CN110165895A - A kind of wide gain FB-HB LLC resonant converter circuit structure of realization and control method - Google Patents

Abstract

The invention discloses a kind of wide gain FB-HB LLC resonant converter circuit structure of realization and control methods, entire controlled resonant converter topological structure is divided into three parts, first part is switching network module, and second part is resonant network module, and Part III is rectifying and wave-filtering network module.The present invention is controlled power switch tube duty ratio by digital control module and realizes dynamic transformation in the case where not turning off controlled resonant converter feeder ear；And in order to realize broader output voltage range, increase the method for winding on secondary side, the power switch by controlling controlled resonant converter pair side is in control suitable output voltage.

Description

A Circuit Structure and Control Method for Realizing Wide Gain FB-HB LLC Resonant Converter

technical field

The present invention relates to the technical field of full bridge/half bridge LLC resonant converter, in particular to a circuit structure and method based on HB (half bridge), FB (full bridge) LLC (inductance L, capacitor C) resonant converter to realize the output voltage A wider description.

Background technique

In many applications, resonant converters are required to operate over a wide output range. For example, the output voltage requirements of resonant converters used in current electric vehicle charging equipment and outdoor lighting equipment range from 24V to 144V. In order to provide a wide range of stable output voltages for power application equipment, traditional half-bridge/full-bridge LLC resonant converters control the output voltage range by changing the operating frequency of the power switch tube, that is, changing the gain of the resonant converter. This control method is easy to implement and has a simple topology. However, with the expansion of the output voltage range, in order to obtain a suitable output voltage value, the switching frequency of the power switch tube will increase or decrease accordingly, so that the frequency operating point of the power switch tube Far away from the resonant frequency point, it will increase the conduction loss of the resonant converter's transformer core and power switch tube, making the entire circuit work inefficient. In order to improve the working efficiency of the resonant converter and reduce the circuit loss, a FB (full bridge)-HB (half bridge) LLC resonant converter circuit scheme is proposed.

There is also an inherent problem in FB-HB LLC resonant converters, that is, the topology conversion process occurs suddenly. For the control of the output voltage range of the FB-HB LLC resonant converter, the topology conversion is realized by cutting off the power supply, simply stopping and then soft-starting the circuit, so as to obtain the desired output voltage value. During the conversion of the FB-HB LLC resonant converter circuit, the output voltage will produce severe voltage spikes. This will increase the voltage stress of the power switch tube and circuit components, resulting in additional conduction loss, and the overall efficiency of the resonant converter has not been significantly improved. By adding output filter capacitors, output voltage transients are reduced, but unnecessary cost and resonant converter size are added. Generally speaking, the output voltage cannot be satisfied to realize continuous change in the whole period.

In the prior art, increasing the output voltage range of the resonant converter is mostly realized by changing the switching frequency of the power switch tube and changing the duty cycle of the power switch tube. But a wider output voltage range requires a wider switching frequency range. Generally, a wide range of switching frequencies is not desirable because it has an adverse effect on the performance of the resonant converter, making the overall operation of the resonant converter unstable. If the resonant converter is not properly maintained, it will also affect its life.

Contents of the invention

The purpose of the present invention is to provide a circuit structure and method for realizing a wide-gain FB-HB hybrid control LLC resonant converter, which is to control the duty cycle of the switching tube through a digital control module to realize dynamic conversion without cutting off the power supply; Moreover, in order to achieve a wider output voltage range, the method of adding windings on the secondary side can obtain a suitable output voltage by controlling the switching tubes connected in series on the windings.

In order to achieve the above tasks, the present invention adopts the following technical solutions:

A circuit structure for realizing a wide-gain FB-HB LLC resonant converter, including a switch network, a resonant network and a rectifying and filtering network connected in sequence, wherein:

The switch network includes power switch tubes Q ₁ , Q ₂ , Q ₃ , Q ₄ , power switch tube junction capacitances C ₁ , C ₂ , C ₃ , C ₄ , power switch tube body diodes D ₁ , D ₂ , D ₃ , D ₄ , the input voltage V _in , where Q ₁ and Q ₃ are connected in series, Q ₂ and Q ₄ are connected in series, C ₁ and C ₃ are connected in series, and C ₂ and C ₄ are connected in parallel at both ends of V _in . C ₁ , C ₂ , C ₃ , and C ₄ are connected in parallel at both ends of Q ₁ , Q ₂ , Q ₃ , and Q ₄ respectively; take a point A between C ₁ and C ₃ , and connect point A to the point between D ₁ and D ₃ and between Q ₁ and Q ₃ ; take a point B between C ₂ and C ₄ , and connect point B to between D ₂ and D ₄ and between Q ₂ and Q ₄ ;

The resonant network includes a resonant capacitor C _r , a resonant inductance L _r and a magnetizing inductance L _m of the primary winding of the transformer. After C _r , L _r , and L _m are connected in series, one end is connected to the A point, and the other end is connected to the Point B above;

The rectification filter network includes four inductors L _S1 , L _S2 , L _S3 , L _S4 of the secondary winding of the transformer, freewheeling diodes _DR1 , _DR2 , _DR3 , _DR4 , power switch tube Q ₅ , filter capacitor C _f , the load _R and the output voltage V _o ; among them, after L _S1 , L _S2 , L _S3 , and L _S4 are connected in series, one end is connected to the positive pole of DR1, and the other end is connected to the positive pole of DR4; the voltage at both ends of _R is the output voltage V _o , C _f are connected in parallel at both ends of R; the positive pole of D _R2 is connected between L _S1 and L _S2 , the negative pole of D _R2 is connected to one end of C _f , and the other end of C _f is connected between L _S2 and L _S3 ; D The positive pole of _R3 is connected between _LS3 and _LS4 , the negative pole of _DR3 is connected to the negative pole of _DR2 , the negative pole of _DR4 is connected to the negative pole of _DR1 and the gate of _Q5 , the source and drain of _Q5 are connected to _DR2 the negative connection.

Further, the circuit structure further includes a digital control module, which is respectively connected to power switch tubes Q ₁ , Q ₂ , Q ₃ , Q ₄ and Q ₅ through an optocoupler isolation drive circuit.

A control method for realizing a wide-gain FB-HB LLC resonant converter, comprising the following steps:

When the resonant converter is started, it can be judged by the value of the output voltage V _o that it should work in various working modes. The method is as follows:

Calculate the resonant converter gain M using a given reference value;

When 0.8≤M<1.2, the resonant converter works in the HB LLC resonant converter mode. At this time, the working status of each power device is: Q ₄ is permanently turned on, Q ₂ and Q ₅ are permanently turned off, and Q ₁ and Q ₃ work in High-frequency switching state; Q ₁ and Q ₃ are complementary conduction, and a dead zone is set to prevent Q ₁ and Q ₃ from passing through; the switching frequency of Q ₁ and Q ₃ works near the resonance frequency point through the digital control module;

When 1.2≤M<2.4, the resonant converter works in the FB LLC resonant converter mode. At this time, the working state of each power device is: the duty cycle of Q ₄ gradually changes from 100% to 50%, and the duty cycle of Q ₂ From 0 to 50%, when the gradual change process is completed, Q ₁ , Q ₂ , Q ₃ , and Q ₄ work in the high-frequency switching state, and Q ₅ is permanently turned off; Q ₁ , Q ₃ and Q ₂ , Q ₄ are respectively complementary conduction Q ₁ , Q ₄ and Q ₂ , Q ₃ are turned on and off at the same time respectively, and dead zones are set to prevent Q ₁ , Q ₃ or Q ₂ , Q ₄ from passing through; the digital control module makes Q ₁ , Q ₂ , The switching frequency of Q ₃ and Q ₄ works near the resonant frequency point;

When 2.4≤M<4.8, the resonant converter works in the secondary multi-winding FB LLC resonant converter mode. At this time, the working status of each power device is: Q ₁ , Q ₂ , Q ₃ , and Q ₄ work in the duty cycle is a 50% high-frequency switching state, _Q5 is permanently turned on _; Q1, _Q3 and _Q2 , _Q4 are complementary conduction respectively, Q1, _Q4 and _Q2 , _Q3 are respectively turned _on and off at the same time, setting The dead zone prevents Q ₁ , Q ₃ or Q ₂ , Q ₄ from passing through; through the digital control module, the switching frequency of Q ₁ , Q ₂ , Q ₃ , Q ₄ works near the resonant frequency point.

Further, the formula for calculating the resonant frequency point is:

Further, the calculation of the gain M of the resonant converter by using a given reference value is specifically:

The resonant gain M of the resonant converter is the ratio of the output voltage V _o multiplied by the primary and secondary turn ratio of the transformer and the input voltage V _in .

Further, the specific working process of the HB LLC resonant converter mode is as follows:

(1) HB LLC resonant converter switching mode 1

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network through Q ₁ and Q ₄ , the current I _r of the resonant inductance L _r and the current I of the magnetizing inductance L _{m m} increases, the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , the freewheeling diode D _R2 is turned on, and the energy is transferred to the load;

(2) HB LLC resonant converter switching mode 1

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network through Q ₁ and Q ₄ , the current I _r of the resonant inductance L _r and the current I of the magnetizing inductance L _{m m} are equal, because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, the freewheeling diode D _R2 is not conducting, and the load is provided by the filter capacitor C _f energy;

(3) HB LLC resonant converter switching mode 2

Q ₃ and Q ₄ are turned on, Q ₁ , Q ₂ and Q ₅ are turned off, the resonant network forms a loop through Q ₃ and Q ₄ , the current I _r of the resonant inductance L _r and the current I _{m of the magnetizing inductance L m increase} , and the resonance is utilized The difference between the current I _{r of the inductance L r and} the current I _m of the magnetizing inductance L _m transfers energy to the secondary side of the transformer, the freewheeling diode D _R3 is turned on, and the energy is transferred to the load;

(4) HB LLC resonant converter switching mode 2

Q ₃ and Q ₄ are turned on, Q ₁ , Q ₂ and Q ₅ are turned off, the resonant network forms a loop through Q ₃ and Q ₄ , the current I _r of the resonant inductance L _r is equal to the current I _m of the magnetizing inductance L _m , due to the resonance The difference between the current I _{r of the inductance L r and} the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, the freewheeling diode _DR3 is not conducting, and the load is supplied with energy by the filter capacitor C _f .

Further, the specific working process of the FB LLC resonant converter is as follows:

(1) Switching mode 1 of FB LLC resonant converter

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network through Q ₁ and Q ₄ , the current I _r of the resonant inductance L _r and the current I of the magnetizing inductance L _{m m} increases, the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , the freewheeling diode D _R2 is turned on, and the energy is transmitted to the load;

(2) FB LLC resonant converter switching mode 1

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m and C _r through Q ₁ and Q ₄ , and the current I _r of the resonant inductor L _r It is equal to the current I _m of the magnetizing inductance L _m , because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, and the freewheeling diode D _R2 is not conducting , the load is powered by the filter capacitor C _f ;

(3) Switching mode 2 of FB LLC resonant converter

Q ₂ and Q ₃ are turned on, Q ₁ , Q ₄ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network through Q ₂ and Q ₃ , the current I _r of the resonant inductance L _r and the current I of the magnetizing inductance L _{m m} grows, the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , the freewheeling diode D _R3 is turned on, and the energy is transferred to the load;

(4) FB LLC resonant converter switching mode 2

Q ₂ and Q ₃ are turned on, Q ₁ , Q ₄ and Q ₅ are turned off, the resonant network forms a loop through Q ₂ and Q ₃ , the current I _r of the resonant inductance L _r is equal to the current I _m of the magnetizing inductance L _m , due to the resonance The difference between the current I _{r of the inductance L r and} the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, the freewheeling diode _DR3 is not conducting, and the load is supplied with energy by the filter capacitor C _f .

Further, the specific working process of the secondary multi-winding FB LLC resonant converter mode is as follows:

(1) Switching mode 1 of secondary multi-winding FB LLC resonant converter

Q ₁ , Q ₄ , Q ₅ are turned on, Q ₂ , Q ₃ are turned off, the input voltage V _in is added to the resonant network through Q ₁ and Q ₄ , the current I _r of the resonant inductance L _r and the current I of the magnetizing inductance L _m As _m grows, the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , the freewheeling diode D _R1 is turned on, and the energy is transferred to the load;

(2) Switching mode 1 of secondary multi-winding FB LLC resonant converter

Q ₁ , Q ₄ , Q ₅ are turned on, Q ₂ , Q ₃ are turned off, the input voltage V _in is added to the resonant network through Q ₁ and Q ₄ , the current I _r of the resonant inductance L _r and the current I of the magnetizing inductance L _{m m} are equal, because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, the freewheeling diode D _R1 is not conducting, and the load is provided by the filter capacitor C _f energy;

(3) Secondary side multi-winding FB LLC resonant converter switching mode 2

Q ₂ , Q ₃ , Q ₅ are turned on, Q ₁ , Q ₄ are turned off, the input voltage V _in is added to the resonant network through Q ₂ and Q ₃ , the current I _r of the resonant inductance L _r and the current I of the magnetizing inductance L _m As _m increases, energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , and the freewheeling diode D _R4 is turned on, and the energy is transmitted to the load;

(4) Secondary side multi-winding FB LLC resonant converter switching mode 2

Q ₂ , Q ₃ , Q ₅ are turned on, Q ₁ , Q ₄ are turned off, the resonant network forms a loop through Q ₂ and Q ₃ , the current I _r of the resonant inductance L _r is equal to the current I _m of the magnetizing inductance L _m , due to the resonance The difference between the current I _{r of the inductance L r and} the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, the freewheeling diode _DR4 is not conducting, and the load is supplied with energy by the filter capacitor C _f .

The present invention has the following technical characteristics:

1. Through the flexible use of the wide-gain FB-HB hybrid control LLC resonant converter circuit structure, the digital control module can control the turn-on and turn-off and duty cycle of the switch tubes Q2 and Q4 according to the output voltage value required by the equipment Transformation enables the circuit topology to dynamically change between half-bridge and full-bridge, so that the power converter can work more efficiently.

2. For the overall circuit topology of the wide-gain FB-HB hybrid control LLC resonant converter, the output voltage range is increased by adding windings on the secondary side, instead of realizing the same function by frequency conversion; its advantage is that it can make the switch tube work The frequency works near the resonant frequency point with the highest efficiency, which can better meet the output voltage requirements of different loads, instead of changing the operating frequency of the power switch tube, the conduction loss of the switch tube is reduced, the stability of the entire system is increased, and the efficiency Improved.

3. Wide-gain FB-HB hybrid control LLC resonant converter has a wide output voltage range, which can meet the voltage requirements of many electrical equipment. When the user has a lot of electrical equipment and the required voltage values are inconsistent, there is no need to purchase additional power converters. It saves investment costs for users and improves efficiency.

4. When the wide-gain FB-HB hybrid control LLC resonant converter is working, through reasonable design of the resonant capacitor C _r , the resonant inductance L _r , the value of the magnetizing inductance L _m and the dead time of the switch tube, the switch tube Q ₁ , Q ₂ , Q ₃ , and Q ₄ realize ZVS (Zero Voltage Switching) turn-on. The conduction loss of the switch tube is reduced, and the efficiency of the whole machine is improved.

Description of drawings

Figure 1 shows the topology of wide-gain FB-HB hybrid control LLC resonant converter;

Figure 2 is a flow chart for selecting the operating mode of the wide-gain FB-HB hybrid control LLC resonant converter;

(a) and (b) in Fig. 3 are two cases of switching mode 1 of the HB LLC resonant converter;

(a) and (b) of Fig. 4 are two cases of switching mode 2 of the HB LLC resonant converter;

(a) and (b) of Fig. 5 are two situations of switching mode 1 of the FB LLC resonant converter;

(a) and (b) in Fig. 6 are two cases of switching mode 2 of the FB LLC resonant converter;

(a) and (b) of Fig. 7 are two cases of switching mode 1 of the secondary multi-winding FB LLC resonant converter;

(a) and (b) of Fig. 8 are two cases of switching mode 2 of the secondary multi-winding FB LLC resonant converter;

Figure 9 shows the topology of a symmetrical wide-gain FB-HB hybrid control LLC resonant converter;

Figure 10 is a secondary side control type wide gain FB-HB hybrid control LLC resonant converter;

Figure 11 is a block diagram of the digital control module. In this figure, Q ₁ , Q ₂ , Q ₃ , Q ₄ , and Q ₅ are the driving signals of each switching tube; PWM1, PWM2, PWM3, PWM4, and PWM5 are the pulses generated by DSP Square wave signal; V _SET is the equipment demand voltage value set by the user through the host computer.

Detailed ways

The topological structure of the wide-gain FB-HB LLC resonant converter is shown in Figure 1. The entire resonant converter topology is divided into three parts, the first part is the switching network, the second part is the resonant network, and the third part is the rectification and filtering network.

The first part of the switch network includes power switch tubes Q ₁ , Q ₂ , Q ₃ , Q ₄ , power switch tube junction capacitances C ₁ , C ₂ , C ₃ , C ₄ , power switch tube body diodes D ₁ , D ₂ , D _3. D ₄ , the input voltage V _in , the midpoint potentials A and B of the two bridge arms. The second part of the resonant network includes the resonant capacitor C _r , the resonant inductance L _r , and the magnetizing inductance L _m of the primary winding of the transformer. The third part of the rectification filter network includes the inductance L _S1 , L _S2 , L _S3 , L _S4 of the four windings on the secondary side of the transformer, the freewheeling diodes _DR1 , _DR2 , _DR3 , _DR4 , the power switch tube Q ₅ , and the filter capacitor C _f , load R, output voltage V _o , the specific connection structure is:

In the switch network: after Q ₁ and Q ₃ are connected in series, after Q ₂ and Q ₄ are connected in series, after C ₁ and C ₃ are connected in series, after C ₂ and C ₄ are connected in series, they are all connected in parallel at both ends of V _in , and C ₁ , C ₂ , C ₃ , and C ₄ are connected in parallel at both ends of Q ₁ , Q ₂ , Q ₃ , and Q ₄ respectively; a point A is taken between C ₁ and C ₃ , and point A is connected between D ₁ , D ₃ and Q ₁ , between Q ₃ ; take a point B between C ₂ and C ₄ , and connect point B to between D ₂ and D ₄ and between Q ₂ and Q ₄ ;

In the resonant network: after C _r , L _r , and L _m are connected in series, one end is connected to the aforementioned point A, and the other end is connected to the aforementioned point B;

In the rectification and filtering network described above, after L _S1 , L _S2 , L _S3 , and L _S4 are connected in series, one end is connected to the positive pole of DR1, and the other end is connected to the positive pole of _DR4 ; the voltage at both ends of _R is the output voltage V _o , and C _{f is} connected in parallel At both ends of R; the positive pole of D _R2 is connected between L _S1 and L _S2 , the negative pole of D _R2 is connected to one end of C _f , and the other end of C _f is connected between L _S2 and L _S3 ; the positive pole of D _R3 is connected to Between _LS3 and _LS4 , the negative pole of _DR3 is connected to the negative pole of _DR2 , the negative pole of _DR4 is connected to the negative pole of _DR1 and the gate of _Q5 , and the source and drain of _Q5 are connected to the negative pole of _DR2 .

In this solution, the circuit structure also includes a digital control module, and the digital control module is respectively connected to the power switch tubes Q ₁ , Q ₂ , Q ₃ , Q ₄ and Q ₅ through the optocoupler isolation drive circuit, as shown in Figure 11, In this embodiment, the digital control module adopts a DSP controller, and the pulse square wave signal generated by it passes through the optocoupler isolation driving circuit to generate a driving signal to drive the corresponding power switch tube. The optocoupler isolation driving circuit is a conventional circuit, and will not be described in detail here. In addition, the digital control module is also used for reading the value of the output voltage V _o and calculating the gain M.

The wide-gain FB-HB hybrid control LLC resonant converter implemented in the present invention can be transformed into three circuit structures:

The first type: the HB LLC resonant converter realizes the low gain range, that is, the input voltage is in the high range, and the output voltage works under the condition of the low range.

The second type: the FB LLC resonant converter realizes the high gain range, that is, the input voltage is in the low range, and the output voltage works under the condition of the high range.

The third type: the secondary multi-winding FB LLC resonant converter realizes higher output voltage, that is, by controlling the opening of the switch tube _Q5 , the L _S1 , L _S2 , L _S3 , L _S4 secondary windings and the load generate a loop, so that The output voltage is higher.

Set the operating frequency of the resonant converter power switch tubes Q ₁ , Q ₂ , Q ₃ , and Q ₄ as near the resonant frequency point. According to the requirements of the equipment for the output voltage value of the resonant converter, if the required voltage is at a lower value in the designed output voltage range, the resonant converter can be converted through a digital control module (as shown in Figure 11, which is a DSP controller in this embodiment). The converter works in the state of HBLLC resonant converter; if the required voltage is in the middle value of the designed output voltage range, the resonant converter works in the state of FB LLC resonant converter through the digital control module; if the required voltage is in the design output voltage range higher When the value is , the resonant converter works in the secondary multi-winding FB LLC resonant converter state through the digital control module.

1. Selection method of working mode of wide-gain FB-HB hybrid control LLC resonant converter

After the start-up of the resonant converter is completed, the voltage value V _o required by the equipment is sent to the digital control module, and then it is judged which working mode the wide-gain FB-HB LLC resonant converter should work in. The resonant network gain M of the resonant converter is the output voltage multiplied by the ratio of the primary and secondary turns of the transformer to the input voltage, n is the turns ratio of the primary and secondary windings of the transformer, and the number of turns of the primary winding of the transformer is defined as N _p . The number of turns of a single winding on the secondary side is N _s , the input voltage is V _in , and the output voltage is V _o . In this embodiment, the value range of the resonant network gain M of the resonant converter is 0.8-4.8. The flow chart of operating mode selection of wide gain FB-HB LLC resonant converter is shown in Figure 2.

2. Details of the three working modes

In Figure 2, the wide-gain FB-HB hybrid control LLC resonant converter has four operating modes. When the wide-gain FB-HB hybrid control LLC resonant converter fails, the entire circuit stops working. After the fault is repaired, it is generally necessary to manually switch the power switch to restart the converter. The following mainly introduces the other three working modes in detail.

2.1 HB LLC resonant converter mode

After the entire system of the power converter is started, the output voltage value required by the user equipment is in the low output voltage range, that is, when the gain M of the resonant network is: 0.5≤M<1, in this case the system selects the power converter to work at HB LLC resonant converter mode. The status of each power device in the HB LLC resonant converter mode is as follows: Q ₄ is permanently turned on, Q ₂ and Q ₅ are permanently turned off, Q ₁ and Q ₃ work in the high-frequency switching state; Q ₁ and Q ₃ are complementary to conduction, and the dead zone is set for Prevent the upper and lower switching tubes Q ₁ and Q ₃ from passing through, and make the switching frequency of Q ₁ and Q ₃ work near the resonant frequency point through the digital control module; the resonant capacitor C _r , the resonant inductance L _r , and the magnetizing inductance L _m together form a resonant circuit, The secondary winding inductance and the secondary freewheeling diode transmit the energy received by the primary to the load. In this mode, the input voltage V _in of the switching network and the output voltage V _o of the rectification and filtering network. The basic relationship of the HB LLC resonant converter is: n=N _p /N _s .

The specific working process of HB LLC resonant converter is:

(1) HB LLC resonant converter switching mode one (the first case), as shown in (a) of Figure 3:

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m and C _r through Q ₁ and Q ₄ , and the current I _r of the resonant inductor L _r The current I _m of the magnetizing inductance L _m increases, and the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , and the freewheeling diode D _R2 of the secondary side is turned on, and the energy transmitted to the load.

(2) HB LLC resonant converter switching mode one (the second case), as shown in (b) of Figure 3:

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m and C _r through Q ₁ and Q ₄ , and the current I _r of the resonant inductor L _r It is equal to the current I _m of the magnetizing inductance L _m , because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, and the freewheeling diode D _R2 of the secondary side does not When it is turned on, the load is supplied with energy by the filter capacitor C _f .

(3) HB LLC resonant converter switching mode 2 (the first case), as shown in (a) of Figure 4:

Q ₃ and Q ₄ are turned on, Q ₁ , Q ₂ and Q ₅ are turned off, the resonant network L _r , L _m , C _r forms a loop through Q ₃ and Q ₄ , the current I _r of the resonant inductance L _r and the magnetizing inductance L _m The current I _m increases, and the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , and the freewheeling diode _DR3 on the secondary side is turned on, and the energy is transmitted to the load.

(4) HB LLC resonant converter switching mode two (the second case), as shown in (b) of Figure 4:

Q ₃ and Q ₄ are turned on, Q ₁ , Q ₂ and Q ₅ are turned off, the resonant network L _r , L _m , C _r forms a loop through Q ₃ and Q ₄ , the current I _r of the resonant inductance L _r and the magnetizing inductance L _m The current I _m of the resonant inductance L r and the current I m of the magnetizing inductance L m are equal, because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, the freewheeling diode D _R3 of the secondary side is not conducting, and the load is controlled by Filter capacitor C _f provides energy.

2.2 FB LLC resonant converter mode

When the power converter starts to work in the HB LLC resonant converter mode, the output voltage value required by the user equipment is in the middle output voltage range, that is, when the resonant network gain M is: 1≤M<1.5, in this case the system selects The power converter works in FB LLC resonant converter mode. The status of each power device in FB LLC resonant converter mode is as follows: the duty cycle of Q ₄ gradually changes from 100% to 50%, and the duty cycle of Q ₂ gradually changes from 0 to 50%. After the gradual change process is completed, Q ₁ and Q ₂ , Q ₃ , Q ₄ work in the high-frequency switching state, Q ₅ is permanently closed; Q ₁ , Q ₃ and Q ₂ , Q ₄ are complementary conduction respectively, and Q ₁ , Q ₄ and Q ₂ , Q ₃ are respectively conduction and Turn off, and set a dead zone to prevent the upper and lower switching tubes from passing through, the switching frequency of Q ₁ , Q ₂ , Q ₃ , and Q ₄ works near the resonant frequency point through the digital control module; the resonant capacitor C _r , the resonant inductance L _r , The magnetizing inductance L _m together constitutes a resonant circuit, and the secondary winding inductance and the secondary freewheeling diode transmit the energy received by the primary side to the load. In this mode, the input voltage V _in of the switching network and the output voltage V _o of the rectification and filtering network. The basic relationship of the FB LLC resonant converter is:

The specific working process of FB LLC resonant converter is:

(1) FB LLC resonant converter switching mode one (the first case), as shown in (a) of Figure 5:

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m and C _r through Q ₁ and Q ₄ , and the current I _r of the resonant inductor L _r The current I _m of the magnetizing inductance L _m increases, and the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , and the freewheeling diode D _R2 of the secondary side is turned on, and the energy transmitted to the load.

(2) FB LLC resonant converter switching mode one (the second case), as shown in (b) of Figure 5:

Q ₁ and Q ₄ are turned on, Q ₂ , Q ₃ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m and C _r through Q ₁ and Q ₄ , and the current I _r of the resonant inductor L _r It is equal to the current I _m of the magnetizing inductance L _m , because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, and the freewheeling diode D _R2 of the secondary side does not When it is turned on, the load is supplied with energy by the filter capacitor C _f .

(3) FB LLC resonant converter switching mode 2 (the first case), as shown in (a) of Figure 6:

Q ₂ and Q ₃ are turned on, Q ₁ , Q ₄ and Q ₅ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m and C _r through Q ₂ and Q ₃ , the current I _r of the resonant inductor L _r The current I _m of the magnetizing inductance L _m increases, and the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , and the freewheeling diode D _R3 of the secondary side is turned on, and the energy transmitted to the load.

(4) FB LLC resonant converter switching mode two (second case), as shown in (b) of Figure 6:

Q ₂ , Q ₃ are turned on, Q ₁ , Q ₄ , Q ₅ are turned off, the resonant network L _r , L _m , C _r forms a loop through Q ₂ and Q ₃ , the current I _r of the resonant inductance L _r and the magnetizing inductance L _m The current I _m of the resonant inductance L r and the current I m of the magnetizing inductance L m are equal to each other. Since the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, and the freewheeling diode D _R3 of the secondary side is not turned on. Filter capacitor C _f provides energy.

2.3 Secondary multi-winding FB LLC resonant converter mode

When the power converter starts to work in the FB LLC resonant converter mode, the output voltage value required by the user equipment is in the high output voltage range, that is, when the resonant network gain M is: 1.5≤M<2, in this case the system selects The power converter works in the secondary multi-winding FB LLC resonant converter mode. The state of each power device in the secondary side multi-winding FB LLC resonant converter mode is as follows: Q ₁ , Q ₂ , Q ₃ , Q ₄ work in the high-frequency switching state with a duty cycle of 50%, Q ₅ is permanently turned on; Q ₁ , Q ₃ and Q ₂ , Q ₄ are complementary conduction respectively, Q ₁ , Q ₄ , Q ₂ , Q ₃ are respectively on and off at the same time, and a dead zone is set to prevent the upper and lower switching tubes from being directly connected, and the digital control module makes Q ₁ , Q 4 The switching frequency of Q ₂ , Q ₃ , and Q ₄ works near the resonant frequency point; the resonant capacitor C _r , the resonant inductance L _r , and the magnetizing inductance L _m together form a resonant circuit, and the secondary winding inductance and the secondary freewheeling diode connect the primary side The received energy is transferred to the load. In this mode, the input voltage V _in of the switching network and the output voltage V _o of the rectification and filtering network. The basic relationship of the secondary multi-winding FB LLC resonant converter is: n=N _p /(2*N _s ).

The specific working process of the secondary side multi-winding FB LLC resonant converter case 1 is:

(1) Switching mode 1 (the first case) of the secondary multi-winding FB LLC resonant converter, as shown in (a) of Figure 7:

Q ₁ , Q ₄ , Q ₅ are turned on, Q ₂ , Q ₃ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m , C _r through Q ₁ and Q ₄ , and the current I _r of the resonant inductor L _r The current I _m of the magnetizing inductance L _m increases, and the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , and the freewheeling diode D _R1 of the secondary side is turned on, and the energy transmitted to the load.

(2) Switching mode 1 (second case) of secondary multi-winding FB LLC resonant converter, as shown in (b) of Figure 7:

Q ₁ , Q ₄ , Q ₅ are turned on, Q ₂ , Q ₃ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m , C _r through Q ₁ and Q ₄ , and the current I _r of the resonant inductor L _r It is equal to the current I _m of the magnetizing inductance L _m , because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, and the freewheeling diode D _R1 of the secondary side is not When it is turned on, the load is supplied with energy by the filter capacitor C _f .

(3) Switching mode 2 (the first case) of the secondary multi-winding FB LLC resonant converter, as shown in (a) of Figure 8:

Q ₂ , Q ₃ , Q ₅ are turned on, Q ₁ , Q ₄ are turned off, the input voltage V _in is applied to the resonant network L _r , L _m , C _r through Q ₂ and Q ₃ , and the current I _r of the resonant inductor L _r The current I _m of the magnetizing inductance L _m increases, and the energy is transferred to the secondary side of the transformer by using the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m , and the freewheeling diode D _R4 of the secondary side is turned on, and the energy transmitted to the load.

(4) Switching mode 2 (the second case) of the secondary multi-winding FB LLC resonant converter, as shown in (b) of Figure 8:

Q ₂ , Q ₃ , Q ₅ are turned on, Q ₁ , Q ₄ are turned off, the resonant network L _r , L _m , C _r forms a loop through Q ₂ and Q ₃ , the current I _r of the resonant inductance L _r and the magnetizing inductance L _m The current I _m of the resonant inductance L r is equal to the current I m of the magnetizing inductance L m because the difference between the current I _r of the resonant inductance L _r and the current I _m of the magnetizing inductance L _m is zero, the energy cannot be transferred to the secondary side of the transformer, the freewheeling diode _DR4 of the secondary side is not conducting, and the load is controlled by Filter capacitor C _f provides energy.

In addition to the above technical solutions, the topology of the wide-gain FB-HB hybrid control LLC resonant converter shown in Figure 1 can also be replaced with a symmetrical wide-gain FB-HB hybrid control LLC resonant converter, as shown in Figure 9. The entire resonant converter topology is divided into three parts, the first part is the switching network module, the second part is the resonant network module, and the third part is the rectifying and filtering network module. Only the first part of the resonant converter topology is different from the resonant converter topology shown in Figure 1, and the other two parts are the same. Symmetric wide-gain FB-HB LLC resonant converter topology The first part of the switch network module mainly includes power switch tubes Q ₁ , Q ₂ , Q ₃ , Q ₄ , Q ₆ , Q ₇ , neutral point potential balancing capacitors C ₅ , C _6. Power switch tube junction capacitance C ₁ , C ₂ , C ₃ , C ₄ , power switch tube body diodes D ₁ , D ₂ , D ₃ , D ₄ , input voltage V _in , midpoint potentials A and B of the two bridge arms . The resonant converter topology works in the same way as the resonant converter shown in Figure 1, and is mainly divided into three parts: (1) The HBLLC resonant converter realizes the low gain range, that is, the input voltage is in the high range and the output voltage is in the low range. (2) FB LLC resonant converter achieves a high gain range, that is, the input voltage is in a low range and the output voltage works in a high range; (3) the secondary side multi-winding FB LLC resonant converter achieves a higher output Voltage, that is, by controlling the turn-on of the power switch tube _Q5 on the secondary side of the resonant converter, the inductance L _S1 , L _S2 , L _S3 , and L _S4 of each winding on the secondary side of the transformer will form a loop with the load, resulting in a higher output voltage. The symmetrical wide-gain FB-HB LLC resonant converter can reduce the input current ripple and the voltage stress of the input bus capacitance through capacitors C ₅ and C ₆ , and effectively suppress the overshoot of the primary side resonant current, prevent circuit damage, and improve Overall efficiency.

In addition, the switching tube Q ₅ is removed, and the freewheeling diodes _DR2 and _DR4 are replaced with power switching tubes Q ₆ and Q ₇ . The circuit topology diagram is shown in Fig. 10 . The entire resonant converter topology is divided into three parts, the first part is the switching network module, the second part is the resonant network module, and the third part is the rectifying and filtering network module. Only the third part of the resonant converter topology is different from the resonant converter topology shown in Figure 1, and the other two parts are the same. The topology of the secondary-side controlled wide-gain FB-HBLLC resonant converter The third part of the rectification and filtering network module mainly includes the inductors L _S1 , L _S2 , L _S3 , and L _S4 of the four windings on the secondary side of the transformer, and the freewheeling diodes D _R2 and D _R3 , power switch tubes Q ₆ and Q ₇ , filter capacitor C _f , load R, and output voltage V _o . The working mode of the secondary-side controlled wide-gain FB-HB LLC resonant converter topology is the same as that of the resonant converter shown in Fig. 1 . The resonant converter controls the switch tubes Q ₆ and Q ₇ through a digital control module, so that the secondary windings can be combined arbitrarily, so that the output voltage can be adjusted more flexibly, and the coil utilization rate of the secondary windings can be increased. However, due to the asymmetry of the voltage values on both sides of the center tap of the secondary side, the output voltage value is unstable, which increases the device loss of the electrical equipment and reduces the service life.

Claims (8)

1. a kind of circuit structure for realizing wide gain FB-HB LLC resonant converter, including sequentially connected switching network, resonance Network and rectifying and wave-filtering network, it is characterised in that:

The switching network includes power switch tube Q₁、Q₂、Q₃、Q₄, power switch junction capacitance C₁、C₂、C₃、C₄, power switch Tube body diode D₁、D₂、D₃、D₄, input voltage V_in, wherein Q₁、Q₃After series connection, Q₂、Q₄After series connection, C₁、C₃After series connection, C₂、C₄String V is connected in parallel on after connection_inBoth ends, C₁、C₂、C₃、C₄It is connected in parallel on Q respectively₁、Q₂、Q₃、Q₄Both ends；In C₁、C₃Between take point A, A a point connect It is connected to D₁、D₃Between and Q₁、Q₃Between；In C₂、C₄Between take point B, B a point to be connected to D₂、D₄Between and Q₂、Q₄Between；

The resonant network includes resonant capacitance C_r, resonant inductance L_rWith the magnetizing inductance L of transformer primary winding_m, wherein C_r、 L_r、L_mAfter series connection, one end connection A point, the other end connection B point；

The rectifying and wave-filtering network includes four inductance L of transformer secondary winding_S1、L_S2、L_S3、L_S4, sustained diode_R1、 D_R2、D_R3、D_R4, power switch tube Q₅, filter capacitor C_f, load R and output voltage V_o；Wherein, L_S1、L_S2、L_S3、L_S4After series connection, One end connects D_R1Anode, the other end connect D_R4Anode；The voltage at the both ends R is output voltage V_o, C_fIt is connected in parallel on the both ends R；D_R2 Anode be connected to L_S1And L_S2Between, D_R2Cathode connect C_fOne end, C_fThe other end be connected to L_S2、L_S3Between；D_R3Just Pole is connected to L_S3、L_S4Between, D_R3Cathode connect D_R2Cathode, D_R4Cathode connect D_R1Cathode and Q₅Grid, Q₅'s Source electrode, drain electrode and D_R2Cathode connection.

2. the circuit structure as described in claim 1 for realizing wide gain FB-HB LLC resonant converter, which is characterized in that institute The circuit structure stated further includes digital control module, and digital control module is separately connected power by optical couple isolation drive circuit and opens Close pipe Q₁、Q₂、Q₃、Q₄And Q₅。

3. a kind of control method for realizing wide gain FB-HB LLC resonant converter, which comprises the following steps:

After controlled resonant converter starting, pass through output voltage V_oValue judgement should work in various operating modes, method are as follows:

Controlled resonant converter gain M is calculated using given reference value；

As 0.8≤M < 1.2, controlled resonant converter works in HB LLC resonant converter mode, the at this time work of each power device State are as follows: Q₄It is permanent to open, Q₂、Q₅It is permanent to close, Q₁、Q₃Work is in HF switch state；Q₁、Q₃Complementation conducting, is arranged dead zone To prevent Q₁、Q₃It is straight-through；Make Q by digital control module₁、Q₃Switching frequency operation near resonant frequency point；

As 1.2≤M < 2.4, controlled resonant converter works in FB LLC resonant converter mode, the at this time work of each power device State are as follows: Q₄Duty ratio be gradient to 50%, Q by 100%₂Duty ratio be gradient to 50% by 0, when progressive formation completion after, Q₁、Q₂、Q₃、Q₄Work is in HF switch state, Q₅It is permanent to close；Q₁、Q₃And Q₂、Q₄Complementary conducting respectively, Q₁、Q₄And Q₂、Q₃Point It does not simultaneously turn on and turns off, dead zone is set to prevent Q₁、Q₃Or Q₂、Q₄It is straight-through；Make Q by digital control module₁、Q₂、Q₃、Q₄'s Switching frequency operation is near resonant frequency point；

As 2.4≤M < 4.8, controlled resonant converter work is in secondary side Multiple coil FB LLC resonant converter mode, each power at this time The working condition of device are as follows: Q₁、Q₂、Q₃、Q₄The HF switch state that work is 50% in duty ratio, Q₅It is permanent open-minded；Q₁、Q₃With Q₂、Q₄Complementary conducting respectively, Q₁、Q₄And Q₂、Q₃It simultaneously turns on and turns off respectively, dead zone is set to prevent Q₁、Q₃Or Q₂、Q₄It is straight-through； Make Q by digital control module₁、Q₂、Q₃、Q₄Switching frequency operation near resonant frequency point.

4. the control method as claimed in claim 3 for realizing wide gain FB-HB LLC resonant converter, which is characterized in that institute The calculation formula for the resonant frequency point stated are as follows:

5. the control method as claimed in claim 3 for realizing wide gain FB-HB LLC resonant converter, which is characterized in that institute The given reference value of the utilization stated calculates controlled resonant converter gain M, specifically:

Controlled resonant converter resonance gain M is output voltage V_oMultiplied by the transformer primary pair side turn ratio and input voltage V_inRatio.

6. the control method as claimed in claim 3 for realizing wide gain FB-HB LLC resonant converter, which is characterized in that institute The specific work process for the HB LLC resonant converter mode stated are as follows:

(1) HB LLC resonant converter switchs mode one

Q₁、Q₄It is open-minded, Q₂、Q₃、Q₅Shutdown, input voltage V_inPass through Q₁And Q₄It is added on resonant network, resonant inductance L_rElectric current I_r With magnetizing inductance L_mElectric current I_mIncrease, utilizes resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference energy is passed It is delivered to transformer secondary, sustained diode_R2Conducting, energy transmission to load；

(2) HB LLC resonant converter switchs mode one

Q₁、Q₄It is open-minded, Q₂、Q₃、Q₅Shutdown, input voltage V_inPass through Q₁And Q₄It is added on resonant network, resonant inductance L_rElectric current I_r With magnetizing inductance L_mElectric current I_mIt is equal, due to resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference be zero, energy Amount can not be transmitted to transformer secondary, sustained diode_R2It is not turned on, loads by filter capacitor C_fEnergy is provided；

(3) HB LLC resonant converter switchs mode two

Q₃、Q₄It is open-minded, Q₁、Q₂、Q₅Shutdown, resonant network pass through Q₃And Q₄Forming circuit, resonant inductance L_rElectric current I_rWith magnetization electricity Feel L_mElectric current I_mIncrease, utilizes resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference transfer energy to transformation Device pair side, sustained diode_R3Conducting, energy transmission to load；

(4) HB LLC resonant converter switchs mode two

Q₃、Q₄It is open-minded, Q₁、Q₂、Q₅Shutdown, resonant network pass through Q₃And Q₄Forming circuit, resonant inductance L_rElectric current I_rWith magnetization electricity Feel L_mElectric current I_mIt is equal, due to resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference be zero, energy can not pass It is delivered to transformer secondary, sustained diode_R3It is not turned on, loads by filter capacitor C_fEnergy is provided.

7. the control method as claimed in claim 3 for realizing wide gain FB-HB LLC resonant converter, which is characterized in that institute The FB LLC resonant converter specific work process stated are as follows:

(1) FB LLC resonant converter switchs mode one

Q₁、Q₄It is open-minded, Q₂、Q₃、Q₅Shutdown, input voltage V_inPass through Q₁And Q₄It is added on resonant network, resonant inductance L_rElectric current I_r With magnetizing inductance L_mElectric current I_mIncrease, utilizes resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference energy is passed It is delivered to transformer secondary, sustained diode_R2Conducting, energy transmission to load；

(2) FB LLC resonant converter switchs mode one

Q₁、Q₄It is open-minded, Q₂、Q₃、Q₅Shutdown, input voltage V_inPass through Q₁And Q₄It is added to resonant network L_r、L_m、C_rOn, resonant inductance L_r Electric current I_rWith magnetizing inductance L_mElectric current I_mIt is equal, due to resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference It is zero, energy can not be transmitted to transformer secondary, sustained diode_R2It is not turned on, loads by filter capacitor C_fEnergy is provided；

(3) FB LLC resonant converter switchs mode two

Q₂、Q₃It is open-minded, Q₁、Q₄、Q₅Shutdown, input voltage V_inPass through Q₂And Q₃It is added on resonant network, resonant inductance L_rElectric current I_r With magnetizing inductance L_mElectric current I_mIncrease, utilizes resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference energy is passed It is delivered to transformer secondary, sustained diode_R3Conducting, energy transmission to load；

(4) FB LLC resonant converter switchs mode two

Q₂、Q₃It is open-minded, Q₁、Q₄、Q₅Shutdown, resonant network pass through Q₂And Q₃Forming circuit, resonant inductance L_rElectric current I_rWith magnetization electricity Feel L_mElectric current I_mIt is equal, due to resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference be zero, energy can not pass It is delivered to transformer secondary, sustained diode_R3It is not turned on, loads by filter capacitor C_fEnergy is provided.

8. the control method as claimed in claim 3 for realizing wide gain FB-HB LLC resonant converter, which is characterized in that institute The specific work process for the secondary side Multiple coil FB LLC resonant converter mode stated are as follows:

(1) secondary side Multiple coil FB LLC resonant converter switchs mode one

Q₁、Q₄、Q₅It is open-minded, Q₂、Q₃Shutdown, input voltage V_inPass through Q₁And Q₄It is added on resonant network, resonant inductance L_rElectric current I_r With magnetizing inductance L_mElectric current I_mIncrease, utilizes resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference energy is passed It is delivered to transformer secondary, sustained diode_R1Conducting, energy transmission to load；

(2) secondary side Multiple coil FB LLC resonant converter switchs mode one

Q₁、Q₄、Q₅It is open-minded, Q₂、Q₃Shutdown, input voltage V_inPass through Q₁And Q₄It is added on resonant network, resonant inductance L_rElectric current I_r With magnetizing inductance L_mElectric current I_mIt is equal, due to resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference be zero, energy Amount can not be transmitted to transformer secondary, sustained diode_R1It is not turned on, loads by filter capacitor C_fEnergy is provided；

(3) secondary side Multiple coil FB LLC resonant converter switchs mode two

Q₂、Q₃、Q₅It is open-minded, Q₁、Q₄Shutdown, input voltage V_inPass through Q₂And Q₃It is added on resonant network, resonant inductance L_rElectric current I_r With magnetizing inductance L_mElectric current I_mIncrease, utilizes resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference energy is passed It is delivered to transformer secondary, sustained diode_R4Conducting, energy transmission to load；

(4) secondary side Multiple coil FB LLC resonant converter switchs mode two

Q₂、Q₃、Q₅It is open-minded, Q₁、Q₄Shutdown, resonant network pass through Q₂And Q₃Forming circuit, resonant inductance L_rElectric current I_rWith magnetization electricity Feel L_mElectric current I_mIt is equal, due to resonant inductance L_rElectric current I_rWith magnetizing inductance L_mElectric current I_mDifference be zero, energy can not pass It is delivered to transformer secondary, sustained diode_R4It is not turned on, loads by filter capacitor C_fEnergy is provided.