A high-efficiency control device and method for a resonant converter with a damping circuit

Abstract

The present invention discloses a high-efficiency control device and method applicable to a resonant converter with a damping circuit. The control method adopts the discontinuous current mode (DCM) to solve the problems of the existing control method for electric vehicle chargers, such as being too complex, having low efficiency, and poor CC-to-CV transition performance. The device includes: an inverter circuit, a resonant circuit, a high-frequency transformer, a damping circuit, a rectifier circuit, a filter circuit, a voltage and current acquisition circuit, a controller, and a drive circuit. By adopting a special discontinuous current modulation method, the resonant converter has an inherent CC-to-CV characteristic, making its operation more stable and reliable. Zero-current switching of all switching devices is achieved, reducing switching losses. No power backflow is realized, reducing transmission losses. A damping circuit is added to the topology to reduce voltage oscillation. Compared with traditional electric vehicle chargers, this control scheme enables the converter to operate under the inherent CC-to-CV characteristic, featuring high efficiency and stability.

Description

Technical Field

[0001] The present invention relates to the technical fields of power electronics and power automation equipment, and particularly relates to a high-efficiency control device and method for a resonant converter with a damping circuit. Background Art

[0002] With the development of the electric vehicle industry, DC-DC converters for battery charging applications have received increasing attention. Resonant converters are the most popular DC-DC converters for battery charging due to their outstanding advantages of soft switching, high power density, and high efficiency. Discontinuous current mode (DCM) control is also widely used in battery charging, but conventional control methods mainly have three defects: (1) large reverse power appears, resulting in high transmission losses; (2) the switching frequency is much lower than the resonant frequency, further increasing power losses, and if not satisfied, the CC characteristic disappears; (3) high oscillations increase EMI noise. Therefore, this method is mainly used for high-voltage charging or power supply equipment, but is not suitable for electric vehicle battery charging because electric vehicle battery charging requires high efficiency to adapt to a wide operating range. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to design a high-efficiency discontinuous current mode (DCM) control device and method for a resonant converter with a damping circuit to solve the problems of low transmission efficiency and poor stability of existing resonant converters.

[0004] The present invention provides a high-efficiency control device and method for a resonant converter with a damping circuit. The device includes: a power supply, an inverter circuit, a resonant circuit, a high-frequency transformer, a damping circuit, a rectifier circuit, a filter circuit, a load, a voltage and current acquisition circuit, a controller, and a drive circuit;

[0005] The output end of the power supply is connected to the first input end of the inverter circuit. The input end of the resonant circuit is connected to the output end of the inverter circuit, and the output end of the resonant circuit is connected to the input end of the high-frequency transformer; the output end of the high-frequency transformer is connected to the input end of the rectifier circuit; the output end of the rectifier circuit is connected to the input end of the filter circuit; the output end of the filter circuit is connected to the load;

[0006] The output end of the high-frequency transformer is connected to the damping circuit;

[0007] The feedback end of the filter circuit is connected to the input end of the voltage and current acquisition circuit; the output end of the voltage and current acquisition circuit is connected to the input end of the controller, the output end of the controller is connected to the input end of the drive circuit, and the output end of the drive circuit is connected to the second input end of the inverter circuit.

[0008] Further, the resonant converter adopts a discontinuous current control method to transfer energy from the power supply to the load.

[0009] Further, the inverter circuit includes four identical switching tubes S1 to S4. A group of parallel-connected diodes and buffer capacitors are respectively connected between the drain and source pins of the switching tubes S1 to S4. The anode of the diode is connected to the source of the corresponding switching tube, and the cathode is connected to the drain of the corresponding switching tube. The source of the switching tube S1 is connected to the drain of the switching tube S2, and the source of the switching tube S3 is connected to the drain of the switching tube S4. The drains of the switching tubes S1 and S3 are connected to the positive pole of the power supply, and the sources of the switching tubes S2 and S4 are connected to the negative pole of the power supply. The types of the switching tubes S1 to S4 include MOSFET and BJT.

[0010] Further, the resonant circuit adopts an LLC resonant circuit including an inductor and a capacitor. The LLC resonant circuit includes a resonant inductor L r , an exciting inductor L m and a resonant capacitor C r ; One end of the resonant capacitor C r is connected to the source of the switching tube S1 of the inverter circuit, and the other end is connected in series with the resonant inductor L r ; The other end of L r is respectively connected to one end of the primary side of the high-frequency transformer and one end of the exciting inductor L m ; The exciting inductor L m is connected in parallel at both ends of the primary side of the high-frequency transformer, and the other end of L m is connected to the drain of the switching tube S4 of the inverter circuit.

[0011] Further, the high-frequency transformer is a high-frequency isolation transformer.

[0012] Further, the damping circuit includes a damping resistor R d , two switching tubes S s1 , S s2 ; A group of parallel-connected diodes and buffer capacitors are connected between the source and drain pins of the switching tubes S s1 , S s2 . The anode of the diode is connected to the source of the corresponding switching tube, and the cathode of the diode is connected to the drain of the corresponding switching tube; One end of the resistor R d is connected to one end of the secondary side of the transformer, and the other end of the resistor R d is connected to the drain of the switching tube S s1 , the source of the switching tube S s1 is connected to the source of the switching tube S s2 , and the drain of the switching tube S s2 is connected to the other end of the secondary side of the transformer.

[0013] Further, the rectifier circuit has four identical diodes D1 to D4. The anode of diode D1, the cathode of diode D2 are connected to one end of the secondary side of the transformer, and the anode of diode D3 is connected to the cathode of diode D4 and then connected to the other end of the secondary side of the transformer; the cathode of diode D1 is connected to the cathode of diode D3 and then connected to the positive pole of the load, and the anode of diode D2 is connected to the anode of diode D4 and then connected to the negative pole of the load.

[0014] Further, the filter circuit is a DC filter capacitor C o , and the positive pole of capacitor C o is connected to the cathode of diode D3, and the negative pole of capacitor C o is connected to the anode of diode D4.

[0015] A high-efficiency control method for a resonant converter with a damping circuit includes the following steps:

[0016] S1. Collect the load terminal voltage value V bat and the current value I o flowing through the load through a voltage and current acquisition circuit;

[0017] S2. Judge the magnitude of the load terminal voltage value. If V bat < V i / n, the converter operates in the CC charging mode; if V bat = V i / n, the converter operates in the CV charging mode, where V i is the power supply voltage value and n is the turns ratio of the high-frequency transformer;

[0018] S3. Use the current value I o collected in step S1 as the input of the controller, calculate the switching tube operating frequency compensation value, and adjust the operating frequency of the switching tube through the output of the drive circuit. According to the formula Δf s = K p e + K i ×(∫edt + C) to obtain the switching tube operating frequency compensation; where Δf s is the switching frequency compensation value, e is the current error, e = I ref - I o ; K p and K i are the load current proportionality coefficient and the load current integral coefficient respectively, C is the integral constant, the C value calculated in the current beat is the integral ∫edt calculated in the previous beat plus the value of C, C = 0 for the first calculation, and I ref is the load current set value;

[0019] S4. At t0 to T rDuring the / 2 time period, S1 and S4 are turned on, while S2, S3, and S s1 and S s2 are turned off. V i charges V bat through the resonant tank; the expression for the resonant current at this time is:

[0020]

[0021] The expression for the resonant voltage is:

[0022] V r =(V r0 -V i +nV bat )cosω r t + V i -nV bat

[0023] where T r is the resonant period time, and Z r is the resonant impedance, and the calculation expression is: V r0 is the resonant voltage value at time t0, and ω r is the resonant angular frequency, and the calculation expression is

[0024] At this time, according to the judgment in step S1, if the converter operates in the CC charging mode, step S5 is executed next; if the converter operates in the CV charging mode, step S7 is executed next;

[0025] S5. During the T r / 2 to T r time period, S2 and S4 are turned on, while S1, S3, and S s1 and S s2 are turned off. At this time, V bat is relatively low, and the rectifier circuit diodes D2 and D3 are turned on, and the resonant circuit continues to charge the load; the expression for the resonant current at this time is:

[0026]

[0027] The expression for the resonant voltage is:

[0028]

[0029] where V r1 is the resonant cavity voltage value at T r / 2 moment.

[0030] S6. During the T r to T s / 2 time period, S1 to S4 are turned off, and S s1 and Ss2 Turn on, the resonant circuit resonates with the parasitic capacitance of the switching transistor, i r Through R d Rapidly decay, the circuit operates in the critical or overdamped state. At this time, the charging current expression is:

[0031]

[0032] Among them, T s is the period time, f r is the resonant frequency; until the load voltage V bat reaches V i / n, return to step S2;

[0033] S7. In the time period of T r / 2 to T r , S2 and S4 are turned on, and S1, S3, S s1 , S s2 are turned off. At this time, due to the large V bat , all the diodes of the rectifier circuit are turned off, and the resonant cavity resonates with the exciting inductor L m ;

[0034] S8. In the time period of T r to T s / 2, S1 to S4 are turned off, and S s1 , S s2 are turned on, the resonant circuit resonates with the parasitic capacitance of the switching transistor, i r passes through R d and rapidly decays to 0. In this stage, the load voltage is clamped to V i / n. At this time, the calculation expression of the load current is:

[0035]

[0036] Among them, V OCV is the open-circuit voltage of the storage battery, r bat is the internal resistance of the storage battery. According to the above steps, the charging work is completed until.

[0037] Furthermore, in step S3, the determination process of the load current proportionality coefficient K p and the load current integration coefficient K i is as follows:

[0038] S31. Take the initial value of K i as 0;

[0039] S32. First, debug K p , check whether the load current waveform of the resonant converter oscillates at this time. If so, reduce K pUntil the waveform oscillation is eliminated, go to process S33; otherwise, repeat process S32 and increase K p ;

[0040] S33. Fix the value of K p and debug K i , check whether the load current waveform fluctuates at this time. If it does, decrease K i until the waveform fluctuation is eliminated; otherwise, repeat process S33 and increase K i ;

[0041] S34. Take the final values of K p and K i as the load current proportionality coefficient K p and the load current integral coefficient respectively.

[0042] The beneficial effects brought by the technical solution provided by the present invention are as follows:

[0043] Compared with the prior art, the present invention solves the problems of low transmission efficiency and poor stability of the existing resonant converter, enables the converter to achieve as small switching losses and conduction losses as possible under the condition of a wide gain range, and has an inherent CC-to-CV characteristic, making the converter have good stability. Description of the Drawings

[0044] Figure 1 is the schematic diagram of a high-efficiency control device for a resonant converter with a damping circuit according to the present invention;

[0045] Figure 2 is the circuit diagram of a high-efficiency control device for a resonant converter with a damping circuit according to an embodiment of the present invention;

[0046] Figure 3 is the schematic diagram of the switching tube drive signal of a high-efficiency control method for a resonant converter with a damping circuit according to an embodiment of the present invention;

[0047] Figure 4 is the waveform diagram of the resonant voltage and current in the CC charging mode of a high-efficiency control method for a resonant converter with a damping circuit according to an embodiment of the present invention;

[0048] Figure 5 is the waveform diagram of the resonant voltage and current in the CV charging mode of a high-efficiency control method for a resonant converter with a damping circuit according to an embodiment of the present invention. Detailed Embodiments

[0049] To make the objectives, technical solutions and advantages of the present invention clearer, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

[0050] Please refer to Figure 1 and Figure 2 ,Figure 1 is the schematic diagram of a high - efficiency control device for a resonant converter with a damping circuit according to the present invention; Figure 2 is the circuit diagram of a high - efficiency control device for a resonant converter with a damping circuit according to an embodiment of the present invention.

[0051] A high - efficiency control device and method for a resonant converter with a damping circuit, wherein the device includes: a power supply, an inverter circuit, a resonant circuit, a high - frequency transformer, a damping circuit, a rectifier circuit, a filter circuit, a load, a voltage and current acquisition circuit, a controller, and a drive circuit;

[0052] The output end of the power supply is connected to the first input end of the inverter circuit, the input end of the resonant circuit is connected to the output end of the inverter circuit, and the output end of the resonant circuit is connected to the input end of the high - frequency transformer; the output end of the high - frequency transformer is connected to the input end of the rectifier circuit; the output end of the rectifier circuit is connected to the input end of the filter circuit; the output end of the filter circuit is connected to the load;

[0053] The output end of the high - frequency transformer is connected to the damping circuit;

[0054] The feedback end of the filter circuit is connected to the input end of the voltage and current acquisition circuit; the output end of the voltage and current acquisition circuit is connected to the input end of the controller, the output end of the controller is connected to the input end of the drive circuit, and the output end of the drive circuit is connected to the second input end of the inverter circuit.

[0055] The resonant converter adopts a discontinuous current control method to transfer energy from the power supply to the load.

[0056] The inverter circuit adopts a full - bridge voltage - type converter to convert the DC voltage of the power supply into a square - wave voltage with periodic changes and symmetric positive and negative half - cycles according to the switching - tube modulation signal. The rated voltage V of the power supply i is 400V, and the switching frequency is set to 52kHz. The inverter circuit includes four identical switching tubes S1 - S4. A group of parallel - connected diodes and buffer capacitors are respectively connected between the drain and source pins of the switching tubes S1 - S4. The anode of the diode is connected to the source of the corresponding switching tube, and the cathode is connected to the drain of the corresponding switching tube. The source of switching tube S1 is connected to the drain of switching tube S2, and the source of switching tube S3 is connected to the drain of switching tube S4; the drains of switching tubes S1 and S3 are connected to the positive pole of the power supply, and the sources of switching tubes S2 and S4 are connected to the negative pole of the power supply. The types of switching tubes S1 - S4 include MOSFET and BJT.

[0057] The resonant circuit adopts an LLC resonant circuit including an inductor and a capacitor to generate a high - frequency resonant current under the excitation of the square - wave voltage. The LLC resonant circuit includes a resonant inductor L r 、an exciting inductor L m and a resonant capacitor Cr ; The resonant capacitor C r has one end connected to the source electrode of the switching transistor S1 of the inverter circuit, and the other end is in series with the resonant inductor L r ; L r has the other end respectively connected to one end of the primary side of the high-frequency transformer and one end of the exciting inductor L m ; The exciting inductor L m is connected across the two ends of the primary side of the high-frequency transformer in parallel, and the other end of L m is connected to the drain electrode of the switching transistor S4 of the inverter circuit.

[0058] The high-frequency transformer includes a high-frequency isolation transformer, a high-frequency autotransformer, and a high-frequency transformer with a center tap. In this embodiment, the high-frequency transformer is a high-frequency isolation transformer, which is used to amplify or reduce the high-frequency resonant voltage and current. Under the excitation of the square-wave voltage output by the inverter circuit, the resonant inductor Lr, the resonant capacitor Cr of the resonant circuit and the exciting inductor Lm of the primary side of the high-frequency isolation transformer generate an approximately sinusoidal high-frequency resonant current, which is transmitted to the secondary side through the primary side of the high-frequency isolation transformer.

[0059] The damping circuit includes a damping resistor R d , two switching transistors S s1 , S s2 ; Between the source and drain electrodes of the switching transistors S s1 , S s2 , a group of parallel-connected diodes and buffer capacitors are connected. The anode of the diode is connected to the source electrode of the corresponding switching transistor, and the cathode of the diode is connected to the drain electrode of the corresponding switching transistor; One end of the resistor R d is connected to one end of the secondary side of the transformer, and the other end of the resistor R d is connected to the drain electrode of the switching transistor S s1 , the source electrode of the switching transistor S s1 is connected to the source electrode of the switching transistor S s2 , and the drain electrode of the switching transistor S s2 is connected to the other end of the secondary side of the transformer. During the period when all the switching transistors are turned off, the resonant current rapidly decays through the damping circuit, realizing zero-current switching of the switching transistors.

[0060] A full-wave rectifier circuit is adopted to convert the high-frequency resonant current into a direct current. In the CC mode, the secondary-side load voltage V bat is 400V, and in the CV mode, the load current I o is 2.5A.

[0061] The rectifier circuit has a total of four identical diodes D1 to D4. The anode of diode D1 and the cathode of diode D2 are connected to one end of the secondary side of the transformer. The anode of diode D3 is connected to the cathode of diode D4 and then connected to the other end of the secondary side of the transformer. The cathode of diode D1 is connected to the cathode of diode D3 and then connected to the positive pole of the load. The anode of diode D2 is connected to the anode of diode D4 and then connected to the negative pole of the load.

[0062] The filter circuit is a DC filter capacitor C o , and the capacitor C o 's positive pole is connected to the cathode of diode D3, and the negative pole of capacitor C o is connected to the anode of diode D4. The filter circuit is used to filter out the harmonics in the current output by the rectifier circuit during energy transmission and provide stable DC energy for the load.

[0063] Please refer to Figure 3 、 Figure 4 and Figure 5 , Figure 3 which is a schematic diagram of the switching tube drive signal of a high-efficiency control method for a resonant converter with a damping circuit according to an embodiment of the present invention; Figure 4 which is the resonant voltage and current waveforms in the CC charging mode of a high-efficiency control method for a resonant converter with a damping circuit according to an embodiment of the present invention; Figure 5 which is the resonant voltage and current waveforms in the CV charging mode of a high-efficiency control method for a resonant converter with a damping circuit according to an embodiment of the present invention.

[0064] A high-efficiency control method for a resonant converter with a damping circuit includes the following steps:

[0065] S1. Collect the load terminal voltage value V bat and the current value I o flowing through the load through a voltage and current acquisition circuit.

[0066] S2. Judge the magnitude of the load terminal voltage value. If V bat < V i / n, the converter operates in the CC charging mode; if V bat = V i / n, the converter operates in the CV charging mode, where V i is the power supply voltage value and n is the high-frequency transformer turns ratio.

[0067] S3. Take the current value I o collected in step S1 as the input of the controller, calculate the switching tube operating frequency compensation value, and adjust the operating frequency of the switching tube through the output of the drive circuit. According to the formula Δf s = K p e + K i×(∫edt + C) obtains the switching tube operating frequency compensation, where Δf s is the switching frequency compensation value, e is the current error, e = I ref - I o ; K p and K i are the load current proportionality coefficient and the load current integral coefficient respectively, C is the integral constant, the value of C calculated in the current beat is the integral ∫edt calculated in the previous beat plus the value of C, and C = 0 during the first calculation, I ref is the load current set value; among them, S3 and S4 are complementary in phase within T s , and S4 is leading; S1 and S2 are complementary and conducting within the first half of T s , and S1 is leading, S1 and S2 are complementary and conducting within the second half of T s , and S2 is leading, and a certain dead time is considered during the switching; S s1 , S s2 are in the same phase and turn on during the dead time of S1~S4, T s is the cycle time.

[0068] The determination process of the load current proportionality coefficient K p and the load current integral coefficient K i is as follows:

[0069] S31. Take the initial value of K i as 0;

[0070] S32. First, debug K p , check whether the load current waveform of the resonant converter oscillates at this time. If it does, reduce K p until the waveform oscillation is eliminated, and then go to process S33; otherwise, repeat process S32 and increase K p at the same time;

[0071] S33. Fix the value of K p , debug K i , check whether the load current waveform fluctuates at this time. If it does, reduce K i until the waveform fluctuation is eliminated; otherwise, repeat process S33 and increase K i at the same time;

[0072] S34. Take the final values of K p and K i as the load current proportionality coefficient K p and the load current integral coefficient respectively.

[0073] S4. Within the time period from t0 to T r / 2, S1 and S4 are conducting, and S2, S3, S s1 , S s2 are turned off, Vi Through the resonant tank to V bat Charging; the resonant current expression at this time is:

[0074]

[0075] The expression of resonant voltage is:

[0076] V r =(V r0 -V i +nV bat )cosω r t+V i -nV bat

[0077] Where T r is the resonant cycle time, Z r is the resonant impedance, and the calculation expression is: V r0 is the resonant voltage value at time t0, ω r is the resonant angular frequency, and the calculation expression is

[0078] At this time, according to the judgment of step S1, if the converter operates in the CC charging mode, step S5 is executed next; if the converter operates in the CV charging mode, step S7 is executed next.

[0079] S5, in T r / 2~T r During this time period, S2 and S4 are turned on, S1, S3, and S s1 、S s2 Shutdown, at this time V bat The rectifier circuit diodes D2 and D3 are turned on, and the resonant circuit continues to charge the load. The expression of the resonant current at this time is:

[0080]

[0081] The expression of resonant voltage is:

[0082]

[0083] Among them, V r1 It's T r / 2 moment resonant cavity voltage value.

[0084] S6, in T r ~T s During the / 2 period, S1~S4 are turned off, S s1 、S s2 When it is turned on, the resonant circuit resonates with the parasitic capacitance of the switch tube, i r By Rd Quick decay, the circuit operates in a critically damped or overdamped state. At this time, the charging current expression is:

[0085]

[0086] Where T s is the period time, and f r is the resonant frequency; it realizes that the charging current is independent of the load until the load voltage V bat reaches V i / n, and return to step S2.

[0087] S7. In the time period of T r / 2 to T r , S2 and S4 are turned on, and S1, S3, S s1 , S s2 are turned off. At this time, due to the large V bat , all the diodes in the rectifier circuit are disconnected, and the resonant cavity resonates with the exciting inductor L m . Since L m is much larger than the resonant inductor, it can be considered that the resonant current and voltage approximately remain unchanged in this stage.

[0088] S8. In the time period of T r to T s / 2, S1 to S4 are turned off, and S s1 , S s2 are turned on. The resonant circuit resonates with the parasitic capacitance of the switching tube, and i r rapidly decays to 0 through R d . In this stage, the load voltage is clamped to V i / n. At this time, the calculation expression of the load current is:

[0089]

[0090] Where V OCV is the open-circuit voltage of the battery, and r bat is the internal resistance of the battery. Follow the above steps until the charging operation is completed.

[0091] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-efficiency control device for a resonant converter with a damping circuit, characterized in that, It includes a power supply, an inverter circuit, a resonant circuit, a high-frequency transformer, a damping circuit, a rectifier circuit, a filter circuit, a load, a voltage and current acquisition circuit, a controller, and a drive circuit; The output terminal of the power supply is connected to the first input terminal of the inverter circuit. The input terminal of the resonant circuit is connected to the output terminal of the inverter circuit, and the output terminal of the resonant circuit is connected to the input terminal of the high-frequency transformer. The output terminal of the high-frequency transformer is connected to the input terminal of the rectifier circuit. The output terminal of the rectifier circuit is connected to the input terminal of the filter circuit. The output terminal of the filter circuit is connected to the load; The output terminal of the high-frequency transformer is connected to the damping circuit; The feedback terminal of the filter circuit is connected to the input terminal of the voltage and current acquisition circuit. The output terminal of the voltage and current acquisition circuit is connected to the input terminal of the controller, the output terminal of the controller is connected to the input terminal of the drive circuit, and the output terminal of the drive circuit is connected to the second input terminal of the inverter circuit; The resonant converter adopts a discontinuous current control method to transfer energy from the power supply to the load; The damping circuit includes a damping resistor Rd, two switching tubes Ss1 and Ss2. A group of parallel diodes and a buffer capacitor are connected between the source and drain pins of the switching tubes Ss1 and Ss2. The anode of the diode is connected to the source of the corresponding switching tube, and the cathode of the diode is connected to the drain of the corresponding switching tube. One end of the resistor Rd is connected to one end of the secondary side of the transformer, the other end of the resistor Rd is connected to the drain of the switching tube Ss1, the source of the switching tube Ss1 is connected to the source of the switching tube Ss2, and the drain of the switching tube Ss2 is connected to the other end of the secondary side of the transformer.

2. The high-efficiency control device of a resonant converter with a damping circuit according to claim 1, characterized in that, The inverter circuit includes four identical switching tubes S1 to S4. A group of parallel diodes and a buffer capacitor are respectively connected between the drain and source pins of the switching tubes S1 to S4. The anode of the diode is connected to the source of the corresponding switching tube, and the cathode is connected to the drain of the corresponding switching tube. The source of the switching tube S1 is connected to the drain of the switching tube S2, and the source of the switching tube S3 is connected to the drain of the switching tube S4. The drains of the switching tubes S1 and S3 are connected to the positive pole of the power supply, and the sources of the switching tubes S2 and S4 are connected to the negative pole of the power supply. The types of the switching tubes S1 to S4 include MOSFET and BJT.

3. The high-efficiency control device of a resonant converter with a damping circuit according to claim 1, characterized in that The described resonant circuit uses an LLC resonant circuit including an inductor and a capacitor. The LLC resonant circuit includes a resonant inductor L r , an exciting inductor L m and a resonant capacitor C r ; One end of the resonant capacitor C r is connected to the source electrode of the switching tube S1 of the inverter circuit, and the other end is connected in series with the resonant inductor L r ; The other end of L r is respectively connected to one end of the primary side of the high-frequency transformer and one end of the exciting inductor L m ; The exciting inductor L m is connected across the two ends of the primary side of the high-frequency transformer in parallel, and the other end of L m is connected to the drain electrode of the switching tube S4 of the inverter circuit.

4. The high-efficiency control device of a resonant converter with a damping circuit according to claim 1, characterized in that, The high-frequency transformer is a high-frequency isolation transformer.

5. The high-efficiency control device of a resonant converter with a damping circuit according to claim 1, characterized in that, The rectifier circuit has four identical diodes D1 to D4. The anode of the diode D1 and the cathode of the diode D2 are connected to one end of the secondary side of the transformer. The anode of the diode D3 is connected to the cathode of the diode D4 and then connected to the other end of the secondary side of the transformer. The cathode of the diode D1 and the cathode of the diode D3 are connected and then connected to the positive pole of the load. The anode of the diode D2 and the anode of the diode D4 are connected and then connected to the negative pole of the load.

6. The high-efficiency control device of a resonant converter with a damping circuit according to claim 1, characterized in that, The filter circuit mentioned above is a DC filter capacitor C o , and the capacitor C o has its positive electrode connected to the cathode of diode D3, and the negative electrode of the capacitor C o is connected to the anode of diode D4.

7. A high-efficiency control method for a resonant converter with a damping circuit, implemented based on the high-efficiency control device for a resonant converter with a damping circuit according to any one of claims 1 to 6, characterized in that, It includes the following steps: S1. Collect the load terminal voltage value V through the voltage and current acquisition circuit bat and the current value I flowing through the load o ; S2. Determine the magnitude of the load terminal voltage. If V bat <V i / n, the converter operates in the CC charging mode. If V bat =V i / n, the converter operates in the CV charging mode, where V i is the power supply voltage value and n is the turns ratio of the high-frequency transformer; S3. Take the current value I collected in step S1 o , use it as the input of the controller, calculate the switching tube operating frequency compensation value, and adjust the operating frequency of the switching tube through the output of the drive circuit. According to the formula Δf s = K p e + K i ×(∫edt + C) to obtain the switching tube operating frequency compensation; where Δf s is the switching frequency compensation value, e is the current error, e = I ref - I o ; K p and K i are the load current proportionality coefficient and the load current integral coefficient respectively, C is the integral constant, the C value calculated in the current beat is the integral ∫edt calculated in the previous beat plus the value of C, C = 0 when calculating for the first time, I ref is the load current set value; S4. During the time period from t0 to T / 2, S1 and S4 are turned on, and S2, S3, S r are turned off. V s1 is charged through the resonant tank to V s2 . The expression of the resonant current at this time is: i bat ​​ The expression of the resonant voltage is: V r = (V r0 - V i + nV bat ) cos ω r t + V i - nV bat Where T r is the resonance period time, and Z r is the resonance impedance, and the calculation expression is: V r0 is the resonance voltage value at time t0, and ω r is the resonance angular frequency, and the calculation expression is At this time, according to the judgment in step S1, if the converter works in the CC charging mode, step S5 is executed next. If the converter works in the CV charging mode, step S7 is executed next; S5, at T r / 2 to T r During the time period, S2 and S4 are turned on, and S1, S3, S s1 , S s2 are turned off. At this time, V bat is relatively low, and the rectifier circuit diodes D2 and D3 are turned on, and the resonant circuit continues to charge the load; the expression of the resonant current at this time is: The expression of the resonant voltage is: Among them, V r1 is the voltage value of the resonant cavity at time T r / 2; S6. During the period from T r to T s / 2, S1 to S4 are turned off, and S s1 and S s2 are turned on. The resonant circuit resonates with the parasitic capacitance of the switching transistor, and i r rapidly decays through R d . The circuit operates in a critical or overdamped state. At this time, the charging current expression is as follows: Among them, T s is the cycle time, and f r is the resonance frequency; until the load voltage V bat reaches V i / n, return to step S2; S7, at T r / 2 to T r During this time period, S2 and S4 are turned on, while S1, S3, S s1 , S s2 are turned off. At this time, due to the relatively large V bat , all the diodes in the rectifier circuit are turned off, and the resonant cavity resonates with the excitation inductor L m ; S8, at T r ~T s During the time period of / 2, S1 to S4 are turned off, and S s1 、S s2 are turned on, and the resonant circuit resonates with the parasitic capacitance of the switching transistor, and i r rapidly decays to 0 through R d . During this stage, the load voltage is clamped to V i / n. At this time, the calculation expression of the load current is: Where V OCV is the open-circuit voltage of the storage battery, and r bat is the internal resistance of the storage battery. Carry out the above steps until the charging operation is completed.

8. The high-efficiency control method of a resonant converter with a damping circuit according to claim 7, characterized in that, In step S3, the load current proportionality coefficient K p and the load current integral coefficient K i are determined as follows: S31. Set the initial value of K i to 0; S32. First, debug K p , and check whether the load current waveform of the resonant converter oscillates at this time. If it does, reduce K p until the waveform oscillation is eliminated, and then go to process S33; otherwise, repeat process S32 and increase K at the same time p ; S33. Fix K p value and debug K i , and check whether the load current waveform fluctuates at this time. If it does, reduce K i until the waveform fluctuation is eliminated; otherwise, repeat process S33 and increase K at the same time i ; S34. Use the final values of K p and K i as the load current proportionality factor K p and the load current integral coefficient respectively.

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