Protection circuit of full-bridge resonance circuit and converter

Abstract

The embodiment of the invention provides a protection circuit of a full-bridge resonance circuit and a converter, the protection circuit comprises the 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 used for switching the current value of the bus. 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 present invention relates to the technical field of electronic circuits, and in particular to a protection circuit and a converter for a full-bridge resonant circuit. Background Art

[0002] With the development of power electronics technology, the operating frequency of power switching devices has increased from several thousand hertz to several hundred kilohertz. This change reduces the energy to be transferred by inductive devices (such as inductors) in a single cycle, thereby significantly reducing the size of the inductor. However, as the switching frequency increases, the switching loss of the entire system and the peak impact voltage and current generated by the switching devices during the switching process also increase, which has an adverse effect on the working efficiency and electromagnetic interference (EMI) of the entire machine.

[0003] In order to deal with the problems of excessive switching loss and electromagnetic interference, LLC (Inductor-Capacitor-Transformer) and CLLC (Capacitor-Inductor-Inductor-Capacitor) circuits are usually relied upon to implement soft switching technology. The core of soft switching technology is to ensure that there is no overlapping area between the source and drain current and voltage waveforms when the switch tube is turned on, thereby achieving zero voltage or zero current turning 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] At present, the full-bridge LLC topology is widely used in converter products above 1 kW, and the full-bridge LLC topology can work in both forward and reverse directions. When using MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) as a full-bridge LLC power device, it is necessary to ensure that the entire resonant cavity is in the 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 the working mode in which the voltage and current on the busbar of the resonant cavity are ahead of the current at a certain working frequency. The resonant cavity is in the capacitive working area, which means that the circuit is in a working mode in which the current phase is ahead of the voltage at a certain working frequency. However, when the resonant cavity works in the capacitive working area, a higher current spike will be generated on the MOS tube in each working cycle, resulting in overcurrent breakdown of the MOS tube and thus damage to the MOS tube. Summary of the invention

[0005] In view of the above problems, embodiments of the present invention are proposed to provide a protection circuit and a converter for a full-bridge resonant circuit that overcome the above problems or at least partially solve the above problems.

[0006] In order to solve the above problems, an embodiment of the present invention discloses a protection circuit of a full-bridge resonant circuit, wherein the protection circuit comprises: a full-bridge resonant circuit, a bus, a sampling module, a switch module, and a main control module;

[0007] The full-bridge resonant circuit is connected to a power source via the bus bar;

[0008] The sampling module is connected to the bus and is used to collect the current value of the bus;

[0009] The first connection end of the switch module is connected to the power supply, and the second connection end is connected to the full-bridge resonant circuit;

[0010] The main control module is connected to the sampling module and the switch module respectively, and is used to obtain the current value of the bus collected by the sampling module; according to the current value of the bus, the switch module is controlled to disconnect the full-bridge resonant circuit from the power supply.

[0011] Optionally, the main control module is used to determine whether the current value of the bus is greater than a preset current value. If the current value of the bus is greater than the preset current value, the switch module is controlled to disconnect the full-bridge resonant circuit from the power supply.

[0012] Optionally, the switch module includes a switch and a switch control circuit;

[0013] The first connection end of the switch is connected to the power supply, and the second connection end is connected to the full-bridge resonant circuit;

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

[0015] Optionally, the protection circuit further includes a fault alarm module;

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

[0017] Optionally, the fault alarm module includes 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 to 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 to be turned on when the full-bridge resonant circuit is working in the forward direction and the switch module is disconnected;

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

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

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

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

[0023] Optionally, the main full-bridge circuit includes 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 to the positive electrode of the first power supply, and the second electrode of the first switch tube is connected to the resonant cavity;

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

[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 to 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 includes a resonant capacitor, a resonant inductor and a transformer;

[0029] One side of the transformer is connected to the primary full-bridge circuit via the resonant capacitor and the resonant inductor, and the other side of the transformer is connected to the secondary full-bridge circuit;

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

[0031] One end of the resonant inductor is disposed 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 to the transformer.

[0032] Optionally, the sub-full-bridge circuit includes a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube;

[0033] A first electrode of the fifth switch tube is connected to the positive electrode of the second power supply, and a second electrode of the fifth switch tube is connected to the transformer;

[0034] The first electrode of the sixth switch tube is connected to the second electrode of the fifth switch tube, and the second electrode of the sixth switch tube is connected to 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 to 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 includes 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 disposed 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 to the first bus.

[0041] Correspondingly, an embodiment of the present invention discloses a converter, which includes the protection circuit of the full-bridge resonant circuit.

[0042] The embodiments of the present invention include the following advantages:

[0043] A protection circuit for a full-bridge resonant circuit according to an embodiment of the present invention comprises a full-bridge resonant circuit, a bus, a sampling module, a switch module and a main control module, wherein the full-bridge resonant circuit is connected to a power supply via the bus, the sampling module is connected to the bus and is used to collect the current value of the bus, the first connection end of the switch module is connected to the power supply, and the second connection end is connected to the full-bridge resonant circuit, the main control module is respectively connected to the sampling module and the switch module and is used to obtain the current value of the bus collected by the sampling module; 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, thereby avoiding the problem of damage to the power devices on the full-bridge resonant circuit when an overcurrent occurs in the bus, thereby improving the stability and reliability of the full-bridge resonant circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a structural schematic diagram of a protection circuit of a full-bridge resonant circuit according to an embodiment of the present invention;

[0045] Figure 2 It is a schematic structural diagram of another protection circuit of a full-bridge resonant circuit according to an embodiment of the present invention.

[0046] Figure numerals: 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 objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] The full-bridge LLC topology is widely used, and the full-bridge LLC topology can work in both forward and reverse directions. When using MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) as a full-bridge LLC power device, it is necessary to ensure that the entire resonant cavity is in the 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 the working mode in which the voltage and current on the busbar of the resonant cavity are ahead of the current at a certain working frequency. The resonant cavity is in the capacitive working area, which means that the circuit is ahead of the voltage at a certain working frequency. However, when the resonant cavity works in the capacitive working area, a higher current spike will be generated on the MOS tube in each working cycle, causing overcurrent breakdown of the MOS tube and thus damage to the MOS tube.

[0049] One of the core concepts of an embodiment of the present invention is that a protection circuit for a full-bridge resonant circuit includes a full-bridge resonant circuit, a bus, a sampling module, a switch module and a main control module. 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, thereby avoiding the problem of damage to power devices on the full-bridge resonant circuit when overcurrent occurs in the bus, thereby improving the stability and reliability of the full-bridge resonant circuit.

[0050] Reference Figure 1 , shows a schematic diagram of the structure of a protection circuit of a full-bridge resonant circuit according to an embodiment of the present invention, which may specifically include the following structure:

[0051] Full-bridge resonant circuit 10 , bus 20 , sampling module 30 , switch module 40 , main control module 50 .

[0052] The full-bridge resonant circuit 10 is connected to the power supply 60 through the bus 20, wherein the full-bridge resonant circuit 10 can be a full-bridge LLC circuit or a full-bridge CLLC circuit, and the full-bridge resonant circuit 10 can work in both forward and reverse directions, that is, the full-bridge resonant circuit 10 can be a bidirectional full-bridge LLC circuit. When the full-bridge resonant circuit 10 works in the forward direction, the current flows from the power supply 60 to the full-bridge resonant circuit 10, and when the full-bridge resonant circuit 10 works in the reverse direction, 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 working modes, which means that it can not only transfer energy from the input to the output, but also return energy from the output to the input in some applications. This bidirectional working capability makes the full-bridge LLC resonant circuit very useful in applications such as energy recovery, battery charging and discharging, and bidirectional power conversion. Forward working mode: In the forward working mode, energy is transferred from the input (usually a DC power supply) to the output (load). At this time, the power switching device switches at a specific switching frequency and duty cycle, so that the circuit operates near the resonant frequency, thereby achieving high-efficiency energy transmission. Reverse working mode: In the reverse working mode, energy is returned from the output (load) to the input (DC power supply). At this time, the switching operation mode of the power switching device needs to be adjusted to ensure that energy can be returned from the output to the input. This mode is usually used in applications such as energy recovery, battery charging and discharging.

[0054] In order to achieve bidirectional energy transfer, the power switching device needs to have bidirectional conduction capability. Usually, bidirectional MOSFET or IGBT is used, or a combination of unidirectional switching devices and diodes is used to achieve bidirectional conduction. The control strategy needs to be adjusted according to the different working modes. In the forward working mode, the control strategy focuses on how to achieve efficient energy transfer; in the reverse working mode, the control strategy needs to ensure that energy can be returned from the output to the input while maintaining high efficiency. In order to ensure efficient energy transfer in both bidirectional working modes, the parameters of the resonant capacitor and the resonant inductor need to be optimized to ensure resonance in both forward and reverse working modes.

[0055] The power supply 60 is a DC power supply. In the full-bridge LLC resonant circuit, the DC power supply is the energy source of the circuit. It provides the required DC power for the circuit. The DC power supply is usually connected to the input end of the full-bridge LLC resonant circuit and is controlled by a power switch device to achieve efficient energy conversion. The connection between the DC power supply and the full-bridge LLC resonant circuit includes: an input filter. In order to reduce the noise and fluctuation of the input power supply, an input filter is usually added between the DC power supply and the full-bridge LLC resonant circuit, such as a filter circuit composed of capacitors and inductors; a DC bus. The DC power supply is connected to the input end of the full-bridge LLC resonant circuit through the DC bus to ensure efficient transmission of electric energy; a power switch device. The electric energy of the DC power supply is controlled by a power switch device to achieve efficient 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 efficient and reliable operation of the circuit.

[0056] The full-bridge LLC circuit is also called the full-bridge LLC resonant converter (Full-Bridge LLC Resonant Converter), which is used to describe a specific circuit topology. It realizes soft switching through the resonant circuit, reduces switching losses and improves efficiency. The full-bridge LLC resonant converter mainly consists of the following parts: a full-bridge inverter, which consists of four power switching devices (usually MOSFET or IGBT) to convert DC voltage into high-frequency AC voltage; a resonant network, including a resonant inductor (Lr), a resonant capacitor (Cr) and a transformer excitation inductor (Lm), which is used to realize soft switching and voltage conversion; an output rectifier circuit, which converts high-frequency AC voltage into DC voltage, usually using a diode or a synchronous rectifier. The operating modes of the full-bridge LLC resonant converter are mainly divided into two types: resonant mode, which works near the resonant frequency to achieve zero voltage switching (ZVS) and zero current switching (ZCS) to reduce switching losses; and non-resonant mode, which works at non-resonant frequencies and may cause hard switching and increase switching losses. The key components include: resonant inductor, which together with the resonant capacitor forms a resonant circuit and determines the resonant frequency; resonant capacitor, which together with the resonant inductor forms a resonant circuit and determines the resonant frequency; excitation inductance, the excitation inductance of the transformer, affects the Q value and voltage gain of the resonant circuit; power switching devices, usually MOSFET or IGBT, need to select appropriate rated voltage and current to ensure reliability under high-frequency switching; output rectifier, usually a diode or synchronous rectifier, is used to convert high-frequency AC voltage into DC voltage.

[0057] The full-bridge CLLC circuit, also known as the full-bridge CLLC resonant converter (Full-Bridge CLLC Resonant Converter), is an improved resonant converter. It adds additional capacitors on the basis of the traditional LLC resonant converter to further optimize the circuit performance. The full-bridge CLLC resonant converter is mainly composed of the following parts: a full-bridge inverter, which consists of four power switching devices (usually MOSFET or IGBT) and is used to convert DC voltage into high-frequency AC voltage; a resonant network, including two resonant inductors (Lr1 and Lr2), two resonant capacitors (Cr1 and Cr2) and the excitation inductance (Lm) of the transformer, which are used to achieve soft switching and voltage conversion; an output rectifier circuit, which converts the high-frequency AC voltage into a DC voltage, usually using a diode or a synchronous rectifier.

[0058] The bus 20 refers to a group of wires or conductors that are used to transmit electrical energy or signals. The bus plays the role of connecting different components and devices in the circuit to ensure that electrical energy or signals can be transmitted efficiently and reliably. The types of bus include: DC bus (DC Bus), which is used to transmit DC power. In power electronic converters, the DC bus usually connects the input power supply and power switching devices; the AC bus (AC Bus) is used to transmit AC power. In inverters or frequency converters, the AC bus connects power switching devices and output loads; the signal bus (Signal Bus) is used to transmit control signals or data signals. The signal bus is usually used to connect control circuits and power switching devices, such as feedback signals. In a full-bridge LLC resonant circuit, the bus is mainly used to connect the input power supply, power switching devices, resonant capacitors, resonant inductors and transformers. Specific applications include: DC bus, connecting input power and power switching devices to ensure efficient transmission of DC power; resonant bus, connecting resonant capacitors and resonant inductors to form a resonant circuit to ensure the stability of the resonant frequency; transformer bus: connecting the primary and secondary windings of the transformer to ensure efficient energy transmission. The bus plays a key connecting role in power electronic systems to ensure efficient transmission of power or signals. In the full-bridge LLC resonant circuit, the design and selection of the bus needs to consider factors such as current capacity, voltage level, heat dissipation performance and mechanical strength to ensure efficient and reliable operation of the circuit.

[0059] The sampling module 30 is connected to the bus 20 and is used to collect 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] A first connection end of the switch module 40 is connected to the power source 60 , and a second connection end of the switch module 40 is connected to the full-bridge resonant circuit 10 .

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

[0062] A protection circuit for a full-bridge resonant circuit according to an embodiment of the present invention comprises a full-bridge resonant circuit, a bus, a sampling module, a switch module and a main control module, wherein the full-bridge resonant circuit is connected to a power supply via the bus, the sampling module is connected to the bus and is used to collect the current value of the bus, the first connection end of the switch module is connected to the power supply, and the second connection end is connected to the full-bridge resonant circuit, the main control module is respectively connected to the sampling module and the switch module and is used to obtain the current value of the bus collected by the sampling module; 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, thereby avoiding the problem of damage to the power devices on the full-bridge resonant circuit when an overcurrent occurs in the bus, thereby improving the stability and reliability of the full-bridge resonant circuit.

[0063] In an embodiment of the present invention, the main control module 50 is used to determine whether the current value of the bus 20 is greater than a preset current value. If the current value of the bus 20 is greater than the preset current value, the switch module 40 is controlled to disconnect the full-bridge resonant circuit 10 from the power supply 50.

[0064] Specifically, the full-bridge resonant circuit 10 can work in both positive and negative directions. 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 the 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 the working mode in which the voltage and current on the bus bar as a whole present a voltage phase leading the current under a certain working frequency. When the entire resonant cavity of the full-bridge resonant circuit 10 is in the inductive working area, it is ensured that the MOS tube works under zero voltage switching conditions, thereby reducing switching losses, improving efficiency, and extending device life. However, 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 zero voltage switching conditions, thereby reducing switching losses, improving efficiency, and extending device life. When the resonator cavity is not in the inductive working area but in the capacitive working area, the capacitive working area refers to the working mode in which the circuit presents an overall current phase leading the voltage at a certain working frequency. At this time, in each working cycle, a higher current spike will be generated on the two groups of MOS tubes, causing the MOS tubes to be overcurrent-breakdowned and damaged. The current spike is also far beyond the overcurrent allowed by the bus. The main control module 50 determines whether the current value of the bus 20 is greater than the preset current value, and when the current value of the bus 20 is greater than the preset current value, controls the switch module 40 to disconnect the full-bridge resonant circuit 10 from the power supply 60, thereby protecting the MOS tube from being overcurrent-breakdown when the full-bridge resonant circuit 10 enters the capacitive working area.

[0065] The capacitive working area refers to the situation that under certain working conditions, the circuit exhibits capacitive characteristics, that is, the current leads the voltage. This situation usually occurs when the switching frequency is higher than the resonant frequency. The characteristics of the capacitive working area are: the current leads the voltage. In the capacitive working area, the phase of the current leads the phase of the voltage. This means that the capacitive effect in the circuit is dominant; the stress of the switching device increases. Since the current leads the voltage, the switching device may be subjected to a large current stress when it is turned off, which may lead to increased switching losses and shortened device life; the resonant current increases. In the capacitive working area, the resonant current may increase, resulting in increased losses in the circuit; the efficiency decreases. Due to the phase relationship between current and voltage, the efficiency of the capacitive working area is usually lower than that of the inductive working area.

[0066] The capacitive working area is an operating state that needs to be avoided in the LLC resonant converter because it will lead to problems such as reduced efficiency, increased stress on switching devices, and overcurrent breakdown damage of power devices.

[0067] Reference Figure 2 , shows a schematic structural diagram of another protection circuit of a full-bridge resonant circuit according to an embodiment of the present invention, wherein 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 to the power source 60 , and the second connection end of the switch 41 is connected to the full-bridge resonant circuit 10 .

[0069] The switch 41 may be a relay, or may be a MOSFET, an IGBT (Insulated Gate Bipolar Transistor), a SIC (Silicon Carbide), a GaN (Gallium Nitride), or the like.

[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, which generates a magnetic field through current to control the switching state of the relay; contacts, which are used to connect or disconnect the circuit, usually including normally open contacts (NO), normally closed contacts (NC) and changeover contacts (COM); a magnetic core, which enhances the magnetic field generated by the coil and improves the sensitivity of the relay; and a spring, which is used to maintain the initial state of the contacts and restore the contact state after the magnetic field disappears.

[0071] The switch control circuit 42 is connected to the switch 41 and the main control module 50 respectively. The main control module 50 is used to control 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 off. The main control module 50 controls the switch 41 to be turned on or off according to the current value of the bus 20. When the current value of the bus 20 is greater than the preset current value, that is, the full-bridge resonant circuit 10 enters the capacitive working area, and the overcurrent when the MOS tube is turned on has a spike. When the current spike exceeds the overcurrent allowed by the bus, the switch control circuit 42 controls the switch 41 to be turned off, thereby disconnecting the connection between the full-bridge resonant circuit 10 and the power supply 60, protecting the MOS tube power device from being burned. 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 is working 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 present invention, 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, a first end of the fault alarm module 70 is connected to the power supply 60, and a second end of the fault alarm module 70 is connected to the full-bridge resonant circuit 10, for performing a fault alarm when the switch module 40 is disconnected.

[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. 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 issues a fault alarm.

[0076] In the embodiment of the present invention, 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 to the first resistor 72; one end of the first resistor 72 is arranged to connect the switch module 40 and the full-bridge resonant circuit 10; the first light-emitting diode 71 is used to be turned on when the full-bridge resonant circuit 10 is working in the forward direction and the switch module 40 is disconnected.

[0078] The first light-emitting diode 71 emits visible light when current passes through it. The light-emitting diode has the advantages of high efficiency, long life, and low power consumption, and is widely used in lighting, display, indication and other fields. The first light-emitting diode 71 lights up when the 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 to prevent the components in the circuit from being overloaded or damaged. The basic working principle of the current limiting resistor is to use Ohm's law to limit the current through the resistance value. By selecting a suitable resistance value, the current can be limited within a safe range.

[0080] When the full-bridge resonant circuit 10 is in the forward working state, if the full-bridge resonant circuit 10 enters the capacitive working area, then the overcurrent of the power device MOS tube in the full-bridge resonant circuit 10 when it is turned on will have a spike, and the current spike size will greatly exceed the overcurrent size allowed by the bus. At this time, the main control module 50 detects the overcurrent of the bus through the sampling module 30, and controls the switch 41 to disconnect 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 is consistent with the current flow direction of the first light-emitting diode 71. The first light-emitting diode 71 is turned on and lights up, and the first resistor 72 can limit the bus current to an extremely low level to protect the power device from being burned. The first light-emitting diode 71 in the fault alarm module 70 lights up, which means that the full-bridge resonant circuit 10 has entered the capacitive working area in the forward working state. At this time, the power device of the full-bridge resonant circuit 10 is at risk of overcurrent breakdown and damage.

[0081] The second light-emitting diode 73 is connected in series with the second resistor 74, and 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 works in reverse and the switch module 40 is disconnected, 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 life, and low power consumption, and is widely used in lighting, display, indication and other fields. The second light-emitting diode 73 lights up when the current flows 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 to prevent the components in the circuit from being overloaded or damaged. The basic working principle of the current limiting resistor is to use Ohm's law to limit the current through the resistance value. By selecting a suitable 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, then the overcurrent of the power device MOS tube in the full-bridge resonant circuit 10 when it is turned on will have a spike, and the current spike size will greatly exceed the overcurrent size allowed by the bus. At this time, the main control module 50 detects the overcurrent of the bus through the sampling module 30, and controls the switch 41 to disconnect 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 is consistent with the current flow direction of the second light-emitting diode 73. The second light-emitting diode 73 is turned on and lights up, and the second resistor 74 can limit the bus current to an extremely low level to protect the power device from being burned. The second light-emitting diode 73 in the fault alarm module 70 lights up, which means that the full-bridge resonant circuit 10 has entered the capacitive working area in the reverse working state. At this time, the power device of the full-bridge resonant circuit 10 is at risk of overcurrent breakdown and damage.

[0085] The tester can visually observe the fault alarm module 70 to determine in which working mode the full-bridge resonant circuit 10 enters the capacitive working area, thereby performing troubleshooting.

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

[0087] The main full-bridge circuit 11 is connected to the first power source 61 via the first bus 21 .

[0088] The secondary full-bridge circuit 13 is connected to the second power source 62 via 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, and 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 present invention, the main full-bridge circuit 11 includes a first switch tube 111, a second switch tube 112, a third switch tube 113 and a fourth switch tube 114. 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] A first electrode of the first switch tube 111 is connected to the positive electrode of the first power source 61 , and a second electrode of the first switch tube 111 is connected to the resonant cavity 12 .

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

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

[0094] The first electrode of the fourth switch tube 114 is disposed 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 disposed between the second electrode of the second switch tube 112 and the negative electrode of the first power source 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 through the first switch tube 111 and the fourth switch tube 114 to the negative bus pole of the first bus 21. The positive bus pole of the first bus 21 is connected to the positive pole of the first power supply 61, and the negative bus pole of the first bus 21 is connected to the negative pole of the first power supply 61.

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

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

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

[0099] One end of the resonant inductor 122 is disposed 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 to the transformer 123 .

[0100] The resonant capacitor 121 is used to store and release electric energy, and forms a resonant circuit with the resonant inductor 122. The resonant inductor 122 is used to store and release 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. The resonant cavity 12 realizes efficient energy transmission and soft switching technology through resonance.

[0101] In the embodiment of the present invention, the sub-full bridge circuit includes a fifth switch tube 131, a sixth switch tube 132, a seventh switch tube 133 and an eighth switch tube 134. The fifth switch tube 131, the sixth switch tube 132, the seventh switch tube 133 and the eighth switch tube 134 can be MOS tubes or diodes, which is not limited in the embodiment of the present invention.

[0102] A first electrode of the fifth switch tube 131 is connected to the positive electrode of the second power source 62 , and a second electrode of the fifth switch tube 131 is connected to the transformer 123 .

[0103] A first electrode of the sixth switch tube 132 is connected to a second electrode of the fifth switch tube 131 , and a second electrode of the sixth switch tube 132 is connected to a negative electrode of the second power source 62 .

[0104] The first electrode of the seventh switch tube 133 is disposed between the first electrode of the fifth switch tube 132 and the positive electrode of the second power source 62 , and the second electrode of the seventh switch tube 133 is connected to the transformer 123 .

[0105] The first electrode of the eighth switch tube 134 is disposed 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 disposed between the second electrode of the sixth switch tube 132 and the negative electrode of the second power supply 62 .

[0106] In the embodiment of the present invention, the protection circuit further includes a first filter capacitor 80 and a second filter capacitor 81 .

[0107] The main function of the filter capacitor is to remove ripple and noise in the voltage or current and provide a stable DC voltage or current. 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 electrical energy. When the voltage drops, the filter capacitor discharges and releases the stored electrical energy to smooth the voltage waveform. The filter capacitor can remove ripple in the voltage or current, making it close to pure DC, and can also reduce high-frequency noise in the voltage or current and improve signal quality.

[0108] One end of the first filter capacitor 80 is disposed between the positive electrode of the first power source 61 and the first electrode of the first switch tube 111 , and the other end is grounded.

[0109] One end of the second filter capacitor 81 is disposed between the positive electrode of the second power source 62 and the first electrode of the seventh switch tube 133 , and the other end is grounded.

[0110] In the embodiment of the present invention, one end of the sampling module 30 is connected to the first bus bar 21 .

[0111] 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 (positive direction) or the second switch tube 112, the third switch tube 113 (negative direction). The sampling module 30 can be on the main power bus, on the positive or negative bus, and can be achieved by adding a sampling resistor at the corresponding position of the bus.

[0112] 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. Specific measures include: adjusting the switching frequency. By controlling the switching frequency to be lower than or equal to the resonant frequency, entering the capacitive working area can be avoided; 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 a frequency control strategy: adopt an appropriate frequency control strategy to ensure that the circuit always operates in the inductive working area.

[0113] The tester can determine in 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.

[0114] And adjust the switching frequency and the resonance cavity parameters. When the fault is eliminated, the power is turned on again, the main control module 50 controls the switch 41 to close 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.

[0115] Specifically, the switching frequency is modified by software programming, and the magnitude of the modulation wave of the main control chip and the reference clock signal value inside the modulation main control module 50 is changed. The resonant cavity parameters include the excitation inductance, the resonant inductance, and the resonant capacitor value, and these parameters can be adjusted by replacing the device resonant capacitor 121, the resonant inductor 122, and the transformer 123.

[0116] In the embodiment of the present invention, when the bidirectional full-bridge LLC circuit enters the capacitive working area, the MOSFET is protected from overcurrent breakdown, and the experimental test personnel can quickly discover and determine that the resonant cavity enters the capacitive working area, and adjust the operating frequency and resonant cavity device parameters in time.

[0117] The embodiment of the present invention further provides a converter, which includes the protection circuit of the full-bridge resonant circuit mentioned above. It should be noted that for the method embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that the embodiments of the present invention are not limited by the described order of actions, because according to the embodiments of the present invention, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present invention.

[0118] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0119] It will be appreciated by those skilled in the art that the embodiments of the present invention may be provided as methods, devices, or computer program products. Therefore, the embodiments of the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the embodiments of the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0120] The embodiments of the present invention are described with reference to the flowcharts and / or block diagrams of the methods, terminal devices (systems), and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing terminal device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing terminal device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0121] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing terminal device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0122] These computer program instructions can also be loaded onto a computer or other programmable data processing terminal device so that a series of operating steps are executed on the computer or other programmable terminal device to produce a computer-implemented process, thereby providing instructions for executing on the computer or other programmable terminal device to implement the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0123] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0124] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0125] The protection circuit and converter of a full-bridge resonant circuit provided by the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A protection circuit for a full-bridge resonant circuit, characterized in that: The protection circuit includes: a full-bridge resonant circuit, a bus, a sampling module, a switch module, and a main control module; The full-bridge resonant circuit is connected to a power source via the bus bar; The sampling module is connected to the bus and is used to collect the current value of the bus; The first connection end of the switch module is connected to the power supply, and the second connection end is connected to the full-bridge resonant circuit; The main control module is connected to the sampling module and the switch module respectively, and is used to obtain the current value of the bus collected by the sampling module; according to the current value of the bus, the switch module is controlled to disconnect the full-bridge resonant circuit from the power supply.

2. The protection circuit according to claim 1, characterized in that: The main control module is used to determine whether the current value of the bus is greater than a preset current value. If the current value of the bus is greater than the preset current value, the switch module is controlled to disconnect the full-bridge resonant circuit from the power supply.

3. The protection circuit according to claim 1, characterized in that: The switch module includes a switch and a switch control circuit; The first connection end of the switch is connected to the power supply, and the second connection end is connected to the full-bridge resonant circuit; The switch control circuit is connected to the switch and the main control module respectively, and the main control module is used to control the working state of the switch through the switch control circuit.

4. The protection circuit according to claim 1, characterized in that: The protection circuit also includes a fault alarm module; The fault alarm module is connected in parallel with the switch module, a first end of the fault alarm module is connected to the power supply, and a second end of the fault alarm module is connected to the full-bridge resonant circuit, and is used for performing a fault alarm when the switch module is disconnected.

5. The protection circuit according to claim 4, characterized in that: The fault alarm module includes 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 switch module, and the other end is connected to 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 to be turned on when the full-bridge resonant circuit is working in the forward direction and the switch module is disconnected; The second light-emitting diode is connected in series with the second resistor, and the second light-emitting diode and the second resistor are connected in parallel with the first light-emitting diode and the first resistor; the second light-emitting diode is used to be turned on when the full-bridge resonant circuit works in reverse and the switch module is disconnected.

6. The protection circuit according to claim 1, characterized in that: The full-bridge resonant circuit comprises a primary 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 busbar comprises a first busbar and a second busbar; The main full-bridge circuit is connected to the first power supply through the first bus; The secondary full-bridge circuit is connected to the second power supply through the second bus.

7. The protection circuit according to claim 6, characterized in that: The main full-bridge circuit includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; The first electrode of the first switch tube is connected to the positive electrode of the first power supply, and the second electrode of the first switch tube is connected to the resonant cavity; The first electrode of the second switch tube is connected to the second electrode of the first switch tube, and the second electrode of the second switch tube is connected to the negative electrode of the first power supply through the bus bar; 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 to the resonant cavity; 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.

8. The protection circuit according to claim 7, characterized in that: The resonant cavity includes a resonant capacitor, a resonant inductor and a transformer; One side of the transformer is connected to the primary full-bridge circuit via the resonant capacitor and the resonant inductor, and the other side of the transformer is connected to the secondary full-bridge circuit; One end of the resonant capacitor is connected to the second electrode of the first switch tube, and the other end of the resonant capacitor is connected to the transformer; One end of the resonant inductor is disposed 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 to the transformer.

9. The protection circuit according to claim 8, characterized in that: The secondary full-bridge circuit includes a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube; A first electrode of the fifth switch tube is connected to the positive electrode of the second power supply, and a second electrode of the fifth switch tube is connected to the transformer; The first electrode of the sixth switch tube is connected to the second electrode of the fifth switch tube, and the second electrode of the sixth switch tube is connected to the negative electrode of the second power supply; 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 to the transformer; 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.

10. The protection circuit according to claim 9, characterized in that: The protection circuit also includes 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 tube, and the other end is grounded; One end of the second filter capacitor is disposed between the positive electrode of the second power supply and the first electrode of the seventh switch tube, and the other end is grounded.

11. The protection circuit according to claim 6, characterized in that: One end of the sampling module is connected to the first bus bar.

12. A converter, characterized in that: A protection circuit comprising a full-bridge resonant circuit as claimed in any one of claims 1 to 11.

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