A control method and device of a totem pole PFC circuit and electronic equipment

Abstract

A control method of totem-pole PFC circuit, if the last switching period is less than the set time, the AC power of the input end of the totem-pole PFC circuit is in the positive half cycle, and the PFC inductor charging is completed, the switching of the PFC inductor discharging is delayed for a set threshold time, and then the switching of the PFC inductor discharging is turned on, so that the switching of the PFC inductor discharging is turned on only once. In the existing PFC application, when the input voltage is in the positive half cycle, the switching of the PFC inductor discharging needs to be turned on twice. Compared with the existing PFC circuit, the switching of the PFC inductor discharging is turned on only once, so that the power consumption of the self-boosting capacitor connected to the gate of the switching S1 in the self-boosting circuit is reduced. The self-boosting capacitor does not need to increase the volume, not only reduces the cost of the circuit, but also facilitates the miniaturization of the equipment with the totem-pole PFC circuit.

Description

Technical Field

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

[0002] Power factor refers to the relationship between effective power and total power consumption (apparent power), which is the ratio of effective power to total power consumption. It is one of the important indicators for evaluating the performance of power-consuming equipment such as components and electronic devices. Therefore, the value of power factor can be used to determine the degree to which the power of power-consuming equipment is effectively utilized. The higher the value of power factor, the higher the power utilization rate and the better the performance of the power-consuming equipment.

[0003] Power factor correction (PFC) is a common technology in the power supply field. Existing PFC circuits suffer from low efficiency, low switching frequency, and large size of magnetic components. To address these issues, totem-pole PFC circuits have been proposed to solve these problems. However, in a totem-pole PFC circuit, the switch needs to be turned on multiple times within a single switching cycle. Each time the switch is turned on, it consumes the charge of the bootstrap capacitor in the bootstrap circuit. If the switch is turned on multiple times, the bootstrap capacitor needs a large capacitance value to ensure the normal operation of the totem-pole PFC circuit. Increasing the capacitance value of the bootstrap capacitor not only increases the circuit cost but also results in a larger capacitor size, which is detrimental to the miniaturization of devices incorporating totem-pole PFC circuits. Summary of the Invention

[0004] To address the aforementioned issues, embodiments of this application provide a control method, apparatus, and electronic device for a totem-pole PFC circuit. When the AC input of the totem-pole PFC circuit is in the positive half-cycle, if the previous switching cycle is less than a set time, after the PFC inductor is fully charged, the switch for discharging the PFC inductor is delayed by a set threshold time before being turned on, thus enabling the PFC inductor to conduct only once. In existing PFC applications, when the input voltage is in the positive half-cycle, the switch for discharging the PFC inductor needs to be turned on twice. Compared to existing PFC circuits, the present application's method of turning on the switch for discharging the PFC inductor only once reduces the power consumption of the bootstrap capacitor in the bootstrap circuit connected to the gate of switch S1. The bootstrap capacitor does not require increased size, reducing circuit cost and facilitating miniaturization of devices equipped with the totem-pole PFC circuit.

[0005] Therefore, the following technical solutions are adopted in the embodiments of this application:

[0006] In a first aspect, this application provides a control method for a totem-pole PFC circuit, the method being executed by a controller, comprising: sampling the electrical parameters of a PFC inductor in the totem-pole PFC circuit; determining the time of the previous switching cycle of the totem-pole PFC circuit based on the electrical parameters of the PFC inductor, the time of the previous switching cycle being determined based on the previous charging time and the previous discharging time of the PFC inductor; when the time of the previous switching cycle is less than a set switching time, sending a control signal to a first switch, the first switch being a switch that discharges the PFC inductor when the AC current at the input terminal of the totem-pole PFC circuit is in the positive half-cycle, the control signal being used to discharge the bootstrap capacitor in a bootstrap circuit coupled to the switch.

[0007] In this embodiment, when the totem-pole PFC circuit performs the switching transition in the current switching cycle, it first obtains the time of the previous switching cycle (i.e., the switching frequency) and determines whether the time of the previous switching cycle is greater than the set switching time. If the time of the previous switching cycle is less than the set switching time, in the current switching cycle, the switching of the PFC inductor discharge is delayed by a set threshold time. After the PFC inductor is fully charged, the switching of the PFC inductor discharge is turned on again, achieving that the switching of the PFC inductor discharge is turned on only once. Compared with the prior art, by eliminating the first turn-on of the PFC inductor discharge switch and the second turn-on of the retention switch in a switching cycle, the power consumption of the bootstrap capacitor CQbst in the bootstrap circuit can be reduced, allowing the totem-pole PFC circuit to achieve ZVS across the entire input range. The totem-pole PFC circuit protected by this application embodiment can be applied in relatively small devices, expanding the application scenarios of the totem-pole PFC circuit.

[0008] In one embodiment, determining the time of the previous switching cycle of the totem pole PFC circuit based on the electrical parameters of the PFC inductor includes: detecting the current value flowing through the PFC inductor, where the electrical parameter is the current value; determining the time when the previous current value flowing through the PFC inductor decreased from a first threshold to zero and the time when the previous current value flowing through the PFC inductor increased from zero to the first threshold, thereby obtaining the time of the previous switching cycle.

[0009] In this embodiment, the time of one switching cycle of the totem pole PFC circuit is obtained by using the current flowing through the PFC inductor and the time of current change during charging and discharging of the PFC inductor.

[0010] In one embodiment, sending a control signal to the first switch specifically includes: sending a control signal to the first switch after a delay of a set threshold time, wherein the set threshold time is greater than or equal to the difference between the set switch time and the previous switch cycle.

[0011] In one embodiment, the method further includes: detecting the current value flowing through the PFC inductor, wherein the electrical parameter is the current value; and determining the time of the current switching cycle of the totem pole PFC circuit when the current value flowing through the PFC inductor is less than a second threshold.

[0012] In this implementation, the current flowing through the PFC inductor is used. When the current value is less than a set threshold, it indicates that the totem-pole PFC circuit has completed the charging and discharging processes of the PFC inductor in the current switching cycle. By calculating the time of the current switching cycle, parameters are provided for whether to delay the conduction time in the next switching cycle.

[0013] In one embodiment, the method further includes: stopping the transmission of control signals to the first switch; sampling the electrical parameters of the input and output terminals of the totem pole PFC circuit, wherein the output terminal is the port through which the totem pole PFC circuit outputs DC power to the outside; and sending control signals to the second switch, wherein the second switch is a switch that charges the PFC inductor when the AC power at the input terminal of the totem pole PFC circuit is in the positive half-cycle.

[0014] In one embodiment, sending a control signal to the second switch includes: when the voltage at the input terminal of the totem pole PFC circuit is not greater than half of the voltage at the output terminal of the totem pole PFC circuit, detecting the input voltage of the detection circuit, wherein the input voltage of the detection circuit is the voltage across the resistor in the detection circuit from the high-frequency bridge arm in the totem pole PFC circuit; and sending a control signal to the second switch when the input voltage of the detection circuit crosses zero.

[0015] In this embodiment, when the totem-pole PFC circuit enters the DCM operating mode, because the current switching cycle of the totem-pole PFC circuit is less than the set switching time, it will not immediately send a control signal to the first switch to turn it off. At this time, the totem-pole PFC circuit enters LC resonance, oscillating until the current switching cycle is not less than the set switching time, and then sends a control signal to the second switch to turn it on. The totem-pole PFC circuit then enters the next switching cycle, achieving zero-voltage turn-on of the second switch.

[0016] In one embodiment, sending a control signal to the second switch includes: detecting the input voltage of the detection circuit when the voltage at the input terminal of the totem pole PFC circuit is greater than half of the voltage at the output terminal of the totem pole PFC circuit; sending a control signal to the first switch when the input voltage of the detection circuit crosses zero negatively; detecting the current value flowing through the PFC inductor; stopping sending the control signal to the first switch when the current value flowing through the PFC inductor is less than a second threshold; and sending a control signal to the second switch when the input voltage of the detection circuit crosses zero positively.

[0017] In this embodiment, when the totem-pole PFC circuit enters the DCM operating mode, because the current switching cycle of the totem-pole PFC circuit is less than the set switching time, it will not immediately send a control signal to the first switch to turn it off. If a negative zero-crossing of the PFC inductor voltage is detected, and the moment when the PFC inductor voltage oscillates to its peak value is determined, a control signal is sent to the first switch to turn it on, achieving soft switching of the first switch. After the first switch is turned on, when the current through the PFC inductor is less than the set current, the sending of control signals to the first switch stops. At this time, the totem-pole PFC circuit enters LC resonance, and when the oscillation time of the current switching cycle is not less than the set switching time, a control signal is sent to the second switch to turn it on. The totem-pole PFC circuit then enters the next switching cycle, achieving zero-voltage turn-on of the second switch.

[0018] In one embodiment, before determining the time of the previous switching cycle of the totem pole PFC circuit based on the electrical parameters of the PFC inductor, the method further includes: sending a control signal to the second switch; detecting the current value flowing through the PFC inductor; and stopping sending the control signal to the second switch when the current value flowing through the PFC inductor crosses negative zero.

[0019] Secondly, embodiments of this application also provide a control device for a totem-pole PFC circuit, comprising: a totem-pole PFC circuit, a detection circuit, an input voltage detection unit, an output voltage detection unit, and a control unit. The detection circuit is used to output the electrical parameters of the PFC inductor of the totem-pole PFC circuit to the control unit. The input voltage detection unit is used to output the AC voltage at the input terminal of the totem-pole PFC circuit to the control unit. The output voltage detection unit is used to output the DC voltage at the output terminal of the totem-pole PFC circuit to the control unit. The control unit is used to determine the time of the previous switching cycle of the totem-pole PFC circuit based on the electrical parameters of the PFC inductor. The time of the previous switching cycle is determined based on the previous charging time and the previous discharging time of the PFC inductor. When the time of the previous switching cycle is less than a set switching time, a control signal is sent to a first switch. The first switch is a switch that discharges the PFC inductor when the AC current at the input terminal of the totem-pole PFC circuit is in the positive half-cycle. The control signal is used to discharge the bootstrap capacitor in the bootstrap circuit coupled to the switch.

[0020] In one embodiment, the control unit is specifically configured to determine, based on the current value of the PFC inductor input at the third port, the time when the previous current value flowing through the PFC inductor decreased from a first threshold to zero and the time when the previous current value flowing through the PFC inductor increased from zero to the first threshold, thereby obtaining the time of the previous switching cycle.

[0021] In one embodiment, the control unit is specifically used to send a control signal to the first switch after a delay of a set threshold time, wherein the set threshold time is greater than or equal to the difference between the set switch time and the previous switch cycle.

[0022] In one embodiment, the control unit is further configured to determine the current switching cycle time of the totem pole PFC circuit based on the current value of the PFC inductor input at the third port, when the current value flowing through the PFC inductor is less than a second threshold.

[0023] In one embodiment, the control unit is further configured to stop sending control signals to the first switch; and to send control signals to the second switch based on the voltage input by the input voltage detection unit and the voltage input by the output voltage detection unit, wherein the second switch is a switch that charges the PFC inductor when the AC current at the input terminal of the totem pole PFC circuit is in the positive half-cycle.

[0024] In one embodiment, the control unit is specifically configured to detect the input voltage of the detection circuit when the voltage at the input terminal of the totem pole PFC circuit is not greater than half of the voltage at the output terminal of the totem pole PFC circuit, wherein the input voltage of the detection circuit is the voltage across the resistor in the detection circuit from the high-frequency bridge arm in the totem pole PFC circuit; and to send a control signal to the second switch when the input voltage of the detection circuit crosses zero.

[0025] In one embodiment, the control unit is specifically configured to: detect the input voltage of the detection circuit when the voltage at the input terminal of the totem pole PFC circuit is greater than half of the voltage at the output terminal of the totem pole PFC circuit; send a control signal to the first switch when the input voltage of the detection circuit crosses zero negatively; detect the current value flowing through the PFC inductor; stop sending the control signal to the first switch when the current value flowing through the PFC inductor is less than a second threshold; and send a control signal to the second switch when the input voltage of the detection circuit crosses zero positively.

[0026] In one embodiment, the control unit is further configured to send a control signal to the second switch; detect the current value flowing through the PFC inductor; and stop sending the control signal to the second switch when the current value flowing through the PFC inductor crosses zero.

[0027] Thirdly, embodiments of this application provide an electronic device, including: a control device for various possible implementations of the totem-pole PFC circuit as described in the second aspect. The electronic device can be a base station, charging pile, switch, electric vehicle, etc., and is not limited thereto herein. Attached Figure Description

[0028] The accompanying drawings used in the description of the embodiments or prior art are briefly introduced below.

[0029] Figure 1 This is a schematic diagram of a totem pole PFC circuit in the prior art;

[0030] Figure 2(a) is a schematic diagram of the current flow direction in another totem pole PFC circuit in the prior art;

[0031] Figure 2(b) is a schematic diagram of the current flow direction in another totem pole PFC circuit in the prior art;

[0032] Figure 2(c) is a schematic diagram of the current flow direction in another totem pole PFC circuit in the prior art;

[0033] Figure 2(d) is a schematic diagram of the current flow direction in another totem pole PFC circuit in the prior art;

[0034] Figure 3 This is a schematic diagram of another totem pole PFC circuit in the prior art;

[0035] Figure 4 This is a simulation diagram showing the changes of various electrical parameters over time in the DCM operating mode of the totem pole PFC circuit in the prior art.

[0036] Figure 5 This is a schematic diagram of the control device for a totem pole PFC circuit provided in the embodiments of this application;

[0037] Figure 6 The input voltage V of the totem pole PFC circuit provided in this embodiment is... AC A circuit diagram showing the charging and discharging conversion of the PFC inductor during the positive half-cycle.

[0038] Figure 7 This is a simulation diagram showing the changes of various electrical parameters over time when the totem pole PFC circuit provided in this embodiment enters the CRM working mode.

[0039] Figure 8 This is a simulation diagram showing the changes of various electrical parameters over time when a totem pole PFC circuit enters the DCM working mode, as provided in the embodiments of this application.

[0040] Figure 9 This is a simulation diagram showing the changes of various electrical parameters over time when another totem pole PFC circuit provided in this embodiment of the application enters the DCM working mode;

[0041] Figure 10 This is a flowchart of a control method for a totem pole PFC circuit provided in an embodiment of this application. Detailed Implementation

[0042] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0043] In this article, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The symbol " / " in this article indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0044] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0045] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0046] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0047] Figure 1 This is a schematic diagram of a totem-pole PFC circuit in the prior art. Figure 1 As shown, the totem pole PFC circuit includes input terminal 1, input terminal 2, PFC inductor L, switch S1, switch S2, switch S3, switch S4, and filter capacitor C. OUT Output terminals 3 and 4 are provided. Input terminals 1 and 2 can be electrically connected to an external power supply. Output terminals 3 and 4 can be electrically connected to multiple loads. Switches S1 and S2 are connected in series and electrically between output terminals 3 and 4. Switches S3 and S4 are connected in series and electrically between output terminals 3 and 4. Filter capacitor C... OUT Electrical connection is made between output terminal 3 and output terminal 4. Input terminal 1 is electrically connected to one end of PFC inductor L, and the other end of PFC inductor L is electrically connected between switch S1 and switch S2. Input terminal 2 is electrically connected between switch S3 and switch S4.

[0048] As shown in Figure 2(a), the input voltage V of the totem pole PFC circuit is... AC In the positive half-cycle, V AC >0. That is, input terminal 1 is positive and input terminal 2 is negative. At this time, the MOS transistor in switch S4 is turned on. When the PFC inductor L is charging, switch S1 in the totem pole PFC circuit is turned off and switch S2 is turned on. The devices in the totem pole PFC circuit through which current flows in sequence are: input terminal 1 → PFC inductor L → switch S2 → switch S4 → input terminal 2.

[0049] As shown in Figure 2(b), the input voltage V of the totem pole PFC circuit is... AC In the positive half-cycle, V AC>0. That is, input terminal 1 is positive and input terminal 2 is negative. At this time, the MOS transistor in switch S4 is turned on. When the PFC inductor L discharges, switch S1 in the totem pole PFC circuit is turned on and switch S2 is turned off. The devices in the totem pole PFC circuit through which current flows in sequence are: input terminal 1 → PFC inductor L → switch S1 → output terminal 3 → output terminal 4 → switch S4 → input terminal 2.

[0050] As shown in Figure 2(c), the input voltage V of the totem pole PFC circuit is... AC In the negative half-cycle, V AC <0. That is, input terminal 1 is negative and input terminal 2 is positive. At this time, the MOS transistor in switch S3 is turned on. When the PFC inductor L is charging, switch S1 in the totem pole PFC circuit is turned on and switch S2 is turned off. The devices in the totem pole PFC circuit through which current flows in sequence are: input terminal 2 → switch S3 → switch S1 → PFC inductor L → input terminal 1.

[0051] As shown in Figure 2(d), the input voltage V of the totem pole PFC circuit is... AC In the negative half-cycle, V AC <0. That is, input terminal 1 is negative and input terminal 2 is positive. At this time, the MOS transistor in switch S3 is turned on. When the PFC inductor L discharges, switch S1 in the totem pole PFC circuit is turned off and switch S2 is turned on. The devices in the totem pole PFC circuit through which current flows in sequence are: input terminal 2 → switch S3 → output terminal 3 → output terminal 4 → switch S2 → PFC inductor L → input terminal 1.

[0052] Existing totem-pole PFC circuits operate in three modes: continuous current mode (CCM), critical conduction mode (CRM), and discontinuous current mode (DCM). CCM refers to a switching cycle in which the current in the PFC inductor L is continuous and does not drop to zero. DCM refers to a switching cycle in which the current in the PFC inductor L is discontinuous and drops to zero. CRM is a mode that allows for a smooth transition from CCM to DCM in the totem-pole PFC circuit. To improve the switching efficiency of the totem-pole PFC circuit, the switches need to achieve zero-voltage switching (ZVS).

[0053] Figure 3 This is a schematic diagram of another totem-pole PFC circuit in the prior art. Figure 3 As shown, in Figure 1 Based on the totem-pole PFC circuit shown, the gates of switches S1, S2, S3, and S4 are electrically connected to a bootstrap circuit. If the bootstrap circuit inputs an electrical signal to the gate of a switch, the switch is in the ON state. If the bootstrap circuit does not input an electrical signal to the gate of a switch, the switch is in the OFF state.

[0054] In the prior art, the input voltage V of the totem pole PFC circuit AC In the positive half-cycle, V AC >0. That is, input terminal 1 is positive, and input terminal 2 is negative. If the input voltage V AC The voltage value and the output voltage V OUT The voltage values ​​satisfy V AC >0.5V OUT The totem pole PFC circuit is in DCM mode. At this time, the current i flowing through the PFC inductor L in the totem pole PFC circuit is... L Voltage V at node SW1 SW1 The relationship between the conduction states of switch S1 and switch S2 and time is as follows: Figure 4 As shown.

[0055] like Figure 4 As shown, at time t0, switch S1 in the totem-pole PFC circuit is open. When the switching cycle time T of the totem-pole PFC circuit is less than the set switching cycle time Tmin, that is, when the switching frequency of the current switching cycle is greater than the maximum switching frequency, switch S1 in the totem-pole PFC circuit needs to be turned on to allow the PFC inductor L to discharge completely. During the time interval t0-t1, switch S1 in the totem-pole PFC circuit is turned on. At time t1, the voltage V at node SW1... SW1 When the resonance reaches its peak, switch S1 opens again. The time period for switch S1 to turn on again is t2-t3. If the voltage V at node SW1... SW1 It can resonate to 0V, and can enable the totem pole PFC circuit to achieve ZVS by allowing switch S2 to be in DCM mode.

[0056] In the prior art, the input voltage V of the totem pole PFC circuit AC During the positive half-cycle, switch S1 needs to be turned on twice. Each time switch S1 is turned on, it consumes the bootstrap capacitor C in the bootstrap circuit. Qbst The amount of electricity. If switch S1 is turned on multiple times, it will cause the bootstrap capacitor C in the bootstrap circuit to be affected. Qbst and bootstrap voltage V Qbst The self-energizing capacitor C continuously decays, consuming its own power. Qbst The amount of charge is relatively large. This is to meet the requirements of the bootstrap capacitor C. QbstThe amount of electricity causes switch S1 to conduct twice, which can increase the capacitance of the bootstrap capacitor. Increasing the capacitance will increase the cost of the circuit. Increasing the capacitance will also result in a larger capacitor size, which is not conducive to the miniaturization of devices with totem-pole PFC circuits.

[0057] To address the shortcomings of existing totem-pole PFC circuits, this application presents a totem-pole PFC circuit and a method for controlling it. During the switching process of this switching cycle, when the input voltage V of the totem-pole PFC circuit... AC During the positive half-cycle, the time of the previous switching cycle (i.e., the switching frequency) is first obtained, and it is determined whether the time of the previous switching cycle is greater than the set switching time. If the time of the previous switching cycle is less than the set switching time, the switch that discharges the PFC inductor L is delayed by a set threshold time during this switching cycle. After the PFC inductor is fully charged, the switch that discharges the PFC inductor is turned on again, thus ensuring that the switch that discharges the PFC inductor L is turned on only once in one switching cycle. In this embodiment, in one switching cycle, switch S1 cancels the first switching on but retains the second switching on, which can reduce the bootstrap capacitance C in the bootstrap circuit connected to the gate of switch S1. Qbst The low power consumption allows the totem-pole PFC circuit to achieve ZVS across the entire input range. The totem-pole PFC circuit protected in this application can be used in smaller devices, expanding its application scenarios.

[0058] Figure 5 This is a schematic diagram of the control device for a totem pole PFC circuit provided in an embodiment of this application. Figure 5 As shown, the control device 500 of the totem pole PFC circuit includes a totem pole PFC circuit 510, an input voltage detection unit 520, an output voltage detection unit 530, a detection circuit 540, and a control unit 550. The totem pole PFC circuit 510 converts the input AC power into DC power. The input voltage detection unit 520 is coupled to the input terminal of the totem pole PFC circuit 510 and is used to detect the input voltage V of the totem pole PFC circuit 510. AC The voltage value is detected and the detection result is sent to the control unit 550. The output voltage detection unit 530 is coupled to the output terminal of the totem pole PFC circuit 510 and is used to detect the voltage V output by the totem pole PFC circuit 510. OUTThe detection circuit 540 measures the voltage value at node SW1 and sends the detection result to the control unit 550. The input terminal of the detection circuit 540 is electrically connected to the totem pole PFC circuit 510, and the output terminal of the detection circuit 540 is electrically connected to the control unit 550. The control unit 550's output terminal is electrically connected to each switch in the totem pole PFC circuit 510. Based on the detection results from the input voltage detection unit 520, the output voltage detection unit 530, the voltage value at node SW1 input to the detection circuit 540, and the current value of resistor R, it generates control signals and sends these signals to each switch in the totem pole PFC circuit 510.

[0059] like Figure 5 As shown, the totem pole PFC circuit 510 includes input terminal 1, input terminal 2, switch S1, switch S2, switch S3, switch S4, diode D1, diode D2, PFC inductor L, resistor R, and filter capacitor C. OUT Output terminals 3 and 4 are provided. Input terminals 1 and 2 can be electrically connected to an external power supply to receive electrical signals input from the external power supply. Input terminals 1 and 2 can also be electrically connected to the input voltage detection unit 520. The input voltage detection unit 520 can detect the input voltage V through input terminals 1 and 2. AC The voltage value. Switches S1 and S2 are connected in series and electrically connected between output terminals 3 and 4. Switches S3 and S4 are connected in series and electrically connected between output terminals 3 and 4. Diodes D1 and D2 are connected in series and electrically connected between output terminals 3 and 4. Filter capacitor C OUT The circuit connects output terminals 3 and 4. Input terminal 1 is electrically connected to the node between diodes D1 and D2. Input terminal 2 is electrically connected to node SW2 between switches S3 and S4. One end of the PFC inductor L is electrically connected to the node between diodes D1 and D2, and the other end is electrically connected to node SW1 between switches S1 and S2. The PFC inductor L can be used with other components to reduce the phase difference between the fundamental current and voltage of the AC input, acting as a rectifier and filter. Output terminals 3 and 4 can be electrically connected to multiple loads to provide power to each load. Output terminals 3 and 4 can also be electrically connected to the output voltage detection unit 530. The output voltage detection unit 530 can detect the input voltage V through output terminals 3 and 4. OUT The voltage value.

[0060] The totem pole PFC circuit used in this application is not limited to Figure 5The structure shown can also be used for other totem pole PFC circuits. This application is only used as an example and is not intended to limit the scope.

[0061] Switches S1, S2, S3, and S4 are generally made of metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), diodes, or other similar devices. Taking a MOSFET as an example, the gate bootstrap circuit (not shown in the figure) of each MOSFET is electrically connected. The output of the control unit 550 is electrically connected to the bootstrap circuit. The control unit 550 can send a pulse width modulation (PWM) signal to the bootstrap circuit to discharge the bootstrap capacitor in the bootstrap circuit, allowing current to enter the gate of the MOSFET, thus putting the MOSFET in the on state. In this application, switches S1, S2, S3, and S4 all include a MOSFET and a diode. One end of the diode is electrically connected to the source of the MOSFET, and the other end of the diode is electrically connected to the drain of the MOSFET. The direction of current flowing through the MOSFET is opposite to the direction of current flowing through the diode.

[0062] like Figure 5 As shown, in switch S1, the current flowing through the diode is "input terminal 1 → switch S1", and the current flowing through the MOS transistor is "switch S1 → input terminal 1". In switch S2, the current flowing through the diode is "switch S2 → input terminal 1", and the current flowing through the MOS transistor is "input terminal 1 → switch S2". In switch S3, the current flowing through the diode is "input terminal 2 → switch S3", and the current flowing through the MOS transistor is "switch S3 → input terminal 2". In switch S4, the current flowing through the diode is "switch S4 → input terminal 2", and the current flowing through the MOS transistor is "input terminal 2 → switch S4".

[0063] In this application, the control unit 550 can control the MOS transistors in switches S1, S2, S3, and S4 to be in an on or off state, allowing the totem-pole PFC circuit 510 to achieve a similar function to... Figures 2(a)-2(d) The four working modes are shown below. Specifically:

[0064] In one embodiment, the input voltage V of the totem pole PFC circuit AC In the positive half-cycle, V AC>0. That is, input terminal 1 is positive and input terminal 2 is negative. At this time, the MOS transistor in switch S4 is turned on. When the PFC inductor L is charging, the MOS transistor in switch S1 is turned off and the MOS transistor in switch S2 is turned on. The devices in the totem pole PFC circuit 510 with current flowing in sequence are: input terminal 1 → PFC inductor L → switch S2 → switch S4 → input terminal 2.

[0065] In one embodiment, the input voltage V of the totem pole PFC circuit AC In the positive half-cycle, V AC >0. That is, input terminal 1 is positive and input terminal 2 is negative. At this time, the MOS transistor in switch S4 is turned on. When the PFC inductor L discharges, the MOS transistor in switch S1 is turned on, and the MOS transistor in switch S2 is turned off. The devices in the totem pole PFC circuit 510 with current flowing in sequence are: input terminal 1 → PFC inductor L → switch S1 → output terminal 3 → output terminal 4 → switch S4 → input terminal 2.

[0066] In one embodiment, the input voltage V of the totem pole PFC circuit AC In the negative half-cycle, V AC <0. That is, input terminal 1 is negative. At this time, the MOS transistor in switch S3 is turned on. When the PFC inductor L is charging, the MOS transistor in switch S1 is turned on, and the MOS transistor in switch S2 is turned off. The devices in the totem pole PFC circuit 510 with current flowing in sequence are: input terminal 2 → switch S3 → switch S1 → PFC inductor L → input terminal 1.

[0067] In one embodiment, the input voltage V of the totem pole PFC circuit AC In the negative half-cycle, V AC <0. That is, input terminal 1 is negative. At this time, the MOS transistor in switch S3 is turned on. When the PFC inductor L discharges, switch S1 in the totem pole PFC circuit is turned off, and switch S2 is turned on. The devices in the totem pole PFC circuit through which current flows in sequence are: input terminal 2 → switch S3 → output terminal 3 → output terminal 4 → switch S2 → PFC inductor L → input terminal 1.

[0068] like Figure 5 As shown, the resistor R in the totem pole PFC circuit 510 is electrically connected to the branch containing switch S3 and the filter capacitor C. OUT Between the branches, an output terminal 5 is provided between resistor R and output terminal 4, and output terminal 5 is electrically connected to control unit 550. Control unit 550 can receive the current i passing through resistor R through output terminal 5. R In this application, since the resistor R and the PFC inductor L are generally in the same circuit, the current i through the resistor R is... R With the current i through the PFC inductor LL They are essentially the same. Therefore, the control unit 550 receives the current i through the resistor R. R The current i through the PFC inductor L can be obtained. L .

[0069] The detection circuit 540 includes a detection capacitor Cd and a detection resistor Rd. The detection capacitor Cd and the detection resistor Rd are connected in series, and the branch containing the detection capacitor Cd and the detection resistor Rd is connected in parallel with switch S2. One end of this branch is electrically connected to node SW1. An output terminal 6 is provided at node DT between the detection capacitor Cd and the detection resistor Rd, and output terminal 6 is electrically connected to control unit 550. During the charging and discharging process of the detection capacitor Cd, the voltage V of capacitor Cd... DT Equal to the voltage V at node SW1 SW1 The control unit 550 receives the voltage V of capacitor Cd through output terminal 6. DT Then, the voltage V at node SW1 can be obtained. SW1 .

[0070] In this embodiment, "switch S1 is on" means that the MOS transistor in switch S1 is turned on, and "switch S1 is off" means that the MOS transistor in switch S1 is turned off. The same logic applies to other switches.

[0071] Figure 6 The input voltage V of the totem pole PFC circuit provided in this embodiment is... AC A circuit diagram illustrating the charging and discharging conversion of the PFC inductor during the positive half-cycle. (See diagram below.) Figure 6 As shown, when the input voltage V of the totem pole PFC circuit 510 is... AC It is in the positive half-cycle. That is, input terminal 1 is positive and input terminal 2 is negative. At this time, switch S4 is always in the on state.

[0072] like Figure 6 As shown in (a), during the discharge process of the PFC inductor L, switch S1 in the totem pole PFC circuit is turned on, and switch S2 is turned off. The devices in the totem pole PFC circuit 510 with current flowing sequentially are: input terminal 1 → PFC inductor L → switch S1 → output terminal 3 → output terminal 4 → switch S4 → input terminal 2. At this time, the current iL flowing through the PFC inductor L discharges in the reverse direction, and the current iR sampled at resistor R changes with the current iL of the PFC inductor L during the discharge process.

[0073] like Figure 6As shown in (b), during the charging process of the PFC inductor, the switch S1 in the totem-pole PFC circuit is turned off and the switch S2 is turned on. The devices through which the current in the totem-pole PFC circuit 510 flows in sequence are: input terminal 1 → PFC inductor L → switch S2 → switch S4 → input terminal 2. At this time, the current iL flowing through the PFC inductor L is charging forward, and the current iR sampled at the resistor R changes with the current iL of the PFC inductor L during the charging process.

[0074] In this application, Ton is used to represent the charging time of the PFC inductor L, Toff is used to represent the time when the current i L decreases from the peak value to 0 A, and Tmin represents the time for a complete charge and discharge of the PFC inductor L at the maximum switching frequency. The control unit 550 can determine the operating mode of the totem-pole PFC circuit 510 according to the relationship between Ton + Toff and Tmin. If Ton + Toff > Tmin, the totem-pole PFC circuit 510 enters the CRM operating mode. At this time, the control unit 550 can directly send the PWM S1 signal to the switch S1 to make the switch S1 in the on state. If Ton + Toff < Tmin, the totem-pole PFC circuit 510 enters the DCM operating mode. At this time, the switching frequency of the current switching cycle of the totem-pole PFC circuit 510 is greater than the maximum switching frequency. After the control unit 550 delays the set threshold time, it sends the PWM S1 signal to the switch S1 to make the switch S1 in the on state. In one switching cycle, the control unit 550 only sends the PWM S1 signal to the switch S1 once to make the switch S1 conduct once, which can reduce the power consumption of the boost capacitor C in the boost circuit. Qbst Among them, the delay set threshold time is the difference between the time of the current switching cycle and the set switching time. Preferably, the delay set threshold time is generally greater than or equal to the difference between the time of the current switching cycle and the set switching time.

[0075] When the control unit 550 determines that the totem-pole PFC circuit 510 enters the CRM operating mode, it sends the PWM S1 signal to the switch S1 to make the switch S1 in the on state. At this time, the on state of the switch S1 in the totem-pole PFC circuit 510, the current i at the resistor R R , the voltage V at the node SW1 SW1 , the voltage V at the node DT DT and the on state of the switch S2 change with time as Figure 7 shown.

[0076] As Figure 7 shown, the control unit 550 receives the input voltage V input by the input voltage detection unit 520 AC , the output voltage V input by the output voltage detection unit 530OUT The voltage V input to the detection circuit 540 DT The current i input at input terminal 5 R At time t1, since the switching frequency of the current switching cycle of the totem pole PFC circuit 510 is less than the maximum switching frequency, the control unit 550 continues to detect the current i input at input terminal 5. R .

[0077] At time t2, the control unit 550 receives the current i from the resistor R input at input terminal 5. R Determine the current i through the PFC inductor L. L If the control unit 550 detects a current i through the PFC inductor L L When the current is less than the set current -ith, the PFC inductor stops sending the PWM S1 signal to switch S1, keeping switch S1 in the open state. If the control unit 550 detects the current i through the PFC inductor L... L When the current is not less than the set current -ith, the control unit 550 continues to detect the current i. R The value of the current ith must be at least greater than the sum of the currents required for charging and discharging the parasitic capacitances of switch S1 and switch S2.

[0078] Control unit 550 receives voltage V input from detection circuit 540 DT Then, determine the voltage V at node SW1. SW1 If the control unit 550 detects a voltage of 0V at node SW1, or if the control unit 550 detects a current of 0A in the PFC inductor L, the energy in the PFC inductor L and the energy in the capacitor of the MOS transistor are fed back to the input side, i.e., input terminal 1. At this time, the voltage between input terminal 1 and input terminal 2 can be considered a fixed value. According to the law of conservation of energy:

[0079]

[0080] Among them, V AC V is the input voltage. OUT For the output voltage, C OSS i is the sum of the parasitic capacitance of switch S1 and the parasitic capacitance of switch S2. L Let i be the current in the PFC inductor L. S1 Let i be the current of switch S1. S2 The current is for switch S2.

[0081] Transforming formula (1), we obtain the current i of the PFC inductor L. L for:

[0082]

[0083] According to formula (2), when When V is available, it can meet the requirements for soft switching. AC <V OUT When V / 2, the inequality always holds. AC >V OUT / 2 o'clock, When V AC =V OUT At that time, i L The maximum value can be obtained. Therefore, the current ith should be set to satisfy:

[0084]

[0085] Therefore, at time t2, if the current i in the PFC inductor L... L When the current is less than the set current -ith, the control unit 550 stops sending the PWM S1 signal to switch S1, keeping switch S1 in the open state. After entering the resonance process, the parasitic capacitance of the PFC inductor L and the parasitic capacitance of switch S2 result in the voltage V at node SW1. SW1 It will decrease as the parasitic capacitance of switch S2 discharges.

[0086] At time t3, after the parasitic capacitance of switch S2 has discharged, the voltage V at node SW1 is... SW1 Will from V OUT The voltage drops to 0V. Control unit 550 detects the voltage V at node SW1 using detection circuit 540. SW1 When a voltage jump occurs, determine the slope of the voltage jump, k = dV. SW1 / dt. The control unit 550 can calculate the current generated in the detection capacitor Cd based on the slope k of the voltage jump at node SW1, which is id = Cd·k. When the current flowing through resistor Rd is id, a voltage V is generated at node DT. DT , for V DT =id·Rd. Control unit 550 detects the voltage V at node SW1. SW1 When the voltage drops to 0V, the voltage V at node DT can be determined. DT It crosses zero. That is, the voltage V at node DT is positive. DT The value changes from negative to positive. Therefore, the control unit 550 receives the input voltage V from the detection circuit 550. DT The voltage value can be used to determine that the voltage at node SW1 is positively zero-crossing. By sending a PWM S2 signal to switch S2, switch S2 is put into the conducting state, thus realizing zero-voltage turn-on of switch S2.

[0087] Compared Figure 4 The simulation results shown indicate that the input voltage V of the totem-pole PFC circuit is... ACDuring the positive half-cycle, the bootstrap circuit in the control device 500 of the totem pole PFC circuit protected in this application only needs to turn on the switch S1 once, and the bootstrap voltage V in the bootstrap circuit... Qbst The fluctuation range is relatively small, and the amount of charge consumed by the bootstrap capacitor C is also relatively small. Therefore, the bootstrap capacitor in the bootstrap circuit can be designed to be smaller, which can reduce the cost of the circuit and also facilitate the miniaturization of devices equipped with totem-pole PFC circuits.

[0088] When the control unit 550 determines that the totem-pole PFC circuit 510 has entered the DCM operating mode, since the switching frequency of the current switching cycle of the totem-pole PFC circuit 510 is greater than the maximum switching frequency, it will not send a PWM S1 signal to switch S1, keeping switch S1 in the off state. At this time, the totem-pole PFC circuit 510 enters LC resonance, and the current iL flowing through the PFC inductor L discharges in reverse. The control unit 550 determines the time T of the current switching cycle based on the charging and discharging time Ton + Toff of the PFC inductor L. If the control unit 550 determines that the time T of the current switching cycle is greater than or equal to the time Tmin for the PFC inductor L to complete one full charge and discharge cycle under the maximum switching frequency limit, it needs to determine the input voltage V. AC Is it greater than the output voltage V? OUT Half of the value is used, and different methods are employed to achieve zero-voltage switching of switch S2 based on different results. Specifically:

[0089] like Figure 8 As shown, when V AC <0.5V OUT At that time, the voltage V at node SW1 SW1 Valley value 2V AC -V OUT It will be below 0V. At time t2, the voltage V at node SW1 will be below 0V. SW1 When the voltage drops to 0V, the voltage V at node SW1 is reduced due to the voltage clamping of the body diode of switch S2. SW1 The voltage remains at 0V between t2 and t3. At this time, the charging and discharging time T of the PFC inductor L in the totem pole PFC circuit 510 does not satisfy T≥Tmin, so the control unit 550 will not send the PWM S2 signal to the switch S2.

[0090] When the current i flows through the totem pole PFC circuit 510 R After oscillation to time t4, once the current switching cycle time T of the totem-pole PFC circuit 510 is greater than or equal to Tmin, the switching frequency of the current switching cycle of the totem-pole PFC circuit 510 is less than the maximum switching frequency, thus satisfying the maximum switching frequency limit. At time t5, the control unit 550 detects the voltage V at node DT. DT When the zero-crossing is positive, determine the voltage V at node SW1. SW1The voltage oscillates to 0V. The control unit 550 sends a PWM signal to switch S2, causing switch S2 to turn on again. The totem-pole PFC circuit 510 then enters the next switching cycle, achieving zero-voltage turn-on of switch S2.

[0091] Compared Figure 4 The simulation results shown indicate that the input voltage V of the totem-pole PFC circuit is... AC During the positive half-cycle, the bootstrap circuit in the control device 500 of the totem pole PFC circuit protected in this application only needs to turn on the switch S1 once, and the bootstrap voltage V in the bootstrap circuit... Qbst The fluctuation range is relatively small, and the amount of charge consumed by the bootstrap capacitor C is also relatively small. Therefore, the bootstrap capacitor in the bootstrap circuit can be designed to be smaller, which can reduce the cost of the circuit and also facilitate the miniaturization of devices equipped with totem-pole PFC circuits.

[0092] like Figure 9 As shown, when V AC >0.5V OUT At that time, the voltage V at node SW1 SW1 Valley value 2V AC -V OUT The voltage will be higher than 0V. At time t01, the control unit 640 detects that the time T of the previous switching cycle is less than the set switching time Tmin, indicating a switching frequency limitation, and therefore delays the time by t02-t01. The control unit 550 receives the input voltage V from input terminal 6. DT If the control unit 550 detects the voltage V at node DT DT Negative zero crossing, determine the voltage V at node SW1. SW1 Oscillation to peak V OUT At that moment.

[0093] At time t3, the control unit 550 detects the voltage V at node SW1. SW1 Reaching output voltage V OUT When the switch is in operation, a PWM signal is sent to switch S1 to put switch S1 in the on state, thus realizing the soft switching of switch S1.

[0094] At time t4, after switch S1 is turned on, control unit 550 calculates the current i input at input terminal 5. R Determine the current i through the PFC inductor L. L If the control unit 550 detects the current i through the PFC inductor L L When the current is less than the set current -ith, the PWM S1 signal is stopped being sent to switch S1. SW1 The oscillation process begins. At this time, the voltage V at node SW1 is... SW1It can oscillate up to 0V. If the control unit 550 detects the current i through the PFC inductor L... L If the current i is not less than the set current -ith, continue to detect the current i. R .

[0095] At time t5, the control unit 550 detects the voltage V at node DT. DT A positive zero crossing indicates that the voltage V at node SW1 is... SW1 The voltage has dropped to 0V. The control unit 550 can send a PWM signal to switch S2, causing switch S2 to turn on again. The totem-pole PFC circuit 510 then enters the next switching cycle, achieving zero-voltage turn-on of switch S2.

[0096] Compared Figure 4 The simulation results shown indicate that the input voltage V of the totem-pole PFC circuit is... AC During the positive half-cycle, the bootstrap circuit in the control device 500 of the totem pole PFC circuit protected in this application only needs to turn on the switch S1 once, and the bootstrap voltage V in the bootstrap circuit... Qbst The fluctuation range is relatively small, and the amount of charge consumed by the bootstrap capacitor C is also relatively small. Therefore, the bootstrap capacitor in the bootstrap circuit can be designed to be smaller, which can reduce the cost of the circuit and also facilitate the miniaturization of devices equipped with totem-pole PFC circuits.

[0097] Figure 10 This is a flowchart illustrating a control method for a totem pole PFC circuit provided in an embodiment of this application. Figure 10 As shown, the method for controlling the totem pole PFC circuit is executed by the aforementioned control unit 550, when the input voltage V AC During the positive half-cycle, the control unit 550 executes the following steps:

[0098] Step S1001: Send a control signal to switch S2.

[0099] Specifically, the input voltage detection unit 520 inputs voltage V to the control unit 550. AC The control unit 550 adjusts the input voltage V. AC Determine the input voltage V AC It is in the positive or negative half-cycle. If the input voltage V AC During the positive half-cycle, the control unit 550 sends a PWM signal to switch S2 in the totem-pole PFC circuit 510, causing switch S2 to be in the on state. At this time, the PFC inductor is in the charging state. The direction of current flow in the totem-pole PFC circuit 510 is: input terminal 1 → PFC inductor L → switch S2 → switch S4 → input terminal 2.

[0100] Step S1002: After the set conduction time, stop sending control signals to switch S2.

[0101] Step S1003: Determine whether the time of the previous switching cycle is less than the set switching time. That is, determine whether the switching frequency of the previous switching cycle is subject to a switching frequency limit. If yes, proceed to step S1004; otherwise, proceed to step S1005.

[0102] Specifically, after switch S2 is turned on, current is generated during the charging process of capacitors such as the parasitic capacitance of PFC inductor L and switch S2. Once all capacitors in the totem-pole PFC circuit 510 have completed charging, control unit 550 stops sending PWM S2 signals to switch S2, leaving switch S2 in the off state. At this time, the current in the totem-pole PFC circuit 510 gradually decreases to 0 as PFC inductor L discharges. Control unit 550 detects the value of the current iR in the totem-pole PFC circuit 510 after receiving the current iR from input terminal 5, thus determining the change in the current iR in the totem-pole PFC circuit 510.

[0103] If the control unit 550 detects that the current iR in the totem pole PFC circuit 510 has not crossed negative zero, the control unit 550 continues to detect the current iR in the totem pole PFC circuit 510. If the control unit 550 detects that the current iR in the totem pole PFC circuit 510 has crossed negative zero, the control unit 550 puts the totem pole PFC circuit 510 into DCM operating mode.

[0104] In step S1004, after delaying the set threshold time, a control signal is sent to switch S1.

[0105] Step S1005: Send a control signal to switch S1.

[0106] Specifically, after the control unit 550 determines that the current iR in the totem-pole PFC circuit 510 has crossed negative zero, it determines whether the time of the previous switching cycle is less than the set switching time, that is, whether the switching frequency of the previous switching cycle is limited. If the control unit 550 detects that the previous switching cycle is less than the set switching time, i.e., a switching frequency limitation has occurred, it can delay for a set threshold time before sending the PWM S1 signal to the switch S1. The set threshold time is greater than or equal to the difference between the time of the previous switching cycle and the set switching time.

[0107] If the control unit 550 detects that the previous switching cycle is not less than the set switching time, i.e., there is no switching frequency limitation, the control unit 550 can directly send a PWM S1 signal to switch S1, allowing the totem-pole PFC circuit 510 to enter the DCM operating mode. At this time, the direction of current flow in the totem-pole PFC circuit 510 is: input terminal 1 → PFC inductor L → switch S1 → output terminal 3 → output terminal 4 → switch S4 → input terminal 2. The direction of current flow in the totem-pole PFC circuit 510 is opposite to the direction of current flow in step S1001.

[0108] Step S1006: Detect the value of the current iR flowing through resistor R.

[0109] Step S1007: Determine whether the current iR is less than the set current ith. If yes, proceed to step S1008; otherwise, proceed to step S1006.

[0110] Step S1008: Detect the time of the current switching cycle. That is, detect the switching frequency of the current switching cycle.

[0111] Step S1009: Stop sending control signals to switch S1.

[0112] Specifically, the control unit 550 continues to monitor the value of the current iR through input terminal 5. If the control unit 550 detects that the current iR is less than the set current ith, the PFC inductor stops sending the PWM S1 signal to the switch S1, keeping the switch S1 in the open state. If the control unit 550 detects that the current iR is not less than the set current ith, the control unit 550 continues to monitor the current iR. R .

[0113] After the control unit 550 detects that the current iR is less than the set current ith, it obtains the time of the current switching cycle. In the next switching cycle, the control unit 550 can compare whether the time of the current switching cycle is less than the set switching time, determine whether the switching frequency of the current switching cycle meets the maximum switching frequency limit, and determine whether to delay the next switching cycle by a set threshold time before sending a PWM S1 signal to the switch S1. The set threshold time is the difference between the time of the current switching cycle and the set switching time. Preferably, the set threshold time is generally greater than or equal to the difference between the time of the current switching cycle and the set switching time.

[0114] Step S1010: Determine the input voltage V AC Is it greater than the output voltage V? OUT Half of it. If yes, proceed to step S1013; otherwise, proceed to step S1011.

[0115] Specifically, when the control unit 550 determines that the totem-pole PFC circuit 510 has entered the DCM operating mode, since the switching frequency of the previous switching cycle of the totem-pole PFC circuit 510 is greater than the maximum switching frequency, it will not send a PWM S1 signal to switch S1, keeping switch S1 in the off state. At this time, the totem-pole PFC circuit 510 enters LC resonance, and the current iL flowing through the PFC inductor L discharges in the forward direction. The control unit 550 determines the current switching cycle T based on the charging and discharging time Ton + Toff of the PFC inductor L. If the control unit 550 determines that the time T of the current switching cycle is greater than or equal to the time Tmin for the PFC inductor L to complete one full charge and discharge cycle under the maximum switching frequency limit, it needs to determine the input voltage V. AC Is it greater than the output voltage V? OUT Half of the value is used, and different methods are employed to achieve zero-voltage switching of switch S2 based on different results.

[0116] Step S1011, detect the voltage V at node DT. DT The value.

[0117] Step S1012, determine voltage V DT Whether it crosses zero. That is, the voltage V. DT Is it less than zero? If yes, proceed to step S1001; otherwise, proceed to step S1011.

[0118] Specifically, when V AC <0.5V OUT At that time, the voltage V at node SW1 SW1 Valley value 2V AC -V OUT It will be below 0V. Control unit 550 receives the voltage V at node DT. DT The voltage V at node DT DT Equal to the voltage V at node SW1 SW1 When the voltage V at node SW1 SW1 When the voltage oscillates to 0V, the control unit 550 detects the voltage V at node DT. DT The voltage V at node DT is determined by the change from a negative value to 0V. DT Positive zero crossing. Control unit 550 sends a PWM S2 signal to switch S2, causing switch S2 to return to the conducting state. The totem-pole PFC circuit 510 enters the next switching cycle, achieving zero-voltage turn-on of switch S2. When the voltage V at node SW1... SW1 If the voltage does not oscillate to 0V, the control unit 550 continues to monitor the voltage V at node DT. DT .

[0119] Step S1013, detect the voltage V at node DT. DT The value.

[0120] Step S1014, determine voltage V DT Does it cross zero? That is, the voltage V DT Is it greater than zero? If yes, proceed to step S1015; otherwise, proceed to step S1013.

[0121] Step S1015: Send a control signal to switch S1.

[0122] Specifically, when V AC >0.5V OUT At that time, the voltage V at node SW1 SW1 Valley value 2V AC -V OUT It will be higher than 0V. When the voltage V at node SW1 SW1 When the voltage oscillates to 0V, the control unit 550 detects the voltage V at node DT. DT The voltage V at node DT is determined by the change from a positive value to 0V. DT The voltage crosses zero. At this time, the voltage V at node SW1 is zero. SW1 Oscillation to peak V OUT The control unit 550 detected the voltage V at node SW1. SW1 Reaching output voltage V OUT When the switch is in operation, a PWM signal is sent to switch S1 to put switch S1 in the on state, thus realizing the soft switching of switch S1.

[0123] Step S1016: Detect the value of the current iR flowing through resistor R.

[0124] Step S1017: Determine whether the current iR is less than the set current ith. If yes, proceed to step S1018; otherwise, proceed to step S1016.

[0125] Step S1017: Stop sending control signals to switch S1.

[0126] Specifically, the control unit 550 continues to monitor the value of the current iR through input terminal 5. If the control unit 550 detects that the current iR is less than the set current ith, it stops sending the PWM S1 signal to switch S1. The voltage V at node SW1... SW1 The LC oscillation process begins. At this time, the voltage V at node SW1... SW1 It can oscillate up to 0V. If the control unit 550 detects that the current iR is not less than the set current ith, the control unit 550 continues to detect the current i. R .

[0127] Step S1019, detect the voltage V at node DT. DT The value.

[0128] Step S1020, determine voltage V DT Does it cross zero? That is, the voltage V DT Is it greater than zero? If yes, proceed to step S1001; otherwise, proceed to step S1019.

[0129] Specifically, the control unit 550 receives the voltage V at node DT. DT The voltage V at node DT DT Equal to the voltage V at node SW1 SW1 When the voltage V at node SW1 SW1 When the voltage oscillates to 0V, the control unit 550 detects the voltage V at node DT. DT The voltage V at node DT is determined by the change from a negative value to 0V. DT Positive zero crossing. Control unit 550 sends a PWM S2 signal to switch S2, causing switch S2 to return to the conducting state. The totem-pole PFC circuit 510 enters the next switching cycle, achieving zero-voltage turn-on of switch S2. When the voltage V at node SW1... SW1 If the voltage does not oscillate to 0V, the control unit 550 continues to monitor the voltage V at node DT. DT .

[0130] This application provides an electronic device including a control device for a totem pole PFC circuit. The control device for the totem pole PFC circuit can be, for example... Figures 5-10 The electronic device includes the control device for the totem pole PFC circuit described in the corresponding protection scheme above. Since the electronic device includes the control device for the totem pole PFC circuit, it possesses all or at least some of the advantages of the control device for the totem pole PFC circuit. The electronic device can be a base station, charging pile, switch, electric vehicle, etc., and is not limited thereto in this application.

[0131] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions in the embodiments of this application.

Claims

1. A control method for a totem pole PFC circuit, characterized in that, The method is executed by the controller and includes: The electrical parameters of the PFC inductor in the totem pole PFC circuit are sampled; Based on the electrical parameters of the PFC inductor, the time of the previous switching cycle of the totem pole PFC circuit is determined, and the time of the previous switching cycle is determined based on the previous charging time and the previous discharging time of the PFC inductor. When the time of the previous switching cycle is less than the time of the set switching cycle, after a delay of a set threshold time, a control signal is sent to the first switch. The set threshold time is greater than or equal to the difference between the time of the set switching cycle and the previous switching cycle. The first switch is a switch that discharges the PFC inductor when the AC current at the input terminal of the totem pole PFC circuit is in the positive half-cycle. The control signal is used to discharge the bootstrap capacitor in the bootstrap circuit coupled to the switch.

2. The method according to claim 1, characterized in that, Determining the time of the previous switching cycle of the totem pole PFC circuit based on the electrical parameters of the PFC inductor includes: The current flowing through the PFC inductor is detected, and the electrical parameter is the current value; The time of the previous switching cycle is obtained by determining the time when the current value flowing through the PFC inductor decreased from the first threshold to zero and the time when the current value flowing through the PFC inductor increased from zero to the first threshold.

3. The method according to claim 1, characterized in that, The method further includes: The current flowing through the PFC inductor is detected, and the electrical parameter is the current value; When the current flowing through the PFC inductor is less than the second threshold, the time of the current switching cycle of the totem pole PFC circuit is determined.

4. The method according to any one of claims 1-3, characterized in that, The method further includes: Stop sending control signals to the first switch; The electrical parameters of the input and output terminals of the totem pole PFC circuit are sampled, and the output terminal is the port through which the totem pole PFC circuit outputs DC power to the outside. A control signal is sent to the second switch, which is a switch that charges the PFC inductor when the AC current at the input terminal of the totem pole PFC circuit is in the positive half-cycle.

5. The method according to claim 4, characterized in that, Sending a control signal to the second switch includes: When the voltage at the input terminal of the totem pole PFC circuit is not greater than half of the voltage at the output terminal of the totem pole PFC circuit, the input voltage of the detection circuit is detected. The input terminal of the detection circuit is electrically connected to the intermediate node between the first switch and the second switch connected in series, and is used to detect the voltage at the intermediate node. The input voltage of the detection circuit is the voltage value at the intermediate node. When the input voltage of the detection circuit crosses zero, a control signal is sent to the second switch.

6. The method according to claim 4, characterized in that, Sending a control signal to the second switch includes: When the voltage at the input terminal of the totem pole PFC circuit is greater than half of the voltage at the output terminal of the totem pole PFC circuit, the input voltage of the detection circuit is detected. The input terminal of the detection circuit is electrically connected to the intermediate node between the first switch and the second switch connected in series, and is used to detect the voltage at the intermediate node. The input voltage of the detection circuit is the voltage value at the intermediate node. When the input voltage of the detection circuit crosses zero, a control signal is sent to the first switch; Detect the current flowing through the PFC inductor; When the current flowing through the PFC inductor is determined to be less than the second threshold, the control signal sent to the first switch is stopped. When the input voltage of the detection circuit crosses zero, a control signal is sent to the second switch.

7. The method according to claim 1, characterized in that, Before determining the time of the previous switching cycle of the totem pole PFC circuit based on the electrical parameters of the PFC inductor, the method further includes: Send a control signal to the second switch, which is a switch that charges the PFC inductor when the AC power at the input terminal of the totem pole PFC circuit is in the positive half cycle; Detect the current flowing through the PFC inductor; When the current flowing through the PFC inductor is determined to be negative and crosses zero, the control signal sent to the second switch is stopped.

8. A control device for a totem pole PFC circuit, characterized in that, include: The totem pole PFC circuit, detection circuit, input voltage detection unit, output voltage detection unit, and control unit are all included. The detection circuit is used to output the electrical parameters of the PFC inductor of the totem pole PFC circuit to the control unit. The input voltage detection unit is used to output the AC voltage of the input terminal of the totem pole PFC circuit to the control unit; The output voltage detection unit is used to output the DC voltage of the output terminal of the totem pole PFC circuit to the control unit. The control unit is used to determine the time of the previous switching cycle of the totem pole PFC circuit based on the electrical parameters of the PFC inductor. The time of the previous switching cycle is determined based on the previous charging time and the previous discharging time of the PFC inductor. When the time of the previous switching cycle is less than the time of the set switching cycle, after a delay of a set threshold time, a control signal is sent to the first switch. The set threshold time is greater than or equal to the difference between the time of the set switching cycle and the previous switching cycle. The first switch is a switch that discharges the PFC inductor when the AC current at the input terminal of the totem pole PFC circuit is in the positive half-cycle. The control signal is used to discharge the bootstrap capacitor in the bootstrap circuit coupled to the switch.

9. The apparatus according to claim 8, characterized in that, The control unit is specifically configured to determine, based on the current value of the PFC inductor, the time when the previous current value decreased from a first threshold to zero and the time when the previous current value increased from zero to the first threshold, thereby obtaining the time of the previous switching cycle.

10. The apparatus according to claim 8, characterized in that, The control unit is further configured to determine the current switching cycle time of the totem pole PFC circuit based on the current value of the PFC inductor, when the current value flowing through the PFC inductor is less than a second threshold.

11. The apparatus according to any one of claims 8-10, characterized in that, The control unit is also configured to stop sending control signals to the first switch; Based on the voltage input by the input voltage detection unit and the voltage input by the output voltage detection unit, a control signal is sent to the second switch, which is a switch that charges the PFC inductor when the AC current at the input terminal of the totem pole PFC circuit is in the positive half-cycle.

12. The apparatus according to claim 11, characterized in that, The control unit is specifically used to detect the input voltage of the detection circuit when the voltage at the input terminal of the totem pole PFC circuit is not greater than half of the voltage at the output terminal of the totem pole PFC circuit. The input terminal of the detection circuit is electrically connected to the intermediate node between the first switch and the second switch connected in series, and is used to detect the voltage at the intermediate node. The input voltage of the detection circuit is the voltage value at the intermediate node. When the input voltage of the detection circuit crosses zero, a control signal is sent to the second switch.

13. The apparatus according to claim 11, characterized in that, The control unit is specifically used to detect the input voltage of the detection circuit when the voltage at the input terminal of the totem pole PFC circuit is greater than half of the voltage at the output terminal of the totem pole PFC circuit. The input terminal of the detection circuit is electrically connected to the intermediate node between the first switch and the second switch connected in series, and is used to detect the voltage at the intermediate node. The input voltage of the detection circuit is the voltage value at the intermediate node. When the input voltage of the detection circuit crosses zero, a control signal is sent to the first switch; Detect the current flowing through the PFC inductor; When the current flowing through the PFC inductor is determined to be less than the second threshold, the control signal sent to the first switch is stopped. When the input voltage of the detection circuit crosses zero, a control signal is sent to the second switch.

14. The apparatus according to claim 8, characterized in that, The control unit is also used to send a control signal to a second switch, which is a switch that charges the PFC inductor when the AC current at the input terminal of the totem pole PFC circuit is in the positive half-cycle. Detect the current flowing through the PFC inductor; When the current flowing through the PFC inductor is determined to be negative and crosses zero, the control signal sent to the second switch is stopped.

15. An electronic device, characterized in that, include: The control device for the totem pole PFC circuit as described in any one of claims 8-14.

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