A clamped resonant circuit and converter

Abstract

The application discloses a clamp resonant circuit and a converter, which are used for reducing the problem of failure of the converter in overload or short circuit in the prior art. The clamp resonant circuit comprises a first resonant inductor, a second resonant inductor, a resonant capacitor and a clamp switching unit. The first resonant inductor is connected with the resonant capacitor in series to form a first branch. The second resonant inductor is connected with the clamp switching unit to form a second branch. The second branch is connected in parallel across the resonant capacitor. When the voltage across the resonant capacitor is greater than or equal to a preset value, the clamp switching unit can turn on the second branch. When the current flowing through the resonant capacitor is too large, the clamp switching unit acts to connect the second resonant inductor in parallel across the resonant capacitor, so that the resonant impedance changes from small to large, and the current flowing through the resonant cavity can be reduced, and the risk of overload or short circuit failure can be reduced.

Description

Technical Field

[0001] This invention relates to the field of circuit technology, and in particular to a clamped resonant circuit and converter. Background Technology

[0002] Resonant circuit converters are commonly used converter circuits in the field of power electronics. A typical resonant circuit converter is the LLC resonant circuit converter. Its basic principle is: the resonant cavity unit is composed of LC elements and connected in series between the chopper circuit and the rectifier circuit to realize soft switching of the high-frequency switching devices in the chopper circuit and the rectifier circuit, thereby reducing switching losses.

[0003] The typical failure modes of resonant circuits are overload and short-circuit failures. This is because under overload and short-circuit conditions, the current in the resonant cavity is many times larger than during normal operation, and the chopper and rectifier circuits lose their soft-switching conditions and are in a hard-turn-off state. Common protection methods include adjusting the switching frequency to deviate from the resonant frequency of the LLC resonant circuit after a short circuit is detected, or implementing waveform blocking protection. However, these measures are implemented only after a short circuit has occurred and been identified, making them delayed measures. In reality, the MOSFET often fails due to a short circuit before the system has even detected it.

[0004] Existing clamping protection circuits place the clamping device on a common circuit, thus reducing the number of clamping devices required. During each high-frequency resonant cycle, this circuit clamps the voltage across the resonant capacitor using the clamping device. When the voltage across the resonant capacitor reaches the operating voltage of the clamping device, the capacitor voltage remains constant, and current transfers to the clamping device. This alters the impedance of the resonant circuit, limiting the uncontrolled increase of current in the resonant cavity. This protection mechanism activates the clamping device the instant a short circuit occurs, as long as the current in the resonant cavity increases to a certain level; it is hardware protection and can be considered a real-time protection measure. However, after each high-frequency resonant cycle, the chopper circuit still needs to interrupt a significant short-circuit current. The aforementioned protection method only limits the short-circuit current; compared to the interruption current under normal operating conditions, it is still a hard interruption, and the interruption stress remains high, meaning the risk of failure still exists.

[0005] If the short-circuit shutdown current of the LLC can be controlled to not exceed the full-load shutdown current, or even be smaller than the full-load shutdown current, then the short-circuit failure can be completely avoided. However, there is no solution in the existing technology that can reduce the short-circuit shutdown current of the LLC to be less than the full-load shutdown current. Summary of the Invention

[0006] This invention provides a clamped resonant circuit and converter to reduce the problem of converter failure under overload or short circuit conditions in the prior art.

[0007] In a first aspect, the present invention provides a clamping resonant circuit for use in a converter, the circuit comprising: a first resonant inductor, a second resonant inductor, a resonant capacitor, and a clamping switching unit;

[0008] The first resonant inductor and the resonant capacitor are connected in series to form the first branch;

[0009] The second resonant inductor is connected to the clamping switching unit to form the second branch;

[0010] The second branch is connected in parallel across the resonant capacitor;

[0011] The clamping switching unit is used to turn on the second branch when the voltage across the resonant capacitor is greater than or equal to a preset value.

[0012] In one possible implementation, the clamping switching unit includes one or a combination of at least two of a transient voltage suppressor diode, a Zener diode, and a varistor connected in parallel or in series.

[0013] In one possible implementation, the clamping switching unit includes a first controllable switching device and a voltage detection device;

[0014] The first terminal of the first controllable switching device is connected to the first terminal of the voltage detection device and the first terminal of the resonant capacitor, the second terminal of the first controllable switching device is connected to the second resonant inductor, and the control terminal of the first controllable switching device is connected to the control terminal of the voltage detection device.

[0015] The second terminal of the voltage detection device is connected to the second terminal of the resonant capacitor;

[0016] The voltage detection device is used to control the first controllable switching device to turn on when it detects that the voltage across the resonant capacitor is greater than a first threshold, and to control the first controllable switching device to turn off when it detects that the voltage across the resonant capacitor is less than or equal to the first threshold.

[0017] In one possible implementation, the clamping switching unit includes a second controllable switching device and a current sensing device;

[0018] The first terminal of the second controllable switching device is connected to the first terminal of the current sensing device and the first resonant inductor, respectively; the second terminal of the second controllable switching device is connected to the second resonant inductor; and the control terminal of the second controllable switching device is connected to the control terminal of the current sensing device.

[0019] The second terminal of the current sensing device is connected to the resonant capacitor;

[0020] The current detection device is used to control the second controllable switching device to turn on when it detects that the current flowing through the resonant capacitor is greater than the second threshold, and to control the second controllable switching device to turn off when it detects that the current flowing through the resonant capacitor is less than or equal to the second threshold.

[0021] In one possible implementation, the inductance value of the first resonant inductor is the same as the inductance value of the second resonant inductor.

[0022] In a second aspect, the present invention provides a converter, comprising a DC source, a chopper circuit, a rectifier circuit, and a clamping resonant circuit as described in any of the first aspects, wherein,

[0023] The DC source, the rectifier circuit, the clamping resonant circuit, and the rectifier circuit are connected in sequence;

[0024] The chopper circuit is either a full-bridge chopper circuit or a half-bridge chopper circuit, wherein...

[0025] The full-bridge chopper circuit includes a first switch, a second switch, a third switch, and a fourth switch. The first switch and the second switch are connected in series to form a first bridge arm, and the third switch and the fourth switch are connected in series to form a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel.

[0026] The half-bridge chopper circuit includes a fifth switch and a sixth switch, which are connected in series to form a third bridge arm;

[0027] The rectifier circuit is either a full-bridge rectifier circuit or a full-wave rectifier circuit, wherein...

[0028] The full-bridge rectifier circuit includes a first transformer, a seventh switch, an eighth switch, a ninth switch, and a tenth switch. The seventh switch and the eighth switch are connected in series to form a fourth bridge arm, and the ninth switch and the tenth switch are connected in series to form a fifth bridge arm. The fourth bridge arm and the fifth bridge arm are connected in parallel and connected to the first terminal and the second terminal of the first transformer.

[0029] The full-wave rectifier circuit includes a second transformer, an eleventh switch, and a twelfth switch. The eleventh switch and the twelfth switch are connected in series to form a sixth bridge arm, which is connected in parallel with the secondary side of the second transformer.

[0030] In one possible implementation, the chopper circuit is a full-bridge chopper circuit, the rectifier circuit is a full-bridge rectifier circuit, and the clamping resonant circuit includes a first clamping resonant circuit, wherein...

[0031] The positive terminal of the DC source is connected to one end of the full-bridge chopper circuit, and the negative terminal of the DC source is connected to the other end of the full-bridge chopper circuit.

[0032] The primary side of the first transformer is connected between the first resonant inductor and the resonant capacitor in the first clamped resonant circuit, and the secondary side of the first transformer is connected between the midpoint of the fourth bridge arm and the midpoint of the fifth bridge arm.

[0033] One end of the series connection of the first resonant inductor, the primary side of the first voltage transformer, and the resonant capacitor in the first clamping resonant circuit is connected to the midpoint of the first bridge arm, and the other end of the series connection is connected to the midpoint of the second bridge arm.

[0034] In one possible implementation, a second clamping resonant circuit is also included;

[0035] The secondary side of the first transformer is connected between the first resonant inductor and the resonant capacitor in the second clamping resonant circuit.

[0036] One end of the series connection of the resonant capacitor in the second clamping resonant circuit, the secondary side of the first transformer, and the resonant capacitor in the second clamping resonant circuit is connected to the midpoint of the fourth bridge arm, and the other end of the series connection is connected to the midpoint of the fifth bridge arm.

[0037] In one possible implementation, the chopper circuit is a half-bridge chopper circuit, and the rectifier circuit is a full-bridge rectifier circuit.

[0038] The resonant capacitor includes a first sub-resonant capacitor and a second sub-resonant capacitor. The clamping switching unit includes a first sub-clamping switching unit and a second sub-clamping switching unit. The first sub-resonant capacitor and the second sub-resonant capacitor are connected in series to form a seventh bridge arm. One end of the first sub-clamping switching unit is connected to one end of the seventh bridge arm, and one end of the second sub-clamping switching unit is connected to the other end of the seventh bridge arm. The second resonant inductor is connected between the other end of the first sub-clamping switching unit, the other end of the second sub-clamping switching unit, and the midpoint of the seventh bridge arm.

[0039] The third bridge arm and the seventh bridge arm are connected in parallel and then connected to the positive and negative terminals of the DC source.

[0040] The secondary side of the first transformer is connected between the midpoint of the fourth bridge arm and the midpoint of the fifth bridge arm.

[0041] In one possible implementation, the second resonant inductor is a single-winding inductor; one end of the second resonant inductor is connected to the other end of the first sub-clamping switching unit and the other end of the second sub-clamping switching unit, and the other end of the second resonant inductor is connected to the midpoint of the seventh bridge arm;

[0042] The second resonant inductor is a dual-winding inductor; the first winding of the second resonant inductor is connected between the other end of the first sub-clamping switching unit and the midpoint of the seventh bridge arm, and the second winding of the second resonant inductor is connected between the seventh bridge arm and the other end of the second sub-clamping switching unit.

[0043] In one possible implementation, the chopper circuit is a half-bridge chopper circuit, and the rectifier circuit is a full-wave rectifier circuit.

[0044] The resonant capacitor includes a third sub-resonant capacitor and a fourth sub-resonant capacitor; the second resonant inductor includes a first sub-resonant inductor and a second sub-resonant inductor; the clamping switching unit includes a third sub-clamping switching unit and a fourth sub-clamping switching unit; the third sub-resonant capacitor and the fourth sub-resonant capacitor are connected in series to form an eighth bridge arm; the first sub-resonant inductor is connected in series with the third sub-clamping switching unit and then connected in parallel across the third sub-resonant capacitor; the second sub-resonant inductor is connected in series with the fourth sub-clamping switching unit and then connected in parallel across the fourth sub-resonant capacitor; the first resonant inductor is connected between the midpoint of the third bridge arm and the first end of the primary side of the second transformer.

[0045] One end of the third bridge arm is connected to the positive terminal of the DC source, and the other end of the third bridge arm is connected to the negative terminal of the DC source.

[0046] The beneficial effects of this invention are as follows:

[0047] The clamping resonant circuit and converter disclosed in this invention include a first resonant inductor, a second resonant inductor, a resonant capacitor, and a clamping switching unit. The first resonant inductor and the resonant capacitor are connected in series to form a first branch. The second resonant inductor is connected to the clamping switching unit to form a second branch. The second branch is connected in parallel across the resonant capacitor. Since the clamping switching unit can conduct the second branch when the voltage across the resonant capacitor is greater than or equal to a preset value, that is, when the current flowing through the resonant capacitor is too large, the clamping switching component operates, connecting the second resonant inductor in parallel across the resonant capacitor, so that the resonant impedance changes from small to large, thereby reducing the current flowing through the resonant cavity and reducing the risk of overload or short circuit failure. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1A schematic diagram of a clamping resonant circuit provided in an embodiment of the present invention;

[0050] Figure 2 An equivalent schematic diagram of a clamping resonant circuit provided in an embodiment of the present invention;

[0051] Figure 3 An equivalent schematic diagram of another clamping resonant circuit provided in an embodiment of the present invention;

[0052] Figure 4 Impedance curve of the equivalent circuit of the clamping resonant circuit provided in the embodiment of the present invention;

[0053] Figure 5a A schematic diagram of the phase curve of an equivalent circuit of a clamping resonant circuit provided in an embodiment of the present invention;

[0054] Figure 5b A schematic diagram of the phase curve of another equivalent circuit of the clamping resonant circuit provided in an embodiment of the present invention;

[0055] Figure 6 A schematic diagram of another clamping resonant circuit provided in an embodiment of the present invention;

[0056] Figure 7 A schematic diagram of another clamping resonant circuit provided in an embodiment of the present invention;

[0057] Figure 8 A schematic diagram of another clamping resonant circuit provided in an embodiment of the present invention;

[0058] Figure 9 A schematic diagram of another clamping resonant circuit provided in an embodiment of the present invention;

[0059] Figure 10 A schematic diagram of a converter provided in an embodiment of the present invention;

[0060] Figure 11 This is a schematic diagram of another converter structure provided in an embodiment of the present invention;

[0061] Figure 12 A circuit structure diagram of a converter provided for related technologies;

[0062] Figure 13a A schematic diagram of the current curve of the resonant cavity when the converter changes from normal operation to overload or short circuit, as provided in an embodiment of the present invention;

[0063] Figure 13b This is a schematic diagram of the switching drive waveform of the converter provided in an embodiment of the present invention;

[0064] Figure 13cA schematic diagram of the output current curve of the converter provided in an embodiment of the present invention;

[0065] Figure 14 This is a schematic diagram of another converter structure provided in an embodiment of the present invention;

[0066] Figure 15 This is a schematic diagram of another converter structure provided in an embodiment of the present invention;

[0067] Figure 16 This is a schematic diagram of another converter structure provided in an embodiment of the present invention;

[0068] Figure 17 This is a schematic diagram of another converter provided in an embodiment of the present invention. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0070] To reduce the risk of converter failure under overload or short circuit conditions in the prior art, embodiments of the present invention provide a clamped resonant circuit and a converter. The clamped resonant circuit and converter provided in the embodiments of the present invention will be described in detail below.

[0071] like Figure 1 As shown, a clamping resonant circuit provided in an embodiment of the present invention is applied to a converter. The clamping resonant circuit includes a first resonant inductor L1, a second resonant inductor L2, a resonant capacitor C, and a clamping switching unit 11.

[0072] The first resonant inductor L1 is connected in series with the resonant capacitor C to form the first branch;

[0073] The second resonant inductor L2 is connected to the clamping switching unit 11 to form the second branch;

[0074] The second branch is connected in parallel across the resonant capacitor C;

[0075] The clamping switching unit 11 is used to turn on the second branch when the voltage across the resonant capacitor C is greater than or equal to a preset value.

[0076] The clamping resonant circuit disclosed in this embodiment of the invention has a first resonant inductor connected in series with a resonant capacitor to form a first branch, and a second resonant inductor connected to a clamping switching unit to form a second branch. The second branch is connected in parallel across the resonant capacitor. Since the clamping switching unit can conduct the second branch when the voltage across the resonant capacitor is greater than or equal to a preset value, that is, when the current flowing through the resonant capacitor is too large, the clamping switching component operates, connecting the second resonant inductor in parallel across the resonant capacitor, so that the resonant impedance changes from small to large, thereby reducing the current flowing through the resonant cavity and reducing the risk of overload or short circuit failure.

[0077] In practice, if the clamping switching unit does not operate, i.e., is in a disconnected state, Figure 1 The clamping resonant circuit shown can be equivalent to... Figure 1 The LC resonant circuit shown includes a resonant inductor L1 and a resonant capacitor C connected in series. The impedance of this LC resonant circuit is infinitesimally small at the resonant frequency and increases as it deviates from the resonant frequency. Utilizing this characteristic, the LC resonant circuit is connected in parallel in a converter to form a resonant converter. This allows for soft-switching of the switching transistors in the converter. Furthermore, due to the impedance changing with frequency, the resonant converter typically operates in frequency modulation mode. By changing the impedance of the resonant circuit, the output voltage of the converter can be adjusted.

[0078] When the voltage across the resonant capacitor C is greater than or equal to a preset value, i.e., when the current flowing through the resonant capacitor reaches a certain value, the clamping switching unit is turned on, causing the second resonant inductor C2 to be connected in parallel with the circuit. Figure 1 The clamping resonant circuit shown can be equivalent to... Figure 2 The LLC resonant circuit shown includes resonant inductors L1 and L3, and a resonant capacitor C. Resonant inductor L3 is connected in parallel across resonant capacitor C. The LLC resonant circuit has the highest impedance at the resonant frequency and the impedance decreases as it deviates from the resonant frequency.

[0079] like Figure 4 As shown, Figure 2 and Figure 3 Impedance curves of two resonant circuits, where the horizontal axis represents frequency and the vertical axis represents impedance. Figure 2 The impedance of the resonant circuit shown is represented by the right side of the vertical axis. Figure 3 The impedance of the resonant circuit shown is represented by the solid line. Figure 2 The impedance curve of the resonant circuit shown is represented by the dashed line. Figure 3The impedance curve of the resonant circuit shown in the figure reveals that at the resonant frequency, the impedances of the two resonant circuits and their changing trends are completely opposite. It should be noted that, for ease of representation, the horizontal axis of the curve uses the normalized frequency, which is the actual frequency divided by the natural resonant frequency composed of the capacitor and inductor. It is clearly visible from the curve that the impedance curve reaches its maximum or minimum value at the natural resonant frequency (normalized frequency = 1).

[0080] Based on the above analysis, combined with Figure 1 The clamping resonant circuit shown is a normal LC resonant circuit when it is working properly. Figure 2 In the resonant circuit shown, when the current flowing through the resonant element is too large, the clamping switching component activates, switching the second resonant inductor into the circuit, thus forming a second mode of resonant circuit. Figure 3 The resonant circuit shown is composed of Figure 2 The resonant circuit shown is switched to Figure 3 The resonant circuit shown reduces the current flowing through the resonant cavity because the resonant impedance changes from small to large. Furthermore, adding the second resonant inductor L2 also changes the phase of the resonant cavity, as shown... Figure 5a and Figure 5b As shown, Figure 5a for Figure 2 The resonant circuit shown and Figure 3 The amplitude-frequency response curve of the resonant circuit is shown, where curve 1 represents... Figure 2 The amplitude-frequency response curve of the resonant circuit shown is illustrated in curve 2, which represents... Figure 3 The amplitude-frequency response curve of the resonant circuit shown is as follows: Figure 5b for Figure 2 The resonant circuit shown and Figure 3 The phase-frequency response curves of the resonant circuit shown are given, where curve 3 is... Figure 2 The phase-frequency response curve of the resonant circuit shown is curve 4. Figure 3 The phase-frequency response curve of the resonant circuit shown is from... Figure 5a and Figure 5b As can be seen from this, at the resonant frequency point, Figure 2 The phase of the resonant circuit shown is 45 degrees. Figure 3 The phase of the resonant circuit shown crosses from -90 degrees to +90 degrees. That is, if the clamping resonant circuit provided in this embodiment of the invention is applied to a resonant converter, changing the operating frequency to be higher or lower than the resonant frequency of the resonant circuit can change the phase of the resonant current. This creates conditions for reducing the turn-off current of the switching transistor under overload or short-circuit conditions. The amplitude of the turn-off current can be reduced by changing the phase of the turn-off current.

[0081] The clamping switching unit in the embodiments of the present invention may include one or a combination of at least two of the transient suppression diode, Zener diode and varistor connected in parallel or in series, as described below with specific embodiments.

[0082] like Figure 6 The diagram shown is a schematic of a clamping resonant circuit provided in an embodiment of the present invention. Figure 6 As can be seen, the clamping switching unit 11 includes two transient suppression diodes D1 and D2 connected in series.

[0083] A TVS (Transient Voltage Suppressor) is a widely used, high-efficiency circuit protection device with extremely fast response time and high surge absorption capability. When its terminals are subjected to a sudden high-energy surge, the TVS can rapidly change its impedance from high to low to absorb a large instantaneous current, clamping the voltage across its terminals to a predetermined value, thereby protecting downstream circuit components from transient high-voltage spikes. Therefore, in this embodiment of the invention, the TVS can be used as a clamping switching component. When the voltage across the resonant capacitor exceeds the operating voltage of the TVS, the TVS breaks down and maintains the voltage across its terminals at the clamping voltage, allowing a larger surge current to pass through. Figure 6 As shown, clamping switching can be achieved by connecting two TVS devices in reverse series or by using a single bidirectional TVS device. When the voltage across the resonant capacitor exceeds the clamping voltage of the TVS, the TVS conducts, connecting the second resonant inductor L2 in parallel across the resonant capacitor C.

[0084] A Zener diode, also known as a Zener rectifier diode, utilizes the reverse breakdown state of a PN junction, where the current can vary over a wide range while the voltage remains essentially constant. A diode is a semiconductor device with high resistance until a critical reverse breakdown voltage is reached. At the critical breakdown point, the reverse resistance drops to a very small value. In the low-resistance region, the current increases, but the voltage remains constant. Zener diodes are categorized based on their breakdown voltage. Due to this characteristic, Zener diodes are primarily used as voltage regulators or reference voltage elements. Zener diodes can be connected in series to operate at higher voltages, thus achieving a higher stable voltage. In this embodiment of the invention, the Zener diode is used as a switching component. When the voltage across the resonant capacitor equals the operating voltage of the Zener diode, the Zener diode breaks down and maintains a clamping voltage across it, reducing the reverse resistance to a very small value and allowing a larger current to pass through.

[0085] A VDR (Voltage-Dependent Resistor) is a resistive device with nonlinear current-voltage characteristics. A VDR can clamp the voltage when a circuit experiences overvoltage, absorbing excess current to protect sensitive components. A VDR is a voltage-limiting protection device; utilizing its nonlinear characteristics, when an overvoltage occurs across the VDR, it can clamp the voltage to a relatively fixed value, thereby protecting downstream circuits. In this embodiment of the invention, the VDR is also used as a clamping switching component. When the voltage across the resonant capacitor exceeds the VDR's operating voltage, the VDR's impedance decreases, allowing a larger current to pass through.

[0086] In implementation, besides simply using the same TVS, Zener, and VDR in series or parallel, diodes, TVS, Zener, and VDR, or combinations of one or more of them in series or parallel, can also be used. For example... Figure 7 As shown, the clamping switching unit 11 is composed of two diodes D3 and D6, two TVS diodes D4 and D5, and a magnetically coupled second resonant inductor L2, which can achieve clamping with different voltages across the resonant capacitor. When the clamping voltages of the two TVS diodes are the same, the voltage across the resonant capacitor C reaches the clamping voltage of the TVS diodes, and the magnetically coupled second resonant inductor L2 is connected in parallel across the resonant capacitor C. When the clamping voltages of the two TVS diodes are different, and the voltage across the resonant capacitor C reaches the clamping voltage of the TVS diodes respectively, the magnetically coupled second resonant inductor L2 is connected in parallel across the resonant capacitor C. This embodiment of the invention, through two discrete clamping switching components, can achieve a more flexible connection of the second resonant inductor L2 in parallel with the resonant capacitor C.

[0087] In one embodiment, the clamping switching unit 11 of the present invention may further include a first controllable switching device and a voltage detection device. The voltage detection device detects the voltage across the resonant capacitor C. When the voltage across the resonant capacitor C is greater than a first threshold, the controllable switching device is turned on; when it is not greater than the first threshold, the controllable switching device is turned off.

[0088] like Figure 8 The diagram shown is a structural schematic of a clamping resonant circuit provided in an embodiment of the present invention. Figure 8As can be seen from the diagram, the clamping switching unit 11 includes a first controllable switching device 1011 and a voltage detection device 1012. The first terminal of the first controllable switching device 1011 is connected to the first terminal of the voltage detection device 1012 and the first terminal of the resonant capacitor C, respectively. The second terminal of the first controllable switching device 1011 is connected to the second resonant inductor L2. The control terminal of the first controllable switching device 1011 is connected to the control terminal of the voltage detection device 1012. The second terminal of the voltage detection device 1012 is connected to the second terminal of the resonant capacitor C. When the voltage detection device 1012 detects that the voltage across the resonant capacitor C is greater than a first threshold, it controls the first controllable switching device 1011 to turn on. When it detects that the voltage across the resonant capacitor C is less than or equal to the first threshold, it controls the first controllable switching device 1011 to turn off.

[0089] The voltage detection device 1012 in this embodiment of the invention can be implemented by a specific hardware functional circuit. For example, after voltage division by resistors, it can be compared with a pre-set threshold by a comparator to send high and low level signals. Alternatively, the voltage across the resonant capacitor can be collected by an intelligent processing unit, and then a drive can be sent after calculation to drive the controllable switching device to close, thereby effectively connecting the second resonant inductor in parallel across the resonant capacitor.

[0090] In one embodiment, the clamping switching unit 11 of the present invention may further include a second controllable switching device and a current detection device; the current detection element detects the current flowing through the resonant capacitor C, and when the current is greater than a second threshold, the controllable switching device is turned on, and when the current is not greater than the second threshold, the controllable switching device is turned off.

[0091] like Figure 9 The diagram shown is a schematic of a clamping resonant circuit provided in an embodiment of the present invention. Figure 9 As can be seen from the diagram, the clamping switching unit 11 includes a second controllable switching device 1013 and a current detection device 1014. The first terminal of the second controllable switching device 1013 is connected to the first terminal of the current detection device 1014 and the first resonant inductor L1, respectively. The second terminal of the second controllable switching device 1013 is connected to the second resonant inductor L2. The control terminal of the second controllable switching device 1013 is connected to the control terminal of the current detection device 1014. The second terminal of the current detection device 1014 is connected to the resonant capacitor C.

[0092] The current detection device 1014 is used to control the second controllable switching device 1013 to turn on when it detects that the current flowing through the resonant capacitor C is greater than the second threshold, and to control the second controllable switching device 1013 to turn off when it detects that the current flowing through the resonant capacitor C is less than or equal to the second threshold.

[0093] In this embodiment of the invention, the current detection element can be detected by current sensors such as Hall effect sensors and current transformers, or by a smart processing unit that collects the voltage across the resonant capacitor, and then sends a drive after calculation to drive the controllable switching device to close, thereby effectively connecting the second resonant inductor in parallel across the resonant capacitor.

[0094] The clamping resonant circuit disclosed in this embodiment of the invention has two resonant frequency points. The first resonant frequency point is formed by the second resonant inductor L2 and the resonant capacitor C. The second resonant frequency point is formed by the equivalent resonant inductance formed by the parallel connection of the first resonant inductor L1 and the second resonant inductor L2, and the resonant capacitor C. The inductance of the second resonant inductor L2 can be the same as that of the first resonant inductor L1. When the clamping switching unit switches the second resonant inductor L2 to be connected in parallel across the resonant capacitor C, the resonant frequency points of the entire circuit remain consistent, but the impedance characteristics are exactly opposite.

[0095] Based on the same inventive concept, this embodiment of the invention also provides a converter, which solves the problem in the same way as the clamped resonant circuit, and the repeated parts will not be described again.

[0096] like Figure 10 The diagram shown is a schematic representation of a converter according to an embodiment of the present invention. The converter includes a DC source, a chopper circuit 101, a rectifier circuit 102, and a clamping resonant circuit 103 as described in any of the above embodiments.

[0097] The DC power source DC, the chopper circuit 101, the clamping resonant circuit 103, and the rectifier circuit 102 are connected in sequence.

[0098] In specific implementation, such as Figure 11 , Figure 12 , Figure 14-15 As shown, the chopper circuit 101 can be a full-bridge chopper circuit or a half-bridge chopper circuit, and the rectifier circuit 102 can be a full-bridge rectifier circuit or a full-wave rectifier circuit.

[0099] The full-bridge chopper circuit may include a first switch S1, a second switch S2, a third switch S3 and a fourth switch S4. The first switch S1 and the second switch S2 are connected in series to form the first bridge arm, the third switch S3 and the fourth switch S4 are connected in series to form the second bridge arm, and the first bridge arm and the second bridge arm are connected in parallel.

[0100] The half-bridge chopper circuit may include a fifth switch S5 and a sixth switch S6, which are connected in series to form the third bridge arm;

[0101] The full-bridge rectifier circuit may include a first transformer T1, a seventh switch S7, an eighth switch S8, a ninth switch S9, and a tenth switch S10. The seventh switch S7 and the eighth switch S8 are connected in series to form the fourth bridge arm, and the ninth switch S9 and the tenth switch S10 are connected in series to form the fifth bridge arm. The fourth bridge arm and the fifth bridge arm are connected in parallel and connected to the first terminal and the second terminal of the first transformer T1.

[0102] The full-wave rectifier circuit may include a second transformer T2, an eleventh switch S11 and a twelfth switch S12. The eleventh switch S11 and the twelfth switch S12 are connected in series to form the sixth bridge arm, and the sixth bridge arm is connected in parallel with the secondary side of the second transformer T2.

[0103] In this embodiment of the invention, the chopper circuit chops the DC power supply into a high-frequency AC output waveform. After impedance transformation by the clamping resonant circuit, the amplitude of the AC output waveform is changed. Finally, the rectifier circuit outputs a DC waveform with adjustable voltage.

[0104] For ease of understanding, the converter provided in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0105] like Figure 11 The diagram shown is a structural schematic of a converter provided in an embodiment of the present invention. Figure 11 As can be seen from the diagram, the converter includes a DC source DC, a full-bridge chopper circuit 1101, a first clamping resonant circuit 1103, and a full-bridge rectifier circuit 1102.

[0106] The positive terminal of the DC source is connected to one end of the full-bridge chopper circuit 1101, and the negative terminal of the DC source is connected to the other end of the full-bridge chopper circuit 1101.

[0107] The primary side of the first transformer T1 is connected between the first resonant inductor L3 and the resonant capacitor C1 in the first clamping resonant circuit 1103, and the secondary side of the first transformer T1 is connected between the midpoint of the fourth bridge arm and the midpoint of the fifth bridge arm.

[0108] One end of the series connection of the first resonant inductor L3, the primary side of the first voltage transformer T1, and the resonant capacitor C1 in the first clamping resonant circuit 1103 is connected to the midpoint of the first bridge arm, and the other end of the series connection is connected to the midpoint of the second bridge arm.

[0109] In this embodiment of the invention, the clamping switching unit in the first clamping resonant circuit 1103 is composed of a bidirectional transient suppression diode TVS1, the first resonant inductor L3 and the resonant capacitor C1 are connected in series through the primary side of the first transformer T1, the second resonant inductor L4 and the bidirectional transient suppression diode TVS1 are connected in series, and after being connected in series, they are connected in parallel with the resonant capacitor C1.

[0110] The full-bridge rectifier circuit is a transformer-isolated full-bridge rectifier circuit. The first transformer T1 includes a primary side and a secondary side. The primary side of the first transformer T1 is connected in series in the first clamping resonant circuit 1103. The secondary side of the first transformer T1 is connected to the midpoint of the fourth bridge arm and the midpoint of the fifth bridge arm, respectively.

[0111] The embodiments of the present invention will be described below in conjunction with resonant converters in related technologies.

[0112] like Figure 12 As shown, a circuit structure diagram of a converter provided in related technologies is presented. Figure 12 As can be seen, the converter limits the unlimited increase of current in the resonant cavity under overload or short circuit by connecting a bidirectional transient suppression diode TVS2 in parallel with the resonant capacitor C2. However, when the switching transistor in the chopper circuit is turned off, there will be a large turn-off current. At this time, the large current causes the switching device to be hard turned off, which will lead to converter failure.

[0113] Embodiments of the present invention, such as Figure 11 As shown, by connecting a clamping circuit consisting of a bidirectional transient suppression diode TVS1 and a second resonant inductor L4 in series in parallel with the resonant capacitor C1, when the converter is overloaded or short-circuited, and the voltage across the resonant capacitor C1 exceeds the operating voltage of the bidirectional transient suppression diode TVS1, the resonant cavity circuit changes from a normal LC series resonant circuit to a new type of resonant circuit consisting of a first resonant inductor L3, a second resonant inductor L4, and a resonant capacitor C1. At this time, the current amplitude of the resonant cavity can be reduced by the change in the impedance of the resonant cavity, and the current of the resonant cavity will also show a phase shift. When the switching transistor is turned off, the current of the resonant cavity has dropped to near zero, thereby realizing soft switching turn-off.

[0114] like Figure 13a The figure shows the current curve of the resonant cavity when the converter changes from normal operation to overload or short circuit. Figure 13a In the middle, curve 5 is Figure 12 The current curve of the resonant cavity in the converter shown under overload is corresponding to... Figure 2 The resonant circuit shown in Figure 6 has curve 6. Figure 11 The current curve of the resonant cavity in the converter shown under overload is corresponding to... Figure 3 The resonant circuit shown;

[0115] Figure 13b This is a schematic diagram of the switching drive waveform of the converter, where the duty cycle of the drive signal is 50%.

[0116] Figure 13c This is a schematic diagram of the converter's output current curve, where curve 7 is... Figure 12 The current curve shown is the output current curve of the converter, which uses... Figure 2The resonant circuit shown in Figure 8 is... Figure 11 The current curve shown is the output current curve of the converter, which uses... Figure 3 The resonant circuit shown.

[0117] from Figure 13a , Figure 13b and Figure 13c As can be seen, under normal operation, the current in the resonant cavity of the two converters is the same, but when overloaded or short-circuited, the current in the resonant cavity shows a significant difference.

[0118] from Figure 13a , Figure 13b and Figure 13c As can be seen, after overload or short circuit, the current in the resonant cavity of the converter provided in this embodiment of the invention is basically at the zero-crossing point at each switching on and off moment. It can achieve soft switching not only under normal operating conditions, but also under overload or short circuit conditions, thereby solving the risk of converter failure under overload or short circuit.

[0119] It should be noted that, Figure 13a , Figure 13b and Figure 13c For illustration purposes only, to show Figure 11 and Figure 12 The curves corresponding to the two converters when the two circuits change from normal operation to overload are compared. Therefore, the units of the horizontal and vertical axes are not shown, and the embodiments of the present invention do not limit this.

[0120] In one embodiment, such as Figure 14 The diagram shown is a circuit schematic of a converter provided in an embodiment of the present invention. This converter is... Figure 11 Based on the converter shown, a second clamping resonant circuit 1501 is added. The second clamping resonant circuit 1501 includes a first resonant inductor L6, a second resonant inductor L7, a resonant capacitor C3, and a bidirectional transient voltage suppressor diode TVS3. The second resonant inductor L7 and the bidirectional transient voltage suppressor diode TVS3 are connected in series and then in parallel with the resonant inductor L3. The first resonant inductor L6 is connected in series through the secondary side of the first transformer T1. Figure 14 As can be seen, the second clamping resonant circuit 1501 is connected between the secondary side of the first transformer T1 and the fourth and fifth bridge arms.

[0121] Specifically, the secondary side of the first transformer T1 is connected between the first resonant inductor L6 and the second resonant capacitor C3 in the second clamping resonant circuit 1501.

[0122] The resonant capacitor C3 in the second clamping resonant circuit 1501, the secondary side of the first transformer T1, and the resonant capacitor C3 in the second clamping resonant circuit 1501 are connected in series. One end of the series connection is connected to the midpoint of the fourth bridge arm, and the other end is connected to the midpoint of the fifth bridge arm.

[0123] The converter provided in this embodiment of the invention has a first clamping resonant circuit 1103 and a second clamping resonant circuit 1501 coupled together through an isolation transformer T1, and connected in series with a full-bridge chopper circuit and a full-bridge rectifier circuit respectively. This enables soft switching of the bidirectional resonant converter in the event of overload or short circuit in either direction, thereby improving the flexibility of the converter.

[0124] In one embodiment, such as Figure 15 The diagram shown is a schematic diagram of the circuit structure of a converter provided in an embodiment of the present invention. Figure 15 As can be seen, the chopper circuit is a half-bridge chopper circuit 1601, including the third bridge arm composed of the fifth switch S9 and the sixth switch S10; the rectifier circuit is a full-bridge rectifier circuit 1602, including the first transformer T1, the seventh switch S5, the eighth switch S6, the ninth switch S7, and the tenth switch S8. The seventh switch S5 and the eighth switch S6 are connected in series to form the fourth bridge arm, and the ninth switch S7 and the tenth switch S8 are connected in series to form the fifth switch; the resonant capacitor in the clamping resonant circuit 103 includes the first sub-resonant capacitor C4 and the second sub-resonant capacitor C5; the clamping switching unit includes the first sub-clamping switching unit and the second sub-clamping switching unit. In this embodiment of the invention, the first sub-clamping switching unit is the first diode D1, and the second sub-clamping switching unit is the second diode D2, wherein:

[0125] The first sub-resonant capacitor C4 and the second sub-resonant capacitor C5 are connected in series to form the seventh bridge arm. The cathode of the first diode D1 is connected to one end of the seventh bridge arm, and the anode of the second diode D2 is connected to the other end of the seventh bridge arm. The second resonant inductor L9 is connected between the other end of the first diode D1, the other end of the second diode D2, and the midpoint of the seventh bridge arm.

[0126] After the third and seventh bridge arms are connected in parallel, the positive and negative terminals of the DC source are connected.

[0127] The secondary side of the first transformer T1 is connected between the midpoint of the fourth bridge arm and the midpoint of the fifth bridge arm.

[0128] like Figure 15 As shown, the second resonant inductor L9 is a single-winding inductor. One end of the second resonant inductor L9 is connected to the anode of the first diode D1 and the cathode of the second diode D2, and the other end of the second resonant inductor L9 is connected to the midpoint of the seventh bridge arm.

[0129] In this embodiment of the invention, the first resonant inductor L8 and the second resonant inductor L9 are shared by the first sub-resonant capacitor C4, the first diode D1, the second sub-resonant capacitor C5, and the second diode D2, thereby reducing the number of components in the circuit.

[0130] In another embodiment, Figure 15 In the publicly disclosed converter, the second resonant inductor L9 can also be a two-winding inductor, such as... Figure 16 The diagram shown is a circuit structure schematic of a converter provided in an embodiment of the present invention. Figure 16 In the clamping resonant circuit 103, the second resonant inductor L10 is a two-winding inductor. The first winding of the second resonant inductor L10 is connected between the anode of the first diode D1 and the midpoint of the seventh bridge arm, and the second winding of the second resonant inductor L10 is connected between the seventh bridge arm and the cathode of the second diode D2.

[0131] In this embodiment of the invention, the first sub-resonant capacitor C4, the first diode D1, and the second sub-resonant capacitor C5 and the second diode D2 share a first resonant inductor L8. The second resonant inductor L10 is a coupling inductor, which includes a first winding inductor and a second winding inductor. Using a coupling inductor can reduce the number of components in the circuit.

[0132] It should be noted that in other embodiments where multiple inductors are used, all multiple inductors can actually become coupled inductors, and the coupled inductors still play the role of inductors in the circuit.

[0133] In one embodiment, such as Figure 17 As shown, the chopper circuit is a half-bridge chopper circuit 1601, and the rectifier circuit is a full-wave rectifier circuit 1801. The full-wave rectifier circuit includes a second transformer T2, an eleventh switch S11, and a twelfth switch S12, wherein the eleventh switch S11 and the twelfth switch S12 form the sixth bridge arm. The resonant capacitors in the second clamping resonant circuit 103 include a third sub-resonant capacitor C6 and a fourth sub-resonant capacitor C7, the second resonant inductor includes a first sub-resonant inductor L11 and a second sub-resonant inductor L12, and the clamping switching unit includes a third sub-clamping switching unit and a fourth sub-clamping switching unit. The fourth clamping switching unit includes a third diode D3 and a first transient suppression diode TVS4. Specifically, the third sub-resonant capacitor C6 and the fourth sub-resonant capacitor C7 are connected in series to form the eighth bridge arm. The first sub-resonant inductor L11 is connected in series with the third sub-clamping switching unit and then connected in parallel across the third sub-resonant capacitor C6. The second sub-resonant inductor L12 is connected in series with the fourth sub-clamping switching unit and then connected in parallel across the fourth sub-resonant capacitor C7. The first resonant inductor L8 is connected between the midpoint of the third bridge arm and the first end of the primary side of the second transformer T2.

[0134] One end of the third bridge arm is connected to the positive terminal of the DC power source, and the other end of the third bridge arm is connected to the negative terminal of the DC power source.

[0135] In this embodiment of the invention, the first sub-resonant inductor L11 is connected in series with the third sub-clamping switching unit, that is, one end of the first sub-resonant inductor L11 is connected to the anode of the third diode D3, the other end of the first sub-resonant inductor L11 is connected to the anode of the first transient suppression diode TVS4, the cathode of the third diode D3 is connected to one end of the third sub-resonant capacitor C6, and the cathode of the first transient suppression diode TVS4 is connected to the other end of the third sub-resonant inductor L6.

[0136] The second sub-resonant inductor L12 is connected in series with the third sub-clamping switching unit. That is, one end of the second sub-resonant inductor L12 is connected to the anode of the fourth diode D4, and the other end of the second sub-resonant inductor L12 is connected to the anode of the second transient suppression diode TVS5. The cathode of the fourth diode D4 is connected to one end of the fourth sub-resonant capacitor C7, and the cathode of the second transient suppression diode TVS5 is connected to the other end of the fourth sub-resonant capacitor C7.

[0137] In this embodiment of the invention, the first sub-resonant inductor L11, the third diode D3, the first transient suppression diode TVS4, the second sub-resonant inductor L12, the fourth diode D4, and the second transient suppression diode TVS5 share a first resonant inductor L13, and the clamping resonant circuit 103 is connected in series between the half-bridge chopper circuit and the full-wave rectifier circuit with transformer isolation.

[0138] The converter provided in this embodiment of the invention can operate in a soft-switching state when overloaded or short-circuited, thereby reducing the risk of failure of the resonant converter due to overload and short circuit.

[0139] It should be noted that in the above embodiments, the first resonant inductors with different designations represent different resonant circuits and do not represent the same inductor. Similarly, the second resonant inductors with different designations represent different resonant circuits and do not represent the same inductor. The resonant capacitors with different designations also represent different resonant circuits and do not represent the same resonant capacitor. The same description applies to other circuit devices with different designations, and will not be repeated here.

[0140] It should be noted that with the development of device integration and packaging technology, multiple functional devices can be integrated into one device, forming a single device with the functions of multiple devices. For example, a diode and a Zener diode can be integrated into a single device through packaging. However, it is not difficult for those skilled in the art to understand that even a device with functions packaged together actually operates according to an equivalent circuit in the circuit. Therefore, the diode and transient suppression diode in this application can be replaced by an integrated device. The above description is only a further detailed explanation of this application in conjunction with specific preferred embodiments, and it should not be considered that the specific embodiments of this application are limited to these descriptions. For those skilled in the art, any substitutions or obvious modifications made without departing from the concept of this application, and with the same function or purpose, should be considered to fall within the protection scope of this application.

[0141] It should be noted that the series and parallel connections in the circuits of the above embodiments are only equivalent relationships and have nothing to do with whether the devices are on the left or right. The accompanying drawings of this embodiment are only a special case drawn according to the description of the embodiment. Any simple circuit modification, as long as it does not violate the series-parallel or equivalent series-parallel connection relationships described in the embodiment, will not affect the scope of protection of this application.

[0142] It should be noted that the accompanying drawings in the above embodiments are only schematic diagrams of the circuit structure. They are only provided for the convenience of understanding this embodiment. Those skilled in the art should understand that the primary side of the transformer has an equivalent magnetizing inductance, and the rectifier on the output side can also have multiple secondary windings. For ordinary converters, the input side of the chopper circuit and the output side of the rectifier circuit usually have filter capacitors. The accompanying drawings of the embodiments are only schematic diagrams of the circuit structure. In order to illustrate the invention of this application, it is impossible to list all the above situations.

[0143] It should be noted that with the development of device technology, there are various types of switches used in power electronic circuits, such as diodes, MOSFETs, and IGBTs. Due to the development of control technology, fully controlled devices can completely replace traditional diode rectification to achieve efficient synchronous rectification. Therefore, for rectifier circuits, there is no need to distinguish between diodes and fully controlled switching devices.

[0144] Those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A clamping resonant circuit, characterized in that, The circuit includes: a first resonant inductor, a second resonant inductor, a resonant capacitor, and a clamping switching unit; The first resonant inductor and the resonant capacitor are connected in series to form the first branch; The second resonant inductor is connected to the clamping switching unit to form the second branch; The second branch is connected in parallel across the resonant capacitor; The clamping switching unit is used to turn on the second branch when the voltage across the resonant capacitor is greater than or equal to a preset value; The clamping switching unit includes a first controllable switching device and a voltage detection device; The first terminal of the first controllable switching device is connected to the first terminal of the voltage detection device and the first terminal of the resonant capacitor, the second terminal of the first controllable switching device is connected to the second resonant inductor, and the control terminal of the first controllable switching device is connected to the control terminal of the voltage detection device. The second terminal of the voltage detection device is connected to the second terminal of the resonant capacitor; The voltage detection device is used to control the first controllable switching device to turn on when it detects that the voltage across the resonant capacitor is greater than a first threshold, and to control the first controllable switching device to turn off when it detects that the voltage across the resonant capacitor is less than or equal to the first threshold; or The clamping switching unit includes a second controllable switching device and a current detection device; The first terminal of the second controllable switching device is connected to the first terminal of the current sensing device and the first resonant inductor, respectively; the second terminal of the second controllable switching device is connected to the second resonant inductor; and the control terminal of the second controllable switching device is connected to the control terminal of the current sensing device. The second terminal of the current sensing device is connected to the resonant capacitor; The current detection device is used to control the second controllable switching device to turn on when it detects that the current flowing through the resonant capacitor is greater than the second threshold, and to control the second controllable switching device to turn off when it detects that the current flowing through the resonant capacitor is less than or equal to the second threshold.

2. The circuit as described in claim 1, characterized in that, The inductance value of the first resonant inductor is the same as that of the second resonant inductor.

3. A converter, characterized in that, It includes a DC source, a chopper circuit, a rectifier circuit, and a clamping resonant circuit as described in claim 1 or 2, wherein, The DC source, the chopper circuit, the clamping resonant circuit, and the rectifier circuit are connected in sequence; The chopper circuit is either a full-bridge chopper circuit or a half-bridge chopper circuit, wherein... The full-bridge chopper circuit includes a first switch, a second switch, a third switch, and a fourth switch. The first switch and the second switch are connected in series to form a first bridge arm, and the third switch and the fourth switch are connected in series to form a second bridge arm. The first bridge arm and the second bridge arm are connected in parallel. The half-bridge chopper circuit includes a fifth switch and a sixth switch, which are connected in series to form a third bridge arm; The rectifier circuit is either a full-bridge rectifier circuit or a full-wave rectifier circuit, wherein... The full-bridge rectifier circuit includes a first transformer, a seventh switch, an eighth switch, a ninth switch, and a tenth switch. The seventh switch and the eighth switch are connected in series to form a fourth bridge arm, and the ninth switch and the tenth switch are connected in series to form a fifth bridge arm. The fourth bridge arm and the fifth bridge arm are connected in parallel and connected to the first terminal and the second terminal of the first transformer. The full-wave rectifier circuit includes a second transformer, an eleventh switch, and a twelfth switch. The eleventh switch and the twelfth switch are connected in series to form a sixth bridge arm, which is connected in parallel with the secondary side of the second transformer.

4. The converter as described in claim 3, characterized in that, The chopper circuit is a full-bridge chopper circuit, the rectifier circuit is a full-bridge rectifier circuit, and the clamping resonant circuit includes a first clamping resonant circuit, wherein... The positive terminal of the DC source is connected to one end of the full-bridge chopper circuit, and the negative terminal of the DC source is connected to the other end of the full-bridge chopper circuit. The primary side of the first transformer is connected between the first resonant inductor and the resonant capacitor in the first clamped resonant circuit, and the secondary side of the first transformer is connected between the midpoint of the fourth bridge arm and the midpoint of the fifth bridge arm. One end of the series connection of the first resonant inductor, the primary side of the first transformer, and the resonant capacitor in the first clamping resonant circuit is connected to the midpoint of the first bridge arm, and the other end of the series connection is connected to the midpoint of the second bridge arm.

5. The converter as described in claim 4, characterized in that, It also includes a second clamping resonant circuit; The secondary side of the first transformer is connected between the first resonant inductor and the resonant capacitor in the second clamping resonant circuit. One end of the series connection of the resonant capacitor in the second clamping resonant circuit, the secondary side of the first transformer, and the resonant capacitor in the second clamping resonant circuit is connected to the midpoint of the fourth bridge arm, and the other end of the series connection is connected to the midpoint of the fifth bridge arm.

6. The converter as described in claim 3, characterized in that, The chopper circuit is a half-bridge chopper circuit, and the rectifier circuit is a full-bridge rectifier circuit. The resonant capacitor includes a first sub-resonant capacitor and a second sub-resonant capacitor. The clamping switching unit includes a first sub-clamping switching unit and a second sub-clamping switching unit. The first sub-resonant capacitor and the second sub-resonant capacitor are connected in series to form a seventh bridge arm. One end of the first sub-clamping switching unit is connected to one end of the seventh bridge arm, and one end of the second sub-clamping switching unit is connected to the other end of the seventh bridge arm. The second resonant inductor is connected between the other end of the first sub-clamping switching unit, the other end of the second sub-clamping switching unit, and the midpoint of the seventh bridge arm. The third bridge arm and the seventh bridge arm are connected in parallel and then connected to the positive and negative terminals of the DC source. The secondary side of the first transformer is connected between the midpoint of the fourth bridge arm and the midpoint of the fifth bridge arm.

7. The converter as claimed in claim 3, characterized in that, The chopper circuit is a half-bridge chopper circuit, and the rectifier circuit is a full-wave rectifier circuit. The resonant capacitor includes a third sub-resonant capacitor and a fourth sub-resonant capacitor; the second resonant inductor includes a first sub-resonant inductor and a second sub-resonant inductor; the clamping switching unit includes a third sub-clamping switching unit and a fourth sub-clamping switching unit; the third sub-resonant capacitor and the fourth sub-resonant capacitor are connected in series to form an eighth bridge arm; the first sub-resonant inductor is connected in series with the third sub-clamping switching unit and then connected in parallel across the third sub-resonant capacitor; the second sub-resonant inductor is connected in series with the fourth sub-clamping switching unit and then connected in parallel across the fourth sub-resonant capacitor; the first resonant inductor is connected between the midpoint of the third bridge arm and the first end of the primary side of the second transformer. One end of the third bridge arm is connected to the positive terminal of the DC source, and the other end of the third bridge arm is connected to the negative terminal of the DC source.

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