CN115276396A

CN115276396A - Bridgeless PFC circuit with lightning surge protection

Info

Publication number: CN115276396A
Application number: CN202211171578.4A
Authority: CN
Inventors: 胡栋栋; 王长河; 阮洁; 杨勇; 蔡磊
Original assignee: Great Wall Power Technology Co ltd
Current assignee: Great Wall Power Technology Co ltd
Priority date: 2022-09-26
Filing date: 2022-09-26
Publication date: 2022-11-01
Also published as: CN219087002U

Abstract

The invention discloses a bridgeless PFC circuit with lightning surge protection, which relates to the field of power supplies and comprises a bridge type switch unit, wherein the bridge unit comprises a fast tube bridge arm and a slow tube bridge arm, the fast tube bridge arm and the slow tube bridge arm are both connected between a first end and a second end of the bridge type switch unit, a common node of the fast tube bridge arm is used for being connected with an L line of an alternating current source through an inductor, and a common node of the slow tube bridge arm is used for being connected with an N line of the alternating current source; the bus unit is connected with the bridge type switch unit in parallel and comprises a bus capacitor and a first switch tube which are connected in series; the lightning surge protection module is arranged between the alternating current input end and the bridge type switch unit of the bridgeless PFC, so that the limitation of the instantaneous current of a branch circuit of the bus unit during lightning stroke is realized, the lightning surge protection problem of a bus capacitor series switch tube under the bridgeless PFC topology is solved, and the stress of a high-frequency tube and a power frequency switch tube cannot be increased.

Description

Bridgeless PFC circuit with lightning surge protection

Technical Field

The invention relates to the field of power supplies, in particular to a bridgeless PFC circuit with lightning surge protection.

Background

With the rapid development of power electronics technology, the demand of high-efficiency high-power-density switching power supplies is more and more common, and among such power supplies, the application of the bridgeless PFC topology in the high-power-density high-efficiency power supplies is wider and wider due to its excellent efficiency performance.

Meanwhile, in order to further reduce the size of the power supply and improve the power density of the power supply, the power supply is suitable for application (such as liquid cooling) under a special cooling mode at present, but due to the special application environment, a relay connected in series on an alternating current input line needs to be cancelled, and a semiconductor switch tube is connected in series on a bus capacitor at the output end of a PFC module. Because the semiconductor switch tube has the requirement of a safe working area, the lightning stroke protection characteristic aiming at the circuit is particularly critical.

Some of the existing lightning stroke protection circuits are not suitable for the circuit of a bus capacitor series switch tube; some functions of lightning surge protection can be solved, but the functions can not be applied to the bridgeless PFC topology. And extra loss and cost are also brought to solve the surge problem, such as the stress increase of the power frequency tube in the bridgeless PFC.

Disclosure of Invention

The application discloses no bridge PFC circuit with protection of thunderbolt surge includes: the bridge type switch unit comprises a fast tube bridge arm and a slow tube bridge arm, wherein the fast tube bridge arm and the slow tube bridge arm are connected between a first end and a second end of the bridge type switch unit, a common node of the fast tube bridge arm is used for being connected with an L line of an alternating current source through an inductor, and a common node of the slow tube bridge arm is used for being connected with an N line of the alternating current source; the bus unit is connected with the bridge type switch unit in parallel and comprises a bus capacitor and a first switch tube which are connected in series; the lightning surge protection module comprises a diode bridge arm unit and a lightning surge current-limiting resistance unit, wherein the diode bridge arm unit comprises a first diode and a second diode which are connected in series, the first end of the diode bridge arm unit is connected with the first end of the bridge switch unit, the second end of the diode bridge arm unit is connected with the second end of the bridge switch unit, and the lightning surge current-limiting resistance unit is connected in a current path formed by the L line, the first diode and the first end of the bridge switch unit and a current path formed by the second end of the bridge switch unit, the second diode and the L line.

Further, the lightning surge current limiting resistance unit is connected between the common node of the first diode and the second diode and the L line.

Furthermore, the lightning surge current-limiting resistance unit comprises a first lightning surge current-limiting resistance unit and a second lightning surge current-limiting resistance unit, wherein the first lightning surge current-limiting resistance unit is connected between the first diode and the first end of the bridge type switch unit, and the second lightning surge current-limiting resistance unit is connected between the second diode and the second end of the bridge type switch unit.

Furthermore, the first lightning surge current-limiting resistance unit is connected between the cathode of the first diode and the first end of the bridge type switch unit, and the second lightning surge current-limiting resistance unit is connected between the anode of the second diode and the second end of the bridge type switch unit.

Furthermore, the withstand voltage of the first diode and the second diode is larger than the lightning strike voltage.

Furthermore, the impedance of the lightning surge current-limiting resistance unit is far greater than the sum of the equivalent impedance of the bridgeless PFC circuit line and the on-resistance of the first switching tube.

Furthermore, the withstand voltage of two switching tubes in the fast tube bridge arm, the withstand voltage of two switching tubes in the slow tube bridge arm, the withstand voltage of the first diode and the withstand voltage of the second diode are all greater than Vp (Rt + Rdson)/(Rt + Rdson + RL), wherein Vp is lightning voltage, rt is equivalent impedance of a bridgeless PFC circuit line, and Rdson is on-resistance of the first switching tube.

Furthermore, the withstand voltage of two switching tubes in the fast tube bridge arm and the withstand voltage of two switching tubes in the slow tube bridge arm are both greater than Vp (Rt + Rdson)/(Rt + Rdson + RL), wherein Vp is lightning voltage, rt is equivalent impedance of a bridgeless PFC circuit, and Rdson is on-resistance of the first switching tube.

Furthermore, the fast tube bridge arm comprises a plurality of fast tube bridge arms connected in parallel, and a common node of each fast tube bridge arm is used for connecting an L line of an alternating current source through an inductor.

Furthermore, the fast tube bridge arm comprises a first high-frequency tube and a second high-frequency tube which are connected in series, wherein the connection point of the first high-frequency tube and the second high-frequency tube forms a common node of the fast tube bridge arm.

Furthermore, the slow pipe bridge arm comprises a first power frequency pipe and a second power frequency pipe which are connected in series, wherein the connection point of the first power frequency pipe and the second power frequency pipe forms a common node of the slow pipe bridge arm.

Furthermore, the power-on current-limiting resistor is connected with the first switch tube in parallel.

Furthermore, in the working process of the bridgeless PFC circuit, when lightning strikes occur in the positive half period of the AC input, a current path is formed by the L line, the lightning strike surge current-limiting resistance unit, the first diode, the bus capacitor, the first switch tube which is conducted, the lower tube of the slow tube bridge arm and the N line; when lightning stroke occurs in the alternating current input negative half period, the N line, the upper tube of the slow tube bridge arm, the bus capacitor, the conducted first switch tube, the second diode, the lightning stroke surge current-limiting resistance unit and the L line form a current path.

Furthermore, when the bridgeless PFC circuit is started, the L line, the bridge type switch unit, the bus capacitor, the starting current limiting resistor and the N line form a current path.

Furthermore, the size of the starting-up surge current of the bridgeless PFC circuit during starting up is limited by adjusting the resistance value of the starting-up current-limiting resistor connected with the first switching tube in parallel.

Drawings

Fig. 1 is a schematic diagram of a bridgeless PFC circuit with lightning surge protection according to a first embodiment of the present application.

Fig. 2 is a schematic diagram of a bridgeless PFC circuit with lightning surge protection according to a second embodiment of the present application.

Fig. 3 is a schematic diagram of a surge current path in the positive half cycle of the ac input of the bridgeless PFC circuit shown in fig. 1 when a lightning strike occurs.

Fig. 4 is a schematic diagram of a surge current path in the negative half cycle of the ac input of the bridgeless PFC circuit shown in fig. 1 when a lightning strike occurs.

Fig. 5 is a schematic diagram of a bridgeless PFC circuit with lightning surge protection according to a third embodiment of the present application.

Fig. 6 is a schematic diagram of a surge current path in the positive half cycle of the ac input of the bridgeless PFC circuit shown in fig. 5 when a lightning strike occurs.

FIG. 7 is the AC input negative of the bridgeless PFC circuit shown in FIG. 5 and the surge current path is schematic when lightning stroke occurs in a half period.

Detailed Description

The technical solutions in the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

In an embodiment of the present application, please refer to fig. 1, which is a schematic diagram of a bridgeless PFC circuit with lightning surge protection according to a first embodiment of the present application. Bridgeless PFC circuit with lightning surge protection, comprising:

the bridge type switch unit 100 comprises a fast tube bridge arm 110 and a slow tube bridge arm 120, wherein the fast tube bridge arm 110 and the slow tube bridge arm 120 are both connected between a first end A and a second end B of the bridge type switch unit, a common node a of the fast tube bridge arm 110 is used for being connected with an L line of an alternating current source through an inductor L1, and a common node B of the slow tube bridge arm 120 is used for being connected with an N line of the alternating current source;

a bus unit 200 connected in parallel with the bridge switch unit 100, and including a bus capacitor Co and a first switch tube SW1 connected in series;

the lightning surge protection module 300 comprises a diode bridge arm unit 310 and a lightning surge current-limiting resistor unit 320, wherein the diode bridge arm unit 310 comprises a first diode D1 and a second diode D2 which are connected in series, a first end C of the diode bridge arm unit 310 is connected with a first end A of a bridge switch unit 100, a second end D of the diode bridge arm unit 310 is connected with a second end B of the bridge switch unit 100, and the lightning surge current-limiting resistor unit 320 is connected in a current path formed by an L line, the first diode D1 and the first end A of the bridge switch unit 100 and a current path formed by the second end B of the bridge switch unit 100, the second diode D2 and the L line.

Specifically, as shown in fig. 1, a cathode of the first diode D1 forms a first end C of the diode-bridge arm unit 310, an anode of the second diode D2 forms a second end D of the diode-bridge arm unit 310, and an anode of the first diode D1 is connected to a cathode of the second diode D2 to form a common node C of the diode-bridge arm unit 310.

Referring to fig. 1 again, the fast transistor leg 110 includes a first high frequency transistor S1 (also called an upper transistor) and a second high frequency transistor S2 (also called a lower transistor) connected in series, wherein a connection point of the first high frequency transistor S1 and the second high frequency transistor S2 forms a common node a of the fast transistor leg. In general, the switching tubes in the fast tube bridge arm 110 may be semiconductor devices such as MOSFET, gaN, and SIC, as long as they can be controlled to switch between on and off at high frequency.

Specifically, taking the first high-frequency tube S1 and the second high-frequency tube S2 as MOSFETs as an example, the source of the first high-frequency tube S1 is connected to the first end a of the bridge-type switching unit 100, the drain of the first high-frequency tube S1 is connected to the source of the second high-frequency tube S2 to form the common node a of the fast-tube bridge arm, and the drain of the second high-frequency tube S2 is connected to the second end B of the bridge-type switching unit 100.

Referring to fig. 1 again, the slow tube bridge arm 120 includes a first power frequency tube D3 (also called upper tube) and a second power frequency tube D4 (also called lower tube) connected in series, wherein a connection point of the first power frequency tube D3 and the second power frequency tube D4 forms a common node b of the slow tube bridge arm. Generally, the switching tubes in the slow tube bridge arm 120 may be MOSFETs, diodes (as shown in fig. 1), thyristors, bridge rectifier stacks, and other semiconductor devices.

Specifically, taking a first power frequency tube D3 and a second power frequency tube D4 as diodes as an example, a cathode of the first power frequency tube D3 is connected to the first end a of the bridge type switch unit 100, an anode of the first power frequency tube D3 is connected to a cathode of the second power frequency tube D4, so as to form a common node B of a slow tube bridge arm, and an anode of the second power frequency tube D4 is connected to the second end B of the bridge type switch unit 100.

Referring to fig. 2, a bridgeless PFC circuit with lightning surge protection according to a second embodiment of the present invention includes a plurality of parallel-connected fast-tube legs, for example, a first high-frequency tube S1 is connected in series with a second high-frequency tube S2 to form a fast-tube leg, a third high-frequency tube S3 is connected in series with a fourth high-frequency tube S4 to form a fast-tube leg, and a nth high-frequency tube Sn is connected in series with an n +1 th high-frequency tube S n +1 to form a fast-tube leg, where common nodes (a 1 to an) of each fast-tube leg are used to connect an L line of an ac source through an inductor (e.g., an inductor L1 to an inductor Ln).

Referring to fig. 1 again, in an embodiment, the lightning surge current limiting resistance unit RL is connected between the common node c of the first diode D1 and the second diode D2 and the L line.

Referring to fig. 1 again, the bridgeless PFC circuit with lightning surge protection further includes a power-on current-limiting resistor Rp connected in parallel with the first switch SW 1. When the bridgeless PFC circuit is started, the first switch tube SW1 is in a turn-off state, and a current path is formed by an L line, the bridge switch unit 110, the bus capacitor Co, the starting current limiting resistor Rp and an N line. The startup current limiting resistor Rp is a PTC resistor with a positive temperature coefficient, and different resistance values can be selected according to design requirements. At the moment of starting up, the bus capacitor Co is equivalent to a short-circuit state, at the moment, all input voltages are applied to two ends of the starting-up current limiting resistor Rp, and the instantaneous current can enable the starting-up current limiting resistor Rp with the positive temperature coefficient to be increased instantaneously, so that the starting-up surge current can be restrained. In practice, the magnitude of the startup surge current when the bridgeless PFC circuit is started up can be limited by adjusting the resistance value of the startup current-limiting resistor connected with the first switch tube in parallel.

Taking fig. 1 as an example, in the working process of the bridgeless PFC circuit, the first switching tube SW1 is in a conducting state, and bypasses the startup current-limiting resistor Rp.

Specifically, in the working process of the bridgeless PFC circuit, when a lightning strike voltage occurs in the positive half-cycle of the ac input, please refer to the schematic diagram of the surge current path when a lightning strike occurs in the positive half-cycle of the ac input shown in fig. 3. As shown in fig. 3, when a lightning strike occurs in the positive half cycle of the ac input, the L line, the lightning strike surge current limiting resistance unit RL, the first diode D1, the bus capacitor Co, the first switching tube SW1 that is turned on, the lower tube of the slow tube bridge arm (e.g., the second power frequency tube D4 in fig. 3), and the N line form a lightning strike current path. Of course, the current path also includes a line equivalent impedance, which is equivalent to the line equivalent impedance Rt of the bridgeless PFC circuit shown in fig. 3.

The impedance of the lightning surge current limiting resistance unit RL is far greater than the sum of the equivalent impedance Rt of the bridgeless PFC circuit line and the conduction impedance Rdson of the first switching tube. The conduction impedance Rdson of the first switch tube is generally very small, and the line equivalent impedance Rt (or called bridgeless PFC circuit line equivalent impedance Rt) of the PCB is also in the milliohm level, so that the added lightning surge current-limiting resistance unit RL can realize the suppression of the instantaneous current of a bus unit branch in lightning stroke, and the first switch tube connected with a bus capacitor in series is protected. Usually the lightning surge current limiting resistance unit RL is a few ohms or a dozen ohms.

Furthermore, because the impedance of the lightning surge current-limiting resistance unit RL is far greater than the sum of the equivalent impedance Rt of the bridgeless PFC circuit line and the conduction impedance Rdson of the first switch tube, the transient voltage caused by the lightning stroke at the moment mainly acts on the lightning surge current-limiting resistance unit RL, and the high-frequency tube and the power frequency tube in the rear-end bridge type switch unit are reliably clamped by the voltage of the bus capacitor, so that the stress of the high-frequency tube and the power frequency switch tube cannot be increased. Specifically, as shown in fig. 3, the voltages borne by the second high-frequency tube S2, the second diode D2 and the upper tube D3 of the slow tube bridge arm are Vp (Rt + Rdson)/(Rt + Rdson + RL), where Vp is a lightning voltage, rt is an equivalent impedance of the bridgeless PFC circuit, and Rdson is an on-resistance of the first switching tube. This is because the current in the inductor L1 cannot suddenly change, and at the moment of lightning stroke occurring in the positive half cycle of the ac input, the first high-frequency tube S1 is still turned on, and the voltage on the second high-frequency tube S2 and the upper tube D3 of the slow tube bridge arm is also clamped. Therefore, in the actual circuit design, the withstand voltage of the second high-frequency tube S2, the second diode D2 and the upper tube D3 of the slow tube bridge arm needs to be selected to be greater than Vp (Rt + Rdson)/(Rt + Rdson + RL).

Furthermore, as can be seen from the formula Vp (Rt + Rdson)/(Rt + Rdson + RL), when a lightning stroke occurs in the positive half cycle, the voltages at the two ends of the upper tube D3 of the second high-frequency tube S2, the second diode D2 and the slow tube bridge arm are clamped by the divided voltages of the three resistors Rt, rdson and RL, so that the voltages at the two ends of the upper tube D3 of the second high-frequency tube S2, the second diode D2 and the slow tube bridge arm can be changed by adjusting the resistance values of the three resistors. Because the Rdson of the first switch tube SW1 is generally very small, the equivalent resistance of the PCB is also in milliohm level, and once the first switch tube SW1 is selected, the on-resistance Rdson is constant, and the equivalent resistance of the PCB is also fixed, the resistance value of RL can be conveniently adjusted, so that the voltage values borne by the second high-frequency tube S2, the second diode D2 and the two ends of the upper tube D3 of the slow tube bridge arm can be adjusted, that is, the clamping voltage can be adjusted.

Specifically, in the working process of the bridgeless PFC circuit, when a lightning stroke occurs in the ac input negative half-cycle, please refer to the schematic diagram of the surge current path when a lightning stroke occurs in the ac input negative half-cycle shown in fig. 4. As shown in fig. 4, when a lightning stroke occurs in the ac input negative half cycle, the N line, the upper tube (e.g., the first power frequency tube D3 in fig. 4) of the slow tube bridge arm, the bus capacitor Co, the turned-on first switching tube SW1, the second diode D2, the lightning stroke surge current limiting resistance unit RL, and the L line form a lightning stroke current path. Of course, the current path also includes a line equivalent impedance, which is equivalent to the line equivalent impedance Rt of the bridgeless PFC circuit shown in fig. 4.

The added lightning surge current limiting resistance unit RL can realize the suppression of the instantaneous current of the branch circuit of the bus unit during lightning stroke, and therefore the first switch tube connected with the bus capacitor in series is protected.

Furthermore, as the impedance of the lightning surge current-limiting resistance unit RL is far greater than the sum of the equivalent impedance Rt of the bridgeless PFC circuit line and the conducting impedance Rdson of the first switching tube, the transient voltage caused by the lightning strike at the moment basically acts on the lightning surge current-limiting resistance unit RL, and the high-frequency tube and the power frequency tube in the rear-end bridge type switching unit are reliably clamped by the voltage of the bus capacitor, so that the stress of the high-frequency tube and the power frequency switching tube cannot be increased. Specifically, as shown in fig. 4, the voltages borne by the first high-frequency tube S1, the first diode D1 and the second power-frequency tube D4 are Vp (Rt + Rdson)/(Rt + Rdson + RL), where Vp is a lightning voltage, rt is an equivalent impedance of the bridgeless PFC circuit line, and Rdson is an on-resistance of the first switching tube. This is because the current on the inductor L1 cannot suddenly change, and at the moment of lightning stroke occurring in the negative half cycle of the ac input, the second high-frequency tube S2 is still turned on, and the voltages on the first high-frequency tube S1 and the second power-frequency tube D4 are also clamped. Therefore, in the actual circuit design, the withstand voltage of the first high-frequency tube S1, the first diode D1 and the second power frequency tube D4 needs to be selected to be greater than Vp (Rt + Rdson)/(Rt + Rdson + RL).

Similarly, it can be known from the formula Vp: (Rt + Rdson)/(Rt + Rdson + RL), when a lightning strike occurs in the negative half cycle, the voltages at the two ends of the first high-frequency tube S1, the first diode D1 and the second power frequency tube D4 are clamped by the divided voltages of the three resistors Rt, rdson and RL, so that the voltages at the two ends of the first high-frequency tube S1, the first diode D1 and the second power frequency tube D4 can be changed by adjusting the resistance values of the three resistors. Because the Rdson of the first switch tube SW1 is generally very small, the equivalent resistance of the PCB is also in milliohm level, and once the first switch tube SW1 is selected, the on-resistance Rdson is constant, and the equivalent resistance of the PCB is also fixed, the resistance value of RL can be conveniently adjusted, so that the voltage values borne by the two ends of the first high-frequency tube S1, the first diode D1 and the second power-frequency tube D4 can be adjusted, and the clamping voltage can be adjusted.

As can be seen from fig. 3 and fig. 4 and the description thereof, when the instantaneous current of the branch of the bus unit is suppressed during a lightning strike, the voltages borne by the diodes in the diode bridge arm unit 310, the switching tubes in the fast transistor bridge arm 110, and the switching tubes in the slow transistor bridge arm 120 are all clamped, so that the stresses of the fast transistor bridge arm switching tubes (i.e., high-frequency tubes) and the slow transistor bridge arm switching tubes (i.e., power-frequency switching tubes) are not increased. And the circuit is simple, the reliability is high, the cost is low, and no extra loss exists.

And as can be seen from fig. 3 and 4 and the description thereof, the lightning surge current limiting resistance unit RL is connected in the current path formed by the L-line, the first diode D1 and the first terminal a of the bridge switching unit 100, and in the current path formed by the second terminal B of the bridge switching unit 100, the second diode D2 and the L-line.

Referring to fig. 5, a schematic diagram of a bridgeless PFC circuit with lightning surge protection according to a third embodiment of the present application is shown, in which the bridge switch unit 100, the bus bar unit 200, and the diode bridge arm unit 310 are the same as those of the first embodiment and the second embodiment. Unlike the first and second embodiments, the lightning surge current limiting resistance unit 320 includes a first lightning surge current limiting resistance unit RL1 and a second lightning surge current limiting resistance unit RL2, the first lightning surge current limiting resistance unit RL1 is connected between the first diode D1 and the first end a of the bridge switching unit 100, and the second lightning surge current limiting resistance unit RL2 is connected between the second diode D2 and the second end B of the bridge switching unit 100.

Specifically, as shown in fig. 5, a first lightning surge current limiting resistor unit RL1 is connected between the cathode of the first diode D1 and the first end a of the bridge switching unit 100, and a second lightning surge current limiting resistor unit RL2 is connected between the anode of the second diode D2 and the second end B of the bridge switching unit 100.

Specifically, in the working process of the bridgeless PFC circuit, when a lightning stroke occurs in the positive half cycle of the ac input, please refer to fig. 6, which is a schematic diagram of a surge current path when a lightning stroke occurs in the positive half cycle of the ac input of the bridgeless PFC circuit shown in fig. 5. As shown in fig. 6, when a lightning strike occurs in the positive half cycle of the ac input, the L line, the first diode D1, the first lightning strike surge current limiting resistance unit RL1, the bus capacitor Co, the turned-on first switching tube SW1, the lower tube of the slow tube bridge arm (e.g., the second power frequency tube D4 in fig. 6), and the N line form a lightning strike current path. Of course, the current path also includes a line equivalent impedance, which is equivalent to the line equivalent impedance Rt of the bridgeless PFC circuit shown in fig. 6.

Specifically, in the working process of the bridgeless PFC circuit, when a lightning stroke occurs in the ac input negative half-cycle, please refer to fig. 7, which is a schematic diagram of a surge current path when a lightning stroke occurs in the ac input negative half-cycle of the bridgeless PFC circuit shown in fig. 5. As shown in fig. 7, when a lightning stroke occurs in the ac input negative half cycle, the N line, the upper tube (e.g., the first power frequency tube D3 in fig. 7), the bus capacitor Co, the first switching tube SW1, the second lightning stroke surge current limiting resistance unit RL2, the second diode D2, and the L line of the slow tube bridge arm form a lightning stroke current path. Of course, the current path also includes a line equivalent impedance, which is equivalent to the line equivalent impedance Rt of the bridgeless PFC circuit shown in fig. 7.

Similarly, the impedance of the first lightning surge current-limiting resistance unit RL1 and the second lightning surge current-limiting resistance unit RL2 is selected to be far larger than the sum of the equivalent impedance Rt of the bridgeless PFC circuit line and the on-resistance Rdson of the first switch tube, for example, several ohms.

Similarly, the added first lightning surge current-limiting resistance unit RL1 and the added second lightning surge current-limiting resistance unit RL2 can realize suppression of instantaneous current of a bus unit branch during lightning stroke, so that a first switching tube connected in series with a bus capacitor is protected.

As can be seen from the positive half-cycle and negative half-cycle surge current paths, as in the first embodiment, the voltages applied to the first high-frequency tube S1 and the second high-frequency tube S2 of the fast tube bridge arm 110, and the upper tube D3 and the lower tube D4 of the slow tube bridge arm 120 are Vp (Rt + Rdson)/(Rt + Rdson + RL), and therefore, in the actual circuit design, the withstand voltages of the first high-frequency tube S1 and the second high-frequency tube S2 of the fast tube bridge arm 110, the upper tube D3 of the slow tube bridge arm, and the lower tube D4 of the slow tube bridge arm are all greater than Vp (Rt + Rdson)/(Rt + Rdson + RL). That is, the high-frequency tube and the power frequency tube in the rear-end bridge switch unit are reliably clamped by the voltage of the bus capacitor, so that the stress of the high-frequency tube and the power frequency switch tube is not increased.

For this embodiment, since the transient voltage caused by the moment of the lightning strike basically acts on the first lightning surge current limiting resistance unit RL1 and the second lightning surge current limiting resistance unit RL2, the first diode D1 and the second diode D2 are required to bear the lightning strike. Therefore, in the actual circuit design, the withstand voltage of the first diode D1 and the second diode D2 needs to be selected to be larger than the lightning strike voltage.

And as can be seen from fig. 6 and 7 and the description thereof, the lightning surge current limiting resistance unit 320 including the first lightning surge current limiting resistance unit RL1 and the second lightning surge current limiting resistance unit RL2 is connected in a current path formed by the L-line, the first diode D1 and the first end a of the bridge switching unit 100 and in a current path formed by the second end B of the bridge switching unit 100, the second diode D2 and the L-line.

With the bridgeless PFC circuit with lightning surge protection shown in FIG. 1, when the circuit is started, the first switch tube SW1 is turned off, and the startup surge current is suppressed through the startup current-limiting resistor Rp. In the working process, the first switch tube SW1 is conducted, if a lightning strike occurs, the diode bridge arm unit 310, the slow tube bridge arm 120, the lightning strike surge current limiting resistance unit 320 and the bus unit 200 form a current path, so that the instantaneous current of a branch of the bus unit is inhibited during the lightning strike, and the stress of a high-frequency tube and a power-frequency switch tube is not increased.

During normal operation of the bridgeless PFC circuit with lightning surge protection and in the absence of lightning, the first switching tube SW1 is turned on, and the bridge switching unit 100 and the bus bar unit 200 form a power converter that converts AC power received from an AC power source including L-lines and N-lines to DC power on the side of the bus bar unit 200. That is, in the normal working process of the bridgeless PFC circuit, no current flows through both the lightning surge current-limiting resistor unit 320 and the power-on current-limiting resistor Rp, so the loss is low and the efficiency is high.

According to the first, second and third embodiments, the lightning surge protection module is arranged between the alternating current input end and the bridge type switch unit of the bridgeless PFC, so that the limitation of the instantaneous current of the branch of the bus unit during lightning stroke is realized, the problem of lightning surge protection of the bus capacitor series switch tube under the topology of the bridgeless PFC is solved, and the stress of the high-frequency tube and the power frequency switch tube is not increased.

In one embodiment, the bridgeless PFC is a totem pole bridgeless PFC.

The power frequency tube refers to a switching tube for switching power frequency between on and off, namely, the switching frequency is 50HZ. The high-frequency tube refers to a switching tube for switching between on and off at high frequency, for example, the switching frequency is hundreds of hertz, thousands of hertz or more.

The power conversion device formed by the bridgeless PFC circuit with lightning surge protection can adopt a liquid cooling mode, does not have a series relay on an alternating current input line, and is connected with the first switch tube in series on a bus capacitor Co at the output end of the PFC module, so that the function of restraining starting surge current is achieved. Through adopting this lightning surge protection module that this disclosure provided can realize that bus-capacitor establishes ties the lightning surge protection problem of switch tube branch road, and guarantee that first switch tube work is in safe workspace. The circuit is simple, efficient and reliable, and can not increase burden for control.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A bridgeless PFC circuit with lightning surge protection, comprising:

the bridge type switch unit comprises a fast tube bridge arm and a slow tube bridge arm, wherein the fast tube bridge arm and the slow tube bridge arm are connected between a first end and a second end of the bridge type switch unit, a common node of the fast tube bridge arm is used for being connected with an L line of an alternating current source through an inductor, and a common node of the slow tube bridge arm is used for being connected with an N line of the alternating current source;

the bus unit is connected with the bridge type switch unit in parallel and comprises a bus capacitor and a first switch tube which are connected in series;

the lightning surge protection module comprises a diode bridge arm unit and a lightning surge current-limiting resistance unit, wherein the diode bridge arm unit comprises a first diode and a second diode which are connected in series, the first end of the diode bridge arm unit is connected with the first end of the bridge type switch unit, the second end of the diode bridge arm unit is connected with the second end of the bridge type switch unit, and the lightning surge current-limiting resistance unit is connected in a current path formed by the L wire, the first diode and the first end of the bridge type switch unit and a current path formed by the second end of the bridge type switch unit, the second diode and the L wire.

2. The bridgeless PFC circuit with lightning surge protection according to claim 1, wherein a lightning surge current limiting resistance unit is connected between a common node of the first diode and the second diode and the L line.

3. The bridgeless PFC circuit with lightning surge protection according to claim 1, wherein the lightning surge current-limiting resistance unit comprises a first lightning surge current-limiting resistance unit and a second lightning surge current-limiting resistance unit, the first lightning surge current-limiting resistance unit is connected between the first diode and the first end of the bridge switching unit, and the second lightning surge current-limiting resistance unit is connected between the second diode and the second end of the bridge switching unit.

4. The bridgeless PFC circuit with lightning surge protection according to claim 3, wherein a first lightning surge current-limiting resistance unit is connected between a cathode of the first diode and a first end of the bridge switching unit, and a second lightning surge current-limiting resistance unit is connected between an anode of the second diode and a second end of the bridge switching unit.

5. The bridgeless PFC circuit with lightning surge protection according to claim 3, wherein a withstand voltage of the first diode and the second diode is greater than a lightning strike voltage.

6. The bridgeless PFC circuit with lightning surge protection according to claim 1, wherein the impedance of the lightning surge current limiting resistance unit is much greater than the sum of the equivalent impedance of the bridgeless PFC circuit line and the on-resistance of the first switching tube.

7. The bridgeless PFC circuit with lightning surge protection according to claim 2, wherein the withstand voltages of the two switching tubes in the fast tube leg, the two switching tubes in the slow tube leg, the first diode, and the second diode are all greater than Vp (Rt + Rdson)/(Rt + Rdson + RL), where Vp is the lightning voltage, rt is the equivalent line impedance of the bridgeless PFC circuit, and Rdson is the on-resistance of the first switching tube.

8. The bridgeless PFC circuit with lightning surge protection according to claim 3 or 5, wherein the withstand voltage of two switching tubes in the fast tube bridge arm and the withstand voltage of two switching tubes in the slow tube bridge arm are both greater than Vp x (Rt + Rdson)/(Rt + Rdson + RL), wherein Vp is the lightning voltage, rt is the equivalent impedance of the bridgeless PFC circuit line, and Rdson is the on-resistance of the first switching tube.

9. The bridgeless PFC circuit with lightning surge protection according to claim 1, wherein the fast pipe bridge arm comprises a plurality of parallel-connected fast pipe bridge arms, and a common node of each fast pipe bridge arm is used for connecting an L line of an AC source through an inductor.

10. The bridgeless PFC circuit with lightning surge protection according to claim 1 or claim 9, wherein the fast tube bridge arm comprises a first high-frequency tube and a second high-frequency tube connected in series, wherein a connection point of the first high-frequency tube and the second high-frequency tube forms a common node of the fast tube bridge arm.

11. The bridgeless PFC circuit with lightning surge protection according to claim 1, wherein the slow tube bridge arm comprises a first power frequency tube and a second power frequency tube which are connected in series, wherein a connection point of the first power frequency tube and the second power frequency tube forms a common node of a slow tube bridge arm.

12. The bridgeless PFC circuit with lightning surge protection according to claim 1, further comprising a power-on current-limiting resistor, wherein the power-on current-limiting resistor is connected in parallel with the first switching tube.

13. The bridgeless PFC circuit with lightning surge protection according to claim 1 or 12, wherein during operation of the bridgeless PFC circuit, when a lightning strike occurs in a positive half cycle of an AC input, an L line, a lightning surge current-limiting resistance unit, a first diode, a bus capacitor, a first switching tube which is turned on, a lower tube of a slow tube bridge arm and an N line form a current path; when lightning stroke occurs in the alternating current input negative half period, the N line, the upper tube of the slow tube bridge arm, the bus capacitor, the conducted first switch tube, the second diode, the lightning stroke surge current-limiting resistance unit and the L line form a current path.

14. The bridgeless PFC circuit with lightning surge protection according to claim 12, wherein when the bridgeless PFC circuit is powered on, the L line, the bridge switch unit, the bus capacitor, the power-on current limiting resistor, and the N line form a current path.

15. The bridgeless PFC circuit with lightning surge protection according to claim 14, wherein the limitation of the power-on surge current of the bridgeless PFC circuit at power-on is achieved by adjusting a resistance of a power-on current-limiting resistor connected in parallel with the first switching tube.