actual application, the size of the dead time range can be adjusted according to the specific situation of the power supply circuit. For example, in the case of a large power of the power supply circuit, the current and voltage of the switching device will also increase accordingly. If the dead time range is small, it may cause the switching device to conduct at the same time, thereby causing a transient short circuit phenomenon, and further causing the current and voltage of the power supply circuit to increase instantaneously, which may damage the power supply circuit. Therefore, the dead time range should be increased accordingly to ensure the safety and stability of the power supply circuit.

[0100] It can be understood that the voltage at the common connection end of each capacitor in the LC filter circuit will change due to the influence of the rear-end switching device, and at this time the voltage at the common connection end of the PFC diode 30 (i.e. D1 and D2) will also fluctuate.

[0101] In some embodiments, the power supply circuit further comprises a neutral line, and the switching circuit 50 is connected in series between the neutral line and the common connection end of the two PFC diodes 30.

[0102] In the embodiment, referring to FIG. 4, the first end of the switching circuit 50S0 is connected to the common connection end of the capacitors in the LC filter circuit, the connection end of the switching circuit 50S0 and the LC filter circuit is connected to the neutral line N, and the second end of the switching circuit 50S0 is connected to the common connection end of the PFC diodes 30 (i.e. D1 and D2). At this time, the voltage at the common connection end of the capacitors in the LC filter circuit will not change due to the influence of the back-end switching device. In this way, even if the switching device is turned on or turned off, the voltage at the common connection end of the capacitors in the LC filter circuit will not be affected, thereby keeping the output voltage of the power supply circuit stable. In addition, since the switching circuit 50S0 is connected to the neutral line N, the voltage of the switching circuit 50S0 is also constrained by the neutral line N and will not change with the state of the switching device, further improving the stability of the power supply circuit.

[0103] The present application also provides a control method of a power supply circuit, which is based on the power supply circuit described in the above embodiments. Referring to FIG. 8, the control method of the power supply circuit comprises the following steps:

[0104] In step S100, a maximum voltage difference between the three-phase input voltages is obtained.

[0105] According to the above embodiments, since the voltage stress of the midpoint switch 20 after being turned off is the voltage difference between the phase and the intermediate phase, the three-phase input voltage can be the maximum voltage difference between the three-phase input voltages, and then the voltage stress borne by the switching device can be determined.

[0106] In some embodiments, referring to FIG. 10, step S100 specifically comprises the following steps:

[0107] In step S110, the maximum phase voltage, the intermediate phase voltage and the minimum phase voltage of the three-phase input voltages are obtained.

[0108] In step S120, the difference between the maximum phase voltage and the intermediate phase voltage is calculated as a first voltage difference, and the difference between the intermediate phase voltage and the minimum phase voltage is calculated as a second voltage difference.

[0109] In step S130, the maximum value of the first voltage difference and the second voltage difference is obtained as the maximum voltage difference between the three-phase input voltages.

[0110] Specifically, the maximum phase voltage u of the three-phase input voltages is obtained first, max the intermediate phase voltage u mid , and the minimum phase voltage u min . Then, the difference between the maximum phase voltage and the intermediate phase voltage is calculated as a first voltage difference u max -u mid , and the difference between the intermediate phase voltage and the minimum phase voltage is calculated as a second voltage difference u mid-u min ; then compare u max -u mid and u mid -u min , and take the larger value as the maximum voltage difference between the three-phase input voltages. For example, if the first voltage difference value u max -u mid is greater than the second voltage difference value u mid -u min , the maximum voltage difference between the three-phase input voltages is the difference between the maximum phase voltage and the intermediate phase voltage (the first voltage difference value), so that the control device determines the working mode of the power supply circuit according to the size relationship between the first voltage difference value and the preset first voltage threshold.

[0111] Step S200: determining the working mode of the power supply circuit according to the size relationship between the maximum voltage difference in the three-phase input voltages and the preset first voltage threshold.

[0112] In some embodiments, referring to FIG. 9, the working mode includes a first running mode and a second running mode; and step S200 specifically includes:

[0113] Step S210: determining the working mode of the power supply circuit according to the size relationship between the maximum voltage difference in the three-phase input voltages and the preset first voltage threshold specifically includes:

[0114] Step S220: when the maximum voltage difference in the three-phase input voltages is less than or equal to the preset first voltage threshold, determining the working mode of the power supply circuit as the first working mode; in the first running mode, the midpoint switch 20 is in the on state, and the switch circuit 50 is in the off state.

[0115] Step S230: when the maximum voltage difference in the three-phase input voltages is greater than the preset first voltage threshold, determining the working mode of the power supply circuit as the second working mode; in the second running mode, the midpoint switch 20 is in the off state, and the switch circuit 50 is in the on state.

[0116] In combination with the above embodiments, the power supply circuit includes the first running mode and the second running mode. After obtaining the maximum voltage difference in the three-phase input voltages, the power supply circuit needs to be controlled to work in the first running mode or the second running mode according to the size relationship between the maximum voltage difference in the three-phase input voltages and the preset first voltage threshold, so as to realize the control of the bus voltage.

[0117] Specifically, taking the first voltage threshold of 430V as an example, the values of the three-phase input voltages are: max(u max -u mid , umid -u min ), where u max The maximum phase voltage of the three-phase input voltage; u mid The intermediate phase voltage u of the three-phase input voltage min This is the minimum phase voltage of the three-phase input voltage. If the difference between the maximum phase voltage and the intermediate phase voltage is u... max -u mid The difference u between the intermediate phase voltage and the minimum phase voltage mid -u min The maximum value is 600V, which is greater than the preset first voltage threshold of 430V. At this time, the power supply circuit operates in the second operating mode, the switching circuit 50 (So) is turned on, and the midpoint switches 20S1 / S2 / S3 are turned off. If the difference between the maximum phase voltage and the intermediate phase voltage is u... max -u mid The difference u between the intermediate phase voltage and the minimum phase voltage mid -u min The maximum value is 400V, which is less than the preset first voltage threshold of 430V. At this time, the power supply circuit operates in the first operating mode, switch circuit 50(So) is open, and the midpoint switches 20S1 / S2 / S3 are closed. It should be noted that in the first operating mode, the voltage stress is low, and there is no need to reduce the voltage stress; switching devices with lower withstand voltage values ​​can be used. In the second operating mode, by controlling the bus voltage within the preset voltage range to reduce voltage stress, switching devices with lower withstand voltage values ​​can also be used.

[0118] Step S300: Control the on / off state of the midpoint switch 20 and the switch circuit 50 according to the determined working mode.

[0119] In this embodiment, the power supply circuit control method of this application can be applied to a control device for refrigeration equipment. For example, the control device integrates a memory for storing the control program of the power supply circuit of this application, and a processor for executing the control program of the power supply circuit of this application. The control device can be implemented using a main controller, such as an MCU, DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), PLC, or SOC (System on Chip). Refrigeration equipment includes refrigerators, air conditioners, freezers, etc.

[0120] Based on the above embodiments, bus switch transistors 40Q1 and Q2 are driven and controlled by PWM, and the duty cycle of the PWM is calculated from the target modulation voltage. One of the bus switch transistors 40 is turned on / off with a preset first duty cycle; the other of the two bus switch transistors 40 is turned on / off with a preset second duty cycle. The following explanation uses bus switch transistor 40Q1 being turned on / off with the preset first duty cycle and bus switch transistor 40Q2 being turned on / off with the preset second duty cycle as an example. When the downstream load is stable, the target modulation voltage is calculated by the following formula: V md =u dc +i s *R s ;

[0121] The duty cycles of bus switch transistors 40Q1 and Q2 are calculated using the following formula: V md =d1u max -d2*u min ;

[0122] Among them, V md For the target modulation voltage, u dc For the bus voltage, i s R is the bus inductance current. s d1 is the circuit resistance; d2 is the preset first duty cycle; d2 is the preset second duty cycle; u max The maximum phase voltage of the three-phase input voltage; u min It is the minimum phase voltage of the three-phase input voltage.

[0123] In this embodiment, when the difference between the maximum phase voltage and the intermediate phase voltage is u max -u mid The difference u between the intermediate phase voltage and the minimum phase voltage mid -u min When the maximum value in the voltage range exceeds the preset first voltage threshold, the control device determines that the power supply circuit should operate in the second operating mode, i.e., the control switch circuit 50(So) is turned on, and the midpoint switches 20S1 / S2 / S3 are turned off. At this time, the duty cycle of the PWM drive signal is based on the target modulation voltage V. md The calculation aims to control the bus voltage at a lower level (below 450V) to reduce voltage stress. The difference between the maximum phase voltage and the intermediate phase voltage, u... max -u mid The difference u between the intermediate phase voltage and the minimum phase voltage mid -u minWhen the maximum value of the voltage difference in the three-phase input voltage is less than the preset first voltage threshold, the control device determines that the power supply circuit should work in the first operation mode, that is, the switch circuit 50 (So) is controlled to be turned off and the midpoint switch 20 S1 / S2 / S3 is controlled to be turned on. At this time, the duty cycle of the PWM drive signal of the bus switch tube 40 Q1 and Q2 is calculated according to the target voltage and the target current and the three-phase input voltage, so as to ensure that the bus voltage can meet the demand of the power supply system. It is suitable for the case where the voltage stress is low, and the switch tube can use a low-voltage switch device and will not damage the switch device. In this way, the midpoint switch 20, the rectifier, the inverter and other switch devices can use switch devices with low voltage requirements, thereby reducing the cost of circuit design.

[0124] Through the above steps, the control circuit controls the power supply circuit to switch between the first operation mode and the second operation mode, that is, when the voltage value of the three-phase input voltage is higher than the first preset voltage threshold, the control device controls the switch circuit 50 to be turned on and controls the midpoint switch 20 to be turned off, so that the power supply circuit works in the second operation mode, thereby ensuring that the voltage stress is within a controllable range, dynamically adjusting the bus voltage according to the load demand, and avoiding maintaining a high bus voltage when a high voltage is not needed. In this way, the voltage stress borne by the switch device is reduced, allowing the use of a switch device with a lower voltage value, thereby reducing the cost of circuit design and energy loss.

[0125] In some embodiments, the step 200 specifically includes:

[0126] When the maximum value of the voltage difference in the three-phase input voltage is less than the preset second voltage threshold, the working mode of the power supply circuit is determined to be the first working mode.

[0127] The preset second voltage threshold is less than the preset first voltage threshold.

[0128] In the embodiment, when the maximum value of the voltage difference U X between the three-phase input voltage is greater than the preset first voltage threshold, the control device controls the switch circuit 50 to be turned on and controls the midpoint switch 20 to be turned off, so that the power supply circuit works in the second operation mode; when U X is less than the preset second voltage threshold, the control device controls the switch circuit 50 to be turned off and controls the midpoint switch 20 to be turned on, so that the power supply circuit works in the first operation mode. For example, the preset first voltage threshold is 430V and the preset second voltage threshold is 400V. When U X is greater than 430V, the control device controls the power supply circuit to work in the second operation mode, and when U X is less than 400V, the control device controls the power supply circuit to work in the first operation mode.

[0129] It should be noted that the preset second voltage threshold is less than the preset first voltage threshold, and the preset first voltage threshold and the preset second voltage threshold are set because the on time of the midpoint switch 20 and / or the switch circuit 50 should be relatively long and cannot be ignored. If the switch signal is too fast, the midpoint switch 20 and / or the switch circuit 50 can always be in the on or off state, and does not act according to the control signal, that is, the switching action between the on / off of the midpoint switch 20 and / or the switch circuit 50 is avoided, so that the power supply circuit works in the first operating mode or the second operating mode for a relatively short time, resulting in that the size of the bus voltage is not effectively controlled. In this way, the reliability of the power supply circuit is improved.

[0130] In order to ensure that the working time of the power supply circuit in the first operating mode and / or the second operating mode reaches an effective time, that is, within the effective time, the power supply circuit can be switched between the first operating mode and the second operating mode to control the bus voltage, thereby reducing the voltage stress borne by the switching device.

[0131] In some embodiments, the step 200 specifically comprises:

[0132] When the maximum value of the voltage difference in the three-phase input voltage is less than the preset second voltage threshold within the preset first time length, it is determined that the working mode of the power supply circuit is the first working mode.

[0133] The preset second voltage threshold is less than the preset first voltage threshold.

[0134] In this embodiment, when the maximum value of the voltage difference U X between the three-phase input voltages exceeds the preset first voltage threshold, the control device controls the switch circuit 50 to be on, and controls the midpoint switch 20 to be off, so that the power supply circuit works in the second operating mode; when U X between the three-phase input voltages is continuously less than the preset second voltage threshold within the first time length, the control device controls the switch circuit 50 to be off, and controls the midpoint switch 20 to be on, so that the power supply circuit is switched from the second operating mode to the first operating mode. The setting of the first time length can ensure the fast entry and slow exit of the second operating mode. For example, taking the preset first voltage threshold as 430V, the preset second voltage threshold as 400V, and the first time length as 3S as an example, if U X is greater than 430V, the switch circuit 50 S0 is on, and the midpoint switch 20 S1 / S2 / S3 is off, so that the power supply circuit works in the second operating mode; only when U X is continuously less than 400V within 3S, the control device controls the switch circuit 50 to be switched from the on state to the off state, and controls the midpoint switch 20 to be switched from the off state to the on state, so that the power supply circuit is switched from the second operating mode to the first operating mode. If U XWhen the voltage is less than 400V for 2S, the control device controls the switching circuit 50 and the midpoint switch 20 to maintain the current on / off state (the switching circuit 50 is on, and the midpoint switch 20 is off), and the power supply circuit is still in the second operation mode. At this time, the control device does not adjust the operation mode of the power supply circuit in real time, and cannot complete multiple adjustments in one power supply cycle. When the three-phase AC 265V input is always in the second operation mode. Until U X When the voltage is less than 400V for 2S, the control device controls the switching circuit 50 and the midpoint switch 20 to maintain the current on / off state (the switching circuit 50 is on, and the midpoint switch 20 is off), and the power supply circuit is still in the second operation mode. At this time, the control device does not adjust the operation mode of the power supply circuit in real time, and cannot complete multiple adjustments in one power supply cycle. When the three-phase AC 265V input is always in the second operation mode. Until U

[0135] In this way, the bus voltage is ensured to be within the preset voltage range as much as possible, thereby reducing the voltage stress of the switching device, reducing the loss of the switching device, and prolonging the service life of the switching device.

[0136] It is worth noting that the control method of the power supply circuit of the present application is based on the above-mentioned power supply circuit, so the embodiments of the control method of the power supply circuit of the present application include all the technical solutions of all the embodiments of the above-mentioned power supply circuit, and the technical effects achieved are also completely the same, which will not be repeated here.

[0137] The present application also proposes a control device, which comprises a memory, a processor and a power supply circuit control program stored in the memory and executable on the processor, and the power supply circuit control program is configured to implement the steps of any one of the above-mentioned power supply circuit control methods.

[0138] It is worth noting that the control device of the present application is based on the control method of the above-mentioned power supply circuit, so the embodiments of the control device of the present application include all the technical solutions of all the embodiments of the control method of the above-mentioned power supply circuit, and the technical effects achieved are also completely the same, which will not be repeated here.

[0139] The present application also proposes a refrigeration equipment, which comprises the power supply circuit according to any one of the above-mentioned embodiments, and / or comprises the control device.

[0140] In some embodiments, the refrigeration equipment comprises an air conditioner. The load characteristics of the air conditioner are nonlinear, which can cause current waveform distortion and affect the quality of the power grid. Therefore, it is necessary to perform power factor correction by the power supply circuit proposed in the present application to adjust the current waveform to be close to a sine wave, thereby improving the power supply efficiency, reducing energy waste, and improving the quality of the power grid. In addition, the stability of the air conditioner can be improved, the service life can be prolonged, and the maintenance cost can be reduced. For the air conditioner, the voltage withstand requirement of the switching device can be reduced by the above-mentioned power supply circuit and the control device, so that a switching device with a smaller voltage withstand value can be selected, thereby reducing the cost.

[0141] It is worth noting that, since the refrigeration equipment of the present application comprises the power supply circuit and / or the control device as described above, the embodiments of the refrigeration equipment of the present application comprise all the technical solutions of all the embodiments of the power supply circuit and / or the control device, and the technical effects achieved are also completely the same, which will not be described here.

[0142] The above is only optional embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent mechanism transformation made by using the content of the present application specification and drawings, or direct / indirect application in other related technical fields under the application concept of the present application is included in the patent protection scope of the present application.

Claims

1. A power supply circuit, wherein, The power supply circuit comprises: a power input end for connecting to a three-phase alternating voltage; a midpoint switch, a first end of the midpoint switch being electrically connected to the power input end; two PFC diodes, the two PFC diodes being connected in series, a second end of the midpoint switch being electrically connected to a common connection end of the two PFC diodes; two bus switch tubes, each of the bus switch tubes being electrically connected to the midpoint switch and the PFC diodes; a switch circuit, a first end of the switch circuit being electrically connected to the power input end, a second end of the switch circuit being electrically connected to the common connection end of the two PFC diodes, the switch circuit, when closed, conducting a path between the power input end and the common connection end of the two PFC diodes to bypass the midpoint switch.

2. The power supply circuit of claim 1, wherein, The power supply circuit has a first operation mode and a second operation mode; in the first operation mode, the midpoint switch is in a conducting state, and the switch circuit is in a disconnected state; in the second operation mode, the midpoint switch is in a disconnected state, and the switch circuit is in a conducting state.

3. The power supply circuit of claim 2, wherein, in the second operation mode, one of the two bus switch tubes is conducting / discharging at a preset first duty ratio, and the other of the two bus switch tubes is conducting / discharging at a preset second duty ratio.

4. The power supply circuit of claim 3, wherein, The preset first duty cycle and the preset second duty cycle are calculated by the following equations: md = u dc + i s * R s ; V md = d1u max - d2*u min ; wherein V md is the target modulation voltage, u dc is the bus voltage, i s is the bus inductor current, R s is the path resistance; d1 is a preset first duty ratio; d2 is a preset second duty ratio; u max is the maximum phase voltage of the three-phase input voltage; u min is the minimum phase voltage of the three-phase input voltage.

5. A power supply circuit as claimed in any one of claims 2 to 4, wherein, When the three-phase input voltage connected to the power input end is greater than a preset first voltage threshold, the power supply circuit works in the second working mode; when the three-phase input voltage connected to the power input end is less than the preset first voltage threshold, the power supply circuit works in the first working mode.

6. A power supply circuit as claimed in any one of claims 2 to 5, wherein, When the three-phase input voltage connected to the power input end is greater than a preset first voltage threshold, the power supply circuit works in the second working mode; when the three-phase input voltage connected to the power input end is less than a preset second voltage threshold, the power supply circuit works in the first working mode; wherein the preset second voltage threshold is less than the preset first voltage threshold.

7. A power supply circuit as claimed in any one of claims 2 to 6, wherein, When switching between the first operation mode and the second operation mode, the power supply circuit further has a dead time range, in which the switch circuit and the midpoint switch are both in a disconnected state.

8. The power supply circuit of any one of claims 1 to 7, wherein, The power supply circuit further comprises a neutral line, and the switch circuit is connected in series between the neutral line and the common connection end of the two PFC diodes.

9. A control method of a power supply circuit, wherein, The control method of the power supply circuit is based on the power supply circuit as claimed in any one of claims 1 to 8, and the control method of the power supply circuit comprises: obtaining a maximum voltage difference between three-phase input voltages; determining a working mode of the power supply circuit according to a size relationship between the maximum voltage difference and a preset first voltage threshold in the three-phase input voltages; controlling the on / off state of the midpoint switch and the switch circuit according to the determined working mode.

10. The control method of the power supply circuit according to claim 9, wherein The working mode comprises a first operation mode and a second operation mode; determining a working mode of the power supply circuit according to a size relationship between the maximum voltage difference and a preset first voltage threshold in the three-phase input voltages specifically comprises: determining the working mode of the power supply circuit as a first working mode when the maximum voltage difference in the three-phase input voltage is less than or equal to a preset first voltage threshold; in the first working mode, the midpoint switch is in a conducting state, and the switch circuit is in a disconnected state; determining the working mode of the power supply circuit as a second working mode when the maximum voltage difference in the three-phase input voltage is greater than the preset first voltage threshold; in the second working mode, the midpoint switch is in a disconnected state, and the switch circuit is in a conducting state.

11. The control method of the power supply circuit according to claim 9, wherein The step of obtaining the maximum voltage difference between the three-phase input voltage includes: obtaining a maximum phase voltage, an intermediate phase voltage and a minimum phase voltage of the three-phase input voltage; calculating a difference between the maximum phase voltage and the intermediate phase voltage as a first voltage difference, and calculating a difference between the intermediate phase voltage and the minimum phase voltage as a second voltage difference; obtaining a maximum value between the first voltage difference and the second voltage difference as the maximum voltage difference between the three-phase input voltage.

12. The control method of the power supply circuit according to claim 9 or 10, wherein The step of determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference in the three-phase input voltage is less than or equal to the preset first voltage threshold specifically includes: determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference in the three-phase input voltage is less than a preset second voltage threshold; wherein the preset second voltage threshold is less than the preset first voltage threshold.

13. The control method of the power supply circuit according to claim 9 or 10, wherein The step of determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference in the three-phase input voltage is less than or equal to the preset first voltage threshold specifically includes: determining the working mode of the power supply circuit as the first working mode when the maximum voltage difference in the three-phase input voltage is less than the preset second voltage threshold within a preset first time length; wherein the preset second voltage threshold is less than the preset first voltage threshold.

14. A control device, wherein, The control device includes a memory, a processor, and a power supply circuit control program stored on the memory and executable on the processor, and the power supply circuit control program is configured to implement the steps of the power supply circuit control method according to any one of claims 9 to 13.

15. A refrigeration appliance, wherein, The refrigeration equipment includes the power supply circuit according to any one of claims 1 to 8, and / or includes the control device according to claim 14.

16. The refrigeration appliance of claim 15, wherein, The refrigeration equipment includes an air conditioner. The refrigeration equipment includes an air conditioner.

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