Totem pole PFC circuit control method and power conversion device

Abstract

The invention provides a totem pole PFC circuit control method and a power conversion device. The totem-pole PFC circuit comprises a first inductor, a first bridge arm and a second bridge arm, the first bridge arm and the second bridge arm are connected in parallel between the positive electrode and the negative electrode of the DC interface of the totem-pole PFC circuit, the first end of the first inductor is connected to the midpoint of the first bridge arm, and the second end of the first inductor and the midpoint of the second bridge arm are used for being connected with an AC power supply. The method comprises the following steps: controlling switch tubes of a first bridge arm and a second bridge arm to be closed within a first duration starting from a first moment before each zero-crossing moment of an alternating current power supply, and controlling a main switch tube of the first bridge arm to work within a second duration starting from a second moment after the zero-crossing moment, the follow current switch tubes of the second bridge arm and the first bridge arm are controlled to be closed; wherein the last moment of the first duration is the second moment. According to the control method provided by the invention, the leakage current of the power conversion device comprising the totem-pole PFC circuit can be effectively reduced.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method and power conversion device for a totem pole PFC circuit. Background Technology

[0002] With the development of the energy storage industry, various energy storage products are being used more and more widely. Some energy storage products employ a two-stage power conversion circuit. The front-end uses a totem-pole PFC circuit to achieve bidirectional power conversion, while the rear-end uses a transformer-equipped isolated DC / DC circuit to electrically isolate the low-voltage side, such as the energy storage battery. However, the low-frequency bridge arm midpoint of the totem-pole PFC circuit experiences pulsating voltage changes, which can generate leakage current on the primary and secondary sides of the rear-end transformer. Furthermore, to address electromagnetic interference (EMI) issues, Y capacitors are often added to the primary and secondary sides of the transformer to reduce common-mode noise at the AC port, further increasing the leakage current. Summary of the Invention

[0003] In view of this, this application provides a control method and power conversion device for a totem pole PFC circuit, which can effectively reduce leakage current.

[0004] This application provides a control method for a totem-pole PFC circuit. The totem-pole PFC circuit includes a first inductor, a first bridge arm, and a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the DC interface of the totem-pole PFC circuit. A first end of the first inductor is connected to the midpoint of the first bridge arm, and a second end of the first inductor and the midpoint of the second bridge arm are used to connect to an AC power supply. The method includes: controlling the switching transistors of the first bridge arm and the second bridge arm to remain off for a first duration starting from a first moment before each zero-crossing moment of the AC power supply; and controlling the main switching transistor of the first bridge arm to operate and controlling all switching transistors of the second bridge arm and the freewheeling switching transistor of the first bridge arm to remain off for a second duration starting from a second moment after the zero-crossing moment; wherein the last moment of the first duration is the second moment.

[0005] In one embodiment, controlling the main switch of the first bridge arm to operate during a second duration starting from a second time point after the zero-crossing moment includes: acquiring the bus voltage between the positive and negative terminals of the DC interface at the zero-crossing moment; determining a target duty cycle based on the bus voltage, the second duration, the inductance of the first inductor, and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm; and controlling the main switch of the first bridge arm to operate at the target duty cycle during the second duration.

[0006] In one embodiment, the lower switch of the second bridge arm is connected in parallel with the first capacitor; before determining the target duty cycle based on the bus voltage, the second duration, the inductance of the first inductor and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm, the method further includes: determining the capacitance value of the equivalent junction capacitance of the lower switch based on the capacitance value of the junction capacitance of the lower switch of the second bridge arm and the capacitance value of the first capacitor.

[0007] In one embodiment, the working cycle of the AC power supply includes a positive half-cycle and a negative half-cycle; during the second duration, the main switch of the first bridge arm is controlled to operate at a target duty cycle, including: when the zero-crossing point is when the AC power supply crosses zero from the negative half-cycle to the positive half-cycle, the lower switch of the first bridge arm is controlled to conduct at the target duty cycle during the second duration; when the zero-crossing point is when the AC power supply crosses zero from the positive half-cycle to the negative half-cycle, the upper switch of the first bridge arm is controlled to conduct at the target duty cycle during the second duration.

[0008] In one embodiment, before the switching transistors of the first bridge arm and the second bridge arm remain closed during a first time period starting from a first time before each zero-crossing moment of the AC power supply, the method further includes: determining the zero-crossing moment of the AC power supply.

[0009] In one embodiment, both the first duration and the second duration are greater than the sum of the turn-on delay time, turn-off delay time, turn-on rise time, and turn-off fall time of any switch in the first and second bridge arms.

[0010] In one embodiment, the method further includes: during the period from the end of each second time period to the next first time period, controlling the switching transistors on the first bridge arm and the second bridge arm to operate according to a preset control strategy.

[0011] A second aspect of this application provides a power conversion device, including a totem pole PFC circuit and a controller. The totem pole PFC circuit includes a first inductor, a first bridge arm, and a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the DC interface of the totem pole PFC circuit. The first end of the first inductor is connected to the midpoint of the first bridge arm. The second end of the first inductor and the midpoint of the second bridge arm are used to connect to an AC power source. The controller is used to execute the control method of the totem pole PFC circuit as described in any of the preceding claims.

[0012] In one embodiment, the power conversion device further includes a first capacitor, and the lower switching transistor of the second bridge arm is connected in parallel with the first capacitor.

[0013] In one embodiment, the power conversion device further includes an isolated DC / DC circuit, wherein the DC interface of the totem-pole PFC circuit is connected to the primary side of the isolated DC / DC circuit.

[0014] In summary, the control method for the totem pole PFC circuit provided in this application, on the one hand, periodically controls the switching transistors of the first and second bridge arms to remain off during a first duration including each zero-crossing moment, so as to reduce the probability of AC current zero-crossing distortion caused by the sudden change in the duty cycle of the switching transistors when the AC power supply crosses zero. On the other hand, during a second duration immediately following the first duration, the main switching transistor of the first bridge arm is controlled to work, and the freewheeling switching transistors of the second and first bridge arms are controlled to remain off, so that the equivalent junction capacitance voltage of the lower switching transistor changes slowly, thereby reducing leakage current by reducing the rate of voltage change. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation on the scope of protection of this application. In the various drawings, similar components are numbered similarly.

[0016] Figure 1 A circuit diagram of a power conversion circuit provided in an embodiment of this application.

[0017] Figure 2A for Figure 1 The diagram shows the first type of energy flow in the positive half-cycle of the AC power supply for the totem pole PFC circuit.

[0018] Figure 2B for Figure 1 The diagram shows the second type of energy flow in the positive half-cycle of the AC power supply for the totem pole PFC circuit.

[0019] Figure 2C for Figure 1 The diagram shows the first type of energy flow in the negative half-cycle of the AC power supply for the totem pole PFC circuit.

[0020] Figure 2D for Figure 1 The diagram shows the second type of energy flow in the negative half-cycle of the AC power supply for the totem pole PFC circuit.

[0021] Figure 3 for Figure 1 A schematic diagram of the equivalent current path of leakage current in a power conversion circuit.

[0022] Figure 4 This is a flowchart illustrating the control method of a totem pole PFC circuit provided in an embodiment of this application.

[0023] Figure 5 This is a timing diagram of each switch in a totem-pole PFC circuit during the transition from the negative half-cycle to the positive half-cycle of the AC power supply, as described in one embodiment of this application.

[0024] Figure 6 This is a flowchart illustrating a sub-step of step S402 in one embodiment of this application.

[0025] Figure 7 This is a circuit diagram of a totem pole PFC circuit in another embodiment of this application.

[0026] Figure 8A This is a schematic diagram of the equivalent junction capacitance voltage of the switch Q4, the output voltage of the AC power supply, and the waveform of the PWM signal controlling the switch Q2 obtained by executing the control method of the totem pole PFC circuit provided in this application when the AC power supply changes from the negative half-cycle to the positive half-cycle.

[0027] Figure 8B This is a schematic diagram of the equivalent junction capacitance voltage of switch Q4, the output voltage of the AC power supply, and the waveform of the PWM signal controlling switch Q2, obtained by keeping switch Q2 off for a second duration when the AC power supply is from the negative half-cycle to the positive half-cycle, according to one embodiment of this application.

[0028] Figure 9 This is a schematic diagram of a power conversion device provided in an embodiment of this application.

[0029] Figure 10 A functional block diagram of a computer-readable storage medium provided in an embodiment of this application. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0031] It should be noted that when a component is considered to be "connected" to another component, it can be directly connected to the other component or may also have an intervening component. When a component is considered to be "placed" on another component, it can be directly placed on the other component or may also have an intervening component. The terms "top," "bottom," "upper," "lower," "left," "right," "front," "back," and similar expressions used in this article are for illustrative purposes only.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0033] Some embodiments will now be described with reference to the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0034] With the development of the energy storage industry, various energy storage products are being used more and more widely. Some energy storage products use a two-stage power conversion circuit. The front stage of the power conversion circuit uses a totem-pole PFC circuit to achieve bidirectional power conversion, while the rear stage uses an isolated DC / DC circuit with a transformer to provide electrical isolation for the low-voltage side, such as the energy storage battery.

[0035] For example, please see Figure 1 , Figure 1 This is a schematic diagram of a power conversion circuit 10 provided in this application. The power conversion circuit 10 includes a totem pole PFC circuit 110 and an isolated DC / DC circuit 120.

[0036] The totem-pole PFC circuit 110 includes a first inductor L1, a first bridge arm 111, and a second bridge arm 112. The first bridge arm 111 and the second bridge arm 112 are connected in parallel between the positive and negative terminals of the DC interface of the totem-pole PFC circuit 110, specifically between the positive terminal OUT+ and the negative terminal OUT-. The first end of the first inductor L1 is connected to the midpoint of the first bridge arm 111, and the second end of the first inductor L1 and the midpoint of the second bridge arm 112 are used to connect to the AC power supply. A capacitor C1 is also connected between the positive terminal OUT+ and the negative terminal OUT- of the DC interface of the totem-pole PFC circuit 110, and the negative terminal OUT- is also connected to the ground point BUS_GND.

[0037] Each bridge arm in the totem pole PFC circuit 110 includes an upper switch and a lower switch connected in series. The connection node between the upper and lower switches is the midpoint of the corresponding bridge arm. For example, the first bridge arm 111 includes an upper switch (i.e., switch Q1) and a lower switch (i.e., switch Q2), and the second bridge arm 112 includes an upper switch (i.e., switch Q3) and a lower switch (i.e., switch Q4). The first terminals of switches Q1 and Q3 are both connected to the positive terminal OUT+ of the DC interface. The second terminal of switch Q1 is connected to the first terminal of switch Q2 (this connection node is the midpoint A of the first bridge arm 111), the second terminal of switch Q3 is connected to the first terminal of switch Q4 (this connection node is the midpoint B of the second bridge arm 112), and the second terminals of switches Q2 and Q4 are both connected to the negative terminal OUT- of the DC interface. The controlled terminals of switches Q1 to Q4 are all connected to the controller of the totem pole PFC circuit 110. Figure 1 (Not shown) Connection. By controlling the switching transistors Q1 to Q4 to turn on and off through the controller, and in conjunction with the first inductor L1, the bidirectional power conversion of the totem pole PFC circuit 110 can be realized.

[0038] Specifically, the first bridge arm 111 of the totem pole PFC circuit 110 is also known as the high-frequency bridge arm, and the second bridge arm 112 is also known as the low-frequency bridge arm. The working principle of the totem pole PFC circuit 110 is as follows:

[0039] Please refer to the following: Figure 2A and Figure 2B In the totem-pole PFC circuit 110, when the AC power supply is in the positive half-cycle, switch Q2 in the first bridge arm 111 acts as the main switch, switch Q1 acts as the freewheeling switch, and switch Q4 in the second bridge arm 112 is always on. Specifically, when switch Q2 is on, the AC power supply is based on... Figure 2A The illustrated energy path stores energy in the first inductor L1, and the voltage across capacitor C1 is used to maintain the current at the DC interface. When switch Q1 is turned on, based on... Figure 2B The energy path shown is such that the electrical energy output from the AC power supply and the energy in the first inductor L1 together maintain the current of the DC interface.

[0040] Please refer to the following: Figure 2C and Figure 2D In the totem-pole PFC circuit 110, when the AC power supply is in the negative half-cycle, switch Q1 in the first bridge arm 111 acts as the main switch, switch Q2 acts as the freewheeling switch, and switch Q3 in the second bridge arm 112 is always on. Specifically, when switch Q1 is on, the AC power supply is based on... Figure 2C The illustrated energy path stores energy in the first inductor L1, and capacitor C1 is used to maintain the current at the DC interface. When switch Q2 is turned on, based on... Figure 2D The energy path shown is such that the electrical energy output from the AC power supply and the energy in the first inductor L1 together maintain the current of the DC interface.

[0041] In this way, the totem pole PFC circuit 110 can achieve bidirectional power conversion between AC power supply and DC interface.

[0042] It should be noted that, in this application, "switch off" means that the switch remains in an open state, i.e., the controller does not send a drive signal to the switch. "Switch on" means that the controller continuously sends a drive signal to the switch, and the switch periodically or intermittently turns on or off under the drive signal.

[0043] Please refer to it again. Figure 1The isolated DC / DC circuit 120 includes a primary circuit 121, a second inductor L2, a capacitor C2, a transformer T1, and a secondary circuit 122. In one embodiment, the primary circuit 121 includes switches Q5 to Q8, and the secondary circuit 122 includes switches Q9 to Q12. The switches in the primary circuit 121 and the secondary circuit 122 respectively form a full-bridge circuit. Specifically, in the primary circuit 121, the first terminals of switches Q5 and Q7 are both connected to the positive terminal OUT+ of the DC interface, the second terminal of switch Q5 is connected to the first terminal of switch Q6 (this connection node is the midpoint a between switches Q5 and Q6), the second terminal of switch Q7 is connected to the first terminal of switch Q8 (this connection node is the midpoint b between switches Q7 and Q8), and the second terminals of switches Q6 and Q8 are both connected to the negative terminal OUT- of the DC interface. In the secondary circuit 122, the first terminals of both switching transistors Q9 and Q11 are connected to the positive terminal BAT+ of the power interface. The second terminal of switching transistor Q9 is connected to the first terminal of switching transistor Q10 (this connection point is the midpoint c between switching transistors Q9 and Q10). The second terminal of switching transistor Q11 is connected to the first terminal of switching transistor Q12 (this connection point is the midpoint d between switching transistors Q11 and Q12). The second terminals of both switching transistors Q10 and Q12 are connected to the negative terminal BAT- of the power interface. The positive and negative terminals BAT+ and BAT- of the power interface are used to connect to a DC power source, such as a battery pack.

[0044] Furthermore, the first terminal of the second inductor L2 is connected to the midpoint a, the second terminal of the second inductor L2 is connected to one end of the primary winding of transformer T1, the other end of the primary winding of transformer T1 is connected to the first terminal of capacitor C2, and the second terminal of capacitor C2 is connected to the midpoint b. One end of the secondary winding of transformer T1 is connected to the midpoint c, and the other end of the secondary winding of transformer T1 is connected to the midpoint d.

[0045] The controlled terminals of switching transistors Q5 to Q12 are all connected to the controller of the isolated DC / DC circuit 120. Figure 1 (Not shown) Connection. The isolated DC / DC circuit 120 controls the switching transistors Q5 to Q12 to turn on and off, enabling power conversion between the DC interface and the battery pack. Thus, the power conversion circuit 10, including the totem-pole PFC circuit 110 and the isolated DC / DC circuit 120, can achieve bidirectional power conversion between AC power and the battery pack.

[0046] Understandably, the aforementioned switching transistors Q1 to Q12 can be MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), BJTs (Bipolar Junction Transistors), or IGBTs (Insulated Gate Bipolar Transistors). This application does not limit this. For example, in one embodiment, switching transistors Q1 to Q4 can be NPN BJTs, and the first terminals of switching transistors Q1 to Q4 are all collectors; the second terminals of switching transistors Q1 to Q4 are all emitters; the controlled terminals of switching transistors Q1 to Q4 are all bases; switching transistors Q5 to Q12 can be NMOS transistors, and the first terminals of switching transistors Q5 to Q12 are all drains; the second terminals of switching transistors Q5 to Q12 are all sources; the controlled terminals of switching transistors Q5 to Q12 are all gates.

[0047] However, since the neutral line N of the AC power supply is connected to the midpoint B of the second bridge arm 112, the voltage of the neutral line N is the same as the voltage at the junction BUS_GND of the second bridge arm midpoint B. Since the low-frequency bridge arm midpoint (i.e., the second bridge arm midpoint B) of the totem-pole PFC circuit 110 has a pulsating voltage change at the junction BUS_GND, this will generate leakage current on the primary and secondary sides of the subsequent transformer T1. Furthermore, to address the system's electromagnetic interference (EMI) problem, Y capacitors are often added to the primary and secondary sides of transformer T1 to reduce common-mode noise at the AC port, which will further increase the leakage current.

[0048] For example, please see Figure 3 , Figure 3 In the diagram, capacitor C3 represents the equivalent parasitic capacitance of the primary and secondary sides of transformer T1, and capacitor C4 represents the Y capacitance connected between the primary and secondary sides. For example... Figure 3 As shown, the voltage waveform at the neutral line N connected to the BUS_GND point is a trapezoidal wave with a power frequency cycle. Therefore, the changing voltage at the midpoint B of the second bridge arm 112 can charge and discharge capacitors C3 and C4, causing leakage current in the power conversion circuit 10. The leakage current path is as follows... Figure 3 As shown by the dashed line.

[0049] Therefore, it is necessary to provide a control method and power conversion device for a totem pole PFC circuit to reduce leakage current.

[0050] Please refer to the following: Figure 1 and Figure 4 , Figure 4This is a schematic flowchart illustrating a control method for a totem pole PFC circuit provided in one embodiment of this application. It can be understood that... Figure 4 The steps shown can be controlled by the controller of the totem pole PFC circuit 110. Figure 1 (Not shown) is executed. The control method for this totem pole PFC circuit includes the following steps:

[0051] Step S401: During the first duration starting from the first moment before each zero-crossing point of the AC power supply, the switching transistors controlling the first and second bridge arms remain closed, and

[0052] Step S402: During the second duration starting from the second moment after the zero point, control the main switch of the first bridge arm to work, and control all switches of the second bridge arm and the freewheeling switch of the first bridge arm to remain closed, wherein the last moment of the first duration is the second moment.

[0053] Please refer to the following: Figure 5 ,by Figure 5 Taking the schematic diagram of the drive signals of each switch on the totem-pole PFC circuit 110 when the AC power supply crosses zero from the negative half-cycle to the positive half-cycle as an example, since the first moment m1 occurs before the zero-crossing moment P0, and the second moment m2 occurs after the zero-crossing moment P0, and the first moment m1 is the start moment of the first duration T1, and the second moment m2 is the last moment of the first duration T1, it indicates that the zero-crossing moment P0 of the AC power supply occurs within the first duration T1. Thus, in step S401, by controlling the switches of the first bridge arm 111 and the second bridge arm 112 to remain closed within the first duration T1, the probability of AC current zero-crossing distortion caused by the sudden change in the duty cycle of the switches can be reduced when the AC power supply crosses zero. Understandably, the above inference also applies to the case when the AC power supply crosses zero from the positive half-cycle to the negative half-cycle, which will not be elaborated here.

[0054] In step S402, the main switch of the first bridge arm 111 is controlled to operate, that is, the main switch of the first bridge arm 111 is controlled to conduct periodically. For ease of explanation, the following description of the working principle uses the example that the parameters of switch Q3 and switch Q4 are the same, that is, the equivalent junction capacitance between the first and second terminals of switch Q3 is equal to the equivalent junction capacitance between the first and second terminals of switch Q4. In other embodiments, the equivalent junction capacitance between the first and second terminals of switch Q3 and switch Q4 may not be equal.

[0055] Understandably, since the switches on the first bridge arm 111 and the second bridge arm 112 are both kept off during the first time period, when the parameters of the switches Q3 and Q4 are the same, the equivalent junction capacitance voltages of the switches Q3 and Q4 are equally divided between the bus voltages of the DC interfaces OUT+ / OUT-, that is, the equivalent junction capacitance voltages of the switches Q3 and Q4 are both half of the bus voltage.

[0056] Please refer to the following: Figure 1 and Figure 5 Let's take the example of AC power supply crossing from the negative half-cycle to the positive half-cycle. After the first duration T1 ends, when the main switch (Q2) of the first bridge arm 111 is turned on, the first inductor L1 is energized through the equivalent junction capacitance of the switch Q2 of the first bridge arm 111 and the lower switch Q4 of the second bridge arm 112. When the main switch Q2 of the first bridge arm 111 is turned off, it is demagnetized through the body diode on the freewheeling switch (Q1) of the first bridge arm 111 and the equivalent junction capacitance of the upper switch Q3 of the second bridge arm 112. Thus, through the multiple turns of the main switch Q2 of the first bridge arm 111, the equivalent junction capacitance of switch Q4 discharges, causing the equivalent junction capacitance voltage of switch Q4 to slowly decrease from half the bus voltage to zero, while the equivalent junction capacitance of switch Q3 charges, causing the equivalent junction capacitance voltage of switch Q3 to slowly increase from half the bus voltage to the bus voltage.

[0057] Correspondingly, when the AC power supply crosses zero from the positive half-cycle to the negative half-cycle, when the main switch (i.e., switch Q1) of the first bridge arm 111 is turned on, the first inductor L1 can be energized through the equivalent junction capacitance of switch Q1 of the first bridge arm 111 and the upper switch Q3 of the second bridge arm 112; when the main switch of the first bridge arm 111 is turned off, it can be demagnetized through the body diode on the freewheeling switch (i.e., switch Q2) of the first bridge arm 111 and the equivalent junction capacitance of the lower switch Q4 of the second bridge arm 112. Thus, through the multiple turns on of the main switch Q1 of the first bridge arm 111, the equivalent junction capacitance of switch Q3 discharges, causing the equivalent junction capacitance voltage of switch Q3 to slowly decrease from half the bus voltage to zero, while the equivalent junction capacitance of switch Q4 charges, causing the equivalent junction capacitance voltage of switch Q4 to rise from half the bus voltage to the bus voltage.

[0058] In this way, each time the AC power supply crosses zero, the multiple conductions of the main switch in the first bridge arm 111 allow the equivalent junction capacitance voltage of switch Q4 to change slowly, compared to when the main switch in the first bridge arm 111 is not controlled to operate within the second time period. Since the equivalent junction capacitance voltage of switch Q4 (i.e., the midpoint B voltage) is the voltage between the neutral line N and the ground point BUS_GND, the equivalent junction capacitance of switch Q4 is related to capacitors C3 and C4 (see reference). Figure 3 Leakage current is generated during charging and discharging, and this leakage current can be calculated using the formula I = C·dV / dt, where I is the leakage current, C is the capacitance value, and dV / dt is the voltage change rate. That is, the magnitude of the leakage current is positively correlated with the voltage change rate. Thus, by executing step S402, the equivalent junction capacitance voltage of the switching transistor Q4 changes slowly, thereby reducing the leakage current by decreasing the voltage change rate.

[0059] In summary, the control method of the totem pole PFC circuit provided in this application, on the one hand, periodically controls the switching transistors of the first bridge arm 111 and the second bridge arm 112 to remain off during a first duration including each zero-crossing moment, so as to reduce the probability of AC current zero-crossing distortion caused by the sudden change in the duty cycle of the switching transistors when the AC power supply crosses zero. On the other hand, during a second duration immediately following the first duration, the main switching transistor of the first bridge arm 111 is controlled to work, and the freewheeling switching transistors of the second bridge arm 112 and the first bridge arm 111 are controlled to remain off, so that the equivalent junction capacitance voltage of the switching transistor Q4 changes slowly, thereby reducing leakage current by reducing the rate of voltage change.

[0060] Please refer to the following: Figure 1 and Figure 6 In some embodiments, step S402 includes the following sub-steps:

[0061] Step S601: Obtain the bus voltage between the positive and negative terminals of the DC interface at the zero-crossing point.

[0062] In some embodiments, the DC interface of the totem pole PFC circuit 110 is equipped with a voltage sensor or other hardware or circuit with voltage detection function. Thus, in step S601, the voltage sample value across capacitor C1 at the zero-crossing point can be obtained by the voltage sensor or other voltage detection circuit as the bus voltage at the zero-crossing point.

[0063] Step S602: Determine the target duty cycle based on the bus voltage, the second duration, the inductance of the first inductor, and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm.

[0064] The equivalent junction capacitance of the lower switch of the second bridge arm 112 can be the equivalent junction capacitance between the first and second terminals of the switch Q4. The target duty cycle is used to represent the duty cycle during which the main switch driving the first bridge arm 111 is periodically turned on within the second time period.

[0065] In some embodiments, the target duty cycle can be calculated based on the voltage calculation formula across the first inductor L1 and the equivalent junction capacitance charge calculation formula of the switch Q4, according to the bus voltage, the second duration, the inductance of the first inductor, and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm.

[0066] For example, the conduction duration of the main switch tube of the first bridge arm 111 in each working cycle during the second time period can be calculated based on the following formulas (1) and (2), and then the target duty cycle can be calculated based on the conduction duration.

[0067] (Vac-Vbus / 2)×Ton=L×ΔIl (1)

[0068] (T2×fs)×(ΔIl / 2)×Ton=Cq×Vbus / 2 (2)

[0069] Where Vac represents the output voltage of the AC power supply; Vbus represents the bus voltage; Ton represents the conduction duration of the main switch of the first bridge arm 111 in each operating cycle within the second time period; L represents the inductance of the first inductor L1; ΔIl represents the current change of the first inductor L1 within the conduction duration Ton; T2 represents the second time period; fs represents the switching frequency of the main switch of the first bridge arm 111; ΔIl / 2 represents the average current of the first inductor L1 within the conduction duration Ton; and Cq represents the equivalent junction capacitance of the switch Q4.

[0070] In some embodiments, the second duration can be, for example, 200 microseconds, the switching frequency fs can be, for example, 20kHz, the equivalent junction capacitance Cq of the switching transistor Q4 can be, for example, 10nF, and the bus voltage can be, for example, 400V. Since the second duration is close to the zero-crossing point of the AC power supply, the output voltage Vac is equal to 0 at this time, and the conduction duration Ton can be calculated to be 1 microsecond. It is understood that this application does not limit the specific values ​​involved in the above formulas (1) and (2), and the corresponding conduction duration can be calculated based on other values ​​in other embodiments.

[0071] Thus, based on the above formulas (1) and (2), the conduction duration Ton of the main switch of the first bridge arm 111 in each working cycle can be calculated according to the bus voltage, the second duration, the inductance of the first inductor, the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm, and the switching frequency. Then, the target duty cycle can be calculated by multiplying the conduction duration Ton by the switching frequency fs.

[0072] Understandably, the second duration, the inductance of the first inductor L1, and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm can be pre-stored in the memory of the totem-pole PFC circuit 110. Figure 1 The data (not shown) can also be data obtained from a host computer. This application does not limit the method of obtaining the second duration, the inductance of the first inductor L1, and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm.

[0073] In other embodiments, in order to further improve the calculation accuracy, the target duty cycle can also be calculated based on the calculation coefficients and the above formulas (1) and (2). This application does not limit the specific calculation formula for calculating the target duty cycle in step S602.

[0074] Step S603: Control the main switch of the first bridge arm to operate at the target duty cycle during the second time period.

[0075] In step S603, a drive signal can be generated according to the target duty cycle, so that the main switch of the first bridge arm 111 can be periodically turned on according to the drive signal during the second time period, so that the voltage of the midpoint B of the second bridge arm 112 changes slowly during the second time period, thereby reducing the leakage current.

[0076] In some embodiments, the drive signal may be a PWM (Pulse Width Modulation) signal.

[0077] Thus, by executing steps S601 to S603, effective control of the lower switch of the second bridge arm 112, i.e., the switch Q4, can be achieved within the second time period, so that the equivalent junction capacitance voltage of the switch Q4 changes slowly.

[0078] Please continue reading. Figure 7 In some embodiments, the lower switch of the second bridge arm 112, i.e., switch Q4, is connected in parallel with the first capacitor Cq1, and the upper switch of the second bridge arm 112, i.e., switch Q3, is connected in parallel with the second capacitor Cq2. Thus, before performing step S602, the method further includes: determining the equivalent junction capacitance value of the lower switch based on the junction capacitance value of the lower switch of the second bridge arm and the capacitance value of the first capacitor.

[0079] For example, in some embodiments, the sum of the junction capacitance of the switch Q4 and the capacitance Cq1 of the first capacitor can be calculated as the equivalent junction capacitance of the lower switch. The junction capacitance of the switch Q4 can be obtained from the switch Q4's datasheet or measured using a measurement circuit.

[0080] In other embodiments, the equivalent junction capacitance of the lower switching transistor can also be calculated based on other calculation parameters, according to the sum of the junction capacitance of the switching transistor Q4 and the capacitance Cq1 of the first capacitor. This application does not limit the specific calculation formula for determining the equivalent junction capacitance of the lower switching transistor based on the junction capacitance of the lower switching transistor in the second bridge arm and the capacitance of the first capacitor.

[0081] In some embodiments, the capacitance values ​​of the first capacitor Cq1 and the second capacitor Cq2 are equal, for example, both being 10 nF (nanofa). In other embodiments, the capacitance values ​​of the first capacitor Cq1 and the second capacitor Cq2 may be different, and this application does not limit the specific capacitance values ​​of the first capacitor Cq1 and the second capacitor Cq2.

[0082] In this embodiment, by connecting the first capacitor Cq1 in parallel with the switch Q4, the equivalent junction capacitance of the switch Q4 can be increased by the first capacitor Cq1 when the junction capacitance of the switch Q4 is too small to meet the charging and discharging conditions. This is in conjunction with the control method of the totem pole PFC circuit provided in this application to reduce the voltage change rate of the switch Q4, thereby reducing leakage current.

[0083] Understandably, the duty cycle of an AC power supply includes a positive half-cycle and a negative half-cycle; correspondingly, step S402 includes:

[0084] When the zero-crossing point is when the AC power supply crosses zero from the negative half-cycle to the positive half-cycle, the lower switch of the first bridge arm is controlled to conduct according to the target duty cycle during the second time period.

[0085] When the zero-crossing point is when the AC power supply crosses zero from the positive half-cycle to the negative half-cycle, the upper switch of the first bridge arm is controlled to conduct according to the target duty cycle during the second time period.

[0086] Thus, this embodiment can reduce the rate of change of the equivalent junction capacitance voltage of the switching transistor Q4 at each zero-crossing point of the AC power supply, thereby reducing leakage current.

[0087] In some embodiments, before performing step S401, the method further includes: determining the zero-crossing time of the AC power supply.

[0088] The zero-crossing point of the AC power supply can be determined by detecting the output voltage or output current between the live wire (L) and the neutral wire (N) of the AC power supply. The zero-crossing point includes the zero-crossing point between the negative half-cycle and the positive half-cycle, and the zero-crossing point between the positive half-cycle and the negative half-cycle.

[0089] In some embodiments, the zero-crossing time can be determined by comparing the sampled output current with a reference current (e.g., zero-point current) and based on the direction of the output current change, or by using existing zero-point detection circuits or sensors. This application does not limit the specific method for determining the zero-crossing time based on the output voltage or output current.

[0090] Understandably, since the AC power supply changes periodically, the zero-crossing time of the AC power supply in the next cycle can be predicted based on the currently detected zero-crossing time.

[0091] In some embodiments, the first duration can be a preset value, such as 200 microseconds or 300 microseconds. This application does not limit the specific value of the first duration. Thus, based on the first duration and the determined zero-crossing time, the corresponding first moment and second moment can be determined.

[0092] In some embodiments, the duration from the first time point to the zero-crossing time point is equal to the duration from the zero-crossing time point to the second time point. This application does not limit the position of the zero-crossing time point within the first duration. For example, in other embodiments, the duration from the first time point to the zero-crossing time point may be greater than or less than the duration from the zero-crossing time point to the second time point.

[0093] In some embodiments, both the first duration and the second duration are greater than the sum of the turn-on delay time, turn-off delay time, turn-on rise time, and turn-off fall time of any switch in the first bridge arm 111 and the second bridge arm 112. This ensures that the switches involved in steps S401 and S402 have sufficient time to fully transition from the off state to the on state, and from the on state to the off state. This helps avoid partial turn-on or incomplete turn-off, thereby reducing switching losses and electromagnetic interference (EMI), and ensuring the effectiveness of the totem-pole PFC circuit control method.

[0094] In some embodiments, the method further includes:

[0095] During the period from the end of each second time period to the next first time period, the switching transistors on the first and second bridge arms are controlled according to the preset control strategy.

[0096] Please refer to the following: Figures 2A-2D and Figure 5 The preset control strategy may include: when the AC power supply is in the positive half-cycle, the switch Q2 in the first bridge arm 111 acts as the main switch, the switch Q1 acts as the freewheeling switch, and the switch Q1 and switch Q2 conduct complementaryly, while the switch Q4 in the second bridge arm 112 is always on; when the AC power supply is in the negative half-cycle, the switch Q1 in the first bridge arm 111 acts as the main switch, the switch Q2 acts as the freewheeling switch, and the switch Q1 and switch Q2 conduct complementaryly, while the switch Q3 in the second bridge arm 112 is always on.

[0097] Please continue reading. Figure 8A and Figure 8B , Figure 8A From top to bottom, the figures are: the equivalent junction capacitance voltage of the switching transistor Q4, the output voltage of the AC power supply (from the negative half-cycle to the positive half-cycle), and the waveform diagram of the PWM signal controlling the switching transistor Q2, obtained by implementing the control method of the totem pole PFC circuit provided in this application. Figure 8BThe diagram, from top to bottom, shows: the equivalent junction capacitance voltage of switch Q4 obtained by keeping switch Q2 off for the second time period when the AC power supply transitions from the negative half-cycle to the positive half-cycle; the output voltage of the AC power supply; and the waveform of the PWM signal controlling switch Q2. Figure 8A and Figure 8B The comparison shows that, due to Figure 8A The control method of the totem-pole PFC circuit provided in this application causes the switching transistor Q2 to operate earlier, thereby slowing down the voltage change trend of the equivalent junction capacitance voltage of the switching transistor Q4, and reducing the voltage change rate from... Figure 8B Reducing the leakage current from 100V / µS to 1V / µS (volts per microsecond) is obviously beneficial for reducing leakage current.

[0098] Please see Figure 9 This application also provides a power conversion device 100, including a totem-pole PFC circuit 110 and a controller 130. The totem-pole PFC circuit 110 includes a first inductor L1, a first bridge arm 111, and a second bridge arm 112. The first bridge arm 111 and the second bridge arm 112 are connected in parallel between the positive and negative terminals of the DC interface of the totem-pole PFC circuit 110. The first end of the first inductor L1 is connected to the midpoint A of the first bridge arm 111, and the second end of the first inductor L1 and the midpoint B of the second bridge arm 112 are used to connect to an AC power source. The controller 130 is used to execute the control method of the totem-pole PFC circuit as described in any of the above embodiments.

[0099] In some embodiments, the power conversion device 100 further includes a first capacitor Cq1. The lower switch of the second bridge arm 112, i.e., switch Q4, is connected in parallel with the first capacitor Cq1. This increases the equivalent junction capacitance of switch Q4, which, in conjunction with the control method of the totem-pole PFC circuit provided in this application, reduces the voltage change rate of switch Q4, thereby reducing leakage current.

[0100] In some embodiments, the power conversion device 100 further includes an isolated DC / DC circuit 120, and the DC interface of the totem-pole PFC circuit 110 is connected to the primary side of the isolated DC / DC circuit 120. For specific connection details, please refer to [link to specific connection methods]. Figure 1 The relevant descriptions will not be repeated here.

[0101] Understandably, the power conversion device 100 provided in this application can be a standalone electronic device or integrated into an energy storage device or other electronic device. This application does not limit the specific form of the power conversion device 100.

[0102] Please see Figure 10This application also provides a computer-readable storage medium 200 storing a computer program 210 thereon. When executed by a processor, the computer program 210 implements the control method of the totem-pole PFC circuit as described in the above technical solutions. The computer-readable storage medium 200 may be a portable compact disc read-only memory (CD-ROM) and include program code, and may run on a terminal device, such as a personal computer. However, the program product of this invention is not limited thereto. In this document, the readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

[0103] The above-described program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: electrical connections having one or more wires, portable disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0104] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium, capable of sending, propagating, or transmitting programs for use by or in conjunction with an instruction execution system, apparatus, or device.

[0105] The program code contained on the readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, RF, etc., or any suitable combination thereof.

[0106] Program code for performing the operations of this invention can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0107] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0108] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for a totem pole PFC circuit, characterized in that, The totem pole PFC circuit includes a first inductor, a first bridge arm, and a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the DC interface of the totem pole PFC circuit. A first end of the first inductor is connected to the midpoint of the first bridge arm, and a second end of the first inductor and the midpoint of the second bridge arm are used to connect to an AC power source. The method includes: During a first duration beginning at a first moment before each zero-crossing point of the AC power supply, the switching transistors controlling the first and second bridge arms remain closed, and During the second duration starting from the second moment after the zero crossing time, the main switch of the first bridge arm is controlled to operate, and all switches of the second bridge arm and the freewheeling switch of the first bridge arm are controlled to remain closed. The last moment of the first duration is the second moment.

2. The method according to claim 1, characterized in that, During the second duration starting from the second moment after the zero-crossing time, controlling the main switch of the first bridge arm to operate includes: Obtain the bus voltage between the positive and negative terminals of the DC interface at the zero-crossing point; The target duty cycle is determined based on the bus voltage, the second duration, the inductance of the first inductor, and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm. During the second duration, the main switch of the first bridge arm is controlled to operate at the target duty cycle.

3. The method according to claim 2, characterized in that, The lower switch of the second bridge arm is connected in parallel with the first capacitor; Before determining the target duty cycle based on the bus voltage, the second duration, the inductance of the first inductor, and the capacitance value of the equivalent junction capacitance of the lower switch of the second bridge arm, the method further includes: The equivalent junction capacitance of the lower switch is determined based on the capacitance value of the lower switch junction capacitance of the second bridge arm and the capacitance value of the first capacitor.

4. The method according to claim 2, characterized in that, The working cycle of the AC power supply includes a positive half-cycle and a negative half-cycle. The step of operating the main switch of the first bridge arm at the target duty cycle during the second time period includes: When the zero-crossing point is when the AC power supply crosses zero from the negative half-cycle to the positive half-cycle, the lower switch of the first bridge arm is controlled to conduct according to the target duty cycle within the second duration. When the zero-crossing point is when the AC power supply crosses zero from the positive half-cycle to the negative half-cycle, the upper switch of the first bridge arm is controlled to conduct according to the target duty cycle within the second duration.

5. The method according to claim 1, characterized in that, Within a first duration beginning at a first moment before each zero-crossing point of the AC power supply, before keeping the switching transistors of the first and second bridge arms closed, the method further includes: Determine the zero-crossing time of the AC power supply.

6. The method according to claim 1, characterized in that, Both the first duration and the second duration are greater than the sum of the turn-on delay time, turn-off delay time, turn-on rise time, and turn-off fall time of any switching transistor in the first bridge arm and the second bridge arm.

7. The method according to claim 1, characterized in that, The method further includes: During the period from the end of each second time period to the next first time period, the switching transistors on the first bridge arm and the second bridge arm are controlled to operate according to a preset control strategy.

8. A power conversion device, the power conversion device comprising a totem-pole PFC circuit and a controller, characterized in that, The totem pole PFC circuit includes a first inductor, a first bridge arm, and a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel between the positive and negative terminals of the DC interface of the totem pole PFC circuit. The first end of the first inductor is connected to the midpoint of the first bridge arm. The second end of the first inductor and the midpoint of the second bridge arm are used to connect to an AC power source. The controller is used to execute the control method of the totem pole PFC circuit as described in any one of claims 1 to 7.

9. The power conversion device according to claim 8, characterized in that, The power conversion device further includes a first capacitor, and the lower switching transistor of the second bridge arm is connected in parallel with the first capacitor.

10. The power conversion device as described in claim 8, characterized in that, The power conversion device also includes an isolated DC / DC circuit, and the DC interface of the totem pole PFC circuit is connected to the primary side of the isolated DC / DC circuit.

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