CN112134463B - Full-bridge LLC resonant converter and resonant current detection method thereof - Google Patents

Full-bridge LLC resonant converter and resonant current detection method thereof Download PDF

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Publication number
CN112134463B
CN112134463B CN202010895001.2A CN202010895001A CN112134463B CN 112134463 B CN112134463 B CN 112134463B CN 202010895001 A CN202010895001 A CN 202010895001A CN 112134463 B CN112134463 B CN 112134463B
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capacitor
resistor
bridge
resonant
diode
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CN112134463A (en
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李锐
程志杰
王金鑫
许双全
卢继东
刘宏森
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Hangzhou Zhonhen Electric Co ltd
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Hangzhou Zhonhen Electric Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—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
    • H02M3/3353—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 at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/1213—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for DC-DC converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a full-bridge LLC resonant converter, which relates to the technical field of power electronics and comprises a full-bridge rectifying circuit, a resonant circuit, a detection circuit and a secondary side circuit; the resonant circuit comprises a first inductor, a second inductor, a resonant capacitor and a transformer bank, wherein the resonant capacitor is provided with a first end and a second end, and the first end and the second end have the same potential value and opposite directions; the detection circuit comprises a first resistor and a first capacitor, the first resistor and the first capacitor are connected in series, one end, far away from the first resistor, of the first capacitor is connected to any one end of the resonant capacitor, one end, far away from the first capacitor, of the first resistor is grounded, and the ratio of the voltage value at the two ends of the first capacitor to the voltage value at the two ends of the first resistor is larger than 50, so that the resonant current value and the voltage value at the two ends of the first resistor are in a linear relation. The invention replaces a current transformer with the first resistor and the first capacitor to carry out resonance current detection so as to reduce the overall cost.

Description

Full-bridge LLC resonant converter and resonant current detection method thereof
Technical Field
The invention relates to the technical field of power electronics, in particular to a full-bridge LLC resonant converter and a resonant current detection method thereof.
Background
LLC resonant converters are one of the main power stage topologies of led tv, with more advantages compared to other converters, such as: a) operating with zvs (zero voltage switching) conditions throughout the load range to achieve high efficiency; b) the working frequency variation range is narrow, so that the design of a high-frequency transformer and an input filter is facilitated; c) the voltage stress of the switch used on the primary side is clamped to the input voltage, while the voltage across the two diodes on the secondary side is always equal to twice the output voltage of the center-tapped transformer.
This LLC resonant transformation ware can divide into full bridge type and half-bridge type according to the rectification mode, and to full bridge type LLC resonant transformation ware, it adopts circuit transformer to carry out resonant current's detection mostly, nevertheless because current transformer's is with high costs to full bridge type LLC resonant transformation ware's overall cost has been improved.
Disclosure of Invention
In order to overcome the defects of the prior art, an object of the present invention is to provide a full-bridge LLC resonant converter, which uses a first resistor and a first capacitor to replace a current transformer to detect the resonant current, thereby reducing the overall cost.
One of the purposes of the invention is realized by adopting the following technical scheme:
a full bridge LLC resonant converter, comprising: the detection circuit comprises a full-bridge rectification circuit, a resonance circuit, a detection circuit and a secondary side circuit;
the full-bridge rectification circuit comprises two first bridge arms and two second bridge arms, the resonant circuit is provided with an access point A1 and an access point A2, one first bridge arm is connected between the access point A1 and the positive end of the direct current source, the other first bridge arm is connected between the access point A2 and the negative end of the direct current source, one second bridge arm is connected between the access point A1 and the negative end of the direct current source, and the other second bridge arm is connected between the access point A2 and the positive end of the direct current source; the two first bridge arms are synchronously conducted, the two second bridge arms are synchronously conducted, and the first bridge arms and the second bridge arms are asynchronously conducted;
the resonance circuit comprises a first inductor, a second inductor, a resonance capacitor and a transformer bank, wherein the transformer bank is provided with a first winding, a second winding and a third winding, the resonance capacitor is provided with a first end and a second end, the first inductor and the first winding are connected in series between the access point A1 and the first end, the second inductor and the second winding are connected in series between the access point A2 and the second end, the potentials of the first end and the second end are the same in value and opposite in direction, and the third winding is connected in series with the secondary side circuit;
the detection circuit comprises a first resistor and a first capacitor, the first resistor and the first capacitor are connected in series, one end of the first resistor, which is far away from the first capacitor, is connected to any end of the resonance capacitor, the first resistor is far away from one end of the first capacitor, which is grounded, wherein the ratio of the voltage value at two ends of the first capacitor to the voltage value at two ends of the first resistor is greater than 50, so that the numerical value of the resonance current and the voltage value at two ends of the first resistor are in a linear relationship.
Further, the detection circuit further comprises a second resistor and a second capacitor, the second resistor and the second capacitor are connected in series, one end of the first capacitor far away from the first resistor and one end of the second capacitor far away from the second resistor are respectively connected to the first end and the second end, one end of the second resistor far away from the second capacitor is grounded, and the ratio of the voltage value at the two ends of the second capacitor to the voltage value at the two ends of the second resistor is greater than 50, so that the numerical value of the resonant current and the voltage value at the two ends of the second resistor are in a linear relationship.
Further, the first bridge arm and the second bridge arm are both bidirectional switches formed by any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay, or a combination of the MOSFET tube, the IGBT tube, the GaN tube, the triode, the thyristor and the relay.
Furthermore, the secondary side circuit comprises a fifth diode, a sixth diode, a seventh diode, an eighth diode, a third capacitor and a load, one end of the third winding is connected to the anode of the fifth diode, the other end of the third winding is connected to the anode of the sixth diode, the cathode of the fifth diode is connected to the cathode of the sixth diode, the anode of the fifth diode is connected to the cathode of the seventh diode, the anode of the sixth diode is connected to the cathode of the eighth diode, the anode of the seventh diode and the anode of the eighth diode are connected to the ground, and the load and the third capacitor are connected in parallel between the cathode of the fifth diode and the anode of the seventh diode.
Further, the transformer bank comprises 2n transformers, n being greater than zero; the primary windings of the 2n transformers are connected in series in the same direction, wherein the primary windings of the n transformers are positioned between the first end of the resonant capacitor and the access point A1 and form a first winding; the primary windings of the further n transformers are located between the second end of the resonant capacitor and the access point a2 and form a second winding.
Further, the transformer bank comprises 2m-1 transformers, wherein m is larger than zero; the primary windings of 2m-1 transformers are connected in series in the same direction, wherein two sub-windings are led out from the primary winding of the mth transformer, and the primary windings of the m-1 transformers and one sub-winding of the mth transformer are positioned between the first end of the resonant capacitor and the access point A1 and form a first winding; wherein the primary windings of the m +1 transformers and the other sub-winding of the m-th transformer are located between the second end of the resonant capacitor and the access point a2 and form a second winding.
The overcurrent protection circuit comprises a comparison module, the input end of the comparison module is connected to one end, far away from the ground, of the first resistor, and the output end of the comparison module is connected to the control ends of the first bridge arm and the second bridge arm; and when the comparison module judges that the voltage value of the first resistor exceeds a preset range, controlling the first bridge arm and the second bridge arm to be powered off.
It is another object of the present invention to provide a method for detecting a resonant current by detecting a voltage value V of a first resistor1Thereby rapidly obtaining the resonance current.
One of the purposes of the invention is realized by adopting the following technical scheme: a resonance current detection method is applied to the full-bridge LLC resonance converter, and comprises the following steps:
obtaining the voltage value of the first resistor and recording as V1；
The voltage value V is measured1Inputting a first formula to obtain a resonant current, wherein the first formulaComprises the following steps: ir ═ 2 ═ C5)/(R1*C1)*V1Here, Ir is a resonant current flowing through the resonant circuit, C5 is a capacitance of the resonant capacitor, R1 is a resistance of the first resistor, and C1 is a capacitance of the first capacitor.
Compared with the prior art, the invention has the beneficial effects that: when the two first bridge arms are switched on and the two second bridge arms are switched off, the current output by the direct current source sequentially flows through: the forward end of the direct current source, the first bridge arm connected with the access point A1, the resonant circuit, the first bridge arm connected with the access point A2, and the reverse end of the direct current source; when the two first bridge arms are turned off and the two second bridge arms are turned on, the current output by the direct current source sequentially flows through: in the two processes, the values of the potentials of the first end and the second end are kept to be the same and the directions are opposite, so that the potential of the first capacitor far away from the first resistor is equal to the voltage value of the 1/2 resonant capacitor, and the ratio of the voltage value of the two ends of the first capacitor to the voltage value of the two ends of the first resistor is greater than 50, so that the resonant current and the voltage values of the two ends of the first resistor can be regarded as being in linear distribution, and the value of the resonant current can be quickly obtained.
Drawings
Fig. 1 is a circuit diagram of a full bridge type LLC resonant converter shown in a first embodiment;
fig. 2 is a flowchart of the oscillating current detection method according to the second embodiment.
In the figure: 10. a full-bridge rectifier circuit; 20. a resonant circuit; 30. a detection circuit; 40. a secondary side circuit; 50. an overcurrent protection circuit.
Detailed Description
The present invention will now be described in more detail with reference to the accompanying drawings, in which the description of the invention is given by way of illustration and not of limitation. The various embodiments may be combined with each other to form other embodiments not shown in the following description.
Example one
The embodiment provides a full-bridge LLC resonant converter, and aims to solve the problem that the whole cost is high because the current transformer is adopted to sample resonant current in the existing full-bridge LLC resonant converter.
Specifically, referring to fig. 1, the full-bridge type LLC resonant converter includes: full-bridge rectifier circuit 10, resonant circuit 20, detection circuit 30 and secondary circuit 40.
The full-bridge rectification circuit 10 includes two first bridge arms and two second bridge arms, and both the two first bridge arms and the two second bridge arms are used for rectification. The resonant circuit 20 has access point a1 and access point a 2. One of the first bridge arms is connected between the access point A1 and the forward end of the direct current source, the other first bridge arm is connected between the access point A2 and the reverse end of the direct current source, one of the second bridge arms is connected between the access point A1 and the reverse end of the direct current source, the other second bridge arm is connected between the access point A2 and the forward end of the direct current source, the two first bridge arms are synchronously conducted, the two second bridge arms are synchronously conducted, and the first bridge arm and the second bridge arm are asynchronously conducted.
The resonant circuit 20 comprises a first inductor L1, a second inductor L2, a resonant capacitor C5 and a transformer bank, wherein the transformer bank is formed with a first winding, a second winding and a third winding, the resonant capacitor C5 has a first end and a second end, the first inductor L1 and the first winding are connected in series between an access point a1 and the first end, the second inductor L2 and the second winding are connected in series between an access point a2 and the second end, the potentials of the first end and the second end are the same in value and opposite in direction, and the third winding is connected in series with the secondary side circuit 40. The first inductor L1 and the second inductor L2 are of the same type.
The detection circuit 30 includes a first resistor R1 and a first capacitor C1, the first resistor R1 is connected in series with the first capacitor C1, one end of the first capacitor C1 far away from the first resistor R1 is connected to the first end or the second end of the resonant capacitor C5, one end of the first resistor R1 far away from the first capacitor C1 is grounded, wherein a ratio of a voltage value at two ends of the first capacitor C1 to a voltage value at two ends of the first resistor R1 is greater than 50, so that a value of the resonant current and a voltage value at two ends of the first resistor R1 are in a linear relationship.
In summary, when the two first bridge arms are turned on and the two second bridge arms are turned off, the current output by the dc source sequentially flows through: the forward end of the direct current source, the first bridge arm connected with the access point A1, the resonant circuit, the first bridge arm connected with the access point A2, and the reverse end of the direct current source; when the two first bridge arms are turned off and the two second bridge arms are turned on, the current output by the direct current source sequentially flows through: the forward terminal of the dc source-the second leg connected to access point a 2-the resonant circuit-the second leg connected to access point a 1-the reverse terminal of the dc source.
In the two processes, the values of the potentials of the first end and the second end are kept the same and the directions are opposite, so that the potential of the first capacitor C1 far away from the first resistor R1 is equal to the voltage value of the resonant capacitor C5 1/2, and since the ratio of the voltage value of the two ends of the first capacitor C1 to the voltage value of the two ends of the first resistor R1 is greater than 50, the resonant current and the voltage value of the two ends of the first resistor R1 can be regarded as being in linear distribution, and the value of the resonant current can be obtained quickly.
As an optional technical solution, the first bridge arm and the second bridge arm are both bidirectional switches formed by any one of a MOSFET tube, an IGBT tube, a GaN tube, a triode, a thyristor and a relay, or a combination thereof.
It should be noted here that the two first bridge arms may have multiple branches, but the number and connection manner of the branches of the two first bridge arms should be the same, and the number and model of the components of the two first bridge arms on the corresponding same branches are the same, and of course, the connection order may be the same or different. The two second bridge arms may also have a plurality of branches, which may specifically refer to the above related descriptions and are not described herein again.
For example, when the two first bridge arms both adopt a combination of a parasitic diode and an N-channel enhancement type MOSFET transistor, and the two second bridge arms also both adopt a combination of a parasitic diode and an N-channel enhancement type MOSFET transistor, the two N-channel enhancement type MOSFET transistors of the two first bridge arms are respectively denoted as S1 and S4, the corresponding parasitic diodes are respectively denoted as D1 and D4, the two MOSFET transistors of the two second bridge arms are respectively denoted as S2 and S3, and the corresponding parasitic diodes are respectively denoted as D2 and D3. Specifically, the drain of the MOSFET tube S1 is connected to the positive terminal of the dc source, and the source is connected to the drain of the MOSFET tube S3; the source electrode of the MOSFET S3 is connected with the reverse end of the direct current source, and the reverse end of the direct current source is grounded; the drain electrode of the MOSFET tube S2 is connected with the positive end of the direct current source, and the source electrode is connected with the drain electrode of the MOSFET tube S4; the source electrode of the MOSFET S4 is connected with the reverse end of the direct current source; the cathode of each parasitic diode is connected with the drain electrode of the corresponding MOSFET, and the anode of each parasitic diode is connected with the source electrode of the corresponding MOSFET; the access point a1 is connected to the source of the MOSFET transistor S1, and the access point a2 is connected to the source of the MOSFET transistor S2.
It can be understood that the MOSFET tube S1 is turned on synchronously with the MOSFET tube S4, i.e. the duty cycle of the two is the same; the MOSFET transistor S2 is turned on synchronously with the MOSFET transistor S3, i.e. both have the same duty cycle.
The MOSFET tube S1 and the MOSFET tube S2 are asynchronously conducted, and then the MOSFET tube S1 and the MOSFET tube S2 are staggered in a mode of shifting the phase by 180 degrees. Specifically, when the MOSFET S1 is turned on and the corresponding phase range is [360n + x, 360n + y ], the MOSFET S2 is turned on and the corresponding phase range is [360n +180+ x, 360n +180+ y ] or [360n-180+ x, 360n-180+ y ], where n is a natural number, and 0 ° < (y-x) < 360 °.
When the MOSFET transistor S1 and the MOSFET transistor S4 are turned on, the MOSFET transistor S2 and the MOSFET transistor S3 are turned off, and the current flows through: the forward end of the direct current source, namely the MOSFET S1, the resonant circuit 20, the MOSFET S4, and the reverse end of the direct current source, namely the two first bridge arms can be regarded as being symmetrically arranged relative to the direct current source and the resonant circuit 20; when the MOSFET transistor S1 and the MOSFET transistor S4 are turned off, the MOSFET transistor S2 and the MOSFET transistor S3 are turned on, and the current flows through: the forward end of the direct current source, flowing through the MOSFET transistor S2, the resonant circuit 20, the MOSFET transistor S3, and the reverse end of the direct current source, i.e., the two second legs can be regarded as being symmetrically arranged with respect to the direct current source and the resonant circuit 20, so that the potential values of the first end and the second end are controlled to be equal.
As an optional technical solution, in the resonant circuit 20, the transformer bank may include 2n transformers T, n is greater than zero, and the types of the 2n transformers T are all equal, and the circuit diagram shown in fig. 1 is a circuit diagram in which the transformer bank employs two transformers T. The primary windings of the 2n transformers T are connected in series in the same direction, namely the homonymous end of any primary winding is connected with the heteronymous end of the adjacent primary winding, so that the effect of signal enhancement is achieved. The primary windings of the n transformers T are positioned between the first end of the resonant capacitor C5 and the access point A1 and form a first winding; the primary windings of the further n transformers T are located between the second terminal of the resonant capacitor C5 and the access point a2 and form a second winding. It should be noted that the overall resistance, the number of turns, the diameter, and the free-wheeling capability of the first winding and the second winding are all equal, that is, the first winding and the second winding can be regarded as being symmetrically arranged with respect to the resonant capacitor C5, so as to facilitate controlling the potential values of the first terminal and the second terminal to be equal.
As an optional technical solution, in the resonant circuit 20, the transformer bank includes 2m to 1 transformers T, m is greater than zero, and models of the 2m to 1 transformers T are all equal. The primary windings of 2m-1 transformers T are connected in series in the same direction, namely the homonymous end of any primary winding is connected with the heteronymous end of the adjacent primary winding, so that the effect of signal enhancement is realized. Two sub-windings are led out from the primary winding of the mth transformer T, wherein the primary winding of the m-1 transformers T and one sub-winding of the mth transformer T are positioned between the first end of the resonant capacitor C5 and the access point A1, and form a first winding; wherein the primary windings of the m +1 transformers T and the other sub-winding of the mth transformer T are located between the second terminal of the resonant capacitor C5 and the access point a2 and form a second winding. It should be noted that the overall resistance, the number of turns, the diameter, and the free-wheeling capability of the first winding and the second winding are all equal, that is, the first winding and the second winding can be regarded as being symmetrically arranged with respect to the resonant capacitor C5, so as to facilitate controlling the voltage values of the first terminal and the second terminal to be equal.
It should be noted that the number of the transformers T may be set according to actual conditions, as long as the number is greater than one, and the setting position of the resonant capacitor C5 may be adjusted according to the number of the transformers T or specific parameters. Due to the fact that the types of the transformers T in the technical scheme are consistent, the setting position of the resonance capacitor C5 can be conveniently and rapidly determined, and the time for calculation and simulation is saved. Of course, the arrangement of the transformer T is not limited to the above-mentioned manner, for example, the types of the transformer T may also be different, and the number of the primary windings at two ends of the resonant capacitor C5 may also be different, but it is only necessary to ensure that the potentials at the first end and the second end have the same value and opposite directions.
As an optional technical solution, the detection circuit 30 further includes a second resistor R2 and a second capacitor C2, the second resistor R2 is connected in series with the second capacitor C2, one end of the first capacitor C1, which is far away from the first resistor R1, and one end of the second capacitor C2, which is far away from the second resistor R2, are respectively connected to the first end and the second end, one end of the second resistor R2, which is far away from the second capacitor C2, is grounded, wherein a ratio of a voltage value at two ends of the second capacitor C2 to a voltage value at two ends of the second resistor R2 is greater than 50, so that a value of the resonant current and a voltage value at two ends of the second resistor R2 are in a linear relationship.
It should be noted that, since the first terminal and the second terminal have the same potential and opposite potentials, the voltage of the resonant capacitor C5 is denoted as V5The first terminal and the second terminal are both 1/2 × V5, and the first resistor R1 and the first capacitor C1 are taken as an example for explanation, since Ir ═ C5*dV5/dt，
Figure BDA0002658173330000091
Because the voltage value at the two ends of the first capacitor C1 and the voltage value V at the two ends of the first resistor R11If the ratio of (A) to (B) is greater than 50, V1Relative to 1/2V5Can be ignored, i.e.
Figure BDA0002658173330000092
Thereby making Ir ═ 2 ═ C5)/(R1*C1)*V1Wherein Ir is the current value of the resonant current, C5Is the capacitance value, V, of the resonant capacitor C55Is the voltage value, R, of the resonant capacitor C51Is the resistance value of the first resistor R1, C1The capacitance value of the first capacitor C1 is (2 × C)5)/(R1*C1) Is constant, therefore, only the voltage value V of the first resistor R1 needs to be obtained1The current value of the resonant current can be obtained, and the direction of the resonant current can be calculated from the period of the direct current source, so that the corresponding resonant current can be obtained.
Reference toIn the above description, Ir ═ 2 × C is made in the branch between the second resistor R2 and the second capacitor C25)/(R2*C2)*V1Wherein Ir is the current value of the resonant current, C5Is the capacitance value, V, of the resonant capacitor C55Is the voltage value of the resonant capacitor C5, R2Is the resistance value of the second resistor R2, C2The capacitance value of the second capacitor C2 is (2 × C)5)/(R2*C2) Is constant, therefore, only the voltage value V of the second resistor R2 needs to be obtained2The current value of the resonant current can be obtained, and the direction of the resonant current can be calculated from the period of the direct current source, so that the corresponding resonant current can be obtained.
It should be noted that, since the potentials of the first end and the second end are opposite, if the first resistor R1 is connected to the first end in a matching manner, and the second resistor R2 is connected to the second end in a matching manner, the phase of the voltage across the first resistor R1 is the same as the phase of the resonant current, and the phase difference between the voltage across the first resistor R1 and the voltage across the second resistor R2 is 180 degrees, so that a user can draw a required voltage according to his own needs, and avoid using a corresponding component to perform phase inversion.
Through the technical scheme, subsequent voltage extraction is convenient to carry out, and the voltage value V of the first resistor R1 can be measured1And the voltage value V2 of the second resistor R2 to obtain a calculated value of the corresponding resonance current, so that mutual verification is performed to improve the accuracy of the result.
As an alternative solution, the secondary circuit 40 includes a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a third capacitor C3, and a load Rx, one end of the third winding is connected to the anode of the fifth diode D5, the other end is connected to the anode of the sixth diode D6, the cathode of the fifth diode D5 is connected to the cathode of the sixth diode D6, the anode of the fifth diode D5 is connected to the cathode of the seventh diode D7, the anode of the sixth diode D6 is connected to the cathode of the eighth diode D8, the anode of the seventh diode D7 and the anode of the eighth diode D8 are connected to ground, and the load Rx and the third capacitor C3 are connected in parallel between the cathode of the fifth diode D5 and the anode of the seventh diode D7. It should be noted here that when the transformer bank includes more than one transformer T, the secondary windings of the transformers T are also connected in series in the same direction to form a third winding, so that the generated current of the secondary circuit 40 is rectified.
As an optional technical solution, the full-bridge LLC resonant converter may further include an overcurrent protection circuit 50, where the overcurrent protection circuit 50 includes a comparison module, an input end of the comparison module is connected to one end of the first resistor R1 and/or the second resistor R2, which is far away from the ground, an output end of the comparison module is connected to control ends of the first bridge arm and the second bridge arm, and when the comparison module determines that the voltage value of the first resistor R1 exceeds a preset range, the first bridge arm and the second bridge arm are both controlled to be powered off.
For example: the output end of the comparison module can be connected to the control electrode of the MOSFET transistor S1 and/or the MOSFET transistor S4 via the driver chip, and the output end of the comparison module can be connected to the control electrode of the MOSFET transistor S2 and/or the control electrode of the MOSFET transistor S3 via the driver chip, so that the full-bridge LLC resonant converter is controlled to stop operating when overcurrent occurs.
As an optional technical solution, the full-bridge LLC resonant converter may further include a display, an input end of the display is connected to a far end of the first resistor R1 and/or the second resistor R2, the display processes the voltage of the first resistor R1 and/or the second resistor R2, and displays a change curve of the resonant current on the display, so as to facilitate observation by a user.
Example two
The present embodiment provides a resonance current detection method, which is applied to the full-bridge LLC resonant converter shown in the first embodiment, and referring to fig. 1 and fig. 2, the resonance current detection method includes step S10 and step S20.
In step S10, the voltage value of the first resistor R1 is obtained and recorded as V1. The obtaining method is not limited herein, and reference may be made to a method that is correspondingly used when the existing current transformer performs resonance current detection.
Step S20, converting the voltage value V1Inputting a first formula to obtain a resonant current, wherein the first formula is as follows: ir ═ C (2 × C)5)/(R1*C1)*V1Where Ir is the resonant current flowing through the resonant circuit 20, C5Is the capacitance value of the resonant capacitor C5, R1Is the resistance value of the first resistor R1, C1Is the capacitance value of the first capacitor C1. This step can be referred to the relevant description in reference to the first embodiment.
The above embodiments are only preferred embodiments of the present invention, and the scope of the present invention should not be limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are intended to be covered by the claims.

Claims (8)

1. A full-bridge LLC resonant converter, comprising: the detection circuit comprises a full-bridge rectification circuit, a resonance circuit, a detection circuit and a secondary side circuit;
the full-bridge rectification circuit comprises two first bridge arms and two second bridge arms, the resonant circuit is provided with an access point A1 and an access point A2, one first bridge arm is connected between the access point A1 and the positive end of the direct current source, the other first bridge arm is connected between the access point A2 and the negative end of the direct current source, one second bridge arm is connected between the access point A1 and the negative end of the direct current source, and the other second bridge arm is connected between the access point A2 and the positive end of the direct current source; the two first bridge arms are synchronously conducted, the two second bridge arms are synchronously conducted, and the first bridge arms and the second bridge arms are asynchronously conducted, wherein the two first bridge arms are symmetrically arranged relative to the direct current source and the resonance circuit, the two second bridge arms are symmetrically arranged relative to the direct current source and the resonance circuit, the two first bridge arms are conducted, and when the two second bridge arms are turned off, currents output by the direct current source sequentially flow through: the forward end of the direct current source, the first bridge arm connected with the access point A1, the resonant circuit, the first bridge arm connected with the access point A2, and the reverse end of the direct current source; when the two first bridge arms are turned off and the two second bridge arms are turned on, the current output by the direct current source sequentially flows through: the forward end of the direct current source, the second bridge arm connected with the access point A2, the resonant circuit, the second bridge arm connected with the access point A1 and the reverse end of the direct current source;
the resonance circuit comprises a first inductor, a second inductor, a resonance capacitor and a transformer bank, wherein the transformer bank is provided with a first winding, a second winding and a third winding, the resonance capacitor is provided with a first end and a second end, the first inductor and the first winding are connected in series between the access point A1 and the first end, the second inductor and the second winding are connected in series between the access point A2 and the second end, the potential values of the first end and the second end are the same, the potential directions of the first end and the second end are opposite, the third winding is connected in series with the secondary side circuit, one end of a first resistor and one end of a second resistor in the detection circuit are grounded, and the secondary side circuit is grounded;
the detection circuit comprises a first resistor and a first capacitor, the first resistor and the first capacitor are connected in series, one end of the first resistor, which is far away from the first capacitor, is connected to any end of the resonance capacitor, the first resistor is far away from one end of the first capacitor, which is grounded, wherein the ratio of the voltage value at two ends of the first capacitor to the voltage value at two ends of the first resistor is greater than 50, so that the numerical value of the resonance current and the voltage value at two ends of the first resistor are in a linear relationship.
2. The full-bridge LLC resonant converter according to claim 1, wherein said detection circuit further comprises a second resistor and a second capacitor, said second resistor and said second capacitor are connected in series, an end of said first capacitor far from said first resistor and an end of said second capacitor far from said second resistor are respectively connected to said first end and said second end, an end of said second resistor far from said second capacitor is grounded, wherein a ratio of a voltage value across said second capacitor to a voltage value across said second resistor is greater than 50, so that a value of said resonant current and a voltage value across said second resistor are in a linear relationship.
3. The full-bridge LLC resonant converter according to claim 1, wherein said first and second bridge legs are bidirectional switches constituted by any one of MOSFET tubes, IGBT tubes, GaN tubes, triodes, thyristors and relays, or a combination thereof.
4. A full-bridge LLC resonant converter as claimed in claim 1, wherein the secondary circuit comprises a fifth diode, a sixth diode, a seventh diode, an eighth diode, a third capacitor and a load, one end of the third winding is connected to the anode of the fifth diode, the other end is connected to the anode of the sixth diode, the cathode of the fifth diode is connected to the cathode of the sixth diode, the anode of the fifth diode is connected to the cathode of the seventh diode, the anode of the sixth diode is connected to the cathode of the eighth diode, the anode of the seventh diode and the anode of the eighth diode are connected and grounded, and the load and the third capacitor are connected in parallel between the cathode of the fifth diode and the anode of the seventh diode.
5. A full-bridge LLC resonant converter according to any one of claims 1 to 4, wherein said transformer bank comprises 2n transformers, n being greater than zero; the primary windings of the 2n transformers are connected in series in the same direction, wherein the primary windings of the n transformers are positioned between the first end of the resonant capacitor and the access point A1 and form a first winding; the primary windings of the further n transformers are located between the second end of the resonant capacitor and the access point a2 and form a second winding.
6. A full bridge LLC resonant converter according to any one of claims 1 to 4, wherein said transformer bank comprises 2m-1 transformers, m being greater than zero; the primary windings of 2m-1 transformers are connected in series in the same direction, wherein two sub-windings are led out from the primary winding of the mth transformer, and the primary windings of the m-1 transformers and one sub-winding of the mth transformer are positioned between the first end of the resonant capacitor and the access point A1 and form a first winding; wherein the primary windings of the m +1 transformers and the other sub-winding of the m-th transformer are located between the second end of the resonant capacitor and the access point a2 and form a second winding.
7. The full-bridge LLC resonant converter according to claim 1, further comprising an overcurrent protection circuit, wherein said overcurrent protection circuit comprises a comparison module, an input end of said comparison module is connected to one end of said first resistor which is far from the ground, and an output end of said comparison module is connected to control ends of said first bridge arm and said second bridge arm; and when the comparison module judges that the voltage value of the first resistor exceeds a preset range, controlling the first bridge arm and the second bridge arm to be powered off.
8. A resonant current detection method, applied to a full-bridge LLC resonant converter as claimed in any one of claims 1 to 7, comprising the steps of:
acquiring the voltage value of the first resistor and recording the voltage value as V1；
The voltage value V is measured1Inputting a first formula to obtain a resonant current, wherein the first formula is as follows: ir ═ 2 ═ C5)/(R1*C1)*V1Wherein Ir is the resonant current flowing through the resonant circuit, C5Is the capacitance value of the resonant capacitor, R1Is the resistance value of the first resistor, C1Is the capacitance value of the first capacitor.
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