Semi-secondary buck-boost DC-DC converter soft switching circuit

Abstract

The invention provides a transformer-free resonant soft switching circuit based on a semi-secondary buck-boost DC-DC converter, and an auxiliary soft switching network is designed on the basis of a traditional semi-secondary buck-boost DC-DC converter circuit. Three auxiliary soft switching networks are designed for circuit structures of a front stage and a rear stage of the half-secondary buck-boost DC-DC converter, and comprise two single-capacitor auxiliary soft switching circuits of the front stage and a multi-element network which is connected with a main switching device in parallel and comprises an auxiliary switch; the semi-secondary buck-boost DC-DC converter circuit based on the resonance type soft switch comprises three power diodes and one main switch tube in a main circuit, the three power diodes and the one main switch tube can achieve the complete soft switch on and off functions, and meanwhile power devices of an auxiliary soft switch network assembly comprise two auxiliary power diodes and one auxiliary power switch tube. A complete soft switching function can be turned on and turned off; the auxiliary soft switching network is suitable for the converter with more power diodes or main switches and high-frequency working conditions, can effectively improve the efficiency of the converter, and has a wide voltage regulation range and a load range.

Description

Technical Field

[0001] The present invention relates to the technical field of soft switching circuits of semi-quadratic buck-boost converters, and in particular to a transformerless resonant soft switching circuit of a semi-quadratic buck-boost converter and a semi-quadratic buck-boost converter device with full soft switching of all power devices. Background Art

[0002] The application scenarios of DC-DC converters are very wide, including data centers, communication equipment, automotive industry, industrial control, solar energy applications, etc. Among them, there is an active switching device semi-quadratic buck-boost DC-DC converter, which has high buck-boost function, wide input and output voltage range, stability, reliability, fast response and high precision.

[0003] In order to reduce the weight and size of the converter and meet the technical requirements of high power density equipment, it is necessary to increase the switching frequency. However, the increase in switching frequency leads to an increase in switching losses, thereby reducing the transmission efficiency of traditional pulse width modulation (PWM) switch mode converters. Although there is only one active power switch tube for the semi-quadratic buck-boost converter, there are three power diodes. Under high-frequency working conditions, the switching losses of the four tubes will increase significantly. Therefore, the overall efficiency of the converter can be improved by reducing the switching losses of the power devices. Soft switching technology is to control the conduction and shutdown of the switching device under zero voltage and zero current conditions, which effectively reduces the switching loss and switching noise of the circuit and is widely used in power electronic devices. However, there is a lack of literature and information on the soft switching design of semi-quadratic DC-DC converter circuits. The present invention proposes a resonant soft switching circuit based on a semi-quadratic buck-boost DC-DC converter, which has the characteristics of soft switching functions of all power devices, full soft switching capability, large PWM adjustment range, high buck-boost ratio, and high switching frequency. Summary of the invention

[0004] A resonant soft-switching circuit of a secondary buck converter, characterized in that it comprises: a DC voltage source, a main circuit component, a load, and an auxiliary soft-switching network component;

[0005] Among them, the auxiliary soft switch network includes: three groups of circuits, namely, two single capacitor soft switch networks and a resonant network containing an auxiliary switch. The auxiliary soft switch capacitor connected in parallel with the front-stage diode of the main circuit is auxiliary soft switch network 1; the auxiliary soft switch capacitor connected in parallel with the front-stage output end of the main circuit is auxiliary soft switch network 2; the auxiliary soft switch network about the main switch in the main circuit is auxiliary soft switch network 3. The positive electrode of the DC voltage source is connected to the first end of the capacitor of the auxiliary soft switch network 1, and the midpoint of the diode connected in series with the front-stage of the main circuit is connected to the second end of the capacitor of the auxiliary switch network 1. The negative electrode of the DC power supply is connected to the second end of the capacitor of the auxiliary soft switch network 2, and the drain of the main switch of the main circuit is connected to the first section of the capacitor of the soft switch network 2. The auxiliary soft switch network 3 includes two parts, one part of the soft switch network component is connected in parallel with the main switch, which is the soft switch assembly 3-1, and the other part is the resonant inductor connected in series with the main switch, which is the soft switch assembly 3-2. The drain of the main switch in the main circuit is electrically connected to the first end of the auxiliary soft switch network component 3-1, and the source of the main switch in the main circuit is electrically connected to the second end of the auxiliary soft switch network component 3-1 or to the first end of the auxiliary soft switch network component 3-2. The cathode of the output freewheeling diode of the rear stage in the main circuit is electrically connected to the second end of the auxiliary soft switch network component 3-2. The control end of the main circuit component and the control end of the auxiliary soft switch network component are connected to the controller.

[0006] The auxiliary soft switch network 3 component includes an auxiliary switch tube, a first auxiliary diode, a second auxiliary diode, an auxiliary resonant capacitor, and a second auxiliary resonant inductor to form an auxiliary soft switch network component 3-1, and the first auxiliary resonant inductor constitutes an auxiliary soft switch network component 3-2. Among them, the control end of the auxiliary switch tube is connected to the controller, the first end of the auxiliary switch tube is electrically connected to the connection point between the anode of the second end of the second auxiliary diode and the first end of the second auxiliary resonant inductor, and the second end of the auxiliary switch tube is electrically connected to the connection point between the second end of the resonant capacitor and the anode of the first end of the first auxiliary diode. The first end of the first auxiliary resonant inductor is electrically connected to the main switch source in the main circuit or to the second end of the auxiliary soft switch network component 3-1, and the second end of the first auxiliary resonant inductor is electrically connected to the load grounding terminal. The first end of the first auxiliary resonant capacitor and the first end cathode of the second auxiliary diode are jointly the first end of the auxiliary soft switch network component 3-1. The second end of the second auxiliary resonant inductor and the first end cathode of the first auxiliary diode are jointly the second end of the auxiliary soft switch network component 3-1. The first end of the first auxiliary resonant inductor is the first end of the auxiliary soft switch network component 3 - 2 , and the second end of the first auxiliary resonant inductor is the second end of the auxiliary soft switch network component 3 - 2 .

[0007] The main circuit assembly includes a front-stage circuit and a rear-stage circuit, and the components include: a main switch tube, a front-stage first main diode, a front-stage second main diode, a front-stage energy storage inductor, a front-stage energy storage capacitor, a rear-stage freewheeling diode, a rear-stage filter inductor and a filter capacitor, and the main switch tube connects the front stage with the rear stage. Among them, the control end of the main switch tube is connected to the controller, the first end of the main switch tube is electrically connected to the second end of the front-stage energy storage inductor and the second end of the front-stage energy storage capacitor of the main circuit, and the second end of the main switch tube is electrically connected to the second end of the auxiliary soft switch network 3-1 component and the first end of the auxiliary soft switch network 3-2 component. The front-stage first main diode is connected in series with the front-stage second main diode, the anode of the front-stage first main diode is connected to the cathode of the DC voltage source, the cathode of the front-stage second main diode is connected to the anode of the DC voltage source, the first end of the front-stage energy storage inductor is connected to the cathode of the front-stage first main diode and the anode of the front-stage second main diode, and the first end of the front-stage energy storage inductor is electrically connected to the cathode of the second main diode and the anode of the DC voltage source. The second end of the front-stage energy storage inductor is connected to the second end of the front-stage energy storage capacitor, and is also connected to the first end of the main switch tube. The first end of the front-stage energy storage capacitor is connected to the midpoint of the series-connected front-stage first main diode and the front-stage second main diode. The cathode of the rear-stage freewheeling diode is connected to the positive terminal of the load, the first end of the rear-stage filter capacitor is electrically connected, the anode of the rear-stage freewheeling diode is electrically connected to the first end of the rear-stage filter inductor and the cathode of the DC voltage source, and the second end of the rear-stage filter capacitor is electrically connected to the second end of the rear-stage filter inductor and the load grounding terminal.

[0008] The resonant soft switching circuit of a semi-quadratic buck-boost converter according to claim 1 is characterized in that the auxiliary switch tube is an NMOS tube or an IGBT tube, the control end of the auxiliary switch tube is the gate of the NMOS tube or the gate of the IGBT tube, the first end of the auxiliary switch tube is the drain of the NMOS tube or the collector of the IGBT tube, and the second end of the auxiliary switch tube is the source of the NMOS tube or the emitter of the IGBT tube.

[0009] The resonant soft switching circuit of a semi-quadratic buck-boost converter according to claim 1 is characterized in that the main switch tube is an NMOS tube or an IGBT tube, the control end of the main switch tube is the gate of the NMOS tube or the IGBT tube, the first end of the main switch tube is the drain of the NMOS tube or the collector of the IGBT tube, and the second end of the main switch tube is the source of the NMOS tube or the emitter of the IGBT tube.

[0010] A resonant soft switching circuit of a semi-quadratic buck-boost converter, characterized in that it comprises a controller and a resonant soft switching circuit of a semi-quadratic buck-boost converter according to any one of claims 1 to 3, wherein the control end of the main circuit component and the control end of the auxiliary soft switching network component are electrically connected to the output end of the controller;

[0011] Wherein, the controller is configured to control the switching operation of the auxiliary switch tube and the main switch tube, and the main switch tube and the auxiliary switch tube are turned on and off at the same time. When turned on, the zero current of the main switch tube is turned on, and then the auxiliary soft switch network is used to create conditions for the zero voltage turn-off of the main switch tube and the auxiliary switch tube. After the auxiliary resonant capacitor is discharged to zero, the main switch tube and the auxiliary switch tube are controlled to be turned off at zero voltage. During the entire switching cycle, all diodes and main switch tubes in the main circuit, as well as all auxiliary diodes and auxiliary switch tubes in the auxiliary soft switch network components are soft switches, and the overall circuit adjusts the output voltage by controlling the duty cycle of the main switch tube. It has a wide voltage regulation range and load range. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a circuit diagram of a secondary buck converter;

[0013] Figure 2 1 is a circuit diagram of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0014] Figure 3 1 is a schematic diagram of a circuit principle waveform of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0015] Figure 4 It is a schematic diagram of equivalent circuits of each stage of a circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0016] Figure 4 (a) is a schematic diagram of the first stage equivalent circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0017] Figure 4 (b) is a schematic diagram of a second-stage equivalent circuit of a circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0018] Figure 4 (c) is a schematic diagram of a third-stage equivalent circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0019] Figure 4(d) is a schematic diagram of a fourth-stage equivalent circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0020] Figure 4 (e) is a schematic diagram of a fifth-stage equivalent circuit of a circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0021] Figure 4 (f) is a schematic diagram of the sixth stage equivalent circuit of a circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0022] Figure 4 (g) is a schematic diagram of the seventh stage equivalent circuit of a circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0023] Figure 4 (h) is a schematic diagram of an eighth-stage equivalent circuit of a circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention;

[0024] Figure 4 (i) is a schematic diagram of a ninth-stage equivalent circuit of a circuit of a semi-quadratic buck-boost converter based on resonant soft switching provided by an embodiment of the present invention; DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0026] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0027] See also Figure 2 The first embodiment of the present invention provides a transformerless semi-quadratic buck-boost converter resonant soft switching circuit, comprising: a DC voltage source V in, main circuit components, load R, and auxiliary soft switch network components; wherein the auxiliary soft switch network includes: three groups of circuits, namely two single capacitor soft switch networks and a resonant network containing an auxiliary switch. The semi-quadratic buck-boost converter main circuit includes a front stage circuit and a rear stage circuit. The auxiliary soft switch capacitor C connected in parallel with the second diode D2 of the front stage D2 , the auxiliary soft switching capacitor C D2 is an auxiliary soft switch network 1; an auxiliary soft switch capacitor C3 connected in parallel to the front-stage output end of the main circuit, and the auxiliary soft switch capacitor C3 is an auxiliary soft switch network 2; the auxiliary soft switch network 3 includes an auxiliary soft switch network component 3-1 connected in parallel with the main switch tube Q2 and an auxiliary soft switch network component 3-1 connected in series with the network, namely, a resonant inductor L σ The DC voltage source V in The positive electrode of the auxiliary soft switch network 1 capacitor C D2 The first end is connected to the midpoint of the first and second diodes D1 and D2 in series in the front stage of the main circuit and the capacitor C of the auxiliary switch network 1 D2 The second end is connected to the DC power supply V in The negative electrode is connected to the second end of the capacitor D3 of the auxiliary soft switch network 2, and the first end of the main switch of the main circuit and the first end of the auxiliary soft switch network 3-1 are connected to the first end of the capacitor C3 of the soft switch network 2. The first end of the main switch Q2 in the main circuit is connected to the first end of the auxiliary resonant soft switch network 3-1, and the second end of the main switch Q2 in the main circuit is connected to the second end of the auxiliary resonant soft switch network 3-1. The current limiting inductor L of the auxiliary soft switch network 3-2 σ The first end is connected to the second end of the main switch Q2, and the current limiting inductor L of the auxiliary soft switch network 3-2 σ The second end is connected to the second end of the subsequent energy storage inductor L2 and the load grounding end. The control end of the main circuit component and the control end of the auxiliary soft switch network component are connected to the controller.

[0028] Preferably, the auxiliary soft switch capacitor C of the auxiliary soft switch network 1 D2 The first end is connected to the DC voltage source V in The anode of the front stage second diode D2 is connected to the cathode of the auxiliary soft switching capacitor C D2 The second end of the auxiliary soft switch capacitor C is connected to the anode of the second diode D2 in the front stage of the main circuit. D2 The first end of the auxiliary soft switch capacitor C3 of the auxiliary soft switch network 2 is connected to the second end of the front-stage energy storage inductor L1 of the main circuit and the first end of the front-stage energy storage inductor C1, and the second end of C3 is connected to the DC voltage source V in The cathode of the first diode D1 in the previous stage is connected.

[0029] Preferably, the auxiliary soft switch network 3 component includes an auxiliary switch tube Q sn , the first auxiliary diode D sn1 , the second auxiliary diode D sn2 , the second resonant inductor L sn , auxiliary resonant capacitor C sn , forming an auxiliary resonant soft switch network 3-1, and the first resonant inductor L σ That is, an auxiliary resonant soft switch network 3-2 is formed. sn The control end is connected to the controller. Auxiliary resonant capacitor C sn The first end of the auxiliary resonant capacitor C is connected to the first end of the main switch Q2. sn The second end of the first auxiliary diode D sn1 The anode of the first auxiliary diode D sn1 The cathode of the second auxiliary diode D is connected to the second end of the main switch Q2 to form a series branch 1 in the soft switching circuit network. sn2 The cathode of the second auxiliary diode D is connected to the first end of the main switch Q2. sn2 The anode and resonant inductor L sn The first end is connected to the resonant inductor L sn The second end is connected to the second end of the main switch Q2 to form a series branch 2 in the soft switching circuit network. sn With the first auxiliary diode D sn1 The anode of the second auxiliary diode D is connected, and its connection point is the midpoint of the series branch 1; sn2 The anode and resonant inductor L sn The first end is connected, and the connection point is the midpoint of the series branch 2. Auxiliary switch tube Q sn The first end is connected to the midpoint of the series branch 2, and the auxiliary switch tube Q sn The second end of the resonant inductor L is connected to the midpoint of the series branch 1. σ The first end of the resonant inductor L is connected to the second end of the main switch tube Q2 and the second end of the auxiliary soft switch network 3-1. σ The two ends of the inductor are electrically connected to the second end of the subsequent energy storage inductor L2 and the load grounding end.

[0030] Preferably, the main circuit assembly includes a front-stage circuit and a rear-stage circuit, and the components included are: a main switch tube Q2, a front-stage first main diode D1, a front-stage second main diode D2, a front-stage energy storage inductor L1, a front-stage energy storage capacitor C1, a rear-stage freewheeling diode D3, a rear-stage filter inductor L2 and a filter capacitor C2, and the load is connected in parallel with the filter capacitor C2. The main switch tube Q2 connects the front stage with the rear stage. Among them, the control end of the main switch tube Q2 is connected to the controller, the first end of the main switch tube Q2 is electrically connected to the second end of the front-stage energy storage inductor L1 of the main circuit and the first end of the auxiliary soft switch network component 3-1, and the second end of the main switch tube Q2 is electrically connected to the second end of the auxiliary soft switch network 3-1 and the resonant inductor L in the auxiliary soft switch network 3-2. σ The cathode of the first diode D1 is connected to the anode of the second diode D2, and the anode of the first diode is connected to the DC voltage source V in The cathode of the second diode D2 is connected to the DC voltage source V in The anode of the preceding stage energy storage inductor L1 is connected, the first end of the preceding stage energy storage inductor L1 is connected to the cathode of the preceding stage second diode D2, the second end of the preceding stage energy storage inductor L1 is connected to the second end of the preceding stage energy storage capacitor C1 and the first end of the main switch tube Q1, and the first end of the preceding stage energy storage capacitor C1 is connected to the midpoint of the preceding stage first diode D1 and the preceding stage second diode D2 connected in series.

[0031] The cathode of the post-stage freewheeling diode D3 is connected to the first end of the post-stage filter capacitor C2, the anode of the post-stage freewheeling diode D3 is connected to the negative end of the DC voltage source and the first end of the post-stage filter inductor L2, the second end of the post-stage filter capacitor C2 is electrically connected to the second end of the post-stage filter inductor L2 and the load grounding terminal. The load R is connected in parallel with the post-stage filter capacitor C2.

[0032] See also Figure 3 , in steady-state operation, the soft-switching semi-quadratic buck-boost converter circuit based on the resonant network can be divided into 9 operating modes, and the circuit diagrams of each stage are as follows: Figure 4 shown.

[0033] Mode 1 to Mode 4, that is, the time period t0-t1 is divided into 4 time-segment modes. Figure 3 Mode 1 [t0, t'0]: The circuit working state in this mode is as follows Figure 4 As shown in (a). Before time t0, the main switch tube Q2 and the auxiliary switch tube Q sn are both in the off state, the auxiliary resonant inductor L sn Current And the subsequent inductor L σ Current is zero, the resonant capacitor C snThe voltage is maintained at the resonance peak. The front-stage inductor L1 resonates with the front-stage capacitor C1, and the unidirectional resonant current is i L1 The voltage of the front-stage auxiliary capacitor C3 is maintained at V in (1+D). The current of the output filter inductor L2 of the rear stage flows through D3, and the load current I o The output filter inductor L2 provides the output filter. At time t0, the main switch tube Q2 and the auxiliary switch tube Q sn At the same time, Q2 connects the front and rear stages of the conversion circuit, and incorporates the power supply into the loop that transmits energy to the load. σ The DC voltage source V in Under the excitation of σ The series-connected Q2 gradually increases from zero current, thus achieving zero current turn-on (ZCS-on) of Q2.

[0034] In the auxiliary resonant network 3-1 connected in parallel with the main switch tube Q2, the resonant capacitor C sn With the resonant inductor L sn The main switch tube and the auxiliary switch tube form a resonant circuit, and the resonant capacitor C sn Discharge, resonant inductance L sn Charging, flowing through the resonant inductor L sn Current The auxiliary switch Q sn Also known as zero current switch-on (ZCS-on).

[0035] At the same time, the front-stage energy storage inductor L1 charges the front-stage energy storage capacitor C1 with a current i L1 Gradually decreases until t1, when the DC voltage source positive output current is equal to i L1 The charging current of the front-stage capacitor C1 drops to zero, so that the power diode D2 is turned off with zero current (ZCS-off). At the same time, the current flowing through the diode D3 in the rear-stage circuit Start descending from I2.

[0036] Mode 2 [t'0, t"0]: The circuit working state in this mode is as follows Figure 4 (b) At t1, the auxiliary capacitor C connected in parallel at the moment when the front diode D2 is turned off with zero current D2 The voltage is zero, and the current i flows through the front-stage inductor L1 There is no increase, while the power supply V in In order to meet the demand of the subsequent circuit for increased current, the power supply V in To the auxiliary capacitor C D2 It is charged and discharged through the front capacitor C1. At the same time, it forms a voltage loop with the auxiliary capacitor C3. Under the constraint of the loop KVL, the voltage of C3 is V in(1+D) discharges to the next stage, so that the previous stage inductor branch and auxiliary capacitor C D2 The currents of the front-stage capacitor C1 branch and the auxiliary capacitor C3 branch flow to the rear-stage circuit through the main switch tube Q1. D2 Voltage is At t2, the polarity of the front-stage inductor changes and begins to absorb the power supply energy for storage. The auxiliary resonant network connected in parallel with the main switch tube Q2 and the subsequent circuit mode remain in the previous mode. At t2, the auxiliary capacitor C D2 Charge to V in At the same time, the discharge voltage of auxiliary capacitor C3 is V in D, the mode ends. In this state, the auxiliary resonant inductor L σ With the previous auxiliary capacitor C3, auxiliary capacitor C D2 The series branches with the previous capacitor C1 resonate respectively to realize the transfer of capacitor energy to the next stage.

[0037] Mode 3 [t”0, t”'0]: The circuit working state in this mode is as follows Figure 4 (c) At t2, the voltage of auxiliary capacitor C3 is V in D has the same voltage as the front-stage capacitor C1, the front-stage diode D1 is turned on with zero voltage, and the front-stage capacitor C1 and the auxiliary resonant inductor L σ Resonance continues to maintain the discharge state of C1. The circuit mode of the auxiliary resonant soft switch network 3-1 connected in parallel with the main switch tube Q2 still maintains the previous mode. As the current flowing through the subsequent energy storage inductor L2 gradually increases, the current of the subsequent freewheeling diode D3 gradually decreases. This mode continues until the inductor current Rise to I L2 , that is, the current of D3 decreases to zero, that is, zero current shutdown (ZCS-off). In this mode, the diode D3 clamps the load current, and the load current is provided by the post-stage filter capacitor C2.

[0038] Mode 4 [t”’0, t1]: The circuit working state in this mode is as follows Figure 4 (d) The resonant capacitor C in this mode sn The energy is completely transferred to the resonant inductor L sn , and continues until the resonant capacitor voltage until.

[0039] Mode 5 [t1, t2]: The circuit working state in this mode is as follows Figure 4 (e) At time t4, the resonant capacitor C in the auxiliary resonant network 3-1 sn The voltage discharges to zero, and the auxiliary diode D sn1 and D sn2 To achieve zero voltage turn-on (ZVS-on), the resonant inductor L snPart of the current flows through the freewheeling diode D sn2 The freewheeling circuit formed by the main switch tube Q2, part of which passes through the freewheeling diode D sn1 and auxiliary switch tube Q sn The freewheeling circuit is formed. The working status of other devices is consistent with the previous mode. In this mode, the main switch tube Q2 and the auxiliary switch tube Q sn The voltage across the two ends is zero, providing conditions for the zero voltage turn-off (ZVS-off) of the two switch tubes. This stage continues until the main switch tube Q2 and the auxiliary switch tube Q sn The shutdown signal arrives.

[0040] Mode 6 [t2, t3]: The circuit working state in this mode is as follows Figure 4 (f) At t5, the main switch tube Q2 and the auxiliary switch tube Q sn The shutdown signal arrives. At this moment, the auxiliary resonant inductor L sn Through the auxiliary diode D sn1 and D sn2 With the resonant capacitor C sn A resonant circuit is formed. sn Resonance voltage Charging starts from zero, so Q2, Q sn Zero voltage shutdown (ZVS-off). After Q2 is turned off, the auxiliary inductor L σ The current flows through the resonant capacitor C sn and diode D sn1 There is conduction loss in the auxiliary switch tube and auxiliary diode in the auxiliary resonant network 3-1, so the resonant capacitor C sn The stored energy comes from two parts: one part is the resonant inductor L sn The other part is provided by the front stage circuit. The auxiliary inductor L of the rear stage circuit σ The current gradually decreases Part of the current of L2 is transferred to the load through D3. The current flowing through diode D3 starts to rise from zero, and diode D3 achieves zero current conduction (ZCS-on). , the mode ends.

[0041] Mode 7 [t3, t4]: The circuit working state in this mode is as follows Figure 4 (g) At t6, the auxiliary inductor L of the subsequent circuit σ The current drops to zero, and the load current I o The output filter capacitor C2 and the output inductor L2 provide the freewheeling current. The front stage forms two charging and discharging circuits, one of which is composed of L1 and C1, C D2 The composition of C1 charging, C D2The first circuit is a circuit for discharging and charging L1, and the second circuit is a circuit for charging C3 and L1, which is composed of L1, C3, and power supply Vin. The resonant inductor in the resonant circuit continues to charge the resonant capacitor. At t7, the front-stage auxiliary capacitor C D2 Discharge voltage At the same time, the voltage of the front-stage auxiliary capacitor C3 is charged to V C3 -V in (1+D), enter the next mode.

[0042] Mode 8 [t4, t5]: The circuit working state in this mode is as follows Figure 4 At t7, after the front stage circuit is charged and discharged, the front stage auxiliary capacitor C D2 Voltage The front-stage diode D2 is turned on at zero voltage (ZVS-on), forming a loop for the front-stage inductor L1 to charge the front-stage capacitor C1. The rear-stage circuit maintains the previous mode unchanged. sn Through the diode D sn1 and D sn2 Continue to give the resonant capacitor C sn The resonant capacitor voltage continues to increase while charging. This stage continues until the auxiliary resonant inductor current discharges to zero.

[0043] Mode 9 [t5, t6]: The circuit working state in this mode is as follows Figure 4 (i) At t8, the resonant inductor L in the auxiliary resonant network sn Current Discharge to zero. Resonant capacitor C sn The voltage reaches a maximum value of Auxiliary diode D sn1 and D sn2 Achieve zero current shutdown (ZCS-off). At this time, the load current I o Provided by the output filter inductor L2. The front-stage inductor L1 continues to charge the front-stage capacitor C1. This mode continues until the main switch tube conduction signal of the next cycle arrives.

Claims

1. A transformerless resonant soft switching circuit based on a semi-quadratic buck-boost DC-DC converter, characterized in that: include: DC voltage source, main circuit components, load, and auxiliary soft switching network components; Among them, the auxiliary soft switch network includes: three groups of circuits, namely, two single capacitor soft switch networks and a resonant network containing an auxiliary switch. The auxiliary soft switch capacitor connected in parallel with the second main diode of the front stage of the main circuit is auxiliary soft switch network 1; the auxiliary soft switch capacitor connected in parallel with the output end of the front stage of the main circuit is auxiliary soft switch network 2; the auxiliary soft switch network about the main switch in the main circuit is auxiliary soft switch network 3. The positive electrode of the DC voltage source is connected to the first end of the capacitor of the auxiliary soft switch network 1, and the midpoint of the diode connected in series with the front stage of the main circuit is connected to the second end of the capacitor of the auxiliary switch network 1. The negative electrode of the DC power supply is connected to the second end of the capacitor of the auxiliary soft switch network 2, and the drain of the main switch of the main circuit is connected to the first section of the capacitor of the soft switch network 2. The auxiliary soft switch network 3 includes two parts, one part of the soft switch network component is connected in parallel with the main switch, which is the soft switch assembly 3-1, and the other part is the resonant inductor connected in series with the main switch, which is the soft switch assembly 3-2. The drain of the main switch in the main circuit is electrically connected to the first end of the auxiliary soft switch network component 3-1, and the source of the main switch in the main circuit is electrically connected to the second end of the auxiliary soft switch network component 3-1 or to the first end of the auxiliary soft switch network component 3-2. The cathode of the output freewheeling diode of the rear stage in the main circuit is electrically connected to the second end of the auxiliary soft switch network component 3-2. The control end of the main circuit component and the control end of the auxiliary soft switch network component are connected to the controller. The auxiliary soft switch network 3 component includes an auxiliary switch tube, a first auxiliary diode, a second auxiliary diode, an auxiliary resonant capacitor, and a second auxiliary resonant inductor to form an auxiliary soft switch network component 3-1, and the first auxiliary resonant inductor constitutes an auxiliary soft switch network component 3-2. Among them, the control end of the auxiliary switch tube is connected to the controller, the first end of the auxiliary switch tube is electrically connected to the connection point between the anode of the second end of the second auxiliary diode and the first end of the second auxiliary resonant inductor, and the second end of the auxiliary switch tube is electrically connected to the connection point between the second end of the resonant capacitor and the anode of the first end of the first auxiliary diode. The first end of the first auxiliary resonant inductor is electrically connected to the main switch source in the main circuit or to the second end of the auxiliary soft switch network component 3-1, and the second end of the first auxiliary resonant inductor is electrically connected to the load grounding terminal. The first end of the first auxiliary resonant capacitor and the first end cathode of the second auxiliary diode are jointly the first end of the auxiliary soft switch network component 3-1. The second end of the second auxiliary resonant inductor and the first end cathode of the first auxiliary diode are jointly the second end of the auxiliary soft switch network component 3-1. The first end of the first auxiliary resonant inductor is the first end of the auxiliary soft switch network component 3 - 2 , and the second end of the first auxiliary resonant inductor is the second end of the auxiliary soft switch network component 3 - 2 . The main circuit assembly includes a front-stage circuit and a rear-stage circuit, and the components include: a main switch tube, a front-stage first main diode, a front-stage second main diode, a front-stage energy storage inductor, a front-stage energy storage capacitor, a rear-stage freewheeling diode, a rear-stage filter inductor and a filter capacitor, and the main switch tube connects the front stage with the rear stage. Among them, the control end of the main switch tube is connected to the controller, the first end of the main switch tube is electrically connected to the second end of the front-stage energy storage inductor and the second end of the front-stage energy storage capacitor of the main circuit, and the second end of the main switch tube is electrically connected to the second end of the auxiliary soft switch network 3-1 component and the first end of the auxiliary soft switch network 3-2 component. The front-stage first main diode is connected in series with the front-stage second main diode, the anode of the front-stage first main diode is connected to the cathode of the DC voltage source, the cathode of the front-stage second main diode is connected to the anode of the DC voltage source, the first end of the front-stage energy storage inductor is connected to the cathode of the front-stage first main diode and the anode of the front-stage second main diode, and the first end of the front-stage energy storage inductor is electrically connected to the cathode of the second main diode and the anode of the DC voltage source. The second end of the front-stage energy storage inductor is connected to the second end of the front-stage energy storage capacitor, and is also connected to the first end of the main switch tube. The first end of the front-stage energy storage capacitor is connected to the midpoint of the series-connected front-stage first main diode and the front-stage second main diode. The cathode of the rear-stage freewheeling diode is connected to the positive terminal of the load, the first end of the rear-stage filter capacitor is electrically connected, the anode of the rear-stage freewheeling diode is electrically connected to the first end of the rear-stage filter inductor and the cathode of the DC voltage source, and the second end of the rear-stage filter capacitor is electrically connected to the second end of the rear-stage filter inductor and the load grounding terminal.

2. The resonant soft switching circuit of a semi-quadratic buck-boost converter according to claim 1, characterized in that: The auxiliary switch tube is an NMOS tube or an IGBT tube, the control end of the auxiliary switch tube is the gate of the NMOS tube or the gate of the IGBT tube, the first end of the auxiliary switch tube is the drain of the NMOS tube or the collector of the IGBT tube, and the second end of the auxiliary switch tube is the source of the NMOS tube or the emitter of the IGBT tube.

3. The resonant soft switching circuit of a semi-quadratic buck-boost converter according to claim 1, characterized in that: The main switch tube is an NMOS tube or an IGBT tube, the control end of the main switch tube is the gate of the NMOS tube or the IGBT tube, the first end of the main switch tube is the drain of the NMOS tube or the collector of the IGBT tube, and the second end of the main switch tube is the source of the NMOS tube or the emitter of the IGBT tube.

4. A resonant soft switching circuit of a semi-quadratic buck-boost converter, characterized in that: A controller and a resonant soft switch circuit of a semi-quadratic buck-boost converter as claimed in any one of claims 1 to 3, wherein the control end of the main circuit component and the control end of the auxiliary soft switch network component are electrically connected to the output end of the controller; Wherein, the controller is configured to control the switching operation of the auxiliary switch tube and the main switch tube, and the main switch tube and the auxiliary switch tube are turned on and off at the same time. When turned on, the zero current of the main switch tube is turned on, and then the auxiliary soft switch network is used to create conditions for the zero voltage turn-off of the main switch tube and the auxiliary switch tube. After the auxiliary resonant capacitor is discharged to zero, the main switch tube and the auxiliary switch tube are controlled to be turned off at zero voltage. During the entire switching cycle, all diodes and main switch tubes in the main circuit, as well as all auxiliary diodes and auxiliary switch tubes in the auxiliary soft switch network components are soft switches, and the overall circuit adjusts the output voltage by controlling the duty cycle of the main switch tube. It has a wide voltage regulation range and load range.

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