CN116865547B - Soft start method and soft start circuit - Google Patents

Soft start method and soft start circuit Download PDF

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Publication number
CN116865547B
CN116865547B CN202311134026.0A CN202311134026A CN116865547B CN 116865547 B CN116865547 B CN 116865547B CN 202311134026 A CN202311134026 A CN 202311134026A CN 116865547 B CN116865547 B CN 116865547B
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China
Prior art keywords
circuit
voltage value
llc
soft start
output voltage
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CN116865547A (en
Inventor
尹鹏
刘中伟
石伟
杨志龙
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Xi'an Topology Electric Power Technology Co ltd
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Xi'an Topology Electric Power Technology Co ltd
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Classifications

    • 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
    • H02M1/36—Means for starting or stopping converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • 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
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • 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
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4241—Arrangements for improving power factor of AC input using a resonant converter
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33571—Half-bridge at primary side of an isolation transformer
    • 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
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer

Abstract

The application relates to a soft start method and a soft start circuit, which are used in a charging circuit, wherein the charging circuit comprises a PFC circuit and an LLC circuit, and the method comprises the following steps: inputting voltage to a bus at the output end side of the PFC circuit through the external power supply so as to enable the bus voltage at the output end side of the PFC circuit to reach a first bus voltage value; controlling the LLC circuit to perform a first stage soft start so as to enable the output voltage of the LLC circuit to reach a first output voltage value; and controlling the PFC circuit and the LLC circuit to synchronously perform a second-stage soft start so as to enable the bus voltage at the output end side of the PFC circuit to reach a second bus voltage value and enable the LLC circuit output voltage to reach a second output voltage value. The method can reduce the time of soft start.

Description

Soft start method and soft start circuit
Technical Field
The application relates to the technical field of battery energy storage, in particular to a soft start method and a soft start circuit.
Background
With the development of new energy industry, battery energy storage technology is developed. During battery charging, PFC and LLC circuits are required. Before charging the battery, soft start of the PFC circuit and the LLC circuit is first required.
In the prior art, PFC soft start is performed to obtain a stable bus voltage, and then the stable bus voltage is input into an LLC circuit to perform soft start to obtain a stable direct current output voltage.
However, the soft start is performed for a long time by the conventional technique.
Disclosure of Invention
Accordingly, it is desirable to provide a soft start method and a soft start circuit for reducing the duration of soft start.
In a first aspect, the present application provides a soft start method, for use in a charging circuit, where the charging circuit includes a PFC circuit and an LLC circuit, where an input end of the PFC circuit is connected to an external power source, and an output end of the PFC circuit is connected to an input end of the LLC circuit, the method includes:
inputting voltage to a bus at the output end side of the PFC circuit through the external power supply so as to enable the bus voltage at the output end side of the PFC circuit to reach a first bus voltage value; controlling the LLC circuit to perform a first stage soft start so as to enable the output voltage of the LLC circuit to reach a first output voltage value; and controlling the PFC circuit and the LLC circuit to synchronously perform a second-stage soft start so as to enable the bus voltage at the output end side of the PFC circuit to reach a second bus voltage value and enable the LLC circuit output voltage to reach a second output voltage value.
In one embodiment, the controlling the PFC circuit and the LLC circuit to perform the second-stage soft start synchronously, so that the bus voltage at the output end side of the PFC circuit reaches a second bus voltage value, and the LLC circuit output voltage reaches a second output voltage value, includes:
and controlling the PFC circuit and the LLC circuit to synchronously perform a second-stage soft start so as to enable the bus voltage at the output end side of the PFC circuit to be increased from the first bus voltage value to the second bus voltage value according to a first slope and enable the LLC circuit output voltage to be increased from the first output voltage value to the second output voltage value according to a second slope.
In one embodiment, the LLC circuit includes a transformer, the first output voltage value being determined in accordance with the first bus voltage value, a number of primary winding turns of the transformer, a number of secondary winding turns of the transformer, and a preset gain value.
In one embodiment, the PFC circuit includes a soft start circuit, a first inductor, and a first full bridge circuit that are sequentially connected, the soft start circuit includes a soft start resistor and a soft start relay that are connected in parallel, and the voltage is input to a bus at an output end side of the PFC circuit through the external power supply, so that the bus voltage at the output end side of the PFC circuit reaches a first bus voltage value, and the method includes:
Controlling the soft start relay to be in an off state so as to form a starting path consisting of the external power supply, the soft start resistor, the first inductor and the first full-bridge circuit; and inputting voltage to a bus at the output end side of the PFC circuit by the external power supply based on the starting path so as to enable the bus voltage at the output end side of the PFC circuit to reach the first bus voltage value.
In one embodiment, the controlling the LLC circuit to perform a first stage soft start to bring the output voltage of the LLC circuit to a first output voltage value includes:
after the bus voltage at the output end side of the PFC circuit reaches the first bus voltage value, controlling the soft start relay to be closed; and after the soft start relay is closed, controlling the LLC circuit to perform a first stage soft start so as to enable the output voltage of the LLC circuit to reach the first output voltage value.
In one embodiment, the LLC circuit includes a transformer, a primary side of the transformer includes a half-bridge circuit and an LC series resonant unit connected in sequence, a secondary side of the transformer includes a second full-bridge circuit, and the control of the LLC circuit to perform a first stage soft start so that an output voltage of the LLC circuit reaches the first output voltage value includes:
And controlling a switching tube in the half-bridge circuit and a switching tube in the second full-bridge circuit to work according to a first preset working mode so as to enable the output voltage of the LLC circuit to reach the first output voltage value.
In one embodiment, the controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to operate according to a first preset operation mode includes:
and controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to operate based on a constant operating frequency and a constant duty cycle.
In one embodiment, the controlling the PFC circuit and the LLC circuit to perform the second-stage soft start synchronously, so that the bus voltage at the output end side of the PFC circuit reaches a second bus voltage value, and the LLC circuit output voltage reaches a second output voltage value, includes:
and controlling the switching tube in the first full-bridge circuit to work, synchronously controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to work according to a second preset working mode, so that the bus voltage at the output end side of the PFC circuit reaches the second bus voltage value, and the LLC circuit output voltage reaches the second output voltage value.
In one embodiment, the synchronously controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit operates according to a second preset operation mode, including:
and synchronously controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to work based on a constant working frequency and a monotonically increasing duty ratio curve.
In a second aspect, the application further provides a soft start circuit, which comprises a controller and a charging circuit, wherein the charging circuit comprises a PFC circuit and an LLC circuit, the input end of the PFC circuit is connected with an external power supply, and the output end of the PFC circuit is connected with the input end of the LLC circuit; the controller is configured to perform the method steps of any one of the first aspect.
According to the soft start method and the soft start circuit, the bus voltage at the output end side of the PFC circuit reaches the first bus voltage value through the bus input voltage at the output end side of the PFC circuit by the external power supply, the LLC circuit is used for performing first-stage soft start, the output voltage of the LLC circuit reaches the first output voltage value, the PFC circuit and the LLC circuit are controlled to synchronously perform second-stage soft start on the premise that the bus voltage at the output end side of the PFC circuit reaches the first output voltage value, the bus voltage at the output end side of the PFC circuit reaches the second bus voltage value, and the LLC circuit output voltage reaches the second output voltage value, namely, the bus voltage at the output end side of the PFC circuit and the LLC circuit output voltage at the second-stage soft start time are synchronously increased in the second-stage soft start mode, in the prior art, the output time of the soft start time of the LLC circuit is reduced from the second-stage voltage of the PFC circuit is shortened, and the output time of the LLC circuit reaches the second-stage soft start time is shortened, and the soft start time of the LLC circuit is shortened.
Drawings
FIG. 1 is a schematic diagram of a connection between a charging circuit and an external power source in one embodiment;
FIG. 2 is a flow chart of a soft start method in one embodiment;
fig. 3 is a schematic flow chart of inputting a voltage to a bus at an output end side of the PFC circuit by an external power source so that the bus voltage at the output end side of the PFC circuit reaches a first bus voltage value in one embodiment;
fig. 4 is a circuit diagram of a PFC circuit in one embodiment;
FIG. 5 is a flow chart of controlling the LLC circuit to perform a first stage soft start to enable the output voltage of the LLC circuit to reach a first output voltage value according to one embodiment;
FIG. 6 is a circuit diagram of LLC circuitry in one embodiment;
FIG. 7 is a circuit diagram of an input of a PFC circuit connected to an external power source, an output of the PFC circuit connected to an input of an LLC circuit, according to an embodiment;
FIG. 8 is a flow chart of a soft start method in an exemplary embodiment;
fig. 9 is a graph of a bus voltage at an output side of the PFC circuit in an exemplary embodiment;
FIG. 10 is a graph of output voltage waveforms of an LLC circuit in an exemplary embodiment;
FIG. 11 is a waveform diagram of an operating frequency curve of an LLC circuit in an exemplary embodiment;
FIG. 12 is a schematic diagram of the duty cycle of a switching tube in a half-bridge circuit in an LLC circuit in an exemplary embodiment;
FIG. 13 is a schematic diagram of the duty cycle of a switching tube in a second full bridge circuit in an LLC circuit in an exemplary embodiment;
FIG. 14 is a schematic diagram of a soft start circuit in one embodiment;
fig. 15 is a circuit diagram of an input terminal of a PFC circuit connected to an external power supply and an output terminal of the PFC circuit connected to an input terminal of an LLC circuit in a soft start circuit according to an embodiment.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
The soft start method provided by the embodiment of the application can be applied to a charging circuit shown in fig. 1. Fig. 1 shows a connection between the charging circuit 120 and the external power supply 140, wherein the charging circuit 120 includes a PFC circuit 122 and an LLC circuit 124, an input terminal of the PFC circuit 122 is connected to the external power supply 140, and an output terminal of the PFC circuit 122 is connected to an input terminal of the LLC circuit 124.
In one embodiment, as shown in fig. 2, a soft start method is provided, which is applied to the charging circuit 120 in fig. 1, and includes the following steps:
in step 202, a voltage is input to a bus on the output side of the PFC circuit by an external power source, so that the bus voltage on the output side of the PFC circuit reaches a first bus voltage value.
The PFC in the PFC circuit is "Power Factor Correction" (power factor correction), where the power factor is often used to characterize the utilization efficiency of the electronic product on the electric energy, and the higher the power factor of the electronic product, the higher the electric energy utilization efficiency of the electronic product; the PFC circuit comprises a soft start circuit, a first inductor and a first full-bridge circuit which are sequentially connected, wherein the soft start circuit comprises a soft start resistor and a soft start relay which are connected in parallel.
Optionally, when the voltage input by the external power supply enters the PFC circuit, the voltage input by the external power supply may enter a start-up path formed by the soft start circuit, the first inductor and the first full bridge circuit, and the bus voltage at the output end side of the PFC circuit reaches the first bus voltage value through the processing of the start-up path.
In step 204, the LLC circuit is controlled to perform a first stage soft start to enable the output voltage of the LLC circuit to reach a first output voltage value.
The LLC circuit comprises a transformer, a primary side of the transformer comprises a half-bridge circuit and an LC series resonance unit which are sequentially connected, and a secondary side of the transformer comprises a second full-bridge circuit.
Optionally, the bus voltage reaching the first bus voltage value in step 202 is input to the LLC circuit, and the output voltage of the LLC circuit is made to reach the first output voltage value through processing of the half-bridge circuit, the LC series resonant unit, and the second full-bridge circuit in the LLC circuit.
And 206, controlling the PFC circuit and the LLC circuit to synchronously perform a second stage soft start so as to enable the bus voltage at the output end side of the PFC circuit to reach a second bus voltage value and enable the LLC circuit output voltage to reach a second output voltage value.
Optionally, the PFC circuit is controlled to perform a second stage soft start, namely, the bus voltage at the output end side of the PFC circuit reaching the first bus voltage value is processed through a first full-bridge circuit in the PFC circuit, so that the bus voltage at the output end side of the PFC circuit reaches the second bus voltage value; meanwhile, the LLC circuit is synchronously controlled to carry out second-stage soft start, namely, the output voltage of the LLC circuit reaching the first output voltage value is processed through a half-bridge circuit and a second full-bridge circuit in the LLC circuit, so that the output voltage of the LLC circuit reaches the second output voltage value.
In the soft start method, the voltage is input to the bus at the output end side of the PFC circuit through the external power supply, so that the bus voltage at the output end side of the PFC circuit reaches a first bus voltage value; controlling the LLC circuit to perform first-stage soft start so as to enable the output voltage of the LLC circuit to reach a first output voltage value; and controlling the PFC circuit and the LLC circuit to synchronously perform the second stage soft start so as to enable the bus voltage at the output end side of the PFC circuit to reach a second bus voltage value and enable the LLC circuit output voltage to reach a second output voltage value. The method comprises the steps of inputting voltage to a bus at the output end side of a PFC circuit through an external power supply, enabling the bus at the output end side of the PFC circuit to reach a first bus voltage value, performing first-stage soft start through an LLC circuit, enabling the bus at the output end side of the LLC circuit to reach a first output voltage value, controlling the PFC circuit and the LLC circuit to synchronously perform second-stage soft start on the premise that the bus at the output end side of the PFC circuit reaches the first bus voltage value and the output voltage of the LLC circuit reaches the first output voltage value, enabling the bus at the output end side of the PFC circuit to reach a second bus voltage value, enabling the output voltage of the LLC circuit to reach the second output voltage value, namely enabling the bus at the output end side of the PFC circuit and the output voltage of the LLC circuit to synchronously increase in the second-stage soft start, and enabling the output time of the LLC circuit to be reduced from the second-stage soft start time of the LLC circuit after the bus at the output end side of the PFC circuit reaches the second bus voltage value to reach the second bus voltage value.
In the above embodiment, the process of bringing the bus voltage on the output side of the PFC circuit to the second bus voltage value and bringing the output voltage of the LLC circuit to the second output voltage value is described. In this embodiment, further describing, controlling the PFC circuit and the LLC circuit to perform the second stage soft start synchronously, so that the bus voltage at the output end side of the PFC circuit reaches a second bus voltage value, and the LLC circuit output voltage reaches a second output voltage value, includes:
the PFC circuit and the LLC circuit are controlled to synchronously perform a second-stage soft start so that the bus voltage at the output end side of the PFC circuit is increased from a first bus voltage value to a second bus voltage value according to a first slope, and the LLC circuit output voltage is increased from a first output voltage value to a second output voltage value according to a second slope.
Alternatively, the first slope is defined ask 1 The second slope is defined ask 2 Here, wherek 1 Andk 2 the present application is not limited to this, and may be a fixed value or a variable value. At a first slopek 1 The voltage value of the bus voltage at the output end side of the PFC circuit monotonically increases; at a second slopek 2 Next, the voltage value of the LLC circuit output voltage monotonically increases. Controlling a first full-bridge circuit in the PFC circuit to enable the first full-bridge circuit to work in a preset working mode, and enabling the bus voltage at the output end side of the PFC circuit to be in slope from a first bus voltage value through the first full-bridge circuit in the preset working mode k 1 Increasing to a second bus voltage value; the half-bridge circuit and the second full-bridge circuit in the LLC circuit are controlled to work in a preset working mode, and the LLC circuit output voltage is led to be led to work from the first output voltage value according to the slope through the half-bridge circuit and the second full-bridge circuit working in the preset working modek 2 To a second output voltage value.
In this embodiment, the PFC circuit and the LLC circuit are controlled to perform the second-stage soft start in synchronization, so that the bus voltage at the output end side of the PFC circuit increases from the first bus voltage value to the second bus voltage value according to the first slope, and the LLC circuit output voltage increases from the first output voltage value to the second output voltage value according to the second slope. The bus voltage at the output end side of the PFC circuit is increased from the first bus voltage value to the second bus voltage value according to the first slope, and the LLC circuit output voltage is increased from the first output voltage value to the second output voltage value according to the second slope, because the first slope and the second slope are both fixed values, the PFC circuit and the LLC circuit can keep fixed gains in the soft start process, the PFC circuit and the LLC circuit are more stable, and meanwhile, the PFC circuit and the LLC circuit synchronously perform the soft start process of the second stage, compared with the traditional technology, the time for enabling the output voltage of the LLC circuit to reach the second output voltage value from 0 is greatly reduced, and therefore the duration of soft start can be reduced.
In the above embodiment, the process of performing the second stage soft start by the PFC circuit and the LLC circuit is referred to. In this embodiment, further describing that the LLC circuit includes a transformer, the first output voltage value is determined based on the first bus voltage value, the number of primary winding turns of the transformer, the number of secondary winding turns of the transformer, and a preset gain value.
The transformer comprises a primary winding and a secondary winding, and the preset gain value characterizes the gain of the LLC circuit.
Optionally, the first bus voltage value is defined asV bus1 The number of turns of the primary winding of the transformer isN 1 Secondary winding turns of transformerN 2 The preset gain value isMThe first output voltage isV out1 . Calculating according to formula (1) to obtain a first output voltage value ofV out1 。
（1）
Voltage value of first busV bus1 The number of turns of the primary winding of the transformer isN 1 Secondary winding turns of transformerN 2 The preset gain value isMInput to equation (1) to determine the firstThe output voltage value isV out1 。
In this embodiment, the LLC circuit includes a transformer, and the first output voltage value is determined according to the first bus voltage value, the number of turns of the primary winding of the transformer, the number of turns of the secondary winding of the transformer, and a preset gain value. The first output voltage value is determined through the first bus voltage value, the number of turns of the primary winding of the transformer, the number of turns of the secondary winding of the transformer and a preset gain value, so that the circuit keeps constant gain in the soft start process of the first stage, the LLC circuit is more stable, meanwhile, the output voltage of the LLC circuit reaches the first output voltage value through the soft start of the first stage, and then the time required for increasing the output voltage of the LLC circuit to the second output voltage value is greatly reduced compared with the time required for directly increasing the output voltage of the LLC circuit from 0 to the second output voltage value, so that the time for obtaining the output voltage of the LLC circuit can be reduced.
In the previous embodiment, a process of determining a first output voltage value was involved. In this embodiment, further describing that the PFC circuit includes a soft start circuit, a first inductor, and a first full-bridge circuit that are sequentially connected, the soft start circuit includes a soft start resistor and a soft start relay that are connected in parallel, and voltage is input to a bus on an output end side of the PFC circuit through an external power supply, so that the bus voltage on the output end side of the PFC circuit reaches a first bus voltage value, and a flow is shown in fig. 3, and includes:
in step 302, the soft start relay is controlled to be in an off state to form a start-up path consisting of an external power supply, a soft start resistor, a first inductor and a first full bridge circuit.
The circuit diagram of the PFC circuit is shown in fig. 4, where the power grid 400 is an external power supply, RT1 is a soft-start resistor, L1 is a first inductor, rli is a soft-start relay, Q1, Q2, Q3, and Q4 are respectively four switching tubes in the first full-bridge circuit, and Vbus is a bus voltage at an output end side of the PFC circuit.
Optionally, the power grid 400 inputs voltage to a bus at the output end side of the PFC circuit, and at this time, the soft start relay rli is controlled to be in an off state, so as to form a start path formed by the power grids 400, RT1, L1, Q2, Q3, and Q4.
In step 304, the external power supply inputs a voltage to the bus on the output side of the PFC circuit based on the start-up path, so that the bus voltage on the output side of the PFC circuit reaches the first bus voltage value.
Optionally, the power grid 400 inputs voltage to the bus at the output end of the PFC circuit, and controls Q1, Q2, Q3, Q4 based on a start-up path formed by the power grids 400, RT1, L1, Q2, Q3, Q4 to make Q1, Q2, Q3, Q4 operate in a mode of constant operating frequency and a first preset duty ratio so as to make the bus voltage at the output end of the PFC circuit reach a first bus voltage valueV bus1 . The first preset duty cycle is calculated from the voltage value of the bus voltage at the output end of the PFC circuit and the instantaneous value of the input voltage of the power grid 400.
In the embodiment, a starting path consisting of an external power supply, a soft start resistor, a first inductor and a first full-bridge circuit is formed by controlling the soft start relay to be in an off state; the external power supply inputs a voltage to a bus on the output end side of the PFC circuit based on the start-up path, so that the bus voltage on the output end side of the PFC circuit reaches a first bus voltage value. The external power supply inputs the voltage to the bus at the output end side of the PFC circuit based on the starting path, so that the bus voltage at the output end side of the PFC circuit reaches the first bus voltage value, and loss of the input voltage of the external power supply can be reduced, therefore, the bus voltage at the output end side of the PFC circuit can reach the first bus voltage value in a shorter time under the condition of receiving the same input voltage of the external power supply, and the output voltage of the LLC circuit can be obtained in a shorter time after the bus voltage at the output end side of the PFC circuit is input into the LLC circuit.
In the above embodiment, the process of bringing the bus voltage on the output side of the PFC circuit to the first bus voltage value is involved. In this embodiment, further describing, the control LLC circuit performs a first stage soft start to enable the output voltage of the LLC circuit to reach a first output voltage value, and the flowchart shown in fig. 5 includes:
and step 502, after the bus voltage at the output end side of the PFC circuit reaches a first bus voltage value, controlling the soft start relay to be closed.
The circuit diagram of the PFC circuit is shown in fig. 4, where the power grid 400 is an external power supply, RT1 is a soft-start resistor, L1 is a first inductor, rli is a soft-start relay, Q1, Q2, Q3, and Q4 are respectively four switching tubes in the first full-bridge circuit, and Vbus is a bus voltage at an output end side of the PFC circuit.
Optionally, the power grid 400 inputs voltage to the bus at the output end of the PFC circuit, and controls Q1, Q2, Q3, Q4 based on a start-up path formed by the power grids 400, RT1, L1, Q2, Q3, Q4 to make Q1, Q2, Q3, Q4 operate in a mode of constant operating frequency and a first preset duty ratio so as to make the bus voltage at the output end of the PFC circuit reach a first bus voltage valueV bus1 The bus voltage at the output end side of the PFC circuit reaches a first bus voltage value V bus1 And then, controlling the soft start relay RLY to be closed.
In step 504, after the soft start relay is closed, the LLC circuit is controlled to perform a first stage soft start to enable the output voltage of the LLC circuit to reach a first output voltage value.
The LLC circuit comprises a transformer, a primary side of the transformer comprises a half-bridge circuit and an LC series resonance unit which are sequentially connected, and a secondary side of the transformer comprises a second full-bridge circuit.
Optionally, the first bus voltage value is reached in step 502V bus1 Is input into an LLC circuit, and the output voltage of the LLC circuit reaches a first output voltage value through the processing of a half-bridge circuit, an LC series resonance unit and a second full-bridge circuit in the LLC circuitV out1 。
In the embodiment, after the bus voltage at the output end side of the PFC circuit reaches a first bus voltage value, the soft start relay is controlled to be closed; after the soft start relay is closed, the LLC circuit is controlled to perform a first stage soft start so that the output voltage of the LLC circuit reaches a first output voltage value. After the soft start relay is closed, the LLC circuit is controlled to perform a first stage soft start so that the output voltage of the LLC circuit reaches a first output voltage value, so that the output voltage of the LLC circuit can be obtained stably, namely, after the soft start relay is closed in the first stage of the LLC circuit, the output voltage of the LLC circuit reaches a stable voltage value, and the time required for obtaining the voltage value of the output voltage of the final LLC circuit based on the stable voltage value is shorter than the time required for increasing the output voltage of the LLC circuit from 0 to the voltage value of the output voltage of the final LLC circuit in the prior art, so that the time for obtaining the output voltage of the LLC circuit can be reduced.
In the last embodiment, the process of performing the first stage soft start by the LLC circuit to make the output voltage of the LLC circuit reach the first output voltage value is referred to. In this embodiment, further describing that the LLC circuit includes a transformer, a primary side of the transformer includes a half-bridge circuit and an LC series resonant unit connected in sequence, a secondary side of the transformer includes a second full-bridge circuit, and the LLC circuit is controlled to perform a first-stage soft start so that an output voltage of the LLC circuit reaches a first output voltage value, including:
and controlling a switching tube in the half-bridge circuit and a switching tube in the second full-bridge circuit to work according to a first preset working mode so as to enable the output voltage of the LLC circuit to reach a first output voltage value.
As shown in fig. 6, vbus is a bus voltage at an output end of the PFC circuit, S1 and S2 are two switching tubes in the half-bridge circuit, lr is an inductance in the LC series resonant unit, cr is a capacitance in the LC series resonant unit, T1 is a transformer, lm is an excitation inductance of the transformer T1, N1 is a number of turns of a primary winding of the transformer T1, N2 is a number of turns of a secondary winding of the transformer T1, S3, S4, S5, and S6 are four switching tubes of the second full-bridge circuit, and Vout is an output voltage of the LLC circuit.
Optionally, the switching tubes S1 and S2 in the half-bridge circuit and the switching tubes S3, S4, S5 and S6 in the second full-bridge circuit are controlled to make the switching tubes S1 and S2 in the half-bridge circuit and the switching tubes S3, S4, S5 and S6 in the second full-bridge circuit operate at a constant operating frequency and a second preset duty ratio, so that the output voltage of the LLC circuit reaches a first output voltage valueV out1 . The second preset duty cycle is that of passing throughAnd (5) debugging to obtain the product.
In this embodiment, the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit are controlled to operate according to a first preset operation mode, so that the output voltage of the LLC circuit reaches a first output voltage value. The switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit work according to the first preset working mode, so that the output voltage of the LLC circuit can reach a stable voltage value, and the time required for obtaining the voltage value of the output voltage of the final LLC circuit based on the stable voltage value is shorter than the time required for increasing the output voltage of the LLC circuit from 0 to the voltage value of the output voltage of the final LLC circuit in the prior art, so that the time for obtaining the output voltage of the LLC circuit can be reduced.
In the above embodiment, the process of controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to operate according to the first preset operation mode so as to enable the output voltage of the LLC circuit to reach the first output voltage value is involved. In this embodiment, further describing, controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to operate according to the first preset operation mode includes:
the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit are controlled to operate based on a constant operating frequency and a constant duty cycle.
As shown in fig. 6, vbus is a bus voltage at an output end of the PFC circuit, S1 and S2 are two switching tubes in the half-bridge circuit, lr is an inductance in the LC series resonant unit, cr is a capacitance in the LC series resonant unit, T1 is a transformer, lm is an excitation inductance of the transformer T1, N1 is a number of turns of a primary winding of the transformer T1, N2 is a number of turns of a secondary winding of the transformer T1, S3, S4, S5, and S6 are four switching tubes of the second full-bridge circuit, and Vout is an output voltage of the LLC circuit.
Optionally, the switching tubes S1, S2 in the half-bridge circuit and the switching tubes S3, S4, S5, S6 in the second full-bridge circuit are controlled to make the switching tubes S1, S2 in the half-bridge circuit and the switching tubes S3, S4, S5, S6 in the second full-bridge circuit advance at a constant operating frequency and a constant duty cycle Operating in a row to enable the output voltage of the LLC circuit to reach a first output voltage valueV out1 . The constant duty cycle here is a fixed value obtained by debugging.
In the above embodiment, a process of controlling a switching tube in a half-bridge circuit and a switching tube in a second full-bridge circuit to operate based on a constant operating frequency and a constant duty ratio is involved. In this embodiment, further describing, controlling the PFC circuit and the LLC circuit to perform the second stage soft start synchronously, so that the bus voltage at the output end side of the PFC circuit reaches a second bus voltage value, and the LLC circuit output voltage reaches a second output voltage value, includes:
and controlling the switching tube in the first full-bridge circuit to work, synchronously controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to work according to a second preset working mode, so that the bus voltage at the output end side of the PFC circuit reaches a second bus voltage value, and enabling the output voltage of the LLC circuit to reach a second output voltage value.
The circuit diagram of the PFC circuit with the input end connected to the external power supply and the output end connected to the input end of the LLC circuit is shown in fig. 7, where the power grid 700 is the external power supply, RT1 is a soft start resistor, L1 is a first inductor, rli is a soft start relay, Q1, Q2, Q3, and Q4 are respectively four switching tubes in the first full-bridge circuit, vbus is a bus voltage at the output end side of the PFC circuit, S1 and S2 are two switching tubes in the half-bridge circuit, lr is an inductor in the LC series resonant unit, cr is a capacitor in the LC series resonant unit, T1 is a transformer, lm is an excitation inductance of the transformer T1, N1 is a number of turns of a primary winding of the transformer T1, N2 is a number of turns of a secondary winding of the transformer T1, S3, S4, S5, and S6 are four switching tubes in the second full-bridge circuit, and Vout is an output voltage of the LLC circuit.
Optionally, the switching transistors Q1, Q2, Q3, Q4 in the first full-bridge circuit are controlled to make Q1, Q2, Q3, Q4 operate in a mode of constant operating frequency and a first preset duty cycle, so that the bus voltage at the output end side of the PFC circuit reaches the second bus voltage valueV bus2 Simultaneously, the switching tubes S1 and S2 in the half-bridge circuit and the second full-bridge circuit are synchronously controlledThe switching tubes S3, S4, S5 and S6 in the control circuit work in a mode of constant working frequency and target duty ratio to enable the LLC circuit output voltage to reach a second output voltage valueV out2 . The first preset duty cycle is calculated from the voltage value of the bus voltage at the output end of the PFC circuit and the instantaneous value of the input voltage of the power grid 400.
In this embodiment, the switching tube in the first full-bridge circuit is controlled to work, and the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit are synchronously controlled to work according to a second preset working mode, so that the bus voltage at the output end side of the PFC circuit reaches a second bus voltage value, and the output voltage of the LLC circuit reaches a second output voltage value. The process that the bus voltage at the output end side of the PFC circuit reaches the second bus voltage value and the process that the output voltage of the LLC circuit reaches the second output voltage value are synchronously carried out, and compared with the prior art, the time for enabling the output voltage of the LLC circuit to reach the second output voltage value from 0 is greatly reduced, so that the duration of soft start can be reduced.
In the above embodiment, the process of bringing the bus voltage on the output side of the PFC circuit to the second bus voltage value and bringing the LLC circuit output voltage to the second output voltage value is referred to. In this embodiment, further describing that the switching tube in the synchronous control half-bridge circuit and the switching tube in the second full-bridge circuit operate according to the second preset operation mode, the method includes:
the switching tubes in the half-bridge circuit and the switching tubes in the second full-bridge circuit are synchronously controlled to operate based on a constant operating frequency and a monotonically increasing duty cycle curve.
The circuit diagram of the PFC circuit with the input end connected to the external power supply and the output end connected to the input end of the LLC circuit is shown in fig. 7, where the power grid 400 is the external power supply, RT1 is a soft start resistor, L1 is a first inductor, rli is a soft start relay, Q1, Q2, Q3, and Q4 are respectively four switching tubes in the first full-bridge circuit, vbus is a bus voltage at the output end side of the PFC circuit, S1 and S2 are two switching tubes in the half-bridge circuit, lr is an inductor in the LC series resonant unit, cr is a capacitor in the LC series resonant unit, T1 is a transformer, lm is an excitation inductance of the transformer T1, N1 is a number of turns of a primary winding of the transformer T1, N2 is a number of turns of a secondary winding of the transformer T1, S3, S4, S5, and S6 are four switching tubes in the second full-bridge circuit, and Vout is an output voltage of the LLC circuit.
Alternatively, the switching tubes S1, S2 in the half-bridge circuit and the switching tubes S3, S4, S5, S6 in the second full-bridge circuit are synchronously controlled to operate in a mode of a monotonically increasing duty cycle curve at a constant operating frequency.
In this embodiment, the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit are synchronously controlled to operate based on a constant operating frequency and a monotonically increasing duty cycle curve. The switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit work under a constant working frequency and a monotonically increasing duty ratio curve, so that the process that the output voltage of the LLC circuit reaches a second output voltage value is monotonically increasing, and meanwhile, the PFC circuit and the LLC circuit synchronously perform a second-stage soft start process, and compared with the traditional technology, the time for enabling the output voltage of the LLC circuit to reach the second output voltage value from 0 is greatly reduced, and the duration of soft start can be reduced.
In an exemplary embodiment, a soft start method is provided, which is used in a charging circuit, where the charging circuit includes a PFC circuit and an LLC circuit, an input end of the PFC circuit is connected with an external power supply, an output end of the PFC circuit is connected with an input end of the LLC circuit, the PFC circuit includes a soft start circuit, a first inductor, and a first full-bridge circuit that are sequentially connected, the soft start circuit includes a soft start resistor and a soft start relay that are connected in parallel, the LLC circuit includes a transformer, a primary side of the transformer includes a half-bridge circuit and an LC series resonant unit that are sequentially connected, a secondary side of the transformer includes a second full-bridge circuit, and a flow of the method is shown in fig. 8, and includes:
Step 801, the soft start relay is controlled to be in an off state, so as to form a start-up path composed of an external power supply, a soft start resistor, a first inductor and a first full bridge circuit.
In step 802, a voltage is input to a bus on an output side of the PFC circuit by an external power supply based on a start-up path, so that the bus voltage on the output side of the PFC circuit reaches a first bus voltage value.
And 803, after the bus voltage at the output end side of the PFC circuit reaches a first bus voltage value, controlling the soft start relay to be closed.
Step 804, after the soft start relay is closed, controlling a switching tube in the half-bridge circuit and a switching tube in the second full-bridge circuit to work based on a constant working frequency and a constant duty ratio so as to enable the output voltage of the LLC circuit to reach a first output voltage value; the first output voltage value is determined according to the first bus voltage value, the number of turns of the primary winding of the transformer, the number of turns of the secondary winding of the transformer and a preset gain value.
And step 805, controlling the switching tube in the first full-bridge circuit to work, synchronously controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to work based on a constant working frequency and a monotonically increasing duty ratio curve so as to enable the bus voltage at the output end side of the PFC circuit to reach a second bus voltage value and enable the LLC circuit output voltage to reach a second output voltage value.
When steps 801 to 805 are performed, the operation timing diagrams of the charging circuit are shown in fig. 9, 10, 11, 12, and 13. Wherein, in the period 0-t1, executing step 801 and step 802; in the period t1-t2, executing step 803 and step 804; in period t2-t3, step 805 is performed. Fig. 9 shows a graph of a bus voltage at the output side of the PFC circuit, in which the abscissa indicates time, the ordinate indicates a voltage value of the bus voltage at the output side of the PFC circuit, vbus1 is a first bus voltage value, and Vbus2 is a second bus voltage value. Fig. 10 shows a graph of waveforms of output voltages of an LLC circuit, with the abscissa representing time and the ordinate representing voltage values of the output voltages of the LLC circuit, vout1 being a first output voltage value and Vout2 being a second output voltage value. Fig. 11 shows a waveform diagram of an operating frequency curve of an LLC circuit, with the abscissa representing time and the ordinate representing the operating frequency of the LLC circuit. Fig. 12 shows a schematic diagram of the duty cycle of the switching tubes in the half-bridge circuit in the LLC circuit, with the abscissa representing time and the ordinate representing the magnitude of the duty cycle of the switching tubes in the half-bridge circuit in the LLC circuit. Fig. 13 shows a schematic diagram of the duty cycle of the switching tubes in the second full-bridge circuit in the LLC circuit, with the abscissa representing time and the ordinate representing the magnitude of the duty cycle of the switching tubes in the second full-bridge circuit in the LLC circuit. The data in this exemplary embodiment are shown in table 1.
The data in this exemplary embodiment are shown in table 1.
TABLE 1
In table 1, the bus voltage value is a second bus voltage value corresponding to the bus voltage at the output end side of the PFC circuit, the output voltage value is a second output voltage value corresponding to the output voltage of the LLC circuit, the design gain M is a preset gain, and the gain of the LLC circuit is a ratio of the bus voltage value to the output voltage value. As can be seen from the data in table 1, the LLC circuit maintains a constant gain during the execution of step 805.
In the soft start method, the external power supply inputs the voltage to the bus at the output end side of the PFC circuit, so that the bus at the output end side of the PFC circuit reaches the first bus voltage value, the LLC circuit performs a first stage soft start, so that the output voltage of the LLC circuit reaches the first output voltage value, the PFC circuit and the LLC circuit are controlled to perform a second stage soft start synchronously on the premise that the bus at the output end side of the PFC circuit reaches the first bus voltage value, so that the bus at the output end side of the PFC circuit reaches the second bus voltage value, and the LLC circuit output voltage reaches the second output voltage value, namely, the bus at the output end side of the PFC circuit and the LLC circuit output voltage are synchronously increased in the second stage soft start, in the prior art, the output voltage of the LLC circuit reaches the second bus voltage value, and the soft start time of the LLC circuit is reduced after the voltage at the output end side of the PFC circuit reaches the second bus voltage value, and the second stage soft start time of the LLC circuit is 0.
It should be understood that, although the steps in the flowcharts related to the above embodiments are sequentially shown as indicated by arrows, these steps are not necessarily sequentially performed in the order indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in the flowcharts described in the above embodiments may include a plurality of steps or a plurality of stages, which are not necessarily performed at the same time, but may be performed at different times, and the order of the steps or stages is not necessarily performed sequentially, but may be performed alternately or alternately with at least some of the other steps or stages.
Based on the same inventive concept, the embodiment of the present application further provides a soft start circuit, the structure of which is shown in fig. 14, the soft start circuit includes a controller 1440 and a charging circuit 1420, wherein the charging circuit includes a PFC circuit 1422 and an LLC circuit 1424.
A circuit diagram in which an input terminal of the PFC circuit 1422 is connected to the external power supply 1500 and an output terminal of the PFC circuit 1422 is connected to an input terminal of the LLC circuit 1424 is shown in fig. 15. In fig. 15, an external power supply 1500 is a grid voltage, RT1 is a soft start resistor, L1 is a first inductance, rli is a soft start relay, Q1, Q2, Q3, Q4 are respectively four switching tubes in a first full-bridge circuit, vbus is a bus voltage at an output end side of a PFC circuit, S1, S2 are two switching tubes in a half-bridge circuit, lr is an inductance in an LC series resonance unit, cr is a capacitance in the LC series resonance unit, T1 is a transformer, lm is an excitation inductance of the transformer T1, N1 is a number of turns of a primary winding of the transformer T1, N2 is a number of turns of a secondary winding of the transformer T1, S3, S4, S5, S6 are four switching tubes of a second full-bridge circuit, and Vout is an output voltage of the LLC circuit. Unit1 is a Vbus sampling Unit and is used for detecting bus voltage at the output end side of the PFC circuit; unit2 is a Vout sampling Unit for detecting the output voltage of the LLC circuit.
In one embodiment, the controller is configured to: the external power supply 1500 inputs a voltage to a bus on the output side of the PFC circuit 1422 so that the bus voltage on the output side of the PFC circuit 1422 reaches a first bus voltage value; controlling the LLC circuit 1424 to perform a first stage soft start so that the output voltage of the LLC circuit 1424 reaches a first output voltage value; the PFC circuit 1422 and the LLC circuit 1424 are controlled to perform the second-stage soft start in synchronization, so that the bus voltage on the output side of the PFC circuit 1422 reaches a second bus voltage value, and the LLC circuit output voltage reaches a second output voltage value.
In one embodiment, the controller is configured to: the PFC circuit 1422 and the LLC circuit 1424 are controlled to perform the second-stage soft start in synchronization such that the bus voltage on the output side of the PFC circuit 1422 increases from the first bus voltage value to the second bus voltage value with a first slope, and the LLC circuit 1424 output voltage increases from the first output voltage value to the second output voltage value with a second slope.
In one embodiment, the controller is configured to: and determining a first output voltage value according to the first bus voltage value, the number of turns of the primary winding of the transformer and the number of turns of the secondary winding of the transformer and a preset gain value.
In one embodiment, the PFC circuit 1422 includes a soft start circuit, a first inductor, and a first full bridge circuit connected in sequence, the soft start circuit including a soft start resistor and a soft start relay connected in parallel, and the controller is configured to: the soft start relay is controlled to be in an off state so as to form a starting path consisting of an external power supply 1500, a soft start resistor, a first inductor and a first full-bridge circuit; the external power supply 1500 inputs a voltage to the bus on the output side of the PFC circuit 1422 based on the start-up path, so that the bus voltage on the output side of the PFC circuit 1422 reaches the first bus voltage value.
In one embodiment, the controller is configured to: after the bus voltage at the output end side of the PFC circuit 1422 reaches a first bus voltage value, controlling the soft start relay to be closed; after the soft start relay is closed, the LLC circuit 1424 is controlled to perform a first stage soft start so that the output voltage of the LLC circuit 1424 reaches a first output voltage value.
In one embodiment, the LLC circuit 1424 comprises a transformer, the primary side of which comprises a half-bridge circuit and an LC series resonant unit connected in sequence, and the secondary side of which comprises a second full-bridge circuit, the controller being configured to: the switching tubes in the half-bridge circuit and the switching tubes in the second full-bridge circuit are controlled to operate in a first preset operating mode to enable the output voltage of the LLC circuit 1424 to reach a first output voltage value.
In one embodiment, the controller is configured to: the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit are controlled to operate based on a constant operating frequency and a constant duty cycle.
In one embodiment, the controller is configured to: the switching tube in the first full-bridge circuit is controlled to work, and the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit are synchronously controlled to work according to a second preset working mode, so that the bus voltage at the output end side of the PFC circuit 1422 reaches a second bus voltage value, and the output voltage of the LLC circuit 1424 reaches a second output voltage value.
In one embodiment, the controller is configured to: the switching tubes in the half-bridge circuit and the switching tubes in the second full-bridge circuit are synchronously controlled to operate based on a constant operating frequency and a monotonically increasing duty cycle curve.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of the application should be assessed as that of the appended claims.

Claims (10)

1. The soft start method is characterized by being used in a charging circuit, wherein the charging circuit comprises a PFC circuit and an LLC circuit, an input end of the PFC circuit is connected with an external power supply, and an output end of the PFC circuit is connected with an input end of the LLC circuit, and the method comprises the following steps:
inputting voltage to a bus at the output end side of the PFC circuit through the external power supply so as to enable the bus voltage at the output end side of the PFC circuit to reach a first bus voltage value;
controlling the LLC circuit to perform a first stage soft start so as to enable the output voltage of the LLC circuit to reach a first output voltage value;
and controlling the PFC circuit and the LLC circuit to synchronously perform a second-stage soft start so as to enable the bus voltage at the output end side of the PFC circuit to reach a second bus voltage value and enable the LLC circuit output voltage to reach a second output voltage value.
2. The method of claim 1, wherein the controlling the PFC circuit and the LLC circuit to perform the second stage soft start in synchronization to bring the bus voltage on the output side of the PFC circuit to a second bus voltage value and bring the LLC circuit output voltage to a second output voltage value includes:
And controlling the PFC circuit and the LLC circuit to synchronously perform a second-stage soft start so as to enable the bus voltage at the output end side of the PFC circuit to be increased from the first bus voltage value to the second bus voltage value according to a first slope and enable the LLC circuit output voltage to be increased from the first output voltage value to the second output voltage value according to a second slope.
3. The method of claim 1, wherein the LLC circuit includes a transformer, the first output voltage value being determined based on the first bus voltage value, a number of primary winding turns of the transformer, a number of secondary winding turns of the transformer, and a preset gain value.
4. The method of claim 1, wherein the PFC circuit includes a soft start circuit, a first inductor, and a first full bridge circuit connected in sequence, the soft start circuit including a soft start resistor and a soft start relay connected in parallel, the inputting a voltage to a bus on an output side of the PFC circuit by the external power supply to bring the bus voltage on the output side of the PFC circuit to a first bus voltage value, comprising:
controlling the soft start relay to be in an off state so as to form a starting path consisting of the external power supply, the soft start resistor, the first inductor and the first full-bridge circuit;
And inputting voltage to a bus at the output end side of the PFC circuit by the external power supply based on the starting path so as to enable the bus voltage at the output end side of the PFC circuit to reach the first bus voltage value.
5. The method of claim 4, wherein the controlling the LLC circuit to perform a first stage soft start to bring the output voltage of the LLC circuit to a first output voltage value comprises:
after the bus voltage at the output end side of the PFC circuit reaches the first bus voltage value, controlling the soft start relay to be closed;
and after the soft start relay is closed, controlling the LLC circuit to perform a first stage soft start so as to enable the output voltage of the LLC circuit to reach the first output voltage value.
6. The method of claim 5, wherein the LLC circuit includes a transformer, a primary side of the transformer including a half-bridge circuit and an LC series resonant unit connected in sequence, a secondary side of the transformer including a second full-bridge circuit, the controlling the LLC circuit for a first stage soft start to bring an output voltage of the LLC circuit to the first output voltage value, comprising:
And controlling a switching tube in the half-bridge circuit and a switching tube in the second full-bridge circuit to work according to a first preset working mode so as to enable the output voltage of the LLC circuit to reach the first output voltage value.
7. The method of claim 6, wherein controlling the switching tubes in the half-bridge circuit and the switching tubes in the second full-bridge circuit to operate in a first predetermined mode of operation comprises:
and controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to operate based on a constant operating frequency and a constant duty cycle.
8. The method of claim 6, wherein the controlling the PFC circuit and the LLC circuit to perform the second stage soft start in synchronization to bring the bus voltage on the output side of the PFC circuit to a second bus voltage value and bring the LLC circuit output voltage to a second output voltage value, comprises:
and controlling the switching tube in the first full-bridge circuit to work, synchronously controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to work according to a second preset working mode, so that the bus voltage at the output end side of the PFC circuit reaches the second bus voltage value, and the LLC circuit output voltage reaches the second output voltage value.
9. The method of claim 8, wherein said synchronously controlling the switching tubes in the half-bridge circuit and the switching tubes in the second full-bridge circuit operates in a second predetermined operating mode, comprising:
and synchronously controlling the switching tube in the half-bridge circuit and the switching tube in the second full-bridge circuit to work based on a constant working frequency and a monotonically increasing duty ratio curve.
10. The soft start circuit is characterized by comprising a controller and a charging circuit, wherein the charging circuit comprises a PFC circuit and an LLC circuit, the input end of the PFC circuit is connected with an external power supply, and the output end of the PFC circuit is connected with the input end of the LLC circuit;
the controller is configured to perform the soft start method of any one of claims 1 to 9.
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