CN110649821A - Bidirectional SCC type LLC resonant converter, circuit and control method thereof - Google Patents

Abstract

The application discloses a bidirectional SCC type LLC resonant converter, a circuit therein and a control method. The LLC resonant circuit includes: a first inductor; a second inductor; the first end of the second inductor is respectively connected with the first end of the transformer and the first end of the first inductor, and the second end of the second inductor is respectively connected with the second end of the transformer and the first end of the inversion/rectification bridge; a capacitor unit; the first end of the capacitor unit is connected with the second end of the first inductor, and the second end of the capacitor unit is used for being connected with the second end of the inverter/rectifier bridge; the capacitance value of the capacitor unit is adjustable, and when the capacitor unit works in the forward direction and the reverse direction, the resonance capacitance value is adjusted, so that the characteristics of the circuit, such as the parameters of a resonance point, a quality factor, gain and the like of the circuit are changed, the gain of the input and output of the reverse working circuit can be greatly changed in an ideal frequency band, and ideal output is finally obtained.

Description

Bidirectional SCC type LLC resonant converter, circuit and control method thereof

technical field

The present application relates to the technical field of LLC resonant circuits, and in particular, to a bidirectional SCC type LLC resonant converter and a circuit and control method therein.

Background technique

A direct current-direct current (DC/DC) converter is a device that converts electrical energy of one voltage value into electrical energy of another voltage value in a DC circuit. Large-scale data centers, aerospace systems, new energy power generation, LED lighting, and electric vehicle charging all place higher and higher requirements on the capacity, efficiency, and power density of DC/DC converters. Therefore, the development of high-efficiency, high-power Density, high reliability DC/DC converters are required for industrial energy saving and applications. The LLC resonant converter is a relatively common DC/DC converter at present. On the one hand, the LLC resonant converter realizes Zero Voltage Switching (ZVS) on the primary side and Zero Current Switching (ZCS) on the secondary side, which greatly reduces the loss of components and has high efficiency. On the one hand, due to the reduction of loss and ease of heat dissipation, the switching frequency can be further increased, and the volume of magnetic components can be further reduced, so that high power density performance can be obtained. Therefore, compared with other DC/DC converters, LLC resonant converters have better performance. High efficiency and higher power density have made LLC resonant converters develop more rapidly, have broader application prospects, and become the mainstream converters in the field of DC/DC converters.

With the development of science and technology, there are more and more demands for bidirectional DC/DC converters. Bidirectional DC/DC converters refer to DC/DC converters that can realize bidirectional flow of energy. To the output, when working in reverse, energy can flow from the output to the input.

In the related art, the traditional LLC resonant converter can directly carry out the bidirectional flow of energy. However, in the case of wide voltage input and output requirements, when the reverse operation is performed, the output terminal becomes the input terminal, and the input terminal becomes the output terminal. In order to achieve the same wide voltage input and output as in the forward operation, the operating frequency will have a wide range of changes, and the range of the operating frequency will often exceed the ideal frequency band, resulting in poor output waveform quality. Harmonics, etc., resulting in a poor effect of realizing the bidirectional flow of energy.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide a bidirectional SCC type LLC resonant converter and a circuit and control method therein, so as to solve the problem of poor output quality when bidirectional energy flow is realized based on the traditional LLC resonant circuit in the related art.

The purpose of this application is achieved through the following technical solutions:

An LLC resonant circuit is applied in a bidirectional SCC type LLC resonant converter, the LLC resonant converter at least includes an inverter/rectifier bridge, a transformer and a rectifier/inverter bridge, and the LLC resonant circuit is used for The inverter/rectifier bridge is connected to the transformer, and the transformer is also connected to the rectifier/inverter bridge; the LLC resonant circuit includes:

first inductance;

A second inductance; the first end of the second inductance is respectively connected to the first end of the transformer and the first end of the first inductance, and the second end is used to connect to the second end of the transformer and the first end of the first inductance respectively. Connect the first end of the inverter/rectifier bridge;

a capacitor unit; the first end of the capacitor unit is connected with the second end of the first inductor, and the second end is used for connecting with the second end of the inverter/rectifier bridge;

The capacitance value of the capacitance unit is adjustable, and is used to generate the required resonant capacitance value when working in the forward direction, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the first interval into the second interval When the voltage is reversed, the resonant capacitance value is adjusted, so that the circuit parameters of the LLC resonant circuit are changed, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the second interval into The voltage of the first interval is output.

Optionally, the capacitor unit includes: N capacitors connected in parallel with each other; wherein, the value of N is a positive integer;

When the required resonant capacitance value is generated, the capacitor unit is specifically used to: turn on a required number of capacitors in the N capacitors; when the resonant capacitance value is adjusted, the capacitor unit is specifically used for: Used to: adjust the number of capacitors that are turned on in the N capacitors;

Or, when the required resonance capacitance value is generated, the capacitor unit is specifically configured to: turn on a required number of capacitors in the N capacitors, and turn on at least one capacitor that is turned on according to a preset frequency , and is turned on according to the required turn-on time in each cycle; when the resonant capacitance value is adjusted, the capacitor unit is specifically used to: adjust the turn-on time of the at least one capacitor in each cycle .

Optionally, if the value of N is 2; the capacitor unit includes: a first capacitor, a second capacitor, a first switch transistor and a second switch transistor;

The first end of the first capacitor is connected with the second end of the first inductor, and the second end is used for connecting with the second end of the inverter/rectifier bridge;

The first end of the second capacitor is connected to the second end of the first capacitor through the first switch transistor, and the second end is connected to the first end of the first capacitor through the second switch transistor;

When the required number of capacitors in the N capacitors are turned on, the capacitor unit is specifically configured to: turn on the first capacitor, and turn off the first switch transistor and the second switch by turning off the first switch transistor. The transistor disconnects the second capacitor; when adjusting the number of capacitors that are turned on in the N capacitors, the capacitor unit is specifically used to: turn on the first switch transistor and the second switch a transistor turns on the second capacitor;

Alternatively, when the required number of capacitors in the N capacitors are turned on, and at least one capacitor that is turned on is turned on according to a preset frequency, and is turned on according to the required on-time in each cycle, The capacitor unit is specifically configured to: turn on the first capacitor, turn on the first switch transistor and the second switch transistor according to a preset frequency, so that the second capacitor is turned on, and at each The first switch transistor and the second switch transistor are turned on according to the required phase angle of the first switch transistor and the second switch transistor within one cycle, so that the second capacitor conducts according to the required phase angle. The on-time is turned on; when adjusting the on-time of the at least one capacitor in each cycle, the capacitor unit is specifically used to: adjust the phase angle of the first switch transistor and the second switch transistor, to adjust the conduction time of the second capacitor in each cycle.

Optionally, if the value of N is 2; the capacitor unit includes: a first capacitor, a second capacitor, a first switch transistor and a second switch transistor;

The first end of the first capacitor is connected with the second end of the first inductor, and the second end is used for connecting with the second end of the inverter/rectifier bridge;

The first end of the second capacitor is connected to the first end of the first capacitor, the second end is used to connect to the third end of the inverter/rectifier bridge through the first switch transistor, and the second switch the transistor is connected to the fourth end of the inverter/rectifier bridge;

When the required number of capacitors in the N capacitors are turned on, the capacitor unit is specifically configured to: turn on the first capacitor, and turn off the first switch transistor and the second switch by turning off the first switch transistor. The transistor disconnects the second capacitor; when adjusting the number of capacitors that are turned on in the N capacitors, the capacitor unit is specifically used to: turn on the first switch transistor and the second switch a transistor turns on the second capacitor;

Alternatively, when the required number of capacitors in the N capacitors are turned on, and at least one capacitor that is turned on is turned on according to a preset frequency, and is turned on according to the required on-time in each cycle, The capacitor unit is specifically configured to: turn on the first capacitor, turn on the first switch transistor and the second switch transistor according to a preset frequency, so that the second capacitor is turned on, and at each The first switch transistor and the second switch transistor are turned on according to the required phase angle of the first switch transistor and the second switch transistor within one cycle, so that the second capacitor conducts according to the required phase angle. The on-time is turned on; when adjusting the on-time of the at least one capacitor in each cycle, the capacitor unit is specifically used to: adjust the phase angle of the first switch transistor and the second switch transistor, to adjust the conduction time of the second capacitor in each cycle.

Optionally, the capacitor unit includes: a first capacitor, a first switch transistor and a second switch transistor;

The first end of the first capacitor is connected to the second end of the first inductor, and the second end is used to connect with the second end of the inverter/rectifier bridge; the second end of the first capacitor is also connecting the first end of the first capacitor through the first switch transistor and the second switch transistor in sequence;

When the required resonant capacitance value is generated, the capacitance unit is specifically configured to: turn on the first switch transistor and the second switch transistor according to a preset frequency, and perform the required resonant capacitance in each cycle. The turn-on time is turned on; when the resonant capacitance value is adjusted, the capacitor unit is specifically used for: adjusting the turn-on time of the first switch transistor and the second switch transistor in each cycle.

A control method for an LLC resonant circuit, wherein the LLC resonant circuit is the LLC resonant circuit as described in any one of the above; the control method comprises:

When working in the forward direction, the capacitor unit generates the required resonant capacitance value, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the first interval into the voltage of the second interval and outputs it;

During reverse operation, the capacitor unit adjusts the resonant capacitance value, so that the circuit parameters of the bidirectional SCC type LLC resonant circuit are changed so that the bidirectional SCC type LLC resonant converter will input the voltage in the second interval Converted to the voltage of the first interval and output.

Optionally, if the capacitor unit includes N capacitors connected in parallel:

The capacitor unit generates a required resonant capacitance value, including: turning on a required number of capacitors in the N capacitors; and adjusting the resonant capacitance value by the capacitor unit includes: adjusting the N capacitors The number of capacitors that are turned on;

Alternatively, the capacitor unit generates a required resonant capacitance value, including: turning on a required number of capacitors in the N capacitors, conducting at least one capacitor that is turned on according to a preset frequency, and turning on at least one capacitor in each cycle The capacitor unit is turned on according to the required turn-on time; adjusting the resonant capacitance value by the capacitor unit includes: adjusting the turn-on time of the at least one capacitor in each cycle.

Optionally, if the capacitor unit includes: a first capacitor, a second capacitor, a first switch transistor and a second switch transistor:

The turning on a required number of capacitors in the N capacitors includes: turning on the first capacitor, and turning off the second capacitor by turning off the first switch transistor and the second switch transistor ; the adjusting the number of capacitors that are turned on in the N capacitors includes: turning on the first switch transistor and the second switch transistor to make the second capacitor;

Alternatively, turning on a required number of capacitors in the N capacitors, for at least one capacitor that is turned on, is turned on according to a preset frequency, and is turned on according to the required on-time in each cycle, including: Turn on the first capacitor, turn on the first switch transistor and the second switch transistor according to a preset frequency, so that the second capacitor is turned on, and in each cycle, according to the required The phase angle of the first switch transistor and the second switch transistor turns on the first switch transistor and the second switch transistor, so that the second capacitor is turned on according to the required conduction time; The conduction time of the at least one capacitor in each cycle includes: adjusting the phase angle of the first switch transistor and the second switch transistor to adjust the conduction time of the second capacitor in each cycle.

Optionally, if the capacitor unit includes: a first capacitor, a first switch transistor and a second switch transistor, the capacitor unit generates a required resonance capacitance value, including: turning on the first switch according to a preset frequency transistor and the second switch transistor, and are turned on according to the required turn-on time in each cycle; the capacitance unit adjusts the resonant capacitance value, including: adjusting the first switch transistor and the second switch transistor in each cycle the turn-on time of the second switch transistor.

A bidirectional SCC type LLC resonant converter, comprising an inverter/rectifier bridge, a transformer, a rectifier/inverter bridge and an LLC resonant circuit; wherein the LLC resonant circuit is the LLC resonant circuit as described in any of the above; The LLC resonant circuit is respectively connected with the inverter/rectifier bridge and the transformer; the transformer is also connected with the rectifier/inverter bridge.

The application adopts the above technical solutions, and has the following beneficial effects:

The LLC resonant circuit provided by the solution of the present application includes a basic first inductor, a second inductor and a capacitor unit, wherein the capacitance value of the capacitor unit is adjustable. Based on this, it is applied to a bidirectional SCC type LLC resonant converter. When working in the forward direction, the capacitor unit can generate the resonant capacitance value required at this time to meet the needs of wide voltage input and output. ratio, the internal circuit parameters of the LLC resonant circuit can be changed, that is, the capacitance value of the capacitor unit can be changed, thereby changing the characteristics of the circuit, such as its resonance point, quality factor, gain and other parameters, so that the gain of the input and output of the reverse working circuit is ideal. A large change can be achieved within the frequency band of , and finally an ideal output can be obtained, thereby improving the output quality of the bidirectional SCC type LLC resonant converter in bidirectional flow.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

FIG. 1 is a structural diagram of an LLC resonant circuit provided by an embodiment of the present application.

FIG. 2 is a graph showing the relationship between frequency and gain of a conventional LLC resonant circuit provided by an embodiment of the present application.

FIG. 3 is a schematic diagram of an LLC resonant circuit provided by an embodiment of the present application.

FIG. 4 is a schematic diagram of a waveform of a capacitor unit provided by an embodiment of the present application.

FIG. 5 is a schematic diagram of a first working mode of a capacitor unit provided by an embodiment of the present application.

FIG. 6 is a schematic diagram of a second working mode of the capacitor unit provided by an embodiment of the present application.

FIG. 7 is a schematic diagram of a third working mode of a capacitor unit provided by an embodiment of the present application.

FIG. 8 is a schematic diagram of an LLC resonant circuit provided by another embodiment of the present application.

FIG. 9 is a schematic diagram of an LLC resonant circuit provided by another embodiment of the present application.

FIG. 10 is a flowchart of a method for controlling an LLC resonant circuit provided by an embodiment of the present application.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the examples in this application, all other implementations obtained by those of ordinary skill in the art without creative work fall within the scope of protection of this application.

Example

Referring to FIG. 1 , FIG. 1 is a structural diagram of an LLC resonant circuit provided by an embodiment of the present application.

As shown in FIG. 1 , this embodiment provides an LLC resonant circuit, which is applied to a bidirectionally controllable switched capacitor (switch-controlled capator, SCC) type LLC resonant converter, where the LLC resonant converter at least includes an inverter/rectifier bridge 1 , transformer 2 and rectifier/inverter bridge 3, LLC resonant circuit 4 is used to connect with inverter/rectifier bridge 1 and transformer 2 respectively, and transformer 2 is also connected with rectifier/inverter bridge 3; LLC resonant circuit 4 includes:

the first inductor L1;

The second inductance L2; the first end of the second inductance L2 is connected to the first end of the transformer 2 and the first end of the first inductance L1 respectively, and the second end is used to connect with the second end of the transformer 2 and the inverter/rectifier respectively The first end of bridge 1 is connected;

Capacitor unit 41; the first end of the capacitor unit 41 is connected to the second end of the first inductor L1, and the second end is used to connect with the second end of the inverter/rectifier bridge 1;

The capacitance value of the capacitor unit 41 is adjustable, and is used to generate the required resonant capacitance value when working in the forward direction, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the first interval into the voltage of the second interval and Output; when working in reverse, adjust the resonant capacitance value so that the circuit parameters of the LLC resonant circuit 4 are changed so that the bidirectional SCC type LLC resonant converter converts the input voltage of the second interval into the voltage of the first interval and outputs it.

Taking the input on the left side and the output on the right side as an example in the forward direction in Figure 1, the basic working principle of the bidirectional SCC type LLC resonant converter includes: when working in the forward direction, the inverter/rectifier bridge 1 inverts the input DC power V1 and outputs the AC power, The LLC resonant circuit 4 performs resonance conversion on the AC power output by the inverter/rectifier bridge 1, the transformer 2 performs voltage conversion on the AC power after the resonance conversion by the LLC resonant circuit 4, and the rectifier/inverter bridge 3 performs voltage conversion on the AC power output by the transformer 2. Rectify and output V2. When working in reverse, the rectifier/inverter bridge 3 inverts the input DC power V2 and outputs the AC power, the transformer 2 performs voltage conversion on the AC power output by the rectifier/inverter bridge 3, and the LLC resonant circuit 4 converts the output voltage of the transformer 2 after voltage conversion. The AC power is resonantly transformed, and the inverter/rectifier bridge 1 rectifies the AC power output after the resonance transformation of the LLC resonant circuit 4 and outputs the DC power V1.

Among them, the capacitance value of the capacitor unit 41 can be changed. When the resonant capacitance value generated by the capacitor unit 41 changes, it will have the following effects on the characteristics of the LLC resonant circuit 4: First, the frequency of the resonance point changes, and the resonant capacitance value changes. Large, the frequency of the resonance point decreases, the value of the resonance capacitance decreases, and the frequency of the resonance point increases; the second is the change of the quality factor Q: the value of the resonance capacitance increases, the quality factor decreases, the value of the resonance capacitance decreases, and the quality factor increases; The third is the change of gain: the smaller the quality factor, the higher the maximum gain, on the contrary, the larger the quality factor, the smaller the maximum gain point.

The resonant capacitance value is the equivalent capacitance value of the capacitor unit 41 connected to the LLC resonant circuit 4 .

In this embodiment, the input and output voltage is a wide voltage, and the wide voltage is relative to a single voltage value. The specific values of the first interval and the second interval corresponding to the voltage can be set according to actual needs.

The LLC resonant circuit 4 provided by the solution of the present application includes a basic first inductance L1, a second inductance L2 and a capacitance unit 41, wherein the capacitance value of the capacitance unit 41 can be changed. Based on this, it is applied to a bidirectional SCC type In the LLC resonant converter, in the forward operation, the capacitor unit 41 can generate the resonant capacitance value required at this time to meet the needs of wide voltage input and output, and in the reverse operation, when the input and output conditions cannot meet the target requirements , compared with the above-mentioned related technologies, the internal circuit parameters of the LLC resonant circuit 4 can be changed, that is, the capacitance value of the capacitor unit 41 can be changed, thereby changing the characteristics of the circuit, such as its resonance point, quality factor, gain and other parameters, so that the reverse operation The gain of the input and output of the circuit can be greatly changed in the ideal frequency band, and finally the ideal output is obtained, thereby improving the output quality of the bidirectional SCC type LLC resonant converter in bidirectional flow.

It should be noted that the capacitor unit can also generate the required resonant capacitance value based on the input on the right side of Figure 1 when the output on the left side works in the forward direction, and the input on the left side and the output on the right side work in the reverse direction to adjust the resonant capacitor value, that is, In both directions, an ideal output can be obtained by adjusting the capacitance value of the capacitor unit, realizing bidirectional adjustment.

In addition, based on the LLC resonant circuit 4 of the present application, by adjusting the capacitance value of the capacitor unit 41, the change requirements of different resonance points can be met, so that the LLC resonant circuit 4 can basically work around the resonance point, thereby achieving gain optimization.

In addition, in the traditional LLC resonant circuit, there are generally two resonant frequencies, one of which is the resonant frequency f _r1 , which is obtained based on the resonant inductance L _r and the resonant capacitor _Cr , see the following formula (1), the other resonant frequency f _r2 is obtained based on the resonant inductance L _r , the excitation inductance L _m , and the resonant capacitor C _r , see the following formula (2).

As shown in Figure 2, the abscissa is the frequency, and the ordinate is the gain. When the quality factors are 3, 2, 1, 0.5, 0.25, and 0.2, the frequency and gain of the LLC resonant circuit have a curve as shown in Figure 2 In order to realize the soft switching of the circuit, the general operating frequency is set near f _r1 . The operating frequency of the resonant circuit is generally not selected to the left of the low resonance point, but to the left of the resonance point with a higher frequency value, thereby realizing ZVS. However, when the input changes, in order to achieve the ideal output, the frequency may be over-adjusted, so that the operating frequency operates on the left side of the lower resonance point. Therefore, the entire circuit works in a capacitive state, which is difficult to achieve. The advantages of the ZVS, LLC resonant circuit 4 are not reflected. In the solution of the present application, the working frequency can be shifted to the left. Correspondingly, the value of the resonance capacitor is increased, so as to realize the left shift of the resonance point, and finally ensure that the working frequency is on the right side of the low resonance point. Advantages of LLC resonant circuit 4.

During specific implementation, there are various specific structures of the capacitor unit 41 . Several possible structures are listed but not limited below.

In implementation, the capacitor unit 41 may include one capacitor or multiple capacitors. If multiple capacitors are included, the multiple capacitors may be connected in parallel with each other, or may be connected in series with each other. Different structures have corresponding strategies for realizing the adjustment of the resonant capacitance value. An example is given below.

In some embodiments, the specific structure of the capacitor unit 41 includes: N capacitors connected in parallel with each other; wherein, N is a positive integer. This embodiment provides a structure of parallel capacitors. According to the characteristics of parallel capacitors, the equivalent capacitance value is the sum of the capacitance values of the capacitors connected in parallel. The more capacitors connected in parallel, the greater the equivalent capacitance value. The more the capacitors are, the smaller the equivalent capacitance value is. Compared with the structure of the series capacitor, the parallel capacitor structure of this embodiment does not cause waste of the equivalent capacitance.

Based on this structure, there are various strategies for realizing the adjustable resonant capacitance value.

The first one is: when the required resonant capacitance value is generated, the capacitor unit 41 is specifically used for: turning on the required number of capacitors in the N capacitors; when adjusting the resonant capacitance value, the capacitor unit 41 is specifically used for: adjusting the N capacitors The number of capacitors that are turned on in each capacitor. In this embodiment, the adjustment of the resonant capacitance value is realized by adjusting the number of on-capacitors, and the realization is very simple.

The second is: when the required resonant capacitance value is generated, the capacitor unit 41 is specifically used to: turn on a required number of capacitors among the N capacitors, and turn on at least one capacitor that is turned on according to a preset frequency, and Turn on according to the required turn-on time in each cycle; when adjusting the resonant capacitance value, the capacitor unit 41 is specifically used to: adjust the turn-on time of at least one capacitor in each cycle. Among them, the size of the preset frequency can be set according to actual needs, for example, it can be set to be consistent with the operating frequency of the LLC resonant circuit 4, for example, it can be set to the operating frequency of the previous stage circuit, so that it can be controlled together with the previous stage circuit, The implementation is simple, and it can also be set to other values that are inconsistent with the operating frequency of the previous stage circuit, which will not be listed here. The solution in this embodiment can also be called a high-frequency control strategy. By adjusting the on-time of the capacitor in each cycle and changing the equivalent capacitance value, the resonance point can be continuously adjusted.

In implementation, the number N of capacitors connected in parallel in the capacitor unit 41 is not specifically limited, and can be set according to actual needs. The following takes the value of N as 2 as an example to introduce a specific structure of the capacitor unit 41 .

Referring to FIG. 3 , FIG. 3 is a structural diagram of an LLC resonant circuit 4 provided by another embodiment of the present application.

As shown in FIG. 3 , the capacitor unit 41 includes: a first capacitor C1, a second capacitor C2, a first switch transistor T1 and a second switch transistor T2; a first end of the first capacitor C1 and a second end of the first inductor L1 The second end is connected to the second end of the inverter/rectifier bridge 1; the first end of the second capacitor C2 is connected to the second end of the first capacitor C1 through the first switching transistor T1, and the second end is connected to the second end of the first capacitor C1 through the first switching transistor T1. The two switching transistors T2 are connected to the first end of the first capacitor C1.

Wherein, the directions of the first switch transistor T1 and the second switch transistor T2 are opposite. Specifically, as shown in FIG. 3 , the first terminal of the second capacitor C2 is connected to the drain of the first switching transistor T1 , and the second terminal is connected to the drain of the second switching transistor T2 . The source of the first switching transistor T1 is connected to the second terminal of the first capacitor C1. The source of the second switching transistor T2 is connected to the first terminal of the first capacitor C1.

Based on the structure shown in FIG. 3 , correspondingly, if the above-mentioned first strategy is adopted, when the required number of capacitors among the N capacitors are turned on, the capacitor unit 41 is specifically used for: turning on the first capacitor C1 , and turning on the first capacitor C1 by turning off Turn on the first switch transistor T1 and the second switch transistor T2 to disconnect the second capacitor C2; when adjusting the number of capacitors that are turned on in the N capacitors, the capacitor unit 41 is specifically used to: turn on the first switch transistor T1 and the second capacitor C2. Two switch transistors T2, so that the second capacitor C2 is turned on. In this embodiment, the switching of on and off of the switching transistor occurs only when the working direction is changed, and the control method thereof is simple and convenient. When working in the forward direction, in the LLC state, the first switching transistor T1 and the second switching transistor T2 are both in the off state, the second capacitor C2 does not participate in the resonance, and the resonance capacitor value is the capacitance value of the first capacitor C1 at this moment. , the frequency of the resonance point is the largest, and the working frequency can be changed around the resonance point to realize the ZVS working state. When working in reverse, it can also work in a resonant state. Both the first switching transistor T1 and the second switching transistor T2 are in a conducting state, and the second capacitor C2 participates in the resonance. At this moment, the resonant capacitor value is the capacitance of the first capacitor C1. The sum of the capacitance value and the capacitance value of the second capacitor C2, the resonant frequency is the lowest. By increasing the resonant capacitance value, the frequency of the resonant point is greatly reduced relative to the original resonant point, so that the operating frequency can be at the forward operating frequency. Nearby adjustment can achieve a small range of frequency changes during bidirectional operation. In this way, by slightly changing the operating frequency, the voltage requirements can be met and the circuit topology performance can be optimized.

Based on the structure shown in FIG. 3 , correspondingly, if the above-mentioned second strategy is adopted, a required number of capacitors among the N capacitors are turned on, and at least one capacitor that is turned on is turned on according to the preset frequency, and each capacitor is turned on at a predetermined frequency. When the capacitor unit 41 is turned on according to the required turn-on time in the cycle, the capacitor unit 41 is specifically used for: turning on the first switching transistor T1 and the second switching transistor T2 according to the preset frequency, so that the second capacitor C2 is turned on, and the second capacitor C2 is turned on. In each cycle, the first switching transistor T1 and the second switching transistor T2 are turned on according to the required phase angle of the first switching transistor T1 and the second switching transistor T2, so that the second capacitor C2 is turned on according to the required on-time. ; When adjusting the conduction time of at least one capacitor in each cycle, the capacitor unit 41 is specifically used to: adjust the phase angle of the first switching transistor T1 and the second switching transistor T2 to adjust the second capacitor C2 in each cycle. turn-on time. The specific working principle is as follows:

Referring to FIG. 4 , FIG. 4 is a schematic diagram of a waveform of the capacitor unit 41 provided by an embodiment of the present application.

Referring to FIG. 5 , FIG. 5 is a schematic diagram of a first working mode of the capacitor unit 41 provided by an embodiment of the present application.

Referring to FIG. 6 , FIG. 6 is a schematic diagram of a second working mode of the capacitor unit 41 provided by an embodiment of the present application.

Referring to FIG. 7 , FIG. 7 is a schematic diagram of a third working mode of the capacitor unit 41 provided by an embodiment of the present application.

Based on FIG. 4 , a sinusoidal voltage is applied to both ends of the first capacitor C1 for a period T of analysis. When the voltage is in the positive half cycle, the second switching transistor T2 is kept on to keep the current flowing forward. As shown in FIG. 5 , the current forms a path through the body diode of the first switching transistor T1, the second capacitor C2, and the second switching transistor T2. The second capacitor C2 is charged, and when the time conduction angle reaches αT/2π, the second switching transistor T2 is controlled to be turned off, as shown in FIG. 6 . Then at the phase (π-α)T/2, the first switching transistor T1 is controlled to be turned on (the first switching transistor T1 can realize soft switching), as shown in FIG. 7 , the current flow direction is the direction of the second switching transistor T2 The body diode, the second capacitor C2 and the first switching transistor T1 discharge the charges stored in the previous stage at both ends of the second capacitor C2. The first switching transistor T1 is controlled to be continuously turned on until the sinusoidal voltage across the first capacitor C1 is at (π+α)T/2, and the first switching transistor T1 is controlled to be effectively turned off. When the sinusoidal voltage across the first capacitor C1 operates at (2π-α)T/2, the second switching transistor T2 is controlled to be turned on (at this time, the second switching transistor T2 can implement soft switching). Then, according to the above-mentioned one-cycle switch coordination mode, the equivalent change of the capacitance value is realized by repeated charging and discharging in the circuit. The value range of the phase shift angle α may be 0 to 90 degrees.

When a higher resonance point frequency is required, the phase angle of the first switching transistor T1 and the second switching transistor T2 can be made lower, resulting in a decrease in the equivalent capacitance value and an increase in the resonance point frequency; on the contrary, if a lower frequency is required When the resonant point frequency is , the phase angle of the first switching transistor T1 and the second switching transistor T2 should be raised to increase the equivalent capacitance value and reduce the frequency of the resonant point.

In a cycle, the ratio of the time the switching transistor is turned on relative to the total time of a cycle is called the duty cycle. The solution of this embodiment can also be said to adjust the equivalent capacitance value by adjusting the duty ratio.

Referring to FIG. 8, FIG. 8 is a structural diagram of an LLC resonant circuit provided by another embodiment of the present application.

As shown in FIG. 8 , the specific structure of the capacitor unit 41 includes: a first capacitor C1, a second capacitor C2, a first switch transistor T1 and a second switch transistor T2; the first end of the first capacitor C1 and the first inductance L1 The second end is connected to the second end of the inverter/rectifier bridge 1; the first end of the second capacitor C2 is connected to the first end of the first capacitor C1, and the second end is used to pass the The source and drain of a switching transistor T1 are connected to the third terminal of the inverter/rectifier bridge 1 , and the drain and source of the second switching transistor T2 are sequentially connected to the fourth terminal of the inverter/rectifier bridge 1 . In this embodiment, compared with the structure shown in FIG. 3 , the positions of the first switching transistor T1 and the second switching transistor T2 are changed, and the first switching transistor T1 and the second switching transistor T2 connected in series are connected in parallel to the positive To the inverter/rectifier bridge 1 of the input front stage. In this way, in implementation, the first switching transistor T1 and the second switching transistor T2 can share a driving auxiliary circuit with the switching transistor in the inverter/rectifier bridge 1 , which is simple and convenient to implement, and saves cost and space.

Based on the structure shown in FIG. 8 , correspondingly, if the above-mentioned first strategy is adopted, when the required number of capacitors among the N capacitors are turned on, the capacitor unit 41 is specifically used for: turning on the first capacitor C1 , and turning on the first capacitor C1 by turning off Turn on the first switch transistor T1 and the second switch transistor T2 to disconnect the second capacitor C2; when adjusting the number of capacitors that are turned on in the N capacitors, the capacitor unit 41 is specifically used to: turn on the first switch transistor T1 and the second capacitor C2. The two switching transistors T2 make the second capacitor C2 conduct. For details, reference may be made to the related embodiment in FIG. 3 , which will not be repeated here.

Based on the structure shown in FIG. 8 , correspondingly, if the above-mentioned second strategy is adopted, a required number of capacitors among the N capacitors are turned on, and at least one capacitor that is turned on is turned on according to the preset frequency, and each capacitor is turned on at a predetermined frequency. When the capacitor unit 41 is turned on according to the required turn-on time in the cycle, the capacitor unit 41 is specifically used for: turning on the first capacitor C1, and turning on the first switching transistor T1 and the second switching transistor T2 according to the preset frequency, so that the second switching transistor T1 is turned on. The capacitor C2 is turned on, and in each cycle, the first switch transistor T1 and the second switch transistor T2 are turned on according to the required phase angle of the first switch transistor T1 and the second switch transistor T2, so that the second capacitor C2 is in accordance with the required phase angle. The required on-time is turned on; when adjusting the on-time of at least one capacitor in each cycle, the capacitor unit 41 is specifically used to: adjust the phase angle of the first switching transistor T1 and the second switching transistor T2 to adjust each The conduction time of the second capacitor C2 in a period. For details, reference may be made to the related embodiment in FIG. 3 , which will not be repeated here.

Referring to FIG. 9, FIG. 9 is a structural diagram of an LLC resonant circuit 4 provided by another embodiment of the present application.

In some embodiments, as shown in FIG. 9 , the capacitor unit 41 includes: a first capacitor C1, a first switch transistor T1 and a second switch transistor T2; a first end of the first capacitor C1 and a second end of the first inductor L1 The second end is used to connect with the second end of the inverter/rectifier bridge 1; the second end of the first capacitor C1 is also connected to the first end of the first capacitor C1 through the first switch transistor T1 and the second switch transistor T2 in turn. end. The first terminal of the first capacitor C1 is connected to the source of the second switching transistor T2, and the second terminal is connected to the source of the first switching transistor T1. The drain of the first switching transistor T1 is connected to the drain of the second switching transistor T2.

Based on the structure shown in FIG. 9 , when the required resonant capacitance value is generated, the capacitor unit 41 is specifically used for: turning on the first switching transistor T1 and the second switching transistor T2 according to the preset frequency, and in each cycle according to The required turn-on time is turned on; when adjusting the resonant capacitance value, the capacitor unit 41 is specifically used to: adjust the turn-on time of the first switch transistor T1 and the second switch transistor T2 in each cycle. In this embodiment, compared with the structure in FIG. 3 , the second capacitor C2 is removed, thus reducing the number of capacitors, realizing the miniaturization of the volume and the high production efficiency. For a specific implementation, reference may be made to the related embodiment in FIG. 3 , which will not be repeated here.

There are various types of the first switching transistor T1, for example, it may include a metal oxide semiconductor field effect transistor (MOS) or an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT). There are also various types of the second switching transistor T2, such as MOS or IGBT.

The above inverter/rectifier bridge 1 may be a full-bridge circuit or a half-bridge circuit. In FIG. 3, FIG. 4, FIG. 8, and FIG. 9, a full-bridge circuit is used for illustration. Specifically, the inverter/rectifier bridge 1 includes: a third switch transistor T3, a fourth switch transistor T4, a fifth switch transistor T5 and a sixth switch transistor T6. The first end of the inverter/rectifier bridge 1 is respectively connected to the source of the fifth switching transistor T5 and the drain of the sixth switching transistor T6, and the second end is respectively connected to the source of the third switching transistor T3 and the fourth switching transistor T4 The drain of the third switch transistor T3 and the drain of the fifth switch transistor T5 are respectively connected, and the fourth terminal is respectively connected to the source of the fourth switch transistor T4 and the source of the sixth switch transistor T6 pole connection.

When working in the forward direction, the third end and the fourth end of the inverter/rectifier bridge 1 may be the input end, and the first end and the second end may be the output end. In reverse operation, the first end and the second end of the inverter/rectifier bridge 1 may be the input end, and the third end and the fourth end may be the output end.

The above-mentioned rectifier/inverter bridge 3 may be a full-bridge circuit or a half-bridge circuit. In FIG. 3, FIG. 4, FIG. 8, and FIG. 9, a full-bridge circuit is used for illustration. Specifically, the rectifier/inverter bridge 3 includes: a seventh switch transistor T7, an eighth switch transistor T8, a ninth switch transistor T9 and a tenth switch transistor T10. The first end of the rectifier/inverter bridge 3 is respectively connected to the source of the ninth switch transistor T9, the drain of the tenth switch transistor T10, and the third end of the transformer 2, and the second end is respectively connected to the source of the seventh switch transistor T7 pole, the drain of the eighth switching transistor T8, and the fourth terminal of the transformer 2; the third terminal is respectively connected to the drain of the seventh switching transistor T7 and the drain of the ninth switching transistor T9; The source of the switching transistor T8 and the source of the tenth switching transistor T10 are connected.

When working in the forward direction, the first end and the second end of the rectifier/inverter bridge 3 may be the input end, and the third end and the fourth end may be the output end. When working in reverse, the third and fourth ends of the rectifier/inverter bridge 3 may be input ends, and the first and second ends may be output ends.

As shown in FIGS. 3 , 4 , 8 and 9 , the transformer 2 includes a first winding and a second winding. One end of the first winding serves as the first end of the transformer 2 and the other end serves as the second end of the transformer 2 ; one end of the second winding serves as the third end of the transformer 2 , and the other end serves as the fourth end of the transformer 2 .

In FIG. 3 , FIG. 4 , FIG. 8 , and FIG. 9 , the bidirectional SCC type LLC resonant converter may further include a first filtering unit 5 . One end of the first filtering unit 5 is connected to the third end of the inverter/rectifier bridge 1 , and the other end is connected to the fourth end of the inverter/rectifier bridge 1 . Specifically, the specific structure of the first filtering unit includes a third capacitor C3. The bidirectional SCC type LLC resonant converter may further include a second filtering unit 6 . One end of the second filter unit 6 is connected to the third end of the rectifier/inverter bridge 3 , and the other end is connected to the fourth end of the rectifier/inverter bridge 3 . Specifically, the specific structure of the second filtering unit includes a fourth capacitor C4. The input and output waveforms can be filtered through the first filtering unit and the second filtering unit to improve the current quality.

Referring to FIG. 10 , FIG. 10 is a flowchart of a method for controlling an LLC resonant circuit provided by another embodiment of the present application.

As shown in FIG. 10 , this embodiment provides a method for controlling an LLC resonant circuit, where the LLC resonant circuit is the LLC resonant circuit described in any of the above embodiments; the control method in this embodiment at least includes the following steps:

Step 101 : when working in the forward direction, the capacitor unit generates the required resonant capacitance value, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the first interval into the voltage of the second interval and outputs it.

Step 102: During reverse operation, the capacitor unit adjusts the resonant capacitance value, so that the circuit parameters of the LLC resonant circuit are changed, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the second interval into the voltage of the first interval and output.

The LLC resonant circuit provided by the solution of the present application includes a basic first inductor, a second inductor and a capacitor unit, wherein the capacitance value of the capacitor unit is adjustable. Based on this, it is applied to a bidirectional SCC type LLC resonant converter. When working in the forward direction, the capacitor unit can generate the resonant capacitance value required at this time to meet the needs of wide voltage input and output. When working in reverse, when the input and output conditions cannot meet the target requirements, the existing Compared with other technologies, the internal circuit parameters of the LLC resonant circuit can be changed, that is, the capacitance value of the capacitor unit can be changed, thereby changing the characteristics of the circuit, such as its resonance point, quality factor, gain and other parameters, so that the gain of the input and output of the reverse working circuit can be changed A large change can be achieved in the ideal frequency band, and finally an ideal output can be obtained, thereby improving the output quality of the bidirectional SCC type LLC resonant converter in bidirectional flow.

Optionally, if the capacitor unit includes N capacitors connected in parallel:

The capacitor unit generates a required resonant capacitance value, including: turning on a required number of capacitors in the N capacitors; the capacitor unit adjusting the resonant capacitor value includes: adjusting the number of capacitors that are turned on in the N capacitors;

Alternatively, the capacitor unit generates a required resonant capacitance value, including: turning on a required number of capacitors among the N capacitors, conducting at least one capacitor that is turned on according to a preset frequency, and conducting according to the required frequency in each cycle The turn-on time is turned on; the capacitor unit adjusts the resonant capacitance value, including: adjusting the turn-on time of at least one capacitor in each cycle.

Optionally, if the capacitor unit includes: a first capacitor, a second capacitor, a first switch transistor and a second switch transistor:

Turning on the required number of capacitors in the N capacitors includes: turning on the first capacitor, and disconnecting the second capacitor by disconnecting the first switch transistor and the second switch transistor; adjusting the number of capacitors that are turned on in the N capacitors , including: turning on the second capacitor by turning on the first switch transistor and the second switch transistor;

Alternatively, a required number of capacitors in the N capacitors are turned on, and at least one capacitor that is turned on is turned on according to a preset frequency, and turned on according to the required on-time in each cycle, including: turning on the first capacitor A capacitor turns on the first switching transistor and the second switching transistor according to the preset frequency, so that the second capacitor is turned on, and conducts according to the required phase angle of the first switching transistor and the second switching transistor in each cycle Turning on the first switch transistor and the second switch transistor, so that the second capacitor is turned on according to the required turn-on time; adjusting the turn-on time of at least one capacitor in each cycle includes: adjusting the first switch transistor and the second switch transistor , to adjust the conduction time of the second capacitor in each cycle.

Optionally, if the capacitor unit includes: a first capacitor, a first switch transistor and a second switch transistor, the capacitor unit generates a required resonance capacitance value, including: turning on the first switch transistor and the second switch transistor according to a preset frequency , and is turned on according to the required turn-on time in each cycle; the capacitor unit adjusts the resonant capacitance value, including: adjusting the turn-on time of the first switch transistor and the second switch transistor in each cycle.

It should be noted that the capacitor unit in this embodiment can be triggered by an external circuit to generate a required resonant capacitance value, and the specific structure of the external circuit may include a controller or other hardware circuits, and so on.

For the specific implementation of the embodiments of the present application, reference may be made to the implementation of the LLC resonant circuit in any of the above embodiments, which will not be repeated here.

Another embodiment of the present application further provides a bidirectional SCC type LLC resonant converter, including an inverter/rectifier bridge, a transformer, a rectifier/inverter bridge and an LLC resonant circuit; wherein the LLC resonant circuit is as described in any of the above embodiments The LLC resonant circuit described above; the LLC resonant circuit is respectively connected with the inverter/rectifier bridge and the transformer; the transformer is also connected with the rectifier/inverter bridge.

For the specific implementation of the bidirectional SCC type LLC resonant converter provided in the embodiment of the present application, reference may be made to the implementation of the LLC resonant circuit in any of the above embodiments, and details are not repeated here.

It can be understood that, the same or similar parts in the above embodiments may refer to each other, and the content not described in detail in some embodiments may refer to the same or similar content in other embodiments.

It should be noted that, in the description of the present application, the terms "first", "second" and the like are only used for the purpose of description, and should not be construed as indicating or implying relative importance. Also, in the description of this application, unless otherwise specified, the meaning of "plurality" means at least two.

Any description of a process or method in the flowcharts or otherwise described herein may be understood to represent a module, segment or portion of code comprising one or more executable instructions for implementing a specified logical function or step of the process , and the scope of the preferred embodiments of the present application includes alternative implementations in which the functions may be performed out of the order shown or discussed, including performing the functions substantially concurrently or in the reverse order depending upon the functions involved, which should It is understood by those skilled in the art to which the embodiments of the present application belong.

It should be understood that various parts of this application may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or a combination of the following techniques known in the art: Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, Programmable Gate Arrays (PGA), Field Programmable Gate Arrays (FPGA), etc.

Those of ordinary skill in the art can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, and the program is stored in a computer-readable storage medium. When executed, one or a combination of the steps of the method embodiment is included.

In addition, each functional unit in each embodiment of the present application may be integrated into one processing module, or each unit may exist physically alone, or two or more units may be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware, and can also be implemented in the form of software function modules. If the integrated modules are implemented in the form of software functional modules and sold or used as independent products, they may also be stored in a computer-readable storage medium.

The above-mentioned storage medium may be a read-only memory, a magnetic disk or an optical disk, and the like.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limitations to the present application. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (10)

1. an LLC resonant circuit, it is characterized in that, be applied in bidirectional SCC type LLC resonant converter, described LLC resonant converter at least comprises inverter/rectifier bridge, transformer and rectifier/inverter bridge, described LLC resonant circuit for connecting with the inverter/rectifier bridge and the transformer respectively, and the transformer is also connected with the rectifier/inverter bridge; the LLC resonant circuit includes: first inductance; A second inductance; the first end of the second inductance is respectively connected to the first end of the transformer and the first end of the first inductance, and the second end is used to connect to the second end of the transformer and the first end of the first inductance respectively. Connect the first end of the inverter/rectifier bridge; a capacitor unit; the first end of the capacitor unit is connected with the second end of the first inductor, and the second end is used for connecting with the second end of the inverter/rectifier bridge; The capacitance value of the capacitance unit is adjustable, and is used to generate the required resonant capacitance value when working in the forward direction, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the first interval into the second interval When the voltage is reversed, the resonant capacitance value is adjusted, so that the circuit parameters of the LLC resonant circuit are changed, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the second interval into The voltage of the first interval is output. 2. The LLC resonant circuit according to claim 1, wherein the capacitor unit comprises: N capacitors connected in parallel with each other; wherein, the value of N is a positive integer; When the required resonant capacitance value is generated, the capacitor unit is specifically used to: turn on a required number of capacitors in the N capacitors; when the resonant capacitance value is adjusted, the capacitor unit is specifically used for: Used to: adjust the number of capacitors that are turned on in the N capacitors; Or, when the required resonance capacitance value is generated, the capacitor unit is specifically configured to: turn on a required number of capacitors in the N capacitors, and turn on at least one capacitor that is turned on according to a preset frequency , and is turned on according to the required turn-on time in each cycle; when the resonant capacitance value is adjusted, the capacitor unit is specifically used to: adjust the turn-on time of the at least one capacitor in each cycle . 3. The LLC resonant circuit according to claim 2, wherein, if the value of N is 2; the capacitor unit comprises: a first capacitor, a second capacitor, a first switch transistor and a second switch transistor; The first end of the first capacitor is connected with the second end of the first inductor, and the second end is used for connecting with the second end of the inverter/rectifier bridge; The first end of the second capacitor is connected to the second end of the first capacitor through the first switch transistor, and the second end is connected to the first end of the first capacitor through the second switch transistor; When the required number of capacitors in the N capacitors are turned on, the capacitor unit is specifically configured to: turn on the first capacitor, and turn off the first switch transistor and the second switch by turning off the first switch transistor. The transistor disconnects the second capacitor; when adjusting the number of capacitors that are turned on in the N capacitors, the capacitor unit is specifically used to: turn on the first switch transistor and the second switch a transistor turns on the second capacitor; Alternatively, when the required number of capacitors in the N capacitors are turned on, and at least one capacitor that is turned on is turned on according to a preset frequency, and is turned on according to the required on-time in each cycle, The capacitor unit is specifically configured to: turn on the first capacitor, turn on the first switch transistor and the second switch transistor according to a preset frequency, so that the second capacitor is turned on, and at each The first switch transistor and the second switch transistor are turned on according to the required phase angle of the first switch transistor and the second switch transistor within one cycle, so that the second capacitor conducts according to the required phase angle. The on-time is turned on; when adjusting the on-time of the at least one capacitor in each cycle, the capacitor unit is specifically used to: adjust the phase angle of the first switch transistor and the second switch transistor, to adjust the conduction time of the second capacitor in each cycle. 4. The LLC resonant circuit according to claim 2, wherein, if the value of N is 2; the capacitor unit comprises: a first capacitor, a second capacitor, a first switch transistor and a second switch transistor; The first end of the first capacitor is connected with the second end of the first inductor, and the second end is used for connecting with the second end of the inverter/rectifier bridge; The first end of the second capacitor is connected to the first end of the first capacitor, the second end is used to connect to the third end of the inverter/rectifier bridge through the first switch transistor, and the second switch the transistor is connected to the fourth end of the inverter/rectifier bridge; When the required number of capacitors in the N capacitors are turned on, the capacitor unit is specifically configured to: turn on the first capacitor, and turn off the first switch transistor and the second switch by turning off the first switch transistor. The transistor disconnects the second capacitor; when adjusting the number of capacitors that are turned on in the N capacitors, the capacitor unit is specifically used to: turn on the first switch transistor and the second switch a transistor turns on the second capacitor; Alternatively, when the required number of capacitors in the N capacitors are turned on, and at least one capacitor that is turned on is turned on according to a preset frequency, and is turned on according to the required on-time in each cycle, The capacitor unit is specifically configured to: turn on the first capacitor, turn on the first switch transistor and the second switch transistor according to a preset frequency, so that the second capacitor is turned on, and at each The first switch transistor and the second switch transistor are turned on according to the required phase angle of the first switch transistor and the second switch transistor within one cycle, so that the second capacitor conducts according to the required phase angle. The on-time is turned on; when adjusting the on-time of the at least one capacitor in each cycle, the capacitor unit is specifically used to: adjust the phase angle of the first switch transistor and the second switch transistor, to adjust the conduction time of the second capacitor in each cycle. 5. The LLC resonant circuit according to claim 1, wherein the capacitor unit comprises: a first capacitor, a first switch transistor and a second switch transistor; The first end of the first capacitor is connected to the second end of the first inductor, and the second end is used to connect with the second end of the inverter/rectifier bridge; the second end of the first capacitor is also connecting the first end of the first capacitor through the first switch transistor and the second switch transistor in sequence; When the required resonant capacitance value is generated, the capacitance unit is specifically configured to: turn on the first switch transistor and the second switch transistor according to a preset frequency, and perform the required resonant capacitance in each cycle. The turn-on time is turned on; when the resonant capacitance value is adjusted, the capacitor unit is specifically used for: adjusting the turn-on time of the first switch transistor and the second switch transistor in each cycle. 6. A control method for an LLC resonant circuit, wherein the LLC resonant circuit is the LLC resonant circuit according to any one of claims 1 to 5; the control method comprises: When working in the forward direction, the capacitor unit generates the required resonant capacitance value, so that the bidirectional SCC type LLC resonant converter converts the input voltage of the first interval into the voltage of the second interval and outputs it; During reverse operation, the capacitor unit adjusts the resonant capacitance value, so that the circuit parameters of the bidirectional SCC type LLC resonant circuit are changed so that the bidirectional SCC type LLC resonant converter will input the voltage in the second interval Converted to the voltage of the first interval and output. 7. The control method according to claim 6, wherein, if the capacitor unit comprises N capacitors connected in parallel with each other: The capacitor unit generates a required resonant capacitance value, including: turning on a required number of capacitors in the N capacitors; and adjusting the resonant capacitance value by the capacitor unit includes: adjusting the N capacitors The number of capacitors that are turned on; Alternatively, the capacitor unit generates a required resonant capacitance value, including: turning on a required number of capacitors in the N capacitors, conducting at least one capacitor that is turned on according to a preset frequency, and turning on at least one capacitor in each cycle The capacitor unit is turned on according to the required turn-on time; adjusting the resonant capacitance value by the capacitor unit includes: adjusting the turn-on time of the at least one capacitor in each cycle. 8. The control method according to claim 7, wherein if the capacitor unit comprises: a first capacitor, a second capacitor, a first switch transistor and a second switch transistor: The turning on a required number of capacitors in the N capacitors includes: turning on the first capacitor, and turning off the second capacitor by turning off the first switch transistor and the second switch transistor ; the adjusting the number of capacitors that are turned on in the N capacitors includes: turning on the first switch transistor and the second switch transistor to make the second capacitor; Alternatively, turning on a required number of capacitors in the N capacitors, for at least one capacitor that is turned on, is turned on according to a preset frequency, and is turned on according to the required on-time in each cycle, including: Turn on the first capacitor, turn on the first switch transistor and the second switch transistor according to a preset frequency, so that the second capacitor is turned on, and in each cycle, according to the required The phase angle of the first switch transistor and the second switch transistor turns on the first switch transistor and the second switch transistor, so that the second capacitor is turned on according to the required conduction time; The conduction time of the at least one capacitor in each cycle includes: adjusting the phase angle of the first switch transistor and the second switch transistor to adjust the conduction time of the second capacitor in each cycle. 9 . The control method according to claim 6 , wherein, if the capacitor unit includes: a first capacitor, a first switch transistor and a second switch transistor, the capacitor unit generates a required resonance capacitance value, comprising: 10 . : turn on the first switch transistor and the second switch transistor according to a preset frequency, and turn on according to the required turn-on time in each cycle; the capacitor unit adjusts the resonant capacitance value, including: The on-time of the first switch transistor and the second switch transistor in each cycle is adjusted. 10. A bidirectional SCC type LLC resonant converter, characterized in that it comprises an inverter/rectifier bridge, a transformer, a rectifier/inverter bridge and an LLC resonant circuit; wherein the LLC resonant circuit is as claimed in claims 1 to 5 The LLC resonant circuit of any one; the LLC resonant circuit is respectively connected with the inverter/rectifier bridge and the transformer; the transformer is also connected with the rectifier/inverter bridge.

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