Charging pile side efficient stacking half-bridge topology circuit applied to dynamic load

Abstract

The invention relates to the field of electricity, and provides a charging pile side efficient stacking half-bridge topology circuit applied to a dynamic load. The problems that traditional Sigma topology is low in efficiency, a Buck converter is large in voltage stress and obvious in switching loss, and low efficiency is caused by a small switching period are solved. The input end of the stacked half-bridge inverter unit is connected with direct-current input voltage, the output end of the stacked half-bridge inverter unit provides alternating-current excitation voltage with alternating amplitude, and pre-adjusted direct-current voltage is led out from the midpoint of the stacked half-bridge inverter unit; the LLC resonant power transmission unit receives the alternating-current excitation voltage and efficiently transmits main power at resonant frequency; the stacked half-bridge inversion unit, the LLC resonance power transmission unit and the partial power regulation unit form a Sigma type power distribution architecture, and the Sigma type power distribution architecture jointly provides power for the load.

Description

TECHNICAL FIELD

[0001] The application relates to the electrical field and provides a charging pile side efficient stacked half-bridge topology circuit applied to a dynamic load. BACKGROUND

[0002] LLC resonant converters have the advantages of high efficiency, small size and low EMI, and are widely used in electric vehicle charging piles, server power supplies and renewable energy systems. However, in the application occasions of dynamic load and high step-down ratio, the efficiency, size and EMI advantages of the traditional frequency-modulated LLC converter will gradually disappear. In order to adapt to the demand of wide-range regulation of the LLC converter, the current work can be divided into the following three categories: 1) hybrid modulation strategy, 2) topology reconfiguration method, and 3) partial power processing method.

[0003] In order to avoid the problems of efficiency reduction and magnetic element size increase caused by wide frequency modulation range, an asymmetric pulse width modulation (PWM) strategy for hold-up time is proposed. However, the introduced DC bias limits the improvement of efficiency. PWM and PFM (pulse frequency modulation) hybrid control maintains the symmetry of the magnetic flux while expanding the gain range. However, zero voltage switching (ZVS) may be lost at light load. Phase-shifted control is another effective modulation technique, but it also suffers from ZVS loss at light load. In order to ensure ZVS, a hybrid modulation method combining phase-shifted control and burst control is proposed, but high-frequency oscillation may be induced in the off state.

[0004] In order to reduce the control complexity, combining topology reconfiguration with modulation strategy is an effective method. The primary side inverter bridge can be reconfigured to switch between full-bridge and half-bridge modes. However, the topology reconfiguration-based method still needs a relatively wide frequency regulation range and requires additional control.

[0005] To make the LLC converter work near its resonant frequency (for peak efficiency) while achieving voltage gain regulation, partial power processing (PPP) technique becomes an attractive solution. Sigma converter operates in quasi-parallel topology, where a high efficiency non-regulated LLC stage provides most of the power to the load, while a small Buck converter provides accurate output voltage regulation. However, in wide range, high step-down applications, the duty cycle of the Buck converter becomes extremely small, leading to efficiency degradation. By introducing a transformer isolated topology, the system can avoid forcing the Buck converter to operate at extremely low duty cycle, thus preserving efficiency. However, transformer-based PPP topology often requires a large number of additional components, significantly increasing the overall system size. SUMMARY

[0006] The present application mainly solves the problems of low efficiency, large voltage stress and significant switching loss of the traditional Sigma topology structure in wide input range and high step-down applications, and the problem of small switching period and low efficiency of the Buck converter of the traditional Sigma topology structure in such application scenarios. The present application improves the traditional Sigma topology, reconfigures the LLC inverter bridge into a stacked half-bridge (SHB) structure, and naturally provides a pre-regulated 1 / 2 voltage gain for the partial power processing Buck converter. Therefore, the duty cycle of the Buck converter can be doubled, significantly reducing its voltage stress and improving efficiency. In addition, a phase-shift control scheme is used to achieve ZVS of the SHB, and the Buck converter independently processes voltage regulation, further reducing the energy consumption of the system.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical means:

[0008] The present application provides a high-efficiency power conversion topology circuit for wide input voltage range and high step-down ratio scenarios, comprising:

[0009] a stacked half-bridge inverter unit, whose input end is connected to a direct current input voltage , and whose output end provides a first alternating excitation voltage and a second alternating excitation voltage with alternating amplitude, wherein the midpoint of the stacked half-bridge inverter unit leads out a pre-regulated direct current voltage node VB, and the voltage value of the VB is ;

[0010] an LLC resonant power transmission unit, whose input end is connected to the output end of the stacked half-bridge inverter unit, for receiving the first excitation voltage and the second excitation voltage As a resonant excitation source, it transmits main power efficiently near the resonant frequency, and its output is coupled to the load side through an isolation transformer;

[0011] A partial power regulation unit is connected to the pre-regulated DC voltage node VB, and its output is connected in parallel to the output of the LLC resonant power transmission unit to the load, for independent regulation of the output voltage and transmission of auxiliary power;

[0012] The stacked half-bridge inverter unit, LLC resonant power transmission unit and partial power regulation unit form a Sigma type power distribution architecture, which collectively provides power to the load.

[0013] In the above scheme, the stacked half-bridge inverter unit is composed of first switch S1, second switch S2, third switch S3 and fourth switch S4; wherein the source of S1 and the drain of S2 are connected to form the first node A, the source of S3 and the drain of S4 are connected to form the second node B, and the drain of S1 is connected to the input voltage positive , the source of S2 and the source of S4 are commonly connected to the input voltage negative ;

[0014] The regulated DC voltage node VB is derived from the connection point of the drain of S3 and the source of S2, serving as the input voltage source of the Buck converter;

[0015] The LLC resonant circuit includes a primary resonant inductor Lr, a resonant capacitor Cr and an excitation inductor L m as the primary winding of the transformer, which is connected to the first node A and the second node B;

[0016] The transformer secondary circuit includes a secondary winding with a turns ratio of n:1:1, and the two ends of the secondary winding are connected to the output filter capacitor and the load through the first synchronous rectifier SR1 and the second synchronous rectifier SR2 respectively;

[0017] The partial power regulation unit is a Buck converter circuit, including fifth switch S5, sixth switch S6 and Buck inductor ; wherein the drain of S5 is connected to the regulated DC voltage node VB, the source of S5 is connected to the drain of S6 and the first end of inductor , the source of S6 is connected to the input voltage negative , and the second end of inductor is connected to the output filter capacitor and the load ;

[0018] The stacked half-bridge circuit and the Buck converter circuit jointly provide power for a load in a Sigma type manner, and the stacked half-bridge structure inherently halves the input voltage of the Buck converter, thereby improving the duty cycle and reducing the switching stress.

[0019] In the above scheme, the stacked half-bridge inverter unit is configured to operate the gate drive signals vgs1-vgs4 at a fixed duty cycle of 50%, and the drive signals of S3 / S4 are delayed relative to S1 / S2 by a set dead time through phase shift control.

[0020] In the above scheme, the input voltage of the Buck converter circuit satisfies: The output voltage of the Buck converter circuit satisfies the relationship: .

[0021] In the above scheme, the stacked half-bridge inverter unit sequentially operates the following five working stages in time sequence within one complete switching cycle:

[0022] Stage one[ ]:

[0023] At time t0, the second switch S2 is turned off, and within the dead time, the negative resonant current discharges the output capacitor C oss1 of the first switch S1 and charges the output capacitor C oss2 of S2; when the voltage of C oss1 drops to zero, the body diode of S1 is turned on, realizing zero-voltage turn-on; then S1 and S4 are simultaneously turned on, the resonant tank input voltage becomes , the resonant current rises, the excitation current is clamped by the output voltage and linearly rises, the secondary current starts from zero and increases, and energy is transmitted to the load through the transformer;

[0024] Mode two[ ]:

[0025] At time t1, the fourth switch S4 is turned off, and the resonant current i Lr becomes positive, charging the output capacitor C oss4 of S4 and discharging the output capacitor C oss3 of S3; when the voltage of C oss3 drops to zero, the body diode of S3 is turned on, realizing zero-voltage turn-on of S3; at this time ​, resonant current The resonant trajectory is changed due to the decrease of the excitation voltage, and the excitation current is still clamped, and the secondary current follows The energy continues to be transferred;

[0026] Phase three[ ]:

[0027] At , the resonant current drops to equal the excitation current , the secondary current drops to zero, and the primary stops transferring energy to the secondary; the excitation inductance is out of the clamping state, and , free resonance occurs, continues until , at which time the first switch S1 is turned off, and the positive is prepared for the zero voltage turn-on of S2;

[0028] Phase four[ ]:

[0029] The fifth switch S5 remains on, and the sixth switch S6 remains off, and the Buck inductance current rises linearly with a slope .

[0030] Phase five[ ]:

[0031] The fifth switch S5 is turned off, and the sixth switch S6 is turned on, and the Buck inductance has a voltage , and the inductance current falls linearly with a slope .

[0032] In the above scheme, the first switch S1 and the second switch S2 are complementarily turned on, the third switch S3 and the fourth switch S4 are complementarily turned on, and the driving signals of S3 / S4 have a phase shift angle φ relative to S1 / S2, and the phase shift angle φ is determined by the resonant current The charging and discharging capabilities of the switch output capacitor Coss in the dead time determine that the body diode of all switches is turned on before the switch is turned on, so that the zero voltage turn-on in the full load range is realized.

[0033] The application further provides a control method for controlling the topology circuit, comprising the following steps:

[0034] ​Step 1: control S1 and S2 in the stacked half-bridge inverter unit to be complementary on at a duty cycle of 50%, S3 and S4 are complementary on at a duty cycle of 50%, and the S3 / S4 drive signal is delayed by a phase shift angle φ relative to S1 / S2, φ is dynamically adjusted according to the load current to maintain zero voltage turn-on;

[0035] Step 2: independently adjust the duty cycle D of the fifth switch S5 and / or the sixth switch S6 in the Buck power regulation unit, so that the output voltage is stabilized at the set value;

[0036] Step 3: monitor the output current or power distribution ratio, dynamically adjust the phase shift angle φ and the duty cycle D, and realize power collaborative optimization of the LLC and Buck paths, and maximize the system efficiency.

[0037] Because the application adopts the above technical means, the following beneficial effects are achieved:

[0038] The application adopts the above technical scheme, and has the following beneficial effects:

[0039] (1) The half-bridge LLC in the traditional Sigma topology is reconstructed into a stacked half-bridge (SHB) structure, the SHB naturally divides the input voltage V in into V B and V in −V B , so that the input voltages of LLC and Buck are halved, the switching stress is reduced, the Buck input voltage is reduced to , and the duty cycle of Buck is significantly improved, and the problem of efficiency degradation under low voltage difference is alleviated.

[0040] (2) Buck duty cycle doubling mechanism, through SHB pre-voltage division, the Buck duty cycle D can be increased to 2 times of the duty cycle of the traditional scheme, the voltage stress of Buck is reduced, and the conduction loss is reduced.

[0041] (3) Zero voltage turn-on technology is realized for all load ranges, phase shift control is applied to the switch tube, and full switch tube ZVS is realized in combination with the resonant current, so that the switching loss is eliminated and the efficiency is improved.

[0042] (4) Power distribution optimization and parameter collaborative design, LLC (main power path) and Buck (auxiliary regulation path) collaborative power supply, wide gain range is realized through transformer turns ratio and Buck duty cycle. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 : Sigma topology circuit diagram based on stacked half-bridge structure;

[0044] Figure 2 : ideal steady-state switch waveform;

[0045] Figure 3 Equivalent circuit of different operation modes

[0046] Figure 4 Simplified circuit model of the proposed converter

[0047] Figure 5 Conventional Sigma topology

[0048] Figure 6 Relationship of voltage gain M and power ratio k with duty cycle D. Fig. (a) presents the Sigma topology based on SHB (n=3), Fig. (b) the conventional Sigma topology (n=3). c =3). DETAILED DESCRIPTION

[0049] The embodiments of the present application will be described in detail below. Although the present application will be described and illustrated by referring to some specific embodiments, it is noted that the present application is not limited to these embodiments only. On the contrary, modifications or equivalent alternatives to the present application are also included in the scope of the claims of the present application.

[0050] In addition, in order to better illustrate the present application, numerous specific details are given in the following detailed description. Those skilled in the art will understand that the present application can be implemented without these specific details.

[0051] The present application mainly solves the problems of low efficiency of the conventional Sigma topology structure, large voltage stress of the Buck converter and obvious switching loss in wide input range and high step-down applications, and the problems of small switching period and low efficiency of the Buck converter of the conventional Sigma topology structure in such application scenarios. The present application improves the conventional Sigma topology and reconfigures the LLC inverter bridge into an (SHB) structure, which naturally provides a pre-regulated 1 / 2 voltage gain for the Buck converter for partial power processing. Therefore, the duty cycle of the Buck converter can be doubled, significantly reducing its voltage stress and improving efficiency. In addition, the phase-shift control scheme is adopted to realize ZVS of the SHB, and the Buck converter independently processes voltage regulation, further reducing the energy consumption of the system.

[0052] The present application adopts the following technical solutions to achieve the above-mentioned purposes:

[0053] A charging pile side high-efficiency stacked half-bridge topology circuit applied to a dynamic load, comprising:

[0054] The stacked half-bridge inverter unit has an input end connected to a direct-current input voltage and an output end providing a first alternating excitation voltage with alternating amplitude and a second alternating excitation voltage , wherein the midpoint of the stacked half-bridge inverter unit leads to a pre-regulated DC voltage node VB, the voltage value of the VB is ;

[0055] LLC resonant power transmission unit, the input end is connected to the output end of the stacked half-bridge inverter unit, for receiving the first excitation voltage and the second excitation voltage As a resonant excitation source, it efficiently transmits main power near the resonant frequency, and its output end is coupled to the load side through an isolation transformer;

[0056] Partial power regulation unit, the input end is connected to the pre-regulated DC voltage node VB, and the output end is connected in parallel to the output end of the LLC resonant power transmission unit to the load, for independently regulating the output voltage and transmitting auxiliary power;

[0057] Wherein, the stacked half-bridge inverter unit, LLC resonant power transmission unit and partial power regulation unit constitute a Sigma type power distribution architecture, which provides power for the load together.

[0058] Stacked half-bridge inverter unit, including first switch S1, second switch S2, third switch S3 and fourth switch S4, the output parasitic capacitance is C oss1 , C oss2 , C oss3 , C oss4 (S1-S2 is a common NMOS tube, and there are parasitic parameters in the actual MOS tube model, including parasitic capacitance, parasitic inductance, parasitic resistance and the like, which affect the switching speed and ringing noise and the like. In circuit analysis, the parasitic output capacitance is usually considered, and the charging and discharging of the parasitic output capacitance in the dead time is taken as a basis for judging ZVS (zero voltage switching), which provides guidance for accurate design and optimization of the circuit); wherein, the source of S1 and the drain of S2 are connected to form a first node A, the source of S3 and the drain of S4 are connected to form a second node B, and the drain of S1 is connected to the input voltage positive , the source of S2 and the source of S4 are commonly connected to the input voltage negative ;

[0059] Regulated DC voltage node VB, which is led out from the connection point of the drain of S3 and the source of S2, as the input voltage source of the Buck converter;

[0060] LLC resonant circuit, including series connected primary resonant inductor Lr, resonant capacitor Cr and excitation inductor L mThe first end of the LLC resonant circuit is connected to the first node A, and the second end is connected to the second node B;

[0061] The transformer secondary circuit includes a secondary winding with a turns ratio of n:1:1. The two ends of the secondary winding are connected to the output filter capacitor through a first synchronous rectifier diode SR1 and a second synchronous rectifier diode SR2, respectively. and load ;

[0062] Part of the power regulation unit is a Buck converter circuit, including the fifth switch S5, the sixth switch S6, and a Buck inductor. In this configuration, the drain of S5 is connected to the DC voltage node VB, and the source of S5 is connected to the drain of S6 and the inductor. At the first terminal, the source of S6 is connected to the input voltage. negative electrode ,inductance The second terminal is connected to the output filter capacitor. and load ;

[0063] The stacked half-bridge circuit and the Buck converter circuit work together to provide power to the load in a Sigma-type manner. The stacked half-bridge structure inherently halves the input voltage of the Buck converter, thereby increasing the duty cycle and reducing switching stress.

[0064] The proposed Sigma topology based on SHB (stacked half-bridge inverter units) is as follows: Figure 1 As shown. The SHB consists of switching transistors S1~S4, providing AC input voltage to the LLC resonant tank. The resonant slot is formed by a resonant inductor. Resonant capacitor And excitation inductance Composition. The primary-side resonant current is included. With excitation current The difference is converted into secondary current through a transformer with a turns ratio of n:1:1. Subsequently, through synchronous rectifiers SR1 and SR2 and filter capacitors... Processing current, to the load (R) L Power can be delivered. Additionally, extra DC output can be extracted from the midpoint of the SHB. After conversion by the Buck converter, Also for It contributes some power. The Buck converter mainly consists of switching transistors S5 and S6 and an inductor. Composition. (Note) The inductor current is In this configuration, the LLC converter and the Buck converter jointly supply the load in a Sigma type. Moreover, due to the SHB structure, the input voltage of both converters is inherently halved, which facilitates high step-down ratio operation.

[0065] The steady-state operation waveforms of the proposed converter are shown in Fig. 2. The gate drive signals vgs1-vgs4 of the SHB operate at 50% duty ratio with fixed dead-time. The drive signal of S3 (S4) is slightly delayed with respect to S1 (S2) to achieve ZVS in the SHB. The stable output voltage is maintained by adjusting the duty ratio of S5 (S6). One switching cycle can be roughly divided into five stages. The detailed operation process is as follows: Figure 2

[0066] Mode one [t0-t1]: At t0, switch S2 is turned off. During the dead-time, the negative output capacitor C oss1 of S1 is discharged, and the output capacitor C oss2 of S2 is charged. When C oss1 is completely discharged, the body diode of S1 is turned on, and ZVS turn-on (zero voltage switching turn-on) is achieved. Subsequently, as S1 and S4 are simultaneously turned on, the input voltage of the resonant tank becomes , resulting in an increase. At the same time, the magnetizing inductance is clamped, and the magnetizing current linearly rises. At the secondary side, the current gradually increases from zero. The equivalent circuit of this operation mode is shown in Fig. 2(a). Figure 3

[0067] Mode two [t1-t2]: At t1, switch S4 is turned off. becomes positive. C oss4 is charged, and C oss3 is discharged. Similarly, when the body diode of S3 is turned on, S3 achieves ZVS turn-on. During this interval, the ac input voltage decreases to , resulting in a change in its resonant trajectory due to negative excitation. remains clamped, while the secondary current varies in response to . The equivalent circuit of this operation mode is shown in Fig. 2(b). Figure 3

[0068] Mode three [t2-t3]: At t2, the resonant current i Lr decreases to equal the magnetizing current i Lm . However, when remains at​​​​ When the secondary side current drops to zero, the commutation fails, and remains zero in this interval, the primary side stops energy transfer. Therefore, the magnetizing inductance L m is no longer clamped and starts to resonate with L r and C r , thus , until the end of the half cycle at t3: S1 turns off, and the positive i Lr is ready for ZVS turn-on. The equivalent circuit of this mode is shown in Fig. Figure 3 (c).

[0069] Mode four [t3-t4]: In this interval, the Buck converter S5 remains on, and S6 remains off. The inductor current increases linearly with a slope of .

[0070] Mode five [t4-t5]: At t4, the switch S5 turns off, and S6 turns on, resulting in a voltage drop across . Therefore, the inductor current decreases with a slope of .

[0071] For the convenience of those skilled in the art to better understand the technical concept and effect of the present application, the technical solutions and specific embodiments of the application are further described in detail below in conjunction with the drawings and embodiments:

[0072] For simplicity, the effect of phase shift is ignored in the following gain derivation, and the simplified circuit model shown in Fig. Figure 4 is obtained. When the phase shift and dead time effects are ignored, the resonant tank output and alternating square waves with varying amplitudes. Considering that the switching frequency is equal to the resonant frequency of and , and the sum of the voltages remains zero. This square wave voltage is directly applied to the transformer. In addition, according to the turns ratio of the transformer, the following expression holds

[0073] (1)

[0074] In addition, the input voltage of the Buck converter satisfies a certain relationship between the output voltage :

[0075] (2)

[0076] ​In the formula, D is the duty cycle of S5. Substituting (2) into (1) yields the voltage gain M of the converter.

[0077] (3)

[0078] As shown in equation (3), when the transformer turns ratio n is determined, the voltage gain M of the converter can be adjusted by adjusting the duty cycle D of the Buck converter. Furthermore, the total input power is divided into two parts: one part is transferred to the load through the LLC converter, and the other part is transferred to the load through the Buck converter. The power distribution ratio between the LLC converter and the Buck converter can be derived from the following equation:

[0079] (4)

[0080] Performance comparison:

[0081] Traditional Sigma topology, such as Figure 5 As shown, the half-bridge LLC converter and the Buck converter are connected in series-input parallel-output (ISOP) configuration. The corresponding voltage gain and power distribution characteristics are as follows:

[0082] (5)

[0083] (6)

[0084] This represents the voltage gain of a traditional Sigma topology. The turns ratio of transformers in a traditional Sigma topology, This represents the duty cycle of the Buck converter in a traditional Sigma topology; The power distribution ratio between the Buck converter and the LLC converter in a traditional Sigma topology;

[0085] By comparing the voltage gain and power distribution expressions, under the same transformer turns ratio and Buck converter duty cycle, the proposed converter exhibits a lower voltage gain compared to the traditional Sigma topology, but a higher power ratio compared to the Buck converter, which will adversely affect system efficiency. Nevertheless, by achieving n=n c and D=2D c Based on the parameter relationships, the SHB-based Sigma converter can achieve matched voltage gain and power distribution characteristics compared to the traditional topology. Figure 6 The two topologies were compared at n=3 and n cThe voltage gain and power sharing characteristics of the two topologies under the condition of =3 are analyzed. The results show that both topologies maintain the same power sharing characteristics when the gain range constraint is [0.09, 0.12]. However, the proposed topology can make the Buck converter operate in a higher duty cycle range, significantly improving its conversion efficiency.

Claims

1. A high efficient stacked half bridge topology circuit applied to a dynamic load charging pile side, characterized in that, Comprising: a stacked half-bridge inverter unit having input terminals connected to a DC input voltage and output terminals providing a first AC excitation voltage and a second AC excitation voltage of alternating magnitude, wherein a midpoint of the stacked half-bridge inverter unit is connected to a pre-regulated DC voltage node VB; a LLC resonant power transfer unit, having an input connected to the output of the stacked half-bridge inverter unit for receiving the first excitation voltage and the second excitation voltage as a resonant excitation source, efficiently transferring the main power around the resonant frequency, and having an output coupled to the load side via an isolation transformer a partial power regulation unit, whose input is connected to the pre-regulated DC voltage node VB, and whose output is connected in parallel to the output of the LLC resonant power transfer unit to the load, for independently regulating the output voltage and transferring auxiliary power; wherein the stacked half-bridge inverter unit, LLC resonant power transfer unit and partial power regulation unit form a Sigma type power distribution architecture, which collectively provides power to the load.

2. The topology circuit of claim 1, wherein: The stacked half-bridge inverter unit comprises a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4; wherein the source of the S1 is connected with the drain of the S2 to form a first node A, the source of the S3 is connected with the drain of the S4 to form a second node B, and the drain of the S1 is connected to an input voltage positive electrode , the source of the S2 and the source of the S4 are commonly connected to the input voltage negative electrode ; the regulated DC voltage node VB is derived from the connection point of the drain of S3 and the source of S2, and serves as the input voltage source of the Buck converter; An LLC resonant circuit comprises a primary resonant inductance Lr, a resonant capacitance Cr and an excitation inductance as a primary winding of a transformer connected in series , a first end of the LLC resonant circuit being connected to a first node A and a second end being connected to a second node B; The transformer secondary circuit comprises a secondary winding with a turns ratio of n:1:1, two ends of the secondary winding being connected to an output filter capacitor through a first synchronous rectifier SR1 and a second synchronous rectifier SR2 respectively and the load ; Part of the power regulation unit is a Buck converter circuit, including the fifth switch S5, the sixth switch S6, and a Buck inductor. In this configuration, the drain of S5 is connected to the DC voltage node VB, and the source of S5 is connected to the drain of S6 and the inductor. At the first terminal, the source of S6 is connected to the input voltage. negative electrode ,inductance The second terminal is connected to the output filter capacitor. and load ; wherein the stacked half-bridge circuit and the Buck converter circuit collectively provide power to the load in a Sigma type manner, and the stacked half-bridge structure inherently halves the input voltage of the Buck converter, thereby improving the duty cycle and reducing the switching stress.

3. The topology circuit of claim 2, wherein, The first switch tube S1, the second switch tube S2, the third switch tube S3 and the fourth switch tube S4 are respectively connected in parallel with independent buffer capacitors C oss1 , C oss2 , C oss3 , C oss4 .

4. The topology circuit of claim 2, wherein: the stacked half-bridge inverter unit is configured such that the gate drive signals vgs1-vgs4 operate at a fixed duty cycle of 50%, and the drive signals of S3 / S4 are delayed relative to S1 / S2 by a set dead time through phase-shift control.

5. The topological circuit of claim 1, wherein, The input voltage of the buck converter circuit satisfies: The output voltage of the buck converter circuit and the duty cycle satisfies the relationship: .

6. The topological circuit according to any of claims 1-5, characterized by, the stacked half-bridge inverter unit sequentially runs the following five working stages in time order within one complete switching cycle: Phase one ]: At t0, the second switch S2 is off, and in the dead time, the negative resonant current is charged to the output capacitor C oss1 of S1 oss2 ; when C oss1 is discharged, the body diode of S1 is on, realizing zero voltage turn-on; then S1 and S4 are on at the same time, the input voltage of the resonant tank becomes , the resonant current rises, the excitation current is clamped by the output voltage and linearly rises, the secondary current starts from zero and increases, and the energy is transmitted to the load through the transformer; Mode two ] : At time t1, the fourth switch S4 is turned off, and the resonant current... When the value turns positive, the output capacitor C of S4... oss4 Charging, output capacitor C of S3 oss3 Discharge; when C oss3 When the voltage drops to zero, the body diode of S3 conducts, achieving zero-voltage turn-on of S3; at this time Resonant current The resonant trajectory changes due to the decrease in excitation voltage, and the excitation current... Still being Clamping, secondary current Follow The change continues to transfer energy; Stage three ]: exist At that moment, the resonant current Drop to equal to the excitation current Secondary current When the voltage drops to zero, the primary side stops transferring energy to the secondary side; the magnetizing inductor... Disengage from clamping state, and , Free resonance occurs. Continue until At that moment; At that moment, the first switch S1 is turned off, and the forward direction is... Prepare for zero-voltage turn-on of S2; Stage Four ]: The fifth switch S5 keeps on, the sixth switch S6 keeps off, and the Buck inductor current with a slope linearly increases; Stage five ]: The fifth switch S5 is off, the sixth switch S6 is on, and the Buck inductor... The voltage across the terminals is Inductor current With slope Linear decrease.

7. The topology circuit of claim 1, comprising the following steps: The first switch S1 and the second switch S2 are complementary on, the third switch S3 and the fourth switch S4 are complementary on, and the driving signals of S3 / S4 have a phase shift angle φ relative to S1 / S2, the phase shift angle φ is determined by the resonant current The charging and discharging capacity of the switch output capacitor Coss in the dead time determines that the body diode of all switches is turned on before the switch is turned on, and the zero voltage turn-on in the full load range is realized.

8. The control method of a topological circuit according to any one of claims 1, 2, 3, 4, 5, 7, characterized in that, Step 1: control S1 and S2 in the stacked half-bridge inverter unit to be complementary on at a duty cycle of 50%, and S3 and S4 to be complementary on at a duty cycle of 50%, and the drive signals of S3 / S4 are delayed relative to S1 / S2 by a phase-shift angle φ, which is dynamically adjusted according to the load current to maintain zero-voltage turn-on; Step 3: monitor the output current or power distribution ratio, and dynamically adjust the phase-shift angle φ and the duty cycle D to realize power collaborative optimization of the LLC and Buck paths, and maximize the system efficiency. Step 2: Independently adjust the duty cycle D of the fifth switch S5 and / or the sixth switch S6 in the Buck power regulation unit, so that the output voltage is stabilized at the set value; ​

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