Resonant converter and switching power supply

Abstract

The resonant converter comprises a primary side circuit, a transformer and a secondary side circuit which are connected in sequence, and the primary side circuit comprises a primary side energy storage network, a primary side switching network and a resonant network; the primary side switching network comprises a first bridge arm and a second bridge arm which are connected in parallel; the resonant network comprises a resonant inductor, a first resonant capacitor, a second resonant capacitor and an auxiliary capacitor; one end of the resonant inductor is connected with the midpoint of the first bridge arm and one end of the auxiliary capacitor, and the other end of the resonant inductor is connected with one end of the first resonant capacitor. The other end of the second resonant capacitor is connected with the other end of the transformer primary winding, the other end of the auxiliary capacitor and the second bridge arm midpoint. On the basis of not increasing the working frequency range, the gain range of the output voltage during reverse working of the resonant converter can be improved, and soft switching of a switching device can be realized during forward and reverse working.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a resonant converter and a switching power supply. Background Art

[0002] Traditional hard-switching converters suffer from high switching losses and low efficiency. Reliable operation requires larger transformers and heat sinks, making them difficult to meet the demands of miniaturization and high power density in electronic products. Resonant converters, due to their soft-switching characteristics, offer advantages such as high efficiency, low electromagnetic interference, and reduced voltage and current stress on components, and are therefore gaining increasing popularity.

[0003] Compared with traditional isolated converters, LLC or LCC resonant converters add inductor-capacitor energy storage devices between the transformer and the bridge arm. Through different combinations of energy storage devices, when the converter is working, the inductor and capacitor and other energy storage devices are in a resonant state, which can achieve zero voltage switch-on (ZVS) and zero current shutdown (ZCS) of the switching devices, significantly reducing the switching loss and electrical stress of the switching devices, thereby increasing the switching frequency and reducing the size of the power supply.

[0004] In situations where the output voltage is high and the output power is large, the parasitic capacitance inside the transformer will have a greater impact on the resonant converter. The LCC resonant converter can not only utilize the parasitic capacitance in the transformer but also use the leakage inductance in the transformer as part of the resonant element. Moreover, when the LCC resonant converter is working at a constant current output, the switching frequency varies little with the load, and it has high reliability. However, when working in the reverse direction, its resonant network becomes an LC resonance and no longer has the characteristics of the LCC resonant structure, thus losing the advantage of small switching frequency variation at constant current output.

[0005] At the same time, due to limitations of its circuit structure, the LCC bidirectional resonant converter cannot achieve a boost characteristic during reverse operation. Its normalized gain during reverse operation is less than 1, which prevents reverse boosting and limits the output voltage range during reverse operation. To achieve the requirement of an output voltage gain greater than 1 during reverse operation, a circuit structure with symmetry between the primary and secondary sides can be adopted. This topology is simple, has consistent resonant characteristics during forward and reverse operation, and is easy to control. However, the symmetrical structure has similar input and output voltage and current levels, which limits its application. In addition, the number of energy storage devices (inductors and capacitors) is large, which increases the size and cost of the resonant converter. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a resonant converter and a switching power supply, which can at least to some extent overcome one of the above-mentioned defects in the prior art.

[0007] As a first aspect of the present invention, the embodiment and technical solution of the resonant converter provided are as follows:

[0008] A resonant converter includes a first external positive terminal, a first external negative terminal, a second external positive terminal, and a second external negative terminal, and a primary side circuit, a transformer, and a secondary side circuit connected in sequence, wherein:

[0009] The primary-side circuit includes a primary-side energy storage network, a primary-side switching network and a resonant network; the primary-side switching network includes a first bridge arm and a second bridge arm connected in parallel; the resonant network includes a resonant inductor, a first resonant capacitor, a second resonant capacitor and an auxiliary capacitor; one end of the primary-side energy storage network, one end of the first bridge arm and one end of the second bridge arm are simultaneously connected to the first external positive end, the other end of the primary-side energy storage network, the other end of the first bridge arm and the other end of the second bridge arm are simultaneously connected to the first external negative end, one end of the resonant inductor is simultaneously connected to the midpoint of the first bridge arm and one end of the auxiliary capacitor, the other end of the resonant inductor is connected to one end of the first resonant capacitor, the other end of the first resonant capacitor is simultaneously connected to one end of the second resonant capacitor and one end of the primary winding of the transformer, and the other end of the second resonant capacitor is simultaneously connected to the other end of the primary winding of the transformer, the other end of the auxiliary capacitor and the midpoint of the second bridge arm;

[0010] The secondary-side circuit includes a secondary-side energy storage network and a secondary-side switch network; the secondary-side switch network includes a third bridge arm and a fourth bridge arm connected in parallel; one end of the secondary-side energy storage network, one end of the third bridge arm, and one end of the fourth bridge arm are simultaneously connected to the second external positive end, the other end of the secondary-side energy storage network, the other end of the third bridge arm, and the other end of the fourth bridge arm are simultaneously connected to the second external negative end, the midpoint of the third bridge arm is connected to one end of the secondary winding of the transformer, and the midpoint of the fourth bridge arm is connected to the other end of the secondary winding of the transformer.

[0011] Furthermore, the capacitance of the auxiliary capacitor is equal to the capacitance of the second resonant capacitor.

[0012] Preferably, all the switch tubes in the primary-side switch network and the secondary-side switch network are N-MOS tubes or IGBTs.

[0013] Furthermore, when the resonant converter is in an operating mode in which energy flows from the primary side to the secondary side, the voltage across the auxiliary capacitor is clamped by the voltage between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and does not participate in resonance. A resonant network is formed by the resonant inductor, the first resonant capacitor, and the second resonant capacitor.

[0014] Furthermore, when the resonant converter is in an operating mode in which energy flows from the secondary side to the primary side, the voltage across the second resonant capacitor is clamped by the voltage across the primary winding of the transformer and does not participate in the resonance. A resonant network is formed by the resonant inductor, the first resonant capacitor and the auxiliary capacitor.

[0015] Furthermore, when the resonant converter operates bidirectionally: the driving signals of the two switch tubes on the first diagonal of the two bridge arms in the inverter side switch network are the first driving signals, and the driving signals of the two switch tubes on the second diagonal are the second driving signals, and the first driving signal and the second driving signal are complementary; the driving signals of the two switch tubes on the first diagonal of the two bridge arms in the rectifier side switch network are the third driving signals, and the driving signals of the two switch tubes on the second diagonal are the fourth driving signals, and the third driving signal and the fourth driving signal are complementary; when the resonant converter is in an operating mode in which energy flows from the primary side to the secondary side, the primary side switch network is the inverter side switch network, and the secondary side switch network is the rectifier side switch network; when the resonant converter is in an operating mode in which energy flows from the secondary side to the primary side, the secondary side switch network is the inverter side switch network, and the primary side switch network is the rectifier side switch network.

[0016] Furthermore, the duty cycle of the first driving signal and the second driving signal are both less than 50%, and both have a certain dead time.

[0017] Furthermore, the duty cycle of the third driving signal and the fourth driving signal are both less than 50%, and the on-pulse width is adjusted in real time according to the power output by the resonant converter.

[0018] Furthermore, the primary-side energy storage network and / or the secondary-side energy storage network include capacitors.

[0019] As a second aspect of the present invention, the technical solution of the embodiment of the switching power supply provided is as follows:

[0020] A switching power supply, comprising the resonant converter described in any one of the first aspects above.

[0021] The resonant converter proposed in the present invention is based on the conventionally known bidirectional LCC resonant converter circuit. By connecting an auxiliary capacitor Cb in parallel between the midpoints of the bridge arms of the primary-side switching network, the bidirectional LCC resonant converter can form an LCC resonant circuit in both forward and reverse operation. Specifically, the following beneficial effects are achieved:

[0022] (1) The resonant converter of the embodiment of the present invention can achieve soft switching of the switch tube in the full load range regardless of whether it is working in forward or reverse direction, thereby improving the working efficiency of the resonant converter and reducing EMI interference;

[0023] (2) When the resonant converter of the embodiment of the present invention is operating in reverse, since the auxiliary capacitor Cb is connected in parallel between the midpoints of the bridge arms of the primary-side switching network, the resonant network of the converter is composed of the parallel auxiliary capacitor Cb, the series resonant inductor Lr, and the series resonant capacitor Cr. Its reverse voltage gain can be greater than 1, thereby improving the output voltage range of the converter when operating in reverse.

[0024] (3) When the resonant converter of the embodiment of the present invention is working in reverse, the resonant circuit is also an LCC structure. When outputting a constant current, the switching frequency of the switching device varies in a small range with load changes, is easy to control, and has high reliability.

[0025] (4) When the resonant converter of the embodiment of the present invention is working, the transformer does not need to store energy, so the transformer does not need to have an air gap, which reduces the labor cost when designing and manufacturing the transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 1 is a schematic diagram of a topology of a bidirectional LCC resonant converter provided by an embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of a bidirectional LCC resonant converter control provided by an embodiment of the present invention;

[0028] Figure 3 1 is a schematic diagram of the forward working power of a bidirectional LCC resonant converter provided by an embodiment of the present invention;

[0029] Figure 4 1 is a schematic diagram of reverse working power of a bidirectional LCC resonant converter provided by an embodiment of the present invention;

[0030] Figure 5 yes Figure 1 A forward operating waveform of a bidirectional LCC resonant converter;

[0031] Figure 6 yes Figure 1 A reverse operating waveform of a bidirectional LCC resonant converter. DETAILED DESCRIPTION

[0032] It should be noted that, unless there is any conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0033] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate to describe the embodiments of the present application here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] It should be understood that in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0036] In addition, the figures of this disclosure are merely schematic diagrams of the present disclosure and are not necessarily drawn to scale. Identical reference numbers in the figures denote identical or similar parts, and therefore repeated descriptions thereof will be omitted. Some of the blocks shown in the figures are functional entities that do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented using software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontrollers.

[0037] Figure 1 : is a schematic diagram of a bidirectional LCC resonant converter topology provided by an embodiment of the present invention, such as Figure 1 As shown, the bidirectional LCC resonant converter topology includes a primary-side energy storage network, a primary-side switching network, a resonant network, a transformer T, a secondary-side switching network, and a secondary-side energy storage network;

[0038] Two ends of the primary side energy storage network Cp are respectively connected to two ends of the primary side switch network, one end of the primary side energy storage capacitor Cp is connected to the first terminal of the primary side switch network, and the other end of the primary side energy storage capacitor Cp is connected to the second terminal of the primary side switch network;

[0039] The primary-side switching network includes a full-bridge circuit, specifically, a first switching tube Q1, a second switching tube Q2, a third switching tube Q3, and a fourth switching tube Q4; the first terminal of the first switching tube Q1 serves as a first input terminal of the primary-side switching network and is simultaneously connected to one end of the primary-side energy storage network Cp and the first terminal of the third switching tube Q3; the second terminal of the first switching tube Q1 is connected to the first terminal of the second switching tube Q2; the second terminal of the second switching tube Q2 serves as a second input terminal of the primary-side switching network and is simultaneously connected to the other end of the primary-side energy storage network Cp and the second terminal of the fourth switching tube Q4; the second terminal of the third switching tube Q3 is connected to the first terminal of the fourth switching tube Q4;

[0040] The resonant network includes a series resonant inductor Lr, a series resonant capacitor Cr, a resonant capacitor Ca connected in parallel across the primary winding of the transformer T, and an auxiliary capacitor Cb connected in parallel across the input terminals of the resonant network; the first input terminal of the resonant network is the second terminal of the first switch tube Q1, the first input terminal of the resonant network is simultaneously connected to one end of the series resonant inductor Lr and one end of the auxiliary capacitor Cb, the other end of the series resonant inductor Lr is connected to one end of the series resonant capacitor Cr, the other end of the series resonant capacitor Cr is simultaneously connected to one end of the parallel resonant capacitor Ca and one end of the primary winding of the transformer T, the other end of the primary winding of the transformer T is simultaneously connected to the other end of the parallel resonant capacitor Ca, the other end of the auxiliary capacitor Cb, and the second input terminal of the resonant network, and the second input terminal of the resonant network is the second terminal of the third switch tube Q3;

[0041] The secondary-side switching network includes a full-bridge circuit, specifically, a fifth switching tube Q5, a sixth switching tube Q6, a seventh switching tube Q7, and an eighth switching tube Q8; the first terminal of the fifth switching tube Q5 serves as the first output terminal of the secondary-side switching network and is simultaneously connected to one end of the secondary-side energy storage network Cs and the first terminal of the seventh switching tube Q7; the second terminal of the fifth switching tube Q5 is simultaneously connected to one end of the secondary winding of the transformer T and the first terminal of the sixth switching tube Q6; the second terminal of the sixth switching tube Q6 serves as the second output terminal of the secondary-side switching network and is simultaneously connected to the other end of the secondary-side energy storage network Cs and the second terminal of the eighth switching tube Q8; the second terminal of the seventh switching tube Q7 is simultaneously connected to the other end of the secondary winding of the transformer T and the first terminal of the eighth switching tube Q8.

[0042] As a specific embodiment, the capacitance of the parallel auxiliary capacitor Cb is equal to the capacitance of the parallel resonant capacitor Ca, so that the resonant cavity parameters of the bidirectional LCC resonant converter topology remain consistent when working in forward or reverse directions.

[0043] As a specific embodiment, all the switching tubes in the primary-side switching network and the secondary-side switching network are N-MOS tubes (N-channel metal oxide semiconductor field effect transistors), the first terminal of the switching tube is the D-stage (drain) of the N-MOS tube, and the second terminal is the S-stage (source) of the N-MOS tube. The N-MOS includes its built-in body diode and the junction capacitance in parallel between the drain and source.

[0044] Figure 2 FIG. 1 is a schematic diagram of a bidirectional LCC resonant converter control system according to an embodiment of the present invention. Figure 2 As shown, it includes a primary-side current and voltage sampling module, a secondary-side current and voltage sampling module, an MCU control module, a primary-side drive control module and a secondary-side drive control module; the primary-side current and voltage sampling module and the secondary-side current and voltage sampling module transmit the collected primary-side current and voltage, and secondary-side voltage and current signals to the MCU control module, and generate a primary-side drive control signal and a secondary-side drive control signal after calculation and processing. The MCU control module transmits the corresponding drive control signals to the primary-side drive module and the secondary-side drive control module respectively, and then the drive module generates the corresponding drive signal to control the switching devices of the primary-side switch network and the secondary-side switch network to be turned on and off.

[0045] Figure 3 FIG. 1 is a schematic diagram of a forward working power of a bidirectional LCC resonant converter provided by an embodiment of the present invention. Figure 3 As shown in the figure, the primary side switch network is the energy input end. The input DC signal is inverted into an AC signal by the primary side switch network and transmitted to the input end of the secondary side switch network through the resonant cavity network and transformer T. The secondary side switch network rectifies the AC signal and generates a stable DC signal through filtering by the secondary side energy storage network to power the back-end load and realize forward energy transmission.

[0046] Figure 4 FIG. 1 is a schematic diagram of a reverse working power of a bidirectional LCC resonant converter provided by an embodiment of the present invention. Figure 4 As shown, the secondary side switch network is the energy input end. The input DC signal is inverted into an AC signal by the secondary side switch network and transmitted to the input end of the primary side switch network through the transformer T and the resonant cavity network. The primary side switch network rectifies the AC signal and generates a stable DC signal through filtering by the primary side energy storage network to power the back-end load and realize reverse energy transmission.

[0047] Figure 5 yes Figure 1 A forward working waveform of a bidirectional LCC resonant converter, such as Figure 5As shown, Q1 / Q4 are the driving waveforms of the switch tubes Q1 and Q4, Q2 / Q3 are the driving waveforms of the switch tubes Q2 and Q3, Ids1 is the current flowing through the switch tube Q1, Vds1 is the voltage across the drain and source of the switch tube Q1, Ids2 is the current flowing through the switch tube Q2, Vds2 is the voltage across the drain and source of the switch tube Q2, Vcb is the voltage across the parallel auxiliary capacitor cb, Vca is the voltage across the parallel resonant capacitor ca, Ica is the current flowing into the parallel resonant capacitor ca, Ir is the resonant cavity current, Ids6 is the current flowing through the switch tube Q6, Vds6 is the voltage across the drain and source of the switch tube Q6, Ids5 is the current flowing through the switch tube Q5, and Vds5 is the voltage across the drain and source of the switch tube Q5. The control logic and specific working principle are analyzed in detail as follows;

[0048] At t0, switches Q1 and Q4 are turned on, achieving zero voltage switching (ZVS).

[0049] During the time period from t0 to t1, the resonant current Ir is equal to the current flowing through the switches Q1 and Q4, and the current direction is negative. During this period, the voltage VCa across the parallel resonant capacitor Ca is clamped to -NVs (N is the turns ratio of the primary winding to the secondary winding of the transformer), and no current flows. The switches Q2 and Q3 are in the off state, the rectifier switches Q6 and Q7 are in the on state, and the voltage VCb across the parallel auxiliary capacitor Cb is clamped to the input voltage Vp.

[0050] At time t1, the resonant cavity current decreases to 0, and the current flowing through the switch tubes Q1 and Q4 decreases to 0; the current flowing through the rectifier switch tubes Q6 and Q7 decreases to 0, the rectifier switch tubes Q6 and Q7 can achieve ZCS, and the parallel resonant capacitor Ca begins to be positively charged;

[0051] During the time period from t1 to t2, the parallel resonant capacitor Ca is positively charged, and the voltage Vcb across the parallel auxiliary capacitor Cb is still clamped to the input voltage Vp. The current of the switch tubes Q1 and Q4 flows from the drain D to the source S. During this time period, the series resonant inductor Lr, the series resonant capacitor Cr, and the parallel resonant capacitor Ca resonate in series. The inductance of the resonant inductor Lr is recorded as Lr, and the sum of the capacitance values of the capacitors Cr and Ca when they resonate in series is recorded as C p , the capacitance of other capacitors is represented by their respective reference symbols, then the resonant frequency f in this time period rp for:

[0052]

[0053] in:

[0054]

[0055] The transformer primary winding voltage VLm is equal to the voltage VCa across the parallel resonant capacitor Ca, VLm=VCa<NVs, and the secondary rectifier switch and diode are both in the off state. During this period, the output end is provided with energy by the energy storage capacitor Cs;

[0056] At time t2, the voltage VCa across the parallel resonant capacitor Ca is charged to NVs and does not participate in resonance. The secondary side rectifier switches Q5 and Q8 are turned on.

[0057] During the time period from t2 to t3, the series resonant inductor Lr and the series resonant capacitor Cr perform series resonance, and the resonant frequency is:

[0058]

[0059] The energy of the primary side of the transformer is transferred to the secondary side, and at the same time, the output energy storage capacitor Cs is charged. The voltage VCa across the parallel resonant capacitor Ca is charged to NVs, and the voltage VCb across the parallel auxiliary capacitor Cb is clamped to the input voltage Vp.

[0060] At t3, switches Q1 and Q4 are turned off;

[0061] The time period t3 to t4 is the dead time of the primary-side switching network. During this time period, the junction capacitance of the switches Q1 and Q4 is positively charged, Vds1 begins to rise, and the current flowing through the internal resistance Rdson of the switches Q1 and Q4 gradually decreases. The body diodes of the switches Q2 and Q3 are turned on and the current increases negatively, their junction capacitance is reversely charged, and Vds2 begins to decrease. During this time period, the voltage VCa across the parallel resonant capacitor Ca is still clamped to NVo, and the voltage VCb across the parallel auxiliary capacitor Cb gradually decreases. The secondary-side rectifier switches Q5 and Q8 are still turned on, and the rectifier current gradually decreases.

[0062] At time t4, the current flowing through the switches Q1 and Q4 decreases to 0, the drain-source voltage Vds2 of the switches Q2 and Q3 drops to 0, the negative current Ids2 flowing through the switches Q2 and Q3 reaches its negative maximum value, and the voltage Vcb across the parallel auxiliary capacitor Cb decreases to -Vp;

[0063] During the time period t4 to t5, the switches Q1 and Q4 are in the off state, the body diodes of the switches Q2 and Q3 are in the on state, the secondary rectifier switches Q5 and Q8 are turned on, and the voltage VCa across the parallel resonant capacitor Ca is clamped to NVo, with no current flowing.

[0064] At t5, switches Q2 and Q3 are turned on, achieving zero voltage switching (ZVS).

[0065] During the time period t5 to t6, the switch segments Q1 and Q4 are turned off, the switch tubes Q2 and Q3 are turned on, and the secondary side rectifier switch tubes Q5 and Q8 are turned on. The voltage VCa across the parallel resonant capacitor Ca is clamped to NVo, and no current flows. The negative current flowing through the switch tubes Q2 and Q3 gradually decreases.

[0066] At t6, the resonant cavity current drops to 0, the negative current flowing through Q2 and Q3 drops to 0, and the current flowing through the secondary switches Q5 and Q8 also drops to 0, achieving ZCS. The parallel resonant capacitor Ca begins to be reversely charged, and the voltage Vcb across the parallel auxiliary capacitor Cb is still clamped to -Vp.

[0067] The working state of the subsequent circuit repeats the working process from t0 to t6;

[0068] Figure 6 yes Figure 1 A reverse working waveform of the bidirectional LCC resonant converter, such as Figure 6 As shown, Q5 / Q8 are the driving waveforms of the switch tubes Q5 and Q8, Q6 / Q7 are the driving waveforms of the switch tubes Q6 and Q7, Ids5 is the current flowing through the switch tube Q5, Vds5 is the voltage across the drain and source of the switch tube Q5, Ids6 is the current flowing through the switch tube Q6, Vds6 is the voltage across the drain and source of the switch tube Q6, Vca is the voltage across the parallel resonant capacitor ca, Vcb is the voltage across the parallel auxiliary capacitor cb, Icb is the current flowing into the parallel auxiliary capacitor, Ir is the resonant cavity current, Ids2 is the current flowing through the switch tube Q2, Vds2 is the voltage across the drain and source of the switch tube Q2, Ids1 is the current flowing through the switch tube Q1, and Vds1 is the voltage across the drain and source of the switch tube Q1. The control logic and specific working principle are analyzed in detail as follows;

[0069] At t0, switches Q5 and Q8 are turned on, achieving zero voltage switching (ZVS).

[0070] During the time period from t0 to t1, the current flowing through the switches Q5 and Q8 decreases in the reverse direction. During this period, the voltage VCa across the parallel resonant capacitor Ca is clamped to NVs, and no current flows. The switches Q6 and Q7 are in the off state, and the rectifier switches Q2 and Q3 are in the on state. The voltage VCb across the parallel auxiliary capacitor Cb is clamped to the output voltage -Vp.

[0071] At time t1, the resonant cavity current decreases to 0, and the current flowing through the switch tubes Q5 and Q8 decreases to 0; the current flowing through the rectifier switch tubes Q2 and Q3 decreases to 0, the rectifier switch tubes Q2 and Q3 can achieve ZCS, and the parallel auxiliary capacitor Cb begins to be positively charged;

[0072] During the time period from t1 to t2, the parallel auxiliary capacitor Cb is positively charged, and the voltage VCa across the parallel resonant capacitor Ca is still clamped to NVs. The current of the switch tubes Q5 and Q8 flows from the drain D to the source S. During this time period, the series resonant inductor Lr, the series resonant capacitor Cr, and the parallel auxiliary capacitor Cb resonate in series. The inductance of the resonant inductor Lr is recorded as Lr, and the sum of the capacitances of the capacitors Cr and Ca when they resonate in series is recorded as C p1 , the capacitance of other capacitors is represented by their respective reference symbols, then the resonant frequency f in this time period rp1 for:

[0073]

[0074] in:

[0075]

[0076] The primary side rectifier switch and diode are both in the off state. During this period, the output end is provided with energy by the energy storage capacitor Cp.

[0077] At time t2, the voltage VCb across the parallel auxiliary capacitor Cb is charged to Vp and does not participate in resonance. The primary-side rectifier switches Q1 and Q4 are turned on.

[0078] During the time period t2 to t3, the series resonant inductor Lr and the series resonant capacitor Cr perform series resonance, and the resonant frequency is the above formula (3). The energy of the secondary side of the transformer is transferred to the primary side, and the primary side energy storage capacitor Cp is charged at the same time. The voltage VCa across the parallel resonant capacitor Ca is clamped to NVs, and the voltage VCb across the parallel auxiliary capacitor Cb is clamped to the input voltage Vp.

[0079] At t3, switches Q5 and Q8 are turned off;

[0080] The time period t3 to t4 is the dead time of the secondary-side switching network. During this time period, the junction capacitance of switches Q5 and Q8 is positively charged, Vds5 begins to rise, and the current flowing through the internal resistance Rdson of switches Q5 and Q8 gradually decreases. The body diodes of switches Q6 and Q7 conduct and the current increases negatively, their junction capacitance is reversely charged, and Vds6 begins to decrease. During this time period, the voltage VCb across the parallel auxiliary capacitor Cb is still clamped to Vp, the voltage VCa across the parallel resonant capacitor Ca gradually decreases, and the secondary-side rectifier switches Q1 and Q4 remain on.

[0081] At time t4, the current flowing through the switch tubes Q5 and Q8 decreases to 0, the drain-source voltage Vds6 of the switch tubes Q6 and Q7 drops to 0, the negative current Ids6 flowing through the switch tubes Q6 and Q7 reaches the negative maximum value, and the voltage VCa across the parallel resonant capacitor Ca decreases to -NVs;

[0082] During the time period t4 to t5, switches Q5 and Q8 are off, the body diodes of switches Q6 and Q7 are on, primary-side rectifier switches Q1 and Q4 are on, and the voltage VCb across the parallel auxiliary capacitor Cb is clamped to Vp, with no current flowing.

[0083] At t5, switches Q6 and Q7 are turned on, achieving zero voltage switching (ZVS).

[0084] During the time period from t5 to t6, the switches Q5 and Q8 are turned off, and the primary-side rectifier switches Q1 and Q4 are turned on. The voltage VCb across the parallel auxiliary capacitor Cb is clamped to Vp, and no current flows. The negative current flowing through the switches Q6 and Q7 gradually decreases.

[0085] At t6, the resonant cavity current drops to 0, the negative current flowing through Q6 and Q7 drops to 0, and the current flowing through the primary-side switches Q1 and Q4 also drops to 0, achieving ZCS. The parallel auxiliary capacitor Cb begins to be reversely charged, and the voltage VCa across the parallel resonant capacitor Ca is still clamped to -NVs.

[0086] The working state of the subsequent circuit repeats the working process from t0 to t6.

[0087] From the above waveform analysis, it can be seen that the bidirectional LCC resonant converter provided by the embodiment of the present invention satisfies the LCC topology structure even when working in reverse direction by adding the parallel auxiliary capacitor Ca.

[0088] An embodiment of the present invention further provides a switching power supply, comprising any of the above-mentioned resonant converters.

[0089] The above-described embodiments of the present invention are merely examples for illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations and modifications can be made based on the above description. It is not possible to enumerate all embodiments here. Any obvious variations or modifications arising from the technical solution of the present invention remain within the scope of protection of the present invention.

Claims

1. A resonant converter comprising a first external positive terminal, a first external negative terminal, a second external positive terminal, and a second external negative terminal, and a primary side circuit, a transformer, and a secondary side circuit connected in sequence, characterized in that: The primary-side circuit includes a primary-side energy storage network, a primary-side switching network and a resonant network; the primary-side switching network includes a first bridge arm and a second bridge arm connected in parallel; the resonant network includes a resonant inductor, a first resonant capacitor, a second resonant capacitor and an auxiliary capacitor; one end of the primary-side energy storage network, one end of the first bridge arm and one end of the second bridge arm are simultaneously connected to the first external positive end, the other end of the primary-side energy storage network, the other end of the first bridge arm and the other end of the second bridge arm are simultaneously connected to the first external negative end, one end of the resonant inductor is simultaneously connected to the midpoint of the first bridge arm and one end of the auxiliary capacitor, the other end of the resonant inductor is connected to one end of the first resonant capacitor, the other end of the first resonant capacitor is simultaneously connected to one end of the second resonant capacitor and one end of the primary winding of the transformer, and the other end of the second resonant capacitor is simultaneously connected to the other end of the primary winding of the transformer, the other end of the auxiliary capacitor and the midpoint of the second bridge arm; The secondary-side circuit includes a secondary-side energy storage network and a secondary-side switch network; the secondary-side switch network includes a third bridge arm and a fourth bridge arm connected in parallel; one end of the secondary-side energy storage network, one end of the third bridge arm, and one end of the fourth bridge arm are simultaneously connected to the second external positive end, the other end of the secondary-side energy storage network, the other end of the third bridge arm, and the other end of the fourth bridge arm are simultaneously connected to the second external negative end, the midpoint of the third bridge arm is connected to one end of the secondary winding of the transformer, and the midpoint of the fourth bridge arm is connected to the other end of the secondary winding of the transformer.

2. The resonant converter according to claim 1, wherein: The capacitance of the auxiliary capacitor is equal to the capacitance of the second resonant capacitor.

3. The resonant converter according to claim 1, wherein: The switch tubes in the primary-side switch network and the secondary-side switch network are all N-MOS tubes or all IGBTs.

4. The resonant converter according to claim 1, wherein: When the resonant converter is in an operating mode in which energy flows from the primary side to the secondary side, the voltage across the auxiliary capacitor is clamped by the voltage between the midpoint of the first bridge arm and the midpoint of the second bridge arm, and does not participate in resonance. A resonant network is formed by the resonant inductor, the first resonant capacitor, and the second resonant capacitor.

5. The resonant converter according to claim 1, wherein: When the resonant converter is in an operating mode in which energy flows from the secondary side to the primary side, the voltage across the second resonant capacitor is clamped by the voltage across the primary winding of the transformer and does not participate in the resonance. A resonant network is formed by the resonant inductor, the first resonant capacitor and the auxiliary capacitor.

6. The resonant converter according to claim 1, wherein: When the resonant converter operates bidirectionally: the driving signals of the two switch tubes on the first diagonal of the two bridge arms in the inverter side switch network are the first driving signals, and the driving signals of the two switch tubes on the second diagonal are the second driving signals, and the first driving signal and the second driving signal are complementary; the driving signals of the two switch tubes on the first diagonal of the two bridge arms in the rectifier side switch network are the third driving signals, and the driving signals of the two switch tubes on the second diagonal are the fourth driving signals, and the third driving signal and the fourth driving signal are complementary; when the resonant converter is in an operating mode in which energy flows from the primary side to the secondary side, the primary side switch network is the inverter side switch network, and the secondary side switch network is the rectifier side switch network; when the resonant converter is in an operating mode in which energy flows from the secondary side to the primary side, the secondary side switch network is the inverter side switch network, and the primary side switch network is the rectifier side switch network.

7. The resonant converter according to claim 6, wherein: The duty cycles of the first driving signal and the second driving signal are both less than 50%, and both have a certain dead time.

8. The resonant converter according to claim 6, wherein: The duty cycles of the third driving signal and the fourth driving signal are both less than 50%, and the on-pulse width is adjusted in real time according to the power output by the resonant converter.

9. The resonant converter according to claim 1, wherein: The primary-side energy storage network and / or the secondary-side energy storage network include capacitors.

10. A switching power supply, characterized in that: The resonant converter comprises the resonant converter according to any one of claims 1 to 9.

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