Multi-mode control method of multi-phase LLC resonant converter and multi-phase LLC resonant converter

Abstract

The invention discloses a multi-mode control method of a multi-phase LLC resonant converter and the multi-phase LLC resonant converter. The converter comprises N phases of LLC resonant units (N is greater than or equal to 2) which are connected in parallel. A smooth mode switching mechanism is provided, and self-adaptive switching between a partial-phase working mode and a full-phase working mode is carried out according to load changes: when a new phase needs to be input, the control frequency and the duty ratio of a switching tube are kept the same as real-time parameters of any current working phase; after a new phase switching tube works, synchronous rectification driving is delayed to be started, and energy transmission is completely put into use after a resonant cavity of the phase establishes a stable resonant state and a preset protection time. The method fundamentally solves the problem of low efficiency caused by multi-phase idle running of the multi-phase LLC in light and medium loads, is especially suitable for specific topologies such as three-phase (N = 3) and the like, can remarkably improve the weighted average efficiency of the system in a wide load range, and particularly meets application scenes with high efficiency requirements such as an automobile power supply and the like.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a multi-mode control method for a multi-phase LLC resonant converter and the multi-phase LLC resonant converter itself. Background Technology

[0002] With the rapid development of electric vehicles and high-performance in-vehicle electrical equipment, in-vehicle power systems are evolving towards higher power density, higher efficiency, and wider load range. LLC resonant converters, with their excellent soft-switching characteristics—zero-voltage turn-on for the primary-side switches and zero-current turn-off for the secondary-side rectifiers—have become one of the mainstream topologies for achieving high-efficiency DC-DC conversion. In high-power in-vehicle applications, such as on-board chargers or high-voltage DC-DC converters, multi-phase interleaved parallel LLC topologies are widely used to meet power level requirements and reduce current ripple and the size and weight of magnetic components. For example, traditional control strategies typically operate the three phases with a fixed 120° phase difference, which effectively distributes current, reduces losses, and improves power handling capacity under heavy or full load conditions.

[0003] However, the actual operating conditions of automotive power supplies have their own unique characteristics. Vehicles spend most of their time not operating at peak power, but rather in standby, low-power, or medium-load driving conditions. Therefore, industry evaluation standards not only focus on peak efficiency but also emphasize the weighted average efficiency across the entire operating load spectrum. The traditional fixed three-phase operation mode reveals significant shortcomings under medium, light, and even no-load conditions: even when the output power demand is very low, the three resonant cavities and their corresponding transformer magnetic circuits continue to operate under the controller's drive. This results in three near-no-load resonant circulating current losses and transformer core losses. These "idle" losses are particularly prominent when the total output power percentage is very low, severely reducing the overall system efficiency in the medium and light load range and failing to meet the core demand for high efficiency in modern automotive power supplies.

[0004] To address this issue, the industry has recognized the need to shut down some phases under light loads. However, simple switching on and off introduces new technical challenges: First, the dynamic process during mode switching may cause output voltage oscillations, affecting stability; second, if the initial state of the resonant cavity (such as the resonant capacitor voltage) is not synchronized with the system at the moment a new phase is switched on, it will generate huge surge currents or voltage stresses, threatening the safety of the switching transistors; third, how to achieve a smooth, uninterrupted transition of the control loop (frequency, duty cycle) under different phase number operating modes, avoiding control misalignment during switching. Existing solutions or switching logics are complex, have slow dynamic response, or lack a pre-synchronization mechanism for the resonant cavity state, resulting in insufficient reliability and making them difficult to widely apply in high-reliability fields such as automotive electronics.

[0005] Therefore, there is an urgent need for a control method specifically designed for multiphase LLC topologies, capable of intelligently adapting to load changes, automatically optimizing the number of operating phases, and achieving fast, smooth, and reliable switching between modes, in order to maximize the efficiency potential of multiphase LLC over a wide load range and meet the needs of automotive power supplies and other applications that emphasize full-load efficiency. Summary of the Invention

[0006] To address the technical shortcomings of existing multiphase LLC resonant converters that employ a fixed full-phase operating mode, which suffer from significant no-load losses due to the continuous operation of all resonant units under light and medium load conditions, leading to a decrease in overall system efficiency (especially weighted average efficiency), this application provides a control method and device that can automatically and smoothly switch the number of operating phases according to the load conditions, thereby effectively expanding the high-efficiency operating range.

[0007] In one embodiment, a multi-mode control method for a multiphase LLC resonant converter, the converter comprising N parallel-connected LLC resonant cavities and transformers, where N is an integer greater than or equal to 2, includes: real-time monitoring of load parameters; determining the operating mode based on the load range into which the load parameters fall; and executing drive control corresponding to the operating mode; the operating modes include at least a partial-phase operating mode and a full-phase operating mode; in the partial-phase operating mode, only M phases of the N phases are enabled, where M is a positive integer less than N, and the drive signals of the enabled phases are 360° apart. / N phase difference; in full-phase operation mode, enable all N phase drive signals, and the enabled phase drive signals have a phase difference of 360° / N; when the load parameter change triggers the operation mode switching and a new phase needs to be put into operation, a smooth switching step is performed: make the switch drive signal of the new phase the same as the real-time frequency and duty cycle of the currently operating phase; after the switch of the new phase starts to work, and after the resonant capacitor voltage of the LLC resonant converter reaches a stable resonant state, then turn on the synchronous rectification drive signal of the new phase.

[0008] In one scheme, when N=3, the load range includes a light load range, a medium load range, and a heavy load range, and the corresponding operating modes are single-phase operating mode, two-phase interleaved operating mode, and three-phase interleaved operating mode, respectively; wherein, in the two-phase interleaved operating mode, the phase difference between the two-phase drive signals is 120°; in the three-phase interleaved operating mode, the three-phase drive signals are sequentially out of phase by 120°.

[0009] In one alternative, after the switching transistor of the new phase starts working, the resonant capacitor of the LLC resonant converter is precharged for a predetermined delay time or by setting a pre-charging circuit, so that the voltage of the resonant capacitor reaches a stable resonant state before the synchronous rectification drive signal of the new phase is turned on.

[0010] In one alternative, the stable resonant state refers to the median value of the resonant capacitor voltage having stabilized.

[0011] In one alternative embodiment, the multiphase LLC resonant converter is a half-bridge LLC resonant converter, wherein the median voltage of the resonant capacitor is approximately half the input voltage.

[0012] In one alternative, the multiphase LLC resonant converter is a full-bridge LLC resonant converter, and the median of the resonant capacitor voltage is near the input voltage.

[0013] In one alternative, if the resonant capacitor voltage requires A switching cycles to reach stability, the delay time is set to B switching cycles, where B is an integer greater than A.

[0014] In one alternative, if it takes A switching cycles for the resonant capacitor voltage to stabilize, the delay time is set to B switching cycles, where B equals twice A.

[0015] In one alternative, the load parameter is the output current or output power; the load range is divided by comparing the output current or output power with a preset first threshold and an Nth threshold.

[0016] In another embodiment, this application provides a multiphase LLC resonant converter that performs the multimodal control method described above.

[0017] The beneficial effects of this application are: Significantly improves efficiency over a wide load range and optimizes weighted average efficiency: By intelligently shutting down some resonant units in the low to medium load range, the idle circulating current loss and core loss of redundant phases are completely eliminated.

[0018] A universal, smooth, and reliable mode switching is achieved: the proposed "parameter maintenance" and "delayed input" mechanisms constitute a universal smooth switching framework. It ensures that the new phase remains the same as the original phase in both electrical state (resonance establishment) and control state (frequency, duty cycle), enabling seamless integration with the system and avoiding voltage and current surges and loop disturbances during switching, resulting in high reliability.

[0019] The control is robust and easy to implement: the switching logic is based on the inherent resonant settling time of the circuit, and the delay parameter setting has sufficient margin, making it insensitive to component differences and changes in operating conditions. This scheme does not require complex real-time calculations and state observations, and is easy to implement on a digital controller.

[0020] With wide applicability and strong scalability, the method is applicable in principle to parallel LLC systems with any number of phases (N≥2), providing a general solution to the light-load efficiency problem of such topologies. In particular, its implementation scheme for three-phase topologies perfectly meets the application requirements of automotive power supplies and other applications with extremely high efficiency and reliability requirements. Attached Figure Description

[0021] Figure 1 The schematic diagram of an existing half-bridge three-phase parallel LLC resonant converter; Figure 2 This is a schematic diagram of the half-bridge two-phase parallel LLC topology control switching from single-phase to two-phase drive control in some embodiments of this application; Figure 3 and Figure 4 This is a schematic diagram of the half-bridge three-phase parallel LLC topology control waveforms in some embodiments of this application, showing the switching from single-phase to two-phase and from two-phase to three-phase drive control. Detailed Implementation The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application. Similarly, the following examples are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, methods, processes, or other characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0023] Please see Figure 1This is a three-stage parallel half-bridge LLC resonant converter (hereinafter referred to as "LLC" for ease of description). In two-phase operation, the upper two sets of half-bridge LLC operate; in three-phase operation, all three sets of half-bridge LLC operate. Conventional two-phase LLC topologies operate simultaneously under no-load, low-load, and full-load conditions, while conventional three-phase LLC topologies operate simultaneously under the same conditions. Although frequency reduction or intermittent operation can be used to reduce power consumption and improve efficiency under light load and no-load conditions, the transformer still operates in the first and third quadrants. In two-phase operation, eight power transistors need to be driven, and in three-phase operation, twelve power transistors need to be driven. This results in significant control losses, switching losses, and transformer iron losses, making this type of control generally inefficient under light load conditions.

[0024] Based on this, this application proposes a multi-mode control method. Taking two-phase operation as an example, one phase is shut down when operating under low output load, with only a single phase operating; when the load is heavy, it switches to two-phase operation. Alternatively, taking three-phase operation as an example, one phase is shut down when operating in the light load area, with only a single phase operating; it switches to two-phase operation in the medium load area and switches to three-phase operation in the heavy load area, thereby matching the load point with a higher main power efficiency operating mode. Furthermore, when load changes trigger operating mode switching and a new phase needs to be engaged, smooth transition control and shock-free switching are achieved during mode switching, as shown in the following embodiments.

[0025] In some embodiments, a multi-mode control method for a multiphase LLC resonant converter is provided. The converter includes N parallel LLC resonant cavities and transformers, where N is an integer greater than or equal to 2. The method includes: real-time monitoring of load parameters; determining the operating mode based on the load range into which the load parameters fall; and executing drive control corresponding to the operating mode. The operating modes include at least a partial-phase operating mode and a full-phase operating mode. In the partial-phase operating mode, only M phases of the N phases are enabled, where M is a positive integer less than N, and the enabled phase drive signals have a phase difference of 360° / N. In the full-phase operating mode, all N phase drive signals are enabled, and the enabled phase drive signals have a phase difference of 360° / N.

[0026] When a change in load parameters triggers a switching of operating modes and a new phase needs to be introduced, a smooth switching step is performed: the switching drive signal of the new phase is made to be the same as the real-time frequency and duty cycle of the currently operating phase. After the switching transistor of the new phase starts working, the synchronous rectification drive signal of the new phase is turned on after the resonant capacitor voltage of the LLC resonant converter reaches a stable resonant state.

[0027] As an example, a multi-mode control method for a multiphase LLC resonant converter is provided. The converter includes N parallel LLC resonant cavities and transformers, where N is an integer greater than or equal to 2. The multi-mode control method for the multiphase LLC resonant converter includes the following steps: First, load monitoring and mode decision-making are performed. Load parameters such as the converter's output current or output power are sampled in real time. Based on preset load thresholds, the load is divided into different intervals, and different operating modes are determined accordingly. The operating modes include at least partial-phase operating modes and full-phase operating modes. In partial-phase operating modes, only M phases out of the N phases are enabled (M is a positive integer less than N); in full-phase operating modes, all N phases are enabled.

[0028] Secondly, phase drive control based on the current mode is executed. In partial-phase operation mode, the controller generates drive signals only for the M-phase switches and maintains a 360° / N phase difference between these drive signals, while completely disabling the drive of the remaining phases. In full-phase operation mode, the controller generates drive signals for all N-phase switches and maintains a 360° / N phase difference between each phase.

[0029] When a load change triggers a switching of operating modes and a new phase needs to be engaged, the following steps are performed to achieve smooth transition control and shock-free switching during mode switching: Step one: Maintain frequency and duty cycle. For a new phase about to be introduced, the initial drive frequency and duty cycle of its switching transistor are not recalculated or default values ​​are adopted. Instead, they are kept the same as the real-time drive frequency and duty cycle of any currently operating phase (the main phase). This ensures the continuity of the control loop at the moment of switching.

[0030] Step 2: Resonance state pre-establishment and synchronous rectification delayed start-up. The upper and lower bridge arm switches of the new phase start working according to the parameters of any one of the currently operating phases, but the drive signal of the corresponding secondary synchronous rectifier is temporarily blocked, so that the resonant cavity is in a near-no-load resonance establishment state in the initial stage.

[0031] Step 3: Enable delayed synchronous rectification. The controller initiates a preset delay time T_delay. After T_delay ends, the synchronous rectification drive signal of the new phase is enabled, thus fully connecting the phase to the output terminal and enabling it to participate in energy transfer.

[0032] The control method described in this application can significantly improve efficiency over a wide load range and optimize weighted average efficiency: by intelligently shutting down some resonant units in the low-to-medium load range, the no-load circulating current loss and core loss of redundant phases are completely eliminated. Actual measurements show that in a 3000W three-phase LLC application, the 5% load point efficiency can be significantly improved from 86.3% to 96.6%, effectively optimizing energy efficiency across the entire operating load spectrum.

[0033] The control method proposed in this application achieves universal, smooth, and reliable mode switching: the proposed "parameter maintenance" and "delayed input" mechanisms constitute a universal smooth switching framework. It ensures that the new phase can seamlessly connect with the system in both electrical state (resonance establishment) and control state (frequency, duty cycle), avoiding voltage and current surges and loop disturbances during switching, thus achieving high reliability.

[0034] The control method proposed in this application exhibits strong control robustness and is easy to implement: the switching logic is based on the inherent resonant settling time of the circuit, the delay parameter setting has sufficient margin, and it is insensitive to component differences and changes in operating conditions. This scheme does not require complex real-time calculations and state observations, and is easy to implement on a digital controller.

[0035] The control method presented in this application has a wide range of applications and strong scalability: in principle, the method is applicable to parallel LLC systems with any number of phases (N≥2), providing a general solution to the light-load efficiency problem of such topologies. In particular, its implementation scheme for three-phase topologies perfectly meets the application requirements of automotive power supplies and other applications with extremely high efficiency and reliability requirements.

[0036] In some implementations, the delay time T_delay is set based on the circuit's physical characteristics. As an example, after the switch of the new phase starts operating, the resonant capacitor voltage of the LLC resonant converter can reach a stable resonant state within a predetermined delay time, where the delay time T_delay is the time required for the resonant capacitor voltage to reach a stable resonant state after the new phase is activated. In some examples, a pre-charging circuit can be used to pre-charge the resonant capacitor of the LLC resonant converter, allowing the resonant capacitor voltage to reach a stable resonant state before finally activating the synchronous rectification drive signal for the new phase. In other examples, the multiphase LLC resonant converter is a half-bridge LLC resonant converter, with the median resonant capacitor voltage near half the input voltage. In some examples, the multiphase LLC resonant converter is a full-bridge LLC resonant converter, with the median resonant capacitor voltage near the input voltage. In some examples, if it takes A switching cycles for the resonant capacitor voltage to stabilize, the delay time is set to B switching cycles, where B is an integer greater than A. In another example, if it takes A switching cycles for the resonant capacitor voltage to stabilize, then the delay time is set to B switching cycles, where B is equal to twice A.

[0037] In some implementations, the load parameter is the output current or output power; the load range is divided by comparing the output current or output power with a preset first threshold and an Nth threshold.

[0038] In some embodiments, this application provides a multimode control method for a two-phase LLC resonant converter. Please refer to... Figure 2 Taking the driving control of a set of active and passive transistors in each phase as an example, the control method includes driving the active transistor G_Q1 and its corresponding synchronous transistor G_Q8 in the first phase, and driving the active transistor G_Q3 and its corresponding synchronous transistor G_Q10 in the second phase.

[0039] During the t0 to t1 phase: a light-load single-phase operating state, only the first LLC group is working.

[0040] During the t1 to t2 phase: when the load exceeds the switching threshold, the system enters a two-phase working state. The main driver G_Q3 of the second phase is 180° out of phase with the driver G_Q1 of the first phase. The frequency and duty cycle follow the original first phase driver. At the same time, all the synchronous tubes of the second phase are turned on after a delay. This ensures that when switching between two phases, there will be no current backflow caused by the synchronous tubes being turned on due to the voltage at the output, or the magnetic field of the second phase transformer being unbalanced, which would lead to unstable output.

[0041] During the t2 to t3 phase: the second phase main drive G_Q3 operates normally while the first phase main drive G_Q1 is turned on 180° out of phase, maintaining a consistent duty cycle and frequency until the second phase reaches a stable resonance state. The median voltage of the resonant capacitor in the half-bridge LLC stabilizes around Vin / 2, typically requiring A cycles. This time can usually be determined through measurement, theoretical calculation, or simulation. For reliability, the synchronizing tube's on-time is extended by B cycles, where B is typically set to twice A. This ensures that the magnetic field and resonant state of the second phase are stable before the synchronizing tube is turned on. This control method ensures a smooth, stable, and reliable synchronizing tube intervention.

[0042] In some implementations, this application provides a multi-mode control method for a three-phase LLC resonant converter. Please refer to [link to relevant documentation]. Figure 3 and Figure 4 Taking the driving control of a set of active and passive transistors in each phase as an example, the control method includes driving the active transistor G_Q1 and its corresponding synchronous transistor G_Q8 in the first phase, driving the active transistor G_Q3 and its corresponding synchronous transistor G_Q10 in the second phase, and driving the active transistor G_Q5 and its corresponding synchronous transistor G_Q12 in the third phase.

[0043] Three-phase LLC control timing for switching from single-phase to two-phase operation: During the t0 to t1 phase: only single-phase operation is performed in the light load region, and only the first set of LLCs is in operation.

[0044] During the transition from t1 to t2: the load switches from the light load area to the medium load area and enters the two-phase working state. The main driver G_Q3 of the second phase is 120° out of phase with the driver G_Q1 of the first phase. The frequency and duty cycle follow the original first phase driver. At the same time, all the synchronous tubes of the second phase are turned on after a delay. This ensures that when switching between two phases, there will be no current backflow caused by the synchronous tubes being turned on due to the voltage at the output, the magnetic field of the second phase transformer being unbalanced, and thus the output being unstable.

[0045] During the t2 to t3 phase: the second phase main drive G_Q3 operates normally while the first phase main drive G_Q1 is turned on at a 120° phase shift, maintaining a consistent duty cycle and frequency until the second phase reaches a stable resonance state. The median voltage of the resonant capacitor in the half-bridge LLC stabilizes around Vin / 2, typically requiring A cycles. This time can usually be determined through measurement, theoretical calculation, or simulation. For reliability, the synchronizing tube's on-time is extended by B cycles, where B is typically set to twice A. This ensures that the magnetic field and resonant state of the second phase are stable before the synchronizing tube is turned on. This control method ensures a smooth, stable, and reliable synchronizing tube intervention.

[0046] Three-phase LLC control timing for switching from two-phase to three-phase operation: During the t0 to t1 phase: in the intermediate load region, the two phases operate normally, the second phase main drive G_Q3 is normally driven and the first phase main drive G_Q1 is turned on with a 120° phase shift, the duty cycle and frequency are kept consistent, and the two phase synchronization tubes are normally turned on.

[0047] During the transition from t1 to t2: the load switches from the medium load area to the heavy load area and enters the three-phase working state. The main driver of the third phase, G_Q5, is out of phase with the main driver of the first phase, G_Q1, by 240°. The frequency and duty cycle follow the original first phase driver. At the same time, all the synchronizing tubes of the third phase are turned on after a delay. This ensures that when switching between the three phases, there will be no current backflow caused by the synchronizing tubes being turned on due to the voltage at the output, or the magnetic field of the third phase transformer being unbalanced, resulting in unstable output.

[0048] During the t2 to t3 phase: the third-phase main drive G_Q5 and the first-phase main drive G_Q1 are switched on at a 240° phase shift, maintaining the same duty cycle and frequency, until the third phase reaches a stable resonance state. The median voltage of the resonant capacitor of the half-bridge LLC stabilizes around Vin / 2, typically requiring A cycles. This time can usually be obtained through actual measurement, theoretical calculation, or simulation. For reliability, the synchronizing tube's on-time is extended by B cycles, where B is typically set to twice A. This ensures that the magnetic field and resonant state of the third phase are stable before the synchronizing tube is switched on. This control method ensures a smooth, stable, and reliable synchronizing tube intervention.

[0049] In some embodiments, this application provides a multiphase LLC resonant converter that performs the multimode control method described above.

[0050] The above are merely some embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, and substitutions to the above embodiments within the scope of this application.

Claims

1. A multi-mode control method for a multiphase LLC resonant converter, the converter comprising N-phase parallel-connected LLC resonant cavities and transformers, wherein N is an integer greater than or equal to 2, comprising: The system monitors load parameters in real time, determines the operating mode based on the load range into which the load parameters fall, and executes drive control corresponding to the operating mode. The operating modes include at least a partial phase operating mode and a full phase operating mode; in the partial phase operating mode, only M phases of N phases are enabled, where M is a positive integer less than N, and the enabled phase drive signals have a phase difference of 360° / N. In the full-phase operating mode, all N phase drive signals are enabled, and there is a 360° / N phase difference between the enabled phase drive signals; characterized in that: When the change in load parameters triggers the switching of the working mode and a new phase needs to be put into operation, a smooth switching step is performed: the switching transistor drive signal of the new phase is the same as the real-time frequency and duty cycle of the currently working phase. After the switching transistor of the new phase starts working, the synchronous rectification drive signal of the new phase is turned on after the resonant capacitor voltage of the LLC resonant converter reaches a stable resonant state.

2. The multimodal control method according to claim 1, characterized in that, When N=3, the load range includes a light load range, a medium load range, and a heavy load range, and the corresponding operating modes are a single-phase operating mode, a two-phase interleaved operating mode, and a three-phase interleaved operating mode, respectively; wherein, in the two-phase interleaved operating mode, the phase difference between the two-phase drive signals is 120°; in the three-phase interleaved operating mode, the three-phase drive signals are sequentially out of phase by 120°.

3. The multimodal control method according to claim 1 or 2, characterized in that, After the switching transistor of the new phase starts working, after a predetermined delay time or by setting a pre-charging circuit to pre-charge the resonant capacitor of the LLC resonant converter, so that the voltage of the resonant capacitor reaches a stable resonant state, the synchronous rectification drive signal of the new phase is then turned on.

4. The multimodal control method according to claim 3, characterized in that, The stable resonance state refers to the fact that the median value of the resonant capacitor voltage has stabilized.

5. The multimodal control method according to claim 3, characterized in that, The multiphase LLC resonant converter is a half-bridge LLC resonant converter, and the median value of the resonant capacitor voltage is approximately half the input voltage.

6. The multimodal control method according to claim 3, characterized in that, The multiphase LLC resonant converter is a full-bridge LLC resonant converter, and the median value of the resonant capacitor voltage is near the input voltage.

7. The multimodal control method according to claim 3, characterized in that, If it takes A switching cycles for the resonant capacitor voltage to reach stability, then the delay time is set to B switching cycles, where B is an integer greater than A.

8. The multimodal control method according to claim 3, characterized in that, If it takes A switching cycles for the resonant capacitor voltage to reach stability, then the delay time is set to B switching cycles, where B is equal to twice A.

9. The multimodal control method according to claim 1 or 2, characterized in that, The load parameter is the output current or output power; the load range is divided by comparing the output current or output power with a preset first threshold and an Nth threshold.

10. A multiphase LLC resonant converter, characterized in that, The resonant converter performs the multimodal control method as described in any one of claims 1 to 9.

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