Multi-phase parallel LLC resonant converter current sharing control system based on nonlinear capacitor

Abstract

The invention relates to the field of multi-module converter control, and provides a multi-phase parallel LLC resonant converter current sharing control system based on a nonlinear capacitor, which comprises N LLC modules with parallel outputs and parallel inputs, non-linear capacitors are arranged in N-1 LLC modules, the non-linear capacitor in a single LLC module serves as a resonant capacitor of the LLC resonant converter to be connected into an LLC resonant circuit, and the Nth module is an uncompensated reference module; the LLC resonant circuit comprises a power supply, a half-bridge inverter, a nonlinear capacitor, an ideal transformer, a rectification filter circuit and a filter capacitor; one end of the nonlinear capacitor is connected with the midpoint of a bridge arm of the half-bridge inverter, and the other end of the nonlinear capacitor is connected with the primary side of the ideal transformer; the nonlinear capacitor comprises a switching tube Q, an LC filter and a shunt capacitor CP; a variable phase delay angle is applied to a driving signal of a switching tube Q relative to a driving signal of a half-bridge inverter so as to change a capacitance value of a nonlinear capacitor, and gain deviation caused by parameter deviation of a resonant element is compensated.

Description

Technical Field

[0001] This invention relates to the field of multi-module converter control, and more particularly to a current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors. Background Technology

[0002] LLC resonant converters are common power electronic converters, offering advantages such as simple structure, high efficiency, high power density, and low electromagnetic interference. However, a single LLC resonant converter is prone to significant current ripple during operation. While increasing the filter capacitor can reduce current ripple, this limits the converter's reliability and increases system design complexity. To address these issues, a parallel structure of multi-phase LLC resonant converters can reduce current ripple while improving reliability. However, due to manufacturing processes, operating environment, and component losses, resonant components in different phases may experience parameter shifts, preventing current balance between modules and severely impacting system efficiency and lifespan. In actual production, the resonant capacitor tolerance can reach ±10%, leading to current deviations of >25% in parallel modules. Therefore, this patent proposes a current sharing control system for multi-phase parallel LLC resonant converters based on nonlinear capacitors. Summary of the Invention

[0003] The purpose of this invention is to provide a current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors, which can compensate for circuit gain when the parameters of the resonant elements deviate, so as to realize the current sharing control of the multiphase LLC resonant converter in parallel.

[0004] To address the aforementioned technical problems, this invention provides a current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors, comprising N LLC modules, where N≥2, and the outputs and inputs of the N LLC modules are connected in parallel; the nonlinear capacitors are set in N-1 LLC modules, and in a single LLC module, the nonlinear capacitors are connected to the LLC resonant circuit as the resonant capacitors of the LLC resonant converter; the Nth module is an uncompensated reference module.

[0005] The LLC resonant circuit includes a power supply, a half-bridge inverter, a nonlinear capacitor, an ideal transformer, a rectifier-filter circuit, and a filter capacitor. One end of the nonlinear capacitor is connected to the midpoint of the bridge arm of the half-bridge inverter, and the other end is connected to the primary side of the ideal transformer. The nonlinear capacitor includes a switching transistor Q, an LC filter, and a parallel capacitor C. P ;

[0006] By applying a variable phase delay angle to the drive signal of the switch Q relative to the drive signal of the half-bridge inverter. The capacitance value of the nonlinear capacitor is changed to compensate for the gain deviation caused by the parameter offset of the resonant element.

[0007] In a preferred embodiment, the LC filter includes a filter capacitor C. C and filter inductor L C The positive terminal of the nonlinear capacitor is connected to the filter capacitor C. C Its negative terminal is connected to the filter inductor L. C The LC filter, after being connected in series with the switching transistor Q, is connected as a whole with the parallel capacitor C. P in parallel.

[0008] In a preferred embodiment, the parallel capacitor C P One end is connected to the filter capacitor C C Connect the switch Q to the filter inductor L, and connect the other end of the switch Q to the filter inductor L. C Connected;

[0009] Wherein, the filter capacitor C C and filter inductor L C Satisfies the series resonance relationship:

[0010] In a preferred embodiment, the filter capacitor C C and filter inductor L C Satisfying the resonant frequency relationship of the LLC resonant converter: L C C C =L r1 C r1 , where L r1 Resonant inductance, C r1 It is a resonant capacitor.

[0011] In a preferred embodiment, the driving signal for the switch Q is a square wave signal with a 50% duty cycle, and its operating frequency is the same as the operating frequency f of the LLC resonant converter inverter half-bridge. s Maintain consistency; operating frequency f s Satisfy the following formula: Among them, L r1 Resonant inductance, C r1 It is a resonant capacitor.

[0012] In a preferred embodiment, when the system is in a steady state, the equivalent impedance Z of the nonlinear capacitor is... r Satisfy the following formula: The port of the nonlinear capacitor is capacitive, and in a steady state, the port voltage lags the port current phase by π / 2.

[0013] In a preferred embodiment, the half-bridge inverter includes a half-bridge switching transistor composed of switching transistors S1 and S2 connected in series; the half-bridge switching transistor is controlled by inputting a drive signal with a 50% duty cycle and a switching frequency equal to the system operating frequency onto the gates of switching transistors S1 and S2.

[0014] In a preferred embodiment, the turns ratio of the ideal transformer is n:1:1; the rectifier and filter circuit adopts a zero-wave rectifier circuit.

[0015] In a preferred embodiment, in N LLC modules, the output current I of the rectifier filter circuit of the Nth offset phase is... 0N The current is compared with the set current sharing value, and the output current I in the offset phase is... 0N If the preset value is not reached, PID control is used to apply a certain delay angle of turn-on and turn-off signals to the switch Q until the output current reaches the preset value and the circuit stabilizes.

[0016] In a preferred embodiment, when the switch Q is turned off, the LC filter is not connected to the LLC resonant circuit, and at this time, all the current in the resonant circuit flows through the parallel capacitor C. P When the switch Q is turned on, a reverse current will be generated in the LC filter circuit, causing the resonant circuit current to intersect with the current flowing through the parallel capacitor C. P The current generates a current difference; the switching of the switch Q in one switching cycle is determined by the phase delay angle. To control.

[0017] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0018] 1. This invention is based on the existing parallel structure multiphase LLC resonant converter. By connecting a nonlinear capacitor as the resonant capacitor, it can compensate for the circuit gain when the parameters of the resonant element deviate, so as to realize the current sharing control of the parallel multiphase LLC resonant converter.

[0019] 2. Compared with traditional inverter bridge control and rectifier circuit control, this invention compensates for the parameters of resonant components by controlling the phase shift angle of the drive signal of the switching transistor inside the nonlinear capacitor, which is a simple control method.

[0020] 3. The nonlinear capacitor used in this invention only requires the addition of one switching transistor, one inductor, and one capacitor, resulting in relatively low cost.

[0021] 4. The nonlinear capacitor proposed in this invention can achieve zero-current switching (ZCS) with minimal additional losses.

[0022] 5. The nonlinear capacitor proposed in this invention can be plugged in and out online with a fast response speed. Attached Figure Description

[0023] Figure 1 This is a diagram showing the offset phase structure of a parallel LLC resonant circuit based on a nonlinear capacitor in a preferred embodiment of the present invention.

[0024] Figure 2 This is a diagram of the nonlinear capacitor structure of the current sharing control system of a multiphase parallel LLC resonant converter based on nonlinear capacitors in a preferred embodiment of the present invention.

[0025] Figure 3 This is a key waveform diagram of the LLC resonant circuit based on nonlinear capacitance in a preferred embodiment of the present invention;

[0026] Figure 4 This is a circuit diagram of the offset phase of the nonlinear capacitor in a preferred embodiment of the present invention;

[0027] Figure 5 This is a graph showing the relationship between the ratio of the nonlinear capacitor to the standard capacitor in a preferred embodiment of the present invention and the phase shift angle.

[0028] Figure 6 This is a comparison diagram of the current sharing effect of the system under 25% load conditions in a preferred embodiment of the present invention (wherein) Figure 6 a is the waveform diagram of the circuit without NC connection. Figure 6 b is a waveform diagram of the circuit with NC connection);

[0029] Figure 7 This is a comparison diagram of the current sharing effect of the system under 100% load conditions in a preferred embodiment of the present invention;

[0030] Figure 8 This is an experimental diagram illustrating the transient effect of hot-swapping of the switching transistor Q in a preferred embodiment of the present invention. Figure 8 a is the transient diagram of the switch being turned off and on. Figure 8 b is the transient diagram of the switch being turned on and off. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0032] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0034] Compared to a single LLC resonant converter, a multiphase LLC resonant converter with a parallel structure offers advantages such as low ripple and high reliability. However, due to potential parameter differences in the resonant elements of different LLC modules, an unbalanced distribution of operating current can occur between the system modules when the LLC resonant converters are running in parallel. This leads to reduced system efficiency, uneven thermal stress between modules, affects system lifespan, and reduces system stability and reliability. Therefore, this invention proposes a current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors, which offers advantages such as simple structure, simple control, low loss, low current stress, wide compensation range, and online pluggability.

[0035] Reference Appendix Figures 1-2 This invention provides a current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors, comprising N LLC modules, where N≥2, and the outputs and inputs of the N LLC modules are connected in parallel. The nonlinear capacitors are configured in N-1 LLC modules, and in each LLC module, the nonlinear capacitor serves as the resonant capacitor of the LLC resonant converter, connected to the LLC resonant circuit. The Nth module is an uncompensated reference module. The LLC resonant circuit includes a power supply, a half-bridge inverter, a nonlinear capacitor, an ideal transformer, a rectifier filter circuit, and a filter capacitor. One end of the nonlinear capacitor is connected to the midpoint of the bridge arm of the half-bridge inverter, and the other end is connected to the primary side of the ideal transformer. The nonlinear capacitor includes a switching transistor Q, an LC filter, and a parallel capacitor C. P By applying a variable phase delay angle to the drive signal of the switch Q relative to the drive signal of the half-bridge inverter. The capacitance value of the nonlinear capacitor is changed to compensate for the gain deviation caused by the parameter offset of the resonant element.

[0036] The nonlinear capacitor consists of a switching transistor Q, an LC filter, and a parallel capacitor C. P Parallel capacitor C P This is the resonant capacitor in the original LLC resonant circuit, and the switch Q is a MOS switch. After connecting this nonlinear capacitor as a whole into the LLC resonant converter circuit, the current balance of the multi-phase parallel LLC resonant converter can be achieved by adjusting the phase difference between the switch Q and the inverter half-bridge in the half-bridge inverter.

[0037] The LC filter includes a filter capacitor C. C and filter inductor L C The positive terminal of the nonlinear capacitor is connected to the filter capacitor C. C Its negative terminal is connected to the filter inductor L. C The LC filter, after being connected in series with the switching transistor Q, is connected as a whole with the parallel capacitor C. P in parallel.

[0038] The parallel capacitor C P One end is connected to the filter capacitor C C Connect the switch Q to the filter inductor L, and connect the other end of the switch Q to the filter inductor L. C Connected; wherein, the filter capacitor C C and filter inductor L C Satisfies the series resonance relationship: The filter capacitor C C and filter inductor L C Satisfying the resonant frequency relationship of the LLC resonant converter: L C C C =L r1 C r1 , where L r1 Resonant inductance, C r1 This is a resonant capacitor. The driving signal for the switch Q is a square wave signal with a 50% duty cycle, and its operating frequency is the same as the operating frequency f of the LLC resonant converter inverter half-bridge. s Maintain consistency; operating frequency f s Satisfy the following formula: Among them, L r1 Resonant inductance, C r1 It is a resonant capacitor.

[0039] The LLC resonant circuit used in this invention has the following characteristics:

[0040] The half-bridge inverter includes a half-bridge switching transistor composed of switching transistors S1 and S2 connected in series; it adopts a complementary drive signal with a duty cycle of 50%; the control method of the half-bridge switching transistor is to input a drive signal with a 50% duty cycle and a switching frequency equal to the system operating frequency on the gates of switching transistors S1 and S2.

[0041] The resonant circuit consists of a resonant capacitor (C) r ), resonant inductor (L) r Magnetizing inductance (L) m The ideal transformer is composed of n:1:1 turns ratio; the rectifier and filter circuit adopts a zero-type full-wave rectifier circuit.

[0042] In N LLC modules, the output current I of the rectifier filter circuit of the Nth offset phase is... 0N The current is compared with the set current sharing value, and the output current I in the offset phase is... 0N If the preset value is not reached, PID control is used to apply a certain delay angle of turn-on and turn-off signals to the switch Q until the output current reaches the preset value and the circuit stabilizes.

[0043] For ease of analysis, in the N LLC modules, the first phase is used as the reference standard phase (resonant capacitor C). r1 Resonant inductor L r1 The second phase is used as the parameter offset phase. When the resonant capacitance C of the offset phase... r2 (or resonant inductance L) r2 When parameter offset occurs, the output current I obtained after rectification and filtering circuit is... 02 If the current sharing value deviates from the set value, PID control is used to apply a delayed turn-on and turn-off signal to the switching transistor Q until the output current reaches the preset value and the circuit stabilizes.

[0044] When the system is in a steady state, the equivalent impedance Z of the nonlinear capacitor r Satisfy the following formula: The ports of the nonlinear capacitor are capacitive, and in a steady state, the port voltage lags behind the port current phase.

[0045] The following is in conjunction with the appendix Figures 3-8 The invention will be further illustrated by examples:

[0046] Taking a single offset phase as the analysis object, for a multi-phase parallel LLC resonant converter system, the current imbalance caused by the offset of parameter components stems from the gain imbalance resulting from the parameter offset. Therefore, for an LLC resonant converter with a nonlinear capacitor, when the parameters of components such as the resonant capacitor or resonant inductor shift, the circuit can change the equivalent capacitance value of the nonlinear capacitor according to the offset to achieve gain balance among phases, thereby achieving the purpose of output current sharing.

[0047] The key waveforms of the LLC resonant circuit based on nonlinear capacitance are as follows: Figure 3 As shown in the waveform diagram, when the switch Q is turned off, the LC filter is not connected to the LLC resonant circuit. At this moment, all the current in the resonant circuit flows through the parallel capacitor C. P When the switch Q is turned on, a reverse current will be generated in the LC filter circuit, causing the resonant circuit current to intersect with the current flowing through the parallel capacitor C. P The current generates a current difference. In this way, the change in the resonant circuit impedance caused by the offset of the compensation component parameters is achieved. The switching on and off of the switching transistor in one switching cycle is determined by the phase delay angle. Therefore, controlling only one parameter is sufficient to control the current sharing of the entire parallel system. The phase delay angle between the drive signal of the nonlinear capacitor's switching transistor Q and the switching transistor S1 in the half-bridge inverter is... Resonant current i Lr Satisfy: i Lr =i Cc +i Cp .

[0048] Overall, the phase relationship between the port current and voltage of the nonlinear capacitor exhibits capacitive characteristics. Further analysis of the nonlinear capacitor using the fundamental frequency analysis method yields the following results: Figure 4 The diagram shows the offset phase equivalent circuit. Where V... P V represents the output voltage of the half-bridge inverter circuit. Cr R represents the nonlinear capacitor port voltage. ac It is the equivalent resistance of the transformer and rectifier, expressed by the following formula: Where n is the transformer turns ratio, R L Let be the system load resistance. For the nonlinear capacitor component, its impedance is expressed as:

[0049]

[0050] Where ω = 2πfs. Therefore, C r The port exhibits capacitive characteristics, with the port voltage lagging the resonant current by π / 2 phase. Based on this phase relationship, the input voltage V can be obtained. P The phase difference with the resonant current is

[0051] By analyzing the equivalent circuit again, the circuit input impedance Z can be obtained. in for:

[0052]

[0053] The impedance Z can be obtained through the equivalent relationship between the real and imaginary parts. LC The expression:

[0054]

[0055] The equivalent capacitance C of the nonlinear capacitor r It can be represented as:

[0056]

[0057] From the above formula, the ratio of the nonlinear capacitor to the standard capacitor and the phase delay angle can be plotted as follows: Relationships, such as Figure 5 As shown, the equivalent capacitance of a nonlinear capacitor exhibits a nonlinear changing trend with the phase shift angle, hence the name "nonlinear capacitor." The equivalent capacitance of a nonlinear capacitor can have both positive and negative values, meaning it can exhibit either capacitive or inductive characteristics, and its variable range is wide.

[0058] To verify the correctness of the control method, an experiment was conducted on the current sharing control system of the multiphase parallel LLC resonant converter based on nonlinear capacitors. The experimental parameters are designed as follows:

[0059] Devices parameter Devices parameter <![CDATA[Input voltage V in > 400V <![CDATA[Output voltage V out > 48V <![CDATA[Single-phase resonant inductor L r1 > 30uH <![CDATA[Two-phase resonant inductor L r1 > 30uH <![CDATA[One-phase excitation inductance L m1 > 300uH <![CDATA[Two-phase excitation inductance L m2 > 300uH <![CDATA[Single-phase resonant capacitor C r1 > 33nF <![CDATA[Two-phase parallel capacitor C p > 38nF <![CDATA[Filter capacitor C O > 100uF Transformer turns ratio n 4:1:1 <![CDATA[Filter capacitor C C > 33nF <![CDATA[Filter inductor L C > 30uH

[0060] The following conclusions can be drawn:

[0061] (1) Figure 6 The experimental waveforms are depicted when the circuit is subjected to a 25% load. Without an NC (non-conductive) connection, the output current of the two phases of the system exhibits significant non-uniformity. When an NC is inserted to control the resonant frequency of the bias phase, the output current of the two phases of the system achieves good current sharing.

[0062] (2) A load change experiment was conducted on the system, and the experimental waveform is shown below. Figure 7 As shown, when the load jumps from 25% to 100%, the system can re-establish the current balance in a very short time, with a response time of less than 8ms.

[0063] (3) To confirm that the nonlinear capacitor structure achieves ZCS, the waveform of the switch Q and the current at the nonlinear capacitor port under current balancing conditions were collected, such as... Figure 8As shown. At the instant the switch is turned on, the drain-source voltage V... ds_Q The drain current i drops rapidly. ds_Q with i Cc It is the same current signal, with an effective value of approximately 0.2A. This results in extremely low switching losses. During the turn-off process of the switching transistor Q, the switching branch opens, and the current i... ds_Q It remains at 0. Therefore, the ZCS of the nonlinear capacitance is verified.

[0064] As can be seen from the above, this invention effectively solves the problem of unbalanced operating current between system modules caused by parameter differences in the resonant elements of different LLC modules. The current sharing control method based on nonlinear capacitors can be extended from a two-phase LLC parallel structure to an N-phase structure.

[0065] The above examples are merely illustrative of the principles of this invention and are not the only possible implementations. The above embodiments should not be considered as limiting the scope of this invention. Those skilled in the art can make modifications and variations upon reading and understanding the foregoing detailed description. The specific scope of protection should be determined by the claims.

[0066] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A current sharing control system based on a multiphase parallel LLC resonant converter with nonlinear capacitors, characterized in that: It includes N LLC modules, where N≥2, and the outputs and inputs of the N LLC modules are connected in parallel; the nonlinear capacitor is set in N-1 LLC modules, and the nonlinear capacitor in a single LLC module is connected to the LLC resonant circuit as the resonant capacitor of the LLC resonant converter; the Nth module is an uncompensated reference module. The LLC resonant circuit includes a power supply, a half-bridge inverter, a nonlinear capacitor, an ideal transformer, a rectifier-filter circuit, and a filter capacitor. One end of the nonlinear capacitor is connected to the midpoint of the bridge arm of the half-bridge inverter, and the other end is connected to the primary side of the ideal transformer. The nonlinear capacitor includes a switching transistor Q, an LC filter, and a parallel capacitor C. P ; By applying a variable phase delay angle to the drive signal of the switch Q relative to the drive signal of the half-bridge inverter. The capacitance value of the nonlinear capacitor is changed to compensate for the gain deviation caused by the parameter offset of the resonant element.

2. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 1, characterized in that: The LC filter includes a filter capacitor C. C and filter inductor L C The positive terminal of the nonlinear capacitor is connected to the filter capacitor C. C Its negative terminal is connected to the filter inductor L. C The LC filter, after being connected in series with the switching transistor Q, is connected as a whole with the parallel capacitor C. P in parallel.

3. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 2, characterized in that: The parallel capacitor C P One end is connected to the filter capacitor C C Connect the switch Q to the filter inductor L, and connect the other end of the switch Q to the filter inductor L. C Connected; Wherein, the filter capacitor C C and filter inductor L C Satisfies the series resonance relationship:

4. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 1, characterized in that: The filter capacitor C C and filter inductor L C Satisfying the resonant frequency relationship of the LLC resonant converter: L C C C =L r1 C r1 , where L r1 Resonant inductance, C r1 It is a resonant capacitor.

5. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 1, characterized in that: The driving signal for the switch Q is a square wave signal with a 50% duty cycle, and its operating frequency is the same as the operating frequency f of the LLC resonant converter inverter half-bridge. s Maintain consistency; operating frequency f s Satisfy the following formula: Among them, L r1 Resonant inductance, C r1 It is a resonant capacitor.

6. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 1, characterized in that: When the system is in a steady state, the equivalent impedance Z of the nonlinear capacitor r Satisfy the following formula: The port of the nonlinear capacitor is capacitive, and in a steady state, the port voltage lags the port current phase by π / 2.

7. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 1, characterized in that: The half-bridge inverter includes a half-bridge switching transistor consisting of switching transistors S1 and S2 connected in series; the half-bridge switching transistor is controlled by inputting a drive signal with a 50% duty cycle and a switching frequency equal to the system operating frequency onto the gates of switching transistors S1 and S2.

8. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 1, characterized in that: The ideal transformer has a turns ratio of n:1:1; the rectifier and filter circuit adopts a zero-type full-wave rectifier circuit.

9. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 1, characterized in that: In N LLC modules, the output current I of the rectifier filter circuit of the Nth offset phase is... 0N The current is compared with the set current sharing value, and the output current I in the offset phase is... 0N If the preset value is not reached, PID control is used to apply a certain delay angle of turn-on and turn-off signals to the switch Q until the output current reaches the preset value and the circuit stabilizes.

10. The current sharing control system for a multiphase parallel LLC resonant converter based on nonlinear capacitors according to claim 9, characterized in that: When the switch Q is turned off, the LC filter is not connected to the LLC resonant circuit, and at this moment, all the current in the resonant circuit flows through the parallel capacitor C. P When the switch Q is turned on, a reverse current will be generated in the LC filter circuit, causing the resonant circuit current to intersect with the current flowing through the parallel capacitor C. P The current generates a current difference; The switching on and off of the transistor Q in one switching cycle is determined by the phase delay angle. To control.

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