Switching tube rectifier bridge and PFC circuit and control method thereof

Abstract

The application provides a switching tube rectifier bridge and a PFC circuit and a control method thereof, which comprises a switching tube rectifier bridge, a switching tube rectifier bridge control circuit and a PFC conversion circuit. The switching tube rectifier bridge uses two switching tubes to replace two lower bridge arm diodes of a diode rectifier bridge, and utilizes the characteristic that the conduction voltage drop of the switching tube is much lower than that of the diode to reduce the conduction loss of the rectifier bridge. The PFC circuit is a Boost, Buck-Boost or flyback topology circuit. The application utilizes the power supply and driving signal of the PFC controller to control the conduction and turn-off of the two lower bridge arm switching tubes of the switching tube rectifier bridge, and utilizes the characteristic that the duty cycle of the driving signal changes with the input voltage to adjust the conduction time of the two lower bridge arm switching tubes of the switching tube rectifier bridge, thereby avoiding the micro-conduction of the two lower bridge arm switching tubes when switching at the input voltage zero point, and reducing the input harmonic current.

Description

Technical Field

[0001] This invention relates to the field of AC input power supply applications, and more particularly to a switching transistor rectifier bridge and PFC circuit and its control method. Background Technology

[0002] In applications requiring small size and high power density, such as PD power supplies, it is necessary to improve efficiency and reduce heat generation in order to achieve small size and high power density. Compared with traditional rectifier bridges, switching transistor rectifier bridges can significantly reduce their conduction losses and improve efficiency. In Class C&D compliant applications, such as those with an input power greater than 75W, in order to reduce the power supply's interference with the power grid, the law stipulates that the power supply must meet harmonic current requirements, which inevitably requires the addition of a PFC circuit to reduce the power supply's harmonic current.

[0003] When the switching transistor rectifier bridge and PFC circuit are combined, the traditional control method is complex because each has a different focus. Furthermore, near the zero-crossing point of the input voltage, the rectifier switching transistor is prone to micro-pass during switching, resulting in the generation of large harmonic currents.

[0004] Therefore, it is necessary to provide a switching transistor rectifier bridge and PFC circuit and its control method to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention provides a switching transistor rectifier bridge and PFC circuit and its control method, which solves the problems of traditional control methods being complex and prone to micro-common and harmonic currents near the zero-crossing point of the input voltage.

[0006] The present invention provides a switching transistor rectifier bridge and PFC circuit and its control method, comprising: a switching transistor rectifier bridge, a switching transistor rectifier bridge control circuit and a PFC conversion circuit; The switching rectifier bridge includes a first rectifier diode, a second rectifier diode, a first rectifier switch, and a second rectifier switch; The cathode of the first rectifier diode is connected to the cathode of the second rectifier diode; The anode of the first rectifier diode is connected to the drain of the first rectifier switch transistor; The gate of the first rectifier switch is connected to one end of the first resistor, and the source of the first rectifier switch is connected to the second rectifier switch and together they are connected to the primary ground. The gate of the second rectifier switch is connected to one end of the second resistor, and the drain of the second rectifier switch is connected to the anode of the second rectifier diode; Preferably, the first and second rectifier switches of the switching rectifier bridge can be MOSFETs, or low on-resistance semiconductor switching devices such as gallium nitride and silicon carbide. The switching transistor rectifier bridge control circuit includes a first diode, a second diode, a first resistor, a second resistor, a third resistor, a third capacitor, a fourth switching transistor, and a fifth resistor. The anode of the first diode is connected to the gate of the first rectifier switch and one end of the first resistor, and the cathode of the first diode is connected to the drain of the second rectifier switch. The anode of the second diode is connected to the gate of the second rectifier switch and one end of the second resistor, and the cathode of the second diode is connected to the drain of the first rectifier switch. One end of the first resistor is connected to one end of the second resistor and the third capacitor; One end of the third capacitor is connected to the first resistor, the second resistor, the third resistor, and the fifth resistor, and the other end of the third capacitor is connected to the primary ground; One end of the third resistor is connected to the VCC pin of the PFC controller; One end of the fifth resistor is connected to the drain of the fourth switching transistor; The gate of the fourth switch is connected to the DRV drive pin of the PFC controller, and the source of the fourth switch is connected to the primary ground. Preferably, the fourth switching transistor can be a MOSFET or a transistor. The PFC conversion circuit includes a PFC controller, a first capacitor, a second capacitor, a first inductor, a fifth switching transistor, a current sampling resistor, a seventh diode, and a PFC load.

[0007] Preferably, the PFC controller is a PFC controller with Boost, Buck-boost, flyback, or other topologies, which has a drive duty cycle that is inversely proportional to the input voltage. The lower the input voltage, the larger the duty cycle, and the higher the input voltage, the smaller the duty cycle.

[0008] Preferably, the fifth switch can be a MOSFET, or a semiconductor switching device such as gallium nitride or silicon carbide.

[0009] Preferably, the PFC Load can be a resistive, inductive, or capacitive load, or it can be a DC-DC conversion circuit load such as a flyback, forward, AHB, or LLC resonant half-bridge.

[0010] A control method for a switching transistor rectifier bridge and a PFC circuit includes the following steps: During the S1 and T0~T1 periods, the PFC is in operation. During the positive half-wave AC cycle, the L line voltage is greater than the N line voltage. The input current flows from L through DB1, C1 or inductor L1, back to Q2, and then back to the N line. The parasitic diodes at the DS terminals of Q2 are turned on. The N line voltage is lower than the primary ground voltage, so D1 is turned on, pulling down the Vgs1 voltage and turning Q1 off. The VCC and drive voltage DRV signals of the PFC controller U1 drive Q2 to turn on through R3, R5, C3, Q4, and R2, reducing the losses in the rectifier section. During the S2 and T1~T2 periods, the PFC is still in operation. During the negative half-wave period of AC, the voltage of the N line is greater than that of the L line. The input current flows from N through DB2, C1 or inductor L1, back to Q1, and then back to the L line. The parasitic diode of Q1 at its DS terminal is turned on. The voltage of the L line is lower than that of the primary ground, so D2 is turned on, pulling down the Vgs2 voltage and turning Q2 off. The VCC and drive voltage DRV signal of the PFC controller U1 drive Q1 to turn on through R3, R5, C3, Q4, and R1, reducing the loss of the rectifier section. S3, T2~T3, and T3~T4 repeat the operations of time periods T0~T1 and T1~T2, respectively, which will not be repeated here; When S4 and Q1 are turned on, Q2 will be pulled low through D2 to drive Vgs2. When Q2 is turned on, Q1 will be pulled low through D1 to drive Vgs1. Therefore, it can be ensured that only one switch is fully turned on at the same time, preventing a short circuit between L and N lines caused by Q1 and Q2 being fully turned on at the same time. During periods S5 and T4~T5, the output PFC load is disconnected, reducing output power and causing the PFC to cease operation. The VCC voltage of controller U1 is pulled low, and the drive voltages of Q1 and Q2 are also pulled low. The switching transistor rectifier bridge also ceases operation, which helps reduce drive losses under no-load conditions. At this time, the parasitic diodes at the drain and source terminals of Q1 and Q2, together with DB1 and DB2, form a full-bridge rectifier circuit, completing the rectification of the input AC.

[0011] Compared with related technologies, the switching transistor rectifier bridge and PFC circuit and its control method provided by the present invention have the following beneficial effects: This invention provides a switching transistor rectifier bridge and a PFC circuit and its control method, which has the advantages of simple circuit structure, stability and reliability. It can automatically adjust the conduction state of the switching transistor rectifier bridge according to the working status of the PFC circuit and the drive signal, thus avoiding the micro-common current and input harmonic current problems of the switching transistor rectifier bridge near the zero crossing point of the input voltage. Attached Figure Description

[0012] 101: Switching transistor rectifier bridge 102: Switching transistor rectifier bridge control circuit 103: PFC conversion circuit Figure 1 This is a schematic diagram of a preferred embodiment of a switching transistor rectifier bridge and PFC circuit and its control method provided by the present invention. Figure 2 The circuit proposed in this invention utilizes the PFC ON / OFF signal to control the switching transistor rectifier bridge; Figure 3 The circuit proposed in this invention utilizes a PFC controller to drive and control the switching transistor rectifier bridge. Figure 4 The circuit proposed in this invention utilizes the input voltage to adjust the switching transistor rectifier bridge drive; Figure 5 for Figure 1 Typical operating timing waveform diagram. Detailed Implementation

[0013] Please refer to the following: Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 ,in, Figure 1 This is a schematic diagram of a preferred embodiment of a switching transistor rectifier bridge 101, a PFC circuit, and a control method thereof provided by the present invention. Figure 2 The circuit proposed in this invention utilizes the PFCON / OFF signal to control the switching transistor rectifier bridge 101; Figure 3 The circuit proposed in this invention utilizes a PFC controller to drive and control the switching transistor rectifier bridge 101. Figure 4 The circuit proposed in this invention utilizes the input voltage to adjust the driving of the rectifier bridge 101 and the switching transistor. Figure 5 for Figure 1 Typical operating timing waveform diagram.

[0014] The following is based on Figure 1 and Figure 5 Taking an example, the present invention will be described in further detail below. Figure 2 , Figure 3 , Figure 4 The differences will be explained.

[0015] A switching transistor rectifier bridge 101 and a PFC circuit and its control method are disclosed, comprising: a switching transistor rectifier bridge 101, a switching transistor rectifier bridge control circuit 102, and a PFC conversion circuit 103; the switching transistor rectifier bridge 101 includes a first rectifier diode, a second rectifier diode, a first rectifier switch, and a second rectifier switch; the switching transistor rectifier bridge control circuit 102 includes a first diode, a second diode, a first resistor, a second resistor, a third resistor, a third capacitor, a fourth switch, and a fifth resistor. The PFC conversion circuit 103 includes a PFC controller, a first capacitor, a second capacitor, a first inductor, a fifth switch, a current sampling resistor, a seventh diode, and a PFC load. The switching rectifier bridge 101 utilizes the characteristic that the forward voltage drop of the switching transistor is much lower than that of the diode, reducing rectifier bridge losses and thus improving system efficiency. The PFC conversion circuit 103 is a typical Boost converter structure, which converts the rectified pulsating DC voltage into a fixed and stable DC voltage, while increasing the system's power factor (PF) and reducing input harmonic current. The switching rectifier bridge control circuit 102 uses the VCC power supply of the PFC controller and the DRV drive signal to generate a drive voltage associated with the input voltage, controlling the switching rectifier bridge 101 to turn on and off, and adjusting the magnitude of its drive voltage according to the level of the input voltage.

[0016] Its work sequence flow, refer to Figure 5 This includes the following steps: During the S1 and T0~T1 periods, the PFC is in operation. During the positive half-wave AC cycle, the L line voltage is greater than the N line voltage. The input current flows from L through DB1, C1 or inductor L1, back to Q2, and then back to the N line. The parasitic diode at the DS terminal of Q2 is turned on. The N line voltage is lower than the primary ground voltage, so D1 is turned on, pulling down the Vgs1 voltage and turning Q1 off. The VCC and drive voltage DRV signals of the PFC controller U1 drive Q2 to turn on through R3, R5, C3, Q4, and R2, reducing the losses in the rectifier section. During the S2 and T1~T2 periods, the PFC is still in operation. During the negative half-wave period of AC, the voltage of the N line is greater than that of the L line. The input current flows from N through DB2, C1 or inductor L1, back to Q1, and then back to the L line. The parasitic diode of Q1 at its DS terminal is turned on. The voltage of the L line is lower than that of the primary ground, so D2 is turned on, pulling down the Vgs2 voltage and turning Q2 off. The VCC and drive voltage DRV signal of the PFC controller U1 drive Q1 to turn on through R3, R5, C3, Q4, and R1, reducing the loss of the rectifier section. S3, T2~T3, and T3~T4 repeat the operations of time periods T0~T1 and T1~T2, respectively, which will not be repeated here; When S4 and Q1 are turned on, Q2 will be pulled low through D2 to drive Vgs2. When Q2 is turned on, Q1 will be pulled low through D1 to drive Vgs1. Therefore, it can be ensured that only one switch is fully turned on at the same time, preventing a short circuit between L and N lines caused by Q1 and Q2 being fully turned on at the same time. During periods S5 and T4~T5, the output PFC load is disconnected, the output power decreases, the PFC stops working, the VCC voltage of controller U1 is pulled low, the drive voltages of Q1 and Q2 are also pulled low, and the switching transistor rectifier bridge 101 also stops working, which helps to reduce the drive loss of the switching transistor rectifier bridge 101 under no-load conditions. At this time, the parasitic diodes at the drain and source terminals of Q1 and Q2, together with DB1 and DB2, form a full-bridge rectifier circuit to complete the rectification of the input AC. In a traditional switching rectifier bridge 101, the rectifier switches are prone to micro-conduction during switching when the input voltage crosses zero. At this time, both rectifier switches in the lower bridge arm are in the linear amplification region and fail to turn off completely, resulting in a large micro-common current and thus excessive harmonic current. This invention utilizes the DRV signal of the PFC controller to adjust the conduction time of the rectifier switches, turning them off or lowering the drive voltage near the input zero-crossing point, thereby avoiding micro-common current and suppressing input harmonic current. Near the input voltage zero-crossing point, the duty cycle of the PFC controller's drive DRV is very large, while the duty cycle of the complementary signal generated by Q4 is very small, resulting in a relatively low voltage across C3. This allows the rectifier switches to remain off, reducing current distortion near the input voltage zero-crossing point and also reducing input harmonic current.

[0017] Figure 2 , Figure 3 , Figure 4 It is based on Figure 1 The circuit structure derived from the basic working principle, and its... Figure 1 The only difference is in the switching transistor rectifier bridge control circuit 102; the switching transistor rectifier bridge 101 and the PFC conversion circuit 103 are the same.

[0018] Figure 2 for Figure 1 A simplified version that only uses the PFC ON / OFF signal to control the switching transistor rectifier bridge 101 to turn on and off, but it does not have the function of automatically turning off the switching transistor rectifier bridge 101 near the zero point of the input voltage, and is prone to micro-commutation near the zero point of the input voltage. Figure 3 for Figure 1 The simplified version only uses the DRV drive signal of the PFC controller to control the switching transistor rectifier bridge 101 to turn on and off. When the PFC is working under light load, the pulse width of the DRV drive signal is small, which can easily lead to insufficient drive voltage of the switching transistor rectifier bridge 101, causing it to turn off prematurely when the PFC is under light load. Figure 4 This is another implementation proposed in this invention, which is related to... Figure 1 The basic implementation principle is the same. D8 and C3 sample the peak value of the drive voltage of PFC controller U1, which is used to power the switching rectifier bridge 101. D5, D6, R5, R6, DZ1, DZ2, and C5 divide and sample the input voltage signal. When the input voltage is higher than the preset voltage divider sampling voltage V1, Q3 is turned on, which turns on the switching rectifier bridge 101. When the input voltage is lower than the preset voltage divider sampling voltage V1, Q3 is turned off, Q4 is turned on, which pulls down the drive of the switching rectifier bridge 101 and turns off the switching rectifier bridge 101.

[0019] Compared with related technologies, the switching transistor rectifier bridge 101 and PFC circuit and its control method provided by the present invention have the following beneficial effects: This invention provides a switching transistor rectifier bridge 101 and a PFC circuit and its control method. The circuit structure is simple, stable and reliable. It uses the VCC power supply voltage of the PFC controller and the drive DVR signal to drive the switching transistor bridge. It takes advantage of the characteristic that the duty cycle of the DRV signal of the Boost PFC controller U1 changes proportionally with the input voltage, and adjusts the conduction time of the switching transistor bridge according to the magnitude of the input voltage. This makes the switching transistor rectifier bridge 101 in the off state near the zero crossing point of the input voltage, avoiding the occurrence of micro-commutation phenomenon, thereby reducing the distortion of the input current at the zero crossing point and reducing the input harmonic current.

[0020] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A switching transistor rectifier bridge and PFC circuit, characterized in that, include: Switching transistor rectifier bridge, switching transistor rectifier bridge control circuit and PFC conversion circuit; The switching rectifier bridge includes a first rectifier diode, a second rectifier diode, a first rectifier switch, and a second rectifier switch; The cathode of the first rectifier diode is connected to the cathode of the second rectifier diode; The anode of the first rectifier diode is connected to the drain of the first rectifier switch transistor; The gate of the first rectifier switch is connected to one end of the first resistor, and the source of the first rectifier switch is connected to the second rectifier switch and together they are connected to the primary ground. The gate of the second rectifier switch is connected to one end of the second resistor, and the drain of the second rectifier switch is connected to the anode of the second rectifier diode. The switching transistor rectifier bridge control circuit includes a first diode, a second diode, a first resistor, a second resistor, a third resistor, a third capacitor, a fourth switching transistor, and a fifth resistor. The anode of the first diode is connected to the gate of the first rectifier switch and one end of the first resistor, and the cathode of the first diode is connected to the drain of the second rectifier switch. The anode of the second diode is connected to the gate of the second rectifier switch and one end of the second resistor, and the cathode of the second diode is connected to the drain of the first rectifier switch. One end of the first resistor is connected to one end of the second resistor and the third capacitor; One end of the third capacitor is connected to the first resistor, the second resistor, the third resistor, and the fifth resistor, and the other end of the third capacitor is connected to the primary ground; One end of the third resistor is connected to the VCC pin of the PFC controller U1. One end of the fifth resistor is connected to the drain of the fourth switching transistor; The gate of the fourth switch is connected to the DRV drive pin of the PFC controller U1, and the source of the fourth switch is connected to the primary ground. The fourth switching transistor is a MOSFET or a bipolar transistor.

2. The switching transistor rectifier bridge and PFC circuit according to claim 1, characterized in that, The PFC conversion circuit includes a PFC controller U1, a first capacitor C1, a second capacitor C2, a first inductor L1, a fifth switching transistor Q5, a current sampling resistor Rcs, a seventh diode D7, and a PFC load. The PFC controller U1 is a Boost, Buck-boost, or flyback topology PFC controller. Its duty cycle is inversely proportional to the input voltage. The lower the input voltage, the larger the duty cycle, and the higher the input voltage, the smaller the duty cycle. The PFC Load is a resistive, inductive, or capacitive load, or a flyback, forward, AHB, or LLC resonant half-bridge DC-DC converter circuit load.

3. A control method for controlling the switching transistor rectifier bridge and PFC circuit as described in claim 1 or 2, characterized in that, Includes the following steps: During the S1 and T0~T1 periods, the PFC is in operation. During the positive half-wave AC cycle, the L-line voltage is greater than the N-line voltage. The input current flows from L through the first rectifier diode DB1, the first capacitor C1 or the first inductor L1, back to the second rectifier switch Q2, and then back to the N-line. The parasitic diodes at the DS terminals of the second rectifier switch Q2 are turned on. The N-line voltage is lower than the primary ground voltage, so the first diode D1 is turned on, pulling down the gate-source voltage Vgs1 of the first rectifier switch Q1, causing the first rectifier switch Q1 to be in the off state. The VCC and drive voltage DRV signals of the PFC controller U1 drive the second rectifier switch Q2 to turn on through the third resistor R3, the fifth resistor R5, the third capacitor C3, the fourth switch Q4, and the second resistor R2, reducing the losses in the rectification section. During periods S2 and T1~T2, the PFC is still in operation. During the negative half-wave of the AC circuit, the voltage of the N line is greater than that of the L line. The input current flows from the N line through the second rectifier diode DB2, the first capacitor C1 or the first inductor L1, back to the first rectifier switch Q1, and then back to the L line. The parasitic diodes at the DS terminals of the first rectifier switch Q1 are turned on. The voltage of the L line is lower than that of the primary ground. The second diode D2 is turned on, which lowers the gate-source voltage Vgs2 of the second rectifier switch Q2, causing the second rectifier switch Q2 to be in the off state. The VCC and drive voltage DRV signals of the PFC controller U1 drive the first rectifier switch Q1 to turn on through the third resistor R3, the fifth resistor R5, the third capacitor C3, the fourth switch Q4, and the first resistor R1, thereby reducing the losses in the rectification section. S3, T2~T3, and T3~T4 repeat the operations of time periods T0~T1 and T1~T2, respectively, which will not be repeated here; S4. When the first rectifier switch Q1 is turned on, it will pull down the gate-source voltage Vgs2 of the second rectifier switch Q2 through the second diode D2. When the second rectifier switch Q2 is turned on, it will pull down the gate-source voltage Vgs1 of the first rectifier switch Q1 through the first diode D1. This ensures that only one switch is fully turned on at the same time, preventing a short circuit between the L and N lines caused by the first rectifier switch Q1 and the second rectifier switch Q2 being fully turned on at the same time. During periods S5 and T4~T5, the output PFC load is disconnected, the output power decreases, the PFC stops working, the VCC voltage of the PFC controller U1 is pulled low, the drive voltages of the first rectifier switch Q1 and the second rectifier switch Q2 are also pulled low, and the rectifier bridge of the switching transistors also stops working. At this time, the parasitic diodes at the drain and source terminals of the first rectifier switch Q1 and the second rectifier switch Q2, together with the first rectifier diode DB1 and the second rectifier diode DB2, form a full-bridge rectifier circuit to complete the rectification of the input AC.

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