Resonant conversion circuit and resonant converter

Abstract

The invention provides a resonant conversion circuit and a resonant converter. The resonant conversion circuit comprises a first bridge circuit; a high-frequency transformer; the current sampling circuit is used for collecting the current of the resonant conversion circuit; the first end of the driving circuit is connected with the first bridge circuit, and the driving circuit is used for driving the first bridge circuit to work; the comparison protection circuit comprises a first diode, and the negative electrode of the first diode is connected with the current sampling circuit; and when the current of the resonant conversion circuit is greater than or equal to a preset threshold value, the first diode is in a conducting state, so that the comparison protection circuit is in a conducting state, and the driving circuit stops outputting the driving signal. After the resonant conversion circuit generates the overcurrent signal, the output of the driving signal can be quickly stopped, and the purpose of quick protection is achieved.

Description

Technical Field

[0001] The present invention relates to the field of power technologies, and more particularly, to a resonant conversion circuit and a resonant converter. Background Art

[0002] Currently, most sampling schemes in resonant conversion circuits sample current through a current sensor and then output a current signal or a voltage signal. The output signal is processed by an operational amplifier and then sent to a voltage comparator for comparison to obtain an overcurrent protection signal. The overcurrent protection signal is then sent to a DSP (Power Switch Driver, power switch driving module) for driving signal blocking processing. The entire process includes sampling filter delay, operational amplifier output delay, comparator input delay, comparator output signal delay, and DSP software processing delay. After the DSP drive is blocked, buffer delay, PCB (Printed Circuit Board) trace loop delay, and drive isolation chip delay are required. Therefore, the delay time from the generation of the overcurrent signal to the complete turn-off of the power switch tube is very long. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art or related technologies.

[0004] To this end, a first aspect of the present invention provides a resonant conversion circuit.

[0005] A second aspect of the present invention provides a resonant converter.

[0006] In view of this, according to the first aspect of the present invention, a resonant conversion circuit is provided, including: a first bridge circuit, a first end of the first bridge circuit is connected to an input circuit for transmitting the energy of the input circuit; a high-frequency transformer, a primary side of the high-frequency transformer is connected to a second end of the first bridge circuit for energy transfer; a current sampling circuit, a first end of the current sampling circuit is connected to the second end of the first bridge circuit, and a second end of the current sampling circuit is connected to the primary side of the high-frequency transformer for collecting the current of the resonant conversion circuit; a driving circuit, a first end of the driving circuit is connected to the first bridge circuit for driving the first bridge circuit to operate; a comparison protection circuit, a first end of the comparison protection circuit is connected to a third end of the current sampling circuit, and a second end of the comparison protection circuit is connected to a second end of the driving circuit; the comparison protection circuit includes: a first diode, a negative electrode of the first diode is connected to the current sampling circuit; wherein, when the current of the resonant conversion circuit is greater than or equal to a preset threshold, the first diode is in a conducting state, so that the comparison protection circuit is in a conducting state, and the driving circuit stops outputting a driving signal.

[0007] The resonant conversion circuit provided by the present invention mainly includes: a first bridge circuit, a high-frequency transformer, a current sampling circuit, a driving circuit, and a comparison protection circuit. Among them, the first end of the first bridge circuit is connected to the input circuit. The primary side of the high-frequency transformer is connected to the second end of the first bridge circuit, and the high-frequency transformer can perform energy transfer. Further, the resonant conversion circuit further includes: a current sampling circuit, wherein the first end of the current sampling circuit is connected to the second end of the first bridge circuit, and the second end of the current sampling circuit is connected to the primary side of the high-frequency transformer, that is, the current sampling circuit is located between the first bridge circuit and the high-frequency transformer, so as to be able to collect the current of the resonant conversion circuit. The first end of the driving circuit is connected to the first bridge circuit. A comparison protection circuit, the first end of the comparison protection circuit is connected to the third end of the current sampling circuit, and the second end of the comparison protection circuit is connected to the second end of the driving circuit, that is, the comparison protection circuit is located between the current sampling circuit and the driving circuit. The comparison protection circuit includes: a first diode, wherein the negative electrode of the first diode is connected to the current sampling circuit, and the positive electrode of the first diode is connected to the driving circuit. When the current of the resonant conversion circuit collected by the current sampling circuit is greater than or equal to a preset threshold value, it indicates that an overcurrent signal is generated in the resonant conversion circuit at this time. At this time, the first diode is broken down, that is, the first diode is in a conducting state, so that the comparison protection circuit is turned on, and further the driving circuit stops outputting a driving signal. By directly connecting the comparison protection circuit and the driving circuit and setting the first diode in the comparison protection circuit in the present invention, when the current of the resonant conversion circuit is greater than or equal to the preset threshold value, that is, when an overcurrent signal is generated, the breakdown of the first diode is caused, and further the driving circuit is controlled to stop working, so as to achieve the purpose of quickly stopping the output of the driving signal after the overcurrent signal is generated in the resonant conversion circuit, achieving the purpose of rapid protection. At the same time, the risk of introducing interference and signal parasitic oscillation caused by the long-distance wiring of the sampling signal on the PCB (Printed Circuit Board) can also be reduced. At the same time, there is no operational amplifier and comparator in the entire sampling circuit, and it is not affected by bandwidth limitation, filtering delay, and level rising rate.

[0008] In some technical solutions, optionally, the driving circuit includes: a driving chip, and the driving chip includes an enable pin and a first pin; wherein, when the enable pin is at a high level, the first pin outputs a driving signal to drive the first bridge circuit to work, and when the enable pin is at a low level, the first pin stops outputting the driving signal.

[0009] In this technical solution, the driving circuit includes: a driving chip. The driving chip has an enable pin and a first pin. When the enable pin is at a high level, the driving chip is in an operating state, that is, the first pin of the driving chip can emit a driving signal. When the enable pin is at a low level, the driving chip stops operating, that is, the first pin stops emitting the driving signal. In the present invention, by placing the entire circuit near the power transistor driving chip in the PCB (Printed Circuit Board) layout, a very fast response speed can be achieved.

[0010] In some technical solutions, optionally, the comparison protection circuit includes: a switch component. The first end of the switch component is connected to the positive electrode of the first diode; the second end of the switch component is connected to the enable pin; the third end of the switch component is connected to the first pin. When the first diode is in a conducting state, the switch component is in a conducting state, so that when the first pin is at a low level, the enable pin changes from a high level to a low level.

[0011] In this technical solution, the comparison protection circuit further includes: a switch component. The first end of the switch component is connected to the positive electrode of the first diode, the second end of the switch component is connected to the enable pin, and the third end of the switch component is connected to the first pin. When the first diode is in a conducting state, the switch component is also conducted. Furthermore, since the first end of the switch component is connected to the first pin and the second end of the switch component is connected to the enable pin, when the state of the first pin is at a low level, the switch component can pull down the enable pin, that is, the enable pin changes from a high level to a low level, and further the driving chip stops outputting the driving signal. By setting the switch component, the technical effect of being able to pull down the level of the enable pin when the first pin is at a low level and further making the driving chip stop outputting the driving signal is achieved.

[0012] In some technical solutions, optionally, the switch component includes: a first triode, the base of the first triode is connected to the positive electrode of the first diode, and the collector of the first triode is connected to the enable pin; a second triode, the base of the second triode is connected to the first pin, the emitter of the second triode is connected to the emitter of the first triode, and the collector of the second triode is grounded. When the current of the resonant conversion circuit is greater than or equal to a preset threshold and the first pin is at a low level, the first diode is broken down, and the first triode and the second triode are in a conducting state, so that the enable pin changes from a high level to a low level and the driving chip stops outputting the driving signal.

[0013] In this technical solution, the switching component includes: a first triode and a second triode. Among them, the base of the first triode is connected to the positive electrode of the first diode, the collector of the first triode is connected to the enable pin of the driving chip, and the emitter of the first triode is connected to the emitter of the second triode. When the first diode is broken down, the first triode is in the conducting state. Further, the base of the second triode is connected to the first pin, the emitter of the second triode is connected to the emitter of the first triode, and the collector of the second triode is grounded. When the first pin is at a low level, the second triode is in the conducting state. When the current of the resonant conversion circuit is greater than or equal to the preset threshold, it indicates that overcurrent occurs at this time. Therefore, the output signal of the current sampling circuit will break down the first diode, so that the first triode is in the conducting state. If the first pin of the driving chip is in the low-level state at this time, the second triode will also be in the conducting state, so that the switching component is completely conducting, and then the enable pin of the driving chip is pulled low, that is, changed from a high level to a low level, so that the driving chip stops outputting the driving signal. In the present invention, by setting the first triode and the second triode, when overcurrent occurs, the output signal of the current sampling circuit triggers the breakdown of the first diode, triggering the overcurrent signal. At the same time, adding the drive interlock signal can trigger the overcurrent signal to take effect only when the drive signal is at a low level. The overcurrent signal taking effect directly pulls low the enable pin of the driving chip, stops the output of the driving signal, and achieves the purpose of rapid protection. At the same time, it can also ensure that the high-frequency switching device does not turn off when conducting a large current, causing a large voltage stress spike.

[0014] In some technical solutions, optionally, the driving circuit further includes: a controller, which is connected to the driving chip and is used to control the operation of the driving chip.

[0015] In this technical solution, the driving circuit further includes: a controller. Among them, the controller is connected to the driving chip, and the controller can control the operation of the driving chip. When the controller controls the driving chip to output a driving signal, the controller can control the enable pin of the driving chip to be at a high level, so that the first pin of the driving chip outputs the driving signal.

[0016] In some technical solutions, optionally, the resonant conversion circuit further includes: a second bridge circuit, the first end of the second bridge circuit is connected to the secondary side of the high-frequency transformer, and the second end of the second bridge circuit is connected to the output circuit, and is used to transmit the energy transmitted by the high-frequency transformer to the output circuit.

[0017] In this technical solution, the resonant conversion circuit further includes: a second bridge circuit. Wherein, the first end of the second bridge circuit is connected to the secondary side of the high-frequency transformer, the second end of the second bridge circuit is connected to the output circuit, and the second bridge circuit can convert the high-frequency AC voltage transmitted by the high-frequency transformer into a pulsating DC voltage and transmit it to the output circuit. The energy is transmitted from the input circuit to the output circuit through the first bridge circuit, the high-frequency transformer and the second bridge circuit.

[0018] In some technical solutions, optionally, the comparison protection circuit further includes: a first resistor, one end of the first resistor is connected to the positive electrode of the first diode, the other end of the first resistor is connected to the base of the first triode, and is used to protect the first diode; a first capacitor, one end of the first capacitor is connected to the base of the first triode, and the other end is grounded, and is used to protect the first triode; a second resistor, one end of the second resistor is connected to the collector of the second triode, and the other end is grounded, and is used to protect the second triode; a third resistor, one end of the third resistor is connected to the first pin, and the other end is connected to the base of the second triode, and is used to protect the second triode; a second capacitor, one end of the second capacitor is connected to the base of the second triode, and the other end is grounded, and is used to protect the second triode.

[0019] In this technical solution, the comparison protection circuit further includes: a first resistor, a first capacitor, a second resistor, a third resistor and a second capacitor. Wherein, one end of the first resistor is connected to the positive electrode of the first diode, and the other end of the first resistor is connected to the base of the first triode, that is, the positive electrode of the first diode and the base of the first triode are connected through the first resistor. By setting the first resistor between the two, when the first diode is broken down and the energy flows to the first triode, it plays a protective role. One end of the first capacitor is connected to the base of the first triode, and the other end of the first capacitor is grounded, so as to divide the voltage when the first diode is turned on, thereby protecting the first triode. One end of the second resistor is connected to the collector of the second triode, and the other end of the second resistor is grounded. When the second triode is turned on, the second resistor can shunt the current, thereby protecting the second triode. One end of the third resistor is connected to the first pin, and the other end of the third resistor is connected to the base of the second triode, which can shunt the current, and further protect the second triode; one end of the second capacitor is connected to the base of the second triode, and the other end of the second capacitor is grounded, which can divide the voltage, and further protect the second triode.

[0020] In some technical solutions, optionally, the resonant conversion circuit further includes: a current detection circuit, the first end of the current detection circuit is connected to the third end of the current sampling circuit, and the second end of the current detection circuit is connected to the first end of the comparison protection circuit, and is used to convert the high-frequency AC sine wave current signal into a voltage signal.

[0021] In this technical solution, the resonant conversion circuit further includes: a current detection circuit. Among them, the first end of the current detection circuit is connected to the third end of the current sampling circuit, and the second end of the current detection circuit is connected to the first end of the comparison protection circuit. That is, the current sampling circuit and the comparison protection circuit are connected through the current detection circuit. The current detection circuit can convert the high-frequency alternating current sine current signal collected by the current sampling circuit into a voltage signal.

[0022] In some technical solutions, optionally, the current detection circuit includes: a third bridge circuit, which is connected to the current sampling circuit and is used to rectify the high-frequency alternating current sine wave current signal into a flat-topped wave current signal; a sampling resistor, which is connected in parallel with the third bridge circuit and is used to convert the flat-topped wave current signal into a voltage signal.

[0023] In this technical solution, the current detection circuit includes: a third bridge circuit and a sampling resistor. Among them, the third bridge circuit includes a plurality of rectifier diodes. The third bridge circuit is connected to the current sampling circuit, and the third bridge circuit can rectify the high-frequency alternating current sine wave current signal into a flat-topped wave current signal. The sampling resistor is connected in parallel with the third bridge circuit, and the flat-topped wave current signal rectified by the third bridge circuit can convert the current signal into a voltage signal through the sampling resistor.

[0024] In some technical solutions, optionally, the sampling resistor includes: a fourth resistor, which is connected in parallel with the third bridge circuit; a fifth resistor, which is connected in parallel with the fourth resistor.

[0025] In this technical solution, the sampling resistor includes: a fourth resistor and a fifth resistor. Among them, the fourth resistor is connected in parallel with the third bridge circuit, and the fifth resistor is connected in parallel with the fourth resistor. By setting the fourth resistor and the fifth resistor, the current of the resonant conversion circuit can be accurately obtained.

[0026] In some technical solutions, optionally, the current sampling circuit includes: a current transformer, the primary side of which is respectively connected to the first bridge circuit and the high-frequency transformer, and the secondary side is connected to the current detection circuit, and is used to convert the current of the resonant conversion circuit into a weak current signal.

[0027] In this technical solution, the current sampling circuit includes: a current transformer. Among them, the current transformer includes a primary side and a secondary side. The primary side of the current transformer is respectively connected to the first bridge circuit and the high-frequency transformer, that is, the primary side of the current transformer is located between the first bridge circuit and the high-frequency transformer. The secondary side of the current transformer is connected to the current detection circuit. By setting the current transformer, the current can be converted into a weak current signal, and at the same time, it can also play a role in isolating the high-voltage power part from the weak current control signal. At the same time, through the turns ratio between the primary side and the secondary side of the current transformer, the power current is reduced.

[0028] In some technical solutions, optionally, the resonant conversion circuit further includes: a resonant cavity circuit, a first end of the resonant cavity circuit is connected to the first bridge circuit, and a second end of the resonant cavity circuit is connected to the high-frequency transformer, for adjusting the voltage output from the first bridge circuit to the high-frequency transformer.

[0029] In this technical solution, the resonant conversion circuit further includes: a resonant cavity circuit. Wherein, a first end of the resonant cavity circuit is connected to the first bridge circuit, a second end of the resonant cavity circuit is connected to the high-frequency transformer, and the resonant cavity circuit can present different impedances under different switching frequency conditions, so as to achieve the purpose of adjusting the voltage output from the first bridge circuit to the high-frequency transformer.

[0030] In some technical solutions, optionally, the resonant cavity circuit includes: a third capacitor, one end of the third capacitor is connected to the first bridge circuit; a first inductor, one end of the first inductor is connected to the third capacitor, and the other end of the first inductor is connected to the primary side of the high-frequency transformer.

[0031] In this technical solution, the resonant cavity circuit includes: a third capacitor and a first inductor. Wherein, one end of the third capacitor is connected to the first bridge circuit, the other end of the third capacitor is connected to the first inductor, and the other end of the first inductor is connected to the high-frequency transformer. By arranging the series-connected third capacitor and first inductor in the resonant cavity circuit, the resonant cavity circuit can present different impedances under different switching frequency conditions.

[0032] In some technical solutions, optionally, the resonant conversion circuit further includes: a fourth capacitor, the fourth capacitor is connected in parallel with the first bridge circuit and is connected to the input circuit; a fifth capacitor, the fifth capacitor is connected in parallel with the second bridge circuit and is connected to the output circuit.

[0033] In this technical solution, the resonant conversion circuit further includes: a fourth capacitor and a fifth capacitor. Wherein, the fourth capacitor is connected in parallel with the first bridge circuit, that is, both ends of the fourth capacitor are respectively connected to both ends of the first bridge circuit, and the fourth capacitor is connected to the input circuit, and the fourth capacitor can filter the high-frequency ripple current input by the input circuit. The fifth capacitor is connected in parallel with the second bridge circuit, that is, both ends of the fifth capacitor are respectively connected to both ends of the second bridge circuit, and the fifth capacitor is connected to the output circuit, and the fifth capacitor can filter the high-frequency ripple current output by the second bridge circuit and play a role in buffering energy.

[0034] According to the second aspect of the present invention, a resonant converter is provided, wherein the resonant converter includes: the resonant conversion circuit in any of the above technical solutions.

[0035] The resonant converter provided by the present invention mainly includes: the resonant conversion circuit in any of the above technical solutions. Therefore, it has the technical effects of any of the technical solutions in the first aspect above, which will not be elaborated here.

[0036] The additional aspects and advantages of the present invention will become apparent in the following description section or be learned through the practice of the present invention.

[0037] The additional aspects and advantages of the present invention will become apparent in the following description section or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0039] Figure 1 FIG. 1 shows one of the schematic structural diagrams of a resonant conversion circuit in the related art;

[0040] Figure 2 FIG. 2 shows another schematic structural diagram of a resonant conversion circuit in the related art;

[0041] Figure 3 FIG. 3 shows one of the schematic structural diagrams of a resonant conversion circuit according to an embodiment of the present invention;

[0042] Figure 4 FIG. 4 shows another schematic structural diagram of a resonant conversion circuit according to an embodiment of the present invention;

[0043] Figure 5 FIG. 5 shows the schematic structural diagram of a resonant converter according to an embodiment of the present invention;

[0044] Wherein, Figure 1 and Figure 2 the corresponding relationship between the reference numerals and the component names in FIGS. 1 to 5 is as follows:

[0045] 10’ Resonant conversion circuit, C1’ First capacitor, 104’ First bridge circuit, 106’ Resonant cavity circuit, C2’ Second capacitor, L1’ First inductor, 108’ High-frequency transformer, 110’ Second bridge circuit, C3’ Third capacitor, 112’ Input circuit, 114’ Output circuit, 116’ Current sampling circuit, T2’ Current transformer, 118’ Current detection circuit, 120’ Third bridge circuit, R1’ First resistor, R2’ Second resistor, 122’ Operational amplifier, 124’ Comparator, 126’ Driver chip, 128’ Controller, EN’ Enable pin.

[0046] Figures 3 to 5 The corresponding relationship between the reference numerals and the component names in FIGS. 1 to 5 is as follows:

[0047] 10 Resonant conversion circuit, 102 First bridge circuit, 1022 First end of the first bridge circuit, 1024 Second end of the first bridge circuit, 104 Input circuit, 106 High-frequency transformer, 108 Second bridge circuit, 1082 First end of the second bridge circuit, 1084 Second end of the second bridge circuit, 110 Output circuit, 112 Current sampling circuit, 1122 First end of the current sampling circuit, 1124 Second end of the current sampling circuit, 1126 Third end of the current sampling circuit, 114 Driving circuit, 1146 First end of the driving circuit, 1148 Second end of the driving circuit, 116 Comparison and protection circuit, 1162 First end of the comparison and protection circuit, 1164 Second end of the comparison and protection circuit, 1142 Driving chip, 1144 Controller, D9 First diode, 124 Switch component, 1242 First end of the switch component, 1244 Second end of the switch component, 1246 Third end of the switch component, Q5 First triode, Q6 Second triode, EN Enable pin, 118 First pin, R1 First resistor, C1 First capacitor, R2 Second resistor, R3 Third resistor, C2 Second capacitor, 120 Current detection circuit, 1206 First end of the current detection circuit, 1208 Second end of the current detection circuit, 1202 Third bridge circuit, 1204 Sampling resistor, R4 Fourth resistor, R5 Fifth resistor, T2 Current transformer, 122 Resonant cavity circuit, 1222 First end of the resonant cavity circuit, 1224 Second end of the resonant cavity circuit, C3 Third capacitor, L1 First inductor, C4 Fourth capacitor, C5 Fifth capacitor, 20 Resonant converter, Q1 First power switch device, Q2 Second power switch device, Q3 Third power switch device, Q4 Fourth power switch device, D1 Second diode, D2 Third diode, D3 Fourth diode, D4 Fifth diode, D5 Sixth diode, D6 Seventh diode, D7 Eighth diode, D9 Ninth diode. Detailed implementation

[0048] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0049] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the limitations of the specific embodiments disclosed below.

[0050] As Figure 1 and Figure 2 shown, Figure 1 and Figure 2 For the resonant conversion circuit 10' in the related art, inFigure 1 and Figure 2 In Figure 2 , the resonance conversion circuit 10' from left to right is successively an input circuit 112', a first capacitor C1', a first bridge circuit 104', a resonance cavity circuit 106', a high-frequency transformer 108', a second bridge circuit 110', a third capacitor C3' and an output circuit 114'. Among them, the resonance cavity circuit 106' includes a second capacitor C2' and a first inductor L1' connected in series. At the same time, a current sampling circuit 116' is arranged between the first bridge circuit 104' and the high-frequency transformer 108' and can collect the current of the resonance conversion circuit. The current sampling circuit 116' can specifically be a current transformer T2'. Further, a current detection circuit 118' is connected to the current sampling circuit 116' and is used for converting the current signal collected by the current sampling circuit 116'. The current detection circuit 118' includes a third bridge circuit 120', a first resistor R1' and a second resistor R2'. An operational amplifier 122' is connected to the current detection circuit 118' and can amplify the signal output by the current detection circuit 118'. A comparator 124' is connected to the operational amplifier 122' and can compare the signal output from the output port Vout of the operational amplifier 122' with a reference level and output a result through the output port Vout of the comparator 124'. The enable pin EN' of the drive chip 126' is connected to the comparator 124'. When an overcurrent occurs in the resonance conversion circuit 10', the overcurrent signal needs to be first amplified by the operational amplifier 122', then input into the comparator 124' to be compared with the reference level, and finally as Figure 1 shown, output a low level according to the comparison result, thereby controlling the drive chip 126' to stop outputting a drive signal, or as Figure 2 shown, send the comparison result to the controller 128', and then the controller 128' controls the drive chip 126' to stop outputting a drive signal.

[0051] Through Figure 1 and Figure 2It can be seen that in the related art, current is sampled by a current sensor and then a current signal or a voltage signal is output. The output signal is processed by an operational amplifier and then sent to a voltage comparator for comparison to obtain an overcurrent protection signal. The overcurrent protection signal is then sent to a DSP (Power Switch Driver, power switch driving module) for driving signal blocking processing. The whole process includes sampling filtering delay, operational amplifier output delay, comparator input delay, and comparator output signal delay. Therefore, from the generation of the overcurrent signal to the complete turn-off of the power switch tube, the delay time is very long. It is measured that the whole delay can reach more than 1 μs. The whole delay time can cause the current in the loop to rise very high, posing a great risk to the reliability and thermal stress of the power device. There are relatively large risks in some relatively extreme working conditions, such as output short circuit, sudden application of full load, input power failure and other scenarios. In order to prevent the overcurrent signal from being mis-triggered under certain working conditions, such as sudden loading and unloading, and during the startup process. Filter capacitors are added at the signal input end and output end of the operational amplifier comparator, and at the input end and output end of the comparator. On the one hand, these filter capacitors can filter out error-triggered interference signals, and at the same time, they will also filter out some real overcurrent signals, making the overcurrent signal smoothed and unable to trigger the overcurrent in time. It even takes two to three switching cycles to actually trigger the overcurrent protection. At this time, the actual current has reached a very high level, even reaching the risk of tube damage, and in severe cases, it may lead to the phenomenon of machine damage.

[0052] As Figure 3 and Figure 4 shown, the present invention provides a resonant conversion circuit 10, including: a first bridge circuit 102, a first end 1022 of the first bridge circuit is connected to an input circuit 104 for transmitting the energy of the input circuit 104; a high-frequency transformer 106, a primary side of the high-frequency transformer 106 is connected to a second end 1024 of the first bridge circuit for energy transfer; a current sampling circuit 112, a first end 1122 of the current sampling circuit is connected to the second end 1024 of the first bridge circuit, and a second end 1124 of the current sampling circuit is connected to the primary side of the high-frequency transformer 106 for collecting the current of the resonant conversion circuit 10; a driving circuit 114, a first end 1146 of the driving circuit is connected to the first bridge circuit 102 for driving the first bridge circuit 102 to operate; a comparison protection circuit 116, a first end 1162 of the comparison protection circuit is connected to a third end 1126 of the current sampling circuit, and a second end 1164 of the comparison protection circuit is connected to a second end 1148 of the driving circuit; the comparison protection circuit 116 includes: a first diode D9, a negative electrode of the first diode D9 is connected to the current sampling circuit 112; wherein, when the current of the resonant conversion circuit 10 is greater than or equal to a preset threshold, the first diode D9 is in a conducting state, so that the comparison protection circuit 116 is in a conducting state, and the driving circuit 114 stops outputting a driving signal.

[0053] The resonant conversion circuit 10 provided by the present invention mainly includes: a first bridge circuit 102, a high-frequency transformer 106, a current sampling circuit 112, a driving circuit 114, and a comparison protection circuit 116. Among them, the first end 1022 of the first bridge circuit is connected to the input circuit 104, and the first bridge circuit 102 includes a plurality of power switching devices (such as Figure 4The first power switch device Q1, the second power switch device Q2, the third power switch device Q3, and the fourth power switch device Q4 shown), the power switch device can be a high-frequency switching power device such as an IGBT (Insulated Gate Bipolar Transistor) tube, a MOS (Metal-Oxide-Semiconductor Field Effect Transistor) tube, and a diode. The first bridge circuit 102 can convert the voltage input by the input circuit 104 into a pulsed voltage for transmission by the high-frequency transformer 106. Among them, the input circuit 104 can be a DC source, a battery, a voltage bus, etc. The primary side of the high-frequency transformer 106 is connected to the second end 1024 of the first bridge circuit. The high-frequency transformer 106 can perform energy transmission and also has the function of electrical isolation to meet the safety regulations requirements. Further, the resonant conversion circuit 10 further includes: a current sampling circuit 112. Among them, the first end 1122 of the current sampling circuit is connected to the second end 1024 of the first bridge circuit, and the second end 1124 of the current sampling circuit is connected to the primary side of the high-frequency transformer 106. That is, the current sampling circuit 112 is located between the first bridge circuit 102 and the high-frequency transformer 106, so as to be able to collect the current of the resonant conversion circuit 10. The first end 1146 of the drive circuit is connected to the first bridge circuit 102. Specifically, the drive circuit 114 is respectively connected to a plurality of power switch devices in the first bridge circuit 102. The drive circuit 114 can send drive signals to control the plurality of power switch devices in the first bridge circuit 102 to work, and further control the output of the first bridge circuit 102 to the high-frequency transformer 106. A comparison protection circuit 116, the first end 1162 of the comparison protection circuit is connected to the third end 1126 of the current sampling circuit, and the second end 1164 of the comparison protection circuit is connected to the second end 1148 of the drive circuit. That is, the comparison protection circuit 116 is located between the current sampling circuit and the drive circuit 114. The comparison protection circuit 116 includes: a first diode D9. Among them, the negative electrode of the first diode D9 is connected to the current sampling circuit 112, and the positive electrode of the first diode D9 is connected to the drive circuit 114. When the current of the resonant conversion circuit 10 collected by the current sampling circuit is greater than or equal to a preset threshold, it indicates that an overcurrent signal is generated in the resonant conversion circuit 10 at this time. At this time, the first diode D9 is broken down, that is, the first diode D9 is in a conducting state, so that the comparison protection circuit 116 is conducted, and further the drive circuit 114 stops outputting drive signals.In the present invention, a comparison protection circuit 116 is directly connected to a drive circuit 114, and a first diode D9 is provided in the comparison protection circuit 116. When the current of the resonant conversion circuit 10 is greater than or equal to a preset threshold, that is, when an overcurrent signal is generated, the first diode D9 breaks down, thereby controlling the drive circuit 114 to stop working. Thus, after the resonant conversion circuit 10 generates an overcurrent signal, the drive signal can be quickly stopped from being output, achieving the purpose of rapid protection. At the same time, it is also possible to reduce the risk of interference and signal parasitic oscillation introduced by the long-distance routing of the sampling signal on the PCB (Printed Circuit Board). At the same time, the entire sampling circuit does not have operational amplifiers and comparators, and is not affected by bandwidth limitations, filtering delay, and the rate of rise of the level.

[0054] In some embodiments, optionally, as Figure 4 shown, the drive circuit 114 includes: a drive chip 1142, and the drive chip 1142 includes an enable pin EN and a first pin 118; wherein, when the enable pin EN is at a high level, the first pin 118 outputs a drive signal to drive the first bridge circuit 102 to operate, and when the enable pin EN is at a low level, the first pin 118 stops outputting the drive signal.

[0055] In this embodiment, the drive circuit 114 includes: a drive chip 1142. The drive chip 1142 has an enable pin EN and a first pin 118. The first pin 118 is connected to a plurality of power switch devices in the first bridge circuit 102 (not shown in the figure), and can send a drive signal to the plurality of power switch devices in the first bridge circuit 102. The drive signal can be a PWM (Pulse Width Modulation) signal. When the enable pin EN is in a high-level state, the drive chip 1142 is in an operating state, that is, the first pin 118 of the drive chip 1142 can emit a drive signal. When the enable pin EN is in a low-level state, the drive chip 1142 stops operating, that is, the first pin 118 stops emitting the drive signal. In the present invention, by arranging the entire circuit near the power transistor drive chip 1142 in the PCB (Printed Circuit Board) layout, a very fast response speed can be achieved.

[0056] In some embodiments, optionally, as Figure 4As shown, the comparison protection circuit 116 includes: a switch component 124, the first end 1242 of the switch component is connected to the positive electrode of the first diode D9; the second end 1244 of the switch component is connected to the enable pin EN, and the third end 1246 of the switch component is connected to the first pin 118; wherein, when the first diode D9 is in the conducting state, the switch component 124 is in the conducting state, so that when the first pin 118 is at a low level, the enable pin EN changes from a high level to a low level.

[0057] In this embodiment, the comparison protection circuit 116 further includes: a switch component 124. Among them, the first end 1242 of the switch component is connected to the positive electrode of the first diode D9, the second end 1244 of the switch component is connected to the enable pin EN, and the third end 1246 of the switch component is connected to the first pin 118. When the first diode D9 is in the conducting state, the switch component 124 is also conducted. Furthermore, since the first end 1242 of the switch component is connected to the first pin 118 and the second end 1244 of the switch component is connected to the enable pin EN, when the state of the first pin 118 is at a low level, the switch component 124 can pull down the enable pin EN, that is, the enable pin EN changes from a high level to a low level, and then the driving chip 1142 stops outputting the driving signal. By setting the switch component 124, when the first pin 118 is at a low level, the level of the enable pin EN can be pulled down, and then the technical effect of making the driving chip 1142 stop outputting the driving signal is achieved.

[0058] In some embodiments, optionally, as Figure 4 shown, the switch component 124 includes: a first triode Q5, the base of the first triode Q5 is connected to the positive electrode of the first diode D9, and the collector of the first triode Q5 is connected to the enable pin EN; a second triode Q6, the base of the second triode Q6 is connected to the first pin 118, the emitter of the second triode Q6 is connected to the emitter of the first triode Q5, and the collector of the second triode Q6 is grounded; wherein, when the current of the resonant conversion circuit 10 is greater than or equal to a preset threshold and the first pin 118 is at a low level, the first diode D9 is broken down, and the first triode Q5 and the second triode Q6 are in the conducting state, so that the enable pin EN changes from a high level to a low level, so that the driving chip 1142 stops outputting the driving signal.

[0059] In this embodiment, the switch component 124 includes: a first triode Q5 and a second triode Q6. Among them, the first triode Q5 can be an NPN-type triode, and the second triode Q6 can be a PNP-type triode. The base of the first triode Q5 is connected to the positive electrode of the first diode D9, the collector of the first triode Q5 is connected to the enable pin EN of the drive chip 1142, and the emitter of the first triode Q5 is connected to the emitter of the second triode Q6. Since the base of the first triode Q5 is connected to the positive electrode of the first diode D9, when the first diode D9 is broken down, the first triode Q5 is in the conduction state. Further, the base of the second triode Q6 is connected to the first pin 118, the emitter of the second triode Q6 is connected to the emitter of the first triode Q5, and the collector of the second triode Q6 is grounded. Since the base of the second triode Q6 is connected to the first pin 118, when the first pin 118 is at a high level, the second triode Q6 is in the cut-off state, and when the first pin 118 is at a low level, the second triode Q6 is in the conduction state. When the current of the resonant conversion circuit 10 is greater than or equal to the preset threshold, it indicates that an overcurrent has occurred at this time. Therefore, the output signal of the current sampling circuit 112 will break down the first diode D9, so that the first triode Q5 is in the conduction state. If the first pin 118 of the drive chip 1142 is in the low-level state at this time, the second triode Q6 will also be in the conduction state, so that the switch component 124 is completely turned on. Since the collector of the first triode Q5 is connected to the enable pin EN, the emitter of the second triode Q6 is connected to the emitter of the first triode Q5, and the collector of the second triode Q6 is grounded, when both the first triode Q5 and the second triode Q6 are in the conduction state, the enable pin EN of the drive chip 1142 will be pulled low, that is, changed from a high level to a low level, so that the drive chip 1142 stops outputting the drive signal. In the present invention, by setting the first triode Q5 and the second triode Q6, when an overcurrent occurs, the output signal of the current sampling circuit 112 triggers the breakdown of the first diode D9, triggering the overcurrent signal. At the same time, adding a drive interlock signal can trigger the overcurrent signal to take effect only when the drive signal is at a low level. When the overcurrent signal takes effect, it directly pulls down the enable pin EN of the drive chip 1142, stops the output of the drive signal, and achieves the purpose of rapid protection. At the same time, it can also ensure that the high-frequency switching device does not turn off when conducting a large current, causing a large voltage stress spike.

[0060] In some embodiments, optionally, as Figure 4 shown, the drive circuit 114 further includes: a controller 1144, and the controller 1144 is connected to the drive chip 1142 for controlling the operation of the drive chip 1142.

[0061] In this embodiment, the drive circuit 114 further includes: a controller 1144. Among them, the controller 1144 is connected to the drive chip 1142, and the controller 1144 can control the operation of the drive chip 1142. When the controller 1144 controls the drive chip 1142 to output a drive signal, the controller 1144 can control the enable pin EN of the drive chip 1142 to be at a high level, so that the first pin 118 of the drive chip 1142 outputs a drive signal.

[0062] In some embodiments, optionally, as Figure 3 and Figure 4 shown, the resonant conversion circuit 10 further includes: a second bridge circuit 108. The first end 1082 of the second bridge circuit is connected to the secondary side of the high-frequency transformer 106, and the second end 1084 of the second bridge circuit is connected to the output circuit 110, and is used to deliver the energy transmitted by the high-frequency transformer 106 to the output circuit 110.

[0063] In this embodiment, the resonant conversion circuit 10 further includes: a second bridge circuit 108. Among them, the second bridge circuit 108 includes a plurality of diodes (such as Figure 4 the second diode D1, the third diode D2, the fourth diode D3, and the fifth diode D4 in), the first end 1082 of the second bridge circuit is connected to the secondary side of the high-frequency transformer 106, the second end 1084 of the second bridge circuit is connected to the output circuit 110, and the second bridge circuit 108 can convert the high-frequency alternating voltage transmitted by the high-frequency transformer 106 into a pulsating DC voltage and transmit it to the output circuit 110. Among them, the output circuit 110 can be a DC source, a battery, a voltage bus, a load, etc. Through the first bridge circuit 102, the high-frequency transformer 106, and the second bridge circuit 108, the energy is transferred from the input circuit 104 to the output circuit 110.

[0064] In some embodiments, optionally, as Figure 4 shown, the comparison protection circuit 116 further includes: a first resistor R1. One end of the first resistor R1 is connected to the positive electrode of the first diode D9, and the other end of the first resistor R1 is connected to the base of the first triode Q5, and is used to protect the first diode D9; a first capacitor C1. One end of the first capacitor C1 is connected to the base of the first triode Q5, and the other end is grounded, and is used to protect the first triode Q5; a second resistor R2. One end of the second resistor R_{2} is connected to the collector of the second triode Q6, and the other end is grounded, and is used to protect the second triode Q6; a third resistor R3. One end of the third resistor R3 is connected to the first pin 118, and the other end is connected to the base of the second triode Q6, and is used to protect the second triode Q6; a second capacitor C2. One end of the second capacitor C2 is connected to the base of the second triode Q6, and the other end is grounded, and is used to protect the second triode Q6.

[0065] In this embodiment, the comparison protection circuit 116 further includes: a first resistor R1, a first capacitor C1, a second resistor R2, a third resistor R3, and a second capacitor C2. Among them, one end of the first resistor R1 is connected to the positive electrode of the first diode D9, and the other end of the first resistor R1 is connected to the base of the first triode Q5, that is, the positive electrode of the first diode D9 and the base of the first triode Q5 are connected through the first resistor R1. By setting the first resistor R1 between the two, when the first diode D9 is broken down and the energy flows to the first triode Q5, it plays a protective role. One end of the first capacitor C1 is connected to the base of the first triode Q5, and the other end of the first capacitor C1 is grounded, so as to divide the voltage when the first diode D9 is turned on, thereby protecting the first triode Q5. One end of the second resistor R2 is connected to the collector of the second triode Q6, and the other end of the second resistor R2 is grounded. When the second triode Q6 is turned on, the second resistor R2 can shunt the current, thereby protecting the second triode Q6. One end of the third resistor R3 is connected to the first pin 118, and the other end of the third resistor R3 is connected to the base of the second triode Q6, which can shunt the current, and further protect the second triode Q6; one end of the second capacitor C2 is connected to the base of the second triode Q6, and the other end of the second capacitor C2 is grounded, which can divide the voltage, and further protect the second triode Q6. Further, the third resistor R3 and the second capacitor C2 can also form a delay circuit, so as to achieve the purpose of delaying protection.

[0066] In some embodiments, optionally, as Figure 3 shown, the resonant conversion circuit 10 further includes: a current detection circuit 120. The first end 1206 of the current detection circuit is connected to the third end 1126 of the current sampling circuit, and the second end 1208 of the current detection circuit is connected to the first end 1162 of the comparison protection circuit, and is used for converting a high-frequency alternating current sine wave current signal into a voltage signal.

[0067] In this embodiment, the resonant conversion circuit 10 further includes: a current detection circuit 120. Among them, the first end 1206 of the current detection circuit is connected to the third end 1126 of the current sampling circuit, and the second end 1208 of the current detection circuit is connected to the first end 1162 of the comparison protection circuit, that is, the current sampling circuit 112 and the comparison protection circuit 116 are connected through the current detection circuit 120, and the current detection circuit 120 can convert the high-frequency alternating current sine current signal collected by the current sampling circuit into a voltage signal.

[0068] In some embodiments, optionally, as Figure 4As shown, the current detection circuit 120 includes: a third bridge circuit 1202, which is connected to the current sampling circuit 112 and is used to rectify the high-frequency alternating current sine wave current signal into a flat-topped wave current signal; a sampling resistor 1204, which is connected in parallel with the third bridge circuit 1202 and is used to convert the flat-topped wave current signal into a voltage signal.

[0069] In this embodiment, the current detection circuit 120 includes: a third bridge circuit 1202 and a sampling resistor 1204. Among them, the third bridge circuit 1202 includes a plurality of rectifying diodes, such as Figure 4 the sixth diode D5, the seventh diode D6, the eighth diode D7, and the ninth diode D8 in. The third bridge circuit 1202 is connected to the current sampling circuit 112, and the third bridge circuit 1202 can rectify the high-frequency alternating current sine wave current signal into a flat-topped wave current signal. The sampling resistor 1204 is connected in parallel with the third bridge circuit 1202, and the flat-topped wave current signal rectified by the third bridge circuit 1202 can convert the current signal into a voltage signal through the sampling resistor 1204.

[0070] In some embodiments, optionally, as Figure 4 shown, the sampling resistor 1204 includes: a fourth resistor R4, which is connected in parallel with the third bridge circuit 1202; a fifth resistor R5, which is connected in parallel with the fourth resistor R4.

[0071] In this embodiment, the sampling resistor 1204 includes: a fourth resistor R4 and a fifth resistor R5. Among them, the fourth resistor is connected in parallel with the third bridge circuit 1202, and the fifth resistor R5 is connected in parallel with the fourth resistor R4. By setting the fourth resistor R4 and the fifth resistor R5, the current of the resonant conversion circuit 10 can be accurately obtained.

[0072] In some embodiments, optionally, as Figure 4 shown, the current sampling circuit 112 includes: a current transformer T2, the primary side of the current transformer T2 is respectively connected to the first bridge circuit 102 and the high-frequency transformer 106, and the secondary side is connected to the current detection circuit 120, and is used to convert the current of the resonant conversion circuit 10 into a weak electrical signal.

[0073] In this embodiment, the current sampling circuit 112 includes: a current transformer T2. Among them, the current transformer T2 includes a primary side and a secondary side. The primary side of the current transformer T2 is respectively connected to the first bridge circuit 102 and the high-frequency transformer 106, that is, the primary side of the current transformer T2 is located between the first bridge circuit 102 and the high-frequency transformer 106. The secondary side of the current transformer T2 is connected to the current detection circuit 120. By setting the current transformer T2, the current can be converted into a weak electrical signal, and at the same time, it can also play a role in isolating the high-voltage power part from the weak electrical control signal. At the same time, through the turns ratio between the primary side and the secondary side of the current transformer T2, the power current is reduced.

[0074] In some embodiments, optionally, as Figure 3 shown, the resonant conversion circuit 10 further includes: a resonant cavity circuit 122. The first end 1222 of the resonant cavity circuit is connected to the first bridge circuit 102, and the second end 1224 of the resonant cavity circuit is connected to the high-frequency transformer 106, and is used to adjust the voltage output from the first bridge circuit 102 to the high-frequency transformer 106.

[0075] In this embodiment, the resonant conversion circuit 10 further includes: a resonant cavity circuit 122. Among them, the first end 1222 of the resonant cavity circuit is connected to the first bridge circuit 102, and the second end 1224 of the resonant cavity circuit is connected to the high-frequency transformer 106. The resonant cavity circuit 122 can present different impedances under different switching frequency conditions, so as to achieve the purpose of adjusting the voltage output from the first bridge circuit 102 to the high-frequency transformer 106.

[0076] In some embodiments, optionally, as Figure 4 shown, the resonant cavity circuit 122 includes: a third capacitor C3, one end of the third capacitor C3 is connected to the first bridge circuit 102; a first inductor L1, one end of the first inductor L1 is connected to the third capacitor C3, and the other end of the first inductor L1 is connected to the primary side of the high-frequency transformer 106.

[0077] In this embodiment, the resonant cavity circuit 122 includes: a third capacitor C3 and a first inductor L1. Among them, one end of the third capacitor C3 is connected to the first bridge circuit 102, the other end of the third capacitor C3 is connected to the first inductor L1, and the other end of the first inductor L1 is connected to the high-frequency transformer 106. By arranging the series-connected third capacitor C3 and first inductor L1 in the resonant cavity circuit 122, the resonant cavity circuit 122 can present different impedances under different switching frequency conditions.

[0078] In some embodiments, optionally, as Figure 4As shown, the resonant conversion circuit 10 further includes: a fourth capacitor C4, which is connected in parallel with the first bridge circuit 102 and is connected to the input circuit 104; a fifth capacitor C5, which is connected in parallel with the second bridge circuit 108 and is connected to the output circuit 110.

[0079] In this embodiment, the resonant conversion circuit 10 further includes: a fourth capacitor C4 and a fifth capacitor C5. Among them, the fourth capacitor C4 is connected in parallel with the first bridge circuit 102, that is, both ends of the fourth capacitor C4 are respectively connected to both ends of the first bridge circuit 102, and the fourth capacitor C4 is connected to the input circuit 104. The fourth capacitor C4 can filter out the high-frequency ripple current input by the input circuit 104. The fifth capacitor C5 is connected in parallel with the second bridge circuit 108, that is, both ends of the fifth capacitor C5 are respectively connected to both ends of the second bridge circuit 108, and the fifth capacitor C5 is connected to the output circuit 110. The fifth capacitor C5 can filter out the high-frequency ripple current output by the second bridge circuit 108 and play a role in buffering energy.

[0080] Exemplarily, taking the overcurrent protection point of the resonant conversion circuit 10 as 50A as an example, the turn ratio of the current transformer T2 is 1:500. When the current of the first bridge circuit 102 reaches 50A, the primary side of the current transformer T2 is 50A, and the secondary side is 0.1A. The resistance value after the fourth resistor R4 and the fifth resistor R5 are connected in parallel is 25Ω. At this time, the voltage across the sampling resistor 1204 is 2.5V, the first diode D9 conducts, and at the same time the first triode Q5 conducts. When the first pin 118 of the drive chip 1142 outputs a high level, the second triode Q6 is cut off, the enable pin EN of the drive chip 1142 is at a high level, and the drive chip 1142 normally outputs a drive signal. When the first pin 118 of the drive chip 1142 outputs a low level, the second triode Q6 conducts, the enable pin EN of the drive chip 1142 is at a low level, and the drive chip 1142 stops outputting the drive signal. At this time, the overcurrent signal plays a role in blocking the wave output by the drive chip 1142, so as to achieve the effect of overcurrent protection. The entire working loop is very short, the response rate is very fast, and the action is timely. The resonant conversion circuit 10 provided by the present invention can accelerate the LLC overcurrent protection rate, and the overcurrent protection is more timely; at the same time, it effectively avoids the risk of stress spikes caused by the large current of the LLC resonant cavity turning off the switching tube; at the same time, it avoids repeated overcurrent triggering protection, resulting in resonant current oscillation; and the entire sampling circuit does not have an operational amplifier and a comparator, is not affected by bandwidth limitation, filtering delay, and level rising rate; at the same time, through the method of connecting the sampling signal to drive the zener diode, the circuit is simpler and more efficient, without filtering delay, the sampling circuit is close to the power part, and the wiring is short, which can avoid a lot of interference.

[0081] As Figure 5As shown, the present invention provides a resonant converter 20, wherein the resonant converter 20 includes: a resonant conversion circuit 10 as in any of the above embodiments.

[0082] The resonant converter 20 provided by the present invention includes: a resonant conversion circuit 10 as in any of the above embodiments. Therefore, it has the technical effects of any of the above embodiments in the first aspect, which will not be elaborated here.

[0083] In the description of this specification, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance unless otherwise clearly specified and defined; the terms "connection", "installation", "fixation", etc. should all be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0084] In the description of this specification, the description of terms such as "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0085] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A resonant conversion circuit, characterized in that, Including: A first bridge circuit, the first end of the first bridge circuit is connected to the input circuit for transmitting the energy of the input circuit; A high-frequency transformer, the primary side of the high-frequency transformer is connected to the second end of the first bridge circuit for energy transfer; A current sampling circuit, the first end of the current sampling circuit is connected to the second end of the first bridge circuit, and the second end of the current sampling circuit is connected to the primary side of the high-frequency transformer for collecting the current of the resonant conversion circuit; A driving circuit, the first end of the driving circuit is connected to the first bridge circuit for driving the first bridge circuit to operate; A comparison protection circuit, the first end of the comparison protection circuit is connected to the third end of the current sampling circuit, and the second end of the comparison protection circuit is connected to the second end of the driving circuit; The comparison protection circuit includes: a first diode, the negative electrode of the first diode is connected to the current sampling circuit; Wherein, when the current of the resonant conversion circuit is greater than or equal to a preset threshold, the first diode is in a conducting state, so that the comparison protection circuit is in a conducting state, and the driving circuit stops outputting a driving signal.

2. The resonant conversion circuit according to claim 1, wherein The driving circuit includes: A driving chip, the driving chip includes an enable pin and a first pin; Wherein, when the enable pin is at a high level, the first pin outputs a driving signal to drive the first bridge circuit to operate, and when the enable pin is at a low level, the first pin stops outputting a driving signal.

3. The resonant conversion circuit according to claim 2, wherein The comparison protection circuit includes: A switch component, the first end of the switch component is connected to the positive electrode of the first diode; the second end of the switch component is connected to the enable pin, and the third end of the switch component is connected to the first pin; Wherein, when the first diode is in a conducting state, the switch component is in a conducting state, so that when the first pin is at a low level, the enable pin changes from a high level to a low level.

4. The resonant conversion circuit according to claim 3, wherein, The switch component includes: A first triode, the base of the first triode is connected to the positive electrode of the first diode, and the collector of the first triode is connected to the enable pin; A second triode, the base of the second triode is connected to the first pin, the emitter of the second triode is connected to the emitter of the first triode, and the collector of the second triode is grounded; Wherein, when the current of the resonant conversion circuit is greater than or equal to a preset threshold and the first pin is at a low level, the first diode is broken down, and the first triode and the second triode are in a conducting state, so that the enable pin changes from a high level to a low level, so that the driving chip stops outputting a driving signal.

5. The resonant conversion circuit according to claim 2, wherein The driving circuit further includes: A controller, the controller is connected to the driving chip for controlling the operation of the driving chip.

6. The resonant conversion circuit according to claim 1, wherein The resonant conversion circuit further includes: The second bridge circuit, the first end of the second bridge circuit is connected to the secondary side of the high-frequency transformer, and the second end of the second bridge circuit is connected to the output circuit, for delivering the energy transmitted by the high-frequency transformer to the output circuit.

7. The resonant conversion circuit according to claim 4, wherein The comparison protection circuit further includes: A first resistor, one end of the first resistor is connected to the positive electrode of the first diode, and the other end of the first resistor is connected to the base of the first triode, for protecting the first diode; A first capacitor, one end of the first capacitor is connected to the base of the first triode, and the other end is grounded, for protecting the first triode; A second resistor, one end of the second resistor is connected to the collector of the second triode, and the other end is grounded, for protecting the second triode; A third resistor, one end of the third resistor is connected to the first pin, and the other end is connected to the base of the second triode, for protecting the second triode; A second capacitor, one end of the second capacitor is connected to the base of the second triode, and the other end is grounded, for protecting the second triode.

8. The resonant conversion circuit according to any one of claims 1 to 7, characterized in that The resonant conversion circuit further includes: A current detection circuit, the first end of the current detection circuit is connected to the third end of the current sampling circuit, and the second end of the current detection circuit is connected to the first end of the comparison protection circuit, for converting a high-frequency alternating current sine wave current signal into a voltage signal.

9. The resonant conversion circuit according to claim 8, characterized in that The current detection circuit includes: A third bridge circuit, the third bridge circuit is connected to the current sampling circuit, for rectifying the high-frequency alternating current sine wave current signal into a flat-topped wave current signal; A sampling resistor, the sampling resistor is connected in parallel with the third bridge circuit, for converting the flat-topped wave current signal into a voltage signal.

10. The resonant conversion circuit according to claim 9, wherein, The sampling resistor includes: A fourth resistor, the fourth resistor is connected in parallel with the third bridge circuit; A fifth resistor, the fifth resistor is connected in parallel with the fourth resistor.

11. The resonant conversion circuit according to claim 8, characterized in that, The current sampling circuit includes: A current transformer, the primary side of the current transformer is respectively connected to the first bridge circuit and the high-frequency transformer, and the secondary side is connected to the current detection circuit, for converting the current of the resonant conversion circuit into a weak electrical signal.

12. The resonant conversion circuit according to any one of claims 1 to 7, characterized in that, The resonant conversion circuit further includes: A resonant cavity circuit, the first end of the resonant cavity circuit is connected to the first bridge circuit, and the second end of the resonant cavity circuit is connected to the high-frequency transformer, for adjusting the voltage output from the first bridge circuit to the high-frequency transformer.

13. The resonant conversion circuit according to claim 12, characterized in that, The resonant cavity circuit includes: A third capacitor, one end of the third capacitor is connected to the first bridge circuit; A first inductor, one end of the first inductor is connected to the third capacitor, and the other end of the first inductor is connected to the primary side of the high-frequency transformer.

14. The resonant conversion circuit according to claim 6, characterized in that, The resonant conversion circuit further includes: A fourth capacitor, the fourth capacitor is connected in parallel with the first bridge circuit, and the fourth capacitor is connected to the input circuit; A fifth capacitor, the fifth capacitor is connected in parallel with the second bridge circuit, and the fifth capacitor is connected to the output circuit.

15. A resonant converter, characterized in that, Includes: The resonant conversion circuit according to any one of claims 1 to 14.

Images