An interleaved voltage-multiplied wide-output LLC resonant converter and a control method thereof

Abstract

The present application relates to a kind of wide voltage output range LLC converter circuit and its control method.The circuit includes: for the square wave voltage of direct current input voltage inversion inverter network;Resonant network: for the series resonance of circuit, so that inductive reactance and capacitive reactance in the circuit have the effect of mutual offset, when the reactance in series circuit is 0, current and voltage are in phase;High-frequency transformer group: for electrical isolation and voltage regulation;Rectifier network: for the alternating current of transformer secondary side output is converted into direct current, according to the difference of control mode, automatically adjust the working proportion of full-bridge rectification and voltage doubling rectification in a period, make low output voltage smooth switching to high output voltage.The present application realizes the ability of LLC converter wide output voltage regulation, using fixed-frequency PWM control, without considering the low efficiency, low power density and other problems brought by wide switching frequency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power electronics, and particularly relates to a circuit of a wide-voltage-output-range LLC converter and a control method thereof. BACKGROUND

[0002] With the rapid development of power electronics technology, the requirements for switching power supplies are getting higher and higher. In some special DC-DC conversion fields, such as renewable energy systems, LED drivers, electric vehicles, etc., a wide voltage regulation range and electrical isolation are required. LLC resonant converters have a wide application in the above wide output voltage fields due to their excellent soft switching performance, high switching frequency and high power density. Pulse frequency modulation is the most commonly used control method for LLC converters. However, in applications requiring a wide output voltage, the switching frequency must work in a wide range to meet the wide voltage output range. The volume and weight of the transformer of the LLC converter significantly increase at low switching frequency, which is very detrimental to the miniaturization design of the LLC converter, hindering the development of switching power supplies in the direction of high power density. And the soft switching performance of the converter is missing at a wide switching frequency, the switching loss and conduction loss are very large, and the energy conversion efficiency is very low. SUMMARY

[0003] In order to solve the above problems, the application provides an interleaved voltage doubling LLC resonant converter circuit and a control method thereof.

[0004] An interleaved voltage doubling wide output LLC resonant converter, characterized in that,

[0005] Inverter network: used for inverting the direct current input voltage into a square wave voltage.

[0006] Resonant network: used for series resonance of the circuit, so that the inductive reactance and the capacitive reactance in the circuit have a mutual offsetting effect, at this time the reactance in the series circuit is 0, and the current and the voltage are in phase.

[0007] High-frequency transformer group: used for electrical isolation and voltage regulation.

[0008] Rectifier network: used for converting the alternating current output from the secondary side of the transformer into direct current, according to different control methods, the working proportion of full-bridge rectification and voltage doubling rectification in a cycle is automatically adjusted, so that the low output voltage is smoothly switched to the high output voltage.

[0009] In the above-mentioned interleaved voltage doubling wide output LLC resonant converter, the inverter network comprises a direct current input power supply U in , a first switch tube S1, a second switch tube S2, a third switch tube S3 and a fourth switch tube S4; the first switch tube S1 and the second switch tube S2 are connected in series at the head and tail, and the drain electrode of the first switch tube S1 is connected to the direct current input power supply U inThe positive terminal of the first switch S1 is connected to the drain of the second switch S2, and the source of the second switch S2 is connected to the DC input power supply U. in The negative terminal. The third switch S3 and the fourth switch S4 are connected in series, and the drain of the third switch S3 is connected to the DC input power supply U. in The positive terminal of the fourth switch S4 is connected to the source of the third switch S3, and the source of the fourth switch S4 is connected to the DC input power supply U. in The negative electrode.

[0010] In the aforementioned interleaved voltage-multiplying wide-range output LLC resonant converter, the resonant network includes a first resonant capacitor C. r1 Second resonant capacitor C r2 First resonant inductor L r1 Second resonant inductor L r2 First excitation inductor L m1 Second excitation inductor L m2 The first resonant capacitor C r1 The left end is connected to the common terminal of the series connection of the first switch S1 and the second switch S2, and the right end is connected to the first resonant inductor L. r1 The two are connected in series, and then connected to the first magnetizing inductor L. m1 Series connection, first magnetizing inductor L m1 The other end is connected to the source of the second switch S2; simultaneously, the first magnetizing inductor L m1 It is connected in parallel with the primary winding of the first high-frequency transformer T1, thus forming the upper half-bridge structure on the primary side. The second resonant capacitor C r2 The left end is connected to the common terminal of the series connection of the third switch S3 and the fourth switch S4, and the right end is connected to the second resonant inductor L. r2 The two are connected in series, and then connected to the second magnetizing inductor L. m2 Series connection, second magnetizing inductor L m2 The other end is connected to the source of the fourth switch S4; simultaneously, the second magnetizing inductor L m2 It is connected in parallel with the primary winding of the second high-frequency transformer T2 to form a primary-side lower half-bridge structure.

[0011] In the aforementioned interleaved voltage-width multiplier output LLC resonant converter, the rectifier network includes a first rectifier diode D1, a second rectifier diode D2, a third rectifier diode D3, a fourth rectifier diode D4, and a fifth switching transistor. Sixth switching transistor First filter capacitor C 01 Second filter capacitor C 02 Equivalent resistive load R0; Fifth switching transistor Sixth switch The first rectifier diode D1 and the second rectifier diode D2 constitute a bidirectional switch, the positive pole of the third rectifier diode D3 and the negative pole of the fourth rectifier diode D4 are connected in series, the negative pole of the first rectifier diode D1 is connected to the negative pole of the third rectifier diode D3, and the positive pole of the second rectifier diode D2 is connected to the positive pole of the fourth rectifier diode D4. The common end of the negative pole of the first rectifier diode D1 and the negative pole of the third rectifier diode D3 is connected to the positive pole of the first filter capacitor C 01 The common end of the positive pole of the second rectifier diode D2 and the positive pole of the fourth rectifier diode D4 is connected to the negative pole of the second filter capacitor C 02 The negative pole of the first filter capacitor C 01 is connected in series with the positive pole of the second filter capacitor C 02 An equivalent resistive load R0 is connected in parallel with the two series filter capacitors. The drain of the fifth switch tube is connected to the common end of the positive pole of the third rectifier diode D3 and the negative pole of the fourth rectifier diode D4, and the source of the fifth switch tube is connected to the source of the sixth switch tube The drain of the sixth switch tube is connected to the common end of the negative pole of the first filter capacitor C 01 and the positive pole of the second filter capacitor C 02 .

[0012] In the above-mentioned interleaved voltage-doubled wide-output LLC resonant converter, the high-frequency transformer set includes a first high-frequency transformer T1 and a second high-frequency transformer T2; the positive pole of the secondary side of the first high-frequency transformer T1 is connected to the common end of the first rectifier diode D1 and the second rectifier diode D2, the negative pole of the secondary side of the first high-frequency transformer T1 is connected in series with the positive pole of the secondary side of the second high-frequency transformer T2, and the negative pole of the secondary side of the second high-frequency transformer T2 is connected to the common end of the third rectifier diode D3 and the fourth rectifier diode D4.

[0013] The application discloses a control method of an interleaved voltage-doubler wide-output LLC resonant converter, characterized in that a fixed-frequency pulse width (PWM) control is adopted, and the first switch S1 and the second switch S2 are complementarily turned on with a duty cycle of 0.5. The third switch S3 and the fourth switch S4 of the lower half-bridge are complementarily turned on, and the duty cycle of the fourth switch S4 is D, and the regulation range of D is 0-0.5. Meanwhile, the third switch S3 and the first switch S1 have the same phase, the fourth switch S4 and the second switch S2 are turned off at the same time, the fifth switch S5 and the sixth switch S6 of the secondary side have the same driving signal as the third switch S3 and the fourth switch S4, the switching frequency is fixed and equal to the resonant frequency, the working time of the fourth switch S4 of the primary side in one cycle is changed, the primary side is converted from being connected to the upper half-bridge to being connected to the upper and lower half-bridges to realize 2 times voltage gain regulation, and the secondary side is adaptively rectified by cooperating with the control of the bidirectional switch, the rectification network is converted from full-bridge rectification to voltage-doubler rectification, and then 4 times wide-output voltage regulation range is realized.

[0014] In the control method, when the primary side is connected to the upper half-bridge only, the converter works in a low-voltage mode, at this time, the first switch S1 and the second switch S2 are complementarily turned on with a duty cycle of 0.5, the lower half-bridge does not transfer energy to the load, the fifth switch S5 and the sixth switch S6 of the secondary side are turned off and do not work, and the rectification network works in a full-bridge rectification mode. At this time, the converter is equivalent to a half-bridge LLC resonant converter, and the output voltage is the lowest. In the control method, when the primary side is connected to the upper half-bridge only, the converter works in a low-voltage mode, at this time, the first switch S1 and the second switch S2 are complementarily turned on with a duty cycle of 0.5, the lower half-bridge does not transfer energy to the load, the fifth switch S5 and the sixth switch S6 of the secondary side are turned off and do not work, and the rectification network works in a full-bridge rectification mode. At this time, the converter is equivalent to a half-bridge LLC resonant converter, and the output voltage is the lowest.

[0015] In the control method, when the primary side is connected to the upper half-bridge only, the converter works in a low-voltage mode, at this time, the first switch S1 and the second switch S2 are complementarily turned on with a duty cycle of 0.5, the lower half-bridge does not transfer energy to the load, the fifth switch S5 and the sixth switch S6 of the secondary side are turned off and do not work, and the rectification network works in a full-bridge rectification mode. At this time, the converter is equivalent to a half-bridge LLC resonant converter, and the output voltage is the lowest. In the control method, when the primary side is connected to the upper half-bridge only, the converter works in a low-voltage mode, at this time, the first switch S1 and the second switch S2 are complementarily turned on with a duty cycle of 0.5, the lower half-bridge does not transfer energy to the load, the fifth switch S5 and the sixth switch S6 of the secondary side are turned off and do not work, and the rectification network works in a full-bridge rectification mode. At this time, the converter is equivalent to a half-bridge LLC resonant converter, and the output voltage is the lowest.

[0016] In the control method, when the primary side is connected to the upper half-bridge only, the converter works in a low-voltage mode, at this time, the first switch S1 and the second switch S2 are complementarily turned on with a duty cycle of 0.5, the lower half-bridge does not transfer energy to the load, the fifth switch S5 and the sixth switch S6 of the secondary side are turned off and do not work, and the rectification network works in a full-bridge rectification mode. At this time, the converter is equivalent to a half-bridge LLC resonant converter, and the output voltage is the lowest. ​​​​​Under the action of the auxiliary side rectifier network automatically adjusts the full-bridge rectification and voltage doubling rectification in a cycle, the rectification mode gradually changes from full-bridge rectification to voltage doubling rectification, and in this period, the full-bridge and voltage doubling rectification modes exist and work simultaneously. Without changing the switching frequency, only by changing the duty cycle, the smooth switching from low output voltage to high output voltage can be realized.

[0017] The essential difference between the present application and the prior art is that all the switching tubes adopt a fixed frequency PWM control strategy, the primary side can change the access duty cycle of the half-bridge, and through the smooth switching of the secondary side full-bridge rectification mode, full-bridge / voltage doubling hybrid rectification mode and voltage doubling rectification mode, a wider output voltage regulation range is obtained. In terms of control method, the switching frequency is always equal to the series resonance frequency, always working at the best efficiency point, the design requirements for magnetizing inductance and transformer and other magnetic components are low, which is beneficial to the miniaturization design and high power density of the converter.

[0018] Advantages

[0019] (1) The present application realizes the wide output voltage regulation capability of LLC converter, adopts fixed frequency PWM control, and does not need to consider the low efficiency and low power density problems caused by wide switching frequency.

[0020] (2) Under the fixed frequency control method, a larger capacity magnetizing inductance can be used to reduce the circulating current in the circuit, which is beneficial to reducing the volume and weight of the resonant inductance and isolation transformer, and improving the power density of the LLC converter.

[0021] (3) The bidirectional sixth switch S6 and the fifth switch S5 on the secondary side have the same control signal as the third switch S3 and the fourth switch S4 on the primary side, and the control is simple.

[0022] (4) Only two additional switches S5 and S6 are needed to realize the adaptive switching of the secondary side rectification structure, and further realize the smooth switching from low output voltage to high output voltage. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the structure principle diagram of the interleaved voltage doubling LLC resonant converter;

[0024] Figure 2 is the equivalent principle diagram of LLC low output voltage;

[0025] Figure 3 is the equivalent principle diagram of LLC high output voltage;

[0026] Figure 4 is the principle diagram of the control pulse when LLC switches from low output voltage to high output voltage;

[0027] Figure 5is a voltage gain versus duty cycle D curve of the LLC;

[0028] Figure 6a is a resonant current versus magnetizing current curve of the LLC at different duty cycles D (a: D = 0);

[0029] Figure 6b is a resonant current versus magnetizing current curve of the LLC at different duty cycles D (b: D = 0.25);

[0030] Figure 6c is a resonant current versus magnetizing current curve of the LLC at different duty cycles D (c: D = 0.5);

[0031] Figure 7 is a converter output voltage curve at a design example. DETAILED DESCRIPTION

[0032] The application will be further described below in conjunction with the drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not intended to limit the scope of the application. After reading the present disclosure, those skilled in the art will be able to affect various modifications to the application. Such equivalents are considered to fall within the scope of the claims appended hereto.

[0033] The proposed interleaved voltage-multiplied wide voltage converter is based on Figure 1 The reconfigurable LLC topology is shown in FIG. 1, which includes an inverter network, a resonant network, a high-frequency transformer set, and a rectifier network.

[0034] The inverter network includes a DC input power source U in , a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4. The first switch S1 and the second switch S2 are connected in series end to end, the drain of the first switch S1 is connected to the positive pole of the DC input power source U in , the source of the first switch S1 is connected to the drain of the second switch S2, and the source of the second switch S2 is connected to the negative pole of the DC input power source U in . The third switch S3 and the fourth switch S4 are connected in series end to end, the drain of the third switch S3 is connected to the positive pole of the DC input power source U in , the source of the third switch S3 is connected to the drain of the fourth switch S4, and the source of the fourth switch S4 is connected to the negative pole of the DC input power source U in .

[0035] The resonant network includes a first resonant capacitor C r1 , a second resonant capacitor C r2 , a first resonant inductor L r1 , and a second resonant inductor L r2, the first excitation inductance L m1 , the second excitation inductance L m2 ; the left end of the first resonance capacitor C r1 is connected to the common end of the series connection of the first switch tube S1 and the second switch tube S2, and the right end is connected in series with the first resonance inductance L r1 , and the two are connected in series with the first excitation inductance L m1 , and the other end of the first excitation inductance L m1 is connected to the source of the second switch tube S2; at the same time, the first excitation inductance L m1 is connected in parallel with the primary side winding of the first high-frequency transformer T1, thereby forming a half-bridge structure on the primary side. The left end of the second resonance capacitor C r2 is connected to the common end of the series connection of the third switch tube S3 and the fourth switch tube S4, and the right end is connected in series with the second resonance inductance L r2 , and the two are connected in series with the second excitation inductance L m2 , and the other end of the second excitation inductance L m2 is connected to the source of the fourth switch tube S4; at the same time, the second excitation inductance L m2 is connected in parallel with the primary side winding of the second high-frequency transformer T2, thereby forming a half-bridge structure on the primary side.

[0036] The rectifier network includes first rectifier diode D1, second rectifier diode D2, third rectifier diode D3, fourth rectifier diode D4, fifth switch tube sixth switch tube first filter capacitor C 01 , second filter capacitor C 02 , equivalent resistive load R0; the fifth switch tube the sixth switch tube together constitute a bidirectional switch, the anode of the first rectifier diode D1 is connected in series with the cathode of the second rectifier diode D2, the anode of the third rectifier diode D3 is connected in series with the cathode of the fourth rectifier diode D4, the cathode of the first rectifier diode D1 is connected to the cathode of the third rectifier diode D3, and the anode of the second rectifier diode D2 is connected to the anode of the fourth rectifier diode D4. The common end of the cathode of the first rectifier diode D1 and the cathode of the third rectifier diode D3 is connected to the anode of the first filter capacitor C 01 , and the common end of the anode of the second rectifier diode D2 and the anode of the fourth rectifier diode D4 is connected to the cathode of the second filter capacitor C 02 ; the negative electrode of the first filter capacitor C 01 is connected in series with the positive electrode of the second filter capacitor C 02 ; the equivalent resistive load R0 is connected in parallel with the two series-connected filter capacitors. The drain of the fifth switch tube is connected to the common end of the anode of the third rectifier diode D3 and the cathode of the fourth rectifier diode D4, and the drain of the fifth switch tube The source is connected to the sixth switch. The source, the sixth switch The drain is connected to the first filter capacitor C. 01 Negative terminal, second filter capacitor C 02 The positive common terminal.

[0037] The high-frequency transformer group includes a first high-frequency transformer T1 and a second high-frequency transformer T2; the positive terminal of the secondary side of the first high-frequency transformer T1 is connected to the common terminal of the first rectifier diode D1 and the second rectifier diode D2, the negative terminal of the secondary side of the first high-frequency transformer T1 is connected in series with the positive terminal of the secondary side of the second high-frequency transformer T2, and the negative terminal of the secondary side of the second high-frequency transformer T2 is connected to the common terminal of the third rectifier diode D3 and the fourth rectifier diode D4.

[0038] During operation, the converter can smoothly switch between low-voltage and high-voltage modes.

[0039] When the converter operates in low-voltage mode, the equivalent circuit of the converter is as follows: Figure 2 As shown. The first switch S1 and the second switch S2 are complementary, conducting with a duty cycle of 0.5. The fourth switch S4 has a duty cycle of 0. The drive signal of the third switch S3 remains stable at a high level within one cycle. The second high-frequency transformer T2 cannot transfer energy to the secondary side, so only one half-bridge is operating on the primary side. The duty cycle of the fifth switch S5 on the secondary side is 0, the bidirectional switch is normally closed, and the rectifier bridge operates constantly in full-bridge rectification mode. At this time, the transformer output voltage is at its lowest, U... 0-min =100V.

[0040] When the converter operates in high-voltage mode, the converter and its downstream circuits, such as Figure 3 As shown. The first switch S1 and the second switch S2 conduct complementaryly with a duty cycle of 0.5, and the third switch S3 and the fourth switch S4 also conduct complementaryly with a duty cycle of 0.5. Furthermore, the first switch S1 and the third switch S3 conduct simultaneously, and the second switch S2 and the fourth switch S4 conduct simultaneously. Both half-bridges on the primary side operate simultaneously. On the secondary side, the sixth bidirectional switch S6 and the fifth switch S5 have the same drive signal as the third switch S3 and the fourth switch S4 on the primary side, respectively. The bidirectional switches are normally open, and the rectifier bridge operates constantly in voltage doubler rectification mode. At this time, the transformer output voltage is at its highest, U... 0-max =380V.

[0041] When the converter output voltage switches from low voltage to high voltage, the converter control signal is as follows: Figure 4The first switch S1 and the second switch S2 are complementarily turned on with a duty ratio of 0.5. The third switch S3 and the fourth switch S4 of the lower half-bridge are complementarily turned on, and the duty ratio of the fourth switch S4 is D, and the regulation range of D is 0-0.5. Meanwhile, the third switch S3 has the same phase as the third switch S1, the fourth switch S4 is turned off at the same time as the second switch S2, the sixth switch S6 and the fifth switch S5 of the secondary side double-direction switch have the same driving signals as the third switch S3 and the fourth switch S4, respectively. Under the control of the control signals, the pulse width of the high level of the input voltage of the resonant tank of the lower half-bridge becomes narrower with the increase of the duty ratio D, the secondary side rectification network works in the mixed rectification mode of full-bridge and voltage doubling, and the output voltage gradually increases.

[0042] As shown in Figure 5 the LLC resonant converter voltage gain and the duty ratio D in the application are shown in the figure. In the low output voltage mode, the minimum voltage gain G of the LLC resonant converter is nU 0-min / U in =0.46, corresponding to the duty ratio D=0; in the high output voltage mode, the minimum voltage gain G of the LLC resonant converter is nU 0-max / U in =1.92, corresponding to the duty ratio D=0.5. With the increase of the duty ratio D, the voltage gain gradually increases, and the corresponding output voltage gradually increases.

[0043] The resonant current i Lr of the two resonant tanks of the converter obtained in the application under different duty ratios D is shown in FIG. 6. Lm The circulating current (the resonant current i Lr and the magnetizing current i Lm overlap) of the converter in the application under different duty ratios is almost 0, so that the circulating current conduction loss in the circuit can be well reduced.

[0044] As shown in Figure 7 the output voltage variation curve of the converter obtained in the application for a design example. The design input voltage is 160V, the resonant frequency is set to 100kHz, the rated output power is 1kW, the resonant capacitance C r1 =C r2 =147nF, the resonant inductance L r1 =L r2 =17.2uH, the magnetizing inductance L m1 =L m2 =172uH, the output filter capacitance C o1 =C O2= 40uF, and the transformer turns ratio n is 0.8. As shown in the figure, the converter of the application realizes smooth switching of the output voltage of the converter from 100V to 380V under the change of the duty cycle D.

[0045] The induced voltage formula of the transformer is:

[0046] E = 4.44nfphi m (1)

[0047] wherein E is the effective value of the induced voltage, f is the working frequency of the transformer, n is the turns, phi is the main magnetic m As can be seen from formula (1), under the same core material and power capacity, the higher the working frequency of the transformer, the smaller the volume and weight.

[0048] The switching frequency of the converter designed in the application is fixed at 100kHz, which is twice the lowest switching frequency of the traditional frequency conversion control LLC resonant converter. Therefore, the volume of the resonant inductor and the isolation transformer of the converter is greatly reduced, and the converter is suitable for occasions with wide output voltage and high power density.

[0049] The specific embodiments described herein are merely illustrative of the spirit of the application. Those skilled in the art of the application can make various modifications or supplements to the described specific embodiments or replace them with similar ways, without deviating from the spirit of the application or exceeding the scope defined by the appended claims.

Claims

1. A control method for an interleaved voltage-width multiplier output LLC resonant converter, characterized in that, The interleaved bandwidth multiplier output LLC resonant converter includes Inverter network: used to invert DC input voltage into square wave voltage; Resonant network: Used for series resonance in circuits, so that the inductive reactance and capacitive reactance in the circuit cancel each other out. At this time, the reactance in the series circuit is 0, and the current and voltage are in phase. High-frequency transformer banks: used for electrical isolation and voltage regulation; Rectifier network: Used to convert the AC output from the secondary side of the transformer into DC. Depending on the control method, it automatically adjusts the working ratio of the full-bridge rectifier and voltage doubler rectifier in one cycle, so that the low output voltage can be smoothly switched to the high output voltage. The inverter network includes a DC input power supply U in The four transistors are: a first switch S1, a second switch S2, a third switch S3, and a fourth switch S4; the first switch S1 and the second switch S2 are connected in series, and the drain of the first switch S1 is connected to the DC input power supply U. in The positive terminal of the first switch S1 is connected to the drain of the second switch S2, and the source of the second switch S2 is connected to the DC input power supply U. in The negative terminal; the third switch S3 and the fourth switch S4 are connected in series, and the drain of the third switch S3 is connected to the DC input power supply U. in The positive terminal of the fourth switch S4 is connected to the source of the third switch S3, and the source of the fourth switch S4 is connected to the DC input power supply U. in The negative electrode; The rectifier network includes a first rectifier diode D1, a second rectifier diode D2, a third rectifier diode D3, a fourth rectifier diode D4, a fifth switch S5, a sixth switch S6, and a first filter capacitor C. O1 Second filter capacitor C O2 The equivalent resistive load is R0; the fifth switch S5 and the sixth switch S6 together form a bidirectional switch; the anode of the first rectifier diode D1 is connected in series with the cathode of the second rectifier diode D2, and the anode of the third rectifier diode D3 is connected in series with the cathode of the fourth rectifier diode D4; the cathode of the first rectifier diode D1 is connected to the cathode of the third rectifier diode D3, and the anode of the second rectifier diode D2 is connected to the anode of the fourth rectifier diode D4; the common terminal of the cathodes of the first rectifier diode D1 and the third rectifier diode D3 is connected to the first filter capacitor C. O1 The positive terminal of the second rectifier diode D2 and the positive terminal of the fourth rectifier diode D4 are connected to the second filter capacitor C. O2 The negative terminal; the first filter capacitor C O1 Negative terminal and second filter capacitor C O2 The positive terminals are connected in series; the equivalent resistive load R0 is connected in parallel with two series-connected filter capacitors; the drain of the fifth switch S5 is connected to the common terminal of the positive terminal of the third rectifier diode D3 and the negative terminal of the fourth rectifier diode D4, the source of the fifth switch S5 is connected to the source of the sixth switch S6, and the drain of the sixth switch S6 is connected to the first filter capacitor C. O1 Negative terminal, second filter capacitor C O2 The positive common terminal; The control method of the interleaved voltage-doubling output LLC resonant converter adopts fixed-frequency pulse width (PWM) control. The first switch S1 and the second switch S2 are complementaryly turned on with a duty cycle of 0.

5. The third switch S3 and the fourth switch S4 of the lower half-bridge are complementaryly turned on. The duty cycle of the fourth switch S4 is D, and the adjustment range of D is 0 to 0.

5. At the same time, the third switch S3 and the third switch S1 are in phase, and the fourth switch S4 and the second switch S2 are turned off at the same time. The sixth switch S6 and the fifth switch S5 of the secondary side bidirectional switches have the same drive signal as the third switch S3 and the fourth switch S4, respectively. The switching frequency is fixed and equal to the resonant frequency. By changing the working time of the fourth switch S4 of the primary side in one cycle, the primary side is changed from being connected to the upper half-bridge alone to being connected to both the upper and lower half-bridges to achieve a 2x voltage gain adjustment. With the control of the bidirectional switches, the secondary side adaptive rectification is realized. The rectification network is changed from full-bridge rectification to voltage-doubling rectification, thereby realizing a 4x wide output voltage adjustment range. When switching from low output voltage to high output voltage, the duty cycle D of the fourth switch S4 on the primary side is changed within one cycle, 0≤D≤0.5, so that the primary side gradually changes from connecting one half-bridge to connecting two half-bridges. At the same time, under the action of the bidirectional switches S5 and S6, the secondary side rectifier network automatically adjusts the working ratio of full-bridge rectification and voltage doubler rectification within one cycle, and the rectification mode gradually transitions from full-bridge rectification to voltage doubler rectification. During this period, the two rectification modes of full-bridge and voltage doubler coexist and work in combination. Without changing the switching frequency, a smooth switching from low output voltage to high output voltage can be achieved by only changing the duty cycle.

2. The control method for an interleaved voltage-width multiplier output LLC resonant converter according to claim 1, characterized in that, The resonant network includes a first resonant capacitor C. r1 Second resonant capacitor C r2 First resonant inductor L r1 Second resonant inductor L r2 First excitation inductor L m1 Second excitation inductor L m2 The first resonant capacitor C r1 The left end is connected to the common terminal of the series connection of the first switch S1 and the second switch S2, and the right end is connected to the first resonant inductor L. r1 The two are connected in series, and then connected to the first magnetizing inductor L. m1 Series connection, first magnetizing inductor L m1 The other end is connected to the source of the second switch S2; simultaneously, the first magnetizing inductor L m1 It is connected in parallel with the primary winding of the first high-frequency transformer T1, thus forming the upper half-bridge structure on the primary side; the second resonant capacitor C r2 The left end is connected to the common terminal of the series connection of the third switch S3 and the fourth switch S4, and the right end is connected to the second resonant inductor L. r2 The two are connected in series, and then connected to the second magnetizing inductor L. m2 Series connection, second magnetizing inductor L m2 The other end is connected to the source of the fourth switch S4; simultaneously, the second magnetizing inductor L m2 It is connected in parallel with the primary winding of the second high-frequency transformer T2 to form the primary side lower half-bridge structure.

3. The control method for an interleaved voltage-width multiplier output LLC resonant converter according to claim 1, characterized in that, The high-frequency transformer group includes a first high-frequency transformer T1 and a second high-frequency transformer T2; the positive terminal of the secondary side of the first high-frequency transformer T1 is connected to the common terminal of the first rectifier diode D1 and the second rectifier diode D2, the negative terminal of the secondary side of the first high-frequency transformer T1 is connected in series with the positive terminal of the secondary side of the second high-frequency transformer T2, and the negative terminal of the secondary side of the second high-frequency transformer T2 is connected to the common terminal of the third rectifier diode D3 and the fourth rectifier diode D4.

4. The control method according to claim 1, characterized in that, When only the upper half-bridge is connected on the primary side, the converter operates in low-voltage mode. At this time, the first switch S1 and the second switch S2 are complementary and conduct with a duty cycle of 0.

5. The lower half-bridge does not transfer energy to the load. The fifth switch S5 and the sixth switch S6 on the secondary side are disconnected and do not work. The rectifier network operates in full-bridge mode. At this time, the converter is equivalent to a half-bridge LLC resonant converter, and the corresponding output voltage is the lowest.

5. The control method according to claim 1, characterized in that, When two half-bridges are connected to the primary side, the converter operates in high-voltage mode. At this time, the first switch S1 and the second switch S2 are complementaryly turned on with a duty cycle of 0.5, and the third switch S3 and the fourth switch S4 are complementaryly turned on with a duty cycle of 0.

5. The corresponding bidirectional switch on the secondary side is continuously turned on, and the rectifier network operates in voltage doubler rectification mode. At this time, the primary and secondary sides of the converter each achieve a voltage regulation range of 2 times, corresponding to the highest output voltage.

Images