CN116780910A - Test power supply circuit and control method - Google Patents

Test power supply circuit and control method Download PDF

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Publication number
CN116780910A
CN116780910A CN202311058282.6A CN202311058282A CN116780910A CN 116780910 A CN116780910 A CN 116780910A CN 202311058282 A CN202311058282 A CN 202311058282A CN 116780910 A CN116780910 A CN 116780910A
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CN
China
Prior art keywords
power supply
supply circuit
llc
circuit
voltage
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Granted
Application number
CN202311058282.6A
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Chinese (zh)
Other versions
CN116780910B (en
Inventor
吴云
陶磊
胡勇
檀贵友
张�杰
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Hefei Blue Dot Digital Power Supply Co ltd
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Hefei Blue Dot Digital Power Supply Co ltd
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Priority to CN202311058282.6A priority Critical patent/CN116780910B/en
Publication of CN116780910A publication Critical patent/CN116780910A/en
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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
    • 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
    • H02M3/33507—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 with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—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 with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
    • G01R1/28—Provision in measuring instruments for reference values, e.g. standard voltage, standard waveform
    • 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
    • H02M1/0048—Circuits or arrangements for reducing losses
    • 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
    • H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
    • H02M1/007—Plural converter units in cascade
    • 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
    • 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 discloses a test power supply circuit and a control method, and belongs to the technical field of power supplies. The power supply circuit comprises a power factor correction circuit and an LLC isolation switch power supply circuit which are connected in cascade, and the control method comprises the following steps: giving a target voltage output by an LLC isolation switch power supply circuit; when the target voltage is in a reference output voltage range, taking the product of the target voltage and the turn ratio of the transformer of the LLC isolating switch power supply circuit as bus voltage, wherein the reference output voltage range is the output voltage range of the LLC isolating switch power supply circuit in a state that the conversion ratio is 1; controlling a power factor correction circuit to output bus voltage to an LLC isolation switch power supply circuit; the LLC isolation switching power supply circuit is controlled to operate in a state with a conversion ratio of 1. By arranging the power factor correction circuit and the LLC isolation switch power supply circuit and controlling the LLC isolation switch power supply circuit to operate at a high conversion rate, the power loss is reduced, and the conversion efficiency is improved.

Description

Test power supply circuit and control method
Technical Field
The application belongs to the technical field of power supplies, and particularly relates to a test power supply circuit and a control method.
Background
The grid-connected power generation of the photovoltaic inverter is an important green energy source. Along with the annual growth of the photovoltaic power generation of China, the demand of the matched photovoltaic inverter test equipment is also increasing.
At present, a three-level high-frequency isolation scheme is generally adopted in a direct-current test power supply, the voltage of a power grid is rectified to be rectified through an AC/DC module, then the isolation DC/DC module is used for electrical isolation, and finally the output voltage (input voltage of a photovoltaic inverter) of the test power supply is subjected to step-down adjustment through a non-isolation DC/DC power supply module, so that required test voltage and power are obtained. But such dc test power supplies are less system efficient.
Disclosure of Invention
The present application aims to solve at least one of the technical problems existing in the prior art. Therefore, the application provides a test power supply circuit and a control method, which have higher conversion efficiency.
In a first aspect, the present application provides a control method of a power supply circuit, the power supply circuit including a cascaded power factor correction circuit and an LLC isolated switching power supply circuit, the control method comprising:
giving a target voltage output by an LLC isolation switch power supply circuit;
when the target voltage is in a reference output voltage range, taking the product of the target voltage and the turn ratio of the transformer of the LLC isolating switch power supply circuit as bus voltage, wherein the reference output voltage range is the output voltage range of the LLC isolating switch power supply circuit in a state that the conversion ratio is 1;
controlling a power factor correction circuit to output bus voltage to an LLC isolation switch power supply circuit;
the LLC isolation switching power supply circuit is controlled to operate in a state with a conversion ratio of 1.
According to the control method of the test power supply circuit, the power factor correction circuit and the LLC isolation switch power supply circuit are controlled according to the required voltage, and the LLC isolation switch power supply circuit is controlled to operate at a high conversion rate, so that the power loss is reduced, and the conversion efficiency is improved.
According to one embodiment of the application, controlling an LLC isolation switching power supply circuit to operate in a state with a conversion ratio of 1 includes:
the LLC isolation switching power supply circuit is controlled to constantly operate at a switching frequency equal to the self-resonance frequency.
According to one embodiment of the application, controlling an LLC isolated switching power supply circuit to operate constantly at a switching frequency equal to its own resonant frequency comprises:
taking the target voltage as a first given voltage;
determining a first target current according to a first given voltage and an output sampling voltage of the LLC isolation switch power supply circuit;
generating a first PWM signal according to the first target current and the output sampling current of the LLC isolation switch power supply circuit, wherein the switching frequency corresponding to the first PWM signal is equal to the resonant frequency of the LLC isolation switch power supply circuit;
and controlling the LLC isolating switch power supply circuit by using the first PWM signal.
According to one embodiment of the present application, given the target voltage output by the LLC isolated switching power supply circuit, further comprising:
when the target voltage is out of the reference output voltage range, the LLC isolation switch power supply circuit is controlled to operate at a variable switching frequency, and the conversion ratio of the LLC isolation switch power supply circuit is more than or less than 1.
According to one embodiment of the application, when the target voltage is outside the reference output voltage range, controlling the LLC isolation switching power supply circuit to operate at a variable switching frequency, the conversion ratio of the LLC isolation switching power supply circuit being greater than or less than 1, comprises:
when the target voltage is larger than the maximum value of the reference output voltage range, taking the maximum output voltage of the power factor correction circuit as the bus voltage;
controlling a power factor correction circuit to output bus voltage to an LLC isolation switch power supply circuit;
and controlling the LLC isolation switching power supply circuit to operate at a variable switching frequency, wherein the conversion ratio of the LLC isolation switching power supply circuit is greater than 1.
According to one embodiment of the application, when the target voltage is outside the reference output voltage range, controlling the LLC isolation switching power supply circuit to operate at a variable switching frequency, the conversion ratio of the LLC isolation switching power supply circuit being greater than or less than 1, comprises:
when the target voltage is smaller than the minimum value of the reference output voltage range, taking the minimum output voltage of the power factor correction circuit as the bus voltage;
controlling a power factor correction circuit to output bus voltage to an LLC isolation switch power supply circuit;
and controlling the LLC isolation switching power supply circuit to operate at a variable switching frequency, wherein the conversion ratio of the LLC isolation switching power supply circuit is smaller than 1.
According to one embodiment of the application, controlling a power factor correction circuit to output a bus voltage to an LLC isolated switching power supply circuit includes:
taking the bus voltage as a second given voltage;
determining a second target current according to a second given voltage and an output sampling voltage of the power factor correction circuit;
generating a second PWM signal according to the second target current and the output sampling current of the power factor correction circuit;
and controlling the LLC isolating switch power supply circuit by using the second PWM signal.
In a second aspect, the present application also provides a test power supply circuit, comprising:
the power factor correction circuit is configured to be connected with an alternating current power supply, and is used for carrying out power correction and rectification on the alternating current power supply so as to output bus voltage;
an LLC isolation switch power supply circuit coupled with the power factor correction circuit, the LLC isolation switch power supply circuit configured with an LLC topology structure and outputting a target voltage by performing voltage conversion on a bus voltage;
and a control circuit coupled to the power factor correction circuit and the LLC isolation switching power supply circuit, respectively, and configured to control the power factor correction circuit to adjust a bus voltage equal to a product of a transformer turn ratio of the LLC isolation switching power supply circuit and a target voltage, and to control the LLC isolation switching power supply circuit to operate in a state in which a conversion ratio is 1.
According to the test power supply circuit, the power factor correction circuit and the LLC isolation switch power supply circuit are arranged, so that the power loss is reduced, and the LLC isolation switch power supply circuit is controlled to operate at a high conversion rate, and the conversion efficiency is improved; meanwhile, compared with the structure requiring the adoption of the isolated DC/DC and the non-isolated DC/DC in the related technology, the non-isolated DC/DC is removed, the circuit size is reduced, and the weight is also reduced.
According to one embodiment of the application, the control circuit is further configured to adjust the bus voltage to be equal to a maximum output voltage of the power factor correction circuit and to control the conversion ratio of the LLC isolated switching power supply circuit to be greater than 1.
According to one embodiment of the application, the control circuit is further configured to adjust the bus voltage to be equal to a minimum output voltage of the power factor correction circuit and to control the conversion ratio of the LLC isolated switching power supply circuit to be less than 1.
According to one embodiment of the application, the LLC isolation switching power supply circuit is configured with a three-phase LLC interleaved topology.
According to one embodiment of the application, an input of the power factor correction circuit is used for connecting to a power grid, and an output of the LLC isolation switching power supply circuit is used for connecting to an inverter.
Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.
Drawings
The foregoing and/or additional aspects and advantages of the application will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic diagram of a test power circuit according to an embodiment of the present application;
FIG. 2 is a schematic diagram of the output of an LLC isolation switching power supply circuit provided by an embodiment of the application;
FIG. 3 is a schematic diagram of an LLC isolation switch power supply circuit according to an embodiment of the present application;
FIG. 4 is a flow chart of a control method of a test power supply circuit according to an embodiment of the present application;
fig. 5 is a control logic diagram of a test power supply circuit according to an embodiment of the present application.
Reference numerals:
the test power supply circuit 100, the power factor correction circuit 110, the LLC isolation switch power supply circuit 120, the primary side conversion circuit 121, the LLC resonant transformer circuit 122, the secondary side rectification output circuit 123, the control circuit 130 and the inverter 200.
Detailed Description
Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the application.
In the following description, "circuit" refers to an electrically conductive loop formed by at least one element or sub-circuit through electrical or electromagnetic connection. When an element or circuit is referred to as being "coupled to" or "connected to" another element or an element/circuit is "coupled to" or "connected between" two nodes, it can be directly coupled or connected to the other element or intervening elements may be present and the connection between the elements may be physical, logical, or a combination thereof. In contrast, when an element is referred to as being "directly coupled to" or "directly connected to" another element, it means that there are no intervening elements present between the two.
In the description, the terms "first," "second," and the like are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the numerical descriptors used herein are interchangeable under appropriate circumstances such that embodiments of the application are capable of operation in sequences other than those illustrated or otherwise described herein, and that the objects identified by "first," "second," etc. are generally of a type and do not limit the number of objects, for example, the first object can be one or more. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.
Furthermore, the description of the terms "one embodiment," "some embodiments," "an exemplary embodiment," "an example," "a particular example," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Referring to fig. 1, one embodiment of the present application provides a test power supply circuit 100. In the present embodiment, the test power supply circuit 100 includes a power factor correction circuit 110, an LLC isolated switching power supply circuit 120, and a control circuit 130, the power factor correction circuit 110 being configured to access an ac power supply, and to power correct and rectify the ac power supply to output a bus voltage; the LLC isolated switching power supply circuit 120 is coupled with the power factor correction circuit 110, the LLC isolated switching power supply circuit 120 is configured with an LLC topology, and outputs a target voltage by voltage converting the bus voltage; the control circuit 130 is coupled to the PFC circuit 110 and the LLC isolation switching power supply circuit 120, respectively, and is configured to control the PFC circuit 110 to regulate the bus voltage to be equal to the product of the transformer turn ratios of the LLC isolation switching power supply circuit for the target voltage, and to control the LLC isolation switching power supply circuit 120 to operate in a state with a conversion ratio of 1.
In the present embodiment, the input terminal of the pfc circuit 110 is used as the input terminal of the test power supply circuit 100 to be connected to an ac power supply, and the output terminal of the LLC isolated switching power supply circuit 120 is used as the output terminal of the test power supply circuit 100 to output a dc power supply.
In some embodiments, test power circuit 100 may be used to test inverter 200. The input of the power factor correction circuit 110 is used to connect to the grid, wherein A, B, C represents the three-phase line of the incoming line. An output of the LLC isolated switching power supply circuit 120 is connected to the inverter 200. The dc side of the inverter 200 is coupled to the output of the LLC isolated switching power supply circuit 120 and the ac side of the inverter 200 is coupled to the grid, wherein U, V, W represents the output three-phase hot.
The test power supply circuit 100 can test the performance of the inverter 200 under different voltage environments by adjusting the voltage of the dc power supply output to the inverter 200. For a specific testing process of the inverter 200, a mature technology is already available, and this embodiment is not described herein.
Of course, the test power circuit 100 may also provide power to other dc input devices, which is not limited in this embodiment.
In some embodiments, the power factor correction (PFC, power Factor Correction) circuit 110 may be an active power factor correction circuit. The active power factor correction circuit may include a three-phase rectification circuit, a direct current capacitor, and a control device; the control device may be a switching transistor, such as a MOS (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor ). The specific circuit structure of the pfc circuit 110 is well known, and the present embodiment is not described herein.
It will be appreciated that the pfc circuit 110 may be used to improve the power factor of the power supply to increase the energy utilization efficiency and reduce the energy consumption, thereby improving the conversion efficiency of the test power supply circuit 100.
It should be noted that, the LLC isolated switching power supply circuit 120 may use a transformer to implement voltage conversion and isolation between the input power supply and the output power supply. The primary side of the transformer may be connected to a power supply through a switch tube. The switching tube can also be a MOS tube or an IGBT tube. The LLC topology is a resonant circuit structure comprising two inductors and one capacitor. The LLC topological structure is connected between the switching tube and the primary winding of the transformer, and the LLC topological structure can realize soft switching of the switching tube through resonance, so that the switching loss is reduced, and the switching efficiency is higher.
In the present embodiment, the control circuit 130 adjusts the bus voltage to be equal to the product of the target voltage and the transformer turn ratio of the LLC isolated switching power supply circuit 120, and controls the conversion ratio of the LLC isolated switching power supply circuit 120 to be 1.
Note that, the conversion m=v2×n/V1 of the LLC isolated switching power supply circuit 120, where V1 is a bus voltage, V2 is a target voltage, and N is a transformer turn ratio of the LLC isolated switching power supply circuit 120.
The control circuit 130 may control the LLC isolation switching power supply circuit 120 to operate at a first switching frequency equal to a resonant frequency of the LLC isolation switching power supply circuit 120. When the LLC isolation switch power supply circuit 120 works at the conversion ratio of 1, the maximum conversion efficiency can be realized by adopting fixed frequency control, and the loss is reduced.
Referring to fig. 2, the llc isolated switching power supply circuit 120 operates in an output voltage range when the conversion ratio is 1 to a normal output voltage range. The LLC isolation switching power supply circuit 120 may also provide a target voltage that is greater than or less than the constant output voltage range to widen the output range.
According to the test power supply circuit 100 of the present application, by providing the power factor correction circuit 110 and the LLC isolated switching power supply circuit 120, and controlling the LLC isolated switching power supply circuit to operate at a high conversion rate, power loss is reduced, thereby improving conversion efficiency; meanwhile, compared with the structure requiring the adoption of the isolated DC/DC and the non-isolated DC/DC in the related technology, the non-isolated DC/DC is removed, the circuit size is reduced, and the weight is also reduced.
Referring to FIG. 3, in some embodiments, the LLC isolated switching power supply circuit 120 includes a primary side conversion circuit 121, an LLC resonant transformer circuit 122, and a secondary side rectifying output circuit 123 coupled in sequence. The primary side conversion circuit 121 is coupled to the dc bus to convert dc power on the dc bus to ac power. The dc bus is coupled to an output terminal of the pfc circuit 110. The LLC resonant transformer circuit 122 includes an LLC resonant circuit and a transformer, and the ac power supplied from the primary side converter circuit 121 is transmitted to the primary side winding of the transformer via the LLC resonant circuit. The secondary rectifying output circuit 123 is coupled to the secondary winding of the transformer, rectifies and outputs the ac power output from the secondary winding.
In some embodiments, the LLC isolation switching power supply circuit 120 is configured with a three-phase LLC interleaved topology.
In this embodiment, the three-phase LLC interleaved topology may include three topologies as shown in fig. 2. The input ends of the three-way LLC topological structure are all connected to the same direct current bus, and the output ends of the three-way LLC topological structure are all connected to the same direct current bus.
It should be noted that, the phase difference between the driving signal waveforms of the three-way LLC topology structure may be 120 degrees, so as to implement staggered output of the three-way LLC topology structure, so that the output ripple of the LLC isolated switching power supply circuit 120 may be further reduced, and the conversion efficiency may be improved.
In this embodiment, the control circuit 300 may be coupled to the control ends of the switching transistors (such as the gates of the MOS transistors or the gates of the IGBTs) in the pfc circuit 110 and the LLC isolated switching power supply circuit 120, respectively. The control circuit 300 controls the switching tubes to be periodically turned on or off by transmitting a control signal to the control terminals of the switching tubes. The control signal may be a PWM (Pulse width modulation wave, pulse width modulation) signal, among others.
In some embodiments, the test power supply circuit 100 may be applied in a test power supply apparatus, which may include a plurality of test power supply circuits 100. For example, the power of the test power supply circuit 100 may be 30KW, the test power supply apparatus may include 4 test power supply circuits 100, and the power may reach 120KW. Assuming that each test power supply circuit 100 improves the conversion efficiency by 3%, the loss of each test power supply circuit 100 is reduced by 900W, and the loss of the test power supply device is reduced by 3.6KW.
It is noted that the test power supply device is operated with the lost electrical energy converted to thermal energy. Therefore, in the related art, since the circuit loss is large, it is also necessary to configure a high-speed fan to perform heat dissipation, resulting in a large noise. The test power supply equipment can use a low-speed low-noise fan due to the reduction of loss, so that the noise is reduced to 58dB, which is lower than 60dB of the industry standard.
In some embodiments, the control circuit 130 is further configured to regulate the bus voltage to be equal to the maximum output voltage of the power factor correction circuit 110, and to control the conversion ratio of the LLC isolated switching power supply circuit 130 to be greater than 1.
The LLC isolation switching power supply circuit 120 may also provide a target voltage that is greater than the normal output voltage range to widen the output range. The control circuit 130 may control the LLC isolated switching power supply circuit 120 to operate at a variable switching frequency, and may increase a conversion ratio of the LLC isolated switching power supply circuit 120 by using variable frequency control, thereby increasing an output target voltage.
In some embodiments, the control circuit 130 is further configured to regulate the bus voltage to be equal to the minimum output voltage of the PFC circuit 110, and to control the conversion ratio of the LLC isolated switching power supply circuit 120 to be less than 1.
The LLC isolation switching power supply circuit 120 may also provide a target voltage that is greater than the normal output voltage range to widen the output range. The control circuit 130 may control the LLC isolated switching power supply circuit 120 to operate at a variable switching frequency, and may reduce a conversion ratio of the LLC isolated switching power supply circuit 120 by adopting variable frequency control, thereby reducing an output target voltage.
Referring to fig. 4, an embodiment of the present application also provides a control method of the test power supply circuit 100. In this embodiment, the present application is not limited to this embodiment. The control method is used for controlling the test power supply circuit according to the above, and comprises the following steps:
step 10, giving a target voltage output by the LLC isolation switch power supply circuit 120;
step 20, when the target voltage is within a reference output voltage range, taking the product of the target voltage and the turn ratio of the transformer of the LLC isolation switch power supply circuit 120 as a bus voltage, wherein the reference output voltage range is the output voltage range of the LLC isolation switch power supply circuit 120 in a state that the conversion ratio is 1;
step 30, controlling the power factor correction circuit 110 to output bus voltage to the LLC isolation switch power supply circuit 120;
step 40, control LLC isolation switching power supply circuit 120 operates in a state with a conversion ratio of 1.
It should be noted that, the execution body of the control method of the test power supply circuit in this embodiment may be the control circuit 130 of the test power supply circuit 100 proposed in the foregoing embodiment. The specific circuit structure of the test power supply circuit 100 can be referred to the foregoing, and the description of this embodiment is omitted herein.
In some embodiments, the control circuit 130 may receive a test voltage (indicative of the voltage required to be output by the test power supply circuit 100) input by a tester, and determine the test voltage as the target voltage output by the LLC isolation switch power supply circuit 120. Alternatively, the control circuit 130 may calculate based on the current operating state according to an operating control strategy, and thereby determine the target voltage output by the LLC isolation switching power supply circuit 120.
It will be appreciated that the bus voltage output by the pfc circuit 110 is used as an input to the LLC isolated switching power supply circuit 120, and that to determine the control mode of the LLC isolated switching power supply circuit 120, it is also necessary to determine the input voltage (i.e., the bus voltage) thereof.
In some embodiments, the control circuit 130 may determine the bus voltage corresponding to the target voltage value based on a relationship between conversion efficiency and conversion ratio of the LLC isolated switching power supply circuit 120. Wherein the relationship between conversion efficiency and conversion ratio includes conversion ratio between bus voltage and target voltage at different conversion efficiencies. Therefore, the conversion ratio can be determined according to the conversion efficiency, or the conversion ratio can be directly selected, and then the product operation is carried out on the conversion ratio and the target voltage to determine the corresponding target voltage.
With continued reference to fig. 2, the reference output voltage range refers to the output voltage range in which the LLC isolated switching power supply circuit 120 operates at a conversion ratio of 1. When the target voltage is within the reference output voltage range, the highest conversion efficiency of the LLC isolated switching power supply circuit 120 occurs with a conversion ratio of 1, so controlling the conversion ratio to be 1 can effectively improve the conversion efficiency of the LLC isolated switching power supply circuit 120.
According to the foregoing, the conversion m=v2×n/V1 of the LLC isolated switching power supply circuit 120, and therefore the bus voltage value v1=v2×n when the conversion ratio is 1. The LLC isolated switching power supply circuit 120 thus operates in a state where the conversion ratio is 1, and can supply a target voltage.
According to the control method of the test power supply circuit of the present application, the conversion efficiency is improved by controlling the power factor correction circuit 110 and the LLC isolated switching power supply circuit 120 according to a desired voltage, and controlling the LLC isolated switching power supply circuit 120 to operate at a high conversion rate, reducing power loss.
In some embodiments, step 40 may include: the LLC isolation switching power supply circuit 120 is controlled to constantly operate at a switching frequency equal to the self resonant frequency.
The resonant frequency refers to the resonant frequency of the LLC resonant transformer circuit 122 in the control LLC isolated switching power supply circuit 120, and the switching frequency refers to the switching frequency of the primary side conversion circuit 121. Controlling the LLC isolation switching power supply circuit 120 at a switching frequency equal to its resonant frequency allows the LLC isolation switching power supply circuit 120 to operate with a conversion ratio of 1. In this case, the LLC isolated switching power supply circuit 120 is controlled at a constant frequency.
In this embodiment, the control circuit 130 also needs to control the pfc circuit 110 to operate at the corresponding switching frequency to output the voltage with the phase bus. The specific switching frequency is determined according to the specific structure of the circuit and the voltage value of the power supply, which is not limited in this embodiment.
In some embodiments, step 10 further comprises, after: when the target voltage is outside the reference output voltage range, the LLC isolation switching power supply circuit 120 is controlled to operate at a variable switching frequency, and the conversion ratio of the LLC isolation switching power supply circuit 120 is greater than or less than 1.
With continued reference to fig. 2, the LLC isolated switching power supply circuit 120 in this embodiment can also widen the output voltage range at the expense of efficiency. The LLC isolation switching power supply circuit 120 may also operate in a state where the conversion ratio is greater than 1 or less than 1 to boost or reduce the output target voltage.
In some embodiments, when the target voltage is greater than the maximum value of the reference output voltage range, the maximum output voltage of the power factor correction circuit 110 is taken as the bus voltage; controlling the power factor correction circuit 110 to output bus voltage to the LLC isolation switch power supply circuit; the LLC isolated switching power supply circuit 120 is controlled to operate at a varying switching frequency, and the conversion ratio of the LLC isolated switching power supply circuit 120 is greater than 1.
In the present embodiment, the control circuit 130 controls the power factor correction circuit 110 to output at the maximum output voltage, and controls the LLC isolated switching power supply circuit 120 to operate in the variable frequency mode such that the conversion ratio of the LLC isolated switching power supply circuit 120 is greater than 1, thereby making the voltage output by the LLC isolated switching power supply circuit 120 greater than the maximum value of the reference output voltage range. The output voltage of the pfc circuit 110 may be raised to reduce the switching pressure of the LLC isolated switching power supply circuit 120 to some extent.
In some embodiments, when the target voltage is less than the minimum value of the reference output voltage range, the minimum output voltage of the pfc circuit 110 is taken as the bus voltage; controlling the power factor correction circuit 110 to output the bus voltage to the LLC isolated switching power supply circuit 120; the LLC isolation switching power supply circuit 120 is controlled to operate at a varying switching frequency, and the conversion ratio of the LLC isolation switching power supply circuit 120 is less than 1.
In the present embodiment, the control circuit 130 controls the pfc circuit 110 to output at the minimum output voltage, and controls the LLC isolated switching power supply circuit 120 to operate in the variable frequency mode such that the conversion ratio of the LLC isolated switching power supply circuit 120 is less than 1, thereby making the voltage output by the LLC isolated switching power supply circuit 120 less than the minimum value of the reference output voltage range. Wherein, reducing the output voltage of the PFC circuit 110 can reduce the switching pressure of the LLC isolation switching power supply circuit 120 to some extent.
Referring to fig. 5, in some embodiments, both the pfc circuit 110 and the LLC isolated switching power supply circuit 120 employ a dual closed loop control strategy with the current loop as the inner loop and the voltage loop as the outer loop.
In the present embodiment, v2_ref is a target voltage output from the LLC isolated switching power supply circuit 120. In the closed-loop control of the LLC isolated switching power supply circuit 120, the difference between the v2_ref and the output sampling voltage V2 of the LLC isolated switching power supply circuit 120 is input to the LLC voltage loop PI unit, yielding an output first target circuit i2_ref; the difference between i2_ref and the output sampling current I2 of the LLC isolated switching power supply circuit 120 is input to the LLC current loop PI unit, resulting in a first PWM signal, which is used to drive the LLC isolated switching power supply circuit 120.
When the LLC isolated switching power supply circuit 120 is operated in a state in which the conversion ratio is 1, the switching frequency corresponding to the first PWM signal is equal to the resonant frequency of the LLC isolated switching power supply circuit 120.
In the closed-loop control of the power factor correction circuit 110, the LLC compensation module determines an output given bus voltage v1_ref of the power factor correction circuit 110 based on v2_ref; the difference between v1_ref and the output sampling voltage V1 of the PFC circuit 110 is input to the PFC voltage loop PI unit to obtain a second target current i1_ref; the difference between i1_ref and the output sampling current I1 of the power factor correction circuit 110 is input to the PFC current loop PI unit, resulting in a second PWM signal, which is used to drive the power factor correction circuit 110.
While embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the application, the scope of which is defined by the claims and their equivalents.

Claims (12)

1. A control method of a power supply circuit, the power supply circuit comprising a cascaded power factor correction circuit and an LLC isolated switching power supply circuit, the control method comprising:
giving a target voltage output by the LLC isolation switch power supply circuit;
when the target voltage is in a reference output voltage range, taking the product of the target voltage and the turn ratio of a transformer of the LLC isolating switch power supply circuit as a bus voltage, wherein the reference output voltage range is an output voltage range of the LLC isolating switch power supply circuit in a state that the conversion ratio is 1;
controlling the power factor correction circuit to output the bus voltage to the LLC isolating switch power supply circuit;
and controlling the LLC isolation switching power supply circuit to operate in a state with a conversion ratio of 1.
2. The control method according to claim 1, characterized in that the controlling the LLC isolated switching power supply circuit to operate in a state where a conversion ratio is 1, includes:
the LLC isolation switching power supply circuit is controlled to constantly operate at a switching frequency equal to the self resonant frequency.
3. The control method according to claim 2, characterized in that the controlling the LLC isolated switching power supply circuit to constantly operate at a switching frequency equal to a self resonant frequency, comprises:
taking the target voltage as a first given voltage;
determining a first target current according to the first given voltage and an output sampling voltage of the LLC isolation switch power supply circuit;
generating a first PWM signal according to the first target current and the output sampling current of the LLC isolation switch power supply circuit, wherein the switching frequency corresponding to the first PWM signal is equal to the resonant frequency of the LLC isolation switch power supply circuit;
and controlling the LLC isolating switch power supply circuit by using the first PWM signal.
4. A control method according to any one of claims 1-3, characterized in that after said given target voltage output by the LLC isolated switching power supply circuit, further comprises:
and when the target voltage is out of the reference output voltage range, controlling the LLC isolating switch power supply circuit to operate at a variable switching frequency, wherein the conversion ratio of the LLC isolating switch power supply circuit is more than or less than 1.
5. The control method according to claim 4, wherein the controlling the LLC isolated switching power supply circuit to operate at a variable switching frequency when the target voltage is outside a reference output voltage range, the LLC isolated switching power supply circuit having a conversion ratio greater than or less than 1, comprises:
when the target voltage is larger than the maximum value of the reference output voltage range, taking the maximum output voltage of the power factor correction circuit as a bus voltage;
controlling the power factor correction circuit to output the bus voltage to the LLC isolating switch power supply circuit;
and controlling the LLC isolation switching power supply circuit to operate at a variable switching frequency, wherein the conversion ratio of the LLC isolation switching power supply circuit is greater than 1.
6. The control method according to claim 4, wherein the controlling the LLC isolated switching power supply circuit to operate at a variable switching frequency when the target voltage is outside a reference output voltage range, the LLC isolated switching power supply circuit having a conversion ratio greater than or less than 1, comprises:
when the target voltage is smaller than the minimum value of the reference output voltage range, taking the minimum output voltage of the power factor correction circuit as a bus voltage;
controlling the power factor correction circuit to output the bus voltage to the LLC isolating switch power supply circuit;
and controlling the LLC isolation switching power supply circuit to operate at a variable switching frequency, wherein the conversion ratio of the LLC isolation switching power supply circuit is smaller than 1.
7. A control method according to any one of claims 1-3, wherein said controlling the power factor correction circuit to output the bus voltage to the LLC isolated switching power supply circuit comprises:
taking the bus voltage as a second given voltage;
determining a second target current according to the second given voltage and an output sampling voltage of the power factor correction circuit;
generating a second PWM signal according to the second target current and the output sampling current of the power factor correction circuit;
and controlling the LLC isolating switch power supply circuit by using the second PWM signal.
8. A test power supply circuit, comprising:
the power factor correction circuit is configured to be connected with an alternating current power supply, and is used for carrying out power correction and rectification on the alternating current power supply so as to output bus voltage;
an LLC isolation switching power supply circuit coupled with the power factor correction circuit, the LLC isolation switching power supply circuit configured with an LLC topology and outputting a target voltage by voltage converting the bus voltage;
and a control circuit coupled to the power factor correction circuit and the LLC isolation switching power supply circuit, respectively, and configured to control the power factor correction circuit to adjust the bus voltage to be equal to the target voltage by the product of the transformer turn ratios of the LLC isolation switching power supply circuit, and to control the LLC isolation switching power supply circuit to operate in a state where the conversion ratio is 1.
9. The test power supply circuit of claim 8, wherein the control circuit is further configured to adjust the bus voltage to be equal to a maximum output voltage of the power factor correction circuit and to control a conversion ratio of the LLC isolated switching power supply circuit to be greater than 1.
10. The test power supply circuit of claim 8, wherein the control circuit is further configured to adjust the bus voltage to be equal to a minimum output voltage of the power factor correction circuit and to control a conversion ratio of the LLC isolated switching power supply circuit to be less than 1.
11. Test power supply circuit according to any of claims 8-10, characterized in that the LLC isolated switching power supply circuit is configured with a three-phase LLC interleaved topology.
12. Test power supply circuit according to any of claims 8-10, characterized in that the input of the power factor correction circuit is for connection to a power grid and the output of the LLC isolated switching power supply circuit is for connection to an inverter.
CN202311058282.6A 2023-08-22 2023-08-22 Test power supply circuit and control method Active CN116780910B (en)

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