Three-phase step-down PFC circuit, circuit board, controller and air conditioner

Abstract

The utility model discloses a three-phase step-down PFC circuit, a circuit board, a controller and an air conditioner, the three-phase step-down PFC circuit comprises an oscillation absorption module, an input filtering module, a rectification module, an output switch module and an output filtering module, the input filtering module comprises three input filtering inductors and three input filtering capacitors; the rectifier module comprises three rectifier bridge arms, and the midpoints of the three rectifier bridge arms are respectively connected to the connecting points of the three input filter capacitors and the three input filter inductors; the oscillation absorption module comprises at least two absorption units, the absorption units are arranged between the input filter inductor and the alternating current power supply, and each absorption unit comprises a first switch and a buffer resistor which are connected in parallel; the output switch module is arranged between the output end anode of the rectification module and the output filtering module. Secondary damage of electric control can be effectively avoided, power-on oscillation of the input filtering module is reduced, and operation reliability of the circuit is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of air conditioner circuits, in particular to a three-phase buck-type PFC circuit, a circuit board, a controller and an air conditioner. Background Art

[0002] At present, in an air conditioner, the carrier frequency of the fan is high and the voltage requirement is low. Generally, it is more suitable to use a switching device with low voltage stress, such as a switching device with a withstand voltage requirement of 600V to 650V; moreover, for the topology of a three-phase BUCK active PFC circuit, in an application scenario of 220V, due to cost considerations, the withstand voltage requirements of the bus capacitor, the compressor drive IPM module, and the fan drive IPM module are selected to be about 600V to 650V.

[0003] However, when a switching device in the PFC circuit, such as an IGBT, has a short-circuit fault, the capacitor at the back end may cause the voltage of the bus capacitor to continuously be higher than 650V, which may cause secondary damage to the electronic control. If an electrolytic capacitor is selected, there is a risk of fire; at the same time, for the topology with an LC filter circuit at the front end, when accessing the power grid, the inductor current and capacitor voltage of the filter circuit will have a severe oscillation at its resonance frequency point, and the voltage amplitude may reach about twice the input voltage. At this time, there is a reliability risk for the electronic control of the air conditioner. Summary of the Utility Model

[0004] The purpose of the utility model is to at least solve one of the technical problems existing in the prior art, and provide a three-phase buck-type PFC circuit, a circuit board, a controller and an air conditioner, which can effectively avoid secondary damage to the electronic control, reduce the power-on oscillation of the input filter module, and improve the operation reliability of the circuit.

[0005] In a first aspect, an embodiment of the utility model provides a three-phase buck-type PFC circuit, including an oscillation absorption module, an input filter module, a rectification module, an output switching module and an output filter module, where:

[0006] The input filter module includes three input filter inductors and three input filter capacitors. One ends of the three input filter inductors are respectively used to access an AC power supply, and the other ends of the three input filter inductors are respectively connected to the three input filter capacitors;

[0007] The rectification module includes three rectifier bridge arms, and the midpoints of the three rectifier bridge arms are respectively connected to the connection points of the three input filter capacitors and the three input filter inductors;

[0008] The output filter module is connected between the positive output terminal and the negative output terminal of the rectification module;

[0009] The oscillation absorption module includes at least two absorption units, which are arranged between the input filter inductor and the AC power supply. Each absorption unit includes a first switch and a buffer resistor connected in parallel.

[0010] The output switch module is arranged between the positive output terminal of the rectification module and the output filter module.

[0011] According to the three-phase buck-type PFC circuit provided by the embodiments of the present invention, it has at least the following beneficial effects: By arranging an oscillation absorption module at the front end of the input filter module and an output switch module between the positive output terminal of the rectification module and the output filter module, when a short-circuit fault occurs in the switching device in the PFC circuit, resulting in the capacitor voltage in the output filter module being continuously higher than 650V, the output switch module can be disconnected to prevent the high-voltage DC in the output filter module from being applied to each switching device of the rectification module, avoiding secondary damage to the electronic control. In addition, the first switch in the oscillation absorption module can be disconnected to cut off the direct connection between the rectification module and the AC power input, so that the rectification module will not be at risk of secondary damage on both the input side and the output side; moreover, when the PFC circuit is initially connected to the three-phase AC power supply, at least two-phase AC power supplies first pass through the buffer resistor and then are input to the input filter module, reducing the oscillation of the current flowing through the input filter inductor and the voltage applied across the input filter capacitor during the initial power-on stage. After the PFC circuit operates stably, the buffer resistor is short-circuited by closing the first switch to reduce the circuit loss; this three-phase buck-type PFC circuit can effectively avoid secondary damage to the electronic control, reduce the power-on oscillation of the input filter module, and improve the operation reliability of the circuit.

[0012] According to the three-phase buck-type PFC circuit provided by some embodiments of the present invention, the output filter module includes an output filter inductor and an output filter capacitor connected in series, and the output switch module includes a second switch connected between the positive output terminal of the rectification module and the output filter inductor.

[0013] According to the three-phase buck-type PFC circuit provided by some embodiments of the present invention, the first switch and the second switch are relays.

[0014] According to the three-phase buck-type PFC circuit provided by some embodiments of the present invention, the buffer resistor is a PTC resistor.

[0015] According to the three-phase buck-type PFC circuit provided by some embodiments of the present invention, it further includes a freewheeling diode. The positive electrode of the freewheeling diode is connected to the negative output terminal of the rectification module, and the negative electrode of the freewheeling diode is connected to the connection point between the output switch module and the output filter module.

[0016] According to the three - phase buck - type PFC circuit provided by some embodiments of the present utility model, it further includes a switch self - starting circuit. The switch self - starting circuit includes an energy - storage capacitor bank, a third switch, and a switching power supply. The energy - storage capacitor bank includes a first electrolytic capacitor and a second electrolytic capacitor. One end of the first electrolytic capacitor is respectively connected to one end of the output filter capacitor, one end of the switching power supply, and the connection point between one of the input filter inductors and the absorption unit. The other end of the first electrolytic capacitor is connected to one end of the second electrolytic capacitor and one end of the third switch. The other end of the second electrolytic capacitor is connected to the other end of the output filter capacitor and the other end of the switching power supply. The other end of the third switch is connected to the connection point of the three input filter capacitors.

[0017] According to the three - phase buck - type PFC circuit provided by some embodiments of the present utility model, when a short - circuit fault occurs in the switching device in the rectification module, the output switch module is controlled to disconnect.

[0018] The first - aspect embodiment of the present utility model also provides a three - phase buck - type PFC circuit, including:

[0019] An EMI filtering module, including three EMI filtering capacitors respectively connected to a three - phase AC power supply;

[0020] An oscillation absorption module, including at least two absorption units. Each absorption unit includes a first branch and a second absorption branch connected in parallel. The first branch includes a first switch, and the second absorption branch includes a fourth switch and a buffer resistor connected in series;

[0021] An input filtering module, including three input filter inductors and three input filter capacitors. One end of the three input filter inductors is respectively used to connect to a three - phase AC power supply, and the other ends of the three input filter inductors are respectively connected to the three input filter capacitors. The oscillation absorption module is located between the EMI filtering module and the input filtering module. One end of the absorption unit is connected to the EMI filtering capacitor, and the other end is connected to the input filter inductor;

[0022] A rectification module, including three rectification bridge arms. The mid - points of the three rectification bridge arms are respectively connected to the connection points between the three input filter capacitors and the three input filter inductors;

[0023] An output filtering module, connected between the positive output terminal and the negative output terminal of the rectification module;

[0024] Wherein, when a short - circuit fault occurs in the switching device in the rectification module, the first switch and the fourth switch are controlled to disconnect.

[0025] Second aspect, an embodiment of the present invention provides a circuit board, including the three-phase buck-type PFC circuit described in the first aspect embodiment above.

[0026] Third aspect, an embodiment of the present invention provides a controller, including the circuit board described in the second aspect embodiment above.

[0027] Fourth aspect, an embodiment of the present invention provides an air conditioner, including the controller described in the third aspect embodiment above.

[0028] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures specifically pointed out in the specification, claims, and drawings. Description of the Drawings

[0029] The drawings are used to provide a further understanding of the technical solutions of the present invention, and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation to the technical solutions of the present invention.

[0030] The present invention will be further described below in conjunction with the drawings and embodiments;

[0031] Figure 1 is the circuit schematic diagram of the three-phase buck-type PFC circuit provided by an embodiment of the present invention;

[0032] Figure 2 is the schematic diagram of the oscillation waveform of the LC filter circuit when the conventional three-phase buck-type PFC circuit in the related art is connected to the power grid;

[0033] Figure 3 is the schematic diagram of the oscillation waveform of the input filter module when the three-phase buck-type PFC circuit provided by the embodiment of the present invention is connected to the power grid;

[0034] Figure 4 is the circuit schematic diagram of the three-phase buck-type PFC circuit provided by another embodiment of the present invention;

[0035] Figure 5 is the circuit schematic diagram of the three-phase buck-type PFC circuit provided by yet another embodiment of the present invention. Detailed Embodiments

[0036] This section will describe in detail the specific embodiments of the present utility model. The preferred embodiments of the present utility model are shown in the accompanying drawings. The role of the drawings is to supplement the description in the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present utility model. However, it should not be construed as a limitation on the protection scope of the present utility model.

[0037] In the description of the embodiments of the present utility model, the meaning of "several" is one or more, the meaning of "multiple" is two or more. Understandings such as "greater than", "less than", "exceeding", etc. do not include the recited number, and understandings such as "above", "below", "within", etc. include the recited number. "At least one" means one or more, and "at least one of the following" and its similar expressions refer to any combination of these items, including any combination of single items or plural items. If there is a description of "first", "second", etc., it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0038] It should be noted that words such as "set", "installed", "connected", etc. in the embodiments of the present utility model should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meanings of the above words in the embodiments of the present utility model in combination with the specific content of the technical solution. For example, the term "connected" can be a mechanical connection, an electrical connection, or a connection that can communicate with each other; it can be directly connected or indirectly connected through an intermediate medium.

[0039] It should be noted that the technical features involved in the various embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0040] The PFC circuits used in three-phase air conditioners include passive PFC circuits, three-phase BOOST active PFC circuits, and three-phase BUCK active PFC circuits. Among them, the passive PFC circuit needs to use a large-inductance reactor to suppress current harmonics; the bus voltage of the three-phase BOOST active PFC circuit is generally greater than the peak line voltage; for the three-phase BUCK active PFC circuit, the rectifier part usually selects switching devices with a withstand voltage requirement of 800V to 1200V.

[0041] At present, in an air conditioner, the carrier frequency of the fan is high and the voltage requirement is low. Usually, it is more suitable to use a switching device with low voltage stress, such as a switching device with a withstand voltage requirement of 600V to 650V. Moreover, for the topology of a three-phase buck active PFC circuit, in an application scenario of 220V, the withstand voltage requirements of the bus capacitor, the compressor drive IPM module, and the fan drive IPM module are selected to be around 600V to 650V for cost considerations. However, when a switching device in the PFC circuit, such as an IGBT, has a short-circuit fault, the capacitor at the back end may cause the voltage of the bus capacitor to continuously be higher than 650V, which may cause secondary damage to the electronic control. If an electrolytic capacitor is selected, there is a risk of fire. At the same time, for the topology with an LC filter circuit at the front end, when connecting to the power grid, the inductor current and capacitor voltage of the filter circuit will have a severe oscillation at its resonance frequency point, and the voltage amplitude may reach about twice the input voltage. At this time, there is a reliability risk for the electronic control of the air conditioner.

[0042] Based on this, the embodiments of the present invention provide a three-phase buck PFC circuit, a control method, an operation control device, an air conditioner, and a computer-readable storage medium, which can effectively avoid secondary damage to the electronic control, reduce the power-on oscillation of the input filter module (200), and improve the operation reliability of the circuit.

[0043] The following further elaborates on the embodiments of the present invention with reference to the accompanying drawings.

[0044] Referring to Figure 1 , an embodiment of the first aspect of the present invention provides a three-phase buck PFC circuit, including an oscillation absorption module 100, an input filter module 200, a rectification module 300, an output switch module 400, and an output filter module 500, where:

[0045] The input filtering module 200 includes three input filtering inductors and three input filtering capacitors. One end of each of the three input filtering inductors is used to connect to an AC power supply, and the other end of each of the three input filtering inductors is respectively connected to the three input filtering capacitors. Specifically, the three input filtering inductors are input filtering inductor L1, input filtering inductor L2, and input filtering inductor L3, and the three input filtering capacitors are input filtering capacitor C1, input filtering capacitor C2, and input filtering capacitor C3. One end of input filtering inductor L1 is used to connect to phase A of the three-phase AC power supply, and the other end of input filtering inductor L1 is connected to one end of input filtering capacitor C1. One end of input filtering inductor L2 is used to connect to phase B of the three-phase AC power supply, and the other end of input filtering inductor L2 is connected to one end of input filtering capacitor C2. One end of input filtering inductor L3 is used to connect to phase C of the three-phase AC power supply, and the other end of input filtering inductor L3 is connected to one end of input filtering capacitor C3. It should be noted that the three input filtering capacitors can be connected in a star configuration or a delta configuration. When connected in a star configuration, as shown in Figure 1 the other ends of input filtering capacitor C1, input filtering capacitor C2, and input filtering capacitor C3 are connected together. When connected in a delta configuration: the other end of input filtering capacitor C1 is connected to the connection point between input filtering inductor L2 and input filtering capacitor C2, the other end of input filtering capacitor C2 is connected to the connection point between input filtering inductor L3 and input filtering capacitor C3, and the other end of input filtering capacitor C3 is connected to the connection point between input filtering inductor L1 and input filtering capacitor C1;

[0046] The oscillation absorption module 100 includes at least two absorption units 110. The absorption units 110 are arranged between the input filtering inductor and the AC power supply. The absorption unit 110 includes a first switch Km and a buffer resistor Rm connected in parallel. Specifically, Figure 1 the oscillation absorption module 100 in the three-phase buck-type PFC circuit shown in includes two absorption units 110. One absorption unit 110 is connected between the phase A AC power supply and input filtering inductor L1, and the other absorption unit 110 is connected between the phase C AC power supply and input filtering inductor L3. It can be understood that in another embodiment, the absorption unit 110 between the phase A AC power supply and input filtering inductor L1 can be arranged between the phase B AC power supply and input filtering inductor L2. In yet another embodiment, the absorption unit 110 between the phase C AC power supply and input filtering inductor L3 can also be arranged between the phase B AC power supply and input filtering inductor L2. It can also be understood that the oscillation absorption module 100 includes three absorption units 110, and the three absorption units 110 are respectively arranged between the phase A AC power supply and input filtering inductor L1, between the phase B AC power supply and input filtering inductor L2, and between the phase C AC power supply and input filtering inductor L3;

[0047] The rectification module 300 includes three rectifier bridge arms, and the midpoints of the three rectifier bridge arms are respectively connected to the connection points of three input filter capacitors and three input filter inductors; specifically, as Figure 1 shown, the three rectifier bridge arms are respectively: the first rectifier bridge arm corresponding to phase A, the second rectifier bridge arm corresponding to phase B, and the third rectifier bridge arm corresponding to phase C. Among them, the first rectifier bridge arm includes a second diode D2, a second switching tube Q2, a first switching tube Q1, and a first diode D1 connected in sequence. The connection point between the second switching tube Q2 and the first switching tube Q1 serves as the midpoint of the first rectifier bridge arm; the second rectifier bridge arm includes a fourth diode D4, a fourth switching tube Q4, a third switching tube Q3, and a third diode D3 connected in sequence. The connection point between the fourth switching tube Q4 and the third switching tube Q3 serves as the midpoint of the second rectifier bridge arm; the third rectifier bridge arm includes a sixth diode D6, a sixth switching tube Q6, a fifth switching tube Q5, and a fifth diode D5 connected in sequence. The connection point between the sixth switching tube Q6 and the fifth switching tube Q5 serves as the midpoint of the third rectifier bridge arm; therefore, the connection point of the input filter inductor L1 and the input filter capacitor C1 is connected to the connection point between the second switching tube Q2 and the first switching tube Q1, the connection point of the input filter inductor L2 and the input filter capacitor C2 is connected to the connection point between the fourth switching tube Q4 and the third switching tube Q3, and the connection point of the input filter inductor L3 and the input filter capacitor C3 is connected to the connection point between the sixth switching tube Q6 and the fifth switching tube Q5; in addition, the negative electrodes of the first diode D1, the third diode D3, and the fifth diode D5 are connected together and serve as the positive pole of the output end of the rectification module 300, and the positive electrodes of the second diode D2, the fourth diode D4, and the sixth diode D6 are connected together and serve as the negative pole of the output end of the rectification module 300;

[0048] The output filter module 500 is connected between the positive pole and the negative pole of the output end of the rectification module 300; specifically, referring to Figure 1 , the output filter module 500 includes an output filter inductor Ls and an output filter capacitor Cs connected in series, that is, one end of the output filter inductor Ls is connected to the positive pole of the output end of the rectification module 300, the other end of the output filter inductor Ls is connected to one end of the output filter capacitor Cs, and the other end of the output filter capacitor Cs is connected to the negative pole of the output end of the rectification module 300;

[0049] The output switch module 400 is arranged between the positive pole of the output end of the rectification module 300 and the output filter module 500; specifically, referring to Figure 1 , the output switch module 400 includes a second switch K2 connected between the positive pole of the output end of the rectification module 300 and the output filter inductor Ls.

[0050] According to the three-phase buck-type PFC circuit provided by the embodiments of the present utility model, an oscillation absorption module 100 is provided at the front end of the input filter module 200, and an output switch module 400 is provided between the positive pole of the output of the rectification module 300 and the output filter module 500. Thus, when a short-circuit fault occurs in the switching device in the PFC circuit, resulting in the capacitor voltage in the output filter module 500 continuously being higher than 650V, the output switch module 400 can be disconnected to prevent the high-voltage direct current in the output filter module 500 from being applied to each switching device of the rectification module 300, avoiding secondary damage to the electronic control. In addition, the first switch Km in the oscillation absorption module 100 can be disconnected to cut off the direct connection between the rectification module 300 and the AC power input, so that the rectification module 300 will not be at risk of secondary damage on both the input side and the output side; moreover, when the PFC circuit is initially connected to a three-phase AC power supply, at least two-phase AC power supplies first pass through the buffer resistor Rm and then are input to the input filter module 200, reducing the oscillation of the current flowing through the input filter inductor and the voltage applied across the input filter capacitor during the early power-on stage. After the PFC circuit operates stably, the buffer resistor Rm is short-circuited by closing the first switch Km to reduce the circuit loss; this three-phase buck-type PFC circuit can effectively avoid secondary damage to the electronic control, reduce the power-on oscillation of the input filter module 200, and improve the operation reliability of the circuit.

[0051] Referring to Figure 2 , Figure 2 is a schematic diagram of the oscillation waveform of the LC filter circuit when a conventional three-phase buck-type PFC circuit in the related art is connected to the power grid. Among them, the three waveform diagrams from top to bottom are the waveforms of the three-phase input voltage, the capacitor voltage in the LC filter circuit, and the inductor current in the LC filter circuit, respectively. Figure 3 is a schematic diagram of the oscillation waveform of the input filter module 200 when the three-phase buck-type PFC circuit provided by the embodiments of the present utility model is connected to the power grid. The three waveform diagrams from top to bottom are the waveforms of the three-phase input voltage, the voltage waveform of the input filter capacitor in the input filter module 200, and the current waveform of the input filter inductor in the input filter module 200. Combining Figure 2 and Figure 3 for comparison, it can be clearly seen that the oscillation conditions of the capacitor voltage and the inductor current are effectively reduced.

[0052] In the three-phase buck-type PFC circuit provided by some embodiments of the present utility model, the first switch Km and the second switch K2 are relays. It can be understood that using relays for the first switch Km and the second switch K2 can meet the requirements of the circuit control performance while reducing the circuit cost.

[0053] In the three-phase buck-type PFC circuit provided by some embodiments of the present utility model, the buffer resistor Rm is a PTC resistor. It can be understood that the resistance value of the PTC resistor shows a stepwise increase as the temperature of the PTC resistor body increases. The higher the temperature, the larger the resistance value. Therefore, using a PTC resistor as the buffer resistor Rm can have a better alleviating effect on the oscillation phenomenon of the input filter module 200 when the three-phase buck-type PFC circuit is connected to the power grid.

[0054] Referring to Figure 1 , in the three-phase buck-type PFC circuit provided by some embodiments of the present utility model, a freewheeling diode D7 is further included. The positive electrode of the freewheeling diode D7 is connected to the negative electrode of the output terminal of the rectification module 300, and the negative electrode of the freewheeling diode D7 is connected to the connection point between the output switching module 400 and the output filter module 500, that is, the negative electrode of the freewheeling diode D7 is connected to the connection point between the second switch K2 and the output filter inductor Ls.

[0055] It can be understood that by setting the freewheeling diode D7, when all the bridge arms in the rectification module 300 are turned off, the output filter module 500 can conduct freewheeling through the freewheeling diode D7.

[0056] Referring to Figure 4 , in the three-phase buck-type PFC circuit provided by some embodiments of the present utility model, a switch self-starting circuit 600 is further included. The switch self-starting circuit 600 includes an energy storage capacitor bank 610, a third switch K3, and a switching power supply 620. The energy storage capacitor bank 610 includes a first electrolytic capacitor C4 and a second electrolytic capacitor C5. One end of the first electrolytic capacitor C4 is respectively connected to one end of the output filter capacitor Cs, one end of the switching power supply 620, and the connection point between one of the input filter inductors and the absorption unit 110. The other end of the first electrolytic capacitor C4 is connected to one end of the second electrolytic capacitor C5 and one end of the third switch K3. The other end of the second electrolytic capacitor C5 is connected to the other end of the output filter capacitor Cs and the other end of the switching power supply 620. The other end of the third switch K3 is connected to the connection point of the input filter capacitor L1, the input filter capacitor L2, and the input filter capacitor L3. Specifically, the third switch K3 uses the normally closed contact of a relay, that is, when the relay is powered off, the third switch K3 is in a closed state, conducting the connection point of the input filter capacitor L1, the input filter capacitor L2, and the input filter capacitor L3 with the connection point of the first electrolytic capacitor C4 and the second electrolytic capacitor C5.

[0057] It should be noted that the switching power supply 620 is connected to one of the three-phase AC power supplies through the third switch K3, so that it can be self-started after the three-phase buck PFC circuit is connected to the AC power supply to supply power to the control module; the switching power supply 620 is also connected across the output filter capacitor Cs, so that after the three-phase buck PFC circuit operates stably, it can obtain power from the output bus of the rectification module 300.

[0058] Referring to Figure 4 , in some embodiments of the present application, the switch self-starting circuit 600 further includes an eighth diode D8 and a ninth diode D9. The anode of the eighth diode D8 is connected to the connection point of the output filter inductor Ls and the output filter capacitor Cs, and the cathode of the eighth diode D8 is connected to the connection point of the first electrolytic capacitor C4 and the switching power supply 620; the anode of the ninth diode D9 is connected to the connection point of the second electrolytic capacitor C5 and the switching power supply 620, and the cathode of the ninth diode D9 is connected to the negative terminal of the output of the rectification module 300. Since the output bus of the rectification module 300 is used to supply power to the load, when the load suddenly drops, the voltage of the output bus of the rectification module 300 will be pulled up. At this time, the eighth diode D8 and the ninth diode D9 will be turned on, and the energy storage capacitor group 610 composed of the first electrolytic capacitor C4 and the second electrolytic capacitor C5 can absorb the suddenly increased energy on the output bus of the rectification module 300, which can well prevent the voltage across the bus capacitor from being pulled up and well prevent the bus voltage from fluctuating greatly, making the circuit operation more stable and reliable.

[0059] It should be noted that both ends of the output filter capacitor Cs of the output filter module 500 are used to connect to the load to supply power to the load; in some embodiments of the present application, for an air-conditioning device, the load may include a compressor and a fan. Among them, the operating power of the compressor is relatively large, and the operating power of the fan is relatively small. Therefore, the compressor can be regarded as a large load, and the fan can be regarded as a small load; among them, the power, the effective value of the input current, and the bus inductor current can be used to determine whether the load is a large load. Exemplarily, if the power is above 1000W, or the effective value of the input current is above 5A, or the bus inductor current is above 5A, the load is considered a large load. Exemplarily, as Figure 4 shown, during the operation of the air conditioner, the compressor is turned off, and the fan is turned off later. Since the compressor is turned off, the load power suddenly drops, causing the bus voltage to suddenly increase.

[0060] It can be understood that the output filter capacitor Cs can be a thin-film capacitor. The thin-film capacitor has good current ripple tolerance, reliability, and lifespan, and is suitable as the output bus capacitor of the rectification module 300. Among them, the thin-film capacitor uses a metal foil as the electrode, and after overlapping it with plastic films such as polyethylene terephthalate, polypropylene, polystyrene, or polycarbonate from both ends, it is wound into a cylindrical structure capacitor. And it is respectively called polyethylene terephthalate capacitor, polypropylene capacitor, polystyrene capacitor, and polycarbonate capacitor according to the type of plastic film. Due to having many excellent characteristics, the thin-film capacitor is an excellent capacitor; its main characteristics are as follows: non-polar, very high insulation impedance, excellent frequency characteristics, broad frequency response, and very small dielectric loss. Based on the above advantages, the thin-film capacitor is widely used in analog circuits. Especially in the part of signal coupling, a capacitor with good frequency characteristics and extremely low dielectric loss must be used to ensure that there is not too much distortion when the signal is transmitted.

[0061] Referring to Figure 4 , the switch self-starting circuit 600 further includes a twelfth diode D10, an eleventh diode D11, and a first resistor R1; the negative electrode of the twelfth diode D10 is connected to the connection point of the first electrolytic capacitor C4 and the switching power supply 620, the positive electrode of the eleventh diode D11 is connected to the connection point of the second electrolytic capacitor C5 and the switching power supply 620, the positive electrode of the twelfth diode D10 and the negative electrode of the eleventh diode D11 are both connected to one end of the first resistor R1, and the other end of the first resistor R1 is connected to the connection point of one of the input filter inductors and the absorption unit 110.

[0062] When the three-phase buck-type PFC circuit is connected to the AC power supply, one of the power supply circuits of the switching power supply 620 is: the third switch K3 - the first electrolytic capacitor C4 - the switching power supply 620 - the eleventh diode D11 - the first resistor R1 - the AC input terminal; the other power supply circuit of the switching power supply 620 is: the first resistor R1 - the twelfth diode D10 - the switching power supply 620 - the second electrolytic capacitor C5 - the third switch K3 - the AC input terminal; through the above settings, the AC signal can flow through the switching power supply 620 no matter which direction it is input from, so as to stably supply power to the switching power supply 620, enabling the switching power supply 620 to achieve self-starting.

[0063] It can be understood that the first resistor R1 can be a thermistor, so that the magnitude of the current can be limited during the power supply to the switching power supply 620, preventing overcurrent and making the circuit safer. Among them, the thermistor in the embodiment of the present application can be a negative temperature coefficient thermistor and a positive temperature coefficient thermistor. A negative temperature coefficient thermistor is a thermosensitive device whose resistance value increases as the temperature decreases. It is composed of a conductive material, usually metal oxide. When the temperature rises, the electron activity inside the conductive material increases, causing the resistance value to decrease; the working principle of the negative temperature coefficient thermistor is based on the temperature characteristics of semiconductor materials; in the negative temperature coefficient thermistor, as the temperature rises, the concentration of charged carriers increases, and the scattering between electrons and the lattice increases, resulting in a decrease in the resistance value, which makes the negative temperature coefficient thermistor suitable for many applications such as temperature measurement, temperature compensation, and current protection. A positive temperature coefficient thermistor is another thermosensitive device whose resistance value changes according to temperature changes; different from the negative temperature coefficient thermistor, the resistance value of the positive temperature coefficient thermistor increases as the temperature rises. It is composed of a conductive polymer material, usually polymer ceramics; the working principle of the positive temperature coefficient thermistor is based on the positive temperature coefficient of the material; in the positive temperature coefficient thermistor, as the temperature rises, the molecular structure inside the polymer chain changes, resulting in an increase in the resistance value, which makes the positive temperature coefficient thermistor suitable for applications such as overcurrent protection, power supply voltage stabilization, and temperature control.

[0064] Referring to Figure 1 and Figure 4 , in the three-phase buck PFC circuit provided by some embodiments of the present invention, when a short-circuit fault occurs in the switching device in the rectification module 300, the control output switching module 400 is disconnected.

[0065] It can be understood that when a short-circuit fault occurs in the switching device in the rectification module 300, since it will cause the capacitor voltage in the output filtering module 500 to continuously be higher than 650V, at this time, controlling the output switching module 400 to disconnect can prevent the high-voltage direct current in the output filtering module 500 from being applied to each switching device of the rectification module 300, avoiding secondary damage to the electronic control.

[0066] Referring to Figure 5 , an embodiment of the first aspect of the present invention also provides a three-phase buck PFC circuit, including: an EMI filtering module 700, an oscillation absorption module 100, an input filtering module 200, a rectification module 300, and an output filtering module 500, where:

[0067] The EMI filtering module 700 includes three EMI filtering capacitors respectively connected to a three-phase AC power supply; specifically, the three EMI filtering capacitors are EMI filtering capacitor C6, EMI filtering capacitor C7, and EMI filtering capacitor C8. One end of EMI filtering capacitor C6 is connected to the A-phase AC power supply, one end of EMI filtering capacitor C7 is connected to the B-phase AC power supply, one end of EMI filtering capacitor C8 is connected to the C-phase AC power supply, and the other ends of EMI filtering capacitor C6, EMI filtering capacitor C7, and EMI filtering capacitor C8 are connected together;

[0068] The oscillation absorption module 100 includes at least two absorption units 110. The absorption unit 110 includes a first branch and a second absorption branch connected in parallel. The first branch includes a first switch Km, and the second absorption branch includes a fourth switch K4 and a buffer resistor Rm connected in series; specifically, Figure 5 The oscillation absorption module 100 in the shown three-phase buck-type PFC circuit includes two absorption units 110. One absorption unit 110 is connected between the A-phase AC power supply and the input filter inductor L1, and the other absorption unit 110 is connected between the C-phase AC power supply and the input filter inductor L3; it can be understood that in another embodiment, the absorption unit 110 between the A-phase AC power supply and the input filter inductor L1 can be arranged between the B-phase AC power supply and the input filter inductor L2; in yet another embodiment, the absorption unit 110 between the C-phase AC power supply and the input filter inductor L3 can also be arranged between the B-phase AC power supply and the input filter inductor L2; it can also be understood that the oscillation absorption module 100 includes three absorption units 110, and the three absorption units 110 are respectively arranged between the A-phase AC power supply and the input filter inductor L1, between the B-phase AC power supply and the input filter inductor L2, and between the C-phase AC power supply and the input filter inductor L3;

[0069] The input filtering module 200 includes three input filter inductors and three input filtering capacitors. One end of the three input filter inductors is respectively used to connect to a three-phase AC power supply, and the other ends of the three input filter inductors are respectively connected to the three input filtering capacitors; the oscillation absorption module 100 is located between the EMI filtering module 700 and the input filtering module 200, and one end of the absorption unit 110 is connected to the EMI filtering capacitor and the other end is connected to the input filter inductor; specifically, refer to Figure 5, the three input filter inductors are input filter inductor L1, input filter inductor L2, and input filter inductor L3 respectively, and the three input filter capacitors are input filter capacitor C1, input filter capacitor C2, and input filter capacitor C3 respectively. One end of the input filter inductor L1 is connected to phase A in the three-phase AC power supply through the absorption unit 110, and the other end of the input filter inductor L1 is connected to one end of the input filter capacitor C1. One end of the input filter inductor L2 is connected to phase B in the three-phase AC power supply, and the other end of the input filter inductor L2 is connected to one end of the input filter capacitor C2. One end of the input filter inductor L3 is connected to phase C in the three-phase AC power supply through the absorption unit 110, and the other end of the input filter inductor L3 is connected to one end of the input filter capacitor C3; among them, the three input filter capacitors can be connected in star or delta; when connected in star, as shown in Figure 5 shown, the other ends of the input filter capacitor C1, the input filter capacitor C2, and the input filter capacitor C3 are connected together; when connected in delta, it is: the other end of the input filter capacitor C1 is connected to the connection point between the input filter inductor L2 and the input filter capacitor C2, the other end of the input filter capacitor C2 is connected to the connection point between the input filter inductor L3 and the input filter capacitor C3, and the other end of the input filter capacitor C3 is connected to the connection point between the input filter inductor L1 and the input filter capacitor C1;

[0070] The rectification module 300 includes three rectifier bridge arms, and the midpoints of the three rectifier bridge arms are respectively connected to the connection points between the three input filter capacitors and the three input filter inductors; specifically, as shown in Figure 5As shown, the three rectifier bridge arms are respectively: the first rectifier bridge arm corresponding to phase A, the second rectifier bridge arm corresponding to phase B, and the third rectifier bridge arm corresponding to phase C. Among them, the first rectifier bridge arm includes a second diode D2, a second switch tube Q2, a first switch tube Q1, and a first diode D1 connected in sequence. The connection point of the second switch tube Q2 and the first switch tube Q1 serves as the midpoint of the first rectifier bridge arm; the second rectifier bridge arm includes a fourth diode D4, a fourth switch tube Q4, a third switch tube Q3, and a third diode D3 connected in sequence. The connection point of the fourth switch tube Q4 and the third switch tube Q3 serves as the midpoint of the second rectifier bridge arm; the third rectifier bridge arm includes a sixth diode D6, a sixth switch tube Q6, a fifth switch tube Q5, and a fifth diode D5 connected in sequence. The connection point of the sixth switch tube Q6 and the fifth switch tube Q5 serves as the midpoint of the third rectifier bridge arm; therefore, the connection point of the input filter inductor L1 and the input filter capacitor C1 is connected to the connection point of the second switch tube Q2 and the first switch tube Q1, the connection point of the input filter inductor L2 and the input filter capacitor C2 is connected to the connection point of the fourth switch tube Q4 and the third switch tube Q3, and the connection point of the input filter inductor L3 and the input filter capacitor C3 is connected to the connection point of the sixth switch tube Q6 and the fifth switch tube Q5; in addition, the negative electrodes of the first diode D1, the third diode D3, and the fifth diode D5 are connected together and serve as the positive output terminal of the rectifier module 300, and the positive electrodes of the second diode D2, the fourth diode D4, and the sixth diode D6 are connected together and serve as the negative output terminal of the rectifier module 300;

[0071] An output filter module 500 is connected between the positive output terminal and the negative output terminal of the rectifier module 300; specifically, referring to Figure 5 , the output filter module 500 includes an output filter inductor Ls and an output filter capacitor Cs connected in series, that is, one end of the output filter inductor Ls is connected to the positive output terminal of the rectifier module 300, the other end of the output filter inductor Ls is connected to one end of the output filter capacitor Cs, and the other end of the output filter capacitor Cs is connected to the negative output terminal of the rectifier module 300;

[0072] In addition, Figure 5 the three-phase buck-type PFC circuit in Figure 1 may further include a switch self-starting circuit 600 with the same structure as

[0073] Among them, when a short - circuit fault occurs in the switching device in the rectification module 300, the first switch Km and the fourth switch K4 are controlled to disconnect.

[0074] It can be understood that Figure 5 the shown three - phase buck - type PFC circuit, compared with Figure 1 the shown three - phase buck - type PFC circuit, does not have an output switch module 400 arranged between the positive output terminal of the rectification module 300 and the output filter module 500, and is additionally provided with an EMI filter module 700, and the EMI filter module 700 is connected to the switch self - start circuit 600. When a short - circuit fault occurs in the switching device in the rectification module 300, the first switch Km and the fourth switch K4 in the oscillation absorption module 100 are controlled to disconnect, so as to cut off the direct connection between the rectification module 300 and the AC power input, so that the rectification module 300 will not be at risk of secondary damage.

[0075] In addition, an embodiment of the second aspect of the present invention provides a circuit board, including the three - phase buck - type PFC circuit described in the above - mentioned first - aspect embodiment.

[0076] In addition, an embodiment of the third aspect of the present invention provides a controller, including the circuit board described in the above - mentioned second - aspect embodiment.

[0077] In addition, an embodiment of the fourth aspect of the present invention provides an air conditioner, including the controller described in the above - mentioned third - aspect embodiment.

[0078] The above has described the embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above - mentioned embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art in the said technical field, various changes can be made without departing from the gist of the present invention.

Claims

1. A three-phase buck PFC circuit, characterized in that: include: An input filter module, comprising three input filter inductors and three input filter capacitors, wherein one end of the three input filter inductors is respectively used to connect to an AC power supply, and the other ends of the three input filter inductors are respectively connected to the three input filter capacitors; A rectifier module, comprising three rectifier bridge arms, wherein the midpoints of the three rectifier bridge arms are respectively connected to the connection points of the three input filter capacitors and the three input filter inductors; An output filter module, connected between the positive output terminal and the negative output terminal of the rectifier module; An oscillation absorption module, comprising at least two absorption units, wherein the absorption unit is arranged between the input filter inductor and the AC power supply, and the absorption unit comprises a first switch and a buffer resistor connected in parallel; The output switch module is arranged between the positive output terminal of the rectifier module and the output filter module.

2. The three-phase buck PFC circuit according to claim 1, characterized in that: The output filter module includes an output filter inductor and an output filter capacitor connected in series, and the output switch module includes a second switch connected between the positive output terminal of the rectifier module and the output filter inductor.

3. The three-phase buck PFC circuit according to claim 2, characterized in that: The first switch and the second switch are relays.

4. The three-phase buck PFC circuit according to claim 1, characterized in that: The buffer resistor is a PTC resistor.

5. The three-phase buck PFC circuit according to claim 1, characterized in that: It also includes a freewheeling diode, the anode of which is connected to the cathode of the output end of the rectifier module, and the cathode of which is connected to the connection point between the output switch module and the output filter module.

6. The three-phase buck PFC circuit according to claim 2, characterized in that: It also includes a switch self-starting circuit, which includes an energy storage capacitor group, a third switch and a switching power supply. The energy storage capacitor group includes a first electrolytic capacitor and a second electrolytic capacitor. One end of the first electrolytic capacitor is respectively connected to one end of the output filter capacitor, one end of the switching power supply and one of the connection points of the input filter inductor and the absorption unit. The other end of the first electrolytic capacitor is connected to one end of the second electrolytic capacitor and one end of the third switch. The other end of the second electrolytic capacitor is connected to the other end of the output filter capacitor and the other end of the switching power supply. The other end of the third switch is connected to the connection points of the three input filter capacitors.

7. The three-phase buck PFC circuit according to claim 1, characterized in that: When a short circuit fault is detected in the switch device in the rectifier module, the output switch module is controlled to be disconnected.

8. A three-phase buck PFC circuit, characterized in that: include: The EMI filter module includes three EMI filter capacitors respectively connected to the three-phase AC power supply; An oscillation absorption module, comprising at least two absorption units, wherein the absorption unit comprises a first branch and a second absorption branch connected in parallel, wherein the first branch comprises a first switch, and the second absorption branch comprises a fourth switch and a buffer resistor connected in series; An input filter module, comprising three input filter inductors and three input filter capacitors, wherein one end of the three input filter inductors is respectively used to connect to a three-phase AC power supply, and the other ends of the three input filter inductors are respectively connected to the three input filter capacitors; The oscillation absorption module is located between the EMI filter module and the input filter module, one end of the absorption unit is connected to the EMI filter capacitor, and the other end is connected to the input filter inductor; A rectifier module, comprising three rectifier bridge arms, wherein the midpoints of the three rectifier bridge arms are respectively connected to the connection points of the three input filter capacitors and the three input filter inductors; An output filter module, connected between the positive output terminal and the negative output terminal of the rectifier module; When a short circuit fault is detected in the switch device in the rectifier module, the first switch and the fourth switch are controlled to be disconnected.

9. A circuit board, characterized in that: A three-phase buck PFC circuit comprising any one of claims 1 to 8.

10. A controller, characterized in that: Including the circuit board described in claim 9.

11. An air conditioner, characterized in that: Comprising the controller as claimed in claim 10.

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