PFC circuit, circuit board and household appliance

Abstract

The invention discloses a PFC circuit, a circuit board and a household electrical appliance. The PFC circuit comprises a power supply access end, a control end, an inductor, a silicon carbide Schottky diode, a power switch tube, a driving resistor module and a switching speed adjusting module. One end of the inductor is connected to the power supply access end; the positive electrode of the silicon carbide Schottky diode is connected to the other end of the inductor; one switch pin of the power switch tube is connected to the positive electrode of the silicon carbide Schottky diode, and the other switch pin of the power switch tube is grounded; one end of the driving resistor module is connected to the control end, and the other end of the driving resistor module is connected to a control pin of the power switch tube; the switch speed adjusting module is connected to a control pin of the power switch tube so as to adjust the turn-on speed and / or turn-off speed of the power switch tube. According to the PFC circuit, the switching speed of the power switch tube can be improved, and balance can be achieved between reduction of the loss of the power switch tube and mitigation of the EMI problem of the circuit.

Description

Technical Field

[0001] The present invention relates to the field of circuit technologies, and particularly to a PFC circuit, a circuit board and a household appliance. Background Art

[0002] In the field of power electronics, PFC (Power Factor Correction) circuits are widely used in electrical appliances such as air conditioners due to their high power factor correction capabilities. PFC circuit topologies are diverse and their working modes are also different. A typical boost structure is commonly adopted in variable-frequency household appliances. The PFC circuit includes devices such as a storage inductor, a power switch tube, a diode, and a large electrolytic capacitor. The storage inductor stores energy when the power switch tube is turned on, and when the power switch tube is turned off, the storage inductor induces a voltage with the left side negative and the right side positive, so that the energy stored during conduction is used to charge the large electrolytic capacitor through the diode, and the output energy is used to supply power to the load.

[0003] Currently, with the application of silicon carbide power devices, the switching speed of the power switch tube has been continuously improved, which has also led to the problem of thermal loss of the power switch tube. At this time, the loss of the power switch tube can be reduced by adjusting the driving resistance of the control pin of the power switch tube, but this will also bring EMI problems to the circuit. Therefore, how to balance the adjustment of the switching speed of the power switch tube, reduce the loss of the power switch tube, and solve the circuit EMI problem has become one of the major problems faced by PFC. Summary of the Invention

[0004] The purpose of the present invention is to at least solve one of the technical problems existing in the prior art, and provide a PFC circuit, a circuit board and a household appliance, which can improve the switching speed of the power switch tube and can achieve a balance between reducing the loss of the power switch tube and alleviating the circuit EMI problem.

[0005] In a first aspect, an embodiment of the present invention provides a PFC circuit, including a power supply access terminal, a control terminal, an inductor, a silicon carbide Schottky diode, a power switch tube, a driving resistance module, and a switching speed adjustment module, wherein:

[0006] The power supply access terminal is used to access a DC power supply;

[0007] The control terminal is used to access a PWM driving signal;

[0008] One end of the inductor is connected to the power supply access terminal;

[0009] The positive electrode of the silicon carbide Schottky diode is connected to the other end of the inductor;

[0010] One switching pin of the power switch tube is connected to the positive electrode of the silicon carbide Schottky diode, and the other switching pin is grounded;

[0011] One end of the driving resistor module is connected to the control end, and the other end is connected to the control pin of the power switch tube;

[0012] The switching speed adjustment module is connected to the control pin of the power switch tube to adjust the turn-on speed and / or turn-off speed of the power switch tube.

[0013] The PFC circuit provided by the embodiment of the present invention has at least the following beneficial effects: When the power switch tube is turned on, the DC power supply connected to the power input terminal charges the inductor, and when the power switch tube is turned off, the electrical energy stored in the inductor is supplied to the load at the rear end through the silicon carbide Schottky diode; The control end is connected to the PWM drive signal, so as to control the power switch tube to alternately turn on and off through the driving resistor module; By using a silicon carbide Schottky diode for the diode in the PFC circuit, the switching speed of the power switch tube can be improved, so that the selection of the inductance value of the inductor can be reduced; A switching speed adjustment module connected to the control pin of the power switch tube is also provided to adjust the turn-on speed and / or turn-off speed of the power switch tube. Among them, adjusting the turn-on speed of the power switch tube can adjust the oscillation of the circuit current and reduce the EMI problem; Adjusting the turn-off speed of the power switch tube can adjust the discharge speed when the power switch tube is turned off, thereby reducing the heat loss problem; Therefore, after the PFC circuit uses a silicon carbide Schottky diode to improve the switching speed of the power switch tube, the resistance value of the driving resistor module can be adjusted and the turn-on speed and / or turn-off speed of the power switch tube can be adjusted through the switching speed adjustment module, so as to achieve a balance between reducing the loss of the power switch tube and reducing the EMI problem of the circuit.

[0014] In the PFC circuit provided by some embodiments of the present invention, the switching speed adjustment module includes a first resistor and a first diode; The positive electrode of the first diode is connected to the control pin of the power switch tube, and the negative electrode is connected to one end of the first resistor; The other end of the first resistor is connected to the control end.

[0015] In the PFC circuit provided by some embodiments of the present invention, the resistance value of the first resistor is less than the equivalent resistance value of the driving resistor module.

[0016] In the PFC circuit provided by some embodiments of the present invention, the switching speed adjustment module includes a first capacitor, one end of the first capacitor is connected to the control pin of the power switch tube, and the other end is grounded.

[0017] According to the PFC circuit provided by some embodiments of the present invention, the switching speed adjustment module includes a first resistor, a first diode, and a first capacitor; the positive electrode of the first diode and one end of the first capacitor are both connected to the control pin of the power switch tube, and the negative electrode of the first diode is connected to one end of the first resistor; the other end of the first resistor is connected to the control end; the other end of the first capacitor is grounded.

[0018] According to the PFC circuit provided by some embodiments of the present invention, the switching speed adjustment module includes a thermistor for measuring the temperature of the power switch tube, and the thermistor is connected in parallel with the drive resistor module.

[0019] According to the PFC circuit provided by some embodiments of the present invention, the thermistor is located directly below the power switch tube during circuit board layout.

[0020] According to the PFC circuit provided by some embodiments of the present invention, it further includes an absorption buffer module connected in parallel with the silicon carbide Schottky diode, and the absorption buffer module includes a second capacitor and a second resistor connected in series.

[0021] According to the PFC circuit provided by some embodiments of the present invention, the drive resistor module includes a third resistor and a fourth resistor connected in parallel with each other.

[0022] According to the PFC circuit provided by some embodiments of the present invention, it further includes a zener diode and a fifth resistor. The positive electrode of the zener diode and one end of the fifth resistor are connected to the control pin of the power switch tube, and the negative electrode of the zener diode and the other end of the fifth resistor are grounded.

[0023] In a second aspect, an embodiment of the present invention provides a circuit board, including the PFC circuit described in the first aspect embodiment above.

[0024] The circuit board provided by the embodiment of the present invention has at least the following beneficial effects: When the power switch tube is turned on, the DC power supply connected to the power access terminal in the PFC circuit charges the inductor. When the power switch tube is turned off, the electric energy stored in the inductor is supplied to the load at the rear end through the silicon carbide Schottky diode. The control terminal is connected to the PWM drive signal, so as to control the power switch tube to alternately turn on and off through the drive resistance module. By using the silicon carbide Schottky diode for the diode in the PFC circuit, the switching speed of the power switch tube can be increased, so that the selection of the inductance value of the inductor can be decreased. A switching speed adjustment module connected to the control pin of the power switch tube is also provided to adjust the turn-on speed and / or turn-off speed of the power switch tube. Among them, adjusting the turn-on speed of the power switch tube can adjust the oscillation of the circuit current and reduce the EMI problem. Adjusting the turn-off speed of the power switch tube can adjust the discharge speed when the power switch tube is turned off, thereby reducing the heat loss problem. Therefore, after using the silicon carbide Schottky diode to increase the switching speed of the power switch tube in the PFC circuit, the balance between reducing the loss of the power switch tube and reducing the EMI problem of the circuit can be achieved by adjusting the resistance value of the drive resistance module and adjusting the turn-on speed and / or turn-off speed of the power switch tube through the switching speed adjustment module.

[0025] In the third aspect, the embodiment of the present invention provides a household appliance, including the PFC circuit described in the first aspect embodiment above or including the circuit board described in the second aspect embodiment above.

[0026] The household appliance provided by the embodiment of the present invention has at least the following beneficial effects: When the power switch tube is turned on, the DC power supply connected to the power access terminal in the PFC circuit charges the inductor. When the power switch tube is turned off, the electric energy stored in the inductor is supplied to the load at the rear end through the silicon carbide Schottky diode. The control terminal is connected to the PWM drive signal, so as to control the power switch tube to alternately turn on and off through the drive resistance module. By using the silicon carbide Schottky diode for the diode in the PFC circuit, the switching speed of the power switch tube can be increased, so that the selection of the inductance value of the inductor can be decreased. A switching speed adjustment module connected to the control pin of the power switch tube is also provided to adjust the turn-on speed and / or turn-off speed of the power switch tube. Among them, adjusting the turn-on speed of the power switch tube can adjust the oscillation of the circuit current and reduce the EMI problem. Adjusting the turn-off speed of the power switch tube can adjust the discharge speed when the power switch tube is turned off, thereby reducing the heat loss problem. Therefore, after using the silicon carbide Schottky diode to increase the switching speed of the power switch tube in the PFC circuit, the balance between reducing the loss of the power switch tube and reducing the EMI problem of the circuit can be achieved by adjusting the resistance value of the drive resistance module and adjusting the turn-on speed and / or turn-off speed of the power switch tube through the switching speed adjustment module.

[0027] Other features and advantages of the present invention will be described in the following specification, and in part, will be apparent from the specification, or can be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the specification, claims, and drawings. Description of the Drawings

[0028] The drawings are used to provide a further understanding of the technical solutions of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solutions of the present invention, and do not constitute a limitation to the technical solutions of the present invention.

[0029] The present invention will be further described below in conjunction with the drawings and embodiments;

[0030] Figure 1 is the circuit schematic diagram of the PFC circuit provided by the first embodiment of the present invention;

[0031] Figure 2 is the circuit schematic diagram of the PFC circuit provided by the second embodiment of the present invention;

[0032] Figure 3 is the circuit schematic diagram of the PFC circuit provided by the third embodiment of the present invention;

[0033] Figure 4 is the circuit schematic diagram of the PFC circuit provided by the fourth embodiment of the present invention. Detailed Embodiments

[0034] This part will describe the specific embodiments of the present invention in detail. The preferred embodiments of the present invention are shown in the drawings. The role of the drawings is to supplement the description of the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it cannot be understood as a limitation to the protection scope of the present invention.

[0035] In the description of the embodiments of the present invention, the meaning of "several" is one or more, the meaning of "multiple" is two or more, "greater than", "less than", "exceeding", etc. are understood as not including the present number, "above", "below", "within", etc. are understood as including the present 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.

[0036] It should be noted that terms such as "setting", "installing", and "connecting" in the embodiments of the present invention should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meanings of the above terms in the embodiments of the present invention in combination with the specific content of the technical solution. For example, the term "connection" can be a mechanical connection, an electrical connection, or a connection that allows mutual communication; it can be directly connected or indirectly connected through an intermediate medium.

[0037] It should be noted that the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] In the field of power electronics, PFC (Power Factor Correction) circuits are widely used in electrical appliances such as air conditioners due to their high power factor correction capabilities. There are various PFC circuit topologies, and their working modes are also different. A typical boost structure is commonly used in variable-frequency household appliances. The PFC circuit includes devices such as a storage inductor, a power switch transistor, a diode, and a large electrolytic capacitor. The storage inductor stores energy when the power switch transistor is conducting, and when the power switch transistor is cutoff, the storage inductor induces a voltage with the left negative and right positive, so that the energy stored during conduction is used to charge the large electrolytic capacitor through the diode, and the output energy is used to supply power to the load.

[0039] Currently, with the application of silicon carbide power devices, the switching speed of power switch transistors has been continuously improved, which has also led to the problem of thermal loss of power switch transistors. At this time, the loss of power switch transistors can be reduced by adjusting the drive resistance of the control pins of the power switch transistors, but this will also bring EMI problems to the circuit. Therefore, how to balance the adjustment of the switching speed of power switch transistors, reduce the loss of power switch transistors, and solve the circuit EMI problem has become one of the major problems faced by PFC.

[0040] Based on this, the embodiments of the present invention provide a PFC circuit, a circuit board, and a household appliance, which can improve the switching speed of power switch transistors and achieve a balance between reducing the loss of power switch transistors and alleviating the circuit EMI problem.

[0041] The following further elaborates on the embodiments of the present invention with reference to the accompanying drawings.

[0042] Refer to Figures 1 to 4 , the first aspect embodiment of the present invention provides a PFC circuit, including a power supply access terminal DC+, a control terminal PFC-C, an inductor L1, a silicon carbide Schottky diode SBD, a power switch transistor Q1, a drive resistance module 100, and a switching speed adjustment module 200, where:

[0043] The power input terminal DC+ is used to connect to a DC power supply; generally, a rectification module, such as a rectifier bridge stack, is also provided at the front end of the PFC circuit. The input terminal of the rectification module is connected to an AC power supply. After the rectification module rectifies the AC power supply into a DC power supply, it is provided to the power input terminal DC+ from the output terminal of the rectification module;

[0044] The control terminal PFC-C is used to connect to a PWM drive signal; one end of the inductor L1 is connected to the power input terminal DC+; the positive electrode of the silicon carbide Schottky diode SBD is connected to the other end of the inductor L1; one switching pin of the power switch Q1 is connected to the positive electrode of the silicon carbide Schottky diode SBD, that is, connected to the connection point of the silicon carbide Schottky diode SBD and the inductor L1, and the other switching pin of the power switch Q1 is grounded; one end of the drive resistor module 100 is connected to the control terminal PFC-C to obtain the PWM drive signal connected to the control terminal PFC-C, and the other end of the drive resistor module 100 is connected to the control pin of the power switch Q1; the switching speed adjustment module 200 is connected to the control pin of the power switch Q1 to adjust the turn-on speed and / or turn-off speed of the power switch Q1.

[0045] It can be understood that the PFC circuit further includes a large electrolytic capacitor E1 for supplying power to the load at the back end. The positive electrode of the silicon carbide Schottky diode SBD is connected to the positive electrode of the large electrolytic capacitor E1, and the negative electrode of the large electrolytic capacitor E1 is grounded.

[0046] According to the PFC circuit provided by an embodiment of the present invention, when the power switch tube Q1 is turned on, the DC power supply connected to the power access terminal DC+ charges the inductor L1. When the power switch tube Q1 is turned off, the electrical energy stored in the inductor L1 charges the large electrolytic capacitor E1 through the silicon carbide Schottky diode SBD, and then supplies power to the load at the rear end. The control terminal PFC-C is connected to a PWM drive signal, so as to control the power switch tube Q1 to alternately turn on and off through the drive resistance module 100. By using the silicon carbide Schottky diode SBD for the diode in the PFC circuit, the switching speed of the power switch tube Q1 can be increased, so that the inductance selection of the inductor L1 can be decreased. Also, by setting the switching speed adjustment module 200 connected to the control pin of the power switch tube Q1, the turn-on speed and / or turn-off speed of the power switch tube Q1 is adjusted. Among them, adjusting the turn-on speed of the power switch tube Q1 can adjust the oscillation of the circuit current and reduce the EMI problem. Adjusting the turn-off speed of the power switch tube Q1 can adjust the discharge speed when the power switch tube Q1 is turned off, thereby reducing the heat loss problem. Therefore, after the PFC circuit uses the silicon carbide Schottky diode SBD to increase the switching speed of the power switch tube Q1, the balance between reducing the loss of the power switch tube and reducing the EMI problem of the circuit can be achieved by adjusting the resistance value of the drive resistance module 100 and adjusting the turn-on speed and / or turn-off speed of the power switch tube Q1 through the switching speed adjustment module 200.

[0047] Referring to Figure 1 , in the PFC circuit provided by an embodiment of the present invention, the switching speed adjustment module 200 includes a first resistor R1 and a first diode D1. The positive electrode of the first diode D1 is connected to the control pin of the power switch tube Q1, and the negative electrode is connected to one end of the first resistor R1. The other end of the first resistor R1 is connected to the control terminal PFC-C.

[0048] In this embodiment, after the first resistor R1 and the first diode D1 in the switching speed adjustment module 200 are connected in series, they are connected in parallel with the drive resistance module 100. And due to the one-way conduction of the first diode D1, the switching speed adjustment module 200 has no effect when the power switch tube Q1 is turned on and does not affect the turn-on speed of the power switch tube Q1. It can increase the discharge speed when the power switch tube Q1 is turned off, realize fast discharge, increase the turn-off speed of the power switch tube Q1, and thus reduce the heat loss problem brought about by the increase in the switching speed of the power switch tube Q1.

[0049] Referring to Figure 1 , in the PFC circuit provided by some embodiments of the present invention, the resistance value of the first resistor R1 is less than the equivalent resistance value of the drive resistance module 100.

[0050] It can be understood that when the power switch tube Q1 is turned off, due to the small resistance value of the first resistor R1, the current flowing through the first resistor R1 via the first diode D1 is relatively large, so that the rapid turn-off of the power switch tube Q1 can be achieved.

[0051] Referring to Figure 2 , in the PFC circuit provided in another embodiment of the present invention, the switching speed adjustment module 200 includes a first capacitor C1. One end of the first capacitor C1 is connected to the control pin of the power switch tube Q1, and the other end of the first capacitor C1 is grounded, that is, the first capacitor C1 is connected in parallel between the control pin of the power switch tube Q1 and the grounded pin.

[0052] It can be understood that in this embodiment, the provided first capacitor C1 plays a role in energy storage. When the power switch tube Q1 is turned on, the first capacitor C1 needs to be charged first, and the power switch tube Q1 can be turned on only after the voltage across the first capacitor C1 is increased. For the case where the switching speed of the power switch tube Q1 is relatively fast, it can slow down the current change when the power switch tube Q1 is turned on, reduce the oscillation of the circuit current, and thus reduce the EMI problem of the circuit. In addition, it should be noted that when the power switch tube Q1 is turned off, the first capacitor C1 also needs to be discharged first, and the power switch tube Q1 can be turned off only after the voltage across the first capacitor C1 is decreased. Therefore, adding the first capacitor C1 can adjust both the turn-on speed and the turn-off speed of the power switch tube Q1.

[0053] Referring to Figure 3 , in the PFC circuit provided in another embodiment of the present invention, the switching speed adjustment module 200 includes a first resistor R1, a first diode D1 and a first capacitor C1; the positive electrode of the first diode D1 and one end of the first capacitor C1 are both connected to the control pin of the power switch tube Q1, the negative electrode of the first diode D1 is connected to one end of the first resistor R1; the other end of the first resistor R1 is connected to the control terminal PFC-C; the other end of the first capacitor C1 is grounded.

[0054] It can be understood that in this embodiment, the switching speed adjustment module 200 includes both Figure 1 the first resistor R1 and the first diode D1 shown in Figure 2 , and also includes Figure 1 the first capacitor C1 shown in Figure 2The introduction of the embodiment can not only adjust the turn-on speed of the power switch tube Q1, but also adjust the turn-off speed of the power switch tube Q1. Therefore, in this embodiment, the combined setting of the first resistor R1, the first diode D1 and the first capacitor C1 greatly improves the adjustment range of the turn-on speed and the turn-off speed of the power switch tube Q1 in the PFC circuit, can be applied to a variety of different control requirements, and greatly reduces the difficulty of balancing circuit heat loss and EMI problems.

[0055] Referring to Figure 4 , in the PFC circuit provided by another embodiment of the present invention, the switching speed adjustment module 200 includes a thermistor NTC for measuring the temperature of the power switch tube Q1, and the thermistor NTC is connected in parallel with the drive resistance module 100.

[0056] In this embodiment, by using the thermistor NTC to measure the temperature of the power switch tube Q1 and connecting it in parallel with the drive resistance module 100, when the heat loss of the power switch tube Q1 is large and the temperature rises, the temperature of the thermistor NTC also rises. Due to the characteristics of the thermistor NTC, the resistance value of the thermistor NTC decreases, so that the drive resistance of the power switch tube Q1 decreases, thereby reducing the heat loss of the power switch tube Q1. It can be understood that under the adjustment of the thermistor NTC, the heat loss of the power switch tube Q1 will finally reach a stable set value.

[0057] In Figure 4 In the PFC circuit shown, the thermistor NTC is located directly below the power switch tube Q1 when laying out the circuit board. It can be understood that when the thermistor NTC is located directly below the power switch tube Q1 during circuit board layout, the temperature of the power switch tube Q1 can be measured more quickly and accurately, so as to quickly adjust the heat loss of the power switch tube Q1.

[0058] Referring to Figure 1 In Figure 4 , in the PFC circuit provided by some embodiments of the present invention, it further includes an absorption buffer module 300 connected in parallel with the silicon carbide Schottky diode SBD, and the absorption buffer module 300 includes a second capacitor C2 and a second resistor R2 connected in series.

[0059] It can be understood that the series-connected second capacitor C2 and second resistor R2 are set as the absorption buffer module 300, and the absorption buffer module 300 is connected in parallel with the silicon carbide Schottky diode SBD that generates high-frequency noise, which can effectively suppress the high-frequency noise generated by the silicon carbide Schottky diode SBD at the moment of turn-on and turn-off of the power switch tube Q1.

[0060] Referring to Figure 1 In Figure 4, in the PFC circuit provided by some embodiments of the present invention, the driving resistor module 100 includes a third resistor R3 and a fourth resistor R4 connected in parallel with each other.

[0061] Refer to Figure 1 In Figure 4 , in the PFC circuit provided by some embodiments of the present invention, it further includes a zener diode DZ1 and a fifth resistor R5. The positive electrode of the zener diode DZ1 and one end of the fifth resistor R5 are connected to the control pin of the power switch tube Q1, and the negative electrode of the zener diode DZ1 and the other end of the fifth resistor R5 are grounded.

[0062] It can be understood that setting the zener diode DZ1 can play an overvoltage protection role for the power switch tube Q1. When the voltage applied to the control pin of the power switch tube Q1 is too high, the zener diode DZ1 can be broken down, so as to quickly discharge to the ground end, avoiding damage to the power switch tube Q1 under the impact of high voltage; setting the fifth resistor R5 can play a role in potential clamping, so that the potential of the control pin of the power switch tube Q1 remains greater than the potential of the pin of the power switch tube Q1 grounded.

[0063] In a second aspect, an embodiment of the present invention provides a circuit board, including the PFC circuit described in the first aspect embodiment above.

[0064] According to the circuit board provided by the embodiment of the present invention, the DC power supply connected to the power supply access terminal DC+ in the PFC circuit charges the inductor L1 when the power switch tube Q1 is turned on. When the power switch tube Q1 is turned off, the electric energy stored in the inductor L1 is charged to the large electrolytic capacitor E1 through the silicon carbide Schottky diode SBD, and then supplies power to the load at the rear end; the control terminal PFC-C accesses the PWM drive signal, so as to control the power switch tube Q1 to alternately turn on and off through the driving resistor module 100; the diode in the PFC circuit uses the silicon carbide Schottky diode SBD, which can improve the switching speed of the power switch tube Q1, so that the selection of the inductance value of the inductor L1 can be reduced; also, by setting the switching speed adjustment module 200 connected to the control pin of the power switch tube Q1, the turn-on speed and / or turn-off speed of the power switch tube Q1 are adjusted. Among them, adjusting the turn-on speed of the power switch tube Q1 can adjust the oscillation of the circuit current and reduce the EMI problem; adjusting the turn-off speed of the power switch tube Q1 can adjust the discharge speed when the power switch tube Q1 is turned off, thereby reducing the heat loss problem; therefore, after the PFC circuit uses the silicon carbide Schottky diode SBD to improve the switching speed of the power switch tube Q1, the resistance value of the driving resistor module 100 can be adjusted and the turn-on speed and / or turn-off speed of the power switch tube Q1 can be adjusted through the switching speed adjustment module 200, so as to achieve a balance between reducing the loss of the power switch tube and reducing the EMI problem of the circuit.

[0065] In a third aspect, an embodiment of the present invention provides a household appliance, which includes the PFC circuit described in the embodiment of the first aspect above or includes the circuit board described in the embodiment of the second aspect above.

[0066] In the household appliance provided according to the embodiment of the present invention, when the power switch Q1 is turned on, the DC power supply connected to the power access terminal DC+ in the PFC circuit charges the inductor L1. When the power switch Q1 is turned off, the electrical energy stored in the inductor L1 charges the large electrolytic capacitor E1 through the silicon carbide Schottky diode SBD, and then supplies power to the load at the back end. The control terminal PFC-C is connected to a PWM drive signal, so as to control the power switch Q1 to alternately turn on and off through the drive resistor module 100. By using the silicon carbide Schottky diode SBD for the diode in the PFC circuit, the switching speed of the power switch Q1 can be increased, so that the selection of the inductance value of the inductor L1 can be decreased. The switching speed adjustment module 200 connected to the control pin of the power switch Q1 is also provided to adjust the turn-on speed and / or turn-off speed of the power switch Q1. Among them, adjusting the turn-on speed of the power switch Q1 can adjust the oscillation of the circuit current and reduce the EMI problem. Adjusting the turn-off speed of the power switch Q1 can adjust the discharge speed when the power switch Q1 is turned off, thereby reducing the heat loss problem. Therefore, after the PFC circuit uses the silicon carbide Schottky diode SBD to increase the switching speed of the power switch Q1, the balance between reducing the loss of the power switch and reducing the EMI problem of the circuit can be achieved by adjusting the resistance value of the drive resistor module 100 and adjusting the turn-on speed and / or turn-off speed of the power switch Q1 through the switching speed adjustment module 200.

[0067] The embodiments of the present invention have been described in detail above with reference to the drawings. However, the present invention is not limited to the above embodiments. Within the knowledge scope of those of ordinary skill in the art in the technical field, various changes can be made without departing from the purpose of the present invention.

Claims

1. A PFC circuit, characterized in that, Comprising: A power supply access terminal for accessing a DC power supply; A control terminal for accessing a PWM drive signal; An inductor, one end of the inductor being connected to the power supply access terminal; A silicon carbide Schottky diode, the positive electrode of the silicon carbide Schottky diode being connected to the other end of the inductor; A power switch tube, one switching pin of the power switch tube being connected to the positive electrode of the silicon carbide Schottky diode, and the other switching pin being grounded; A drive resistance module, one end of the drive resistance module being connected to the control terminal, and the other end being connected to the control pin of the power switch tube; A switching speed adjustment module, the switching speed adjustment module being connected to the control pin of the power switch tube to adjust the turn-on speed and / or turn-off speed of the power switch tube.

2. The PFC circuit according to claim 1, wherein The switching speed adjustment module includes a first resistor and a first diode; the positive electrode of the first diode is connected to the control pin of the power switch tube, and the negative electrode is connected to one end of the first resistor; the other end of the first resistor is connected to the control terminal.

3. The PFC circuit according to claim 2, wherein The resistance value of the first resistor is less than the equivalent resistance value of the drive resistance module.

4. The PFC circuit according to claim 1, wherein The switching speed adjustment module includes a first capacitor, one end of the first capacitor being connected to the control pin of the power switch tube, and the other end being grounded.

5. The PFC circuit according to claim 1, wherein The switching speed adjustment module includes a first resistor, a first diode and a first capacitor; the positive electrode of the first diode and one end of the first capacitor are both connected to the control pin of the power switch tube, the negative electrode of the first diode is connected to one end of the first resistor; the other end of the first resistor is connected to the control terminal; the other end of the first capacitor is grounded.

6. The PFC circuit according to claim 1, wherein The switching speed adjustment module includes a thermistor for measuring the temperature of the power switch tube, and the thermistor is connected in parallel with the drive resistance module.

7. The PFC circuit according to claim 5, characterized in that, When the circuit board is laid out, the thermistor is located directly below the power switch tube.

8. The PFC circuit according to claim 1, wherein It further includes an absorption buffer module connected in parallel with the silicon carbide Schottky diode, and the absorption buffer module includes a second capacitor and a second resistor connected in series.

9. The PFC circuit according to claim 1, characterized in that, The drive resistance module includes a third resistor and a fourth resistor connected in parallel with each other.

10. The PFC circuit according to claim 1, characterized in that, It further includes a voltage stabilizing diode and a fifth resistor, the positive electrode of the voltage stabilizing diode and one end of the fifth resistor are connected to the control pin of the power switch tube, and the negative electrode of the voltage stabilizing diode and the other end of the fifth resistor are grounded.

11. A circuit board, characterized in that, Comprising the PFC circuit according to any one of claims 1 to 10.

12. A household appliance, characterized in that, Comprising the PFC circuit according to any one of claims 1 to 10 or comprising the circuit board according to claim 11.

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