A staggered parallel LLC DC-DC resonant converter and current balancing method thereof

Abstract

The present invention discloses a staggered parallel LLCC-DC resonant converter and a current balancing method thereof, wherein the output current information of the first phase, the output current information of the second phase and the output voltage information are input into a digital controller through a sampling module and then through a digital-to-analog conversion module, and the error signal is compensated and adjusted by a voltage loop control unit with compensation, and finally a PWM generator outputs a modulated PWM wave with a certain duty cycle as a gate signal to control the action of the Buck bridge arm. By setting the current bus, the current error signal is in a dynamic balance process during the current balancing process, which has more flexibility than using the current constant as a reference value. By collecting the output current information of the two phases, and selecting the current information with a large current as the bus, and then using the two currents to make a difference with the current bus, the error signal is obtained and then proportionally amplified and added to the voltage reference, and finally the duty cycle of the Buck circuit is adjusted to achieve the current balancing effect.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronics, and in particular relates to an interleaved parallel LLC DC-DC resonant converter and a current balancing method thereof. Background Art

[0002] With the continuous development of power electronics technology, high power density DC-DC power modules are widely used in electric vehicles, communication engineering, data centers, aerospace and other fields. At present, with the development of the information society, the importance of data centers is becoming increasingly prominent, so there is a greater demand for DC / DC converters with low voltage and high current output.

[0003] Compared with other DC / DC converters, LLC resonant converters have the advantages of soft switching characteristics, simple structure, high efficiency and easy to achieve high power density. However, for applications with large current output, there are problems such as excessive current ripple and excessive volume of magnetic components. In order to solve the above problems, the interleaved parallel technology is introduced. The use of interleaved parallel technology can effectively reduce the output current ripple, thereby reducing the output capacitor capacitance to reduce the output capacitor volume, and at the same time can reduce the current effective value to reduce the volume of magnetic components. However, due to process limitations, the component parameters between the interleaved parallel LLC resonant converters cannot be exactly the same, which will result in different equivalent impedances of the resonant cavity and different DC gains of the converter at the same switching frequency, resulting in uneven current. The uneven current problem of the interleaved parallel LLC resonant converter will result in uneven losses of components such as switch tubes and capacitors, which will reduce the life and stability reliability of the switching power supply. Therefore, there is a need for a method to solve the uneven current problem of the interleaved parallel LLC resonant converter. Summary of the invention

[0004] In view of the above problems, an embodiment of the present invention provides an interleaved parallel LLC DC-DC resonant converter and a current balancing method thereof.

[0005] The technical solution of the present invention is as follows:

[0006] A staggered parallel LLC DC-DC resonant converter adopts full-bridge rectification on the basis of a circuit topology in which a center tap is adopted on the secondary side of the staggered parallel LLC resonant converter, and two discrete capacitors are used for filtering, and then a BUCK circuit is connected to the rear stage of one of the capacitors. The staggered parallel LLC resonant converter main circuit comprises a DC input power supply, a first-phase high-frequency upper tube GaN HEMT switch tube Q11, a first-phase high-frequency lower tube GaN HEMT switch tube Q12, a first-phase high-frequency transformer T1, a first-phase secondary side low on-resistance SiC rectifier bridge arm upper tube S11, a first-phase secondary side low on-resistance SiC rectifier bridge arm upper tube S13, a first-phase resonant inductor L r1, the first phase resonant capacitor C r1 , the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S12, the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S14, the first phase Buck bus capacitor C o11 , the first phase LLC power filter capacitor C o12 、First phase Buck supervisor S buck11 、The first phase Buck freewheeling tube S buck12 、First phase Buck inductor L buck1 , the second phase high frequency upper tube GaN HEMT switch tube Q21, the second phase high frequency lower tube GaN HEMT switch tube Q22, the second phase high frequency transformer T2, the second phase secondary side low on-resistance SiC rectifier bridge arm upper tube S21, the second phase secondary side low on-resistance SiC rectifier bridge arm upper tube S23, the second phase secondary side low on-resistance SiC rectifier bridge arm lower tube S22, the second phase secondary side low on-resistance SiC rectifier bridge arm lower tube S24, the second phase resonant inductor L r2 , the second phase resonant capacitor C r2 、Second phase Buck bus capacitor C o21 , the second phase LLC power filter capacitor C o22 、Second phase Buck supervisor S buck21 、The second phase Buck freewheeling tube S buck22 、Second phase Buck inductor L buck2 , the output capacitor C shared by the two phases o and output load R Load The digital control module used includes a two-phase staggered parallel output voltage sampling module, a first-phase Buck buck inductor current sampling module, a second-phase Buck buck inductor current sampling module, a first-phase voltage loop PI controller, a square wave generation module, a first-phase PWM output module, a current comparison module, a current bus module, a first-phase low-pass filter, a second-phase low-pass filter, a second-phase PWM output module, a second-phase voltage loop PI controller, a square wave phase shift module, a first-phase voltage compensation ratio link, a second-phase voltage compensation ratio link, a first-phase difference module, and a second-phase difference module. The output voltage sampling module is used to collect the output voltage; the first-phase Buck buck inductor current sampling module is used to collect the first-phase Buck buck inductor current to implement the current sharing strategy; the second-phase Buck buck inductor current sampling module is used to collect the second-phase Buck buck inductor current to implement the current sharing strategy; the first-phase voltage loop PI controller is used to adjust the error information I between the output voltage and the reference voltage compensated by the first-phase current sharing link err1 The second phase voltage loop PI controller is used to adjust the error information I between the output voltage and the reference voltage compensated by the second phase current sharing link err2; The first-phase voltage compensation ratio link is used to calculate the difference between the first-phase inductor current and the current-sharing bus to compensate for the reference voltage; the second-phase voltage compensation ratio link is used to calculate the difference between the second-phase inductor current and the current-sharing bus to compensate for the reference voltage; the first-phase low-pass filter is used to filter out the high-frequency ripple of the first-phase Buck inductor current to obtain the DC component of the inductor current; the second-phase low-pass filter is used to filter out the high-frequency ripple of the first-phase Buck inductor current to obtain the DC component of the inductor current; the square wave generation module and the square wave phase shift module are used to generate a square wave slightly lower than the resonant frequency to drive the signal of the LLC primary switch tube.

[0007] Preferably, the positive electrode of the DC input power supply is connected to the D end of the first phase high-frequency upper tube GaN HEMT switch tube Q11; the S end of the high-frequency upper tube GaN HEMT switch tube Q11 is connected to the D end of the first phase high-frequency lower tube GaN HEMT switch tube Q12, the first phase resonant inductor L r1 One end of the resonant inductor and the other end of the first phase resonant capacitor C r1 The other end of the resonant capacitor is connected to the same-name terminal of the primary side of the first-phase high-frequency transformer T1, and the opposite-name terminal of the primary side of the high-frequency transformer T1 is connected to the S-terminal of the first-phase high-frequency lower tube GaN HEMT switch tube Q12 and the negative electrode of the DC input power supply. The same-name terminal of the secondary side of the transformer is connected to the S-terminal of the first-phase secondary side low-on-resistance SiC rectifier bridge arm upper tube S11, the D-terminal of the first-phase secondary side low-on-resistance SiC rectifier bridge arm lower tube S12, the D-terminal of the first-phase secondary side low-on-resistance SiC rectifier bridge arm upper tube S11, the D-terminal of the first-phase secondary side low-on-resistance SiC rectifier bridge arm upper tube S13, the first-phase Buck bus capacitor C o11 One end, the first phase Buck supervisor S buck11 The D terminal is connected to the bus capacitor C o11 The other end is connected to the center tap of high-frequency transformer T1 and the power filter capacitor C of the first phase LLC part. o12 One end of the first phase Buck freewheeling tube S buck12 The S end of the first phase secondary low on-resistance SiC rectifier bridge arm upper tube S13 is connected to the D end of the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S14 and the opposite end of the high-frequency transformer T1, and the S end of the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S12 is connected to the S end of the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S14 and the first phase LLC part power filter capacitor C o12 One end is connected to the first phase Buck supervisor S buck11 The S end of the first phase Buck freewheeling tube S buck12 The D terminal, the first phase Buck step-down inductor L buck1 One end of the two-phase common output capacitor C oOne end of the output load R Load One end of the output load R Load The other section is shared by the two phases with the output capacitor C o One end of the first phase LLC power filter capacitor C o12 The positive electrode of the DC input power supply is connected to the D end of the second-phase high-frequency upper tube GaN HEMT switch tube Q21; the S end of the high-frequency upper tube GaN HEMT switch tube Q21 is connected to the D end of the second-phase high-frequency lower tube GaN HEMT switch tube Q22, the second-phase resonant inductor L r2 One end of the resonant inductor, the other end of the second phase resonant capacitor C r2 The other end of the resonant capacitor is connected to the same-name terminal of the primary side of the second-phase high-frequency transformer T2, and the opposite-name terminal of the primary side of the high-frequency transformer T1 is connected to the S-terminal of the second-phase high-frequency lower tube GaN HEMT switch tube Q22 and the negative electrode of the DC input power supply. The same-name terminal of the secondary side of the transformer is connected to the S-terminal of the second-phase secondary side low-on-resistance SiC rectifier bridge arm upper tube S21, the D-terminal of the second-phase secondary side low-on-resistance SiC rectifier bridge arm lower tube S22, the D-terminal of the second-phase secondary side low-on-resistance SiC rectifier bridge arm upper tube S21, the D-terminal of the second-phase secondary side low-on-resistance SiC rectifier bridge arm upper tube S23, the second-phase Buck bus capacitor C o21 One end of the second phase Buck supervisor S buck21 The D terminal is connected to the bus capacitor C o21 The other end is connected to the center tap of high-frequency transformer T1 and the power filter capacitor C of the second-phase LLC part. o22 One end of the second phase Buck freewheeling tube S buck22 The S end of the second-phase secondary low on-resistance SiC rectifier bridge arm upper tube S23 is connected to the D end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube S24 and the opposite end of the high-frequency transformer T1, and the S end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube S22 is connected to the S end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube S24 and the second-phase LLC part power filter capacitor C o22 One end is connected to the second phase Buck supervisor S buck21 The S end of the second phase Buck freewheeling tube S buck22 The D terminal and the second phase Buck step-down inductor L buck2 One end of the two-phase common output capacitor C o One end of the output load R Load One end of the output load R Load The other section is shared by the two phases with the output capacitor Co One end of the second phase LLC power filter capacitor C o22 The first output end of the first-phase Buck buck inductor current sampling module is connected to the input end of the first-phase low-pass filter, the first output end of the second-phase Buck buck inductor current sampling module is connected to the input end of the second-phase low-pass filter, the output end of the first-phase low-pass filter is connected to the first input end of the current comparison module, the first input end of the first-phase difference module, and the first input end of the current bus module, and the output end of the second-phase low-pass filter is connected to the second input terminal of the current comparison module, the second input terminal of the current bus module, the second input terminal of the second phase difference module, the first output terminal of the current bus module is connected to the second input terminal of the first phase difference module, the second output terminal of the current bus module is connected to the first input terminal of the second phase difference module, the first output terminal of the first phase difference module is connected to the input terminal of the first phase voltage compensation ratio link, the first output terminal of the second phase difference module is connected to the first input terminal of the second phase voltage compensation ratio link, the first output terminal of the first phase voltage compensation ratio link, the first output terminal of the output voltage sampling module, the reference voltage V ref connected to the first adder, the first output end of the second phase voltage compensation ratio link, the first output end of the output voltage sampling module, the reference voltage V ref The output end of the first adder is connected to the first phase voltage loop PI controller, the output end of the second adder is connected to the second phase voltage loop PI controller, the output end of the first phase voltage loop PI controller is connected to the input end of the first phase PWM output module, the output end of the second phase voltage loop PI controller is connected to the input end of the second phase PWM output module, the output end of the first phase PWM output module is used to drive the Buck circuit bridge arm of the first phase in the interleaved parallel LLC circuit topology, and the output end of the second phase PWM output module is used to drive the Buck circuit bridge arm of the second phase in the interleaved parallel LLC circuit topology.

[0008] Another aspect of an embodiment of the present invention provides a current sharing strategy for an interleaved parallel LLC DC-DC resonant converter, using an interleaved parallel LLC DC-DC resonant converter as described above, comprising the following steps:

[0009] S1, collects the first phase output current I of the interleaved parallel LLC o1 , the second phase output current I o2 will pass through the low-pass filter, and I o2 with I o1 Compare and get the current value with larger current as bus current;

[0010] S2, respectively, subtract I from the current bus o2 with I o1 The difference between each phase and the current bus is obtained, and then the current sharing compensation is added to the reference voltage V through the proportional link. ref superior;

[0011] S3, collects the output voltage V of the interleaved parallel LLC o , and the output voltage V o With the set output voltage V ref The voltage error signals of the two phases are obtained by subtracting the sum of the sum of the first phase current sharing compensation link and the second phase current sharing compensation link, and then the obtained error signals are input into the voltage loop PI controller of the two phases;

[0012] S4, the output duty ratios d1 and d2 of the two-phase voltage loop PI controller are then compared with the carrier with a phase difference of 180°, and the final output duty ratio is d1 real , d2 real The PWM wave is used to drive the Buck tube and freewheeling tube of each phase of the interleaved parallel LLC resonant converter;

[0013] S5, 100K open loop square wave signal V square Drive LLC high frequency half-bridge GaN HEMT switch tube.

[0014] Preferably, the structure of the two diodes on the secondary side of the traditional LLC is changed to a full-bridge structure, two bus capacitors are used, a post-stage Buck circuit is used, and the gain of the Buck circuit is used to compensate for the LLC current unevenness problem caused by parameter differences.

[0015] Preferably, the current difference is automatically balanced using a current bus.

[0016] Preferably, current compensation is used to influence the duty cycle.

[0017] Through the staggered parallel LLC DC-DC resonant converter and its current balancing method implemented above, the output current information of the first phase, the output current information of the second phase and the output voltage information are input into the digital controller through the sampling module and then through the digital-to-analog conversion module, the error signal is compensated and adjusted by the voltage loop control unit with compensation, and finally the PWM generator outputs a PWM wave with a certain duty cycle modulated as a gate signal to control the action of the Buck bridge arm. The present invention sets the current bus method so that the current error signal is in a dynamic balance process during the current balancing process, which has more flexibility than using the current constant as a reference value. By collecting the output current information of the two phases, and selecting the current information with a large current as the bus, and then using the two currents and the current bus to make a difference, the error signal is obtained and then proportionally amplified and added to the voltage reference, and finally the duty cycle of the Buck circuit is adjusted to achieve the current balancing effect. Through topological improvements and control strategies, the good current balancing effect of the staggered parallel LLC is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The main topology structure diagram of an interleaved parallel LLC DC-DC resonant converter according to an embodiment of the present invention is shown in FIG.

[0019] Figure 2 The figure is a schematic diagram of a control strategy for an interleaved parallel LLC DC-DC resonant converter according to an embodiment of the present invention.

[0020] Figure 3 The present invention provides a resonant inductor current waveform of an interleaved parallel LLC DC-DC resonant converter under the control method provided by the present invention.

[0021] Figure 4 The Buck step-down inductor current waveform of the interleaved parallel LLC DC-DC resonant converter under the control method provided by the present invention. DETAILED DESCRIPTION

[0022] join Figure 1 , which is a schematic diagram of the structure of an interleaved parallel LLC DC-DC resonant converter according to an embodiment of the present invention, adopts full-bridge rectification on the basis of the circuit topology of the center tap on the secondary side of the LLC transformer, and uses two discrete capacitors for filtering, and then connects a BUCK circuit to the rear stage of one of the capacitors. The main circuit of the interleaved parallel LLC resonant converter includes a DC input power supply, a first-phase high-frequency upper tube GaN HEMT switch tube Q11, a first-phase high-frequency lower tube GaN HEMT switch tube Q12, a first-phase high-frequency transformer T1, a first-phase secondary side low on-resistance SiC rectifier bridge arm upper tube S11, a first-phase secondary side low on-resistance SiC rectifier bridge arm upper tube S13, and a first-phase resonant inductor L r1, the first phase resonant capacitor C r1 , the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S12, the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S14, the first phase Buck bus capacitor C o11 , the first phase LLC power filter capacitor C o12 、First phase Buck supervisor S buck11 、The first phase Buck freewheeling tube S buck12 、First phase Buck inductor L buck1 , the second phase high frequency upper tube GaN HEMT switch tube Q21, the second phase high frequency lower tube GaN HEMT switch tube Q22, the second phase high frequency transformer T2, the second phase secondary side low on-resistance SiC rectifier bridge arm upper tube S21, the second phase secondary side low on-resistance SiC rectifier bridge arm upper tube S23, the second phase secondary side low on-resistance SiC rectifier bridge arm lower tube S22, the second phase secondary side low on-resistance SiC rectifier bridge arm lower tube S24, the second phase resonant inductor L r2 , the second phase resonant capacitor C r2 、Second phase Buck bus capacitor C o21 , the second phase LLC power filter capacitor C o22 、Second phase Buck supervisor S buck21 、The second phase Buck freewheeling tube S buck22 、Second phase Buck inductor L buck2 , the output capacitor C shared by the two phases o and output load R Load , continue to see Figure 2 The digital control module used includes a two-phase staggered parallel output voltage sampling module 1, a first-phase Buck buck inductor current sampling module 2, a second-phase Buck buck inductor current sampling module 3, a first-phase voltage loop PI controller 4, a square wave generation module 5, a first-phase PWM output module 6, a current comparison module 7, a current bus module 8, a first-phase low-pass filter 9, a second-phase low-pass filter 10, a second-phase PWM output module 11, a second-phase voltage loop PI controller 12, a square wave phase shift module 13, a first-phase voltage compensation ratio link 14, a second-phase voltage compensation ratio link 15, a first-phase difference module 16, and a second-phase difference module 17. The output voltage sampling module 1 is used to collect the output voltage; the first-phase Buck buck inductor current sampling module 2 is used to collect the first-phase Buck buck inductor current to perform a current sharing strategy; the second-phase Buck buck inductor current sampling module 3 is used to collect the second-phase Buck buck inductor current to perform a current sharing strategy; the first-phase voltage loop PI controller 4 is used to adjust the error information I between the output voltage and the reference voltage compensated by the first-phase current sharing link err1The second phase voltage loop PI controller 12 is used to adjust the error information I between the output voltage and the reference voltage compensated by the second phase current sharing link err2 ; The first phase voltage compensation ratio link 14 is used to calculate the difference between the first phase inductor current and the current sharing bus to compensate the reference voltage; the second phase voltage compensation ratio link 15 is used to calculate the difference between the second phase inductor current and the current sharing bus to compensate the reference voltage; the first phase low-pass filter 9 is used to filter out the high-frequency ripple of the first phase Buck inductor current to obtain the DC component of the inductor current; the second phase low-pass filter 10 is used to filter out the high-frequency ripple of the first phase Buck inductor current to obtain the DC component of the inductor current; the square wave generation module 5 and the square wave phase shift module 13 are used to generate a square wave slightly lower than the resonant frequency to drive the signal of the LLC primary switch tube.

[0023] Furthermore, the positive electrode of the DC input power supply is connected to the D end of the first phase high frequency upper tube GaN HEMT switch tube Q11; the S end of the high frequency upper tube GaN HEMT switch tube Q11 is connected to the D end of the first phase high frequency lower tube GaN HEMT switch tube Q12, the first phase resonant inductor L r1 One end of the resonant inductor and the other end of the first phase resonant capacitor C r1 The other end of the resonant capacitor is connected to the same-name terminal of the primary side of the first-phase high-frequency transformer T1, and the opposite-name terminal of the primary side of the high-frequency transformer T1 is connected to the S-terminal of the first-phase high-frequency lower-tube GaN HEMT switch tube Q12 and the negative pole of the DC input power supply. The same-name terminal of the secondary side of the transformer is connected to the S-terminal of the first-phase secondary-side low-on-resistance SiC rectifier bridge arm upper tube S11, the D-terminal of the first-phase secondary-side low-on-resistance SiC rectifier bridge arm lower tube S12, the D-terminal of the first-phase secondary-side low-on-resistance SiC rectifier bridge arm upper tube S11, the D-terminal of the first-phase secondary-side low-on-resistance SiC rectifier bridge arm upper tube S13, and the first-phase Buck bus capacitor C o11 One end, the first phase Buck supervisor S buck11 The D terminal is connected to the bus capacitor C o11 The other end is connected to the center tap of high-frequency transformer T1 and the power filter capacitor C of the first phase LLC part. o12 One end of the first phase Buck freewheeling tube S buck12 The S end of the first phase secondary low on-resistance SiC rectifier bridge arm upper tube S13 is connected to the D end of the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S14 and the opposite end of the high-frequency transformer T1, and the S end of the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S12 is connected to the S end of the first phase secondary low on-resistance SiC rectifier bridge arm lower tube S14 and the first phase LLC part power filter capacitor C o12 One end is connected to the first phase Buck supervisor S buck11 The S end of the first phase Buck freewheeling tube Sbuck12 The D terminal, the first phase Buck step-down inductor L buck1 One end of the two-phase common output capacitor C o One end of the output load R Load One end connected to the output load R Load The other section is shared by the two phases with the output capacitor C o One end of the first phase LLC power filter capacitor C o12 The positive pole of the DC input power supply is connected to the D end of the second-phase high-frequency upper tube GaN HEMT switch tube Q21; the S end of the high-frequency upper tube GaN HEMT switch tube Q21 is connected to the D end of the second-phase high-frequency lower tube GaN HEMT switch tube Q22, the second-phase resonant inductor L r2 One end of the resonant inductor, the other end of the second phase resonant capacitor C r2 The other end of the resonant capacitor is connected to the same-name terminal of the primary side of the second-phase high-frequency transformer T2, and the opposite-name terminal of the primary side of the high-frequency transformer T1 is connected to the S-terminal of the second-phase high-frequency lower-tube GaN HEMT switch tube Q22 and the negative pole of the DC input power supply. The same-name terminal of the secondary side of the transformer is connected to the S-terminal of the second-phase secondary low-on-resistance SiC rectifier bridge arm upper tube S21, the D-terminal of the second-phase secondary low-on-resistance SiC rectifier bridge arm lower tube S22, the D-terminal of the second-phase secondary low-on-resistance SiC rectifier bridge arm upper tube S21, the D-terminal of the second-phase secondary low-on-resistance SiC rectifier bridge arm upper tube S23, the second-phase Buck bus capacitor C o21 One end of the second phase Buck supervisor S buck21 The D terminal is connected to the bus capacitor C o21 The other end is connected to the center tap of high-frequency transformer T1 and the power filter capacitor C of the second-phase LLC part. o22 One end of the second phase Buck freewheeling tube S buck22 The S end of the second-phase secondary low on-resistance SiC rectifier bridge arm upper tube S23 is connected to the D end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube S24 and the opposite end of the high-frequency transformer T1, and the S end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube S22 is connected to the S end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube S24 and the second-phase LLC part power filter capacitor C o22 One end is connected to the second phase Buck supervisor S buck21 The S end of the second phase Buck freewheeling tube S buck22 The D terminal and the second phase Buck step-down inductor L buck2 One end of the two-phase common output capacitor C o One end of the output load RLoad One end of the output load R Load The other section is shared by the two phases with the output capacitor C o One end of the second phase LLC power filter capacitor C o22 The first output end of the first-phase Buck buck inductor current sampling module 2 is connected to the input end of the first-phase low-pass filter 9, the first output end of the second-phase Buck buck inductor current sampling module 3 is connected to the input end of the second-phase low-pass filter 10, the output end of the first-phase low-pass filter 9 is connected to the first input end of the current comparison module 7, the first input end of the first-phase difference module 16, and the first input end of the current bus module 8, and the output end of the second-phase low-pass filter 10 is connected to the current comparison module 7. The second input end of the module 7, the second input end of the current bus module 8, the second input end of the second phase difference module 17, the first output end of the current bus module 8 is connected to the second input end of the first phase difference module 16, the second output end of the current bus module 8 is connected to the first input end of the second phase difference module 17, the first output end of the first phase difference module 16 is connected to the input end of the first phase voltage compensation ratio link 14, the first output end of the second phase difference module 17 is connected to the first input end of the second phase voltage compensation ratio link 15, the first output end of the first phase voltage compensation ratio link 14, the first output end of the output voltage sampling module 1, the reference voltage V ref connected to the first adder, the first output end of the second phase voltage compensation ratio link 15, the first output end of the output voltage sampling module 1, the reference voltage V ref It is connected to the second adder, the output end of the first adder is connected to the first phase voltage loop PI controller 4, the output end of the second adder is connected to the second phase voltage loop PI controller 12, the output end of the first phase voltage loop PI controller 4 is connected to the input end of the first phase PWM output module 6, the output end of the second phase voltage loop PI controller 12 is connected to the input end of the second phase PWM output module 11, the output end of the first phase PWM output module 6 is used to drive the Buck circuit bridge arm of the first phase in the interleaved parallel LLC circuit topology, and the output end of the second phase PWM output module 11 is used to drive the Buck circuit bridge arm of the second phase in the interleaved parallel LLC circuit topology.

[0024] Another embodiment of the present invention provides a current balancing method for an interleaved parallel LLC DC-DC resonant converter, using the interleaved parallel LLC DC-DC resonant converter as described above, comprising the following steps:

[0025] S1, collects the first phase output current I of the interleaved parallel LLC o1, the second phase output current I o2 will pass through the low-pass filter, and I o2 with I o1 By comparison, the current value with a larger current is taken as the bus current.

[0026] S2, respectively, subtract I from the current bus o2 with I o1 The difference between each phase and the current bus is obtained, and then the current sharing compensation is added to the reference voltage V through the proportional link. ref superior.

[0027] S3, collects the output voltage V of the interleaved parallel LLC o , and the output voltage V o With the set output voltage V ref The voltage error signals of the two phases are obtained by subtracting the sum of the sum of the first phase current sharing compensation link and the second phase current sharing compensation link, and then the obtained error signals are input into the voltage loop PI controller of the two phases.

[0028] S4, the output duty cycles d1 and d2 of the two-phase voltage loop PI controller are then compared with the carrier with a phase difference of 180°, and the final PWM waves with duty cycles of d1real and d2real are output to drive the Buck main tube and freewheeling tube of each phase of the staggered parallel LLC resonant converter.

[0029] S5, 100K open-loop square wave signal Vsquare drives the LLC high-frequency half-bridge GaN HEMT switch tube.

[0030] Furthermore, a current equalization method for an interleaved parallel LLC DC-DC resonant converter in an embodiment of the present invention changes the structure of the two diodes on the secondary side of the traditional LLC into a full-bridge structure, adopts two bus capacitors, uses a post-stage connected Buck circuit, and uses the gain of the Buck circuit to compensate for the LLC current unevenness problem caused by parameter differences.

[0031] Furthermore, a current balancing method for interleaved parallel LLC DC-DC resonant converters in an embodiment of the present invention uses a current bus to automatically balance the current difference.

[0032] Furthermore, a current sharing method for interleaved parallel LLC DC-DC resonant converters in an embodiment of the present invention uses current compensation to influence the duty cycle.

[0033] In order to verify the effectiveness of the strategy described in the present invention, the present invention is first applied to the staggered parallel LLC resonant converter. The waveforms using the current sharing topology and strategy are as follows: Figure 3As shown in the figure, I1 represents the resonant current waveform of the first phase LLC resonant converter, and I2 represents the resonant current waveform of the second phase LLC resonant converter. By comparing the amplitudes of the two currents, it can be seen that the current sharing effect is good. The two-phase Buck step-down inductor current waveform using the control method proposed by the present invention is as follows: Figure 4 As shown, IL1 represents the first-phase Buck step-down inductor current, and IL2 represents the first-phase Buck step-down inductor current. It can be seen that this control method can also solve the current unevenness problem well.

[0034] It should be understood that the exemplary embodiments described herein are illustrative rather than restrictive. Although one or more embodiments of the present invention have been described in conjunction with the accompanying drawings, it should be understood by those skilled in the art that various changes in form and detail may be made without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. An interleaved parallel LLC DC-DC resonant converter, characterized in that: The invention adopts full-bridge rectification on the basis of the circuit topology of center tap on the secondary side of the interleaved parallel LLC resonant converter, and uses two discrete capacitors for filtering, and then connects a BUCK circuit to the rear stage of one of the capacitors. The main circuit of the interleaved parallel LLC resonant converter includes a DC input power supply, a first-phase high-frequency upper tube GaN HEMT switch tube (Q11), a first-phase high-frequency lower tube GaN HEMT switch tube (Q12), a first-phase high-frequency transformer (T1), a first-phase secondary side low on-resistance SiC rectifier bridge arm upper tube (S11), a first-phase secondary side low on-resistance SiC rectifier bridge arm upper tube (S13), a first-phase resonant inductor (L r1 ), the first phase resonant capacitor (C r1 ), the first phase secondary side low on-resistance SiC rectifier bridge arm lower tube (S12), the first phase secondary side low on-resistance SiC rectifier bridge arm lower tube (S14), the first phase Buck bus capacitor (C o11 ), the first phase LLC power filter capacitor (C o12 ), the first phase Buck supervisor (S buck11 ), the first phase Buck freewheeling tube (S buck12 ), the first phase Buck inductor (L buck1 ), the second phase high frequency upper tube GaN HEMT switch tube (Q21), the second phase high frequency lower tube GaN HEMT switch tube (Q22), the second phase high frequency transformer (T2), the second phase secondary side low on-resistance SiC rectifier bridge arm upper tube (S21), the second phase secondary side low on-resistance SiC rectifier bridge arm upper tube (S23), the second phase secondary side low on-resistance SiC rectifier bridge arm lower tube (S22), the second phase secondary side low on-resistance SiC rectifier bridge arm lower tube (S24), the second phase resonant inductor (L r2 ), the second phase resonant capacitor (C r2 ), the second phase Buck bus capacitor (C o21 ), the second phase LLC power filter capacitor (C o22 ), the second phase Buck supervisor (S buck21 ), the second phase Buck freewheeling tube (S buck22 ), the second phase Buck inductor (L buck2 ), the output capacitor shared by the two phases (C o ) and output load (R Load ), the digital control module used includes a two-phase staggered parallel output voltage sampling module (1), a first-phase Buck buck inductor current sampling module (2), a second-phase Buck buck inductor current sampling module (3), a first-phase voltage loop PI controller (4), a square wave generating module (5), a first-phase PWM output module (6), a current comparison module (7), a current bus module (8), a first-phase low-pass filter (9), a second-phase low-pass filter (10), a second-phase PWM output module (11), a second-phase voltage loop PI controller (12), a square wave phase shifting module (13), a first-phase voltage The compensation ratio link (14), the second phase voltage compensation ratio link (15), the first phase difference obtaining module (16), the second phase difference obtaining module (17), the output voltage sampling module (1) is used to collect the output voltage; the first phase Buck buck inductor current sampling module (2) is used to collect the first phase Buck buck inductor current to implement the current sharing strategy; the second phase Buck buck inductor current sampling module (3) is used to collect the second phase Buck buck inductor current to implement the current sharing strategy; the first phase voltage loop PI controller (4) is used to adjust the error information I between the output voltage and the reference voltage compensated by the first phase current sharing link err1 The second phase voltage loop PI controller (12) is used to adjust the error information I between the output voltage and the reference voltage compensated by the second phase current sharing link err2 The first phase voltage compensation ratio link (14) is used to calculate the difference between the first phase inductor current and the current sharing bus to compensate for the reference voltage; the second phase voltage compensation ratio link (15) is used to calculate the difference between the second phase inductor current and the current sharing bus to compensate for the reference voltage; the first phase low-pass filter (9) is used to filter out the high-frequency ripple of the first phase Buck inductor current to obtain the DC component of the inductor current; the second phase low-pass filter (10) is used to filter out the high-frequency ripple of the first phase Buck inductor current to obtain the DC component of the inductor current; the square wave generation module (5) and the square wave phase shift module (13) are used to generate a square wave slightly lower than the resonant frequency to drive the signal of the LLC primary switch tube.

2. The interleaved parallel LLC DC-DC resonant converter according to claim 1, characterized in that: The positive electrode of the DC input power supply is connected to the D end of the first phase high frequency upper tube GaN HEMT switch tube (Q11); the S end of the high frequency upper tube GaN HEMT switch tube (Q11) is connected to the D end of the first phase high frequency lower tube GaN HEMT switch tube (Q12), the first phase resonant inductor (L r1 ) one end, the other end of the resonant inductor and the first phase resonant capacitor (C r1 ), the other end of the resonant capacitor is connected to the primary same-name end of the first-phase high-frequency transformer (T1), the primary opposite-name end of the high-frequency transformer (T1) is connected to the S end of the first-phase high-frequency lower tube GaN HEMT switch tube (Q12) and the negative electrode of the DC input power supply; the secondary same-name end of the transformer is connected to the S end of the first-phase secondary low-on-resistance SiC rectifier bridge arm upper tube (S11), the D end of the first-phase secondary low-on-resistance SiC rectifier bridge arm lower tube (S12), the D end of the first-phase secondary low-on-resistance SiC rectifier bridge arm upper tube (S11) is connected to the D end of the first-phase secondary low-on-resistance SiC rectifier bridge arm upper tube (S13), the first-phase Buck bus capacitor (C o11 ) end, the first phase Buck supervisor (S buck11 ) is connected to the D terminal, the bus capacitor (C o11 ) is connected to the center tap of the high-frequency transformer (T1), the first-phase LLC power filter capacitor (C o12 ) one end, the first phase Buck freewheeling tube (S buck12 ), the S end of the first-phase secondary low on-resistance SiC rectifier bridge arm upper tube (S13) is connected to the D end of the first-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S14) and the opposite end of the high-frequency transformer (T1), the S end of the first-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S12) is connected to the S end of the first-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S14) and the first-phase LLC partial power filter capacitor (C o12 ) is connected to one end of the first phase Buck supervisor (S buck11 ) and the first phase Buck freewheeling tube (S buck12 ) of the D terminal, the first phase Buck inductor (L buck1 ) and the output capacitor (C o ) one end, output load (R Load ) is connected to one end, the output load (R Load ) and the output capacitor (C o ) one end, the first phase LLC power filter capacitor (C o12 ), the S end of the first-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S14), and the S end of the first-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S12); the positive electrode of the DC input power supply is connected to the D end of the second-phase high-frequency upper tube GaN HEMT switch tube (Q21); the S end of the high-frequency upper tube GaN HEMT switch tube (Q21) is connected to the D end of the second-phase high-frequency lower tube GaN HEMT switch tube (Q22), the second-phase resonant inductor (L r2 ) one end, the other end of the resonant inductor and the second phase resonant capacitor (C r2 ), the other end of the resonant capacitor is connected to the primary same-name end of the second-phase high-frequency transformer (T2), the primary opposite-name end of the high-frequency transformer (T1) is connected to the S end of the second-phase high-frequency lower tube GaN HEMT switch tube (Q22) and the negative electrode of the DC input power supply; the secondary same-name end of the transformer is connected to the S end of the second-phase secondary low-on-resistance SiC rectifier bridge arm upper tube (S21), the D end of the second-phase secondary low-on-resistance SiC rectifier bridge arm lower tube (S22), the D end of the second-phase secondary low-on-resistance SiC rectifier bridge arm upper tube (S21) is connected to the D end of the second-phase secondary low-on-resistance SiC rectifier bridge arm upper tube (S23), the second-phase Buck bus capacitor (C o21 ) one end, the second phase Buck supervisor (S buck21 ) is connected to the D terminal, the bus capacitor (C o21 ) is connected to the center tap of the high-frequency transformer (T1), the second-phase LLC power filter capacitor (C o22 ) one end, the second phase Buck freewheeling tube (S buck22 ), the S end of the second-phase secondary low on-resistance SiC rectifier bridge arm upper tube (S23) is connected to the D end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S24) and the opposite end of the high-frequency transformer (T1), the S end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S22) is connected to the S end of the second-phase secondary low on-resistance SiC rectifier bridge arm lower tube (S24) and the second-phase LLC partial power filter capacitor (C o22 ) is connected to one end of the second phase Buck supervisor (S buck21 ) and the second phase Buck freewheeling tube (S buck22 ) of the D terminal, the second-phase Buck inductor (L buck2 ) and the output capacitor (C o ) one end, output load (R Load ) is connected to one end, the output load (R Load ) and the output capacitor (C o ) one end, the second phase LLC part power filter capacitor (C o22 ), the S end of the second-phase secondary low-on-resistance SiC rectifier bridge arm lower tube (S24), and the S end of the second-phase secondary low-on-resistance SiC rectifier bridge arm lower tube (S22); the first output end of the first-phase Buck buck inductor current sampling module (2) is connected to the input end of the first-phase low-pass filter (9), the first output end of the second-phase Buck buck inductor current sampling module (3) is connected to the input end of the second-phase low-pass filter (10), the output end of the first-phase low-pass filter (9) is connected to the first input end of the current comparison module (7), the first input end of the first-phase difference module (16), and the first input end of the current bus module (8), and the output end of the second-phase low-pass filter (10) is connected to the current comparison module (7). The first output end of the current bus module (8) is connected to the second input end of the first phase difference module (16), the second output end of the current bus module (8) is connected to the first input end of the second phase difference module (17), the first output end of the first phase difference module (16) is connected to the input end of the first phase voltage compensation ratio link (14), the first output end of the second phase difference module (17) is connected to the first input end of the second phase voltage compensation ratio link (15), the first output end of the first phase voltage compensation ratio link (14), the first output end of the output voltage sampling module (1), and the reference voltage V ref connected to the first adder, the first output end of the second phase voltage compensation ratio link (15), the first output end of the output voltage sampling module (1), the reference voltage V ref The circuit is connected to a second adder, the output end of the first adder is connected to a first-phase voltage loop PI controller (4), the output end of the second adder is connected to a second-phase voltage loop PI controller (12), the output end of the first-phase voltage loop PI controller (4) is connected to an input end of a first-phase PWM output module (6), the output end of the second-phase voltage loop PI controller (12) is connected to an input end of a second-phase PWM output module (11), the output end of the first-phase PWM output module (6) is used to drive a first-phase Buck circuit bridge arm in the interleaved parallel LLC circuit topology, and the output end of the second-phase PWM output module (11) is used to drive a second-phase Buck circuit bridge arm in the interleaved parallel LLC circuit topology.

3. A current balancing method for staggered parallel LLC DC-DC resonant converters, using a staggered parallel LLC DC-DC resonant converter as claimed in claim 1 or 2, characterized in that: The steps include: S1, collects the first phase output current I of the interleaved parallel LLC o1 , the second phase output current I o2 will pass through the low-pass filter, and I o2 with I o1 Compare and get the current value with larger current as bus current; S2, respectively, subtract I from the current bus o2 with I o1 The difference between each phase and the current bus is obtained, and then the current sharing compensation is added to the reference voltage V through the proportional link. ref superior; S3, collects the output voltage V of the interleaved parallel LLC o , and the output voltage V o With the set output voltage V ref The voltage error signals of the two phases are obtained by subtracting the sum of the sum of the first phase current sharing compensation link and the second phase current sharing compensation link, and then the obtained error signals are input into the voltage loop PI controller of the two phases; S4, the output duty ratios d1 and d2 of the two-phase voltage loop PI controller are then compared with the carrier with a phase difference of 180°, and the final output duty ratio is d1 real , d2 real The PWM wave is used to drive the Buck tube and freewheeling tube of each phase of the interleaved parallel LLC resonant converter; S5, 100K open loop square wave signal V square Drive LLC high frequency half-bridge GaN HEMT switch tube.

4. The current balancing method of interleaved parallel LLC DC-DC resonant converters according to claim 3, characterized in that: The two diodes on the secondary side of the traditional LLC are changed into a full-bridge structure, two bus capacitors are used, and a Buck circuit is connected to the back stage. The gain of the Buck circuit is used to compensate for the LLC current unevenness problem caused by parameter differences.

5. The current balancing method of interleaved parallel LLC DC-DC resonant converters according to claim 3, characterized in that: Use the current bus to automatically balance the current difference.

6. The current balancing method of interleaved parallel LLC DC-DC resonant converters according to any one of claims 3 to 5, characterized in that: Current compensation is used to influence the duty cycle.

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