Partial power DC-DC conversion system and conversion control method

Abstract

The invention relates to the technical field of DC-DC converters, in particular to a partial power DC-DC conversion system and a conversion control method. The GaN bridge arm assembly is composed of a GaN power device and supports bidirectional electric energy flow. The bidirectional inductor is connected between the energy input port and the energy output port to form a core energy channel; the high-frequency isolation transformer is connected with the GaN bridge arm to form an isolated hybrid energy path structure; and the control unit is connected to the GaN bridge arm assembly and is used for generating a driving signal and realizing partial power processing and four-quadrant operation. According to the scheme, through a partial power processing architecture, only the power corresponding to the voltage difference is converted, and the stress of a switching device and a magnetic element is reduced; the size and the weight of the inductor and the transformer are reduced, and the power density is improved; the dynamic logic synthesis control strategy avoids the problems of hard switching and circulation of a traditional control mode, and mode smooth transition and full-range soft switching are achieved.

Description

Technical Field

[0001] This invention relates to the field of DC-DC converter technology, and in particular to a partial power DC-DC conversion system and conversion control method. Background Technology

[0002] With the rapid development of electric vehicles, battery energy storage systems, and bidirectional charging piles, the demand for bidirectional DC-DC converters is increasing, requiring support for four-quadrant operation to achieve efficient bidirectional power transmission. Traditional converters mostly adopt a full-power conversion structure, where all energy is processed through switching devices and magnetic components, resulting in high device stress, low efficiency, large size, and prominent heat dissipation and EMI issues, making them particularly inconvenient to use in high-voltage, high-power scenarios.

[0003] While some existing power processing solutions can improve efficiency by converting part of the energy from the voltage difference, most of these solutions are based on silicon devices, which have low switching frequencies and insufficient power density. Furthermore, they are complex to control in four-quadrant operation and are prone to problems such as mode switching impact, hard switching losses, circulating current, and narrow soft switching range. If an isolated solution is used, additional circuitry is required, increasing complexity and cost.

[0004] Therefore, there is a need for a partial-power DC-DC conversion system and conversion control method that can significantly improve efficiency and reduce device stress, reduce the size of magnetic components during GaN high-frequency operation, increase power density, avoid hard switching and circulating current with dynamic control, reduce losses and EMI, support full four-quadrant operation with symmetrical layout, improve dynamic response and stability and provide electrical isolation, and improve system reliability to meet the needs of the current environment. Summary of the Invention

[0005] Therefore, the technical problem to be solved by this invention is that: traditional converters mostly adopt a full-power conversion structure, and all energy is processed through switching devices and magnetic components, resulting in high device stress, low efficiency, large size, and prominent heat dissipation and EMI problems. Existing power processing solutions are prone to problems such as mode switching impact, hard switching loss, circulating current, and narrow soft switching range.

[0006] The above-mentioned technical problems are solved by the following technical solution: This invention proposes a partial power DC-DC conversion system, which includes, Energy input port, energy output port, GaN bridge arm assembly, bidirectional inductor, high-frequency isolation transformer and control unit; The GaN bridge arm assembly is composed of GaN power devices and supports bidirectional power flow; the bidirectional inductor is connected between the energy input port and the energy output port to form the core energy channel. A high-frequency isolation transformer is connected to a GaN bridge arm to form an isolated hybrid energy path structure; The control unit is connected to the GaN bridge arm assembly and is used to generate drive signals, enabling partial power processing and four-quadrant operation.

[0007] In a preferred embodiment of the partial power DC-DC conversion system described in this invention: The GaN bridge arm assembly includes a first low-voltage side bridge arm, a second low-voltage side bridge arm, and a high-voltage side bridge arm. The GaN bridge arm assembly has a centrally symmetrical layout. The first low-voltage side bridge arm includes switches S1-4, the high-voltage side bridge arm includes switches S5-8, and the second low-voltage side bridge arm includes switches S9-12, supporting high-frequency switching and low conduction loss.

[0008] In a preferred embodiment of the partial power DC-DC conversion system described in this invention: The midpoint of the bidirectional inductor is coupled to the high-frequency isolation transformer; The primary side of the high-frequency isolation transformer is connected in series with the high-voltage side bridge arm, and the secondary side is connected between the first low-voltage side bridge arm and the second low-voltage side bridge arm to process the energy of the input-output voltage difference, while the main energy path remains straight.

[0009] A conversion control method includes the aforementioned partial-power DC-DC conversion system, and, The system operates by setting charging and discharging modes. In charging and discharging modes, the system switches between direct energy storage, auxiliary freewheeling, and hybrid boost transmission modes based on the relationship between the duty cycle d and the boundary value dmax. Two sets of logic algorithms are preset, and a dynamic logic synthesis control strategy is adopted. Based on the relationship between the duty cycle d and the boundary value dmax, a seamless logic switching of first judgment and then flip is achieved.

[0010] In a preferred embodiment of the transformation control method described in this invention: When the system is running in charging mode, d and dmax are compared. If d≤dmax, the system enters the direct-through energy storage state, and the control unit drives the first low-voltage side bridge arm and the second low-voltage side bridge arm to conduct, while the high-voltage side bridge arm is closed. Energy is directly transferred from the energy input port to the energy output port through a bidirectional inductor, achieving energy transfer directly without passing through a high-frequency isolation transformer, thus completing a high-efficiency step-down conversion.

[0011] In a preferred embodiment of the transformation control method described in this invention: When the system is running in charging mode, it enters the auxiliary freewheeling state after the direct energy storage state. In auxiliary freewheeling mode, the control unit turns off switches S2, 3, 10, and 11, while keeping switches S1, 4, 9, and 12 on, thus changing the current path; The current flows through S1, enters the secondary winding of the high-frequency isolation transformer, and then flows out through S12. Magnetic coupling causes S5 and S8 of the high-voltage side bridge arm to conduct, and the feedback energy enters C1. The bidirectional inductor discharge realizes the intermediate stage regulation of energy. If d > dmax, the system enters the hybrid boost transmission state. The control unit drives S1, 4, 9, and 12 in the first and second low-voltage side bridge arms to turn off, and S2, 3, 10, and 11 to turn on. It also drives S5 and 8 in the high-voltage side bridge arm to turn on. The energy output from the secondary side of the high-frequency isolation transformer flows to the bidirectional inductor via switch S2 and then out via switch S10, creating an additional channel for energy injection from the high-voltage to the low-voltage side. The system obtains a higher voltage at the output end than at the input end, achieving smooth voltage boost.

[0012] In a preferred embodiment of the transformation control method described in this invention: When the system is operating in discharge mode, d and dmax are compared. If d≤dmax, the system enters the reverse direct energy storage state, and the control unit drives the first low-voltage side bridge arm and the second low-voltage side bridge arm to conduct, while the high-voltage side bridge arm is closed. Energy flows from the energy output port into the bidirectional inductor in reverse via S11 and S12, and then into the energy input port via S3 and S4, completing the reverse magnetic energy accumulation.

[0013] In a preferred embodiment of the transformation control method described in this invention: When the system is operating in discharge mode, after the reverse direct-through energy storage state is activated, it enters the reverse auxiliary freewheeling state. In reverse auxiliary freewheeling mode, the control unit turns off switches S1, 4, 9, and 12, while keeping switches S2, 3, 10, and 11 on, thus changing the current path; The current flows through switch S10, enters the secondary winding of the high-frequency isolation transformer, and then flows out through S3. The high-frequency isolation transformer induces a reverse high voltage on its primary side, which is fed back to the input capacitor C1 via the high-voltage side switches S5 to S8. The high-frequency isolation transformer is used to achieve reverse step-down voltage regulation and freewheeling. If d > dmax, the system enters the reverse hybrid boost transmission state. The control unit drives S2, 3, 10, and 11 in the first and second low-voltage side bridge arms to turn off, and S1, 4, 9, and 12 to turn on. It also drives S5 and 8 in the high-voltage side bridge arm to turn on. High-voltage side energy is coupled through a high-frequency isolation transformer to assist in boosting the low-voltage side voltage, achieving mixed energy transmission with the same physical path but in the opposite direction.

[0014] In a preferred embodiment of the transformation control method described in this invention: In the dynamic logic synthesis control strategy, the real-time calculated master control duty cycle d is compared with the preset boundary threshold dmax; If d≤dmax, the processor determines that the system is in the basic transfer area and the control pointer points to the first set of driving logic algorithms. If d is greater than dmax, the processor determines that the system has entered the hybrid enhancement zone and switches the control pointer to point to the second set of driving logic algorithms.

[0015] In a preferred embodiment of the transformation control method described in this invention: When the system is in the basic transmission zone, complementary decreasing logic is executed in the high-voltage side bridge arm. The conduction time decreases linearly with the increase of the duty cycle d. The first low-voltage side bridge arm and the second low-voltage side bridge arm directly follow the main signal d. When the system determines that it has entered the hybrid enhancement region, the high-voltage side bridge arm performs a logic flip, and the conduction time increases with the increase of d. The drive signals of the first low-voltage side bridge arm and the second low-voltage side bridge arm are forcibly clamped at the maximum conduction value and no longer increase with d. Before the logic waveform is sent to the drive circuit, the PWM timing generator in the system inserts an adaptive dead time in the microsecond-level interval between each switching state transition according to the current current flow. During the dead time, the freewheeling current in the bidirectional inductor draws the charge from the junction capacitance that is about to be turned on. When the voltage across the switch is detected to drop to zero, the drive command is finally released.

[0016] The beneficial effects of this invention are as follows: by using a partial power processing architecture, only the power corresponding to the voltage difference is transformed, which reduces the stress on switching devices and magnetic components; GaN devices support high-frequency operation, reducing the size and weight of inductors and transformers and increasing power density; the dynamic logic synthesis control strategy avoids the hard switching and circulating current problems of traditional control modes, realizes smooth mode transition and full-range soft switching, and reduces switching losses and EMI; the centrally symmetrical layout and six-mode division ensure the symmetry and controllability of forward and reverse energy flow, and supports complete four-quadrant operation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0018] Figure 1 The topology diagram of the partial power DC-DC conversion system in this invention is shown.

[0019] Figure 2The charging mode of the DC-DC conversion system with partial power in this invention is shown as the through-current energy storage state.

[0020] Figure 3 The equivalent circuit of the charging mode-assisted freewheeling state of the partial power DC-DC conversion system of the present invention is shown.

[0021] Figure 4 The equivalent circuit of the charging mode-hybrid boost state of the DC-DC converter system with partial power in this invention is shown.

[0022] Figure 5 The discharge mode of the DC-DC converter system with partial power in this invention is shown as the reverse direct energy storage state.

[0023] Figure 6 The equivalent circuit of the discharge mode-reverse auxiliary freewheeling state of the partial power DC-DC conversion system of the present invention is shown.

[0024] Figure 7 The equivalent circuit of the discharge mode-reverse hybrid boost state of the partial power DC-DC converter system of the present invention is shown.

[0025] Figure 8 A flowchart of the dynamic logic synthesis control strategy determination process corresponding to the transformation control method in this invention is shown. Detailed Implementation

[0026] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0027] The terminology used in this invention refers to those general terms currently widely used in the art in consideration of the functionality of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new techniques. Furthermore, specific terms may be chosen independently, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terminology used in this specification should not be construed as simple names, but rather based on the meaning of the terms and the overall description of the invention.

[0028] Reference Figure 1 This embodiment provides a partial power DC-DC conversion system.

[0029] This system achieves efficient bidirectional power transmission and isolation protection through topology design and high-efficiency component integration. It is particularly suitable for applications with extremely high power density and efficiency requirements in scenarios such as electric vehicle drive, battery energy storage systems, and bidirectional charging piles.

[0030] The system includes an energy input port 1, an energy output port 2, a GaN bridge arm assembly 3, a bidirectional inductor 4, a high-frequency isolation transformer 5, and a control unit 6. Energy input port 1 is used to connect to a high-voltage power source such as the power grid or a high-voltage battery pack, providing a stable input voltage Vin. Energy output port 2 connects to a low-voltage load or battery, enabling energy output or feedback Vout. This port design ensures flexible system access and supports bidirectional operation for both forward charging and reverse discharging.

[0031] GaN bridge arm assembly 3 is the core power conversion module of the system, composed of multiple GaN power devices. The structure of GaN bridge arm assembly 3 features a centrally symmetrical layout with a total of 12 high-speed GaN device switches. GaN devices, with their extremely low on-resistance, fast switching speed, and low reverse recovery current characteristics, support high-frequency operation and bidirectional power flow. They can seamlessly switch between four quadrant modes: positive voltage and positive current, positive voltage and negative current, negative voltage and positive current, and negative voltage and negative current, avoiding the high losses and thermal management challenges associated with traditional silicon-based devices.

[0032] A bidirectional inductor 4 is connected between energy input port 1 and energy output port 2, forming the core energy channel of the system. Designed for bidirectional operation, the bidirectional inductor 4 can store and release magnetic energy in forward mode to achieve buck or boost conversion; in reverse mode, it supports energy feedback from the output to the input. The midpoint of the bidirectional inductor 4 is coupled to the high-frequency isolation transformer 5, ensuring that the main energy path remains highly efficient and direct, handling only the power of the input-output voltage difference, thereby significantly reducing overall system losses.

[0033] The high-frequency isolation transformer 5 is tightly connected to the GaN bridge arm assembly 3, forming an isolated hybrid energy path structure. The high-frequency isolation transformer 5 not only provides electrical isolation and improves system safety, but also efficiently transmits differential power in high duty cycle mode, enabling energy injection or extraction.

[0034] The control unit 6 is connected to the GaN bridge arm assembly 3 and is responsible for generating independent drive signals to achieve partial power processing and four-quadrant operation. The control unit 6 dynamically adjusts the turn-on / turn-off sequence of the GaN device according to the input-output voltage difference and energy flow direction to ensure smooth transition of the system in different modes, while better suppressing ripple interference and hard switching.

[0035] As one embodiment provided, such as Figures 1-6 , Based on Example 1, this embodiment further refines the internal structure of the GaN bridge arm assembly 3 and the coupling method between the high-frequency isolation transformer 5 and the bidirectional inductor 4, which can enhance the symmetry and efficiency of the system.

[0036] The GaN bridge arm assembly 3 consists of a first low-voltage side bridge arm 31, a second low-voltage side bridge arm 32, and a high-voltage side bridge arm 33, arranged in a centrally symmetrical layout to ensure symmetry in forward and reverse operation. This layout allows the system to operate smoothly in four-quadrant mode, avoiding circulating current problems caused by imbalance.

[0037] The first low-voltage side bridge arm 31 includes switches S1 to S4, the high-voltage side bridge arm 33 includes switches S5 to S8, and the second low-voltage side bridge arm 32 includes switches S9 to S12, totaling 12 GaN power devices. These switches support high-frequency switching and low conduction losses, significantly reducing switching losses and heat generation, and improving the power density of the system.

[0038] The primary side of the high-frequency isolation transformer 5 is connected in series with the high-voltage side bridge arm 33, and the secondary side of the high-frequency isolation transformer 5 is connected between the first low-voltage side bridge arm 31 and the second low-voltage side bridge arm 32. Structurally, this forms an isolated hybrid energy path, which is only used to process the energy of the input-output voltage difference portion, while the main energy path remains straight-through, thereby maximizing system efficiency and reducing the size of magnetic components. The high-frequency isolation transformer 5 provides electrical isolation, enhancing the system's safety under high-voltage environments.

[0039] The control unit 6 is connected to the GaN bridge arm assembly 3 and is used to generate drive signals. It supports partial power processing and four-quadrant operation and also includes PWM timing generation, thereby optimizing the switching sequence and reducing EMI.

[0040] As one embodiment provided, such as Figures 1-8 , Based on Example 2, this embodiment provides a conversion control method for a partial power DC-DC conversion system. This method achieves seamless state switching between charging and discharging modes through dynamic logic synthesis strategy and duty cycle threshold determination, while supporting four-quadrant operation to ensure efficient and stable operation of the system under wide range of transformer ratios and dynamic load conditions.

[0041] During system operation, charging and discharging modes are first set. In charging mode, energy flows from energy input port 1 to energy output port 2; in discharging mode, energy flows in the reverse direction. In both modes, based on the relationship between the real-time duty cycle d and the preset boundary value dmax, three typical operating states are switched: direct-through energy storage state, auxiliary freewheeling state, and hybrid boost transmission state. The method pre-defines two sets of driving logic algorithms and employs a dynamic logic synthesis control strategy. Through a "determine first, then flip" mechanism, seamless logic switching of the bridge arm conduction sequence is achieved, avoiding current surges and hard switching issues during mode transitions.

[0042] In charging mode, control unit 6 first compares d and dmax. If d ≤ dmax, the system enters the direct-drive energy storage state.

[0043] At this time, the control unit 6 drives all switches S1~S4 of the first low-voltage side bridge arm 31 and switches S9~S12 of the second low-voltage side bridge arm 32 to be turned on, while switches S5~S8 of the high-voltage side bridge arm 33 are turned off. Energy flows out from the positive terminal of the energy input port 1, merges into the parallel branch of S1 and S2, flows directly through the bidirectional inductor 4, and then flows to the energy output port 2 through the branch of S9 and S10.

[0044] In this state, no current flows through the high-frequency isolation transformer 5, and it does not participate in energy transfer. The bidirectional inductor 4 bears a positive voltage and stores energy, achieving direct energy transfer and high-efficiency step-down conversion. This state can fully utilize the low on-resistance and inductor buffer characteristics of GaN devices to ensure stable operation with extremely low losses.

[0045] After the system enters the direct energy storage state, it switches to the auxiliary freewheeling state. The control unit 6 turns off switches S2, S3, S10, and S11, while keeping switches S1, S4, S9, and S12 on, forcibly changing the current path. At this time, due to the freewheeling characteristics of the bidirectional inductor 4, the current enters the secondary winding of the high-frequency isolation transformer 5 through S1 and then flows out through S12.

[0046] Through magnetic coupling, the secondary current of the high-frequency isolation transformer induces energy on the primary side, causing the body diodes of switches S5~S8 on the high-voltage side bridge arm 33 to conduct, feeding some energy back to the input capacitor C1. At this time, the bidirectional inductor 4 is in a discharging state, and the high-frequency isolation transformer 5 assists in clamping the voltage, realizing intermediate-stage energy regulation, preventing voltage spikes, and optimizing output smoothness.

[0047] If the voltage demand increases to the point that d > dmax, the system enters a hybrid boost transmission state. Control unit 6 drives S1, S4, S9, and S12 in the first low-voltage side bridge arm 31 and the second low-voltage side bridge arm 32 to turn off, and S2, S3, S10, and S11 to turn on, and actively drives S5 to S8 in the high-voltage side bridge arm 33 to turn on.

[0048] High-voltage side energy flows in reverse direction through switches S5-S8 into the primary side of high-frequency isolation transformer 5, and is then magnetically coupled to the secondary side. The induced current on the secondary side is superimposed on the low-voltage side circuit. The entire current output path is as follows: the energy output from the transformer secondary side flows through switch S2 to bidirectional inductor 4, and then out through switch S10. This design creates an additional channel for injecting energy from the high-voltage side to the low-voltage side, enabling the system to obtain a higher voltage at the output than at the input, achieving smooth boost output characteristics, while only handling voltage difference power, reducing the burden on magnetic components.

[0049] The control logic for the discharge mode is centrally symmetrical with that for the charging mode. If d ≤ dmax, the system enters a reverse direct-through energy storage state. The control unit 6 drives the first low-voltage side bridge arm 31 and the second low-voltage side bridge arm 32 to be fully turned on, while the high-voltage side bridge arm 33 is turned off.

[0050] The energy flow at this time is as follows: the energy output port 2 flows out, flows in reverse through nodes S11 and S12 into bidirectional inductor 4, and then feeds back to energy input port 1 through nodes S3 and S4 to complete the reverse magnetic energy accumulation. At this time, the high-frequency isolation transformer 5 does not work to ensure efficient reverse transmission.

[0051] Subsequently, the system enters the reverse auxiliary freewheeling state. Control unit 6 shuts off switches S1, S4, S9, and S12, while keeping switches S2, S3, S10, and S11 on, thus changing the current path. The current flows through switch S10, enters the secondary winding of the high-frequency isolation transformer 5, and then flows out through S3. A reverse high voltage is induced on the primary side of the high-frequency isolation transformer 5, which is fed back to the input capacitor C1 via switches S5~S8 on the high-voltage side bridge arm 33. The transformer is used to achieve reverse voltage reduction or voltage regulation freewheeling, maintaining system stability.

[0052] If d > dmax, the system enters a reverse hybrid boost transmission state. Control unit 6 drives switches S2, S3, S10, and S11 in the first low-voltage side bridge arm 31 and the second low-voltage side bridge arm 32 to turn off, while switches S1, S4, S9, and S12 turn on. This also drives switches S5 to S8 in the high-voltage side bridge arm 33 to turn on. At this time, the current flows through the loop formed by S9, the secondary side of the high-frequency isolation transformer 5, and switch S4. High-voltage side energy is coupled through the transformer, assisting in voltage boosting on the low-voltage side. This achieves hybrid energy transmission with the same physical path but opposite direction as the high-duty-cycle charging mode, ensuring full-range controllability of bidirectional flow.

[0053] In dynamic logic synthesis control strategies, the first step is to acquire the input voltage Vin and output voltage Vout in real time using high-precision voltage and current sensors. The main control duty cycle d is calculated based on the deviation. Then, d is compared with dmax. If d ≤ dmax, the processor determines that the system is in the basic transmission zone and the control pointer points to the first set of driving logic algorithms; if d > dmax, it determines that it has entered the hybrid enhancement zone and switches to the second set of algorithms.

[0054] In the basic transmission region, the high-voltage side arm 33 executes complementary decreasing logic, and the conduction time decreases linearly with the increase of d, which follows a 1-d function relationship. The first low-voltage side arm 31 and the second low-voltage side arm 32 directly follow the main signal d.

[0055] In the hybrid enhancement region, the high-voltage side arm 33 performs a logic flip, and the conduction time increases with the increase of d. This part follows the functional relationship of 1 + d - twice dmax. At this time, the drive signal of the low-voltage side arm is forced to be clamped at the maximum conduction value and no longer increases with the increase of d. This synthesis of "determine first, then flip" eliminates the physical switching breakpoint.

[0056] Finally, before the logic waveform is sent to the driver circuit, the timing generator PWM will insert an adaptive dead time in the microsecond-level gap between the switching state transitions, based on the current flow direction. During the dead time, the freewheeling current of the bidirectional inductor 4 draws the junction capacitance charge of the switch that is about to be turned on. The drive command is only released when the voltage across the switch is detected to drop to zero, thereby achieving zero-voltage soft switching under all operating conditions and further reducing losses and EMI.

[0057] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. A partial-power DC-DC converter system, characterized in that: include, Energy input port (1), energy output port (2), GaN bridge arm assembly (3), bidirectional inductor (4), high-frequency isolation transformer (5) and control unit (6); The GaN bridge arm assembly (3) is composed of GaN power devices and supports bidirectional power flow; the bidirectional inductor (4) is connected between the energy input port (1) and the energy output port (2) to form the core energy channel; The high-frequency isolation transformer (5) is connected to the GaN bridge arm to form an isolated hybrid energy path structure; The control unit (6) is connected to the GaN bridge arm assembly (3) to generate drive signals and realize partial power processing and four-quadrant operation.

2. The partial power DC-DC converter system according to claim 1, characterized in that: The GaN bridge arm assembly (3) includes a first low-voltage side bridge arm (31), a second low-voltage side bridge arm (32) and a high-voltage side bridge arm (33), and the GaN bridge arm assembly (3) is arranged in a centrally symmetrical manner. The first low-voltage side bridge arm (31) includes switches S1~4, the high-voltage side bridge arm (33) includes switches S5~8, and the second low-voltage side bridge arm (32) includes switches S9~12, supporting high-frequency switching and low conduction loss.

3. The partial power DC-DC converter system according to claim 2, characterized in that: The midpoint of the bidirectional inductor (4) is coupled to the high-frequency isolation transformer (5); The primary side of the high-frequency isolation transformer (5) is connected in series with the high-voltage side bridge arm (33), and the secondary side is connected between the first low-voltage side bridge arm (31) and the second low-voltage side bridge arm (32) to process the energy of the input-output voltage difference. The main energy path remains straight.

4. A transformation control method, characterized in that: Including the partial power DC-DC conversion system as described in claim 3, and, The system operates by setting charging and discharging modes. In charging and discharging modes, the system switches between direct energy storage, auxiliary freewheeling, and hybrid boost transmission modes based on the relationship between the duty cycle d and the boundary value dmax. Two sets of logic algorithms are preset, and a dynamic logic synthesis control strategy is adopted. Based on the relationship between the duty cycle d and the boundary value dmax, a seamless logic switching of first judgment and then flip is achieved.

5. The transformation control method according to claim 4, characterized in that: When the system is running in charging mode, d and dmax are compared. If d≤dmax, the system enters the direct-through energy storage state. The control unit (6) drives the first low-voltage side bridge arm (31) and the second low-voltage side bridge arm (32) to conduct, and the high-voltage side bridge arm (33) to close. Energy is directly transferred from the energy input port (1) through the bidirectional inductor (4) to the energy output port (2), achieving energy transfer directly without passing through the high-frequency isolation transformer (5), thus completing a high-efficiency step-down conversion.

6. The transformation control method according to claim 4, characterized in that: When the system is running in charging mode, it enters the auxiliary freewheeling state after the direct energy storage state. In the auxiliary freewheeling state, the control unit (6) turns off switches S2, 3, 10, and 11, while keeping switches S1, 4, 9, and 12 on, thus changing the current path; The current flows through S1 and enters the secondary winding of the high-frequency isolation transformer (5) and then flows out through S12. Magnetic coupling makes S5 and S8 of the high-voltage side bridge arm (33) conduct, and the feedback energy enters C1. The bidirectional inductor (4) discharges to realize the intermediate stage regulation of energy. If d > dmax, the system enters the hybrid boost transmission state. The control unit (6) drives S1, 4, 9, and 12 in the first low-voltage side bridge arm (31) and the second low-voltage side bridge arm (32) to turn off, and S2, 3, 10, and 11 to turn on. It also drives S5 and 8 in the high-voltage side bridge arm (33) to turn on. The secondary side output energy of the high-frequency isolation transformer (5) flows to the bidirectional inductor (4) through switch S2 and flows out through switch S10, forming an additional channel for energy injection from high voltage to low voltage side. The system obtains a voltage at the output end that is higher than that at the input end, thus achieving smooth voltage boost.

7. The transformation control method according to claim 4, characterized in that: When the system is operating in discharge mode, d and dmax are compared. If d≤dmax, the system enters the reverse direct energy storage state. The control unit (6) drives the first low-voltage side bridge arm (31) and the second low-voltage side bridge arm (32) to conduct, and the high-voltage side bridge arm (33) to close. Energy flows from the energy output port (2) through S11 and S12 into the bidirectional inductor (4) in reverse, and then through S3 and S4 into the energy input port (1), completing the reverse magnetic energy accumulation.

8. The transformation control method according to claim 4, characterized in that: When the system is operating in discharge mode, after the reverse direct-through energy storage state is activated, it enters the reverse auxiliary freewheeling state. In the reverse auxiliary freewheeling state, the control unit (6) turns off switches S1, 4, 9, and 12, while keeping switches S2, 3, 10, and 11 on, thus changing the current path; The current flows through switch S10, enters the secondary winding of high-frequency isolation transformer (5), and then flows out through S3; The high-frequency isolation transformer (5) induces a reverse high voltage on the primary side, which is fed back to the input capacitor C1 via the high-voltage side switches S5 to S8. The high-frequency isolation transformer (5) is used to achieve reverse voltage reduction, voltage regulation and freewheeling. If d > dmax, the system enters the reverse hybrid boost transmission state. The control unit (6) drives S2, 3, 10, and 11 in the first low-voltage side bridge arm (31) and the second low-voltage side bridge arm (32) to turn off, and S1, 4, 9, and 12 to turn on. It also drives S5 and 8 in the high-voltage side bridge arm (33) to turn on. The high-voltage side energy is coupled through the high-frequency isolation transformer (5) to assist the low-voltage side voltage to be boosted, thus realizing the mixed energy transmission with the same physical path but in the opposite direction.

9. The transformation control method according to any one of claims 4 to 8, characterized in that: In the dynamic logic synthesis control strategy, the real-time calculated master control duty cycle d is compared with the preset boundary threshold dmax; If d≤dmax, the processor determines that the system is in the basic transfer area and the control pointer points to the first set of driving logic algorithms. If d is greater than dmax, the processor determines that the system has entered the hybrid enhancement zone and switches the control pointer to point to the second set of driving logic algorithms.

10. The transformation control method according to claim 9, characterized in that: When the system is in the basic transmission zone, complementary decreasing logic is executed in the high-voltage side bridge arm (33), and the conduction time decreases linearly with the increase of the duty cycle d. The first low-voltage side bridge arm (31) and the second low-voltage side bridge arm (32) directly follow the main signal d. When the system determines that it has entered the hybrid enhancement zone, the high-voltage side bridge arm (33) performs a logic flip, and the conduction time increases with the increase of d. The drive signals of the first low-voltage side bridge arm (31) and the second low-voltage side bridge arm (32) are forced to be clamped at the maximum conduction value and no longer increase with d. Before the logic waveform is sent to the drive circuit, the PWM timing generator in the system inserts an adaptive dead time in the microsecond-level interval between each switching state transition according to the current current flow. During the dead time, the freewheeling current in the bidirectional inductor (4) draws the charge of the junction capacitance that is about to be turned on. When the voltage across the switch is detected to drop to zero, the drive command is finally released.

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