Protection circuit of full-bridge resonance circuit and converter

Abstract

The utility model provides a full-bridge resonance circuit protection circuit and converter, the protection circuit comprises a full-bridge resonance circuit, a bus, a sampling module, a switch module and a master control module, the full-bridge resonance circuit is connected with a power supply through the bus, the sampling module is connected with the bus and is used for collecting the current value of the bus, and the switch module is connected with the master control module. A first connecting end of the switch module is connected with a power supply, a second connecting end is connected with the full-bridge resonance circuit, and the main control module is connected with the sampling module and the switch module and is used for acquiring a current value of a bus collected by the sampling module; and according to the current value of the bus, the switch module is controlled to disconnect the full-bridge resonant circuit from the power supply. The main control module controls the switch module to disconnect the full-bridge resonant circuit from the power supply according to the current value of the bus collected by the sampling module, so that the problem that power devices on the full-bridge resonant circuit are damaged when overcurrent occurs in the bus is avoided, and the stability and reliability of the full-bridge resonant circuit are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to electronic circuit technical field especially is related to a protection circuit and inverter of full bridge resonant circuit. BACKGROUND

[0002] With the development of power electronics technology, the working frequency of power switching device increases from several kilohertz to several hundred kilohertz, which reduces the energy to be transmitted by inductive device (such as inductor) in a single cycle, thereby significantly reducing the volume of inductor. However, with the increase of switching frequency, the switching loss of the whole system and the peak impulse voltage and current generated by the switching device in the switching process also increase, which has an adverse effect on the working efficiency of the whole machine and electromagnetic interference (EMI).

[0003] To cope with the problem of excessive switching loss and electromagnetic interference, LLC (Inductor-Capacitor-Transformer, Inductor-Capacitor-Transformer resonant converter) and CLLC (Capacitor-Inductor-Inductor-Capacitor, Capacitor-Inductor-Inductor-Capacitor resonant converter) circuits are usually used to realize soft switching technology. The core of soft switching technology is to ensure that there is no overlapping area between source-drain current and voltage waveform when the switching tube is turned on, thereby realizing zero-voltage or zero-current turn-on of the switching device. This method not only significantly reduces the switching loss of the device, but also effectively optimizes the electromagnetic interference performance of the system.

[0004] Currently, full-bridge LLC topology is widely used in inverter products above 1 kilowatt. Full-bridge LLC topology can work in both forward and reverse directions. When MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is used as a full-bridge LLC power device, it is necessary to ensure that the entire resonant cavity is in an inductive working area. The resonant cavity refers to a resonant circuit composed of resonant inductance, resonant capacitance, and excitation inductance. The inductive working area refers to the working mode in which the voltage and current on the bus are in phase and the voltage leads the current at a certain working frequency. The resonant cavity in the capacitive working area refers to the working mode in which the circuit is in phase and the current leads the voltage at a certain working frequency. However, when the resonant cavity works in the capacitive working area, a high current spike will be generated on the MOS tube in each working cycle, which will cause the MOS tube to overheat and break down, resulting in damage to the MOS tube. UTILITY MODEL CONTENTS

[0005] In view of the above problems, the utility model is proposed to provide a protection circuit and inverter of full-bridge resonant circuit to overcome the above problems or at least partially solve the above problems.

[0006] In order to solve the above problems, the utility model discloses a protection circuit of full -bridge resonant circuit, protection circuit includes: full -bridge resonant circuit, bus, sampling module, switch module, main control module,

[0007] Full -bridge resonant circuit passes through bus and power connection,

[0008] Sampling module is connected with bus, is used to gather the current value of bus,

[0009] The first connecting end of the switch module is connected with the power supply, and the second connecting end is connected with the full-bridge resonant circuit.

[0010] The main control module is connected with the sampling module and the switch module respectively, and is used for acquiring the current value of the bus collected by the sampling module.

[0011] Optionally, the main control module is used for judging whether the current value of the bus is greater than a preset current value.

[0012] Optionally, the switch module comprises a switch and a switch control circuit.

[0013] The first connecting end of the switch is connected with the power supply, and the second connecting end is connected with the full-bridge resonant circuit.

[0014] The switch control circuit is connected with the switch and the main control module respectively, and the main control module is used for controlling the working state of the switch through the switch control circuit.

[0015] Optionally, the protection circuit further comprises a fault alarm module.

[0016] The fault alarm module is connected with the switch module in parallel, the first end of the fault alarm module is connected with the power supply, the second end of the fault alarm module is connected with the full-bridge resonant circuit, and the fault alarm module is used for fault alarm when the switch module is disconnected.

[0017] Optionally, the fault alarm module comprises a first light emitting diode, a first resistor, a second light emitting diode and a second resistor.

[0018] One end of the first light emitting diode is arranged between the power supply and the switch module, and the other end is connected with the first resistor; one end of the first resistor is arranged between the switch module and the full-bridge resonant circuit; the first light emitting diode is used for conducting when the full-bridge resonant circuit works in the forward direction and the switch module is turned off.

[0019] The second light emitting diode is connected with the second resistor in series, and the second light emitting diode and the second resistor are connected with the first light emitting diode and the first resistor in parallel; the second light emitting diode is used for conducting when the full-bridge resonant circuit works in the reverse direction and the switch module is turned off.

[0020] Optionally, the full-bridge resonant circuit comprises a main full-bridge circuit, a resonant cavity and a secondary full-bridge circuit connected in sequence; the power supply comprises a first power supply and a second power supply; the bus comprises a first bus and a second bus;

[0021] The main full-bridge circuit is connected with the first power supply through the first bus;

[0022] The secondary full-bridge circuit is connected with the second power supply through the second bus.

[0023] Optionally, the main full-bridge circuit comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube;

[0024] The first electrode of the first switch tube is connected with the positive electrode of the first power supply, and the second electrode of the first switch tube is connected with the resonant cavity;

[0025] The first electrode of the second switch tube is connected with the second electrode of the first switch tube, and the second electrode of the second switch tube is connected with the negative electrode of the first power supply through the bus;

[0026] The first electrode of the third switch tube is arranged between the first electrode of the first switch tube and the first power supply, and the second electrode of the third switch tube is connected with the resonant cavity;

[0027] The first electrode of the fourth switch tube is arranged between the second electrode of the third switch tube and the resonant cavity, and the second electrode of the fourth switch tube is arranged between the second electrode of the second switch tube and the negative electrode of the power supply.

[0028] Optionally, the resonant cavity comprises a resonant capacitor, a resonant inductor and a transformer;

[0029] One side of the transformer is connected with the main full-bridge circuit through the resonant capacitor and the resonant inductor, and the other side of the transformer is connected with the secondary full-bridge circuit;

[0030] One end of the resonant capacitor is connected with the second electrode of the first switch tube, and the other end of the resonant capacitor is connected with the transformer.

[0031] One end of the resonant inductor is arranged between the second electrode of the third switch tube and the first electrode of the fourth switch tube, and the other end of the resonant inductor is connected with the transformer.

[0032] Optionally, the half-bridge circuit comprises a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube.

[0033] The first electrode of the fifth switch tube is connected with the positive electrode of the second power supply, and the second electrode of the fifth switch tube is connected with the transformer.

[0034] The first electrode of the sixth switch tube is connected with the second electrode of the fifth switch tube, and the second electrode of the sixth switch tube is connected with the negative electrode of the second power supply.

[0035] The first electrode of the seventh switch tube is arranged between the first electrode of the fifth switch tube and the positive electrode of the second power supply, and the second electrode of the seventh switch tube is connected with the transformer.

[0036] The first electrode of the eighth switch tube is arranged between the second electrode of the seventh switch tube and the transformer, and the second electrode of the eighth switch tube is arranged between the second electrode of the sixth switch tube and the negative electrode of the second power supply.

[0037] Optionally, the protection circuit further comprises a first filter capacitor and a second filter capacitor.

[0038] One end of the first filter capacitor is arranged between the positive electrode of the first power supply and the first electrode of the first switch tube, and the other end is grounded.

[0039] One end of the second filter capacitor is arranged between the positive electrode of the second power supply and the first electrode of the seventh switch tube, and the other end is grounded.

[0040] Optionally, one end of the sampling module is connected with the first busbar.

[0041] Correspondingly, the utility model discloses a kind of current transformer, and the current transformer includes the protection circuit of above-mentioned full-bridge resonant circuit.

[0042] The utility model includes following advantages:

[0043] The utility model discloses a kind of protection circuit of full-bridge resonant circuit, including full-bridge resonant circuit, bus, sampling module, switch module and main control module, full-bridge resonant circuit is connected with power supply by the bus, sampling module is connected with bus, for the current value of bus acquisition, the first connecting end of switch module is connected with power supply, second connecting end is connected with full-bridge resonant circuit, main control module is connected with sampling module and switch module respectively, for obtaining the current value of bus that sampling module collects;According to the current value of bus, control switch module disconnects the connection of full-bridge resonant circuit and the power supply.The main control module is disconnected by the current value of bus that sampling module collects according to the connection of full-bridge resonant circuit and power supply, to avoid the problem that power device on full-bridge resonant circuit is damaged when overcurrent occurs in bus, improve the stability and reliability of full-bridge resonant circuit. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 It is the structure schematic diagram of the protection circuit of full-bridge resonant circuit of the utility model embodiment;

[0045] Figure 2 It is the structure schematic diagram of another protection circuit of full-bridge resonant circuit of the utility model embodiment.

[0046] Reference signs: full-bridge resonant circuit 10, main full-bridge circuit 11, first switch tube 111, second switch tube 112, third switch tube 113, fourth switch tube 114, resonant cavity 12, resonant capacitor 121, resonant inductor 122, transformer 123, secondary full-bridge circuit 13, fifth switch tube 131, sixth switch tube 132, seventh switch tube 133, eighth switch tube 134, bus 20, first bus 21, second bus 22, sampling module 30, switch module 40, switch 41, switch control circuit 42, main control module 50, power supply 60, first power supply 61, second power supply 62, fault alarm module 70, first light emitting diode 71, first resistor 72, second light emitting diode 73, second resistor 74, first filter capacitor 80, second filter capacitor 81. DETAILED DESCRIPTION

[0047] In order to make the above-mentioned purpose, features and advantages of the utility model more obvious and easy to understand, the utility model is further explained in detail in combination with drawings and specific embodiment.

[0048] The full-bridge LLC topology is widely used, and the full-bridge LLC topology can be bidirectional. When a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is used as a full-bridge LLC power device, it is necessary to ensure that the entire resonant cavity is in an inductive working area. The resonant cavity refers to a resonant circuit composed of a resonant inductor, a resonant capacitor and an excitation inductor. The inductive working area refers to a working mode in which the voltage and current on the bus are in a state of voltage phase leading current at a certain working frequency. The resonant cavity in a capacitive working area refers to a working mode in which the circuit is in a state of current phase leading voltage at a certain working frequency. However, when the resonant cavity works in the capacitive working area, a high current spike will be generated on the MOS tube in each working cycle, resulting in overcurrent breakdown of the MOS tube and damage to the MOS tube.

[0049] One of the core ideas of the utility model is that the protection circuit of the full-bridge resonant circuit comprises a full-bridge resonant circuit, a bus, a sampling module, a switching module and a main control module. The main control module controls the switching module to disconnect the full-bridge resonant circuit and the power supply according to the current value of the bus collected by the sampling module, thereby avoiding the problem of damage to the power device on the full-bridge resonant circuit caused by overcurrent on the bus, and improving the stability and reliability of the full-bridge resonant circuit.

[0050] Referring to Figure 1 , a structure diagram of the protection circuit of the full-bridge resonant circuit is shown, which can specifically comprise the following structure:

[0051] The full-bridge resonant circuit 10, the bus 20, the sampling module 30, the switching module 40 and the main control module 50.

[0052] The full-bridge resonant circuit 10 is connected with the power supply 60 through the bus 20. The full-bridge resonant circuit 10 can be a full-bridge LLC circuit or a full-bridge CLLC circuit. The full-bridge resonant circuit 10 can work bidirectionally, that is, the full-bridge resonant circuit 10 can be a bidirectional full-bridge LLC circuit. When the full-bridge resonant circuit 10 works forwardly, the current flows from the power supply 60 to the full-bridge resonant circuit 10. When the full-bridge resonant circuit 10 works reversely, the current flows from the full-bridge resonant circuit 10 to the power supply 60.

[0053] The full-bridge LLC resonant circuit can operate in both forward and reverse bidirectional modes, which means it can not only transfer energy from the input to the output but also return energy from the output to the input in certain applications. This bidirectional operation capability makes the full-bridge LLC resonant circuit very useful in energy recovery, battery charging and discharging, and bidirectional power conversion applications. Forward operation mode: In the forward operation mode, energy is transferred from the input (usually a DC power source) to the output (load). At this time, the power switching devices are switched according to a specific switching frequency and duty cycle, so that the circuit operates near the resonant frequency, achieving high-efficiency energy transfer. Reverse operation mode: In the reverse operation mode, energy is returned from the output (load) to the input (DC power source). At this time, the switching operation of the power switching devices needs to be adjusted to ensure that energy can be returned from the output to the input. This mode is usually used in energy recovery, battery charging and discharging, and other applications.

[0054] To achieve bidirectional energy transfer, the power switching devices need to have bidirectional conduction capability. Usually, bidirectional MOSFETs or IGBTs are used, or single-directional switching devices and diodes are combined to achieve bidirectional conduction. The control strategy needs to be adjusted according to the different operation modes. In the forward operation mode, the control strategy mainly focuses on how to achieve high-efficiency energy transfer; in the reverse operation mode, the control strategy needs to ensure that energy can be returned from the output to the input while maintaining high efficiency. To ensure high-efficiency energy transfer in both bidirectional operation modes, the parameters of the resonant capacitor and inductor need to be optimized to ensure resonance in both forward and reverse operation modes.

[0055] The power supply 60 is a DC power supply, which is the energy source of the full-bridge LLC resonant circuit, providing the required DC power for the circuit. The DC power supply is usually connected to the input of the full-bridge LLC resonant circuit and controlled by the power switching devices to achieve high-efficiency energy conversion. The connection of the DC power supply to the full-bridge LLC resonant circuit includes: input filter, to reduce the noise and fluctuations of the input power, an input filter such as a capacitor and inductor filter circuit is usually added between the DC power supply and the full-bridge LLC resonant circuit; DC bus, the DC power supply is connected to the input of the full-bridge LLC resonant circuit through the DC bus, ensuring efficient transmission of electrical energy; power switching devices, the electrical energy of the DC power supply is controlled by the power switching devices to achieve high-efficiency energy conversion. The design and selection of the DC power supply need to consider factors such as voltage level, current capacity, stability and protection function to ensure the efficient and reliable operation of the circuit.

[0056] Full-Bridge LLC Resonant Converter, also known as Full-Bridge LLC Resonant Converter, is a specific circuit topology that uses a resonant circuit to achieve soft switching, reduce switching loss, and improve efficiency. Full-Bridge LLC Resonant Converter mainly consists of the following parts: Full-Bridge Inverter, composed of four power switching devices (usually MOSFET or IGBT), used to convert DC voltage to high-frequency AC voltage; Resonant Network, including resonant inductance (Lr), resonant capacitance (Cr) and magnetizing inductance (Lm) of transformer, used to achieve soft switching and voltage conversion; Output Rectifier Circuit, which converts high-frequency AC voltage to DC voltage, usually using diodes or synchronous rectifiers. The working mode of Full-Bridge LLC Resonant Converter mainly includes two types: Resonant Mode, working near the resonant frequency, achieving zero voltage switching (ZVS) and zero current switching (ZCS), reducing switching loss; Non-resonant mode, working at non-resonant frequency, may cause hard switching, increasing switching loss. Key components include: Resonant Inductance, together with resonant capacitance, forms a resonant circuit, determines the resonant frequency; Resonant Capacitance, together with resonant inductance, forms a resonant circuit, determines the resonant frequency; Magnetizing Inductance, the magnetizing inductance of the transformer, affects the Q value of the resonant circuit and the voltage gain; Power switching device, usually MOSFET or IGBT, needs to select appropriate rated voltage and current to ensure reliability under high-frequency switching; Output rectifier, usually diode or synchronous rectifier, used to convert high-frequency AC voltage to DC voltage.

[0057] Full-Bridge CLLC Resonant Converter, also known as Full-Bridge CLLC Resonant Converter, is an improved resonant converter that adds additional capacitors to the traditional LLC resonant converter to further optimize circuit performance. Full-Bridge CLLC Resonant Converter mainly consists of the following parts: Full-Bridge Inverter, composed of four power switching devices (usually MOSFET or IGBT), used to convert DC voltage to high-frequency AC voltage; Resonant Network, including two resonant inductors (Lr1 and Lr2), two resonant capacitors (Cr1 and Cr2) and magnetizing inductance (Lm) of transformer, used to achieve soft switching and voltage conversion; Output Rectifier Circuit, which converts high-frequency AC voltage to DC voltage, usually using diodes or synchronous rectifiers.

[0058] Bus 20 refers to a group of wires or conductors that are used to transmit electrical energy or signals. Bus plays a role in connecting different components and devices in a circuit, ensuring efficient and reliable transmission of electrical energy or signals. The types of bus include: DC bus, used to transmit DC electrical energy. In power electronic converters, DC bus is usually connected to the input power source and power switching devices; AC bus, used to transmit AC electrical energy. In inverters or frequency converters, AC bus connects power switching devices and output loads; signal bus, used to transmit control signals or data signals. Signal bus is usually used to connect control circuits and power switching devices, such as feedback signals. In full-bridge LLC resonant circuits, bus is mainly used to connect input power source, power switching devices, resonant capacitor, resonant inductor and transformer. Specific applications include: DC bus, connecting input power source and power switching devices, ensuring efficient transmission of DC electrical energy; resonant bus, connecting resonant capacitor and resonant inductor, forming a resonant circuit, ensuring stable resonant frequency; transformer bus: connecting the primary and secondary windings of the transformer, ensuring efficient energy transmission. Bus plays a key role in connecting power electronic systems, ensuring efficient transmission of electrical energy or signals. In full-bridge LLC resonant circuits, the design and selection of bus need to consider current capacity, voltage level, heat dissipation performance and mechanical strength, etc. to ensure efficient and reliable operation of the circuit.

[0059] The sampling module 30 is connected to the bus 20 for collecting the current value of the bus. The full-bridge resonant circuit 10 is connected to the power supply 60 through the bus 20, and the sampling module 30 collects the current on the bus 20 connecting the full-bridge resonant circuit 10 and the power supply 60.

[0060] The first connection end of the switching module 40 is connected to the power supply 60, and the second connection end is connected to the full-bridge resonant circuit 10.

[0061] The main control module is connected to the sampling module 30 and the switching module 40 respectively, for obtaining the current value of the bus 20 collected by the sampling module 30; according to the current value of the bus 20, the switching module 40 is controlled to disconnect the connection between the full-bridge resonant circuit 10 and the power supply 60.

[0062] The utility model discloses an embodiment of a kind of protection circuit of full-bridge resonant circuit, including full-bridge resonant circuit, bus, sampling module, switch module and main control module, full-bridge resonant circuit is connected with power supply by the bus, sampling module is connected with bus, for the current value of bus acquisition, the first connecting end of switch module is connected with power supply, second connecting end is connected with full-bridge resonant circuit, main control module is connected with sampling module and switch module respectively, for obtaining the current value of bus that sampling module collects;According to the current value of bus, control switch module disconnects the connection of full-bridge resonant circuit and the power supply.The main control module controls switch module to disconnect the connection of full-bridge resonant circuit and power supply according to the current value of bus that sampling module collects, to avoid the problem that power device on full-bridge resonant circuit is damaged when overcurrent occurs in bus, improve the stability and reliability of full-bridge resonant circuit.

[0063] In the utility model embodiment, the main control module 50 is used for judging whether the current value of the bus 20 is greater than a preset current value, and if the current value of the bus 20 is greater than the preset current value, the switch module 40 is controlled to disconnect the connection of the full-bridge resonant circuit 10 and the power supply 50.

[0064] Specifically, the full-bridge resonant circuit 10 can work in both directions, and the power device of the full-bridge resonant circuit 10 can be a MOS tube. The full-bridge resonant circuit 10 needs to ensure that the entire resonant cavity of the full-bridge resonant circuit 10 is in an inductive working area. The resonant cavity refers to a resonant circuit composed of a resonant inductor, a resonant capacitor, and an excitation inductor. The inductive working area refers to a working mode in which the voltage and current on the bus are in a state of voltage phase leading current under a certain working frequency. When the entire resonant cavity of the full-bridge resonant circuit 10 is in the inductive working area, the MOS tube is ensured to work under the condition of zero-voltage switching, thereby reducing switching loss, improving efficiency, and prolonging the service life of the device. However, when the entire resonant cavity of the full-bridge resonant circuit 10 is not in the inductive working area but in a capacitive working area, the capacitive working area refers to a working mode in which the circuit is in a state of current phase leading voltage under a certain working frequency. At this time, a high current spike will be generated on the two groups of MOS tubes in each working period, causing the MOS tube to be overcurrent breakdown and damaged. The current spike also far exceeds the overcurrent size allowed by the bus. The main control module 50 judges whether the current value of the bus 20 is greater than a preset current value, and controls the switch module 40 to disconnect the connection of the full-bridge resonant circuit 10 and the power supply 60 when the current value of the bus 20 is greater than the preset current value, thereby protecting the MOS tube from overcurrent breakdown when the full-bridge resonant circuit 10 enters the capacitive working area.

[0065] The capacitive operating area refers to the operating area in which the circuit exhibits capacitive characteristics, i.e., the current leads the voltage. This situation usually occurs when the switching frequency is higher than the resonance frequency. The characteristics of the capacitive operating area are: the current leads the voltage, in the capacitive operating area, the phase of the current leads the phase of the voltage. This means that the capacitive effect in the circuit dominates; the switching device stress increases, as the current leads the voltage, the switching device may be subjected to a large current stress when turned off, which can lead to increased switching losses and reduced device lifetime; the resonance current increases, in the capacitive operating area, the resonance current can increase, leading to increased losses in the circuit; the efficiency is reduced, due to the phase relationship between the current and the voltage, the efficiency in the capacitive operating area is usually lower than in the inductive operating area.

[0066] The capacitive operating area is a working state that needs to be avoided in the LLC resonant converter, because it can cause problems such as reduced efficiency, increased switching device stress, power device overcurrent breakdown, etc.

[0067] Referring to Figure 2 , another structure diagram of the protection circuit of the full-bridge resonant circuit is shown, the switch module 40 includes a switch 41 and a switch control circuit 42.

[0068] The first connection end of the switch 41 is connected with the power supply 60, and the second connection end is connected with the full-bridge resonant circuit 10.

[0069] The switch 41 can be a relay, a MOSFET, an IGBT (Insulated Gate Bipolar Transistor), a SIC (Silicon Carbide), a GaN (Gallium Nitride) switch tube, etc.

[0070] A relay is an electrical control device that controls the switching operation of a large current or high voltage through a small current or voltage. The basic structure of a relay includes the following parts: a coil (Coil) that generates a magnetic field through current to control the switching state of the relay; contacts (Contacts) for connecting or disconnecting the circuit, usually including normally open contacts (NO), normally closed contacts (NC), and transfer contacts (COM); a magnetic core (Magnetic Core) that enhances the magnetic field generated by the coil to improve the sensitivity of the relay; a spring (Spring) that maintains the initial state of the contacts and restores the contact state after the magnetic field disappears.

[0071] The switch control circuit 42 is connected with the switch 41 and the main control module 50 respectively, and the main control module 50 is used for controlling the working state of the switch 41 through the switch control circuit 42.

[0072] The switch control circuit 42 can control the switch 41 to be turned on or turned off, and the main control module 50 controls the switch 41 to be turned on or turned off according to the current value of the bus 20, that is, when the full-bridge resonant circuit 10 enters the capacitive working area, the overcurrent peak of the MOS tube appears when the MOS tube is turned on, and the current peak exceeds the allowable overcurrent size of the bus, the switch control circuit 42 controls the switch 41 to be turned off, so as to disconnect the full-bridge resonant circuit 10 and the power supply 60, thereby protecting the MOS tube power device from being burned out, and when the current value of the bus 20 is not greater than the preset current value, that is, when the full-bridge resonant circuit 10 works normally, the main control module 50 controls the switch 41 to be turned on through the switch control circuit 42.

[0073] In the embodiment of the utility model, the protection circuit further includes a fault alarm module 70;

[0074] The fault alarm module 70 is connected in parallel with the switch module 40, the first end of the fault alarm module 70 is connected with the power supply 60, and the second end of the fault alarm module 70 is connected with the full-bridge resonant circuit 10, so as to perform fault alarm when the switch module 40 is turned off.

[0075] When the switch 41 in the switch module 40 is turned on, that is, when the full-bridge resonant circuit 10 works normally, the fault alarm module 70 is short-circuited, and when the switch 41 of the switch module 40 is turned off, that is, when the full-bridge resonant circuit 10 works in the capacitive working area, the fault alarm module 70 starts to work and performs fault alarm.

[0076] In the embodiment of the utility model, the fault alarm module 70 includes a first light-emitting diode 71, a first resistor 72, a second light-emitting diode 73, a second resistor 74 and a capacitor 75.

[0077] One end of the first light-emitting diode 71 is arranged between the power supply 60 and the switch module 40, and the other end is connected with the first resistor 72; one end of the first resistor 72 is arranged between the switch module 40 and the full-bridge resonant circuit 10; and the first light-emitting diode 71 is used to be turned on when the full-bridge resonant circuit 10 works normally and the switch module 40 is turned off.

[0078] The first light-emitting diode 71 emits visible light when current passes through, and the light-emitting diode has the advantages of high efficiency, long service life and low power consumption, and is widely used in the fields of lighting, display and indication, and the current flow direction of the first light-emitting diode 71 is that the first light-emitting diode 71 is bright when current flows from the power supply to the first light-emitting diode 71.

[0079] The first resistor 72 is a current limiting resistor, the main function of the current limiting resistor is to limit the current through its resistance value, prevent the components in the circuit from overloading or damage, the basic working principle of the current limiting resistor is to use Ohm's law, limit the current through the resistance value, by selecting the appropriate resistance value, the current can be limited within a safe range.

[0080] When the full-bridge resonant circuit 10 is in a forward working state, if the full-bridge resonant circuit 10 enters a capacitive working area, then the overcurrent of the power device MOS tube in the full-bridge resonant circuit 10 appears a sharp peak when it is turned on, the size of the current peak greatly exceeds the size of the overcurrent allowed by the bus, at this time, the main control module 50 detects that the bus current appears overcurrent through the sampling module 30, and controls the switch 41 to be opened through the switch control circuit 42, at this time, the current flows from the power supply 60 to the first light emitting diode 71, which meets the current flow direction of the first light emitting diode 71 turned on, the first light emitting diode 71 is turned on and brightened, and the first resistor 72 can limit the bus current to a very low level, protecting the power device from being burned out. The brightening of the first light emitting diode 71 in the fault alarm module 70 means that the full-bridge resonant circuit 10 enters the capacitive working area when it is in the forward working state, at this time, the power device of the full-bridge resonant circuit 10 has the risk of overcurrent breakdown damage.

[0081] The second light emitting diode 73 is connected in series with the second resistor 74, the second light emitting diode 73 and the second resistor 74 are connected in parallel with the first light emitting diode 71 and the first resistor 72, the second light emitting diode 73 is used to be turned on when the full-bridge resonant circuit 10 is reversely working and the switch module 40 is opened, and the capacitor 75 is connected in parallel with the second light emitting diode 73 and the second resistor 74 and the first light emitting diode 71 and the first resistor 72.

[0082] The second light emitting diode 73 emits visible light when current passes through it, the light emitting diode has the advantages of high efficiency, long service life, low power consumption, etc., and is widely used in lighting, display, indication and other fields, and the current flow direction of the second light emitting diode 73 is from the full-bridge resonant circuit 10 to the second light emitting diode 73.

[0083] The second resistor 74 is a current limiting resistor, the main function of the current limiting resistor is to limit the current through its resistance value, prevent the components in the circuit from overloading or damage, the basic working principle of the current limiting resistor is to use Ohm's law, limit the current through the resistance value, by selecting the appropriate resistance value, the current can be limited within a safe range.

[0084] When the full-bridge resonant circuit 10 is in the reverse working state, if the full-bridge resonant circuit 10 enters the capacitive working area, the overcurrent of the power device MOS tube when turned on appears a sharp peak, and the size of the current peak greatly exceeds the overcurrent size allowed by the bus, at this time, the main control module 50 detects that the bus current appears overcurrent through the sampling module 30, and controls the switch 41 to be disconnected through the switch control circuit 42, at this time, the current flows from the full-bridge resonant circuit 10 to the power supply 60, which meets the current direction of the second light emitting diode 73 being turned on, the second light emitting diode 73 is turned on and brightened, and the second resistor 74 can limit the bus current to a very low level, protecting the power device from being burned out. The second light emitting diode 73 in the fault alarm module 70 is brightened, which means that the full-bridge resonant circuit 10 enters the capacitive working area when in the reverse working state, at this time, the power device of the full-bridge resonant circuit 10 has the risk of overcurrent breakdown damage.

[0085] The tester can judge which working mode of the full-bridge resonant circuit 10 enters the capacitive working area by visually observing the fault alarm module 70, so as to troubleshoot.

[0086] In the embodiment of the utility model, the full-bridge resonant circuit 10 includes main full-bridge circuit 11, resonant cavity 12 and secondary full-bridge circuit 13 connected in sequence, the power supply 60 includes first power supply 61 and second power supply 62, and the bus 20 includes first bus 21 and second bus 22.

[0087] The main full-bridge circuit 11 is connected with the first power supply 61 through the first bus 21.

[0088] The secondary full-bridge circuit 13 is connected with the second power supply 62 through the second bus 22.

[0089] Exemplarily, the left side of the resonant cavity 12 is the main full-bridge circuit 11, the power supply on the left side is the first power supply 61, the bus on the left side is the first bus 21, the right side of the resonant cavity 12 is the secondary full-bridge circuit 13, the power supply on the right side is the second power supply 62, and the bus on the right side is the second bus 22.

[0090] In the embodiment of the utility model, the main full-bridge circuit 11 includes first switch tube 111, second switch tube 112, third switch tube 113 and fourth switch tube 114, wherein the first switch tube 111, the second switch tube 112, the third switch tube 113 and the fourth switch tube 114 can be MOS tube power devices.

[0091] The first electrode of the first switch tube 111 is connected with the positive electrode of the first power supply 61, and the second electrode of the first switch tube 111 is connected with the resonant cavity 12.

[0092] The first electrode of the second switch tube 112 is connected with the second electrode of the first switch tube 111, and the second electrode of the second switch tube 112 is connected with the negative electrode of the first power supply 61 through the first bus 21.

[0093] The first electrode of the third switch tube 113 is arranged between the first electrode of the first switch tube 111 and the first power supply 61, and the second electrode of the third switch tube 113 is connected with the resonant cavity 12.

[0094] The first electrode of the fourth switch tube 114 is arranged between the second electrode of the third switch tube 113 and the resonant cavity 12, and the second electrode of the fourth switch tube 114 is arranged between the second electrode of the second switch tube 112 and the negative electrode of the first power supply 61.

[0095] When the full-bridge resonant circuit 10 is working in the forward direction, the first switch tube 111 and the fourth switch tube 114 are turned on, the second switch tube 112 and the third switch tube 113 are turned off, and the current flows from the positive bus pole of the first bus 21 to the negative bus pole of the first bus 21 through the first switch tube 111 and the fourth switch tube 114, and the positive bus pole of the first bus 21 is connected with the positive electrode of the first power supply 61, and the negative bus pole of the first bus 21 is connected with the negative electrode of the first power supply 61.

[0096] In the embodiment of the utility model, the resonant cavity 12 includes resonant capacitor 121, resonant inductor 122 and transformer 123.

[0097] One side of the transformer 123 is connected with the main full-bridge circuit 11 through the resonant capacitor 121 and the resonant inductor 122, and the other side of the transformer 123 is connected with the secondary full-bridge circuit 13.

[0098] One end of the resonant capacitor 121 is connected with the second electrode of the first switch tube 111, and the other end of the resonant capacitor 121 is connected with the transformer 123.

[0099] One end of the resonant inductor 122 is arranged between the second electrode of the third switch tube 113 and the first electrode of the fourth switch tube 114, and the other end of the resonant inductor 122 is connected with the transformer 123.

[0100] The resonant capacitor 121 is used for storing and releasing electric energy, and forms a resonant circuit with the resonant inductor 122, the resonant inductor 122 is used for storing and releasing magnetic energy, and forms a resonant circuit with the resonant capacitor 121, the transformer 123 is used for voltage conversion and electrical isolation, and includes a primary winding and a secondary winding, and the resonant cavity 12 realizes efficient energy transmission and soft switching technology through resonance.

[0101] In the embodiment of the utility model, the secondary full bridge circuit includes fifth switch tube 131, sixth switch tube 132, seventh switch tube 133 and eighth switch tube 134. Fifth switch tube 131, sixth switch tube 132, seventh switch tube 133 and eighth switch tube 134 can be MOS tube, also can be diode, the embodiment of the utility model does not make the limitation to this.

[0102] The first electrode of the fifth switch tube 131 is connected with the positive pole of the second power supply 62, and the second electrode of the fifth switch tube 131 is connected with the transformer 123.

[0103] The first electrode of the sixth switch tube 132 is connected with the second electrode of the fifth switch tube 131, and the second electrode of the sixth switch tube 132 is connected with the negative pole of the second power supply 62.

[0104] The first electrode of the seventh switch tube 133 is arranged between the first electrode of the fifth switch tube 132 and the positive pole of the second power supply 62, and the second electrode of the seventh switch tube 133 is connected with the transformer 123.

[0105] The first electrode of the eighth switch tube 134 is arranged between the second electrode of the seventh switch tube 133 and the transformer 123, and the second electrode of the eighth switch tube 134 is arranged between the second electrode of the sixth switch tube 132 and the negative pole of the second power supply 62.

[0106] In the embodiment of the utility model, the protection circuit further includes first filter capacitor 80 and second

[0107] filter capacitor 81.

[0108] The main function of the filter capacitor is to remove the ripple and noise in the voltage or current, provide stable DC voltage or current, and the basic working principle of the filter capacitor is to use the charging and discharging characteristics of the capacitor to smooth the voltage or current waveform. When the voltage rises, the filter capacitor charges and stores electric energy. When the voltage drops, the filter capacitor discharges and releases the stored electric energy, smooths the voltage waveform, removes the ripple in the voltage or current, makes it close to pure DC, and also reduces the high-frequency noise in the voltage or current, improves the signal quality.

[0109] One end of the first filter capacitor 80 is arranged between the positive pole of the first power supply 61 and the first electrode of the first switch tube 111, and the other end is grounded.

[0110] One end of the second filter capacitor 81 is arranged between the positive pole of the second power supply 62 and the first electrode of the seventh switch tube 133, and the other end is grounded.

[0111] In the embodiment of the utility model, one end of the sampling module 30 is connected with the first bus 21.

[0112] When the resonant cavity 12 enters the capacitive working area, the current flows from the positive bus to the negative bus through the first switch tube 111, the fourth switch tube 114 (forward) or the second switch tube 112, the third switch tube 113 (negative), as long as the sampling module 30 is on the main power bus, it can be on the positive or negative bus, and the sampling resistance can be added at the corresponding position of the bus to realize it.

[0113] In order to avoid the capacitive working area, it is usually necessary to ensure that the switching frequency is lower than or equal to the resonant frequency, and the specific measures include: adjusting the switching frequency, by controlling the switching frequency, so that it is lower than or equal to the resonant frequency, which can avoid entering the capacitive working area; optimizing the resonant parameters, by adjusting the values of the resonant capacitor and inductor, the resonant frequency is optimized to match the switching frequency; using frequency control strategy: using appropriate frequency control strategy, ensuring that the circuit always works in the inductive working area.

[0114] The tester can determine which working mode the full-bridge resonant circuit 10 enters the capacitive working area by visually observing the fault alarm module 70, when the first light-emitting diode 71 is on, the full-bridge resonant circuit 10 enters the capacitive working area in the forward working state, when the second light-emitting diode 73 is on, the full-bridge resonant circuit 10 enters the capacitive working area in the negative working state.

[0115] And adjust the switching frequency, the resonant cavity parameter. When the fault is eliminated, power on again, the main control module 50 controls the switch 41 to be closed through the switch control circuit 42, and the fault alarm module 70 does not work because it is short-circuited by the switch module 40.

[0116] Specifically, the switching frequency is modified by changing the value of the modulation wave of the internal main control chip of the modulation main control module 50 and the reference clock signal. The resonant cavity parameters include the excitation inductance, the resonant inductance, and the resonant capacitance, which can be adjusted by replacing the resonant capacitor 121, the resonant inductor 122 and the transformer 123.

[0117] In the embodiment of the utility model, when the bidirectional full-bridge LLC circuit enters the capacitive working area, the MOSFET is protected from being broken down by overcurrent, and the experimental tester can quickly find and judge that the resonant cavity enters the capacitive working area, and timely adjust the working frequency and the resonant cavity device parameters.

[0118] The embodiment of the utility model also provides a converter, which comprises the protection circuit of the full-bridge resonant circuit.

[0119] Finally, it needs to be explained that in this document, the relational terms such as first and second and the like can merely be used to differentiate one entity or action from another, without necessarily requiring or implying any actual relationship or order between or among the entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0120] The above has carried out the detailed introduction to the protection circuit and the current transformer of the full-bridge resonant circuit provided by the utility model, the principle and the implementation mode of the utility model have been set forth in this document by applying the specific example, the above embodiment is only for helping the understanding of the method and the core thought of the utility model; simultaneously, for the general technical personnel of the field, according to the thought of the utility model, there will be the change in the specific implementation mode and the application range, and the above is stated, the content of the specification should not be understood as the limitation of the utility model.

Claims

1. A protection circuit for a full-bridge resonant circuit, characterized by, The protection circuit comprises a full-bridge resonant circuit, a bus, a sampling module, a switching module and a main control module; The full-bridge resonant circuit is connected with the power supply through the bus; The sampling module is connected with the bus and is used for collecting the current value of the bus; The first connecting end of the switching module is connected with the power supply, and the second connecting end is connected with the full-bridge resonant circuit; The main control module is connected with the sampling module and the switching module respectively, is used for obtaining the current value of the bus collected by the sampling module, and controls the switching module to disconnect the full-bridge resonant circuit from the power supply according to the current value of the bus.

2. The protection circuit of claim 1, wherein, The main control module is used for judging whether the current value of the bus is greater than a preset current value, and if the current value of the bus is greater than the preset current value, the main control module controls the switching module to disconnect the full-bridge resonant circuit from the power supply.

3. The protection circuit of claim 1, wherein, The switching module comprises a switch and a switch control circuit; The first connecting end of the switch is connected with the power supply, and the second connecting end is connected with the full-bridge resonant circuit; The switch control circuit is connected with the switch and the main control module respectively, and the main control module is used for controlling the working state of the switch through the switch control circuit.

4. The protection circuit of claim 1, wherein, The protection circuit further comprises a fault alarm module; The fault alarm module is connected with the switching module in parallel, the first end of the fault alarm module is connected with the power supply, and the second end of the fault alarm module is connected with the full-bridge resonant circuit, so as to perform fault alarm when the switching module is disconnected.

5. The protection circuit of claim 4, wherein, The fault alarm module comprises a first light emitting diode, a first resistor, a second light emitting diode and a second resistor; One end of the first light emitting diode is arranged between the power supply and the switching module, and the other end is connected with the first resistor; one end of the first resistor is arranged at the connection between the switching module and the full-bridge resonant circuit; and the first light emitting diode is used for turning on when the full-bridge resonant circuit works in a forward direction and the switching module is disconnected. The second light emitting diode is connected with the second resistor in series, and the second light emitting diode and the second resistor are connected with the first light emitting diode and the first resistor in parallel; and the second light emitting diode is used for turning on when the full-bridge resonant circuit works in a reverse direction and the switching module is disconnected. The full-bridge resonant circuit comprises a main full-bridge circuit, a resonant cavity and a secondary full-bridge circuit connected in sequence; the power supply comprises a first power supply and a second power supply; and the bus comprises a first bus and a second bus; 6. The protection circuit of claim 1, wherein, The main full-bridge circuit is connected with the first power supply through the first bus; The secondary full-bridge circuit is connected with the second power supply through the second bus. The main full-bridge circuit comprises a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; 7. The protection circuit of claim 6, wherein, The first electrode of the first switch tube is connected with the positive pole of the first power supply, and the second electrode of the first switch tube is connected with the resonant cavity; The first electrode of the second switch tube is connected with the second electrode of the first switch tube, and the second electrode of the second switch tube is connected with the negative pole of the first power supply through the bus; The first electrode of the third switch tube is connected with the second electrode of the second switch tube, and the second electrode of the third switch tube is connected with the positive pole of the first power supply through the first bus; The first electrode of the fourth switch tube is connected with the second electrode of the third switch tube, and the second electrode of the fourth switch tube is connected with the negative pole of the first power supply through the second bus. The first electrode of the third switch is arranged between the first electrode of the first switch and the first power supply, and the second electrode of the third switch is connected with the resonant cavity; The first electrode of the fourth switch is arranged between the second electrode of the third switch and the resonant cavity, and the second electrode of the fourth switch is arranged between the second electrode of the second switch and the negative electrode of the power supply.

8. The protection circuit of claim 7, wherein, The resonant cavity comprises a resonant capacitor, a resonant inductor and a transformer; One side of the transformer is connected with the main full-bridge circuit through the resonant capacitor and the resonant inductor, and the other side of the transformer is connected with the secondary full-bridge circuit; One end of the resonant capacitor is connected with the second electrode of the first switch, and the other end of the resonant capacitor is connected with the transformer; One end of the resonant inductor is arranged between the second electrode of the third switch and the first electrode of the fourth switch, and the other end of the resonant inductor is connected with the transformer.

9. The protection circuit of claim 8, wherein, The secondary full-bridge circuit comprises a fifth switch, a sixth switch, a seventh switch and an eighth switch; The first electrode of the fifth switch is connected with the positive electrode of the second power supply, and the second electrode of the fifth switch is connected with the transformer; The first electrode of the sixth switch is connected with the second electrode of the fifth switch, and the second electrode of the sixth switch is connected with the negative electrode of the second power supply; The first electrode of the seventh switch is arranged between the first electrode of the fifth switch and the positive electrode of the second power supply, and the second electrode of the seventh switch is connected with the transformer; The first electrode of the eighth switch is arranged between the second electrode of the seventh switch and the transformer, and the second electrode of the eighth switch is arranged between the second electrode of the sixth switch and the negative electrode of the second power supply.

10. The protection circuit of claim 9, wherein, The protection circuit further comprises a first filter capacitor and a second filter capacitor; One end of the first filter capacitor is arranged between the positive electrode of the first power supply and the first electrode of the first switch, and the other end is grounded; One end of the second filter capacitor is arranged between the positive electrode of the second power supply and the first electrode of the seventh switch, and the other end is grounded.

11. The protection circuit of claim 6, wherein, One end of the sampling module is connected with the first busbar.

12. A current transformer, characterized by A protection circuit comprising the full-bridge resonant circuit according to any one of claims 1-11.

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