Gallium nitride hybrid switched capacitor voltage converter with high step-down ratio

Abstract

The invention discloses a gallium nitride hybrid switched capacitor voltage converter with a high step-down ratio, which belongs to the technical field of switching power supplies and comprises an input filtering module, a switched capacitor module group, a half-bridge module group and an output filtering module which are connected in sequence, the switched capacitor module group comprises a plurality of switched capacitor modules which are connected in parallel, the half-bridge module group comprises a plurality of half-bridge modules which are connected in parallel, and the switched capacitor modules and the half-bridge modules are in one-to-one correspondence and work in corresponding preset switching periods; the output filtering module comprises a plurality of output filtering inductors, and the output filtering inductors are correspondingly connected with the half-bridge modules. Through innovation of the topological structure, the buck ratio higher than that of a traditional Buck converter under the same duty ratio is achieved, input current and output voltage ripples are further improved through a multi-phase interleaving parallel control mode, wide bandgap devices are reasonably selected for the innovatively-designed topological structure, and therefore the output current and output voltage ripples are improved. And the circuit is more suitable for kilowatt-level switching power supply equipment.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply technology, specifically relating to a gallium nitride hybrid switched capacitor voltage converter with a high step-down ratio. Background Technology

[0002] With the development of electric vehicles, photovoltaic energy storage, communications, and data centers, the demands for power density, size, and voltage conversion ratio of switching power supply equipment are also increasing. For example, L2+ intelligent driving systems, auxiliary drive systems, and turbocharging systems in new energy vehicles all require switching power supplies with power outputs exceeding kilowatts and capable of achieving high voltage conversion ratios from high-voltage battery packs to the 48V bus. Compared to traditional silicon-based devices, switching power supplies based on gallium nitride (GaN) power devices can achieve higher switching frequencies, thereby reducing equipment size and increasing energy density.

[0003] However, under high power and high buck ratio conditions, traditional Buck converters have large peak-to-peak current due to the reduced duty cycle, which increases the size and loss of magnetic components and affects the power density, efficiency, control system complexity, electromagnetic compatibility performance and cost of the switching power supply. These problems are even more pronounced in high-frequency kilowatt-level switching power supply equipment using gallium nitride power devices. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a gallium nitride hybrid switched-capacitor voltage converter with a high step-down ratio. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a gallium nitride hybrid switched-capacitor voltage converter with a high step-down ratio. The high-step-down gallium nitride hybrid switched-capacitor voltage converter includes: an input filter module, a switched-capacitor module group, a half-bridge module group, and an output filter module connected in sequence. The switched-capacitor module group includes several switched-capacitor modules connected in parallel, and the half-bridge module group includes several half-bridge modules connected in parallel. Each switched-capacitor module corresponds to one half-bridge module and operates within a corresponding preset switching cycle. The output filter module includes several output filter inductors, which are connected to corresponding half-bridge modules. The input filtering module is used to filter the high-frequency components in the DC input voltage; Each switched capacitor module is used to control the cut-off and conduction of multiple diodes in the switched capacitor module, thereby changing the charging and discharging state of each switched capacitor in the switched capacitor module during the corresponding preset switching cycle, so as to realize the control of the bus voltage of the corresponding half-bridge module and the first voltage conversion of the filtered DC input voltage; wherein, all diodes in each switched capacitor module are silicon carbide diodes. Each half-bridge module is used to perform a second voltage conversion on the bus voltage of the half-bridge module by controlling the switching transistors in the half-bridge module to turn them on and off. At the same time, each half-bridge module is connected in parallel with a 90-degree phase shift to output a high-frequency chopper voltage with a multiplied frequency, so as to reduce the size requirements of the output filter module. All the switching transistors in each half-bridge module are gallium nitride transistors. The output filtering module is used to filter the high-frequency chopped voltage output by each half-bridge module to output a DC voltage with low ripple.

[0005] The beneficial effects of this invention are: This invention proposes a gallium nitride hybrid switched-capacitor voltage converter with a high step-down ratio. Through innovative topology, it achieves a higher step-down ratio than traditional Buck converters at the same duty cycle, reduces inductor current di / dt, lowers control system requirements, and improves power supply efficiency. Furthermore, multi-phase interleaved parallel control further improves input current and output voltage ripple, reduces the size of input and output filter inductors and capacitors, and increases the power density and current output capability of the power supply. This makes it suitable for switching power supply devices requiring high step-down ratio, high energy density, and high power. The innovative topology design also rationally selects wide-bandgap devices, reducing switching losses caused by parasitic charges in traditional silicon solutions, further improving system efficiency and making it more suitable for kilowatt-level switching power supply devices.

[0006] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of a gallium nitride hybrid switched capacitor voltage converter with a high step-down ratio provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the first voltage conversion from input DC voltage to half-bridge module bus voltage of the gallium nitride hybrid switched capacitor voltage converter with high step-down ratio provided in the embodiment of the present invention; Figure 3 This is a schematic diagram of the specific circuit structure of the gallium nitride hybrid switched capacitor voltage converter with high step-down ratio provided in the embodiment of the present invention; Figure 4 This is a waveform diagram of a gallium nitride hybrid switched capacitor voltage converter with high step-down ratio provided in an embodiment of the present invention during steady-state operation. Figure 5 This is a schematic diagram comparing the buck ratio and duty cycle of a traditional Buck converter and the converter proposed in this invention. Figure 6The gallium nitride hybrid switched capacitor voltage converter with high step-down ratio provided in this embodiment of the invention operates from 0 to DT. S A waveform diagram of the switching transient during the period; Figures 7(a) to 7(g) The gallium nitride hybrid switched capacitor voltage converter with high step-down ratio provided in this embodiment of the invention operates from 0 to DT. S Equivalent circuit diagrams for each sub-stage during the period. Detailed Implementation

[0008] 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.

[0009] Please see Figure 1 This invention provides a gallium nitride hybrid switched-capacitor voltage converter with a high step-down ratio. The high-step-down gallium nitride hybrid switched-capacitor voltage converter includes: an input filter module, a switched-capacitor module group, a half-bridge module group, and an output filter module connected in sequence. The switched-capacitor module group includes several switched-capacitor modules connected in parallel, and the half-bridge module group includes several half-bridge modules connected in parallel. Each switched-capacitor module corresponds to one half-bridge module and operates within a corresponding preset switching cycle. The output filter module includes several output filter inductors, which are connected to corresponding half-bridge modules. The input filtering module is used to filter the high-frequency components in the DC input voltage; Each switched capacitor module is used to control the cutoff and conduction of multiple diodes within the module, thereby changing the charging and discharging state of each switched capacitor within a corresponding preset switching cycle. This achieves control over the bus voltage of the corresponding half-bridge module and the first voltage conversion of the filtered DC input voltage. Figure 2 As shown; in each switched capacitor module, all diodes are silicon carbide diodes; Each half-bridge module is used to perform a second voltage conversion on the bus voltage of the half-bridge module by controlling the switching transistors in the half-bridge module to turn them on and off. At the same time, each half-bridge module is connected in parallel with a 90-degree phase shift to output a high-frequency chopper voltage with a multiplied frequency, so as to reduce the size requirements of the output filter module. All the switching transistors in each half-bridge module are gallium nitride transistors. The output filtering module is used to filter the high-frequency chopped voltage output by each half-bridge module to output a DC voltage with low ripple.

[0010] Next, each module in the gallium nitride hybrid switched-capacitor voltage converter with a high step-down ratio will be described in detail.

[0011] In this embodiment of the invention, the input filtering module is as follows: Figure 3As shown, it includes the input filter inductor L in Input filter capacitor C in Among them, the input filter capacitor C in The two ends serve as the input terminals of the input filter module, and are respectively connected to the DC input voltage V. in The positive and negative terminals are connected, and the input filter inductor L... in The two ends are respectively connected to the DC input voltage V in The positive terminal is connected to each switched capacitor module.

[0012] In this embodiment of the invention, the circuit structure of each switched capacitor module is identical; each capacitor switching module is as follows: Figure 3 As shown, it includes a forearm switched capacitor, a forearm diode, a rear arm switched capacitor, a rear arm diode, and an inter-arm diode; wherein, one end of the rear arm switched capacitor is connected to the cathode of the rear arm diode and the input filter module, the other end of the rear arm switched capacitor is connected to the cathode of the forearm diode and the anode of the inter-arm diode, the anode of the rear arm diode is connected to the cathode of the inter-arm diode and one end of the forearm switched capacitor, and the anode of the forearm diode is connected to the other end of the forearm switched capacitor and the DC input voltage V. in The negative terminal is connected. Figure 3 Four switched capacitor modules are illustrated. They have the same circuit structure. For ease of description, the components in the four switched capacitor modules are labeled with different identifiers. For example, the first switched capacitor module includes the forearm switched capacitor C. L1 Forearm diode D L1 Rear arm switched capacitor C H1 Rear arm diode D H1 Inter-arm diode D M1 The fourth switched capacitor module includes the forearm switched capacitor C. L4 Forearm diode D L4 Rear arm switched capacitor C H4 Rear arm diode D H4 Inter-arm diode D M4 The second and third switched capacitor modules are similar.

[0013] Preferably, the front arm diode, rear arm diode, and inter-arm diode in each switched capacitor module are all silicon carbide diodes with low parasitic capacitance.

[0014] Preferably, the front and rear switching capacitors in each switched capacitor module are MLCC (Multilayer Ceramic Capacitor) ceramic capacitors with small size and low stray inductance.

[0015] In this embodiment of the invention, each half-bridge module has the same circuit structure; each half-bridge module is as follows: Figure 3As shown, it includes an upper switch and a lower switch connected in series; wherein, the gates of the upper switch and the lower switch are connected to an external driving module, the drain of the upper switch is connected to an input filter module, the source of the upper switch is connected to the drain of the lower switch and the output filter module, and the source of the lower switch is connected to the DC input voltage V. in The negative terminal is connected. Figure 3 Four half-bridge modules are illustrated, all with identical circuit structures, enabling four-phase cross-parallel control. For ease of subsequent description, the components in the four half-bridge modules are labeled with different identifiers; for example, the first half-bridge module includes a series-connected upper switching transistor S. H1 , lower switch S L1 The fourth half-bridge module includes an upper switching transistor S connected in series. H4 , lower switch S L4 The second and third half-bridge modules are similar. The Nth switched capacitor module corresponds to the Nth half-bridge module and operates within its respective preset switching cycle, where N takes the value 1 to 4.

[0016] Preferably, both the upper and lower switching transistors in each half-bridge module are gallium nitride transistors with no reverse recovery characteristics. More preferably, both the upper and lower switching transistors in each half-bridge module are gallium nitride transistors with the same specifications and no reverse recovery characteristics.

[0017] Preferably, the external driving module is a gallium nitride (GaN) switching device driving unit. This GaN switching device driving unit includes a gate driver chip with high sinking current capability for providing independently controllable high-speed turn-on and turn-off for the GaN device; an isolated DC-DC power supply for powering the gate driver chip; an optocoupler with high common-mode rejection ratio for isolating logic control signals; and a logic signal buffer for converting 3.3V level signals to 5V level signals to reduce crosstalk caused by high dv / dt. The gate driver chip is a 6-pin SOT-23 packaged IC to optimize the gate drive loop of the GaN device.

[0018] In this embodiment of the invention, the output filtering module is as follows: Figure 3 As shown, it includes the output filter capacitor C. o Multiple output filter inductors; one end of each output filter inductor is connected to the corresponding half-bridge module, and the other end of each output filter inductor is connected to the output filter capacitor C. o One end is connected to the output filter capacitor C. o The other end is connected to the DC input voltage V in The negative terminal is connected, and the two ends of the output filter capacitor serve as the output terminals of the output filter module. Figure 3 The diagram illustrates four output filter inductors, denoted as L1, L2, L3, L4, L5, L6, L7, L8, L9, L1 ... O1 Output filter inductor L O2Output filter inductor L O3 Output filter inductor L O4 Output filter inductor L O1 Connected to the first half-bridge module, the output filter inductor L O2 Connected to the second half-bridge module, the output filter inductor L O3 Connected to the third half-bridge module, the output filter inductor L O4 It is connected to the fourth half-bridge module.

[0019] Next, for Figure 3 The operation of the gallium nitride hybrid switched capacitor voltage converter with a high step-down ratio is described in detail.

[0020] After the circuit reaches steady-state operation, taking the first switched capacitor module and the first half-bridge module as examples: in the first switched capacitor module, each switched capacitor reaches the preset voltage, and in the output filter module, the output filter inductor L... O1 After reaching the preset current, such as Figure 4 As shown: The drive signal for the upper switching transistor in each half-bridge module is V. GSH1 ~V GSH4 The voltage of the upper switching transistor in the first half-bridge module is V. DSH1 Input filter inductor L in The voltage is V Lin Output filter inductor L O1 The voltage is V LO1 Output filter inductor L O1 The current is I LO1 Input filter inductor L in The current is I Lin . Figure 4 In the diagram, D represents the duty cycle, and T... s This indicates the switching period; the preset switching period for the first switched capacitor module is 0~T. S / 4, Indicates the input filter capacitor C in The voltage across the terminals, i.e., the DC input voltage. Indicates the output filter capacitor C o The voltage across the terminals, L in For the output filter inductor L in The inductance value, L O1 For the output filter inductor L O1 The inductance value. More specifically: From 0 to DT S During this period, the upper switching transistor S in the first half-bridge module H1 Turn on, switch S L1 Turn off, the forearm diode D in the first switched capacitor module L1 and rear arm diode D H1Conduction, inter-arm diode D M1 At this point, the first switched capacitor module is in a discharging state, and the input filter inductor L... in With output filter inductor L O1 Charging, the bus voltage V of the first half-bridge module HB Equal to the voltage of a single switched capacitor in the first switched capacitor module; during this period, excluding the output filter inductor L O1 In addition, the output filter inductors connected to other half-bridge modules are all discharged, and the current is freewheeled through the lower switching transistor in the corresponding half-bridge module; In DT S To T S During / 4, the upper switch S in the first half-bridge module H1 Turn off, lower switch S L1 Power on, the first switched capacitor module's forearm diode D L1 and rear arm diode D H1 Cut-off, inter-arm diode D M1 When the circuit is turned on, the first switched capacitor module is in a charging state, and the input filter inductor L... in With output filter inductor L O1 Discharge, the bus voltage V of the first half-bridge module HB It equals the sum of the voltages of the two switched capacitors in the first switched capacitor module; the output filter inductors of the remaining half-bridge modules continue to freewheel through the lower switching transistors in the corresponding half-bridge modules.

[0021] During the switching period T S During the remaining time, that is, during T S / 4~T S During this period, the lower half-bridge module undergoes a 90-degree phase shift relative to the upper half-bridge module. For example, the second half-bridge module shifts its phase 90 degrees relative to the first half-bridge module, the third half-bridge module shifts its phase 90 degrees relative to the second half-bridge module, the fourth half-bridge module shifts its phase 90 degrees relative to the third half-bridge module, and the first half-bridge module shifts its phase 90 degrees relative to the fourth half-bridge module. The operating mode of the other phase switched capacitor modules and half-bridge modules is the same as that of the first switched capacitor module and the first half-bridge module, that is: the second switched capacitor module and the second half-bridge module operate at a preset switching period T. S / 4~T S / 2 period, during T S / 4~DT S +T S During / 4, the second switched capacitor module is in a discharging state, DT S +T S / 4~T S During period / 2, the second switched capacitor module is in a charging state; the third switched capacitor module and the third half-bridge module operate during the preset switching period T.S / 2~3T S / 4, in T S / 2~DT S +T S During / 2, the third switched capacitor module is in a discharging state, DT S +T S / 2~3T S During period / 4, the third switched capacitor module is in a charging state; the fourth switched capacitor module and the fourth half-bridge module operate at a preset switching cycle of 3T. S / 4~T S In 3T S / 4~DT S +3T S During period / 4, the fourth switched capacitor module is in a discharging state, DT S +3T S / 4~T S During this period, the fourth switched capacitor module is in a charging state. Within their respective preset switching cycles, their operating mode is the same as that of the first switched capacitor module and the first half-bridge module.

[0022] Since each switched capacitor module and each half-bridge module is in parallel, as the switched capacitor module operating in the preset switching cycle charges and discharges, the bus voltage of the other phase half-bridge modules and the drain-source voltage of the upper switching transistor will also change accordingly. The lower switching transistor remains clamped. During this process, the junction capacitance of the upper switching transistor charges and discharges, and the charge released will be consumed in the conduction channel of the upper switching transistor of the half-bridge module operating in the preset switching cycle, and converted into the switching loss of the module.

[0023] Through the Figure 4 Steady-state waveform analysis shows that the voltage of the switched capacitor in the topology proposed in this invention can be expressed by the following equation: (1); in, This refers to the switched capacitor voltage. For example, in the first switched capacitor module, the switched capacitor voltage includes the voltage of the rear arm switched capacitor C. H1 switched capacitor voltage Forearm switched capacitor C L1 Switching voltage , and The calculation methods are the same, and both can be calculated using formula (1).

[0024] The proposed topology's voltage drop ratio can be expressed by the following formula: (2); Figure 5The diagram illustrates the comparison between the converter proposed in this invention and the traditional Buck converter regarding the buck ratio and duty cycle. As can be seen from Figure 5, compared with the traditional Buck converter, this invention can achieve a higher buck ratio at the same duty cycle, thereby reducing inductor current ripple and filter capacitor size, and achieving better system efficiency and power density.

[0025] Figure 6 This indicates the range from 0 to DT. S During this period, the upper switch S in the first half-bridge module H1 , lower switch S L1 Voltage and current V DSH1 V DSL1 I DSH1 I DSL1 and its bus voltage V HB Transient analysis, which examines the waveform at the moment of switching, is crucial for understanding circuit principles, estimating switching device losses, designing heat dissipation systems, and optimizing system efficiency. The impact of parasitic parameters on the circuit must be considered. The parasitic capacitances in this system mainly include the junction capacitance of the diodes in the front / back / inter-arm configuration of the first switched capacitor module, and the upper switching transistor S in the first half-bridge module. H1 / Down switch transistor S L1 The junction capacitance, inter-winding capacitance of the input filter inductor, inter-winding capacitance of the output filter inductor, and inter-PCB capacitance can all be measured to estimate system losses and heat dissipation requirements in actual design.

[0026] Figures 7(a) to 7(g) This indicates the range from 0 to DT. S The equivalent circuit diagrams for each stage from t1 to t8 are shown below. For simplicity, only the circuits of a single phase (i.e., the first switched capacitor module and the first half-bridge module) are shown in the diagrams from 0 to DT. S During this period, all other phase switched capacitor modules are in a discharging state, and the current in the output filter inductor is the freewheeling current of the lower switching transistor in the corresponding half-bridge module. The following section, using the equivalent circuit diagram, analyzes phases 0 to DT. S The circuit principles of each sub-stage from t1 to t8 are described in detail.

[0027] In phase t1, the upper switch S in the first half-bridge module H1 Turn on, switch S H1 Current I DSH1 The number of switches continues to increase, and the lower switching transistor S... L1 Current I DSL1 Reduce, switch S H1 , lower switch S L1 The sum of the currents equals the output filter inductance L. O1 Current I LO1At this time, the first switched capacitor module is in a discharging state, and the voltage across its terminals is the bus voltage V of the first half-bridge module. HB It equals the voltage across the series connection of the two switched capacitors in the first switched capacitor module, i.e., V. HB =V CH1 +V CL1 =V in +2V out V CH1 This refers to the rear arm switched capacitor C in the first switched capacitor module. H1 voltage, V CL1 This refers to the forearm switched capacitor C in the first switched capacitor module. L1 The voltage. The equivalent circuit diagram is shown in Figure 7(a).

[0028] In phase t2, the upper switch S in the first half-bridge module H1 Current I DSH1 Rise above the input filter inductance L in Current I Lin At this time, the front arm diode D in the first switched capacitor module L1 and rear arm diode D H1 parasitic capacitance C DL1 C DH1 Discharge begins, inter-arm diode D M1 The parasitic capacitor charging, the bus voltage V of the first half-bridge module HB The voltage drops, and the upper switch S in the first half-bridge module... H1 The voltage drops synchronously due to the lower switching transistor S. L1 The clamping effect of the body diode, the rate of descent and the bus voltage V HB Similarly, using silicon carbide diodes with low parasitic parameters can accelerate the bus voltage V of the first half-bridge module. HB That is, the upper switching transistor S in the first half-bridge module H1 The rate of voltage drop reduces switching losses during this phase. The equivalent circuit diagram is shown in Figure 7(b), and the current relationship is as follows: (3); in, This indicates the upper switching transistor S in the first half-bridge module. H1 The current, Indicates the input filter inductance L in The current, This refers to the rear arm diode D in the first switched capacitor module. H1 The current of the parasitic capacitance, This indicates the forearm diode D in the first switched capacitor module. L1 The current of the parasitic capacitance, This refers to the inter-arm diode D in the first switched capacitor module.M1 The current of the parasitic capacitance, This indicates the upper switching transistor S in the first half-bridge module. H1 The current of the parasitic capacitance, Indicates the rear arm diode D H1 Parasitic capacitance, Indicates the forearm diode D L1 Parasitic capacitance, Indicates inter-arm diode D M1 Parasitic capacitance, This represents the bus voltage of the first half-bridge module. Indicates to Find the first-order partial derivative. This indicates the upper switching transistor S in the first half-bridge module. H1 Parasitic capacitance, This indicates the upper switching transistor S in the first half-bridge module. H1 voltage, Indicates to Find the first-order partial derivative.

[0029] In phase t3, the upper switching transistor S in the first half-bridge module H1 Current I DSH1 Rise to output filter inductor L O1 Current I LO1 upper switch S H1 , lower switch S L1 The commutation is complete, and the next switching transistor S is switched on. L1 The junction capacitance begins to charge, at which point the output filter inductor L... O1 Current I LO1 With input filter inductor L in Current I Lin The difference is equal to the sum of the charging and discharging of all junction capacitances in the circuit, and the bus voltage V. HB The voltage continues to drop, and the upper switching transistor S... H1 The voltage is due to the lower switching transistor S L1 The voltage drops more rapidly due to the charging of the junction capacitance. At the end of this phase, the diodes in the first switched capacitor module (front / rear / inter-arm) complete their state transitions, and the bus voltage V of the first half-bridge module decreases. HB The voltage drops to the voltage of a single switched capacitor, and the switching transistor S... H1 Current I DSH1 The spike is caused by the reverse recovery of the diodes in the front / back / inter-arm of the first switched capacitor module. Using silicon carbide diodes with low parasitic parameters can accelerate the switching of the S-transistor. H1 The voltage drop rate is reduced, and the reverse recovery time is decreased, thus lowering the switching losses during this stage. The equivalent circuit diagram is shown in Figure 7(c), and the current relationship is as follows: (4); in, Indicates the output filter inductance L O1 The current, This indicates the lower switching transistor S in the first half-bridge module. L1 The current of the parasitic capacitance, This indicates the lower switching transistor S in the first half-bridge module. L1 Parasitic capacitance, This indicates the lower switching transistor S in the first half-bridge module. L1 voltage, Indicates to Find the first-order partial derivative.

[0030] In phase t4, the forearm diode D in the first switched capacitor module L1 With the rear arm diode D H1 Conduction, inter-arm diode D M1 Cut-off, the bus voltage V of the first half-bridge module HB Clamped to the voltage of a single switched capacitor, the upper switch S in the first half-bridge module H1 The junction capacitance discharges rapidly through the conduction channel, and the upper switching transistor S... H1 The voltage continues to drop, and the lower switching transistor S... L1 The voltage rises during this stage, and the switching transistor S... H1 Current I DSH1 The current spike is caused by the lower switching transistor S. L1 The reverse recovery of the body diode causes current spikes, so using a gallium nitride transistor with no reverse recovery characteristic can reduce current spikes and lower switching losses in this stage. The equivalent circuit diagram is shown in Figure 7(d), and the current relationship is as follows: (5); In phase t5, the upper switching transistor S in the first half-bridge module H1 When in the ON state, the lower switch S L1 When in the off state, the voltage across its terminals is equal to the bus voltage V of the first half-bridge module. HB The first switched capacitor module continues to discharge, and the input filter inductor L... in With output filter inductor L O1 Charging, the bus voltage V of the first half-bridge module HB It is equal to the voltage of a single switched capacitor.

[0031] In phase t6, the upper switching transistor S in the first half-bridge module H1 and the lower switch S L1 All are turned off. The first half-bridge module enters the dead time to achieve soft shutdown, and the upper switching transistor S... H1 The channel current decreases rapidly, and part of the output filter inductor L... O1 The current is the upper switching transistor SH1 The junction capacitance is charged, and the lower switching transistor S... L1 During the junction capacitance discharge stage, the switching losses are negligible due to the soft-switching effect. The equivalent circuit diagram is shown in Figure 7(e), and the current relationships are as follows: (6); In phase t7, the upper switching transistor S in the first half-bridge module H1 The conduction path is completely turned off, and all output filter inductors L O1 The current is the upper switching transistor S H1 The junction capacitance is charged, and the lower switching transistor S... L1 The junction capacitance discharges during this stage due to the upper switching transistor S. H1 The conduction channel is turned off, and the lower switch S... L1 The conduction path is not yet open, so no switching losses occur. However, during this stage, losses accumulate on the upper switching transistor S. H1 The charge in the junction capacitance is released during the next conduction cycle and converted into turn-on losses. Using gallium nitride devices with low parasitic charge can reduce this loss. The equivalent circuit diagram is shown in Figure 7(f), and the current relationships are as follows: (7); In phase t8, the switching transistor S in the first half-bridge module L1 When the voltage drops to zero, the voltage across the switching transistor S is reduced. L1 Applying a gate-level signal enables zero-voltage turn-on. This is achieved by the upper switching transistor S in the first half-bridge module. H1 The current drops to the input filter inductor L in Current I Lin Below, the forearm diode D in the first switched capacitor module L1 and rear arm diode D H1 The parasitic capacitance begins to charge, and the inter-arm diode D... M1 The parasitic capacitance discharges, and the bus voltage V of the first half-bridge module... HB The voltage gradually rises to the sum of the voltages of the two switched capacitors, while the upper switching transistor S in the first half-bridge module... H1 The voltage rises at the same rate as in the previous stage. In this stage, because the first half-bridge module is in a dead zone, no switching losses occur. However, the charge accumulated in the junction capacitances of the diodes in the first switching capacitor module (front / back / inter-arm) and the switching transistors in the first half-bridge module will be released and cause losses at the next turn-on. Using silicon carbide diodes with low parasitic charge can reduce this loss. The equivalent circuit diagram is shown in Figure 7(g), and the current relationships are as follows: (8).

[0032] Figures 7(a) to 7(g)The equivalent circuit diagram only shows 0~DT S During this period, the circuit states of the first switched capacitor module and the first half-bridge module are as follows: In actual operation, all other switched capacitor modules and half-bridge modules connected in parallel with the first switched capacitor module will change with the bus voltage V. HB The parasitic charge accumulates as the voltage rises, and the remaining parasitic charge in the switched capacitor module and half-bridge module will be released when the conduction channel of the next module (such as the second switched capacitor module or the second half-bridge module) is turned on, and is converted into the switching loss of the device.

[0033] From the above analysis, it can be concluded that: First, the present invention proposes... Figure 3 In the topology shown, the switching speed of all half-bridge modules is affected by the bus voltage V. HB First, the clamping effect increases the switching losses of the device. Second, each parallel switched capacitor module and half-bridge module accumulates parasitic charges at different stages and releases them when the conduction channel is turned on. This causes a single transistor to bear the switching losses caused by the reverse recovery of other modules and the release of parasitic charges when it is turned on, increasing the thermal stress on the switching transistor. Third, the diodes in the front / back / inter-arm of the switched capacitor module in this circuit are also in the main current loop of the corresponding half-bridge module at the moment of switching, introducing additional stray inductance, increasing the voltage spike at the moment of switching, increasing switching losses and affecting device reliability. The above problems limit the application of the converter topology proposed in this invention in kilowatt-level high-power scenarios. However, the wide bandgap solution can solve the above problems through lower parasitic capacitance, faster switching speed, better reverse recovery characteristics, smaller package size and less stray inductance, making it possible to achieve the desired switching losses. Figure 3 The illustrated topology achieves a high buck ratio in kilowatt-level industrial systems while also obtaining superior efficiency, power density, and reliability. Therefore, to enable application in kilowatt-level industrial systems, this invention selects: silicon carbide diodes with low parasitic capacitance for the front-arm diode, rear-arm diode, and inter-arm diode in each switched capacitor module; MLCC ceramic capacitors with small size and low stray inductance for the front-arm and rear-arm switched capacitors in each switched capacitor module; and gallium nitride transistors with no reverse recovery characteristics for the upper and lower switching transistors in each half-bridge module.

[0034] This invention takes a four-phase interleaved parallel design as an example, with a rated power of It has a rated DC input voltage of 1.2kW. 270V, rated output voltage The voltage is 28V, and the input and output ripple voltage is less than 1%. More specific parameter designs are shown in Table 1.

[0035] Table 1 Specific Parameter Design

[0036] The parameter calculations for the output filter inductor in Table 1 refer to the output filter inductor L. O1 For calculation methods of other output filter inductor parameters, please refer to the output filter inductor L. O1 This will not be elaborated upon here.

[0037] Table 2 Comparison results of the present invention with traditional silicon-based solutions

[0038] Table 2 illustrates a comparison of the system loss and efficiency estimation between the present invention and traditional silicon-based solutions. In the silicon-based solution, a superjunction MOSFET from Infineon was selected as the switching transistor for the half-bridge module, and an ultra-high-speed diode from Vishay was selected as the diode for the switched capacitor module. In the embodiments of the present invention, a gallium nitride transistor and a silicon carbide diode from Infineon were selected as the switching transistor for the half-bridge module and the diode for the switched capacitor module, respectively. Both the switching transistors and diodes in the comparative schemes are surface-mount packages to achieve better integration and lower stray inductance. Magnetic components are all shielded surface-mount molded inductors from Wiretech.

[0039] As shown in Table 2, this invention improves system efficiency by 7.5% compared to state-of-the-art silicon-based solutions. More importantly, in traditional silicon-based designs, over 50% of losses occur in the upper switching transistor of the half-bridge module. This is due to the release of parasitic charges from a large number of switching transistors and diodes when the upper switching transistor is turned on, as mentioned in the analysis above. This poses a significant challenge to device heat dissipation and reliability design, and is also a major factor restricting the application of this topology in high-power scenarios. This invention reduces the losses of the upper switching transistor by approximately 85% through a wide bandgap solution, significantly reducing the heat dissipation requirements of the half-bridge module and improving system efficiency. Furthermore, this invention uses all surface-mount packaged devices, further reducing PCB size, decreasing stray inductance, reducing voltage spikes, and improving system reliability.

[0040] This invention provides a topology for a gallium nitride hybrid switched-capacitor voltage converter with a high step-down ratio, and analyzes its specific circuit principle, steady-state and transient states. It also elucidates its performance under high power conditions. Figure 3 The limitations of the topology shown are explained, and a wide bandgap solution for this topology is further provided. The system efficiency improvement of the wide bandgap solution compared with the traditional silicon-based solution is quantified. At the same time, a specific design idea for this topology is provided to realize the application of this topology in kilowatt-level systems.

[0041] In summary, the gallium nitride hybrid switched-capacitor voltage converter with high buck ratio proposed in this invention achieves a higher buck ratio than traditional Buck converters at the same duty cycle through innovative topology. This reduces inductor current di / dt, lowers control system requirements, and improves power supply efficiency. Furthermore, the multi-phase interleaved parallel control further improves input current and output voltage ripple, reduces the size of input and output filter inductors and capacitors, and increases the power density and current output capability of the power supply. It is suitable for switching power supply devices requiring high buck ratio, high energy density, and high power. The innovative topology design also rationally selects wide-bandgap devices, reducing switching losses caused by parasitic charges in traditional silicon solutions, improving system efficiency, and significantly reducing thermal stress on the switching transistors, thus enhancing reliability and making it more suitable for kilowatt-level and above switching power supply devices.

[0042] In the description of this invention, it should be understood that 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.

[0043] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the specification and accompanying drawings, will understand and implement other variations of the disclosed embodiments in carrying out the claimed invention. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0044] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A gallium nitride hybrid switched-capacitor voltage converter with a high step-down ratio, characterized in that, The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio includes: an input filter module, a switched-capacitor module group, a half-bridge module group, and an output filter module connected in sequence; the switched-capacitor module group includes several switched-capacitor modules connected in parallel, and the half-bridge module group includes several half-bridge modules connected in parallel, with each switched-capacitor module and half-bridge module corresponding to one and operating within a corresponding preset switching cycle; the output filter module includes several output filter inductors, which are connected to corresponding half-bridge modules; wherein... The input filtering module is used to filter the high-frequency components in the DC input voltage; Each switched capacitor module is used to control the cut-off and conduction of multiple diodes in the switched capacitor module, thereby changing the charging and discharging state of each switched capacitor in the switched capacitor module within a corresponding preset switching cycle, so as to realize the control of the bus voltage of the corresponding half-bridge module and the first voltage conversion of the filtered DC input voltage; wherein, all diodes in each switched capacitor module are silicon carbide diodes. Each half-bridge module is used to perform a second voltage conversion on the bus voltage of the half-bridge module by controlling the switching transistors in the half-bridge module to turn them on and off. At the same time, each half-bridge module is connected in parallel with a 90-degree phase shift to output a high-frequency chopper voltage with a multiplied frequency, so as to reduce the size requirements of the output filter module. All the switching transistors in each half-bridge module are gallium nitride transistors. The output filtering module is used to filter the high-frequency chopped voltage output by each half-bridge module to output a DC voltage with low ripple.

2. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 1, characterized in that, The input filtering module includes an input filtering inductor and an input filtering capacitor; wherein... The two ends of the input filter capacitor serve as the input terminals of the input filter module, and are respectively connected to the positive and negative terminals of the DC input voltage. The two ends of the input filter inductor are respectively connected to the positive terminal of the DC input voltage and each switched capacitor module.

3. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 1, characterized in that, Each switched capacitor module has the same circuit structure; each capacitor switching module includes a front arm switched capacitor, a front arm diode, a rear arm switched capacitor, a rear arm diode, and an inter-arm diode; among which, One end of the rear arm switched capacitor is connected to the cathode of the rear arm diode and the input filter module. The other end of the rear arm switched capacitor is connected to the cathode of the front arm diode and the anode of the inter-arm diode. The anode of the rear arm diode is connected to the cathode of the inter-arm diode and one end of the front arm switched capacitor. The anode of the front arm diode is connected to the other end of the front arm switched capacitor and the negative terminal of the DC input voltage.

4. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 3, characterized in that, The forearm diodes, rear arm diodes, and inter-arm diodes in each switched capacitor module are all silicon carbide diodes with low parasitic capacitance.

5. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 3, characterized in that, The forearm and rear arm switching capacitors in each switched capacitor module are all MLCC ceramic capacitors with small size and low stray inductance.

6. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 1, characterized in that, Each half-bridge module has the same circuit structure; each half-bridge module includes an upper switch and a lower switch connected in series; wherein, The gates of the upper and lower switching transistors are connected to the external driving module. The drain of the upper switching transistor is connected to the input filter module. The source of the upper switching transistor is connected to the drain of the lower switching transistor and the output filter module. The source of the lower switching transistor is connected to the negative terminal of the DC input voltage.

7. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 6, characterized in that, The upper and lower switching transistors in each half-bridge module are all gallium nitride transistors with no reverse recovery characteristics.

8. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 6, characterized in that, The external drive module is a gallium nitride switching device drive unit.

9. The gallium nitride hybrid switched-capacitor voltage converter with high step-down ratio according to claim 1, characterized in that, The output filtering module includes an output filtering capacitor and multiple output filtering inductors; wherein... One end of each output filter inductor is connected to the corresponding half-bridge module, and the other end of each output filter inductor is connected to one end of the output filter capacitor. The other end of the output filter capacitor is connected to the negative terminal of the DC input voltage. The two ends of the output filter capacitor serve as the output terminals of the output filter module.

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