CN115411921A - Converter and inverter - Google Patents

Converter and inverter Download PDF

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Publication number
CN115411921A
CN115411921A CN202211058310.XA CN202211058310A CN115411921A CN 115411921 A CN115411921 A CN 115411921A CN 202211058310 A CN202211058310 A CN 202211058310A CN 115411921 A CN115411921 A CN 115411921A
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CN
China
Prior art keywords
unit
charging
capacitor
converter
diode
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Pending
Application number
CN202211058310.XA
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Chinese (zh)
Inventor
占金祥
张芳坡
林天散
徐炜基
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Huawei Digital Power Technologies Co Ltd
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Huawei Digital Power Technologies Co Ltd
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Priority to CN202211058310.XA priority Critical patent/CN115411921A/en
Publication of CN115411921A publication Critical patent/CN115411921A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/01—Resonant DC/DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The application provides a converter and an inverter. The converter comprises a control unit, a power conversion unit, a series resonance unit, a pre-charging unit and a rectifying and filtering unit; the input end of the power conversion unit is used as the input end of the converter and is connected with a power supply; the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filter unit is used as the output end of the converter; the pre-charging unit is connected between the positive output end of the power supply and the output end of the power conversion unit in parallel; the control unit is used for controlling the pre-charging unit to charge the resonance capacitor in the series resonance unit and the filter capacitor in the rectifying and filtering unit based on the electric energy provided by the power supply; the control unit is also used for controlling the pre-charging unit to be disconnected when the voltage of the resonance capacitor and the voltage of the filter capacitor reach the target voltage, and controlling the power conversion unit to work. The application can reduce the risk of overcurrent/overvoltage damage of circuit elements and improve the safety and stability of the circuit.

Description

Converter and inverter
Technical Field
The application relates to the technical field of power electronics, in particular to a converter and an inverter.
Background
A resonant Direct Current (DC)/DC conversion circuit is a special DC conversion circuit, and the output voltage and the input voltage of the circuit have a fixed transformation ratio. The resonance DC/DC conversion circuit can realize the soft switching of the switching tube in the circuit by utilizing resonance, reduce the switching loss of the switching tube and improve the working efficiency of the circuit. The resonant DC/DC conversion circuit includes a two-level resonant DC/DC conversion circuit and a multi-level resonant DC/DC conversion circuit. At present, the two-level resonance DC/DC conversion circuit is widely applied, and compared with the two-level resonance DC/DC conversion circuit, the multi-level resonance DC/DC conversion circuit can realize higher-level voltage output by using devices with smaller voltage withstanding level, so that the multi-level resonance DC/DC conversion circuit also has better application prospect. However, when the resonant DC/DC conversion circuit starts operating, the peak value of the current flowing through the circuit elements such as the switching tube and the capacitor in the circuit may be very high, which may cause the circuit elements to be damaged by overcurrent or overvoltage, resulting in a decrease in the safety of the circuit.
Disclosure of Invention
The application provides a converter and an inverter, which can reduce the risk of overcurrent/overvoltage damage of circuit elements and improve the safety and stability of a circuit.
In a first aspect, the present application provides a converter, which may include a control unit, a power conversion unit, a series resonance unit, a pre-charge unit, and a rectification filter unit; the input end of the power conversion unit is used as the input end of the converter and is connected with the power supply, and the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; here, the power conversion unit may be a DC/DC conversion circuit, and in a photovoltaic power supply scenario, the power supply may be a photovoltaic module or an energy storage battery. The series resonance unit may include a resonance capacitor and a resonance inductor connected in series, and the rectifying and filtering unit includes a filtering capacitor. The output end of the rectification filter unit is used as the output end of the converter; the pre-charging unit is connected between the positive output end of the power supply and the output end of the power conversion unit in parallel; the control unit can be used for controlling the pre-charging unit to charge a resonance capacitor in the series resonance unit and a filter capacitor in the rectification filter unit based on electric energy provided by the power supply; the control unit can also be used for controlling the pre-charging unit to be disconnected when the voltage of the resonance capacitor and the voltage of the filter capacitor reach the target voltage, and controlling the power conversion unit to work.
In this application, through increasing simple circuit element, combine multiplexing of components such as the switch tube in the converter to constitute resonant capacitor and filter capacitor's charge circuit, accomplish the precharge to resonant capacitor and filter capacitor, can be at the converter during operation, reduce the pressure differential between the input voltage of power and resonant capacitor's the voltage, and reduce the pressure differential between resonant capacitor's the voltage and the output voltage of converter, make difficult production peak value higher electric current in the circuit, reduce components such as the switch tube in the converter because of the risk of excessive pressure/overcurrent damage in the moment of switching on, improve circuit stability and security, circuit structure is simple, circuit cost is low, and the suitability is strong.
In a possible implementation manner, the rectification filter unit comprises a filter capacitor, a first diode and a second diode, the output end of the converter comprises a first output end and a second output end, the first diode and the second diode are connected in series and then connected in parallel between the first output end and the second output end of the converter with the filter capacitor, and the series connection point of the first diode and the second diode serves as the input end of the rectification filter unit; the power conversion unit comprises a first switching tube and a second switching tube, the first switching tube and the second switching tube are connected in series and then connected in parallel to two ends of a power supply, and the series connection point of the first switching tube and the second switching tube is used as the output end of the power conversion unit; the pre-charging unit is connected in parallel with two ends of the first switch tube. At the moment, the circuit topology of the power conversion unit in the converter is a two-level topology, in the application, the control unit in the converter charges the resonant capacitor and the filter capacitor to the target voltage by controlling the pre-charging unit, and the possibility that elements such as a switching tube and the like in the circuit are damaged due to overvoltage/overcurrent at the moment of conduction can be reduced when the circuit starts to work, so that the safety and the stability of the circuit are improved.
In one possible implementation manner, the pre-charging unit comprises a charging switch and a current limiting unit, and the charging switch and the current limiting unit are connected in series and then connected in parallel with the first switching tube; the charging switch may be a controllable switch, a relay, a dc contactor, an IGBT or a MOSFET, and the current limiting unit may include a resistor or an inductor. The control unit is used for controlling the charging switch to be closed when the voltage of the resonant capacitor does not reach the target voltage, so that the power supply charges the resonant capacitor through a loop formed by the charging switch, the current limiting unit, the series resonant unit and the first diode. In this application, the converter is through increasing simple circuit element such as switch, resistance, and the electric energy that the power that connects based on the converter provides comes to precharge for resonant capacitor, can be when the power conversion unit in the converter begins work, reduces the possibility that components such as switch tube in the circuit are because of overcurrent/excessive pressure damage in the switch-on moment, improves the security and the stability of circuit, simple structure, and circuit cost is low, and the suitability is strong.
In a possible implementation manner, the control unit is further configured to control the charging switch to be turned off and the second switching tube to be turned on under the condition that the voltage of the filter capacitor does not reach a target voltage, the charging switch is turned on, and the voltage of the resonant capacitor reaches a preset voltage, so that the resonant capacitor charges the filter capacitor through a loop formed by the resonant inductor, the second switching tube, the filter capacitor and the second diode in the series resonant unit, wherein the preset voltage is less than or equal to the target voltage; the control unit is further used for controlling the second switching tube to be switched off when the voltage of the filter capacitor reaches the target voltage so as to finish charging the filter capacitor.
In the application, a filter capacitor charging loop is formed by devices such as a switch tube in a multiplexing circuit, the filter capacitor is charged by utilizing a resonance capacitor, the circuit structure is simple, the circuit cost is low, the control logic of the pre-charging process is simple, and the possibility that elements such as the switch tube in the circuit are damaged due to overcurrent/overvoltage at the moment of conduction can be reduced when a power conversion unit in a converter starts to work, so that the safety and the stability of the circuit are improved.
In a possible implementation manner, the rectification filter unit comprises a filter capacitor, a first diode and a second diode, the output end of the converter comprises a first output end and a second output end, the first diode and the second diode are connected in series and then connected in parallel between the first output end and the second output end of the converter with the filter capacitor, and the series connection point of the first diode and the second diode is used as the input end of the rectification filter unit; the power conversion unit comprises a third switching tube, a fourth switching tube, a fifth switching tube, a sixth switching tube, a first capacitor, a second capacitor, a third diode and a fourth diode which are connected in series; the first capacitor and the second capacitor are connected in series, and are connected with the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube which are connected in series in parallel at two ends of a power supply; the serial connection point of the fourth switching tube and the fifth switching tube is used as the output end of the power conversion unit; the circuit topology of the power conversion unit in the converter is now an NPC type three-level topology. The pre-charging unit can be connected in parallel with the two ends of the third switching tube and the fourth switching tube which are connected in series; alternatively, the pre-charging unit may be connected in parallel to both ends of the third switching tube.
In the application, simple circuit elements such as a switch and a resistor are added to serve as a pre-charging unit, the pre-charging unit is controlled to pre-charge a resonant capacitor and a filter in the three-level resonant direct-current converter based on electric energy provided by a power supply, the structure is simple, the circuit cost is low, when a power conversion unit in the converter starts to work, the possibility that elements such as a switch tube in the circuit are damaged due to overcurrent/overvoltage at the moment of conduction is reduced, and the safety and the stability of the circuit are improved.
In a possible implementation manner, the pre-charging unit comprises a charging switch and a current limiting unit, and the charging switch and the current limiting unit are connected in series and then connected in parallel with a third switching tube and a fourth switching tube which are connected in series; at this time, the withstand voltage value of the charge switch may be equal to the input voltage of the power supply. The control unit is used for controlling the charging switch to be closed when the voltage of the resonant capacitor does not reach the target voltage, so that the power supply charges the resonant capacitor through a loop formed by the charging switch, the current limiting unit, the series resonant unit and the first diode. In this application, through increasing simple circuit element such as switch, resistance, come to precharge for the resonant capacitor among the three-level resonance direct current converter based on the electric energy that the power provided, can improve the security and the stability of circuit, simple structure, the circuit is with low costs, and the suitability is strong.
In one possible implementation manner, the pre-charging unit comprises a charging switch and a current limiting unit, and the charging switch and the current limiting unit are connected in series and then connected in parallel with the third switching tube; in this case, the withstand voltage of the charge switch can be reduced to half the input voltage of the power supply. The control unit is used for controlling the charging switch to be closed and the fourth switch tube to be conducted when the voltage of the resonant capacitor does not reach the target voltage, so that the power supply charges the resonant capacitor through a loop formed by the charging switch, the current limiting unit, the fourth switch tube, the series resonant unit and the first diode. In the application, a switch with a smaller voltage-withstanding grade can be selected to form a pre-charging loop of a resonant capacitor in the three-level resonant direct-current converter, so that the device parameter requirements on elements are reduced, and the circuit cost is low.
In a possible implementation manner, the control unit is further configured to control the charging switch to be turned off, the fifth switching tube and the sixth switching tube to be turned on under the condition that the voltage of the filter capacitor does not reach the target voltage, the charging switch is turned on, and the voltage of the resonant capacitor reaches a preset voltage, so that the resonant capacitor charges the filter capacitor through a loop formed by the resonant inductor, the fifth switching tube, the sixth switching tube, the filter capacitor and the second diode in the series resonant unit, wherein the preset voltage is less than or equal to the target voltage; the control unit is further used for controlling the fifth switching tube and the sixth switching tube to be turned off when the voltage of the filter capacitor reaches the target voltage so as to finish charging the filter capacitor.
In the application, the filter capacitor charging loop is formed by devices such as a switch tube in the multiplexing circuit, the resonant capacitor is used for charging the filter capacitor, the structure is simple, the circuit cost is low, the control logic of the pre-charging process is simple, the applicability is strong, and when a power conversion unit in a converter starts to work, the possibility that elements such as the switch tube in the circuit are damaged due to overcurrent/overvoltage at the moment of conduction is reduced, and the safety and the stability of the circuit are improved.
In a possible implementation manner, the control unit is further configured to control the charging switch to be turned off when the voltage of the filter capacitor and the voltage of the resonance capacitor reach the target voltage, so as to control the pre-charging unit to be turned off.
In this application, through increasing simple circuit element, the switch tube among the multiplexing circuit utilizes the power to charge to target voltage for resonance capacitor to utilize resonance capacitor to charge to target voltage for filter capacitor, can realize the precharge that charges resonance capacitor and filter capacitor in this converter, reduce components such as switch tube in the circuit and be in the possibility of switching on in the twinkling of an eye because of overcurrent/excessive pressure damage, improve circuit's security and stability, circuit structure is simple, the circuit is with low costs.
In a second aspect, the present application provides a converter, which includes a control unit, a power conversion unit, a series resonance unit, a first pre-charge unit, a second pre-charge unit, and a rectification filter unit; the input end of the power conversion unit is used as the input end of the converter and is connected with the power supply, and the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filter unit is used as the output end of the converter;
the first pre-charging unit is connected in parallel with two ends of a resonance capacitor in the series resonance unit, and the second pre-charging unit is connected in parallel with two ends of a filter capacitor in the rectifying and filtering unit;
the control unit is used for controlling the first pre-charging unit to charge the resonance capacitor and controlling the second pre-charging unit to charge the filter capacitor; the control unit is also used for controlling the first pre-charging unit to be disconnected when the voltage of the resonance capacitor reaches the target voltage, controlling the second pre-charging unit to be disconnected when the voltage of the filter capacitor reaches the target voltage, and controlling the power conversion unit to work.
In a possible implementation manner, the first pre-charging unit includes a first transformer, a first switching tube and a first rectifying diode, a primary side of the first transformer is connected to the power supply through the first switching tube, and a secondary side of the first transformer is connected in parallel to two ends of the resonant capacitor through the first rectifying diode; the second pre-charging unit comprises a second transformer, a second switching tube and a second rectifier diode, wherein the primary side of the second transformer is connected with the power supply through the second switching tube, and the secondary side of the second transformer is connected in parallel to two ends of the filter capacitor through the second rectifier diode.
According to the power conversion circuit, the converter utilizes the first pre-charging unit and the second pre-charging unit to respectively charge the resonant capacitor and the filter capacitor in the converter, the two charging loops are not affected with each other, the voltage of the resonant capacitor and the voltage of the filter capacitor can reach a target voltage as soon as possible, the charging mode is simple and feasible, when the power conversion unit starts to work, the possibility that a switch tube in the converter is damaged due to overvoltage/overcurrent at the moment of conduction can be reduced, and the safety and the stability of the circuit are improved.
In a third aspect, the present application provides a converter, which includes a control unit, a power conversion unit, a series resonance unit, a pre-charge unit, and a rectification filter unit; the input end of the power conversion unit is used as the input end of the converter and is connected with a power supply; the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filter unit is used as the output end of the converter; the pre-charging unit is connected in parallel with two ends of the resonance capacitor in the series resonance unit;
the rectifying and filtering unit comprises a filter capacitor, a first diode and a second diode, the output end of the converter comprises a first output end and a second output end, the first diode and the second diode are connected in series and then are connected in parallel with the filter capacitor at the first output end and the second output end of the converter, and the series connection point of the first diode and the second diode is used as the input end of the rectifying and filtering unit;
the control unit is used for controlling the conduction of a switch tube connected between the output end of the power conversion unit and the filter capacitor in the power conversion unit so as to control the pre-charging unit to charge the resonance capacitor and the filter capacitor; the control unit is also used for controlling the pre-charging unit to be disconnected, controlling the switch tubes between the output end of the power conversion unit and the filter capacitor to be switched off and controlling the power conversion unit to work when the voltages of the resonant capacitor and the filter capacitor reach the target voltage.
In a possible implementation manner, the pre-charging unit includes a transformer, a first switching tube, and a rectifying diode, a primary side of the transformer is connected to the power supply through the first switching tube, and a secondary side of the transformer is connected in parallel to two ends of the resonant capacitor through the rectifying diode.
In the application, the converter utilizes a pre-charging unit to realize the common charging of the resonant capacitor and the filter capacitor, the possibility of damage of a switch tube in the converter due to overvoltage/overcurrent can be reduced when the power conversion unit starts to work, the safety and the stability of a circuit are improved, and the circuit is simple in structure, low in cost and high in charging speed.
In a fourth aspect, the present application provides an inverter, including an inverting unit and a converter provided in the first, second, or third aspect and any one of the possible implementations of the first, second, or third aspect, where the converter is connected to a load through the inverting unit; the inverter unit is used for converting the direct current output by the converter into alternating current to supply power to a load.
In the application, the converter in the inverter can reduce the risk of circuit elements being damaged due to overcurrent/overvoltage when the converter starts working by pre-charging the resonant capacitor and the filter capacitor in the converter, so that the safety and the stability of the converter are improved, and the safety and the grid connection reliability of the inverter are further improved.
Drawings
Fig. 1 is a schematic structural diagram of an inverter provided in an embodiment of the present application;
FIG. 2 is a schematic diagram of a converter according to an embodiment of the present application;
FIG. 3 is a schematic diagram of another structure of a converter provided in an embodiment of the present application;
FIG. 4 is a graph of drive timing and resonant current waveforms for the converter of FIG. 3;
FIG. 5 is a schematic diagram of another structure of a transducer provided in an embodiment of the present application;
FIG. 6 is a schematic diagram of another structure of a transducer provided in an embodiment of the present application;
FIG. 7 is a graph of drive timing and resonant current waveforms for the converter shown in FIG. 5 or FIG. 6;
FIG. 8 is a schematic diagram of another structure of a transducer provided in an embodiment of the present application;
FIG. 9 is a schematic diagram of another structure of a transducer provided in an embodiment of the present application;
FIG. 10 is a schematic diagram of another structure of a converter provided in the embodiments of the present application;
FIG. 11 is a schematic diagram of another structure of a transducer provided in an embodiment of the present application;
fig. 12 is a schematic diagram of another structure of a converter provided in the embodiment of the present application.
Detailed Description
A dc converter is a common switching power supply device in the field of power electronics, and its main function is to convert dc power into another dc power with controllable voltage or current for output, so as to meet the load requirement. For example, a dc converter may raise the voltage of a dc power supply from tens or tens of volts to hundreds of volts, or down to a few volts. The resonant DC/DC conversion circuit is a DC converter with a special circuit structure, and can realize the soft switching of a switching tube in the circuit by utilizing resonance, reduce the switching loss of the switching tube and improve the working efficiency of the circuit. The circuit topology of the resonant DC/DC conversion circuit includes a two-level topology, a multi-level topology, and the like. The resonant DC/DC conversion circuit adopting the multilevel topology can realize medium-voltage high-power output, and the voltage stress of power devices such as a switching tube and the like is small, so that the resonant DC/DC conversion circuit can be applied to various scenes as the two-level resonant DC/DC conversion circuit. Before the two-level resonant DC/DC conversion circuit and the multi-level topological resonant DC/DC conversion circuit start to work, the resonant capacitor in the circuit and the filter capacitor at the output end need to be pre-charged, so that overvoltage/overcurrent damage of elements such as a switching tube in the circuit is ensured not to easily occur at the moment of conduction, and the safety of the circuit is improved. The utility model provides a converter, the accessible increases simple circuit element, the multiplexing of components such as switch tube in the combination converter constitutes resonant capacitor and filter capacitor's charge circuit, accomplish the precharge to resonant capacitor and filter capacitor, reduce components such as switch tube in the circuit when the circuit begins working and be because of the possibility of overvoltage/overcurrent damage in the moment of switching on, improve circuit stability and security, circuit structure is simple, the circuit is with low costs, the suitability is strong.
The converter provided by the application can be suitable for various types of power equipment such as inverters, energy storage systems and wind-power converters, and can be used for different application scenes such as photovoltaic power supply scenes, light-storage hybrid power supply scenes, energy storage power supply scenes and the like. For convenience of description, the inverter applied to the photovoltaic power supply scene is taken as an example for the description in the application. Specifically, the converter may be a power conversion module for performing dc/dc conversion in the inverter, that is, the converter provided in the present application may be a functional module in the inverter. The present application also provides an inverter, which may be composed of a converter, an inverter unit, and the like, as shown in fig. 1. The converter is connected with a load through an inverter unit, the converter is used for converting direct current provided by a power supply (in the scene, the converter can refer to a photovoltaic module) into direct current and then outputting the direct current, and the inverter unit is used for converting the direct current output by the converter into alternating current to supply power to the load (such as various household devices connected with a public power grid). The converter in the inverter can reduce the risk of damage of circuit elements due to overcurrent/overvoltage when the converter starts to work by pre-charging the resonant capacitor and the filter capacitor in the converter, and improve the safety and the stability of the converter, thereby improving the safety and the grid connection reliability of the inverter.
The converter provided by the present application will be exemplified with reference to fig. 2 to 12.
Referring to fig. 2, fig. 2 is a schematic structural diagram of a converter according to an embodiment of the present disclosure. As shown in fig. 2, the converter provided by the present application may include a control unit, a power conversion unit, a series resonance unit, a pre-charge unit, and a rectification filter unit. The input end of the power conversion unit is used as the input end of the converter and is connected with a power supply. Here, the power conversion unit may be a DC/DC conversion circuit for converting a direct current provided by a power supply into another direct current of a fixed voltage or an adjustable voltage, and the power supply may be a solar cell panel, a photovoltaic module, an energy storage battery, or the like. The output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit. The series resonance unit may include a resonance capacitor and a resonance inductor connected in series, and the rectifying and filtering unit includes a filtering capacitor. And the output end of the rectification filtering unit is used as the output end of the converter. In a photovoltaic power supply scene, the output end of the converter can be connected with a load through an inversion unit in the inverter. As shown in fig. 2, in the embodiment of the present application, the pre-charging unit may be connected in parallel between the positive output terminal of the power supply and the output terminal of the power conversion unit, and the pre-charging unit may charge the resonant capacitor in the series resonant unit and the filter capacitor in the rectifying and filtering unit based on the control of the control unit, so as to reduce the risk of damage to the power switch device in the circuit due to overvoltage/overcurrent at the moment of conducting when the power conversion unit starts to operate, and improve the stability and safety of the circuit.
In some possible embodiments, the control unit in the converter may be coupled to the power conversion unit, the series resonant unit, the pre-charging unit, and the rectifying and filtering unit in the converter respectively. The control unit can be used for controlling the pre-charging unit to charge the resonance capacitor and the filter capacitor based on the electric energy provided by the power supply. The control unit can also be used as a functional module which is used for providing a driving signal for the power conversion unit in the converter so as to trigger a driving circuit of the power conversion unit to control the power conversion unit to work. Therefore, in the embodiment of the present application, the control unit may be further configured to control the pre-charging unit to be turned off and control the power conversion unit to operate when the voltage of the resonant capacitor and the voltage of the filter capacitor reach the target voltage. The target voltage can be obtained according to the input voltage of the power supply, the device parameters of the resonance capacitor and/or the filter capacitor. Specifically, the target voltage may be a voltage value close to the input voltage of the power supply. The target voltage to be achieved by the resonance capacitor and the filter capacitor can be equal voltage values; or may be different voltage values associated with respective device parameters. That is, the target voltage may include a first voltage threshold and a second voltage threshold, which are voltage values to which the resonant capacitor and the filter capacitor need to be charged respectively. The first voltage threshold and the second voltage threshold may be the same or different, and may be specifically determined according to device parameters in an application scenario, which is not limited in this application.
In some possible embodiments, the rectifying and filtering unit in the converter may include the filter capacitor and the first and second diodes. The output of the converter includes a first output and a second output. As shown in fig. 2, the output terminals of the converter include a positive terminal Vout and a negative terminal Vout, which can be respectively used as the first output terminal and the second output terminal of the converter. In the above rectifying and filtering unit, the two diodes, i.e., the first diode and the second diode, are connected in series and then connected in parallel with the filter capacitor at the output end of the converter, i.e., connected in parallel between the first output end and the second output end of the converter. The series connection point of the first diode and the second diode can be used as the input end of the rectifying and filtering unit. That is, the output terminal of the power conversion unit in the converter is connected to the series connection point of the first diode and the second diode via the series resonance unit.
Alternatively, in some possible embodiments, the circuit topology of the power conversion unit may be a two-level topology. The power conversion unit may include a first switching tube and a second switching tube, and may further include a supporting capacitor. Referring to fig. 3, fig. 3 is another schematic structural diagram of a converter according to an embodiment of the present disclosure. As shown in fig. 3, the power conversion unit includes switching tubes T1 and T2 and a capacitor C1, i.e., the first switching tube, the second switching tube and the supporting capacitor can be represented by T1, T2 and C1 in fig. 3, respectively. The second connection end of the switch tube T1 and the first connection end of the switch tube T2 are connected in series and then connected with the capacitor C1 in parallel at two ends of the power supply, the first connection end of the switch tube T1 and the second connection end of the switch tube T2 are respectively used as a first input end and a second input end of the power conversion unit, and the series connection point of the switch tube T1 and the switch tube T2 is used as an output end of the power conversion unit; the pre-charging unit is connected in parallel to two ends of the switching tube T1. It can be understood that when the switch type of the switch transistors T1 and T2 is an Insulated Gate Bipolar Transistor (IGBT), the first connection terminal may refer to a collector of the switch transistor, and the second connection terminal may refer to an emitter of the switch transistor. At this time, the first input terminal of the power conversion unit is connected to the positive output terminal of the power supply, and the second input terminal of the power conversion unit is connected to the negative output terminal of the power supply. Optionally, the switch type of the switch tubes T1 and T2 may also be a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or the like, which is not limited in this application. Before the converter starts to work normally, the control unit in the converter controls the pre-charging unit to charge the resonant capacitor and the filter capacitor in the converter to a target voltage, so that when the converter works, the voltage difference between the input voltage of a power supply and the voltage of the resonant capacitor is reduced, the voltage difference between the voltage of the resonant capacitor and the output voltage of the converter is reduced, current with a high peak value is not easy to generate in a circuit, the risk of overvoltage/overcurrent damage of elements such as a switching tube in the converter at the moment of conduction is reduced, and the safety and the stability of the circuit are improved. When the converter starts to work normally, the switch tubes T1 and T2 are conducted alternately, and when the switch tube T1 is conducted, the power supply can charge a resonant capacitor in a series resonance unit in the converter through the capacitor C1; when the switch tube T2 is turned on, the resonant capacitor can transfer energy to a filter capacitor in a rectifying and filtering unit in the converter. The driving time sequence and the resonant current waveform of the converter are shown in fig. 4, if the dead time is not considered, the driving duty ratios of the switching tubes T1 and T2 are both 0.5, the switching frequency of the converter is set to be less than the LC resonant frequency, the resonant current can be reduced to 0 before the switching tubes T1 and T2 act, zero-current switching of the switching tubes is realized, the switching loss is reduced, and the working efficiency of the circuit is improved.
In some possible embodiments, when the circuit topology of the power conversion unit is a two-level topology, the pre-charging unit in the converter may be composed of a charging switch and a current limiting unit. The charging switch and the current limiting unit can be connected in parallel with the switching tube T1 in fig. 3 after being connected in series. The charging switch can be a controllable switch, a relay, a direct current contactor, an IGBT or an MOSFET and the like, and can be determined according to actual application scenes. The current limiting unit may include a resistor or an inductor, and the current limiting unit is exemplified as the resistor R in fig. 3 in the embodiment of the present application. The charge switch may be represented by switch K in fig. 3. The filter capacitor, the first diode and the second diode included in the rectifying and filtering unit are respectively C, D0 and D0' in fig. 3. In this embodiment, the process of charging the resonant capacitor by the control unit in the converter through the pre-charging unit includes: the control unit controls the switch K in the control unit 3 to be closed, so that the power supply charges the resonant capacitor through a loop formed by the closed switch K, the current limiting unit, the resonant inductor in the resonant unit, the resonant capacitor and the first diode. In other words, as shown in fig. 3, when the switch K is closed, the current path when the power supply charges the resonant capacitor Cr is: vin positive terminal-K-R-Lr-Cr-D0-Vin negative terminal. In the embodiment, the converter is provided with simple circuit elements such as a switch and a resistor, the resonant capacitor is precharged based on the electric energy provided by the power supply connected with the converter, when the power conversion unit in the converter starts to work, the possibility that elements such as a switch tube in the circuit are damaged due to overcurrent/overvoltage at the moment of conduction is reduced, the safety and the stability of the circuit are improved, the structure is simple, the circuit cost is low, and the applicability is strong.
Further, in some possible embodiments, the control unit in the converter may also control the resonant capacitor in the converter to charge the filter capacitor. Specifically, under the condition that the voltage of the filter capacitor does not reach the target voltage and the charging switch is closed, if the voltage of the resonant capacitor reaches the preset voltage, the resonant capacitor is controlled to charge the filter capacitor. That is to say, under the condition that the voltage of the filter capacitor does not reach the target voltage, the charging switch is closed, and the voltage of the resonant capacitor reaches a preset voltage, the resonant capacitor is controlled to charge the filter capacitor. The preset voltage may be a voltage value smaller than or equal to the target voltage, and may be specifically set according to an actual scene, which is not limited in the present application. The process of charging the filter capacitor by the resonance capacitor comprises the following steps: the control unit controls the switch K to be switched off and controls the switch tube T2 in the control unit 3 to be switched on, so that the resonant capacitor charges the filter capacitor through a loop formed by the resonant inductor, the switch tube T2, the filter capacitor and the second diode. In other words, as shown in fig. 3, when the switch K is turned off and the switch T2 is turned on, the current path when the resonant capacitor Cr charges the filter capacitor C is: cr-Lr-T2-C-D0' -Cr. When the voltage at the two ends of the filter capacitor reaches the target voltage, the control unit can also control the switch tube T2 to be switched off so as to finish charging the filter capacitor. In the embodiment, the converter firstly charges the resonant capacitor, and then forms a filter capacitor charging loop through devices such as a switching tube in the multiplexing circuit, so that the resonant capacitor is utilized to charge the filter capacitor, the energy of the resonant capacitor is transferred to the filter capacitor, and the pre-charging of the filter capacitor is completed.
In some possible embodiments, such as the converter shown in fig. 3, the process of charging the resonant capacitor and the filter capacitor may include multiple rounds of charging. Understandably, the control unit in the converter controls the pre-charging unit to firstly charge the resonant capacitor based on the electric energy provided by the power supply, so that the voltage of the resonant capacitor is increased. When the voltage of the resonance capacitor rises to the preset voltage value, the charging process of the resonance capacitor is suspended, and the filter capacitor is charged. At this time, the voltage of the filter capacitor rises and the voltage of the resonance capacitor falls. When the voltage of the resonant capacitor drops to a lower voltage value, the resonant capacitor stops charging the filter capacitor, and at this time, the voltage of the filter capacitor may not reach the target voltage, and the voltage of the resonant capacitor does not reach the target voltage. That is, the voltages of the resonance capacitor and the filter capacitor may not reach the above-mentioned target voltages through this round of charging. Therefore, the charging process can be repeated until the voltages of the resonant capacitor and the filter capacitor reach the target voltage. In the last round of charging process, when the voltage of the filter capacitor reaches the target voltage, the control unit may control the second switching tube (i.e., the switching tube T2 in fig. 3) to turn off, so as to end the charging of the filter capacitor; when the voltage of the filter capacitor reaches the target voltage and the voltage of the resonance capacitor also reaches the target voltage, the control unit can control the charging switch to be switched off so as to control the pre-charging unit to be switched off and finish charging the resonance capacitor. It can be understood that, in the above-mentioned multi-round charging process, the values of the preset voltages corresponding to each round of charging may be equal or different, and the application is not limited. In the embodiment, the resonant capacitor and the filter capacitor in the two-level resonant direct-current converter can be charged by adding simple circuit elements and a switching tube in the multiplexing circuit, the converter has the advantages of simple structure, low circuit cost and high applicability, and when a power conversion unit in the converter starts to work, the possibility of damage of elements such as the switching tube in the circuit due to overcurrent/overvoltage at the moment of conduction can be reduced, and the safety and the stability of the circuit can be improved.
Alternatively, in some possible embodiments, the circuit topology of the power conversion unit in the converter may be a three-level topology. Referring to fig. 5 and 6, fig. 5 and 6 are schematic structural diagrams of a converter according to an embodiment of the present application. As shown in fig. 5 or fig. 6, the circuit topology of the power conversion unit may be a Neutral Point Clamped (NPC) type three-level topology, and then the power conversion unit may include a third switching tube, a fourth switching tube, a fifth switching tube, a sixth switching tube, a first capacitor, a second capacitor, a third diode, and a fourth diode. These circuit elements may be represented in fig. 5 or fig. 6 by switching tubes T3, T4, T5, T6, capacitors C2, C3 and diodes D1, D2, respectively. The capacitor C2 and the capacitor C3 are connected in series and then connected with the switch tube T3, the switch tube T4, the switch tube T5 and the switch tube T6 which are sequentially connected in series in parallel at two ends of a power supply, the diode D1 and the diode D2 are connected in series and then connected in parallel with the switch tube T4 and the switch tube T5 which are connected in series, and the series connection point of the diode D1 and the diode D2 is connected with the series connection point of the capacitor C2 and the capacitor C3; a first connecting end of the switch tube T3 and a second connecting end of the switch tube T6 are respectively used as a first input end and a second input end of the power conversion unit, and a series connecting point of the switch tube T4 and the switch tube T5 is used as an output end of the power conversion unit; it can be understood that the switching types of the switching tubes T3, T4, T5, and T6 can be IGBTs, so that the first connection end of each switching tube refers to the collector of the IGBT, and the second connection end of each switching tube refers to the emitter of the IGBT. The first input end and the second input end of the power conversion unit can be respectively connected with the positive output end and the negative output end of the power supply. Optionally, the switching types of the four switching tubes may also be MOSFETs, etc., which is not limited in this application. Optionally, the diodes D1 and D2 included in the power conversion unit may also be replaced with other types of switching devices, for example, both diodes may be replaced with IGBTs or the like, which is not limited in this application.
In the converter shown in fig. 5 or 6, the filter capacitor, the first diode and the second diode included in the rectifying and filtering unit are C, D0 and D0' in fig. 5 or 6, respectively. The coupling mode of the pre-charging unit and the power conversion unit comprises the following steps: two ends of the pre-charging unit are respectively connected with the first connecting end of the switch tube T3 and the second connecting end of the switch tube T4; alternatively, the pre-charging unit is connected in parallel to two ends of the switching tube T3. The pre-charging unit may be composed of a charging switch and a current limiting unit. The charging switch can be a controllable switch, a relay, a direct current contactor, an IGBT or an MOSFET and the like, and can be determined according to actual application scenes. The current limiting unit may be a resistor or an inductor. In fig. 5 or 6, the current limiting means is represented by a resistor R as an example, and the charge switch is represented by a switch K.
Alternatively, in a possible embodiment, as shown in fig. 5, the charging switch (i.e., the switch K) included in the pre-charging unit is connected in series with the current limiting unit (i.e., the resistor R) and then is connected to the first connection end of the switch tube T3 and the second connection end of the switch tube T4, in other words, the charging switch is connected in series with the current limiting unit and then is connected in parallel with the switch tubes T3 and T4 that are connected in series. At this time, the withstand voltage value of the charge switch may be equal to the input voltage of the power supply. In this embodiment, the control unit in the converter may control the pre-charging unit to charge the resonant capacitor in the converter based on the voltage provided by the power supply, and the charging process includes: when the voltage of the resonant capacitor does not reach the target voltage, the control unit in the converter controls the charging switch to be closed, so that the power supply charges the resonant capacitor through a loop formed by the closed charging switch, the current limiting unit, the resonant capacitor, the resonant inductor and the first diode. In other words, as shown in fig. 5, when the switch K is closed, the current path when the power supply charges the resonant capacitor Cr is: vin positive terminal-K-R-Lr-Cr-D0-Vin negative terminal. In the embodiment, the three-level resonant direct-current converter is provided with simple circuit elements such as a switch and a resistor, and the resonant capacitor is precharged based on the electric energy provided by the power supply connected with the converter, so that the three-level resonant direct-current converter is simple in structure and low in circuit cost, and can reduce the possibility that elements such as a switching tube in the circuit are damaged by overcurrent and overvoltage at the moment of conduction when a power conversion unit in the converter starts to work, and improve the safety and the stability of the circuit.
Alternatively, in a possible embodiment, as shown in fig. 6, the charging switch included in the pre-charging unit is connected in series with the current limiting unit and then connected in parallel with the third switching tube (i.e., the switching tube T3). In this case, the withstand voltage of the charge switch can be reduced to half the input voltage of the power supply. In this embodiment, the control unit in the converter charges the resonant capacitor in the converter through the pre-charging unit, and the charging process includes: when the voltage of the resonant capacitor does not reach the target voltage, the control unit in the converter controls the charging switch to be closed and controls the fourth switch tube to be conducted, so that the power supply charges the resonant capacitor through a loop formed by the closed charging switch, the current limiting unit, the fourth switch tube, the resonant capacitor, the resonant inductor and the first diode. In other words, as shown in fig. 6, when the switch K is closed and the switch tube T4 is turned on, the current path when the power supply charges the resonant capacitor Cr is: vin positive terminal-K-R-T4-Lr-Cr-D0-Vin negative terminal. In the embodiment, a switch with smaller voltage withstanding grade can be selected to form a pre-charging loop of the resonant capacitor in the three-level resonant direct-current converter, so that the parameter requirements on components are reduced, the circuit cost is low, the possibility that components such as a switching tube and the like in the circuit are damaged due to overcurrent/overvoltage at the moment of conduction can be reduced when a power conversion unit in the converter starts to work, and the safety and the stability of the circuit are improved.
In a possible embodiment, the converter is configured as shown in fig. 5 or fig. 6, and after the control unit in the converter controls the pre-charging unit to charge the resonant capacitor based on the power provided by the power supply, the control unit may also control the resonant capacitor to charge the filter capacitor. Specifically, the charging process may include: when the voltage of the filter capacitor does not reach the target voltage and the charging switch is closed, if the voltage of the resonant capacitor reaches the preset voltage, the control unit in the converter can control the charging switch to be switched off and control the fifth switching tube and the sixth switching tube to be switched on, so that the resonant capacitor can be charged for the filter capacitor through a loop formed by the resonant inductor, the fifth switching tube, the sixth switching tube, the filter capacitor and the second diode. That is, the control unit controls the resonant capacitor to charge the filter capacitor under the conditions that the voltage of the filter capacitor does not reach the target voltage, the charging switch is closed, and the voltage of the resonant capacitor reaches the preset voltage. As shown in fig. 5 or fig. 6, the current path when the resonant capacitor Cr charges the filter capacitor C is: cr-Lr-T5-T6-C-D0' -Cr. The preset voltage may be a voltage value less than or equal to the target voltage, and may be specifically set according to an actual scene, which is not limited in the present application. It can be understood that, in the above-mentioned multi-round charging process, the values of the preset voltages corresponding to each round of charging may be equal or different, and the application is not limited. Further, when the voltage of the filter capacitor reaches the target voltage, the control unit in the converter may control the fifth switching tube and the sixth switching tube to be turned off, so as to end charging the filter capacitor. In the embodiment, the converter firstly charges the resonant capacitor, and then forms a filter capacitor charging loop through devices such as a switching tube in the multiplexing circuit, so that the resonant capacitor is used for charging the filter capacitor, the energy of the resonant capacitor is transferred to the filter capacitor, and the pre-charging of the filter capacitor is completed.
In some possible embodiments, the process of charging the resonant capacitor and the filter capacitor by the converter as shown in fig. 5 or fig. 6 may also include multiple rounds of charging. Therefore, the charging can be repeated until the voltages of the resonance capacitor and the filter capacitor reach the target voltage. In the last round of charging process, the voltage of the filter capacitor reaches the target voltage, and the control unit can control the fifth switch tube and the sixth switch tube (i.e. the switch tube T5 and the switch tube T6) to be turned off so as to finish charging the filter capacitor. When the voltage of the filter capacitor reaches the target voltage and the voltage of the resonant capacitor reaches the target voltage, the control unit in the converter shown in fig. 5 may control the switch K to be turned off, so as to control the pre-charging unit to be turned off, and end the charging of the resonant capacitor; and the control unit in the converter shown in fig. 6 may control the switch K to be turned off, and control the switching tube T4 in fig. 6 to be turned off, so as to control the pre-charging unit to be turned off, and to end the charging of the resonant capacitor.
Optionally, the pre-charging unit in the converter may be connected in series with the switch K1 and then connected to the power conversion unit or the series resonant unit, so that the control unit may control the pre-charging unit to be turned off by controlling the switch K1 to be turned off. That is, if the pre-charging unit is an integral module and is connected to the converter through the switch K1 connected in series with the pre-charging unit, the control unit in the converter can control whether the pre-charging unit is turned off or not based on the control of the switch K1. Thus, flexibility of control of the precharge unit can be increased, and applicability is high.
It can be understood that the converter has the structure shown in fig. 5 or fig. 6, and then the control unit in the converter can control the power conversion unit to start operating after the control unit in the converter controls the pre-charging unit to charge the resonant capacitor and the filter capacitor to the target voltage based on the electric energy provided by the power supply. Specifically, after the power conversion unit in the converter starts to operate, the driving timing sequence and the resonant current waveform of the converter are as shown in fig. 7, and the operating processes of the switching tube in the converter in different operating modes are as follows:
the working modes 1, 2 and 3 are the transition process of the resonant circuit from the negative half cycle to the positive half cycle. The working mode 1 is turned off at an initial time T6, and then T4 is turned on and T5 is turned off. In the transition process, the resonance current is always 0, and no loss is generated.
The working mode 4 starts to turn on the T3, and the input buses C2 and C3 charge the resonant capacitor Cr through loops T3, T4, lr, cr and D0. After half the resonant period, the resonant current drops to 0, and since the resonant capacitor Cr voltage is now higher than the positive input bus voltage, this state will be maintained until T3 is turned off.
The working modes 5, 6 and 7 are the transition process of the resonant circuit from the positive half cycle to the negative half cycle. T3 is off, T5 is on, and then T4 is off.
The working mode 8 starts to turn on T6, and the resonant capacitor Cr discharges C through Lr, T5, T6, C and D0'. The control switching frequency is less than the resonant frequency of the resonant circuit, so that the resonant current is reduced to 0 when T6 is switched off, and soft switching is realized.
Through the working modes 1-8, the process that energy is transferred from the input bus to the resonant capacitor Cr and then to the output bus (namely two ends of the filter capacitor C) is realized, and each semiconductor device has no switching loss, so that the working efficiency of the circuit is greatly improved.
In the embodiment of the application, the converter can charge the resonant capacitor in the converter by adding simple circuit elements and multiplexing a power supply connected with the converter. A loop for charging the filter capacitor in the converter by the resonant capacitor is formed by devices such as a switch tube in the multiplexing circuit, so that energy of the resonant capacitor can be transferred to the filter capacitor, and the filter capacitor is precharged. The converter has the advantages of simple structure, low circuit cost and simple control logic in the pre-charging process, and can reduce the possibility of damage of elements such as a switching tube and the like in the circuit due to overcurrent/overvoltage at the moment of conduction when a power conversion unit in the converter starts to work, thereby improving the safety and the stability of the converter.
Referring to fig. 8, fig. 8 is a schematic diagram of another structure of the converter provided in the embodiment of the present application. As shown in fig. 8, the converter may include a control unit, a power conversion unit, a series resonance unit, a first pre-charge unit, a second pre-charge unit, and a rectifying and filtering unit. The input end of the power conversion unit can be used as the input end of the converter to be connected with a power supply; the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filter unit is used as the output end of the converter; the first pre-charging unit is connected in parallel with two ends of a resonance capacitor in the series resonance unit, and the second pre-charging unit is connected in parallel with two ends of a filter capacitor in the rectifying and filtering unit.
In some possible embodiments, the control unit in the converter is configured to control the first pre-charging unit to charge the resonant capacitor and control the second pre-charging unit to charge the filter capacitor. That is, the converter includes precharge units provided for the resonance capacitor and the filter capacitor, respectively, to charge the resonance capacitor and the filter capacitor, respectively. The first pre-charging unit and the second pre-charging unit can be flyback circuits, and can also be other circuit topologies, which can be determined according to practical application scenarios, and the present application is not limited. The power supplies connected to the two precharge units may be a power supply connected to the input terminal of the converter, or may be other power supplies separately arranged, which is not limited in this application.
In some possible embodiments, the control unit in the converter is further configured to control the first pre-charging unit to be turned off when the voltage of the resonant capacitor reaches the target voltage, control the second pre-charging unit to be turned off when the voltage of the filter capacitor reaches the target voltage, and control the power conversion unit to start operating. The target voltage can be obtained by the device parameters of the power supply voltage, the resonance capacitor and/or the filter capacitor connected with the converter. The target voltage that the resonant capacitor needs to reach and the target voltage that the filter capacitor needs to reach may be equal voltages or different voltages, and may be specifically determined according to an actual application scenario, which is not limited in this application. As shown in fig. 8, the circuit topology of the power conversion unit in the converter may be the above two-level topology or three-level topology, that is, the power conversion unit of the converter may be the same as the circuit topology of the power conversion unit in fig. 3, or the same as the circuit topology of the power conversion unit in fig. 5 or fig. 6, and the present application is not limited thereto.
In some possible embodiments, the first pre-charging unit and the second pre-charging unit are both flyback circuits. Then, the first pre-charging unit may include a first transformer, a first switching tube, and a first rectifying diode, a primary side of the first transformer is connected to the power supply through the first switching tube, and a secondary side of the first transformer is connected in parallel to two ends of the resonant capacitor through the first rectifying diode; the second pre-charging unit may include a second transformer, a second switching tube, and a second rectifying diode, a primary side of the second transformer is connected to the power supply through the second switching tube, and a secondary side of the second transformer is connected in parallel to both ends of the filter capacitor through the second rectifying diode. Taking the circuit topology of the power conversion unit in the converter as the two-level topology, as shown in fig. 9, the first pre-charging unit may include a transformer Tr1 (i.e., a first transformer), a switching tube Q1 (i.e., a first switching tube), and a diode D3 (i.e., a first rectifying diode), a primary side of Tr1 is coupled to the power source Vin through Q1, one of secondary sides of Tr1 is connected to an anode of D3, a cathode of D3 is connected to an anode of the resonant capacitor, and the other secondary side of Tr1 is connected to a cathode of the resonant capacitor. In other words, the secondary side of Tr2 is connected in parallel to both ends of the resonance unit through D3. The Q1 may be a high-frequency switching tube, the switching type of the Q1 may be an IGBT, or an MOSFET, etc., and the switching characteristic thereof may be determined according to the circuit requirement, which is not limited herein. The power supply voltage can be converted to the secondary side of the Tr1 through the primary side of the Tr1 and power, and the resonant capacitor is charged after being rectified by the diode D3, so that the operation is simple. As shown in fig. 9, the second pre-charging unit may include a transformer Tr2 (i.e., a second transformer), a switch Q2 (i.e., a second switch) and a diode D4 (i.e., a second rectifier diode), where, correspondingly, a primary side of Tr2 is coupled to the power source Vin through Q2, one of secondary sides of Tr2 is connected to an anode of D4, a cathode of D4 is connected to an anode of the filter capacitor, and the other of secondary sides of Tr2 is connected to a cathode of the filter capacitor. In other words, the secondary side of Tr2 is connected in parallel to both ends of the resonance unit through D4. The switch type of Q2 may be IGBT or MOSFET, etc. The power supply voltage can be converted to the secondary side of the Tr2 through the primary side of the Tr2 and power, and the filter capacitor is charged after being rectified by the diode D4, so that the operation is simple. Device parameters such as the number of turns of the secondary side coil of Tr1 and Tr2 can be determined according to the target voltage, and are not limited herein. The first pre-charging unit and the second pre-charging unit are simple in circuit structure and easy to operate when the resonant capacitor and the filter capacitor are charged. Optionally, the primary sides of the transformers Tr1 and Tr2 may be the primary side of the same transformer, and the secondary sides of Tr1 and Tr2 may be different windings output by the secondary side of the same transformer, so that the circuit cost and space may be saved.
Optionally, the first pre-charging unit and the second pre-charging unit in the converter may be respectively connected in series with the switch K1 and the switch K2, and then connected in parallel with the resonant capacitor and the filter capacitor, so that the control unit may control the pre-charging unit to be turned off by controlling the switch K1 and the switch K2 to be turned off. That is, if the first precharge unit and the second precharge unit are an integral module and are connected to the converter through the switch K1 connected in series with the first precharge unit and the second precharge unit, respectively, the control unit in the converter can control the first precharge unit and the second precharge unit to be turned off or operated based on the control of the switch K1 and the switch K2, respectively. Optionally, each of the first pre-charging unit and the second pre-charging unit may include a switch connected to the power supply, and the switch is turned off to control the corresponding pre-charging unit to be turned off, so as to stop charging the resonant capacitor or the filter capacitor. Thus, flexibility of control of the precharge unit can be increased, and applicability is high.
In the embodiment of the application, the converter charges the resonant capacitor and the filter capacitor in the converter by using the first pre-charging unit and the second pre-charging unit respectively, the two charging loops are not affected with each other, the voltage of the resonant capacitor and the voltage of the filter capacitor can reach the target voltage as soon as possible, the charging mode is simple and easy to implement, the possibility that a switch tube in the converter is damaged due to overvoltage/overcurrent at the moment of conduction can be reduced when the power conversion unit starts to work, and the safety and the stability of the circuit are improved.
Referring to fig. 10 and 11, fig. 10 and 11 are schematic views of another structure of the transducer according to the embodiment of the present application. As shown in fig. 10 or 11, the converter may include a control unit, a power conversion unit, a series resonance unit, a pre-charge unit, and a rectification filter unit. The input end of the power conversion unit is used as the input end of the converter and is connected with a power supply; the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filter unit is used as the output end of the converter; the pre-charging unit is connected in parallel with two ends of the resonance capacitor in the series resonance unit.
In some possible embodiments, the rectifier filter unit in the converter may include a filter capacitor, a first diode, and a second diode, the output terminal of the converter may include a first output terminal and a second output terminal, the first diode and the second diode are connected in series and then connected in parallel with the filter capacitor between the first output terminal and the second output terminal of the converter, and a series connection point of the first diode and the second diode serves as an input terminal of the rectifier filter unit. As shown in fig. 10 or 11, the rectifying and filtering unit may include a filter capacitor C and first and second diodes D0 and D0'. The first and second output terminals of the converter may be the positive and negative terminals Vout and Vout, respectively, in the figure.
In some possible embodiments, the control unit in the converter may be configured to control the switching tubes connected between the output end of the power conversion unit and the filter capacitor in the power conversion unit to be turned on, so as to control the pre-charging unit to charge the resonant capacitor, and to charge the filter capacitor through a loop formed by the resonant inductor in the series resonant unit, the switching tube between the output end of the power conversion unit and the filter capacitor, and the second diode. The precharge unit may be a flyback circuit or other circuit topologies, and the present application is not limited thereto. Understandably, in the converter shown in fig. 10, the switch tube between the output end of the power conversion unit and the filter capacitor includes a switch tube T2. Then, in the converter, when T2 is turned on, the loop formed by Lr, T2, C, D0' and the resonant capacitor Cr are connected in parallel to both ends of the pre-charge unit, so that the pre-charge unit can charge Cr and C at the same time. In the converter shown in fig. 10, the switching tube between the output end of the power conversion unit and the filter capacitor includes switching tubes T5 and T6. Then, in this converter, when T5 and T6 are both turned on, the loop formed by Lr, T5, T6, C and D0' and the resonant capacitor Cr are connected in parallel to both ends of the precharge unit, so that the precharge unit can charge Cr and C at the same time.
In some possible embodiments, the control unit in the converter is further configured to control the pre-charging unit to be turned off, control the switching tube between the output terminal of the power conversion unit and the filter capacitor to be turned off, and control the power conversion unit to start operating when the voltages of the resonant capacitor and the filter capacitor reach the target voltage. The switching off of the pre-charging unit, that is, the switching off of the pre-charging unit, can be realized by controlling the power supply in the pre-charging unit to stop supplying power, controlling the switch in the pre-charging unit to be switched off, and the like. Optionally, the pre-charging unit may be connected in series with the switch K1 and then connected in parallel to two ends of the resonant capacitor, so that the pre-charging unit may be controlled to be turned off by controlling the switch K1 to be turned off. Understandably, in the converter as shown in fig. 10, when the voltage of the resonant capacitor and the filter capacitor reaches the target voltage, the control unit in the converter needs to control the switch tube T2 to be turned off in addition to controlling the pre-charging unit to be turned off. In the converter shown in fig. 11, when the voltages of the resonant capacitor and the filter capacitor reach the target voltages, the control unit in the converter needs to control the switching tubes T5 and T6 to be turned off in addition to controlling the pre-charging unit to be turned off.
In some possible embodiments, the circuit topology of the precharge unit in the converter as shown in fig. 10 or fig. 11 may be a flyback circuit. That is, the precharge unit may include a transformer, a first switching tube, and a rectifying diode. The primary side of the transformer is connected with a power supply through a first switching tube, and the secondary side of the transformer is connected in parallel with two ends of the resonant capacitor through a rectifier diode. Taking the converter shown in fig. 11 as an example, as shown in fig. 12, the precharge unit includes a transformer Tr1, a switching tube Q1, and a diode D3. The primary side of Tr1 is coupled to a power source Vin through Q1, one side of the secondary side of Tr1 is connected with the positive electrode of D3, the negative electrode of D3 is connected with the positive electrode of the resonant capacitor, and the other side of the secondary side of Tr1 is connected with the negative electrode of the resonant capacitor. In other words, the secondary side of Tr1 is connected in parallel to both ends of the resonance capacitance through D3. The Q1 may be a high-frequency switch tube, the switch type of the Q1 may be an IGBT or an MOSFET, and the switching characteristic thereof may be determined according to a circuit requirement, which is not limited herein. The power supply voltage can be converted to the secondary side of the Tr1 through the primary side of the Tr1 and power, and the resonant capacitor and the filter capacitor are charged after being rectified by the diode D3, so that the operation is simple.
In the embodiment of the application, the pre-charging unit in the converter is connected in parallel at two ends of the resonant capacitor in the converter, and the control unit controls the switch tube between the output end of the power conversion unit and the filter capacitor to be connected in parallel, so that the resonant capacitor and the filter capacitor are equivalently connected in parallel, the control unit can control the pre-charging unit to charge the resonant capacitor and the filter capacitor simultaneously, and the voltage of the resonant capacitor and the voltage of the filter capacitor reach the target voltage. The converter utilizes a pre-charging unit to realize the common charging of the resonant capacitor and the filter capacitor, can reduce the possibility of the damage of a switch tube in the converter due to overvoltage/overcurrent when the power conversion unit starts to work, improves the safety and the stability of a circuit, and has the advantages of simple circuit structure, low cost and high charging speed.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (14)

1. The converter is characterized by comprising a control unit, a power conversion unit, a series resonance unit, a pre-charging unit and a rectifying and filtering unit; the input end of the power conversion unit is used as the input end of the converter to be connected with a power supply, and the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filtering unit is used as the output end of the converter; the pre-charging unit is connected between the positive electrode output end of the power supply and the output end of the power conversion unit in parallel;
the control unit is used for controlling the pre-charging unit to charge a resonance capacitor in the series resonance unit and a filter capacitor in the rectifying and filtering unit based on the electric energy provided by the power supply;
the control unit is further used for controlling the pre-charging unit to be disconnected and controlling the power conversion unit to work when the voltage of the resonance capacitor and the voltage of the filter capacitor reach target voltages.
2. The converter according to claim 1, wherein the rectifying and filtering unit comprises the filter capacitor and a first diode and a second diode, the output terminal of the converter comprises a first output terminal and a second output terminal, the first diode and the second diode are connected in series and then connected in parallel with the filter capacitor between the first output terminal and the second output terminal of the converter, and the series connection point of the first diode and the second diode serves as the input terminal of the rectifying and filtering unit;
the power conversion unit comprises a first switch tube and a second switch tube, the first switch tube and the second switch tube are connected in series and then connected in parallel to two ends of the power supply, and the series connection point of the first switch tube and the second switch tube is used as the output end of the power conversion unit;
the pre-charging unit is connected in parallel with two ends of the first switching tube.
3. The converter according to claim 2, wherein the pre-charging unit comprises a charging switch and a current limiting unit, and the charging switch and the current limiting unit are connected in series and then connected in parallel with the first switching tube;
the control unit is used for controlling the charging switch to be closed when the voltage of the resonant capacitor does not reach the target voltage, so that the power supply can charge the resonant capacitor through the charging switch, the current limiting unit, the series resonant unit and a loop formed by the first diode.
4. The converter according to claim 3, wherein the control unit is further configured to control the charging switch to be turned off and the second switching tube to be turned on when the voltage of the filter capacitor does not reach the target voltage, the charging switch is turned on, and the voltage of the resonant capacitor reaches a preset voltage, so that the resonant capacitor charges the filter capacitor through a loop formed by a resonant inductor in the series resonant unit, the second switching tube, the filter capacitor, and the second diode, and the preset voltage is less than or equal to the target voltage;
the control unit is further configured to control the second switching tube to be turned off when the voltage of the filter capacitor reaches the target voltage, so as to end charging of the filter capacitor.
5. The converter according to claim 1, wherein the rectifying and filtering unit comprises the filter capacitor and a first diode and a second diode, the output terminal of the converter comprises a first output terminal and a second output terminal, the first diode and the second diode are connected in series and then connected in parallel with the filter capacitor between the first output terminal and the second output terminal of the converter, and the series connection point of the first diode and the second diode serves as the input terminal of the rectifying and filtering unit;
the power conversion unit comprises a third switching tube, a fourth switching tube, a fifth switching tube, a sixth switching tube, a first capacitor, a second capacitor, a third diode and a fourth diode which are connected in series; the first capacitor and the second capacitor which are connected in series are connected with the third switching tube, the fourth switching tube, the fifth switching tube and the sixth switching tube which are connected in series in parallel at two ends of the power supply, the third diode and the fourth diode which are connected in series are connected in parallel with the fourth switching tube and the fifth switching tube which are connected in series, and the series connection point of the third diode and the fourth diode is connected with the series connection point of the first capacitor and the second capacitor; a series connection point of the fourth switching tube and the fifth switching tube is used as an output end of the power conversion unit;
the pre-charging unit is connected in parallel with two ends of the third switching tube and the fourth switching tube which are connected in series; or, the pre-charging unit is connected in parallel to two ends of the third switching tube.
6. The converter according to claim 5, wherein the pre-charging unit comprises a charging switch and a current limiting unit, and the charging switch and the current limiting unit are connected in series and then connected in parallel with the third switching tube and the fourth switching tube which are connected in series;
the control unit is used for controlling the charging switch to be closed when the voltage of the resonant capacitor does not reach the target voltage, so that the power supply can charge the resonant capacitor through the charging switch, the current limiting unit, the series resonant unit and a loop formed by the first diode.
7. The converter according to claim 5, wherein the pre-charging unit comprises a charging switch and a current limiting unit, and the charging switch and the current limiting unit are connected in series and then connected in parallel with the third switching tube;
the control unit is used for controlling the charging switch to be closed and the fourth switch tube to be conducted when the voltage of the resonant capacitor does not reach the target voltage, so that the power supply passes through the charging switch and the current-limiting unit, the fourth switch tube, the series resonant unit and a loop formed by the first diode are charged by the resonant capacitor.
8. The converter according to claim 6 or 7, wherein the control unit is further configured to control the charging switch to be turned off, the fifth switching tube and the sixth switching tube to be turned on when the voltage of the filter capacitor does not reach the target voltage, the charging switch is turned on, and the voltage of the resonant capacitor reaches a preset voltage, so that the resonant capacitor charges the filter capacitor through a loop formed by a resonant inductor in the series resonant unit, the fifth switching tube, the sixth switching tube, the filter capacitor and the second diode, and the preset voltage is less than or equal to the target voltage;
the control unit is further configured to control the fifth switching tube and the sixth switching tube to be turned off when the voltage of the filter capacitor reaches the target voltage, so as to end charging of the filter capacitor.
9. The converter according to any one of claims 3-8, wherein the control unit is further configured to control the charging switch to be turned off to control the pre-charging unit to be turned off when the voltage of the filter capacitor and the voltage of the resonant capacitor reach the target voltage.
10. The converter is characterized by comprising a control unit, a power conversion unit, a series resonance unit, a first pre-charging unit, a second pre-charging unit and a rectifying and filtering unit; the input end of the power conversion unit is used as the input end of the converter to be connected with a power supply, and the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filter unit is used as the output end of the converter;
the first pre-charging unit is connected in parallel with two ends of a resonance capacitor in the series resonance unit, and the second pre-charging unit is connected in parallel with two ends of a filter capacitor in the rectifying and filtering unit;
the control unit is used for controlling the first pre-charging unit to charge the resonance capacitor and controlling the second pre-charging unit to charge the filter capacitor;
the control unit is further used for controlling the first pre-charging unit to be disconnected when the voltage of the resonance capacitor reaches a target voltage, controlling the second pre-charging unit to be disconnected when the voltage of the filter capacitor reaches the target voltage, and controlling the power conversion unit to work.
11. The converter according to claim 10, wherein the first pre-charging unit comprises a first transformer, a first switch tube and a first rectifying diode, wherein a primary side of the first transformer is connected to the power supply through the first switch tube, and a secondary side of the first transformer is connected in parallel to two ends of the resonant capacitor through the first rectifying diode;
the second pre-charging unit comprises a second transformer, a second switching tube and a second rectifying diode, the primary side of the second transformer is connected with the power supply through the second switching tube, and the secondary side of the second transformer is connected in parallel with two ends of the filter capacitor through the second rectifying diode.
12. The converter is characterized by comprising a control unit, a power conversion unit, a series resonance unit, a pre-charging unit and a rectifying and filtering unit; the input end of the power conversion unit is used as the input end of the converter and is connected with a power supply; the output end of the power conversion unit is connected with the input end of the rectification filter unit through the series resonance unit; the output end of the rectification filter unit is used as the output end of the converter; the pre-charging unit is connected in parallel with two ends of a resonance capacitor in the series resonance unit;
the rectifying and filtering unit comprises the filter capacitor, a first diode and a second diode, the output end of the converter comprises a first output end and a second output end, the first diode and the second diode are connected in series and then connected in parallel between the first output end and the second output end of the converter with the filter capacitor, and the series connection point of the first diode and the second diode is used as the input end of the rectifying and filtering unit;
the control unit is used for controlling the conduction of a switch tube connected between the output end of the power conversion unit and the filter capacitor in the power conversion unit so as to control the pre-charging unit to charge the resonance capacitor and the filter capacitor;
and the control unit is also used for controlling the pre-charging unit to be disconnected, controlling the switching tubes between the output end of the power conversion unit and the filter capacitor to be switched off and controlling the power conversion unit to work when the voltages of the resonance capacitor and the filter capacitor reach the target voltage.
13. The converter according to claim 12, wherein the pre-charging unit comprises a transformer, a first switch tube and a rectifier diode, a primary side of the transformer is connected to the power supply through the first switch tube, and a secondary side of the transformer is connected in parallel to two ends of the resonant capacitor through the rectifier diode.
14. An inverter, characterized in that the inverter comprises an inverting unit and a converter according to any one of claims 1-13, the converter being connected to a load via the inverting unit;
the inverter unit is used for converting the direct current output by the converter into alternating current to supply power to the load.
CN202211058310.XA 2022-08-30 2022-08-30 Converter and inverter Pending CN115411921A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202211058310.XA CN115411921A (en) 2022-08-30 2022-08-30 Converter and inverter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202211058310.XA CN115411921A (en) 2022-08-30 2022-08-30 Converter and inverter

Publications (1)

Publication Number Publication Date
CN115411921A true CN115411921A (en) 2022-11-29

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Family Applications (1)

Application Number Title Priority Date Filing Date
CN202211058310.XA Pending CN115411921A (en) 2022-08-30 2022-08-30 Converter and inverter

Country Status (1)

Country Link
CN (1) CN115411921A (en)

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