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

Abstract

A power supply circuit and a control method and apparatus therefor, and a refrigeration device. The power supply circuit comprises a power supply input end (10), an input filter circuit (20), a midpoint switch (30), two PFC diodes (40), two bus switch transistors (50), and a soft-start circuit (60); the input filter circuit (20) is electrically connected to the power input end (10); a first end of the midpoint switch (30) is electrically connected to the input filter circuit (20); the two PFC diodes (40) are connected in series, and a second end of the midpoint switch (30) is electrically connected to a common connection end of the two PFC diodes (40); each bus switch transistor (50) is separately electrically connected to the midpoint switch (30) and the corresponding PFC diode (40); the soft-start circuit (60) is electrically connected to the input filter circuit (20); and when the voltage of the input filter circuit (20) is less than a three-phase alternating current voltage, the soft-start circuit (60) limits the current flowing into the input filter circuit (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. 202411364433.5, filed on September 27, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

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

[0004] The traditional step-down three-phase PFC topology adopts the form of a current inverter, and is equipped with an LC filter circuit at the front end. When connected to the power grid, the inductive current and the capacitive voltage of the LC filter circuit will experience severe oscillation at the resonance frequency point, and the oscillation amplitude of the voltage may reach twice the input voltage, reducing the reliability of the electrical control. Therefore, it is usually necessary to use front-end devices with larger voltage and current resistance specifications, increasing the cost and volume. SUMMARY

[0005] The main purpose of the present application is to provide a power supply circuit, a control method and device thereof, and a refrigeration equipment, aiming to improve the problem of oscillation during power-on start of the power supply circuit, improve the reliability and stability of the power supply circuit operation, and reduce the circuit design cost and volume.

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

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

[0008] an input filter circuit electrically connected to the power input end for filtering and outputting the three-phase alternating voltage;

[0009] a midpoint switch having a first end electrically connected to the input filter circuit;

[0010] two PFC diodes connected in series, and a second end of the midpoint switch being electrically connected to a common connection end of the two PFC diodes;

[0011] two bus switch tubes, each of which is electrically connected to the midpoint switch and the PFC diode;

[0012] a slow-start circuit electrically connected to the input filter circuit;

[0013] The slow start circuit is capable of limiting the current flowing into the input filter circuit when the voltage of the input filter circuit is less than the three-phase alternating voltage connected to the power input end.

[0014] In some embodiments, the slow start circuit comprises a current limiting mode and a start mode.

[0015] When the voltage of the input filter circuit is less than the three-phase alternating voltage connected to the power input end, the slow start circuit is in the current limiting mode, in which the slow start circuit connects the power circuit, the voltage across the input filter circuit gradually increases, and the current flowing into the input filter circuit gradually decreases.

[0016] When the voltage of the input filter circuit reaches the three-phase alternating voltage connected to the power input end, the slow start circuit is in the start mode, in which the slow start circuit disconnects the power circuit, and the charging time of the input filter circuit is reduced to accelerate the start speed of the power circuit.

[0017] In some embodiments, the midpoint switch is closed after the slow start circuit is in the start mode and runs for a preset time length.

[0018] In some embodiments, when the voltage of the input filter circuit reaches the three-phase alternating voltage connected to the power input end, and the bus voltage is less than a preset voltage threshold, one of the two bus switch tubes is turned on / off at a preset first duty ratio, and the other of the two bus switch tubes is turned on / off at a preset second duty ratio.

[0019] When the bus voltage is greater than or equal to the preset voltage threshold, one of the two bus switch tubes is turned on / off at a preset third duty ratio, and the other of the two bus switch tubes is turned on / off at a preset fourth duty ratio.

[0020] In some embodiments, when the voltage of the input filter circuit reaches the three-phase alternating voltage connected to the power input end, when the bus voltage is greater than or equal to the preset voltage threshold, and the bus voltage is greater than a preset voltage range, both of the two bus switch tubes are in the off state.

[0021] When the bus voltage is greater than or equal to the preset voltage threshold, and the bus voltage is less than the preset voltage range, one of the two bus switch tubes is turned on / off at a preset fifth duty ratio, and the other of the two bus switch tubes is turned on / off at a preset sixth duty ratio.

[0022] The preset voltage threshold is less than or equal to the preset voltage range.

[0023] In some embodiments, two bus switch tubes are turned on / off at a preset duty ratio, which is calculated by the following formula:

[0024] V md = u dc + i s *R s ;

[0025] D = V md / (U max -U min );

[0026] 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 pass-through resistance; D is a preset duty ratio; U max is a maximum phase voltage of a three-phase input voltage; and U min is a minimum phase voltage of the three-phase input voltage.

[0027] In some embodiments, when the bus voltage is less than a preset voltage threshold, the target modulation voltage is increased from 0 to a target voltage at a first preset slope;

[0028] When the bus voltage is greater than or equal to the preset voltage threshold and less than a preset voltage range, the target modulation voltage is increased from a current voltage to the target voltage at a second preset slope, wherein the target voltage is within the preset voltage range.

[0029] In some embodiments, the power input end comprises a three-phase power input end, the input filter circuit comprises three input filter inductors and three input filter capacitors, first ends of the three input filter inductors are respectively connected to corresponding three-phase power input ends, and second ends of each input filter inductor are connected to an input filter capacitor.

[0030] The soft start circuit comprises at least two switch components, one of the two switch components is connected in series with one of the three input filter capacitors, and the other of the two switch components is connected in series with another of the three input filter capacitors.

[0031] In some embodiments, the soft start circuit comprises two switch components, i.e., a first switch component and a second switch component, a first end of the first switch component is connected to a three-phase power input end, a first end of the second switch component is connected to another three-phase power input end, and a second end of the first switch component is connected to a second end of the second switch component.

[0032] In some embodiments, the first switch assembly comprises a first current-limiting resistor and a first switch element connected in parallel; and the second switch assembly comprises a second current-limiting resistor and a second switch element connected in parallel.

[0033] In some embodiments, the first switch assembly comprises a first switch element; and the second switch assembly comprises a second current-limiting resistor and a second switch element connected in parallel.

[0034] In some embodiments, the first switch assembly comprises a first switch element; and the second switch assembly comprises a second current-limiting resistor and a second switch element connected in parallel.

[0035] The present application also provides a control method of a power supply circuit, which is based on any one of the above-mentioned power supply circuits, and comprises the following steps:

[0036] obtaining a voltage of an input filter circuit and a three-phase alternating voltage inputted into a power input terminal;

[0037] when the voltage of the input filter circuit is less than the three-phase alternating voltage inputted into the power input terminal, controlling a soft-start circuit to limit a current flowing into the input filter circuit within a preset current range.

[0038] In some embodiments, when the voltage of the input filter circuit reaches the three-phase alternating voltage inputted into the power input terminal, the control method of the power supply circuit further comprises:

[0039] obtaining a bus voltage, and controlling an operating state of the power supply circuit according to a size relationship between the bus voltage and a preset voltage range.

[0040] In some embodiments, the step of controlling the operating state of the power supply circuit according to the size relationship between the bus voltage and the preset voltage range specifically comprises:

[0041] when the bus voltage is less than a preset voltage threshold, controlling one of the two bus switch tubes to be turned on / off at a preset first duty ratio, and controlling the other of the two bus switch tubes to be turned on / off at a preset second duty ratio;

[0042] when the bus voltage is greater than or equal to the preset voltage threshold, controlling one of the two bus switch tubes to be turned on / off at a preset third duty ratio, and controlling the other of the two bus switch tubes to be turned on / off at a preset fourth duty ratio.

[0043] The present application also provides a control device, which comprises a memory, a processor, and a control program of a power supply circuit stored in the memory and executable on the processor, and the control program of the power supply circuit is configured to implement the steps of the control method of the power supply circuit.

[0044] The application also provides a refrigeration device comprising the power supply circuit according to any one of the above or comprising the control device according to the above.

[0045] In some embodiments, the refrigeration device comprises an air conditioner. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the application or the related art, the drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor based on the structures shown in the drawings.

[0047] Fig. 1 is a module schematic diagram of an embodiment of the power supply circuit of the application;

[0048] Fig. 2 is a related SWISS-PFC topology diagram;

[0049] Fig. 3 is a specific circuit diagram of an embodiment of the power supply circuit of the application;

[0050] Fig. 4 is a specific circuit diagram of another embodiment of the power supply circuit of the application;

[0051] Fig. 5 is a specific circuit diagram of still another embodiment of the power supply circuit of the application;

[0052] Fig. 6 is a state schematic diagram of three-phase alternating voltage, midpoint switch and bus switch tube under PWM control of the related SWISS-PFC topology;

[0053] Fig. 7 is a state schematic diagram of midpoint switch and bus switch tube under PWM control of an embodiment of the power supply circuit of the application;

[0054] Fig. 8 is a schematic diagram of parameter changes in the starting process of an embodiment of the power supply circuit of the application;

[0055] Fig. 9 is a schematic diagram of voltage changes in the starting process of another embodiment of the power supply circuit of the application;

[0056] Fig. 10 is a flowchart of an embodiment of the control method of the power supply circuit of the application;

[0057] Fig. 11 is a flowchart of still another embodiment of the control method of the power supply circuit of the application.

[0058] Explanation of reference numerals: 10, power supply input end; 20, input filter circuit; 30, midpoint switch; 40, PFC diode; 50, bus switch tube; 60, soft start circuit.

[0059] 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

[0060] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of the present application.

[0061] It should be noted that in this paper, step codes such as S100, S200 are used, the purpose is to express the corresponding content more clearly and simply, and it does not constitute a substantial limitation on the order. Those skilled in the art may perform S200 before performing S100 in specific implementation, but these shall be within the scope of protection of the present application.

[0062] 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. The SWISS-PFC usually includes a front-end LC filter circuit, a rectifier circuit, a PFC circuit and a rear-end DC-DC converter. The LC filter circuit is used to filter the alternating input voltage and output it to the rectifier circuit for rectification and output of a direct current voltage. The PFC circuit is used to realize power factor correction through soft switching technology, improve the input current waveform to 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. The traditional buck-type three-phase PFC topology adopts the form of a current inverter. When connected to the power grid, the inductance current and the capacitance voltage of the LC filter circuit will have a sharp oscillation phenomenon at the resonance frequency point, and the oscillation amplitude of the voltage may reach 2 times of the input voltage, reducing the reliability of the electric control. Therefore, it is usually necessary to use front-end devices with larger voltage and current resistance specifications, increasing the cost and volume.

[0063] To this end, the present application provides a power supply circuit, referring to FIG. 1, the power supply circuit comprises:

[0064] A power supply input end 10 for connecting three-phase alternating voltage;

[0065] An input filter circuit 20 electrically connected with the power supply input end 10 for filtering the three-phase alternating voltage and outputting it;

[0066] a midpoint switch 30, a first end of the midpoint switch 30 being electrically connected with the input filter circuit 20;

[0067] two PFC diodes 40, the two PFC diodes 40 being connected in series, a second end of the midpoint switch 30 being electrically connected with a common connection end of the two PFC diodes 40;

[0068] two bus switch tubes 50, each of the bus switch tubes 50 being electrically connected with the midpoint switch 30 and the PFC diode 40 respectively;

[0069] a slow start circuit 60, the slow start circuit 60 being electrically connected with the input filter circuit 20;

[0070] the slow start circuit 60 is capable of limiting the current flowing into the input filter circuit 20 when the voltage of the input filter circuit 20 is less than the three-phase alternating voltage connected to the power input end 10.

[0071] It should be noted that, with reference to FIG. 2, in the PFC topology of the related scheme, the bus switch tube 50 is usually used in cooperation with the midpoint switch 30 to ensure that the current flows in the expected manner. The control method of the related SWISS-PFC topology is: first, the size of the three-phase alternating voltage connected to the power input end 10 is sorted to select the midpoint switch 30 connected to the middle phase of the voltage to be turned on, that is, the voltage of the common connection end of the PFC diode 40 (D1 and D2) is anchored at the middle phase voltage; At this time, the two bus switch tubes 50 (Q1 and Q2) are alternately turned on in a cycle to form two loops: one loop is from the maximum voltage phase through the rear-end inductor Ls capacitor Cs back to the middle phase; The second is from the middle phase of the voltage through the inductor Ls capacitor Cs back to the minimum voltage phase. FIG. 6 is a state diagram of the three-phase alternating voltage, the midpoint switch 30 and the bus switch tube 50 under the PWM control of the related SWISS-PFC topology.

[0072] 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 30 (S1, S2, and S3) connected to each phase, two bus switch tubes 50 (Q1 and Q2), two PFC diodes 40 (D1 and D2), and a soft start circuit 60. The rectifier bridge is a three-phase bridge circuit, each bridge arm of the three-phase bridge arm includes two diodes connected in series, one midpoint switch 30 is connected in series on one side of the midpoint of each bridge arm, and 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 30 is connected to the common connection end of the two PFC diodes 40, the PFC diodes 40 are connected to an LC output circuit (including Ls and Cs), and the soft start circuit 60 is connected to the LC filter circuit in series and 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 the power factor regulation is realized.

[0073] In the embodiment, the midpoint switch 30 and the soft start circuit 60 can be realized by using a relay, a contactor, or the like, or by using an IGBT, a triode, or the like. The power circuit provided in the application further includes a first voltage detection circuit and a control circuit. The first 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 first 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 soft start circuit 60 and the controlled end of the midpoint switch 30. The first voltage detection circuit is used to detect the voltage of the input filter circuit 20 and output a corresponding first voltage detection signal to the control circuit, so that the control circuit controls the on / off state of the midpoint switch 30 and the soft start circuit 60 according to the received first voltage detection signal.

[0074] Specifically, the input filter circuit 20 is an LC filter circuit. When the power supply circuit is powered on, the midpoint switch 30 (S1, S2 and S3) is open. The first voltage detection circuit detects the voltage of the input filter circuit 20 and outputs a corresponding first voltage detection signal to the control circuit. When the control circuit determines that the voltage of the input filter circuit 20 is less than the three-phase alternating voltage connected to the power input end 10, the control circuit controls the soft start circuit 60 to limit the current flowing into the input filter circuit 20 within a preset current range. For example, the soft start circuit 60 includes a current-limiting resistor and a switching device connected in parallel. When the voltage of the input filter circuit 20 is less than the three-phase alternating voltage connected to the power input end 10, the control circuit controls the switching device to be open, and the capacitor C is not charged, and the voltage across the capacitor C is zero. The three-phase alternating voltage is applied to the capacitor C and the current-limiting resistor. Since the impedance of the capacitor C varies with frequency, most of the voltage drop occurs on the current-limiting resistor. The current-limiting resistor limits the charging current of the capacitor C, so that the current will not be too large. As the charging time of the capacitor C increases, the voltage across it gradually increases, and the total current in the circuit gradually decreases, and the current flowing into the input filter circuit 20 gradually decreases. When the capacitor C is fully charged, the voltage across it is equal to the three-phase alternating voltage, at which time the voltage drop on the current-limiting resistor is zero, and the current is zero, i.e. the current flowing into the input filter circuit 20 decreases to 0.

[0075] The setting of the current-limiting resistor limits the current flowing into the LC filter circuit, thereby limiting the charging speed of the capacitor C. When the capacitor C starts to charge, its voltage gradually rises until it approaches the three-phase input voltage of the power input end 10. In this process, the current flows into the capacitor C through the current-limiting resistor, ensuring a smooth charging process. In order to stop the work of the soft start circuit 60 when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power input end 10, the control circuit controls the switching device to be closed, and the current-limiting resistor is short-circuited, cutting the soft start circuit 60 out of the power supply circuit, and the capacitor C is directly connected to the power grid, so that the LC filter circuit is smoothly connected to the power grid. After the switching device is closed, the voltage of the capacitor C is close to the voltage of the power grid connected to the power input end 10, and the current changes very little, ensuring that the LC filter circuit is smoothly connected to the power grid and reducing the risk of oscillation of the inductor L and the capacitor C in the LC filter circuit caused by sudden changes in current and voltage when the power supply circuit is powered on.

[0076] In practical application, when the power supply circuit is powered on, i.e. when the three-phase alternating voltage is connected to the power input end 10, the soft start circuit 60 is connected to the power supply circuit to limit the current flowing into the input filter circuit 20, so as to limit the current of the input filter circuit 20 within a preset current range, so as to smoothly connect the input filter circuit 20 to the power grid, thereby improving the oscillation problem of the input filter circuit 20 when the power supply circuit is powered on. In this way, the reliability and stability of the power supply circuit are improved, and at the same time, the hardware configuration of the soft start circuit 60 can be realized by using a current limiting resistor and a switching device, thereby reducing the circuit design cost and size.

[0077] In an embodiment of the present application, the soft start circuit 60 includes a current limiting mode and a start mode.

[0078] When the voltage of the input filter circuit 20 is less than the three-phase alternating voltage connected to the power input end 10, the soft start circuit 60 is in the current limiting mode, in which the soft start circuit 60 is connected to the power supply circuit, the voltage across the input filter circuit 20 gradually increases, and the current flowing into the input filter circuit 20 gradually decreases.

[0079] When the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power input end 10, the soft start circuit 60 is in the start mode, in which the soft start circuit 60 is disconnected from the power supply circuit, and the charging time of the input filter circuit 20 is reduced to speed up the start speed of the power supply circuit.

[0080] In combination with the above embodiments, the first voltage detection circuit detects the voltage of the input filter circuit 20 and outputs a corresponding first voltage detection signal to the control circuit. When the control circuit determines, according to the first voltage detection signal, that the voltage of the input filter circuit 20 is less than the three-phase alternating voltage connected to the power input end 10, the control circuit controls the soft start circuit 60 to be in the current limiting mode. In actual application, when the alternating input end is connected to the three-phase alternating voltage, the soft start circuit 60 is connected to the power supply circuit, and the current flowing into the input filter circuit 20 is limited within a preset current range through the current limiting resistor. At this time, the capacitor C in the LC filter circuit starts to charge, and the voltage gradually rises until it approaches the three-phase input voltage of the power input end 10. That is, the voltage across the capacitor C gradually increases, the total current in the circuit gradually decreases, and the current flowing into the input filter circuit 20 gradually decreases. When the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power input end 10, that is, the voltage of the capacitor C is close to the grid voltage connected to the power input end 10, the control circuit controls the soft start circuit 60 to be in the start mode, and the LC filter circuit is smoothly connected to the grid. At this time, the soft start circuit 60 is cut off from the power supply circuit, and the current limiting resistor is short-circuited, so that the charging time is reduced and the start speed of the power supply circuit is accelerated. In this way, the risk of oscillation of the inductor L and the capacitor C in the LC filter circuit caused by sudden changes of current and voltage during the start-up of the power supply circuit is reduced, and it is ensured that the capacitor C will not be damaged due to excessive current during power-up.

[0081] It should be noted that the power supply circuit start-up process can be divided into two steps: LC filter circuit power-up and bus power-up, and LC oscillation occurs in these two processes. In this embodiment, after the soft start circuit 60 is in the start mode and runs for a preset time, the midpoint switch 30 is closed. For example, the control circuit can gradually raise the bus voltage by controlling the on / off time of the bus switch tube 50, that is, by changing the duty cycle of the output PWM control signal, and then transition to load start. When the bus voltage is stable within a preset voltage range, the midpoint switch 30 is controlled to be closed, the load start is completed, and the normal modulation mode is switched to. The normal modulation mode refers to the control logic of the PFC topology in the related scheme, which will not be described here. The preset voltage range is set in advance by the researchers. The preset time is the time required for the bus voltage to increase from 0V to the preset voltage range and for the load to reach the preset parameter value. The preset parameter value is usually set by the equipment manufacturer according to the specifications and performance indicators of the equipment, which can reflect the best operating state of the load equipment and is also a prerequisite for normal operation of the load. That is, when it is determined that the load start is completed and can enter the normal working state, the control circuit controls the midpoint switch 30 to be closed and switches to the normal modulation mode.

[0082] In the current-limiting mode, the current flowing into the input filter circuit 20 is limited by the soft-start circuit 60 to ensure the capacitor C is charged smoothly, so that the current is not too large, reducing the risk of oscillation when the LC filter circuit is powered on. When the voltage of the capacitor C approaches the three-phase alternating voltage of the power input terminal 10, the control circuit controls the soft-start circuit 60 to enter the starting mode, i.e. to cut it out of the power supply circuit, to reduce the charging time of the input filter circuit 20, thereby speeding up the overall starting speed of the power supply circuit. And by adjusting the duty cycle of the PWM control signal output by itself, the on / off duration of the bus switch tube 50 is controlled, gradually raising the bus voltage, and the gradual rise of the bus voltage reduces the current mutation when the bus capacitor is charged, thereby reducing the risk of LC oscillation, effectively reducing the oscillation phenomenon caused by the existence of the bus capacitor when the bus is powered on. In this way, the control circuit controls the soft-start circuit 60 to work in the current-limiting mode and the starting mode, ensuring that the power supply circuit is smoothly connected to the power grid, and improving the stability and reliability of the power supply circuit.

[0083] In some embodiments of the present application, the power input terminal 10 includes a three-phase power input terminal 10, and the input filter circuit 20 includes three input filter inductors and three input filter capacitors. The first ends of the three input filter inductors are respectively connected to the corresponding three-phase power input terminal 10, and the second end of each input filter inductor is connected to an input filter capacitor.

[0084] The soft-start circuit 60 includes at least two switching components. One of the two switching components is connected in series with one of the three input filter capacitors, and the other of the two switching components is connected in series with another of the three input filter capacitors.

[0085] Referring to FIG. 3, the input filter circuit 20 is an LC filter circuit, which includes three input filter inductors L1, L2 and L3 and three input filter capacitors C1, C2 and C3. The first ends of the three input filter inductors are respectively connected to the corresponding three-phase power input terminal 10 (A, B, C), and the second end of each input filter inductor is connected to an input filter capacitor.

[0086] In this embodiment, the soft-start circuit 60 includes two switching components, namely a first switching component and a second switching component. The first end of the first switching component is connected to one of the three-phase power input terminal 10, and the first end of the second switching component is connected to another of the three-phase power input terminal 10. The second end of the first switching component and the second end of the second switching component are electrically connected.

[0087] In some embodiments, the first switch assembly comprises a first current-limiting resistor and a first switch element connected in parallel; and the second switch assembly comprises a second current-limiting resistor and a second switch element connected in parallel.

[0088] Alternatively, the first switch assembly comprises a first switch element; and the second switch assembly comprises a second current-limiting resistor and a second switch element connected in parallel.

[0089] As shown in FIG. 3, the buffer circuit comprises two switch assemblies, the first switch assembly comprises a first current-limiting resistor R1 and a first switch element K1 connected in parallel, and the second switch assembly comprises a second current-limiting resistor R2 and a second switch element K2 connected in parallel. That is, the two current-limiting resistors are connected in parallel with the first switch element and the second switch element respectively, and then connected in series with C. As shown in FIG. 4, the first switch assembly comprises a first current-limiting resistor R1 and a first switch element K1 connected in parallel, and the second switch assembly comprises a second switch element K2. That is, C1 is connected in series with the second switch element K2 directly, and the first current-limiting resistor R1 and the first switch element K1 are connected in parallel and then connected in series with the capacitor C3.

[0090] It should be noted that the first switch element and the second switch element can be realized by using a relay, a contactor or other switch devices, or realized by using a transistor, an IGBT or other switch tubes.

[0091] Specifically, as shown in FIG. 3, taking the first switch element and the second switch element as an example, when the power supply circuit is powered on, the capacitors C1 and C3 are charged through the current-limiting resistors R2 and R1 respectively, so as to limit the current flowing into the input filter circuit 20 within a preset current range. That is, if a resistor with a larger resistance value is selected as the current-limiting resistor, the charging current can be ensured to be small and smooth, and large current mutation will not be caused. When the voltages of the capacitors C1 and C3 reach a certain threshold value, for example, when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage input into the power supply input end 10, the voltage across the capacitors is close to the incoming voltage of the power supply input end 10. At this time, the voltages across the relays K1 and K2 are small, and the control circuit controls the relays K1 and K2 to be closed.

[0092] It can be understood that theoretically, the input phase current after stabilization can be calculated according to the capacitance value and the phase of the input voltage, or the input current of the input filter circuit 20 can be directly detected, and then the closing sequence of the relays K1 and K2 is determined. In the embodiment, the power supply circuit can further include a current detection circuit for detecting the input phase current or the input current of the input filter circuit 20 and outputting a current detection signal to the control circuit, so that the control circuit controls the on / off state of the relays according to the current detection signal. When the current value of the input phase current or the input current is less than a preset current threshold, the corresponding relay is controlled to be closed. The preset current threshold is set by the developer in advance. In actual application, if the C capacitance value is small, the relays K1 and K2 can be controlled to be closed at the same time. In this way, the starting time can be shortened, and the response speed of the power supply circuit can be improved.

[0093] As shown in FIG. 4, the soft start circuit 60 includes two current-limiting resistors R1 and R2 and a relay K1, wherein the current-limiting resistor R1 is connected in parallel with the relay K2 and then connected in series with the capacitor C3, and the relay K2 is directly connected in series with the capacitor C1. Since there is only one buffer resistor, the control circuit needs the timing of the relay closure. In the embodiment, when the control circuit determines that the voltage of the input filter circuit 20 reaches the three-phase alternating voltage input into the power supply input end 10 according to the first voltage detection signal, the control circuit first closes the relay K1, so as to first connect the two LC branches (the branch in which L2 and C2 are located and the branch in which L3 and C3 are located) to the power grid, and then closes the other relay K2 at a suitable time point. For example, when the absolute value of the phase voltage corresponding to the relay K2 drops to a preset threshold U1, the control circuit controls the K2 to be closed, wherein the preset threshold U1 is set by the developer in advance and is close to 0V. In order to reduce the arc and transient voltage / current impact generated in the switching process, in this way, the switching loss is reduced, and the electromagnetic interference is reduced.

[0094] In some embodiments, the soft start circuit 60 can further include three switching components, each of which has a current-limiting resistor and a relay connected in parallel, and then connected in series with a corresponding capacitor C, as shown in FIG. 5. When the power supply circuit is powered on, the capacitors C1, C2 and C3 are charged through the current-limiting resistors R1, R2 and R3 respectively, so as to limit the current flowing into the input filter circuit 20 within a preset current range. That is, if a resistor with a larger resistance value is selected as the current-limiting resistor, the charging current can be ensured to be small and smooth, and large current mutations will not be caused. When the voltages of the capacitors C1, C2 and C3 reach a certain threshold, that is, when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage input into the power supply input end 10, at this time, the voltage across the capacitors is close to the incoming line voltage of the power supply input end 10, and the voltage across the relays K1, K2 and K3 is small. The control circuit controls the relays K1, K2 and K3 to be closed. The control circuit can determine the closing sequence of the relays according to the input phase current or the input current of the input filter circuit 20.​

[0095] Through the above setting, when the power supply circuit is powered on, the charging current of the input filter circuit 20 can be first limited by the current limiting resistor to ensure smooth current rise and reduce the risk of LC oscillation when the LC filter circuit is powered on; the input phase current calculated according to the capacitance value and the input voltage phase or the input current of the input filter circuit 20 directly detected by the current detection circuit realizes dynamic adjustment of the closing sequence of the relay, and improves the reliability and stability of the power supply circuit.

[0096] It can be understood that when the power supply circuit is powered on, the bus capacitor starts charging, and under a large current, the charging current changes greatly, which is easy to cause oscillation. Oscillation will cause the bus voltage to be unstable, affect the normal work of the power supply, and even damage the components in the circuit.

[0097] Therefore, in the embodiment, when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power supply input end 10, and the bus voltage is less than the preset voltage threshold, one of the two bus switch tubes 50 is turned on / off with a preset first duty ratio; the other one of the two bus switch tubes 50 is turned on / off with a preset second duty ratio.

[0098] When the bus voltage is greater than or equal to the preset voltage threshold, one of the two bus switch tubes 50 is turned on / off with a preset third duty ratio; the other one of the two bus switch tubes 50 is turned on / off with a preset fourth duty ratio.

[0099] In combination with the above embodiment, when the power supply circuit is powered on, the control circuit controls the midpoint switch 30 to be turned off, and controls the relay to be turned off, and the current limiting resistor of the soft start circuit 60 limits the current of the input filter circuit 20 within a preset current range. When the control circuit determines that the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power supply input end 10 according to the first voltage detection signal, the relay is closed, and after the relay is closed, the control circuit outputs the corresponding PWM control signal to control the bus switch tube 50Q1 and Q2 to be turned on / off, so as to realize power factor correction, improve the input current waveform, and make it close to a sine wave, thereby improving the power factor. As shown in FIG. 7, FIG. 7 is a state diagram of the midpoint switch 30 and the bus switch tube 50 under PWM control of the power supply circuit in the embodiment, i.e., the output mode when each switch tube is started.

[0100] It should be noted that the two bus switch tubes 50 can use the same PWM control signal or different PWM control signals, but only the overlapping part is effective. That is, Q1 and Q2 can be controlled by the same pulse width modulation (PWM) signal, which means that their opening and closing times are synchronized and the duty cycles are equal. At this time, the preset first duty cycle and the preset second duty cycle are equal. Alternatively, Q1 and Q2 can also use different PWM control signals, and at this time, the preset first duty cycle and the preset second duty cycle are not equal. However, only when the overlapping part of the two PWM control signals coincides, current can flow through the power supply circuit. When Q1 and Q2 are in the on state at the same time, current can flow from the power supply to the load. If the PWM control signals of Q1 and Q2 are not exactly the same, current can only flow through the circuit when the opening and closing times of the two PWM control signals coincide. It can be understood that "overlap" here refers to the part where the opening and closing times of the two PWM control signals coincide, that is, the period when the two switches are turned on at the same time. During this period, current can flow through the circuit to complete energy transmission. If the two PWM control signals do not overlap, the current will be interrupted and the load cannot be continuously powered.

[0101] In the embodiment, when the control circuit controls the relay of the slow start circuit 60 to close, that is, shorts the current limiting resistor, the control circuit stops working, and the control circuit controls the bus switch tubes 50 Q1 and Q2 to be turned on / off with a preset first duty cycle and a preset second duty cycle, respectively, to smoothly establish the bus voltage, so that the bus voltage gradually rises, reducing the influence of the bus capacitor on the bus voltage during power-on. When the bus voltage is greater than or equal to a preset voltage threshold, one of the two bus switch tubes 50 is turned on / off with a preset third duty cycle; the other bus switch tube 50 is turned on / off with a preset fourth duty cycle. That is, when the bus voltage rises to the preset voltage threshold, the duty cycles of Q1 and Q2 are changed to control the size of the bus voltage, so as to ensure that the bus voltage is within a stable range, preventing large current from being generated during the charging process of the bus capacitor during power-on, which can cause oscillation. In this way, the stability and safety of the power supply circuit and the power supply system in which the power supply circuit is located are ensured.

[0102] In some embodiments, when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power supply input end 10, when the bus voltage is greater than or equal to a preset voltage threshold, and the bus voltage is greater than a preset voltage range, both bus switch tubes 50 are in the off state.

[0103] When the bus voltage is greater than or equal to the preset voltage threshold value and the bus voltage is less than the preset voltage range, one of the two bus switch tubes 50 is turned on / off at a preset fifth duty ratio; the other of the two bus switch tubes 50 is turned on / off at a preset sixth duty ratio.

[0104] The preset voltage threshold value is less than or equal to the preset voltage range.

[0105] Specifically, the upper limit value of the preset voltage range is U4, and the lower limit value is U3. In combination with the above embodiment content, the control circuit controls the bus switch tubes 50Q1 and Q2 to be turned on / off at a preset first duty ratio and a preset second duty ratio, respectively, through the output of the PWM control signal, so as to smoothly establish the bus voltage, and gradually increase the bus voltage. In this embodiment, the power supply circuit further includes a second voltage detection circuit for detecting the bus voltage and outputting a corresponding second voltage detection signal to the control circuit, so that the control circuit determines the size of the bus voltage according to the second voltage detection signal, and further determines the duty ratio of the bus switch tube 50.

[0106] The two bus switch tubes 50 are turned on / off at a preset duty ratio, and the preset duty ratio is calculated by the following formula:

[0107] V md = u dc +i s *R s ;

[0108] D = V md / (U max -U min );

[0109] Wherein, 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; D is the preset 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.

[0110] In this embodiment, when the bus voltage is less than the preset voltage threshold value, the target modulation voltage V mdThe first preset slope is increased from 0 to a target voltage U2. At this time, the preset first duty cycle of the bus switch tube 50 and the preset second duty cycle of the bus switch tube 50 change with the change of the target adjustment voltage, so as to realize the establishment and smooth rising process of the bus voltage. The target voltage is set by the R&D personnel in advance, which can guarantee the minimum voltage value meeting the demand of load starting, that is, the bus voltage needs to be higher than the minimum demand voltage of load starting, and the highest allowable voltage is higher than the target voltage by a safety margin of 50V-100V. With the increase of the bus voltage, when the bus voltage is greater than or equal to a preset voltage threshold and less than a preset voltage range, the target modulation voltage is increased from the current voltage to the target voltage with a second preset slope, wherein the target voltage is within the preset voltage range. That is, when the target modulation voltage V md The first preset slope is increased from 0 to a target voltage U2. With the change of the duty cycle, the bus voltage reaches a preset voltage threshold, at which time a preset voltage range can be set by the R&D personnel in advance. The control circuit can determine the size of the bus voltage according to the second voltage detection signal output by the second voltage detection circuit, compare the bus voltage with the preset voltage range, and then adjust the duty cycles of the bus switch tubes 50Q1 and Q2.

[0111] In some embodiments, when the bus voltage is greater than or equal to a preset voltage threshold and the bus voltage is greater than a preset voltage range, both bus switch tubes 50 are in an off state when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power input end 10.

[0112] When the bus voltage is greater than or equal to a preset voltage threshold and the bus voltage is less than a preset voltage range, one of the two bus switch tubes 50 is turned on / off with a preset fifth duty cycle, and the other bus switch tube 50 is turned on / off with a preset sixth duty cycle.

[0113] The preset voltage threshold is less than or equal to the preset voltage range.

[0114] Specifically, assuming that the upper limit value of the preset voltage range is U4 and the lower limit value is U3. The target voltage U2 is greater than U3 and less than U4. When the control circuit determines the size of the bus voltage according to the second voltage detection signal output by the second voltage detection circuit and compares the bus voltage with the preset voltage range, it is determined that the bus voltage is greater than the preset voltage range when the bus voltage reaches (is greater than or equal to) the preset voltage threshold. That is, when the bus voltage exceeds the upper limit value U4, the preset third duty cycle and the preset fourth duty cycle take the value of 0, and the duty cycles of Q1 and Q2 are both 0. When the bus voltage is less than the preset voltage range, the control target modulation voltage V mdWhen the bus voltage reaches the target voltage, one of the bus switch tubes 50 is turned on / off with a preset fifth duty ratio, and the other bus switch tube 50 is turned on / off with a preset sixth duty ratio. The preset fifth duty ratio and the preset sixth duty ratio change with the change of the target modulation voltage. In this way, by adjusting the duty ratios of Q1 and Q2, the bus voltage is raised to the preset voltage range. The control circuit can also control the bus switch tubes 50 Q1 and Q2 to turn on / off with a fixed duty ratio, so that the bus voltage is stabilized in the preset voltage range. Referring to FIGS. 8 and 9, FIG. 8 is a schematic diagram of the changes of various parameters in the starting process of an embodiment of the power supply circuit, from top to bottom, respectively, are the schematic diagram of the on / off state change of the relay KM, the schematic diagram of the change of the target modulation voltage, the schematic diagram of the change of the duty ratio of the bus switch tube 50, and the schematic diagram of the change of the PWM control signal. FIG. 9 is a schematic diagram of the changes of various voltages in the starting process of another embodiment of the power supply circuit; from top to bottom, respectively, are the schematic diagram of the change of the three-phase alternating voltage connected to the power supply input end 10, the schematic diagram of the change of the capacitor voltage, the schematic diagram of the change of the input current, and the schematic diagram of the change of the bus voltage.

[0115] It should be noted that when the control circuit determines that the bus voltage reaches the preset voltage range, i.e., the bus voltage is greater than or equal to U3 and less than or equal to U4, the corresponding start signal is output to start the compressor, the fan and other loads. When the speed of the compressor and the fan reaches the preset parameter value, the starting is completed, at this time, the control circuit controls the midpoint switch 30 S1 / S2 / S3 to be closed, and the power supply circuit switches to the normal modulation mode. Starting the compressor, the fan and other loads after the bus voltage is stabilized can avoid damage to the equipment caused by voltage transients or overshoot. For example, if the bus voltage is too high, the load equipment may be burned out; if the bus voltage is too low, the equipment may not work normally. The setting of the preset voltage range can ensure that when the bus voltage is in the preset voltage range, the load is started, and the load can quickly reach the expected working state, improving the efficiency of the load working.

[0116] In practical applications, when the power supply circuit is powered on, the power supply circuit of the application can limit the current flowing into the input filter circuit 20 within a preset current range through the current limiting resistor in the slow start circuit 60, so as to smoothly connect the input filter circuit 20 (LC filter circuit) to the power grid, thereby improving the oscillation problem of the input filter circuit 20 when the power supply circuit is powered on and started. In addition, after the control circuit stops the slow start circuit 60 from working, that is, the relay of the slow start circuit 60 is closed, the duty cycle of the bus switch tubes 50Q1 and Q2 can be adjusted to establish the bus voltage and make it gradually rise until it reaches the preset voltage range, thereby suppressing the oscillation of the bus capacitor when it is powered on, which causes the problem of unstable bus voltage. In this way, the power supply circuit of the application improves the problems of LC filter circuit power-on oscillation and bus capacitor power-on oscillation, improves the reliability and stability of the power supply circuit, and further improves the reliability and stability of the rear-end load. In addition, the slow start circuit 60 can be realized by simple components such as current limiting resistors and relays, without the need to use front-end devices with larger voltage and current ratings, thereby reducing cost and size.

[0117] The application also provides a control method of a power supply circuit, which is based on any one of the power supply circuits described above. The control method of the power supply circuit comprises the following steps:

[0118] In step S100, the voltage of the input filter circuit 20 and the three-phase alternating voltage connected to the power input end 10 are obtained.

[0119] In step S200, when the voltage of the input filter circuit 20 is less than the three-phase alternating voltage connected to the power input end 10, the slow start circuit 60 is controlled to limit the current flowing into the input filter circuit 20 within a preset current range.

[0120] In this embodiment, the control method of the power supply circuit of the application can be applied to a control device of a refrigeration equipment, for example, a control device integrated with a memory for storing the control program of the power supply circuit of the application and a processor for executing the control program of the power supply circuit of the application. The control device can be realized by 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), etc. The refrigeration equipment includes a refrigerator, an air conditioner, a freezer, etc. The control device is integrated with a first voltage detection circuit, a second voltage detection circuit, a current detection circuit, a control circuit, etc.

[0121] In combination with the above embodiment, the first voltage detection circuit in the power supply circuit is configured to detect the voltage of the input filter circuit 20 and output a first voltage detection signal to the control circuit, so that the control circuit determines, according to the first voltage detection signal, that the voltage of the input filter circuit 20 is less than the three-phase alternating voltage connected to the power input end 10, and controls the soft start circuit 60 to be in the current limiting mode, i.e., controls the soft start circuit 60 to limit the current flowing into the input filter circuit 20 within a preset current range, so as to improve the problem of oscillation of the capacitor C in the input filter circuit 20 during the power-on start of the power supply circuit.

[0122] For example, the soft start circuit 60 includes a first relay K1, a second relay K2, a first current limiting resistor R1 and a second current limiting resistor R2. Referring to FIG. 3, the first relay K1 is connected in parallel with the first current limiting resistor R1 and then connected in series with the capacitor C3 in the input filter circuit 20; the second relay K2 is connected in parallel with the second current limiting resistor R2 and then connected in series with the capacitor C1 in the input filter circuit 20, and the capacitor C2 in the input filter circuit 20 is electrically connected to the second common connection end of the first relay K1 and the first current limiting resistor R1.

[0123] Specifically, when the power supply circuit is powered on, the relays K1 and K2 and the midpoint switches 30S1, 30S2 and 30S3 are all in the open state, and the capacitors C1 and C3 are charged through the current limiting resistors R2 and R1 respectively, so as to limit the current flowing into the input filter circuit 20 within a preset current range. If a resistor with a large resistance value is selected as the current limiting resistor, the charging current can be small and smooth, and large current mutation can be avoided, thereby improving the problem of oscillation of the LC filter circuit during power-on. When the voltages of the capacitors C1 and C3 reach a certain threshold, the control soft start circuit 60 is in the start mode. For example, when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power input end 10, the voltage across the capacitors is close to the line voltage of the power input end 10, at this time, the voltages across the relays K1 and K2 are small, and the control circuit controls the relays K1 and K2 to be closed to short the current limiting resistors.

[0124] It can be understood that theoretically, the stabilized input phase current can be calculated according to the capacitance value of the LC filter capacitor and the phase of the input voltage, or the input current of the input filter circuit 20 is directly detected, and then the closing sequence of the relays K1 and K2 is determined. In the embodiment, the current detection circuit of the power supply circuit is used to detect the input phase current or the input current of the input filter circuit 20, and output a current detection signal to the control circuit, so that the control circuit controls the on / off state of the relays K1 and K2 according to the current detection signal. When the current value of the input phase current or the input current is less than a preset current threshold, the corresponding relay is controlled to be closed. The preset current threshold is set in advance by the developer. In actual application, if the C capacitance value is small, the relays K1 and K2 can be controlled to be closed at the same time. In this way, the starting time can be shortened, and the response speed of the power supply circuit can be improved.

[0125] By the above method, the current of the LC filter circuit is limited in the preset current range when the power supply circuit is powered on, so as to smoothly connect the input filter circuit 20 to the power grid, thereby improving the oscillation problem of the input filter circuit 20 when the power supply circuit is powered on. In this way, the reliability and stability of the power supply circuit are improved, without using high-voltage components, reducing the circuit design cost and size.

[0126] In an embodiment of the present application, when the voltage of the input filter circuit 20 reaches the three-phase alternating voltage connected to the power supply input end 10, the control method of the power supply circuit further comprises:

[0127] Obtaining the bus voltage and controlling the working state of the power supply circuit according to the size relationship between the bus voltage and the preset voltage range.

[0128] In combination with the above embodiment, the second voltage detection circuit of the power supply circuit obtains the bus voltage and outputs a second voltage detection signal to the control circuit, so that the control circuit controls the working state of the power supply circuit according to the bus voltage and the preset voltage range. The working state of the power supply circuit includes the on / off state of the bus switch tubes 50Q1 and Q2 and the midpoint switches 30S1, S2 and S3.

[0129] In some embodiments, referring to FIG. 11, the step of controlling the working state of the power supply circuit according to the size relationship between the bus voltage and the preset voltage range specifically comprises:

[0130] Step S300, when the bus voltage is less than a preset voltage threshold, one of the two bus switch tubes 50 is controlled to be turned on / off at a preset first duty ratio, and the other of the two bus switch tubes 50 is controlled to be turned on / off at a preset second duty ratio;

[0131] Step S400, when the bus voltage is greater than or equal to the preset voltage threshold, one of the two bus switch tubes 50 is controlled to be turned on / off with a preset third duty ratio, and the other of the two bus switch tubes 50 is controlled to be turned on / off with a preset fourth duty ratio.

[0132] In the embodiment, when the control device closes the relays K1 and K2 and shorts the current-limiting resistors R1 and R2, the bus switch tubes 50Q1 and Q2 are controlled to work. Specifically, when the bus voltage is less than the preset voltage threshold, the target modulation voltage V md increases from 0V to a target voltage U2 at a first preset slope; at this time, the preset first duty ratio of the bus switch tube 50 and the preset second duty ratio of the bus switch tube 50 change with the change of the target adjustment voltage, so as to realize the establishment and smooth rising process of the bus voltage. The target voltage is set by the researchers in advance, which can guarantee the minimum voltage value meeting the demand of load starting, i.e., the bus voltage needs to be higher than the minimum demand voltage of load starting; and the highest allowable voltage is higher than the target voltage by a safety margin of 50V-100V. With the increase of the bus voltage, when the bus voltage is greater than or equal to the preset voltage threshold, one of the two bus switch tubes 50 is controlled to be turned on / off with a preset third duty ratio, and the other of the two bus switch tubes 50 is controlled to be turned on / off with a preset fourth duty ratio. That is, when the bus voltage rises to the preset voltage threshold, the duty ratios of Q1 and Q2 are changed to control the size of the bus voltage, so as to ensure that the bus voltage is in a stable range, prevent the bus capacitor from generating a large current in the charging process of the power-on starting, and prevent oscillation from affecting the stable work of the bus voltage and the load. In this way, the stability and safety of the power supply circuit and the power supply system where the power supply circuit is located are ensured.

[0133] After the bus voltage reaches the preset voltage threshold, the control device can determine the duty ratios of the two bus switch tubes 50 according to the size relationship between the bus voltage and the preset voltage range. For example, it is assumed that the upper limit value of the preset voltage range is U4 and the lower limit value is U3. When the bus voltage is greater than the preset voltage range, the control device controls the two bus switch tubes 50 to be in the off state. When the bus voltage is less than the preset voltage range, the target modulation voltage increases from the current voltage (at the same time as the detected bus voltage) to a target voltage at a second preset slope, wherein the target voltage is within the preset voltage range. That is, when the target modulation voltage V mdThe bus voltage reaches the preset voltage threshold with the change of the duty cycle as the first preset slope increases from 0 to the target voltage U2, and the establishment and gradual rising process of the bus voltage is completed. At this time, a preset voltage range can be set in advance by the R&D personnel, and the control device can determine the size of the bus voltage and compare it with the preset voltage range, and then adjust the duty cycle of the bus switch tube 50Q1 and Q2 to make the bus voltage stable in the preset voltage range. After the slow start circuit 60 is in the starting mode for a preset time period, the midpoint switch 30 is closed. That is, when the bus voltage is in the preset voltage range, the compressor, fan and other loads are started, and when the speed of the compressor and fan reaches the preset parameter value, the starting is completed, at this time, the control circuit controls the midpoint switch 30S1 / S2 / S3 to be closed, and the power supply circuit is switched to the normal modulation mode.

[0134] It can be understood that the preset parameter value is usually set by the equipment manufacturer according to the specifications and performance indicators of the equipment, which can reflect the best running state of the equipment and is also a prerequisite for the normal operation of the equipment. For example, for the compressor, the preset parameter value may be its rated speed, which is the speed required for the device to operate normally under full load. For the fan, the preset parameter value may be the speed under the designed air volume. Only when the speeds of the compressor and the fan both reach their respective preset parameter values, can it be considered that the starting process is completed.

[0135] In actual application, after the power supply circuit is powered on, the power supply circuit of the present application can limit the current flowing into the input filter circuit 20 within a preset current range through the current limiting resistor in the slow start circuit 60, so that the C in the LC filter circuit charges, and then the input filter circuit 20 (LC filter circuit) is smoothly connected to the power grid, improving the oscillation problem generated when the input filter circuit 20 starts to power on the power supply circuit. In addition, after the control circuit controls the slow start circuit 60 to stop working, i.e. closes the relay of the slow start circuit 60, short-circuits the current limiting resistor, and further adjusts the duty cycle of the bus switch tube 50Q1 and Q2 to establish the bus voltage and make it gradually rise until it reaches the preset voltage range, thereby suppressing the oscillation of the bus capacitor when it is powered on, and the problem of unstable bus voltage. In this way, the power supply circuit of the present application improves the problems of LC filter circuit power-on oscillation and bus capacitor power-on oscillation, improves the reliability and stability of the power supply circuit, and further improves the reliability and stability of the rear-end load. In addition, the slow start circuit 60 can be realized by simple components such as current limiting resistor and relay, without the need to use front-end devices with larger voltage and current ratings, thereby reducing the cost and size.

[0136] It is worth noting that the control method of the power supply circuit of the present application is based on the power supply circuit described above, 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 power supply circuit described above, 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 on 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 control methods of the power supply circuit described above.

[0138] It is worth noting that since the control device of the present application is based on the control method of the power supply circuit described above, 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 power supply circuit described above, 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 and / or the control device according to any one of the above.

[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 through the power supply circuit proposed in the present application to adjust the current waveform to be close to a sine wave, thereby improving power supply efficiency, reducing energy waste, and improving power grid quality. 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 power supply circuit and the control device described above can improve the problems of LC filter circuit power oscillation and bus capacitor power oscillation, so that smaller voltage withstand value switching devices can be selected, and the cost and volume can be reduced.

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

[0142] The above is only an optional embodiment 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 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; an input filter circuit electrically connected to the power input end for filtering the three-phase alternating voltage and outputting the filtered voltage; a midpoint switch having a first end electrically connected to the input filter circuit; two PFC diodes connected in series, and 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 which is electrically connected to the midpoint switch and the PFC diodes; a soft start circuit electrically connected to the input filter circuit; the soft start circuit is capable of limiting the current flowing into the input filter circuit when the voltage of the input filter circuit is less than the three-phase alternating voltage connected to the power input end.

2. The power supply circuit of claim 1, wherein, The soft start circuit comprises a current-limiting mode and a start mode; when the voltage of the input filter circuit is less than the three-phase alternating voltage connected to the power input end, the soft start circuit is in the current-limiting mode, in which the soft start circuit is connected to the power supply circuit, the voltage across the input filter circuit gradually increases, and the current flowing into the input filter circuit gradually decreases; when the voltage of the input filter circuit reaches the three-phase alternating voltage connected to the power input end, the soft start circuit is in the start mode, in which the soft start circuit is disconnected from the power supply circuit, and the charging time of the input filter circuit is reduced to accelerate the start speed of the power supply circuit.

3. The power supply circuit of claim 1 or 2, wherein, When the soft start circuit is in the start mode and runs for a preset time, the midpoint switch is closed.

4. The power supply circuit of any one of claims 1 to 3, wherein, When the voltage of the input filter circuit reaches the three-phase alternating voltage connected to the power input end, and the bus voltage is less than a preset voltage threshold, one of the two bus switch tubes is turned on / off at a preset first duty ratio, and the other bus switch tube is turned on / off at a preset second duty ratio. When the bus voltage is greater than or equal to the preset voltage threshold, one of the two bus switch tubes is turned on / off at a preset third duty ratio, and the other bus switch tube is turned on / off at a preset fourth duty ratio.

5. The power supply circuit of claim 1 or 2, wherein, When the voltage of the input filter circuit reaches the three-phase alternating voltage connected to the power input end, and the bus voltage is greater than or equal to the preset voltage threshold and greater than a preset voltage range, both of the two bus switch tubes are in an off state. When the bus voltage is greater than or equal to the preset voltage threshold and less than the preset voltage range, one of the two bus switch tubes is turned on / off at a preset fifth duty ratio, and the other bus switch tube is turned on / off at a preset sixth duty ratio. The preset voltage threshold is less than or equal to the preset voltage range.

6. The power supply circuit of any one of claims 1 to 5, wherein, Two bus switch tubes are turned on / off with a preset duty ratio, which is calculated by the following formula: V md = u dc + i s *R s ; D = V md / (U max -U min ) ； Wherein, 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; D is the preset 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.

7. The power supply circuit of claim 4, wherein, When the bus voltage is less than the preset voltage threshold, a target modulation voltage increases from 0 to a target voltage at a first preset slope. When the bus voltage is greater than or equal to the preset voltage threshold and less than the preset voltage range, the target modulation voltage is increased from the current voltage to the target voltage at a second preset slope, wherein the target voltage is within the preset voltage range.

8. The power supply circuit of any one of claims 1 to 7, wherein, The power input end comprises three-phase power input ends, and the input filter circuit comprises three input filter inductors and three input filter capacitors; first ends of the three input filter inductors are respectively connected to corresponding three-phase power input ends; second ends of each input filter inductor are connected to an input filter capacitor. The soft start circuit comprises at least two switch components; one of the two switch components is connected in series with one of the three input filter capacitors, and the other of the two switch components is connected in series with another of the three input filter capacitors.

9. The power supply circuit of claim 1 or 8, wherein, The soft start circuit comprises two switch components, i.e., a first switch component and a second switch component; a first end of the first switch component is connected to a power input end of the three-phase power input ends; a first end of the second switch component is connected to another power input end of the three-phase power input ends; and a second end of the first switch component is connected to a second end of the second switch component.

10. The power supply circuit of claim 9, wherein, The first switch component comprises a first current-limiting resistor and a first switch piece connected in parallel; and the second switch component comprises a second current-limiting resistor and a second switch piece connected in parallel. The first switch component comprises a first switch piece; and the second switch component comprises a second current-limiting resistor and a second switch piece connected in parallel.

11. The power supply circuit of claim 9 or 10, wherein, The first switch component comprises a first switch piece; and the second switch component comprises a second current-limiting resistor and a second switch piece connected in parallel.

12. A control method of a power supply circuit, wherein, The control method of the power supply circuit is based on the power supply circuit according to any one of claims 1 to 11, and the control method of the power supply circuit comprises: acquiring a voltage of the input filter circuit and three-phase alternating voltages input to the power input end; when the voltage of the input filter circuit is less than the three-phase alternating voltages input to the power input end, controlling the soft start circuit to limit a current flowing into the input filter circuit within a preset current range.

13. The control method of the power supply circuit according to claim 12, wherein when the voltage of the input filter circuit reaches the three-phase alternating voltages input to the power input end, the control method of the power supply circuit further comprises: acquiring a bus voltage and controlling a working state of the power supply circuit according to a size relationship between the bus voltage and a preset voltage range.

14. The control method of the power supply circuit according to claim 13, wherein The step of controlling the working state of the power supply circuit according to the size relationship between the bus voltage and the preset voltage range specifically comprises: when the bus voltage is less than a preset voltage threshold, controlling one of the two bus switch tubes to be turned on / off at a preset first duty ratio and controlling the other of the two bus switch tubes to be turned on / off at a preset second duty ratio; and when the bus voltage is greater than or equal to the preset voltage threshold, controlling one of the two bus switch tubes to be turned on / off at a preset third duty ratio and controlling the other of the two bus switch tubes to be turned on / off at a preset fourth duty ratio.

15. A control device, wherein, The control device comprises a memory, a processor, and a control program of the power supply circuit stored on the memory and executable on the processor, and the control program of the power supply circuit is configured to implement the steps of the control method of the power supply circuit according to any one of claims 12 to 14.

16. A refrigeration appliance, wherein, The refrigeration equipment comprises the power supply circuit according to any one of claims 1 to 11, and / or comprises the control device according to claim 15.

17. The refrigeration appliance of claim 16, wherein, The refrigeration equipment comprises an air conditioner.

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