Gallium nitride soft-switching high-voltage buck voltage converter

Abstract

The application discloses a gallium nitride soft switch high-voltage Buck voltage converter and belongs to the technical field of switching power supplies. The auxiliary soft switch link is introduced, the problem of large switching loss, high thermal stress, large voltage peak and high-frequency oscillation caused by the switching capacitor link in the traditional high-voltage Buck switching capacitor voltage converter is solved, the efficiency and reliability of the system are improved, further, the double-phase staggered parallel structure is introduced, the current output capacity of the power supply is improved, the application in a higher power scene can be realized, meanwhile, the gallium nitride transistor is adopted, compared with the traditional scheme, the switching frequency is improved, the passive element size is reduced, the PCB integration is improved, the system parasitic parameters are reduced, the dead time and duty cycle loss are reduced, and the system efficiency and power density are further improved.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply technology, specifically relating to a gallium nitride soft-switching high-voltage Buck voltage converter. Background Technology

[0002] Traditional high-voltage Buck converters are widely used in aerospace, specialized equipment, and industrial control power supplies where non-isolated high voltage conversion ratios are required. For example, large commercial airliners, multi-electric aircraft, and small manned aircraft all require switching power supplies that use 270V hydrogen fuel cell stacks to power 28V DC loads. Some of these systems, such as radio and satellite communication systems, flight and engine control systems, instrument panel systems, and lighting systems, do not require electrical isolation. However, with the increasing power and energy efficiency demands of various subsystems, traditional high-voltage Buck converters, when achieving high voltage conversion ratios, suffer from excessively small duty cycles, leading to increased inductor ripple current and losses. This makes them unsuitable for meeting system efficiency requirements under higher power demands.

[0003] To address these issues, researchers proposed adding a switched capacitor stage to the front end of a traditional high-voltage Buck converter. This allows for a larger duty cycle at the same voltage conversion ratio, reducing current peaks and improving system efficiency. However, the reverse recovery current of the diode in the front-end switched capacitor stage increases the switching losses of the main switch, resulting in a limited efficiency improvement. It also increases the thermal stress on the main switch, causing additional voltage spikes and high-frequency oscillations. These are critical problems for aerospace and special equipment with high reliability and EMI (electromagnetic interference) requirements. For these reasons, such switched capacitor voltage converters are rarely used in kilowatt-level switching power supplies in industrial applications. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a gallium nitride soft-switching high-voltage Buck voltage converter. The technical problem to be solved by this invention is achieved through the following technical solution:

[0005] This invention provides a gallium nitride soft-switching high-voltage Buck voltage converter, comprising:

[0006] The system includes an input filter module, a first switched-capacitor Buck module, a second switched-capacitor Buck module, a coupling diode, an auxiliary soft-switching circuit, and an output filter capacitor; among which,

[0007] The input filtering module is used to filter the input voltage, charge the switched capacitors in the first and second switched capacitor Buck modules, and absorb the energy fed back to the input terminal by the auxiliary soft switching circuit.

[0008] The first switched capacitor Buck module is used to step down the bus voltage of the input filter module and output the inductor current of the first phase in zero-voltage mode.

[0009] The second switched capacitor Buck module is used to step down the bus voltage of the input filter module and output the inductor current of the second phase in zero-voltage mode. The inductor current ripples of the first phase and the second phase generate a 180-degree phase difference under interleaved parallel control.

[0010] The coupling diode is used to provide a coupled series charging path for the switched capacitors in the first and second switched capacitor Buck modules, and is reverse cut off during the discharge of the switched capacitors, so that each switched capacitor can supply power to its corresponding switched capacitor Buck module.

[0011] The auxiliary soft-switching circuit is used to generate a pulse current under the control of a control signal. Through a preset pulse width, it discharges the parasitic capacitance of the upper main switch transistor in the first and second switched-capacitor buck modules, achieving zero-voltage turn-on of the upper main switch transistor. Through a preset dead time, it achieves zero-voltage turn-on of the lower main switch transistor in both modules. Simultaneously, it feeds back the energy stored in the upper main switch transistor and the corresponding diode junction capacitance in the switched-capacitor buck modules to the input filter module. All switches in the first, second, and auxiliary soft-switching circuits are gallium nitride transistors.

[0012] The output filter capacitor is used to filter the inductor current output by the first switched capacitor Buck module and the second switched capacitor Buck module connected in parallel, and output a stable DC voltage.

[0013] The beneficial effects of this invention are:

[0014] The solution provided by this invention improves the problems of high switching losses, high thermal stress, large voltage spikes, and high-frequency oscillations caused by the switching capacitor stage in traditional high-voltage Buck switched-capacitor voltage converters by introducing an auxiliary soft-switching stage, thereby enhancing system efficiency and reliability. Furthermore, by introducing a two-phase interleaved parallel structure, the current output capability of the power supply is improved, enabling applications in higher power scenarios. At the same time, by using gallium nitride transistors, the switching frequency is increased compared to traditional solutions, the size of passive components is reduced, PCB integration is improved, system parasitic parameters are reduced, and dead time and duty cycle losses are reduced, further improving system efficiency and power density. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a gallium nitride soft-switching high-voltage Buck voltage converter provided in an embodiment of the present invention;

[0016] Figure 2 A waveform diagram of a gallium nitride soft-switching high-voltage Buck voltage converter in steady-state operation, provided in an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of the working principle of a gallium nitride soft-switching high-voltage Buck voltage converter in the D1T stage within the T / 2 cycle, provided by an embodiment of the present invention.

[0018] Figure 4 This is a schematic diagram of the working principle of a gallium nitride soft-switching high-voltage Buck voltage converter in the D2T stage within the T / 2 cycle, provided in an embodiment of the present invention.

[0019] Figure 5 This is a schematic diagram of the working principle of a gallium nitride soft-switching high-voltage Buck voltage converter in the D3T stage within the T / 2 cycle, provided in an embodiment of the present invention.

[0020] Figure 6 This is a schematic diagram of the working principle of a gallium nitride soft-switching high-voltage Buck voltage converter in the D4T stage within the T / 2 cycle, provided by an embodiment of the present invention.

[0021] Figure 7 This is a schematic diagram of the working principle of a gallium nitride soft-switching high-voltage Buck voltage converter in the D5T stage within the T / 2 cycle, provided in an embodiment of the present invention.

[0022] Figure 8 This is a waveform diagram of a gallium nitride soft-switching high-voltage Buck voltage converter during the D1T~D2T period, provided as an embodiment of the present invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0024] This invention provides a gallium nitride soft-switching high-voltage Buck voltage converter, such as... Figure 1 As shown, it may include:

[0025] The system includes an input filter module, a first switched-capacitor Buck module, a second switched-capacitor Buck module, a coupling diode, an auxiliary soft-switching circuit, and an output filter capacitor; among which,

[0026] The input filtering module is used to filter the input voltage, charge the switched capacitors in the first and second switched capacitor Buck modules, and absorb the energy fed back to the input terminal by the auxiliary soft switching circuit.

[0027] The first switched capacitor Buck module is used to step down the bus voltage of the input filter module and output the inductor current of the first phase in zero-voltage mode.

[0028] The second switched capacitor Buck module is used to step down the bus voltage of the input filter module and output the inductor current of the second phase in zero-voltage mode. The inductor current ripples of the first phase and the second phase generate a 180-degree phase difference under interleaved parallel control.

[0029] The coupling diode is used to provide a coupled series charging path for the switched capacitors in the first and second switched capacitor Buck modules, while being reverse cut off during the discharge of the switched capacitors, so that each switched capacitor can supply power to its corresponding switched capacitor Buck module.

[0030] The auxiliary soft-switching stage generates a pulse current under the control of a control signal. Through a preset pulse width, it discharges the parasitic capacitance of the upper main switch transistor in both the first and second switched-capacitor buck modules, achieving zero-voltage turn-on of the upper main switch transistor. Through a preset dead time, it achieves zero-voltage turn-on of the lower main switch transistor in both modules. Simultaneously, it feeds back the energy stored in the upper main switch transistor and the corresponding diode junction capacitance in the switched-capacitor buck module to the input filter module. All switches in the first, second, and auxiliary soft-switching stages are gallium nitride (GaN) transistors.

[0031] The output filter capacitor is used to filter the inductor current output by the first switched capacitor Buck module and the second switched capacitor Buck module connected in parallel, and output a stable DC voltage.

[0032] This invention presents a gallium nitride (GaN) soft-switching high-voltage Buck converter, which eliminates the adverse effects of the front-end switching capacitor stage on the main switching transistor, reduces switching losses, softens the switching curve, and improves system efficiency, reliability, and EMI performance. Simultaneously, it extends the traditional single-phase topology to two-phase to enhance current output capability and employs a two-phase interleaved parallel control method to reduce the size of input and output filter capacitors. This invention utilizes an all-GaN solution, which, compared to traditional silicon solutions, increases the switching frequency, reduces dead time, lowers system stray inductance and parasitic charge, and further improves system efficiency and power density.

[0033] Input filtering module, such as Figure 1 As shown, it may include:

[0034] Input filter capacitor C in and input inductance L in ;in,

[0035] Input filter capacitor C in The first and second terminals are connected to the positive and negative terminals of the DC input voltage, respectively.

[0036] Input inductance L in The first terminal is connected to the input filter capacitor C in The first end is connected, and the second end serves as the first output end of the input filtering module;

[0037] Input filter capacitor C in The second end serves as the second output end of the input filtering module.

[0038] The input filtering module filters the input voltage, charges the switched capacitors in the first and second switched capacitor Buck modules, and absorbs the energy fed back to the input terminal by the auxiliary soft-switching circuit.

[0039] The first switched-capacitor Buck module, such as Figure 1 As shown, it may include:

[0040] Switching capacitor C1, diode D1, switching transistor S1, switching transistor S2, and inductor L O1 Switch S1 serves as the upper main switch in the first switched capacitor Buck module, and switch S2 serves as the lower main switch in the first switched capacitor Buck module; wherein,

[0041] The first terminal of the switched capacitor C1 serves as the first input terminal of the first switched capacitor Buck module, and the second terminal is connected to the first terminal of the diode D1.

[0042] The first terminal of diode D1 is connected to the first terminal of coupling diode, and the second terminal serves as the second input terminal of the first switched capacitor Buck module.

[0043] The source of switching transistor S1 is connected to the drain of switching transistor S2, and the drain is connected to the first terminal of switching capacitor C1.

[0044] The source of the switching transistor S2 is connected to the second terminal of the diode D1;

[0045] Inductor L O1 The first terminal is connected to the source of the switching transistor S1, and the second terminal is connected to the first terminal of the output filter capacitor.

[0046] The gate of the switching transistor S1 is connected to the control signal V.GS1 The gate of the switching transistor S2 is connected to the control signal V. GS2 .

[0047] Switched capacitor C1 and diode D1 are connected in series to form the first switched capacitor bridge arm; switched transistors S1 and S2 form the first synchronous Buck bridge arm; the neutral point of the first switched capacitor bridge arm is located between switched capacitor C1 and diode D1; the neutral point of the first synchronous Buck bridge arm is located at inductor L. O1 The second terminal is between the source of the switching transistor S1.

[0048] The first switched capacitor Buck module, in zero-voltage mode, steps down the bus voltage of the input filter module and outputs the inductor current of the first phase.

[0049] The second switched-capacitor Buck module, such as Figure 1 As shown, it may include:

[0050] Switching capacitor C2, diode D2, switching transistor S3, switching transistor S4, and inductor L O2 Switch S3 serves as the upper main switch in the second switched capacitor Buck module, and switch S4 serves as the lower main switch in the second switched capacitor Buck module; wherein,

[0051] The first terminal of the switched capacitor C2 serves as the first input terminal of the second switched capacitor Buck module, and the second terminal is connected to the first terminal of the diode D2.

[0052] The first terminal of diode D2 is connected to the second terminal of coupling diode, and the second terminal serves as the second input terminal of the first switched capacitor Buck module.

[0053] The source of switch S3 is connected to the drain of switch S4, and the drain is connected to the first terminal of diode D2.

[0054] The source of the switching transistor S4 is connected to the second terminal of the switching capacitor C2;

[0055] Inductor L O2 The first terminal is connected to the source of the switching transistor S3, and the second terminal is connected to the second terminal of the output filter capacitor.

[0056] The gate of the switching transistor S3 is connected to the control signal V. GS3 The gate of the switching transistor S4 is connected to the control signal V. GS4 .

[0057] The second switched capacitor Buck module, in zero-voltage mode, steps down the bus voltage of the input filter module and outputs the inductor current of the second phase. The inductor current ripple of the first phase and the second phase are generated with a 180-degree phase difference under the interleaved parallel control, thereby achieving the effect of doubling the frequency of the total output ripple current and reducing the size of the required output filter capacitor.

[0058] Switched capacitor C2 and diode D2 are connected in series to form the second switched capacitor bridge arm; switching transistors S3 and S4 form the second synchronous Buck bridge arm; the neutral point of the second switched capacitor bridge arm is located between switched capacitor C2 and diode D2; the neutral point of the second synchronous Buck bridge arm is located at inductor L. O2 The second terminal is between the source of the switching transistor S3.

[0059] Specifically, the first and second switched-capacitor Buck modules form a two-phase interleaved parallel structure. This embodiment of the invention, by introducing a two-phase interleaved parallel structure, improves the current output capability of the power supply, enabling its application in higher power scenarios. Both the first and second switched-capacitor Buck modules use gallium nitride (GaN) transistors as their switching transistors. By using GaN transistors, compared to traditional solutions, the switching frequency is further improved, the size of passive components is reduced, PCB integration is increased, system parasitic parameters are reduced, dead time and duty cycle losses are reduced, and system efficiency and power density are significantly improved.

[0060] The coupling diode provides a coupled series charging path for the switched capacitors in the first and second switched capacitor Buck modules, allowing the bus voltage of the input filter module to charge them simultaneously. At the same time, it is reverse-cut off during the discharge of the switched capacitors, so that each switched capacitor can supply power to its corresponding switched capacitor Buck module.

[0061] Auxiliary soft switching components, such as Figure 1 As shown, it may include:

[0062] Auxiliary diode D aux Auxiliary switch S aux1 Auxiliary switch S aux2 Auxiliary switch S aux3 and pulse inductor L aux ;in,

[0063] Auxiliary diode D aux The first terminal serves as the input terminal of the auxiliary soft-switching circuit, and the second terminal is connected to the auxiliary switch S. aux3 The source and pole are connected;

[0064] Auxiliary switch S aux1The source is used as the first output terminal of the auxiliary soft-switching circuit, and the drain is connected to the pulse inductor L. aux The first end is connected;

[0065] Auxiliary switch S aux2 The source of the circuit serves as the second output terminal of the auxiliary soft-switching circuit, and the drain is connected to the pulse inductor L. aux The first end is connected;

[0066] Auxiliary switch S aux3 The drain and pulse inductor L aux The first end is connected;

[0067] Pulse inductor L aux The second terminal serves as the third output terminal of the auxiliary soft-switching circuit.

[0068] Auxiliary switch S aux1 Gate access control signal V GSaux1 Auxiliary switch S aux2 Gate access control signal V GSaux2 Auxiliary switch S aux3 Gate access control signal V GSaux3 .

[0069] In the auxiliary soft-switching stage, under the control of the control signal, a pulse current is generated. During the dead time before the upper main switch in the first and second switched-capacitor buck modules turns on, the parasitic capacitance of the upper switch is discharged, achieving zero-voltage turn-on of the upper switch. Simultaneously, the energy stored in the upper main switch and the corresponding diode junction capacitance in the switched-capacitor buck module is fed back to the input filter module. For the first switched-capacitor buck module, the upper main switch is S1 and the lower main switch is S2; for the second switched-capacitor buck module, the upper main switch is S3 and the lower main switch is S4.

[0070] Optionally, auxiliary switch S aux1 Auxiliary switch S aux2 Auxiliary switch S aux3 All components use gallium nitride transistors with small package size and high-speed switching capability. In PCB design, they can be placed close to the main switching transistor to assist the main switching transistor in completing zero-voltage turn-on more quickly, while reducing the additional losses introduced by the auxiliary switching circuit.

[0071] Understandably, the embodiments of the present invention improve the efficiency and reliability of traditional high-voltage Buck switched-capacitor voltage converters by introducing an auxiliary soft-switching stage, which addresses the problems of high device switching losses, high thermal stress, large voltage spikes and high-frequency oscillations caused by the switching capacitor stage.

[0072] The waveform diagram of a gallium nitride soft-switching high-voltage Buck voltage converter during steady-state operation provided in this embodiment of the invention is as follows: Figure 2 As shown, the following will be combined with Figure 2 The circuit principle of this gallium nitride soft-switching high-voltage Buck voltage converter is explained.

[0073] Figure 2 The diagram shows the switching transistors S1, S2, S3, and S4 in the first and second switched-capacitor Buck modules, as well as the auxiliary switching transistor S in the auxiliary soft-switching circuit. aux1 S aux2 S aux3 The control signal corresponding to the gate, the drain-source voltage waveforms corresponding to the switching transistors S1 and S2 in the first switched capacitor Buck module, and the input inductor L in and inductor L O1 The voltage and current waveforms; among which, the auxiliary switch S aux1 S aux2 The duty cycle of each is K1. The duty cycle of switches S1 and S3 is K2+K3, and the duty cycle of switches S2 and S4 is K5. K1 represents the first parameter, K2 represents the second parameter, K3 represents the third parameter, K4 represents the fourth parameter, and K5 represents the fifth parameter. T is the switching period. The dead time of the first synchronous Buck bridge arm and the second synchronous Buck bridge arm is (K1+K4)T.

[0074] The working principle diagram of a gallium nitride soft-switching high-voltage Buck voltage converter provided in this embodiment of the invention at various stages within the T / 2 cycle is as follows: Figures 3-7 As shown, the black part represents the device that is conducting and has current flowing through it during this stage, and the gray part represents the device that is not conducting current during this stage.

[0075] Specifically, the working principle diagram of the K1T stage is as follows: Figure 3 As shown, at this time, the auxiliary switch S aux1 On, input inductor L in Simultaneously serving as auxiliary inductor L aux And the charging of switched capacitors C1 and C2, and the pulse inductor L aux Current I Laux The linear rise creates the conditions for zero-voltage turn-on of switches S1 and S3, the specific circuit principles and calculation methods of which will be discussed in detail later. Auxiliary switch S... aux1 It conducts in zero-current mode, so no switching losses are generated. At this time, the first switched capacitor Buck module is in dead time, and the inductor L... O1 Freewheeling occurs through the body diode of the switching transistor S2.

[0076] The working principle diagram of the K2T stage, as follows: Figure 4As shown, at this time, the auxiliary switch S aux3 On, S aux1 Off, pulse inductor L aux The energy stored on it is transmitted through the auxiliary diode D aux3 Feedback is sent back to the input terminal, and simultaneously, the switching transistor S1 is soft-turned under zero-voltage conditions. Switching capacitors C1 and C2 act as inductors L through diodes D1 and D2. O1 Charging, output inductor current ripple V in (K2+K3+K4)T / 2L O1 Because the first and second switched-capacitor Buck modules are controlled in a two-phase interleaved manner, S3 lags behind S1 by 180 degrees in phase, and the inductor L... O2 Continue freewheeling through switch S4.

[0077] The working principle diagram of the K3T stage is as follows: Figure 5 As shown, at this time, the pulse inductor L aux All energy feedback is complete, auxiliary switch S aux3 In zero-current mode, the switch is turned off without incurring switching losses. The operation of the first and second switched-capacitor Buck modules is the same as in the previous stage.

[0078] The working principle diagram of the K4T stage is as follows: Figure 6 As shown, at this time, switch S1 is turned off, the first switched capacitor Buck module enters the dead time, and inductor L... O1 The junction capacitances of switching transistors S1 and S2 are charged and discharged. The voltage across S1 rises slowly due to the buffering effect of the junction capacitance, thus achieving soft turn-off.

[0079] The working principle diagram of the K5T stage, such as Figure 7 As shown, at this time, switch S2 is turned on, and inductor L... O1 With S2 freewheeling, the junction capacitance of S2 is now fully discharged, enabling it to turn on in zero-voltage mode. The input inductor L... in The switching capacitors C1 and C2 are charged through the coupling diode D3, and the current ripple of the input inductor is 2V. o K5T / L in At this time, the switching capacitors C1 and C2 are in series, and the drain-source voltage of the switching transistors S1 and S3 is approximately equal to the sum of the voltages of the two switching capacitors.

[0080] During the remaining T / 2 cycles, the second switched-capacitor Buck module repeats the operating state of the first switched-capacitor Buck module during K1T-K5T in the same mode. It should be noted that, since the two switched-capacitor Buck modules are connected in parallel, when the switching transistor S3 in the second switched-capacitor Buck module is turned on, its drain-source voltage will change even though S1 is in the gate-off state. Figure 2 During the period T / 2-T, the drain-source voltage V of S1 DS1 As shown.

[0081] When the switching transistor S1 in the first switched-capacitor Buck module is in a hard-switching state, current spikes occur due to the body diode of the switching transistor S2 and the reverse recovery of the diodes, increasing switching losses and generating high-frequency oscillations and EMI noise. In this embodiment of the invention, an auxiliary switching stage is used to discharge the junction capacitance of S2 and diodes D1, D2, and D3 before the switching transistor S1 is turned on. This causes the voltage across S1 to drop to zero before the conduction channel opens, achieving zero-voltage turn-on, reducing switching losses, softening the switching curve, and improving EMI performance. Similarly, zero-voltage turn-on and soft turn-off can be achieved for S3 in the second switched-capacitor Buck module.

[0082] Under the control of the control signal, the auxiliary soft-switching circuit generates a pulse current. Through a preset pulse width, it discharges the parasitic capacitance of the upper main switch in the first and second switched capacitor buck modules, thereby achieving zero-voltage turn-on of the upper main switch. Through a preset dead time, it achieves zero-voltage turn-on of the lower main switch in the first and second switched capacitor buck modules.

[0083] The preset pulse width includes K1T and K2T, and the preset dead time includes K1T and K4T; where K1T=T1+T2+T3+T4, K2T=T5+T6, K1 represents the first parameter, K2 represents the second parameter, K4 represents the fourth parameter, and T represents the switching period.

[0084] T1 indicates the first time, L aux I represents the inductance value of the pulse inductor. Lin V represents the current in the input inductor. in This represents the voltage at which the input inductor is located, V. o This indicates the voltage across the output filter capacitor;

[0085] ;

[0086] T2 indicates the second time. This represents the resonant parasitic capacitance coefficient during period T2. I LO1 This represents the output inductor current of the first switched-capacitor buck module; ;

[0087] T3 indicates the third time. and This represents the resonant parasitic capacitance coefficient during period T3. I represents the voltage across the pulse inductor at the end of period T2. Laux This represents the current in the pulse inductor;

[0088] T4 indicates the fourth time period. This represents the resonant parasitic capacitance coefficient during period T4;

[0089] T5 indicates the fifth time period. This represents the current in the pulse inductor at the end of period T4;

[0090] T6 indicates the sixth time. This represents the output inductor current of the first switched capacitor buck module.

[0091] The waveform diagram of a gallium nitride soft-switching high-voltage Buck voltage converter during the K1T~K2T period provided in this embodiment of the invention is as follows: Figure 8 As shown, the following will be combined with Figure 8 For auxiliary switching transistor S aux1 S aux2 S aux3 The method for setting the switching timing is explained. In actual design, the corresponding pulse widths K1T and K2T need to be set according to the specific parameters of the circuit and the specifications of each device to achieve zero-voltage conduction of switching transistors S1 and S3. At the same time, an appropriate dead time K4T also needs to be set to achieve zero-voltage conduction of switching transistors S2 and S4.

[0092] ;

[0093] in, This represents the junction capacitance of the main switch transistor S2.

[0094] Figure 8 The waveforms of the circuit during K1T and K2T on the extended time axis are shown, including the gate signal V of the switching transistor. GS1 With V GS2 The voltage V of the pulse inductor Laux The current I of the pulse inductor Laux The drain-source voltage V of the switching transistor S1 DS1 The drain-source voltage V of S2 DS2 Auxiliary switch S aux1 Drain-source voltage V DSaux1 Auxiliary switch S aux3 Drain-source voltage V DSaux3 .

[0095] Specifically, before the switching transistor S1 is turned on, the first switched capacitor Buck module is in the dead time, and the auxiliary switching transistor S1 is turned on. aux1The duty cycle is K1, and the circuit operation can be divided into four stages: T1-T4. During T1, as S... aux1 On, pulse inductor L aux As charging begins, the current increases linearly with a slope of (V). in +2V o ) / L aux At this point, the auxiliary switching circuit is in the energy storage stage and has not yet acted on the main circuit. This stage continues until the current I of the pulse inductor reaches its maximum. Laux Equal to the current I of the input inductor Lin Up to this point, the expression for its first time step T1 is as follows:

[0096] .

[0097] During T2, as the current I of the pulse inductor... Laux Current I exceeding the input inductance Lin The junction capacitance C of diode D1 oss_D1 The junction capacitance C of diode D2 oss_D2 The junction capacitance C of diode D3 oss_D3 The junction capacitance C of the switching transistor S1 oss_S1 The junction capacitance C of the switching transistor S3 oss_S3 Start with pulse inductor L aux At resonance, switch S2 remains in a state where the body diode is turned on and the drain-source voltage is clamped. The characteristic equation of the resonant circuit at this time is expressed as follows:

[0098] ;

[0099] in This represents the resonant parasitic capacitance coefficient during period T2. This represents the current in the pulse inductor at time t.

[0100] The general solution expression of the characteristic equation is as follows:

[0101] ;

[0102] Where X and Y represent the general solution constants, the initial conditions of the circuit in this stage are as follows;

[0103] ;

[0104] ;

[0105] Substituting the initial conditions, we can obtain the current I of the pulse inductor. Laux With voltage V Laux The expression is as follows:

[0106] ;

[0107] ;

[0108] in, This represents the voltage of the pulse inductor at time t.

[0109] This stage is defined as: the current I to the pulse inductor. Laux Equal to the current I of the output inductor LO1 End, that is:

[0110] ;

[0111] Substituting into the above expression for pulse inductor current, we get:

[0112] ;

[0113] The expression for the second time T2 in this stage can be obtained by solving as follows:

[0114] .

[0115] Substitute T2 into the aforementioned expression for the voltage of the pulse inductor. The voltage of the pulse inductor at the end of this phase can be obtained. .

[0116] During T3, as the current I of the pulse inductor... Laux Current I exceeding the output inductor LO1 When the neutral point current of the synchronous Buck bridge arm begins to reverse, the current I of the output inductor... LO1 Stop the freewheeling current from the body diode of S2. At this time, the switching transistor S2 and the auxiliary switching transistor S2 are connected. aux2 The junction capacitance also begins to participate in resonance, and the parasitic resonance capacitance C at this stage... oss_T3 Including: the junction capacitance C of the diode oss_D1 C oss_D2 C oss_D3 The junction capacitance C of the switching transistor oss_S1 C oss_S2 C oss_S3 The junction capacitance C of the auxiliary switching transistor oss_Saux2 .

[0117] Solve the characteristic equation using the same method as described above, and substitute the initial conditions. The current of the pulse inductor can be obtained. With voltage The expression is as follows:

[0118] ;

[0119] ;

[0120] Among them, coefficient ; .

[0121] This stage is defined as: the voltage to the pulse inductor. This is equal to the end of the switched capacitor voltage, that is:

[0122] ;

[0123] in, This represents the voltage of the pulse inductor at the end of period T3.

[0124] Substitute into the aforementioned expression for the voltage of the pulse inductor The expression for the third time T3 in this stage can be obtained as follows:

[0125] ;

[0126] in, This represents the voltage of the pulse inductor at the end of period T2.

[0127] During T4, the diodes complete their state transition: D1 and D2 are on, D3 is off, their junction capacitance and the pulse inductor resonance end, and the voltage clamping of the synchronous Buck bridge arm is reduced to V. in / 2+V o The resonant parasitic capacitance C at this stage oss_T4 The junction capacitance C of the switching transistor oss_S1 C oss_S2 C oss_S3 The junction capacitance C of the auxiliary switching transistor oss_Saux2 The sum of these values, and the voltage V of the inductor at the end of this phase. Laux The voltage V across the switching transistor S1 DS1 When the voltage drops to zero, the voltage across S2 rises to V. in / 2+V o At this point, the zero-voltage conduction condition of S1 is met.

[0128] Solve the characteristic equation using the same method as described above, and then substitute the initial conditions. ;

[0129] The current of the pulse inductor can be obtained. With voltage The expression is as follows:

[0130] ;

[0131] ;

[0132] The resonant parasitic capacitance coefficient during T4 is as follows:

[0133] .

[0134] This stage is defined as: the voltage V to the pulse inductor. Laux The resonance ends at the zero-crossing point, that is:

[0135] ;

[0136] in, This represents the voltage of the pulse inductor during period T4.

[0137] Substitute the voltage of the pulse inductor mentioned above From the expression, we can obtain the expression for the fourth time point T4 in this stage as follows:

[0138] .

[0139] When the auxiliary inductor voltage resonates to zero, the auxiliary switch S is turned off. aux1 Turn on auxiliary switch S aux3 Pulse inductor L aux Discharge and feed energy back to the input, assisting the switching transistor S. aux3 Turning on under zero-current conditions, without incurring switching losses, the current in the pulse inductor decreases linearly during this stage at a rate of (V). in / 2-V o ) / Laux It should be noted that the switching transistor S1 needs to be in the pulse inductor current I Laux The current I drops to the output inductor LO1 The circuit must be turned on during time T5; otherwise, the output inductor will charge the S1 junction capacitor again, preventing it from turning on at zero voltage. The expression for the fifth time period T5 is as follows:

[0140] .

[0141] When the switching transistor S1 is turned on during period T5, the switched capacitor initially becomes the inductor L. O1 During charging, the circuit enters Buck operating mode, and the auxiliary switching transistor S... aux3 The conduction time is K2T = T5 + T6. During T6, the inductor energy is fully released, and the auxiliary switching circuit ends its operation. The expression for the sixth time T6 is as follows:

[0142] ;

[0143] Since the two half-bridge arms in the first and second switched-capacitor Buck modules are controlled by interleaved parallel connection, the auxiliary switching transistor S is set with the same duty cycle D1 and D2 in the second half-cycle. aux2 and S aux3 This allows for zero-voltage turn-on of the switching transistor S3.

[0144] Based on the above circuit analysis, it can be seen that, by introducing an auxiliary switching element and reasonably setting the auxiliary switching timing and dead time, this embodiment of the invention can achieve zero-voltage turn-on and soft turn-off of switch S1, zero-voltage turn-on and zero-current turn-off of switch S2, and zero-voltage turn-on of switches S3 and S4. This is achieved through the auxiliary switching element S... aux1 With S aux2 Zero-current turn-on, auxiliary switch S aux3 Zero-voltage turn-on and zero-current turn-off essentially eliminate all switching losses in the circuit.

[0145] In this invention, the switching transistors in the first switched-capacitor Buck module, the second switched-capacitor Buck module, and the auxiliary soft-switching stage all employ gallium nitride (GaN) transistors. The low junction capacitance of GaN devices significantly shortens the dead time K1T and K4T required for soft switching, reducing conduction losses caused by circulating current during the dead time and lowering duty cycle losses, thus improving system efficiency. Secondly, since each switching transistor in the circuit has almost no switching losses, using GaN devices with low on-resistance can significantly reduce the heat dissipation requirements. Furthermore, because this invention has almost no switching losses, it has a high switching frequency, making it particularly suitable for high-frequency, high-integration switching power supply designs based on GaN, thereby improving system power density.

[0146] Through the above explanation, those skilled in the art should have a corresponding understanding of the circuit working principle of the embodiments of the present invention. The following section will specifically introduce the design of various system parameters under the rated input power of 1.2kW, rated input voltage of 270V, and rated output voltage of 28V of the embodiments of the present invention.

[0147] Based on the design formulas for K1, K2, and K4 and the parameters in the switching transistor datasheet, the auxiliary switching transistor S is selected. aux1 S aux2 Duty cycle K1 = 0.01, auxiliary switch S aux3 The duty cycle K2 = 0.05, and the dead-time duty cycle K4 = 0.03 before the main switches S2 and S4 are turned on. According to the duty cycle formula, the output inductor volt-second balance yields K3 = 0.092 and K5 = 0.5 - (K1 + K2 + K3 + K4) = 0.318. The duty cycles of switches S1 and S3 are K2 + K3 = 0.169, and the duty cycles of S2 and S4 are K1 + K5 = 0.319. The switching frequency is selected as 200kHz, and the switching period is 5μs.

[0148] The current I of the input inductor Lin for:

[0149] ;

[0150] Among them, P in This indicates the power of the input inductor.

[0151] Based on a 30% ripple design for the input inductor current, the inductance value L of the input inductor is... in for:

[0152] ;

[0153] Designed with a system efficiency of 95%, the current of the single-phase output inductor... for:

[0154] ;

[0155] in, This indicates system efficiency.

[0156] Based on the 20% ripple design of the output inductor current, the output inductor value L O1 L O2 for:

[0157] ;

[0158] Through the auxiliary switching transistor S aux1 S aux3 The inductance value L of the pulse inductor can be determined by the duty cycles K1 and K2. aux =0.17μH. The selection of the pulse inductor value needs to be combined with the junction capacitance of the selected device to ensure that all resonant cycles can be completed within K1T, while the inductor energy can be reset within K2T, and the peak value of the resonant current at the end of the T2 stage exceeds the current I of the output inductor. LO1 This is to complete the discharge of the junction capacitance of the main switch transistors S1 and S3.

[0159] Input filter capacitor C in Switching capacitors C1 and C2, output capacitor C o All are designed with voltage ripple not exceeding 1%, specifically:

[0160] ;

[0161] ;

[0162] .

[0163] This invention improves the efficiency and reliability of traditional high-voltage Buck switched-capacitor voltage converters by introducing an auxiliary soft-switching stage, which addresses the problems of high switching losses, high thermal stress, large voltage spikes, and high-frequency oscillations caused by the switching capacitor stage. Furthermore, the introduction of a two-phase interleaved parallel structure enhances the power supply's current output capability, enabling applications in higher power scenarios. Simultaneously, the use of gallium nitride transistors further increases the switching frequency compared to traditional solutions, reduces the size of passive components, improves PCB integration, lowers system parasitic parameters, and reduces dead time and duty cycle losses, further enhancing system efficiency and power density.

[0164] It should be noted that, in the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0165] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A gallium nitride soft-switching high-voltage Buck voltage converter, characterized in that, include: The system includes an input filter module, a first switched-capacitor Buck module, a second switched-capacitor Buck module, a coupling diode, an auxiliary soft-switching circuit, and an output filter capacitor; among which, The input filtering module is used to filter the input voltage, charge the switched capacitors in the first and second switched capacitor Buck modules, and absorb the energy fed back to the input terminal by the auxiliary soft switching circuit. The first switched capacitor Buck module is used to step down the bus voltage of the input filter module and output the inductor current of the first phase in zero-voltage mode. The second switched capacitor Buck module is used to step down the bus voltage of the input filter module and output the inductor current of the second phase in zero-voltage mode. The inductor current ripples of the first phase and the second phase generate a 180-degree phase difference under interleaved parallel control. The coupling diode is used to provide a coupled series charging path for the switched capacitors in the first and second switched capacitor Buck modules, and is reverse cut off during the discharge of the switched capacitors, so that each switched capacitor can supply power to its corresponding switched capacitor Buck module. The auxiliary soft-switching circuit is used to generate a pulse current under the control of a control signal. Through a preset pulse width, it discharges the parasitic capacitance of the upper main switch transistor in the first and second switched-capacitor buck modules, achieving zero-voltage turn-on of the upper main switch transistor. Through a preset dead time, it achieves zero-voltage turn-on of the lower main switch transistor in both modules. Simultaneously, it feeds back the energy stored in the upper main switch transistor and the corresponding diode junction capacitance in the switched-capacitor buck modules to the input filter module. The switching transistors in the first, second, and auxiliary soft-switching modules are all gallium nitride transistors. The auxiliary soft-switching circuit includes: Auxiliary diode D aux Auxiliary switch S aux1 Auxiliary switch S aux2 Auxiliary switch S aux3 and pulse inductor L aux ;in, The auxiliary diode D aux The first terminal serves as the input terminal of the auxiliary soft-switching circuit, and the second terminal is connected to the auxiliary switching transistor S. aux3 The source and pole are connected; The auxiliary switching transistor S aux1 The source of the circuit serves as the first output terminal of the auxiliary soft-switching circuit, and the drain is connected to the pulse inductor L. aux The first end is connected; The auxiliary switching transistor S aux2 The source of the circuit serves as the second output terminal of the auxiliary soft-switching circuit, and the drain is connected to the pulse inductor L. aux The first end is connected; The auxiliary switching transistor S aux3 The drain of the pulse inductor L aux The first end is connected; The pulse inductor L aux The second terminal serves as the third output terminal of the auxiliary soft-switching circuit; The output filter capacitor is used to filter the inductor current output by the first switched capacitor Buck module and the second switched capacitor Buck module connected in parallel, and output a stable DC voltage.

2. The gallium nitride soft-switching high-voltage Buck voltage converter according to claim 1, characterized in that, The input filtering module includes: Input filter capacitor C in and input inductance L in ;in, The input filter capacitor C in The first and second terminals are connected to the positive and negative terminals of the DC input voltage, respectively. The input inductance L in The first terminal is connected to the input filter capacitor C in The first end is connected, and the second end serves as the first output end of the input filtering module; The input filter capacitor C in The second end serves as the second output end of the input filtering module.

3. A gallium nitride soft-switching high-voltage Buck voltage converter according to claim 1, characterized in that, The first switched capacitor Buck module and the second switched capacitor Buck module form a two-phase interleaved parallel structure.

4. A gallium nitride soft-switching high-voltage Buck voltage converter according to claim 1, characterized in that, The first switched-capacitor Buck module includes: Switching capacitor C1, diode D1, switching transistor S1, switching transistor S2, and inductor L O1 Switch S1 serves as the upper main switch in the first switched capacitor Buck module, and switch S2 serves as the lower main switch in the first switched capacitor Buck module; wherein, The first terminal of the switched capacitor C1 serves as the first input terminal of the first switched capacitor Buck module, and the second terminal is connected to the first terminal of the diode D1. The first end of diode D1 is connected to the first end of coupling diode, and the second end serves as the second input end of the first switched capacitor Buck module. The source of the switching transistor S1 is connected to the drain of the switching transistor S2, and the drain is connected to the first terminal of the switching capacitor C1. The source of the switching transistor S2 is connected to the second terminal of the diode D1; The inductor L O1 The first end is connected to the source of the switching transistor S1, and the second end is connected to the first end of the output filter capacitor.

5. A gallium nitride soft-switching high-voltage Buck voltage converter according to claim 4, characterized in that, The switched capacitor C1 and diode D1 are connected in series to form the first switched capacitor bridge arm; the switched transistors S1 and S2 form the first synchronous Buck bridge arm; the neutral point of the first switched capacitor bridge arm is located between the switched capacitor C1 and diode D1; the neutral point of the first synchronous Buck bridge arm is located at the inductor L. O1 The second terminal is between the source of the switching transistor S1.

6. A gallium nitride soft-switching high-voltage Buck voltage converter according to claim 1, characterized in that, The second switched-capacitor Buck module includes: Switching capacitor C2, diode D2, switching transistor S3, switching transistor S4, and inductor L O2 Switch S3 serves as the upper main switch in the second switched capacitor Buck module, and switch S4 serves as the lower main switch in the second switched capacitor Buck module; wherein, The first terminal of the switched capacitor C2 serves as the first input terminal of the second switched capacitor Buck module, and the second terminal is connected to the first terminal of the diode D2. The first end of diode D2 is connected to the second end of coupling diode, and the second end serves as the second input end of the first switched capacitor Buck module. The source of the switching transistor S3 is connected to the drain of the switching transistor S4, and the drain is connected to the second terminal of the diode D2. The source of the switching transistor S4 is connected to the first terminal of the switching capacitor C2; The inductor L O2 The first end is connected to the source of the switching transistor S3, and the second end is connected to the second end of the output filter capacitor.

7. A gallium nitride soft-switching high-voltage Buck voltage converter according to claim 6, characterized in that, The switched capacitor C2 and diode D2 are connected in series to form the second switched capacitor bridge arm; the switched transistors S3 and S4 form the second synchronous Buck bridge arm; the neutral point of the second switched capacitor bridge arm is located between the switched capacitor C2 and diode D2; the neutral point of the second synchronous Buck bridge arm is located at the inductor L. O2 The second terminal is between the source of the switching transistor S3.

8. A gallium nitride soft-switching high-voltage Buck voltage converter according to claim 1, characterized in that, The preset pulse width includes K1T and K2T, and the preset dead time includes K1T and K4T; where K1T=T1+T2+T3+T4, K2T=T5+T6, K1 represents the first parameter, K2 represents the second parameter, K4 represents the fourth parameter, and T represents the switching period. T1 indicates the first time, L aux I represents the inductance value of the pulse inductor. Lin V represents the current in the input inductor. in This represents the voltage at which the input inductor is located, V. o This indicates the voltage across the output filter capacitor; ； T2 indicates the second time. I represents the resonant parasitic capacitance coefficient during period T2. LO1 This represents the output inductor current of the first switched-capacitor buck module; ； T3 indicates the third time. and This represents the resonant parasitic capacitance coefficient during period T3. I represents the voltage across the pulse inductor at the end of period T2. Laux This represents the current in the pulse inductor; T4 indicates the fourth time period. This represents the resonant parasitic capacitance coefficient during period T4; T5 indicates the fifth time period. This represents the current in the pulse inductor at the end of period T4; T6 indicates the sixth time. This represents the output inductor current of the first switched-capacitor buck module; ; This represents the junction capacitance of the switching transistor S2.

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