An LLC integrated PFC circuit with a wide voltage regulation range

Abstract

The present invention discloses an LLC integrated PFC circuit with a wide voltage regulation range. The circuit comprises a PFC circuit cascaded with an LLC circuit by reusing part of the LLC circuit; the reusing part of the LLC circuit comprises a secondary rectifier bridge of the LLC circuit and a leakage inductance of a high-frequency transformer of the LLC circuit; the secondary rectifier bridge of the LLC circuit serves as a PFC freewheeling diode in the PFC circuit; the leakage inductance of the high-frequency transformer of the LLC circuit serves as an energy storage inductor in the PFC circuit; the LLC integrated PFC circuit adopts any one of a Boost phase-controlled rectifier continuous voltage regulation control method, a phase-controlled voltage-doubling rectifier control method, and a hybrid voltage regulation control method to achieve an extension of the upper limit of the voltage transformation range in a soft switching state.

Description

Technical Field

[0001] The present invention belongs to the technical field of power supplies, and in particular relates to an LLC integrated PFC circuit with a wide voltage regulation range. Background Art

[0002] The LLC is a robust, highly efficient, isolated DC / DC converter, but it has a narrow voltage regulation range. In applications requiring a wide voltage regulation range, the LLC is often cascaded with other non-isolated DC / DC converters to extend this range, such as by cascading an H-type buck-boost in front of the LLC. However, this approach increases the number of components, reduces system efficiency, and increases hardware costs. Summary of the Invention

[0003] Purpose of the invention: In order to reduce hardware costs and improve power conversion efficiency, the present invention proposes an LLC integrated PFC circuit with a wide voltage regulation range.

[0004] Technical solution: An LLC integrated PFC circuit with a wide voltage regulation range includes an LLC circuit and a PFC circuit. The PFC circuit is cascaded with the LLC circuit by reusing part of the LLC circuit; the reused part includes the LLC circuit's secondary rectifier bridge and the LLC circuit's high-frequency transformer's leakage inductance. The LLC circuit's secondary rectifier bridge serves as a PFC freewheeling diode in the PFC circuit; and the LLC circuit's high-frequency transformer's leakage inductance serves as an energy storage inductor in the PFC circuit.

[0005] The PFC circuit further includes a first docking switch device, a second docking switch device, a first voltage-dividing capacitor, a second voltage-dividing capacitor, a DC output positive terminal, and a DC output negative terminal; the DC output positive terminal is connected to the positive busbar of the secondary rectifier bridge, the DC output negative terminal is connected to the negative busbar of the secondary rectifier bridge, the AC port of the secondary rectifier bridge is connected to the secondary winding of the high-frequency transformer, and is connected to the connection point of the first voltage-dividing capacitor and the second voltage-dividing capacitor via the first docking switch device and the second docking switch device, respectively;

[0006] The LLC integrated PFC circuit adopts any one of the Boost phase-controlled rectifier continuous voltage regulation control method, the phase-controlled voltage doubler rectifier control method and the hybrid voltage regulation control method to achieve the expansion of the upper limit of the voltage transformation range in the soft switching state;

[0007] The Boost phase-controlled rectifier continuous voltage regulation control method includes:

[0008] Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state;

[0009] When the phase angle is 0, the first and second docking switch devices are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches a set value A1, the first and second docking switch devices are turned off, the first and second voltage-dividing capacitors are charged, and the voltage increases; wherein A1<pi; when the phase angle is pi, the first and second docking switch devices are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches a set value A1+pi, the first and second docking switch devices are turned off, the first and second voltage-dividing capacitors are charged, and the voltage increases;

[0010] The phase-controlled voltage-doubling rectification control method includes:

[0011] Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state;

[0012] When the phase angle is 0, the first docking switch device is turned on to charge the second voltage-dividing capacitor; when the phase angle reaches a set value A1, the first docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor; wherein A1 < pi; when the phase angle is pi, the first docking switch device is turned on to charge the first voltage-dividing capacitor; when the phase angle reaches a set value A1 + pi, the first docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor;

[0013] The hybrid voltage regulation control method includes:

[0014] Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state;

[0015] When the phase angle is 0, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1, the second docking switch device is turned off, and the second voltage-dividing capacitor is charged; when the phase angle is pi, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1+pi, the second docking switch device is turned off, and the first voltage-dividing capacitor is charged.

[0016] Furthermore, the control steps in the phase-controlled voltage doubler rectification control method can be replaced by:

[0017] Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state;

[0018] When the phase angle is 0, the second docking switch device is turned on to charge the first voltage-dividing capacitor; when the phase angle reaches the set value A1, the second docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor; wherein A1<pi; when the phase angle is pi, the second docking switch device is turned on to charge the second voltage-dividing capacitor; when the phase angle reaches the set value A1+pi, the second docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor.

[0019] Furthermore, the control steps in the hybrid voltage regulation control method can be replaced by:

[0020] Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state;

[0021] When the phase angle is 0, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1, the first docking switch device is turned off, and the first voltage-dividing capacitor is charged; when the phase angle is pi, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1+pi, the first docking switch device is turned off, and the second voltage-dividing capacitor is charged.

[0022] Furthermore, the positive busbar and negative busbar of the active bridge are connected to the DC input positive terminal and the DC input negative terminal respectively; the AC port of the active bridge is connected to the primary side of the high-frequency transformer and is connected in series with a resonant capacitor and a resonant inductor; the active bridge is composed of a first switching device, a second switching device, a third switching device and a fourth switching device, the DC input positive terminal is connected to the positive electrode of the first switching device and the positive electrode of the third switching device; the negative electrode of the first switching device is connected to the positive electrode of the resonant capacitor and the positive electrode of the second switching device; the negative electrode of the third switching device is connected to the positive electrode of the resonant inductor and the positive electrode of the fourth switching device; the DC input negative terminal is connected to the negative electrodes of the second switching device and the fourth switching device;

[0023] The method of maintaining the operating frequency of the LLC circuit unchanged and controlling all switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state includes the following steps:

[0024] Connect the DC input positive terminal and DC input negative terminal to the positive and negative poles of the DC power supply respectively;

[0025] Among the switching devices that constitute the active bridge, the first switching device and the fourth switching device are turned on or off simultaneously, and the second switching device and the third switching device are turned on or off simultaneously. The first switching device and the fourth switching device are alternately turned on and off with the second switching device and the third switching device, and the duty cycle is maintained at 50%. The switching frequency is F1. The resonant frequency of the resonant circuit formed by the resonant capacitor and the resonant inductor is F2. By controlling F1 to be less than or equal to F2, it is ensured that the first switching device, the second switching device, the third switching device, and the fourth switching device operate in a soft switching state.

[0026] Furthermore, the first docking switch device and the second docking switch device are both power electronic switches composed of two power electronic switches connected in reverse series and have forward and reverse bidirectional shutoff capabilities.

[0027] Furthermore, the secondary rectifier bridge is composed of a first diode, a second diode, a third diode and a fourth diode; the DC output positive terminal is connected to the positive electrode of the first voltage-dividing capacitor, the negative electrode of the first diode and the negative electrode of the third diode; the positive electrode of the first diode is connected to the positive electrode of the secondary winding of the high-frequency transformer, the negative electrode of the second diode and the positive electrode of the first docking switch device; the positive electrode of the third diode is connected to the negative electrode of the secondary winding of the high-frequency transformer, the negative electrode of the fourth diode and the negative electrode of the second docking switch device; the positive electrode of the second diode and the positive electrode of the fourth diode are connected to the negative electrode of the second voltage-dividing capacitor and the DC output negative terminal; the negative electrode of the first docking switch device is connected to the positive electrode of the second docking switch device, the negative electrode of the first voltage-dividing capacitor and the positive electrode of the second voltage-dividing capacitor.

[0028] Beneficial Effects: This invention proposes a novel LLC cascade PFC topology that reuses the leakage inductance of a high-frequency transformer and a rectifier bridge. This LLC-type isolated DC / DC converter with a cascade transformer topology reduces hardware costs and improves power conversion efficiency. Compared with existing technologies, this invention has the following advantages:

[0029] (1) The LLC circuit and the PFC circuit reuse the first diode, the second diode, the third diode, and the fourth diode. These diodes constitute the LLC secondary rectifier bridge and serve as PFC freewheeling diodes, reducing the number of power devices in the circuit topology, lowering hardware costs and device losses, and improving power conversion efficiency.

[0030] (2) The PFC circuit reuses the leakage inductance of the LLC high-frequency transformer as the energy storage inductor, which reduces the circuit topology hardware cost, reduces the power devices in the circuit topology, reduces the hardware cost and device loss, and improves the power conversion efficiency;

[0031] (3) The input side of the PFC circuit is the high-frequency AC output of the high-frequency transformer, which is output after PFC rectification and boosting, expanding the upper limit of the topology voltage regulation;

[0032] (4) Based on the new circuit topology, a Boost phase-controlled rectifier continuous voltage regulation control method is proposed to keep the LLC operating frequency unchanged. All devices in the LLC active bridge operate in the soft switching state, and some fully controlled devices in the PFC circuit operate in the "zero voltage conduction" state. This control method expands the upper limit of the voltage transformation range under the soft switching state.

[0033] (5) Based on the new circuit topology, a phase-controlled voltage-doubling rectifier control method is proposed to keep the LLC operating frequency unchanged. All devices in the LLC active bridge operate in the soft switching state. Some fully controlled devices in the PFC circuit operate in the "zero voltage turn-on" state. Under some working conditions, they can also operate in the "zero current turn-off" state. This control method expands the upper limit of the voltage transformation range in the soft switching state without affecting the LLC resonant current distortion. The output voltage is increased by up to 2 times.

[0034] (6) Based on the new circuit topology, a hybrid voltage regulation control method is proposed to keep the LLC operating frequency unchanged. All devices in the LLC active bridge operate in the soft switching state, and some fully controlled devices in the PFC circuit operate in the "zero voltage conduction" state. This control method further expands the upper limit of the voltage transformation range under the soft switching state. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a topological diagram of the present invention;

[0036] Figure 2 This is a schematic diagram of the transformer secondary current flow when the phase angle is 0 under the Boost phase-controlled rectifier continuous voltage regulation control method;

[0037] Figure 3 The figure shows the secondary current flow of the transformer under the Boost phase-controlled rectifier continuous voltage regulation control method when the phase angle reaches the set value A1 (A1 is less than pi);

[0038] Figure 4 This is a schematic diagram of the secondary current flow of the transformer under the Boost phase-controlled rectifier continuous voltage regulation control method when the phase angle is pi;

[0039] Figure 5 The figure shows the secondary current flow of the transformer under the Boost phase-controlled rectifier continuous voltage regulation control method when the phase angle reaches the set value A1+pi (A1 is less than pi);

[0040] Figure 6 Schematic diagram of the secondary current flow of the high-frequency transformer under the phase-controlled voltage-doubling rectification control method when the phase angle is 0 and the first connecting switch device is turned on;

[0041] Figure 7Schematic diagram of the secondary current flow of the high-frequency transformer under the phase-controlled voltage-doubling rectification control method when the phase angle reaches the set value A1 (A1 is less than pi) and the first connecting switch device is turned off;

[0042] Figure 8 Schematic diagram of the secondary current flow of the transformer when the phase angle is pi and the first connecting switch device is turned on under the phase-controlled voltage doubler rectification control method;

[0043] Figure 9 Schematic diagram of the transformer secondary current flow when the first connecting switch device is turned off when the phase angle reaches the set value A1+pi (A1 is less than pi) under the phase-controlled voltage doubling rectification control method;

[0044] Figure 10 Schematic diagram of the current flow direction of the secondary side of the transformer when the phase angle is 0 and the second connecting switch device is turned on under the phase-controlled voltage doubling rectification control method;

[0045] Figure 11 Schematic diagram of the transformer secondary current flow when the phase angle reaches the set value A1 (A1 is less than pi) and the second connecting switch device is turned off under the phase-controlled voltage doubler rectification control method;

[0046] Figure 12 Schematic diagram of the current flow direction of the secondary side of the transformer when the second connecting switch device is turned on under the phase-controlled voltage doubling rectification control method when the phase angle is pi;

[0047] Figure 13 Schematic diagram of the transformer secondary current flow when the phase angle reaches the set value A1+pi (A1 is less than pi) and the second connecting switch device is turned off under the phase-controlled voltage doubler rectification control method;

[0048] Figure 14 Schematic diagram of the secondary current flow of the transformer under the hybrid voltage regulation control method when the phase angle is 0 and the first and second docking switch devices are turned on;

[0049] Figure 15 Schematic diagram of the transformer secondary current flow when the phase angle reaches the set value A1 (A1 is less than pi) and the second docking switch device is turned off under the hybrid voltage regulation control method;

[0050] Figure 16 Schematic diagram of the secondary current flow of the transformer when the first and second docking switching devices are turned on under the hybrid voltage regulation control method, when the phase angle is pi;

[0051] Figure 17 Schematic diagram of the transformer secondary current flow when the phase angle reaches the set value A1+pi (A1 is less than pi) and the second connecting switch device is turned off under the hybrid voltage regulation control method;

[0052] Figure 18 Schematic diagram of the secondary current flow of the transformer under the hybrid voltage regulation control method when the phase angle is 0 and the first and second docking switch devices are turned on;

[0053] Figure 19 Schematic diagram of the secondary current flow of the transformer under the hybrid voltage regulation control method when the phase angle reaches the set value A1 (A1 is less than pi) and the first connecting switch device is turned off;

[0054] Figure 20 Schematic diagram of the secondary current flow of the transformer when the first and second docking switching devices are turned on under the hybrid voltage regulation control method, when the phase angle is pi;

[0055] Figure 21 Schematic diagram of the transformer secondary current flow when the first connecting switch device is turned off when the phase angle reaches the set value A1+pi (A1 is less than pi) under the hybrid voltage regulation control method;

[0056] Figure 22 The output voltage diagram is as follows: the input voltage is 750Vdc, the load power is 1kW, and the phase angle is 0.05×pi under the Boost phase-controlled rectifier continuous voltage regulation control method;

[0057] Figure 23 Schematic diagram of the driving voltage of the first switching device and the conduction current of the first switching device when the input voltage is 750Vdc, the load power is 1kW, and the phase angle is 0.05×pi under the Boost phase-controlled rectifier continuous voltage regulation control method;

[0058] Figure 24 The output voltage diagram is shown when the input voltage is 750Vdc, the load power is 1kW, and the phase angle is 0.05×pi under the hybrid voltage regulation control method;

[0059] Figure 25 Schematic diagram of the driving voltage and the on-current of the first switching device when the input voltage is 750 Vdc, the load power is 1 kW, and the phase angle is 0.05×pi under the hybrid voltage regulation control method;

[0060] Figure 26 The output voltage diagram is as follows: when the input voltage is 750Vdc, the load power is 15kW, and the phase angle is 0.05×pi under the Boost phase-controlled rectifier continuous voltage regulation control method;

[0061] Figure 27 Schematic diagram of the driving voltage and the on-current of the first switching device when the input voltage is 750Vdc, the load power is 15kW, and the phase angle is 0.05×pi under the Boost phase-controlled rectifier continuous voltage regulation control method;

[0062] Figure 28 The output voltage diagram is shown when the input voltage is 750Vdc, the load power is 15kW, and the phase angle is 0.05×pi under the hybrid voltage regulation control method;

[0063] Figure 29 Schematic diagram of the driving voltage and the on-current of the first switching device when the input voltage is 750 Vdc, the load power is 15 kW, and the phase angle is 0.05×pi under the hybrid voltage regulation control method;

[0064] Figure 30 The following is a diagram showing the relationship between load power, output voltage, and phase angle when the input voltage is 750Vdc and the Boost phase-controlled rectifier continuous voltage regulation method is used.

[0065] Figure 31 This is a schematic diagram of the corresponding relationship between load power, output voltage and phase angle when the input voltage is 750Vdc and the hybrid voltage regulation control method is adopted. DETAILED DESCRIPTION

[0066] The technical solution of the present invention will now be further described with reference to the accompanying drawings.

[0067] The present invention proposes an LLC integrated PFC topology with a wide voltage regulation range. Figure 1 As shown, it includes: a DC input positive terminal 1601, a DC input negative terminal 1602, an active bridge, a resonant capacitor 1201, a high-frequency transformer 1202, a resonant inductor 1203, a rectifier bridge, a first docking switch device 1401, a second docking switch device 1402, a first voltage-dividing capacitor 1501, a second voltage-dividing capacitor 1502, a DC output positive terminal 1603 and a DC output negative terminal 1604.

[0068] The DC input positive terminal 1601 is connected to the positive busbar of the active bridge, and the DC input negative terminal 1602 is connected to the negative busbar of the active bridge. The AC port of the active bridge is connected to the primary side of the high-frequency transformer 1202 and is connected in series with the resonant capacitor 1201 and the resonant inductor 1203. The active bridge is composed of a first switching device 1101, a second switching device 1102, a third switching device 1103, and a fourth switching device 1104. These switching devices are preferably IGBTs, but can also be fully controlled power electronic switching devices such as MOSFETs and IGCTs. That is, the DC input positive terminal 1601 is connected to the positive electrodes of the first switching device 1101 and the third switching device 1103; the negative electrode of the first switching device 1101 is connected to the positive electrode of the resonant capacitor 1201 and the positive electrode of the second switching device 1102; the negative electrode of the third switching device 1103 is connected to the positive electrode of the resonant inductor 1203 and the positive electrode of the fourth switching device 1104; the negative electrode of the resonant capacitor 1201 is connected to the positive electrode of the primary winding of the high-frequency transformer 1202; the negative electrode of the resonant inductor 1203 is connected to the negative electrode of the primary winding of the high-frequency transformer 1202; the DC input negative terminal 1602 is connected to the negative electrodes of the second switching device 1102 and the fourth switching device 1104; the negative electrode of the resonant capacitor 1201 is connected to the positive electrode of the primary winding of the high-frequency transformer 1202.

[0069] The DC output positive terminal 1603 is connected to the positive busbar of the rectifier bridge, and the DC output negative terminal 1604 is connected to the negative busbar of the rectifier bridge. The AC port of the rectifier bridge is connected to the secondary winding of the high-frequency transformer 1202, and is connected to the connection point of the first and second voltage-dividing capacitors 1501 and 1502 via the first and second docking switch devices 1401 and 1402, respectively. The rectifier bridge is composed of a first diode 1301, a second diode 1302, a third diode 1303, and a fourth diode 1304. That is, the DC output positive terminal 1603 is connected to the positive electrode of the first voltage-dividing capacitor 1501, the negative electrode of the first diode 1301, and the negative electrode of the third diode 1303; the positive electrode of the first diode 1301 is connected to the positive electrode of the secondary winding of the high-frequency transformer 1202, the negative electrode of the second diode 1302, and the positive electrode of the first docking switch device 1401; the positive electrode of the third diode 1303 is connected to the negative electrode of the secondary winding of the high-frequency transformer 1202, the negative electrode of the fourth diode 1304, and the negative electrode of the second docking switch device 1402; the positive electrodes of the second diode 1302 and the fourth diode 1304 are connected to the negative electrode of the second voltage-dividing capacitor 1502 and the DC output negative terminal 1604; and the negative electrode of the first docking switch device 1401 is connected to the positive electrode of the second docking switch device 1402, the negative electrode of the first voltage-dividing capacitor 1501, and the positive electrode of the second voltage-dividing capacitor 1502. The first docking switch device 1401 and the second docking switch device 1402 are power electronic switches composed of two reverse-connected power electronic switches in series and have forward and reverse bidirectional turn-off capabilities, and are preferably MOSFETs.

[0070] The topology design has an input rated voltage of U and a rated power of P. The withstand voltage of the first switching device 1101, the second switching device 1102, the third switching device 1103, and the fourth switching device 1104, as well as the first diode 1301, the second diode 1302, the third diode 1303, and the fourth diode 1304 is not less than the rated voltage U, and preferably is not less than 1.5 times the rated voltage U. The maximum average current of the first switching device 1101, the second switching device 1102, the third switching device 1103, and the fourth switching device 1104, as well as the first diode 1301, the second diode 1302, the third diode 1303, and the fourth diode 1304 is not less than 0.5 times the ratio of P / U, and preferably is not less than 0.75 times the ratio of P / U. The withstand voltage of the switch devices connected to the first docking switch device 1401 and the second docking switch device 1402 is not less than 0.5 times the rated voltage U, and preferably not less than 0.75 times the rated voltage U; the maximum average current of the switch devices connected to the first docking switch device 1401 and the second docking switch device 1402 is not less than 0.5 times P / U, and preferably not less than 0.75 times P / U.

[0071] The present invention also proposes a control method for the above topological structure.

[0072] Connect the DC input positive terminal 1601 and the DC input negative terminal 1602 to the positive and negative terminals of the DC power supply, respectively. Among the switching devices forming the active bridge, the first switching device 1101 and the fourth switching device 1104 are simultaneously turned on or off, and the second switching device 1102 and the third switching device 1103 are simultaneously turned on or off. The first switching device 1101 and the fourth switching device 1104 are alternately turned on and off with the second switching device 1102 and the third switching device 1103, maintaining a duty cycle of 50% and a switching frequency of F1. The resonant circuit formed by the resonant capacitor 1201 and the resonant inductor 1203 has a resonant frequency of F2, which is less than or equal to F2 to ensure that the first switching device 1101, the second switching device 1102, the third switching device 1103, and the fourth switching device 1104 operate in a soft switching state.

[0073] Control method 1: Boost phase-controlled rectification continuous voltage regulation control method

[0074] (1) Figure 2 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the negative half cycle to the positive half cycle, that is, when the phase angle is 0, the first docking switch device 1401 and the second docking switch device 1402 are turned on, so that the secondary winding of the high-frequency transformer 1202 is short-circuited;

[0075] (2) Figure 3 As shown, when the phase angle reaches the set value A1 (A1 is less than pi), the first docking switch device 1401 and the second docking switch device 1402 are turned off, and the current charges the first voltage-dividing capacitor 1501 and the second voltage-dividing capacitor 1502 through the first diode 1301 and the diode 1304, and the voltage increases;

[0076] (3) Figure 4 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the positive half cycle to the negative half cycle, that is, when the phase angle is pi, the first docking switch device 1401 and the second docking switch device 1402 are turned on, so that the secondary winding of the high-frequency transformer 1202 is short-circuited;

[0077] (4) Figure 5 As shown, when the phase angle reaches the set value A1+pi (A1 is less than pi), the first docking switch device 1401 and the second docking switch device 1402 are turned off, and the current charges the first voltage-dividing capacitor 1501 and the second voltage-dividing capacitor 1502 through the second diode 1302 and the third diode 1303, and the voltage increases.

[0078] This control method does not affect LLC soft-switching control, but the PFC part can only achieve zero-voltage turn-on, not zero-current turn-off. Therefore, it is preferable to use MOSFETs for the PFC part. This control method will cause the LLC part resonant current to generate more significant harmonics under light load conditions.

[0079] Control method 2: Phase-controlled voltage doubler rectification control method

[0080] (1) Figure 6 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the negative half cycle to the positive half cycle, that is, when the phase angle is 0, the first docking switch device 1401 is turned on, and the current charges the second voltage-dividing capacitor 1502 through the first docking switch device 1401 and the fourth diode 1304;

[0081] (2) Figure 7 As shown, when the phase angle reaches the set value A1 (A1 is less than pi), the first docking switch device 1401 is turned off, and the current charges the first voltage-dividing capacitor 1501 and the second voltage-dividing capacitor 1502 through the first diode 1301 and the fourth diode 1304;

[0082] (3) Figure 8 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the positive half cycle to the negative half cycle, that is, when the phase angle is pi, the first docking switch device 1401 is turned on, and the current charges the first voltage-dividing capacitor 1501 through the third diode 1303 and the first docking switch device 1401;

[0083] (4) Figure 9 As shown, when the phase angle reaches the set value A1+pi (A1 is less than pi), the first docking switch device 1401 is turned off, and the current charges the first voltage-dividing capacitor 1501 and the second voltage-dividing capacitor 1502 through the second diode 1302 and the third diode 1303.

[0084] or:

[0085] (1) Figure 10 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the negative half cycle to the positive half cycle, that is, when the phase angle is 0, the second docking switch device 1402 is turned on, and the current charges the first voltage-dividing capacitor 1501 through the first diode 1301 and the second docking switch device 1402;

[0086] (2) Figure 11 As shown, when the phase angle reaches the set value A1 (A1 is less than pi), the second docking switch device 1402 is turned off, and the current charges the first voltage-dividing capacitor 1501 and the second voltage-dividing capacitor 1502 through the first diode 1301 and the fourth diode 1304;

[0087] (3) Figure 12 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the positive half cycle to the negative half cycle, that is, when the phase angle is pi, the second docking switch device 1402 is turned on, and the current charges the second voltage-dividing capacitor 1502 through the second diode 1302 and the second docking switch device 1402;

[0088] (4) Figure 13 As shown, when the phase angle reaches the set value A1+pi (A1 is less than pi), the second docking switch device 1402 is turned off, and the current charges the first voltage-dividing capacitor 1501 and the second voltage-dividing capacitor 1502 through the second diode 1302 and the third diode 1303.

[0089] Under this control method, the PFC circuit has little impact on the LLC circuit, and the LLC resonant current distortion is small. However, the maximum boost ratio of the circuit under this control method does not exceed 2. When the phase angle setting values ​​are pi and 2×pi, the PFC boost ratio is 2, and at this moment, the PFC fully controlled devices 1401 and 1402 can simultaneously achieve "zero voltage turn-on" and "zero current turn-off."

[0090] Control method 3: Hybrid voltage regulation control method:

[0091] (1) Figure 14 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the negative half cycle to the positive half cycle, that is, when the phase angle is 0, the first docking switch device 1401 and the second docking switch device 1402 are turned on, so that the secondary winding of the high-frequency transformer 1202 is short-circuited;

[0092] (2) Figure 15 As shown, when the phase angle reaches the set value A1 (A1 is less than pi), the second docking switch device 1402 is turned off, and the current charges the second voltage-dividing capacitor 1502 through the first docking switch device 1401 and the fourth diode 1304;

[0093] (3) Figure 16 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the positive half cycle to the negative half cycle, that is, when the phase angle is pi, the first docking switch device 1401 and the second docking switch device 1402 are turned on, so that the secondary winding of the high-frequency transformer 1202 is short-circuited;

[0094] (4) Figure 17 As shown, when the phase angle reaches the set value A1+pi (A1 is less than pi), the second docking switch device 1402 is turned off, and the current charges the first voltage-dividing capacitor 1501 through the first docking switch device 1401 and the third diode 1303;

[0095] or

[0096] (1) Figure 18 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the negative half cycle to the positive half cycle, that is, when the phase angle is 0, the first docking switch device 1401 and the second docking switch device 1402 are turned on, so that the secondary winding of the high-frequency transformer 1202 is short-circuited;

[0097] (2) Figure 19 As shown, when the phase angle reaches the set value A1 (A1 is less than pi), the first docking switch device 1401 is turned off, and the current charges the first voltage-dividing capacitor 1501 through the second docking switch device 1402 and the first diode 1301;

[0098] (3) Figure 20 As shown, when the secondary current of the high-frequency transformer 1202 passes through the zero point from the positive half cycle to the negative half cycle, that is, when the phase angle is pi, the first docking switch device 1401 and the second docking switch device 1402 are turned on, so that the secondary winding of the high-frequency transformer 1202 is short-circuited;

[0099] (4) Figure 21 As shown, when the phase angle reaches the set value A1+pi (A1 is less than pi), the first docking switch device 1401 is turned off, and the current charges the second voltage-dividing capacitor 1502 through the second docking switch device 1402 and the second diode 1302.

[0100] The technical solution of the present invention is now further described in conjunction with an embodiment.

[0101] The following components are used to build the topology structure proposed in the present invention: the first switch device 1101, the second switch device 1102, the third switch device 1103 and the fourth switch device 1104 are IGBTs with a rated voltage of 1200V and a maximum average current of 200A; the resonant capacitor 1201 is 1.32×10 -7 F film capacitor; resonant inductor 1203 select 4.7×10 -6 The high-frequency inductor of H; the rated power of high-frequency transformer 1202 is 15kW, the rated frequency is 20kHz, the insulation voltage is 1000V, the primary-secondary turns ratio is 3:1, and the excitation resistance is 1.125×10 5 ohm, the excitation inductance is 2×10 -3 H; the first diode 1301, the second diode 1302, the third diode 1303 and the fourth diode 1304 are selected to have a rated voltage of 1200V and a maximum average current of 600A; the switching devices in the first docking switch device 1401 and the second docking switch device 1402 are selected to be MOSFETs with a rated voltage of 600V and a maximum average current of 400A; the first voltage-dividing capacitor 1501 and the second voltage-dividing capacitor 1502 are selected to have a voltage of 1200V and a maximum average current of 2.2×10-3 F electrolytic capacitor.

[0102] The rated input voltage is 750V, and the output voltage range is 250V to 1000V. Boost phase-controlled rectification continuous voltage regulation control method is adopted in the output voltage regulation range of 250V to 500V, and a hybrid voltage regulation control method is adopted in the range of 500V to 1000V.

[0103] When the input voltage is 750Vdc, the load power is 1kW, and the phase angle is 0.05×pi under the Boost phase-controlled rectifier continuous voltage regulation control method, the output voltage (i.e., the voltage between the DC output positive terminal 1603 and the DC output negative terminal 1604) is as follows: Figure 22 As shown, the driving voltage of the first switching device 1101 and the conduction current of the first switching device 1101 are as follows: Figure 23 shown.

[0104] When the input voltage is 750Vdc, the load power is 1kW, and the phase angle is 0.05×pi under the hybrid voltage regulation control method, the output voltage is as follows: Figure 24 As shown, the driving voltage of the first switching device 1101 and the conduction current of the first switching device 1101 are as follows: Figure 25 shown.

[0105] When the input voltage is 750Vdc, the load power is 15kW, and the phase angle is 0.05×pi under the Boost phase-controlled rectifier continuous voltage regulation control method, the output voltage is as follows: Figure 26 As shown, the driving voltage of the first switching device 1101 and the conduction current of the first switching device 1101 are as follows: Figure 27 shown.

[0106] When the input voltage is 750Vdc, the load power is 15kW, and the phase angle is 0.05×pi under the hybrid voltage regulation control method, the output voltage is as follows: Figure 28 As shown, the driving voltage of the first switching device 1101 and the conduction current of the first switching device 1101 are as follows: Figure 29 shown.

[0107] The input voltage is 750Vdc. When using Boost phase-controlled rectifier continuous voltage regulation control method, the corresponding relationship between load power, output voltage and phase angle is as follows: Figure 30 shown.

[0108] The input voltage is 750Vdc. When the hybrid voltage regulation control method is used, the corresponding relationship between load power, output voltage and phase angle is as follows: Figure 31 shown.

Claims

1. An LLC integrated PFC circuit with a wide voltage regulation range, characterized by: The circuit comprises an LLC circuit and a PFC circuit, wherein the PFC circuit is cascaded with the LLC circuit by reusing part of the LLC circuit; the reusing part of the LLC circuit comprises a secondary rectifier bridge of the LLC circuit and a leakage inductance of a high-frequency transformer of the LLC circuit; wherein the secondary rectifier bridge of the LLC circuit serves as a PFC freewheeling diode in the PFC circuit; wherein the leakage inductance of the high-frequency transformer of the LLC circuit serves as an energy storage inductor in the PFC circuit; The PFC circuit further includes a first docking switch device, a second docking switch device, a first voltage-dividing capacitor, a second voltage-dividing capacitor, a DC output positive terminal, and a DC output negative terminal; the DC output positive terminal is connected to the positive busbar of the secondary rectifier bridge, the DC output negative terminal is connected to the negative busbar of the secondary rectifier bridge, the AC port of the secondary rectifier bridge is connected to the secondary winding of the high-frequency transformer, and is connected to the connection point of the first voltage-dividing capacitor and the second voltage-dividing capacitor via the first docking switch device and the second docking switch device, respectively; One end of the first voltage-dividing capacitor is connected to the DC output positive terminal, the other end of the first voltage-dividing capacitor is connected to one end of the second voltage-dividing capacitor, and the other end of the second voltage-dividing capacitor is connected to the DC output negative terminal; The LLC integrated PFC circuit adopts any one of the Boost phase-controlled rectifier continuous voltage regulation control method, the phase-controlled voltage doubler rectifier control method and the hybrid voltage regulation control method to achieve the expansion of the upper limit of the voltage transformation range in the soft switching state; The Boost phase-controlled rectifier continuous voltage regulation control method includes: Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state; When the phase angle is 0, the first and second docking switch devices are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches a set value A1, the first and second docking switch devices are turned off, the first and second voltage-dividing capacitors are charged, and the voltage increases; wherein A1<pi; when the phase angle is pi, the first and second docking switch devices are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches a set value A1+pi, the first and second docking switch devices are turned off, the first and second voltage-dividing capacitors are charged, and the voltage increases; The phase-controlled voltage-doubling rectification control method includes: Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state; When the phase angle is 0, the first docking switch device is turned on to charge the second voltage-dividing capacitor; when the phase angle reaches a set value A1, the first docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor; wherein A1 < pi; when the phase angle is pi, the first docking switch device is turned on to charge the first voltage-dividing capacitor; when the phase angle reaches a set value A1 + pi, the first docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor; The hybrid voltage regulation control method includes: Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state; When the phase angle is 0, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1, the second docking switch device is turned off, and the second voltage-dividing capacitor is charged; when the phase angle is pi, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1+pi, the second docking switch device is turned off, and the first voltage-dividing capacitor is charged.

2. The LLC integrated PFC circuit with a wide voltage control range according to claim 1, characterized in that: The control steps in the phase-controlled voltage doubler rectifier control method can be replaced by: Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state; When the phase angle is 0, the second docking switch device is turned on to charge the first voltage-dividing capacitor; when the phase angle reaches the set value A1, the second docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor; wherein A1<pi; when the phase angle is pi, the second docking switch device is turned on to charge the second voltage-dividing capacitor; when the phase angle reaches the set value A1+pi, the second docking switch device is turned off to charge the first voltage-dividing capacitor and the second voltage-dividing capacitor.

3. The LLC integrated PFC circuit with a wide voltage control range according to claim 1, characterized in that: The control steps in the hybrid voltage regulation control method can be replaced by: Keep the operating frequency of the LLC circuit unchanged, and control all the switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state; When the phase angle is 0, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1, the first docking switch device is turned off, and the first voltage-dividing capacitor is charged; when the phase angle is pi, the first docking switch device and the second docking switch device are turned on, so that the secondary winding of the high-frequency transformer is short-circuited; when the phase angle reaches the set value A1+pi, the first docking switch device is turned off, and the second voltage-dividing capacitor is charged.

4. The LLC integrated PFC circuit with a wide voltage control range according to any one of claims 1 to 3, characterized in that: The positive busbar and negative busbar of the active bridge are connected to the DC input positive terminal and DC input negative terminal respectively; the AC port of the active bridge is connected to the primary side of the high-frequency transformer and is connected in series with a resonant capacitor and a resonant inductor; the active bridge is composed of a first switching device, a second switching device, a third switching device and a fourth switching device, the DC input positive terminal is connected to the positive electrode of the first switching device and the positive electrode of the third switching device; the negative electrode of the first switching device is connected to the positive electrode of the resonant capacitor and the positive electrode of the second switching device; the negative electrode of the third switching device is connected to the positive electrode of the resonant inductor and the positive electrode of the fourth switching device; and the DC input negative terminal is connected to the negative electrodes of the second switching device and the fourth switching device; The method of maintaining the operating frequency of the LLC circuit unchanged and controlling all switching devices constituting the active bridge in the LLC circuit to operate in a soft switching state includes the following steps: Connect the DC input positive terminal and DC input negative terminal to the positive and negative poles of the DC power supply respectively; Among the switching devices that constitute the active bridge, the first switching device and the fourth switching device are turned on or off simultaneously, and the second switching device and the third switching device are turned on or off simultaneously. The first switching device and the fourth switching device are alternately turned on and off with the second switching device and the third switching device, and the duty cycle is maintained at 50%. The switching frequency is F1. The resonant frequency of the resonant circuit formed by the resonant capacitor and the resonant inductor is F2. By controlling F1 to be less than or equal to F2, it is ensured that the first switching device, the second switching device, the third switching device, and the fourth switching device operate in a soft switching state.

5. The LLC integrated PFC circuit with a wide voltage control range according to claim 1, characterized in that: The first docking switch device and the second docking switch device are both power electronic switches composed of two power electronic switches connected in reverse series and have forward and reverse bidirectional shutoff capabilities.

6. The LLC integrated PFC circuit with a wide voltage control range according to claim 1, characterized in that: The secondary rectifier bridge is composed of a first diode, a second diode, a third diode and a fourth diode; the DC output positive terminal is connected to the positive electrode of the first voltage-dividing capacitor, the negative electrode of the first diode and the negative electrode of the third diode; the positive electrode of the first diode is connected to the positive electrode of the secondary winding of the high-frequency transformer, the negative electrode of the second diode and the positive electrode of the first docking switch device; the positive electrode of the third diode is connected to the negative electrode of the secondary winding of the high-frequency transformer, the negative electrode of the fourth diode and the negative electrode of the second docking switch device; the positive electrode of the second diode and the positive electrode of the fourth diode are connected to the negative electrode of the second voltage-dividing capacitor and the DC output negative terminal; the negative electrode of the first docking switch device is connected to the positive electrode of the second docking switch device, the negative electrode of the first voltage-dividing capacitor and the positive electrode of the second voltage-dividing capacitor.

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