CN109302071B - Full-wave active rectification type LLC resonant converter and control strategy thereof - Google Patents

Full-wave active rectification type LLC resonant converter and control strategy thereof Download PDF

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Publication number
CN109302071B
CN109302071B CN201811233483.4A CN201811233483A CN109302071B CN 109302071 B CN109302071 B CN 109302071B CN 201811233483 A CN201811233483 A CN 201811233483A CN 109302071 B CN109302071 B CN 109302071B
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full
switch network
wave active
wave
secondary side
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CN109302071A (en
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汤欣喜
吴红飞
邢岩
罗有纲
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Nanjing University of Aeronautics and Astronautics
Lite On Technology Corp
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Nanjing University of Aeronautics and Astronautics
Lite On Technology Corp
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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
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33576—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer
    • H02M3/33592—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements having at least one active switching element at the secondary side of an isolation transformer having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
    • 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 invention discloses a full-wave active rectification type LLC resonant converter and a control strategy thereof, belonging to the technical field of power electronic converters. The converter is composed of an input source, an input bus capacitor, a primary side switch network, a resonant inductor, a resonant capacitor, a transformer, n (more than or equal to 1) secondary side full-wave active rectifier switch networks, m (more than or equal to 0) secondary side full-wave rectifier switch networks, an output filter capacitor and an output load; when the input voltage is near the rated working point, the auxiliary active switching tube is kept to be switched off, and the converter adopts frequency conversion control; when the input voltage drops, the output voltage is kept stable by adjusting the duty ratio of the auxiliary active switch on the secondary side; the full-wave active rectification type LLC resonant converter can meet two requirements of a power supply system for maintaining steady-state working point efficiency and transient voltage drop at the same time, and is particularly suitable for application occasions requiring the power supply system to have power-down maintaining capability, such as a server power supply and a rail transit power supply.

Description

Full-wave active rectification type LLC resonant converter and control strategy thereof
Technical Field
The invention relates to a full-wave active rectification type LLC resonant converter and a control strategy thereof, belonging to the technical field of power electronic converters, in particular to the technical field of isolation type DC-DC electric energy conversion.
Background
With the development of information technology, isolated direct-current power supply modules are adopted for supplying power in various application occasions, and the requirements are more and more, and higher. Particularly, in the occasions of servers, rail transit and the like, the direct-current power supply module is required to have high efficiency and small volume, and meanwhile, when the input voltage drops, the output voltage can be kept stable within a certain time, so that the system can complete the operations of storing key data, switching to a standby power supply and the like. To achieve this, the input bus capacitance is typically increased to ensure the power down time requirement, but the converter size is increased. The capacitance volume of the bus is further reduced, the output voltage can be kept unchanged in a wider input voltage range, and meanwhile, the working efficiency of a steady-state working point is considered.
In recent years, the conventional LLC resonant converter has been widely used because of its high efficiency, high power density, and low cost. It can realize soft switching of all power semiconductor devices, reduce electromagnetic interference and realize high frequency, so that it can reduce the power consumption of power semiconductor deviceIs widely applied. However, as the input voltage range of the LLC resonant converter is wider, the magnetizing inductance (L) of the converterm) The smaller the circulation, the greater the efficiency of the entire operating range. Therefore, the conventional LLC resonant converter shown in fig. 1 is not suitable for situations with an excessively wide input voltage range.
In order to expand the input voltage range of the traditional LLC Resonant Converter and simultaneously consider the steady-state operation efficiency of the Converter, the documents "Kim Moon-Young, Kim Bong-Chul, Park Kik Ki-Bum, Moon Gun-Wo.LLC Series resource Converter with Autoliary Hold-Up Time Compensation Circuit [ J ].8th International Conference on Power Electronics-ECCE Asia, 2011: 628-633 "proposed a modified LLC converter with secondary plus auxiliary windings as shown in FIG. 3. On the basis of the original low-gain working mode, the improved LLC converter with the auxiliary winding added on the secondary side has two working modes totally according to whether the auxiliary winding of the transformer (T) is switched in or not. When the input voltage is near the rated point, the auxiliary winding is disconnected and does not participate in the work; when the input voltage drops, the auxiliary winding participates in work, and the gain of the converter is improved. However, when the transformer works in a power-down maintaining state, the transformer works in an asymmetric state and has magnetic biasing, and the introduction of the auxiliary winding makes the transformer complex in process, inconvenient to process and reduces the utilization rate of the magnetic core.
Disclosure of Invention
The invention aims to provide a full-wave active rectification type LLC resonant converter and a control strategy thereof aiming at the defects of the prior art.
The purpose of the invention is realized by the following technical scheme:
the full-wave active rectification type LLC resonant converter is composed of an input source UinInput bus capacitor CinPrimary side switch network, resonant inductor LrResonant capacitor CrN + m transformers, n secondary side full-wave active rectification switch networks, m secondary side full-wave rectification switch networks and output filter capacitor CoAnd an output load RoWherein n is more than or equal to 1, m is more than or equal to 0, and transformer TkPrimary side excitation inductance value of Lm，kWherein k is not less than 1N + m is less than or equal to; the two input ends of the primary side switching network are respectively connected with an input source UinAre connected with the output end a of the primary side switch network and the resonant inductor LrAre connected to one end of a resonant inductor LrThe other end of the transformer and the transformer T1Transformer T with primary winding connected to the same name terminal1Different name terminal of primary winding and transformer T2The homonymous terminals of the primary windings are connected, and so on, and the transformer Tk-1Different name terminal of primary winding and transformer TkTransformer T with primary winding connected to the same name terminaln+mSynonym terminal and resonant capacitor C of primary windingrIs connected to one end of a resonant capacitor CrThe other end of the primary side switch network is connected with the output end b of the primary side switch network; when k is more than or equal to 1 and less than or equal to n, the transformer TkHomonymous terminal of secondary winding and input terminal c of secondary full-wave active rectification switch networkkConnected to each other, a transformer TkCenter tap of secondary winding and input end d of secondary full-wave active rectifier switch networkkConnected to each other, a transformer TkSynonym terminal of secondary winding and input terminal e of secondary full-wave active rectification switch networkkConnecting; when k is more than or equal to n +1 and less than or equal to n + m, the transformer TkHomonymous terminal of secondary winding and input terminal c of secondary full-wave rectification switch networkkConnected to each other, a transformer TkCenter tap of secondary winding and input end d of secondary full-wave rectification switch networkkConnected to each other, a transformer TkSynonym terminal of secondary winding and input terminal e of secondary full-wave rectification switch networkkThe two output ends of the secondary side full-wave active rectification switch network and the two output ends of the secondary side full-wave rectification switch network are respectively connected with an output filter capacitor CoTwo ends of (1), output load RoTwo ends are connected.
The primary side switch network is an asymmetric half-bridge switch network, or a symmetric half-bridge switch network, or a full-bridge switch network.
The secondary side full-wave active rectification switch network is a common-cathode full-wave active rectification switch network and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A third rectifying diode Dk，3A fourth rectifying diode Dk，4And assistAuxiliary switch tube Sk，aIs composed of a first rectifying diode Dk，1And a third rectifying diode Dk，3Input end c of anode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Cathode and auxiliary switch tube Sk，aIs connected to the drain of the third rectifying diode Dk，3And a fourth rectifying diode Dk，4Cathode and output filter capacitor CoPositive electrode, output load RoIs connected to the anode of a second rectifying diode Dk，2And a fourth rectifying diode Dk，4Input terminal e of anode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aInput terminal d of the source and secondary full-wave active rectification switch networkkAn output filter capacitor CoNegative electrode of (1), output load RoThe negative electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
The secondary side full-wave active rectification switch network is a common-positive full-wave active rectification switch network and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A third rectifying diode Dk，3A fourth rectifying diode Dk，4And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a third rectifying diode Dk，3Input terminal c of cathode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Anode of (2), auxiliary switch tube Sk，aIs connected to the source of the third rectifying diode Dk，3And a fourth rectifying diode Dk，4Anode and output filter capacitor CoNegative electrode of (1), output load RoIs connected to the negative pole of a second rectifier diode Dk，2And a fourth rectifying diode Dk，4Input terminal e of cathode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aDrain and secondary side full wave active rectification switch network input terminal dkAn output filter capacitor CoPositive electrode, output load RoThe positive electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
The secondary side full-wave active rectification switch network is a full-wave active rectification switch network with a synchronous rectification function and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A first synchronous rectification switch tube Sk，s1A second synchronous rectification switch tube Sk，s2And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a first synchronous rectification switching tube Sk，s1Input terminal c of source and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Cathode and auxiliary switch tube Sk，aIs connected with the drain electrode of the first synchronous rectification switch tube Sk，s1And a second synchronous rectification switching tube Sk，s2Drain electrode of (1), and output filter capacitor CoPositive electrode, output load RoIs connected to the anode of a second rectifying diode Dk，2And a second synchronous rectification switching tube Sk，s2Input terminal e of source electrode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aInput terminal d of the source and secondary full-wave active rectification switch networkkAn output filter capacitor CoNegative electrode of (1), output load RoThe negative electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
The secondary side full-wave active rectification switch network is another full-wave active rectification switch network with synchronous rectification function and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A first synchronous rectification switch tube Sk，s1A second synchronous rectification switch tube Sk，s2And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a first synchronous rectification switch tube Sk，s1Input terminal c of the drain electrode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Anode and auxiliary opening ofClosing pipe Sk，aIs connected with the source electrode of the first synchronous rectification switch tube Sk，s1Source electrode of and the second synchronous rectification switch tube Sk，s2Source electrode, output filter capacitor CoNegative electrode of (1), output load RoIs connected to the negative pole of a second rectifier diode Dk，2And a second synchronous rectification switch tube Sk，s2Input terminal e of drain electrode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aDrain and secondary side full wave active rectification switch network input terminal dkAn output filter capacitor CoPositive electrode, output load RoThe positive electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
The secondary side full-wave rectification switch network is a full-wave rectification switch network or a full-wave rectification switch network with a synchronous rectification function.
The control strategy of the full-wave active rectification type LLC resonant converter is that when the input voltage is near a rated working point, the auxiliary switch tube Sk，aKeeping the switching-off, keeping the output voltage constant by adjusting the switching frequency of a primary side switching network of the converter, and enabling the converter to work near a resonant frequency point; when the input voltage drops and the output voltage can not be maintained through the frequency conversion control, the auxiliary switch tube Sk，aAdopting Pulse Width Modulation (PWM) strategy, the converter is fixedly operated at a resonant frequency point, and the auxiliary switch tube S is increasedk，aThe duty ratio of (1) and (k) is not less than n, and the output voltage is kept constant.
The control strategy of the full-wave active rectification type LLC resonant converter is that when the input voltage drops and the output voltage cannot be maintained through frequency conversion control, the auxiliary switching tube S is increased firstly1，aThe duty ratio of (1) to maintain the output voltage constant; as an auxiliary switch tube S1，aWhen the duty ratio reaches 1, the auxiliary switch tube S is increased2，aDuty cycle of (d); by analogy, when the auxiliary switch tube Sk，aWhen the duty ratio reaches 1, the auxiliary switch tube S is increasedk+1，aK is more than or equal to 1 and less than or equal to n-1; if the number m of the secondary side full-wave rectification switch networks is 0, the duty ratio of the nth secondary side full-wave active rectification switch network needs to be smallAt 1; if the number m of the secondary side full-wave rectification switch networks is larger than or equal to 1, the duty ratio of the nth secondary side full-wave active rectification switch network can reach the maximum duty ratio of 1.
The essential difference between the technical scheme of the invention and the existing technical scheme is that an active switch tube is introduced into the traditional LLC secondary side rectifier switch network, and a new control quantity is added. When the input power supply is powered down, the converter fixedly works at a resonant frequency point, and the introduced auxiliary switching tube adopts a pulse width modulation strategy, so that the gain of the converter can be improved, and a special working mode of the invention appears. When n is 1 and m is 0, the converter gain formula expression is shown as (1).
Figure GSB0000189704340000031
In the formula, n1For a transformer T1D is an auxiliary switching tube S1，aThe duty cycle of (c).
Therefore, when n is more than or equal to 1 and m is 0, the auxiliary switch tube S in the secondary side full-wave active rectification switch networkk，aDuty ratio of drive is 1, auxiliary switch tube Sn，aThe duty ratio of the drive reaches the designed maximum value Dn，maxThe maximum gain of the converter is expressed as (2), wherein k is more than or equal to 1 and less than or equal to n-1.
Figure GSB0000189704340000032
In the formula, nnFor a transformer TnThe turn ratio of (c).
When m is more than or equal to 1, when the duty ratio of the auxiliary switch tube drive in all the secondary side full-wave active rectification switch networks is 1, the maximum voltage gain can be achieved
Figure GSB0000189704340000033
In the formula, nkFor a transformer TkThe turn ratio of (c).
The working mode greatly reduces the requirement on the peak gain of the converter working in a frequency conversion mode, the efficiency of the converter can be obviously improved by optimizing the resonant cavity parameters and the transformer parameters, the size of the input bus capacitor is reduced, and the requirement on power failure holding occasions is met.
The invention has the following beneficial effects:
(1) in designing transformer TkWhen the inductor is excited, the realization condition of the soft switch of the primary side switching tube in the normal working mode is only needed to be considered, and the transformer T is increased as much as possiblekExciting the inductor, thereby reducing the circulating current of the converter and improving the efficiency of the converter, wherein k is more than or equal to 1 and less than or equal to n + m;
(2) when the power supply is not powered down, the converter works near a resonance point, which is the optimal efficiency point of the resonance converter;
(3) the introduction of a plurality of transformers can fully optimize the structure of the transformer, reduce the secondary side leakage inductance of the transformer, reduce the processing difficulty of the transformer, improve the efficiency of the transformer and be suitable for low-voltage and high-current application occasions;
(4) when the power supply is powered off, the converter enters a PWM working mode, a larger gain range can be achieved, the size of the input bus capacitor can be effectively reduced, and the power density of the converter is improved.
Drawings
FIG. 1 is a schematic diagram of a conventional half-bridge LLC resonant converter;
FIG. 2 is a waveform diagram of a resonant point operation of a conventional half-bridge LLC resonant converter;
FIG. 3 is a schematic diagram of an improved LLC converter with an auxiliary winding added to the secondary side;
FIG. 4 is a schematic diagram of a full-wave active rectification type LLC resonant converter of the invention;
FIG. 5 is a schematic diagram of a full-wave active rectification LLC resonant converter with a full-bridge switching network adopted by a primary side switching network;
FIG. 6 is a schematic diagram of a full-wave active rectification LLC resonant converter with a symmetrical half-bridge switching network adopted by a primary side switching network;
FIG. 7 is a schematic diagram of a full-wave active rectification LLC resonant converter with another symmetrical half-bridge switching network adopted by a primary side switching network of the invention;
FIG. 8 is a schematic diagram of a full-wave active rectification LLC resonant converter with an asymmetric half-bridge switching network adopted in a primary side switching network;
FIG. 9 is a common-cathode full-wave active rectification switch network adopted by the secondary side full-wave active rectification switch network of the present invention;
FIG. 10 is a common-anode full-wave active rectifier switch network employed by the secondary full-wave active rectifier switch network of the present invention;
FIG. 11 is a full-wave active rectification switch network with synchronous rectification function adopted by the secondary side full-wave active rectification switch network of the present invention;
FIG. 12 is another full-wave active rectification switch network with synchronous rectification function used in the secondary full-wave active rectification switch network of the present invention;
FIG. 13 is a common-cathode full-wave rectification switch network employed by the secondary side full-wave rectification switch network of the present invention;
FIG. 14 is a common-anode full-wave rectifier switch network employed in the secondary full-wave rectifier switch network of the present invention;
FIG. 15 is a full-wave rectification switch network with synchronous rectification function used in the secondary side full-wave rectification switch network of the present invention;
FIG. 16 is a schematic diagram of another full-wave rectification switch network with synchronous rectification function for the secondary side full-wave rectification switch network according to the present invention;
FIG. 17 is a schematic diagram of a full-wave active rectification LLC resonant converter with an asymmetric half-bridge switching network on the primary side, a full-wave active rectification switching network with only one common cathode on the secondary side, and a full-wave rectification switching network without the secondary side;
FIG. 18 is a waveform illustrating an exemplary operation of the full-wave active rectifying LLC resonant converter of FIG. 17 in a power down hold mode;
FIG. 19 is a schematic diagram of a full-wave active rectification LLC resonant converter with an asymmetric half-bridge switching network on the primary side, a full-wave active rectification switching network with a synchronous rectification function on the secondary side, and a full-wave rectification switching network without the secondary side;
fig. 20 is a waveform diagram illustrating an exemplary operation of the full-wave active rectification type LLC resonant converter of fig. 19 in a power-down hold mode in accordance with the present invention;
FIGS. 21-23 show the converter of FIG. 17 at t in FIG. 180～t1、t1～t2、t2～t3、t3～t4Equivalent circuits of each mode in a time period (the current direction is marked as a positive direction in the figure);
FIG. 24 is a voltage gain diagram for the converter of FIG. 17 employing PWM control when the input supply voltage drops;
fig. 25 is an experimental waveform diagram of the converter shown in fig. 17 when the input supply voltage drops.
Symbolic names in the above figures: u shapeinIs an input source; cinIs an input bus capacitance; 10 is a primary side switch network; a. b are two output ports of the primary side switch network 10; 20, k is a secondary side full-wave active rectifier switch network, ck、dk、ekThree input ports of a secondary side full-wave active rectification switch network 20, k, wherein k is more than or equal to 1 and less than or equal to n; 30, k is a secondary side full-wave active rectifier switch network, ck、dk、ekThe three input ports of a secondary side rectifier switch network 30 and k are provided, wherein k is more than or equal to n +1 and less than or equal to n + m; l isrIs a resonant inductor; crIs a resonant capacitor; t iskIs a transformer, LmkFor a transformer TkPrimary side excitation inductance of (1)kFor a transformer TkThe turn ratio of the original secondary side is more than or equal to 1 and less than or equal to n + m; s1、S2、S3、S4The first, second, third and fourth switch tubes on the primary side are respectively; dk，1、Dk，2、Dk，3、Dk，4First, second, third and fourth rectifying diodes, S, of a secondary side full-wave active rectifying switch network 20, k, respectivelyk，aFor secondary side full-wave active rectification switching networkAuxiliary switching tube of network 20, k, Sk，s1、Sk，s2A first synchronous rectification switch tube and a second synchronous rectification switch tube of a secondary side full-wave active rectification switch network 20, k, wherein k is more than or equal to 1 and less than or equal to n; dk，3、Dk，4A third rectifying diode and a fourth rectifying diode of a secondary side full-wave rectification switch network 30, k respectively, wherein k is more than or equal to n +1 and less than or equal to n + m; coIs an output filter capacitor; roIs an output load; u shapeoIs the output voltage; i isoIs an output current; m is a voltage gain; f. ofnNormalizing the switching frequency; f. ofnminIs a normalized value of the lowest switching frequency; f. ofnmaxIs the normalized value of the highest switching frequency; i.e. iLrFor flowing through resonant inductor LrThe current of (a); i.e. iLmkExciting inductance L for flowing through transformermkWherein k is more than or equal to 1 and less than or equal to n + m; i.e. iDk，3、iDk，4For flowing through a secondary side full-wave active rectification switch network diode Dk，3、Dk，4Wherein k is more than or equal to 1 and less than or equal to n; u. ofLr、uCrAre respectively Lr、CrThe voltage across; u. ofGS1、uGS2、uGS3、uGS4And uGSk，aAre respectively a switch tube S1、S2、S3、S4And Sk，aK is more than or equal to 1 and less than or equal to n; u. ofabIs the voltage between two ports a and b of the primary side switch network; t is to～t8Is time.
Detailed Description
The technical scheme of the invention is explained in detail with reference to the attached drawings.
As shown in FIG. 4, the full-wave active rectification type LLC resonant converter is composed of an input source UinInput bus capacitor CinPrimary side switch network, resonant inductor LrResonant capacitor CrN + m transformers, n secondary side full-wave active rectification switch networks, m secondary side full-wave rectification switch networks and output filter capacitor CoAnd an output load RoWherein n is more than or equal to 1, m is more than or equal to 0, and transformer TkPrimary side excitation inductance value of Lm，kWherein k is more than or equal to 1 and less than or equal to n + m; the primary side switching networkThe two input ends of the input are respectively connected with an input source UinAre connected with the output end a of the primary side switch network and the resonant inductor LrAre connected to one end of a resonant inductor LrThe other end of the transformer and the transformer T1Transformer T with primary winding connected to the same name terminal1Different name terminal of primary winding and transformer T2The homonymous terminals of the primary windings are connected, and so on, and the transformer Tk-1Different name terminal of primary winding and transformer TkTransformer T with primary winding connected to the same name terminaln+mSynonym terminal and resonant capacitor C of primary windingrIs connected to one end of a resonant capacitor CrThe other end of the primary side switch network is connected with the output end b of the primary side switch network; when k is more than or equal to 1 and less than or equal to n, the transformer TkHomonymous terminal of secondary winding and input terminal c of secondary full-wave active rectification switch networkkConnected to each other, a transformer TkCenter tap of secondary winding and input end d of secondary full-wave active rectifier switch networkkConnected to each other, a transformer TkSynonym terminal of secondary winding and input terminal e of secondary full-wave active rectification switch networkkConnecting; when k is more than or equal to n +1 and less than or equal to n + m, the transformer TkHomonymous terminal of secondary winding and input terminal c of secondary full-wave rectification switch networkkConnected to each other, a transformer TkCenter tap of secondary winding and input end d of secondary full-wave rectification switch networkkConnected to each other, a transformer TkSynonym terminal of secondary winding and input terminal e of secondary full-wave rectification switch networkkThe two output ends of the secondary side full-wave active rectification switch network and the two output ends of the secondary side full-wave rectification switch network are respectively connected with an output filter capacitor CoTwo ends of (1), output load RoTwo ends are connected.
As shown in fig. 5, fig. 6, fig. 7, or fig. 8, the primary side switching network is an asymmetric half-bridge switching network, a symmetric half-bridge switching network, or a full-bridge switching network.
As shown in FIG. 9, the secondary side full-wave active rectification switch network is a common-cathode full-wave active rectification switch network and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A third rectifying diode Dk，3The first stepFour rectifier diodes Dk，4And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a third rectifying diode Dk，3Input end c of anode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Cathode and auxiliary switch tube Sk，aIs connected to the drain of the third rectifying diode Dk，3And a fourth rectifying diode Dk，4Cathode and output filter capacitor CoPositive electrode, output load RoIs connected to the anode of a second rectifying diode Dk，2And a fourth rectifying diode Dk，4Input terminal e of anode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aInput terminal d of the source and secondary full-wave active rectification switch networkkAn output filter capacitor CoNegative electrode of (1), output load RoThe negative electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
As shown in FIG. 10, the secondary side full-wave active rectification switch network is a common-anode full-wave active rectification switch network and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A third rectifying diode Dk，3A fourth rectifying diode Dk，4And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a third rectifying diode Dk，3Input terminal c of cathode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Anode of (2), auxiliary switch tube Sk，aIs connected to the source of the third rectifying diode Dk，3And a fourth rectifying diode Dk，4Anode and output filter capacitor CoNegative electrode of (1), output load RoIs connected to the negative pole of a second rectifier diode Dk，2And a fourth rectifying diode Dk，4Input terminal e of cathode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aDrain electrode and sub-electrode ofInput end d of side full wave active rectification switch networkkAn output filter capacitor CoPositive electrode, output load RoThe positive electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
As shown in FIG. 11, the secondary side full-wave active rectification switch network is a full-wave active rectification switch network with synchronous rectification function and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A first synchronous rectification switch tube Sk，S1A second synchronous rectification switch tube Sk，s2And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a first synchronous rectification switching tube Sk，s1Input terminal c of source and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Cathode and auxiliary switch tube Sk，aIs connected with the drain electrode of the first synchronous rectification switch tube Sk，s1And a second synchronous rectification switching tube Sk，s2Drain electrode of (1), and output filter capacitor CoPositive electrode, output load RoIs connected to the anode of a second rectifying diode Dk，2And a second synchronous rectification switching tube Sk，s2Input terminal e of source electrode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aInput terminal d of the source and secondary full-wave active rectification switch networkkAn output filter capacitor CoNegative electrode of (1), output load RoThe negative electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
As shown in FIG. 12, the secondary side full-wave active rectification switch network is another full-wave active rectification switch network with synchronous rectification function and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A first synchronous rectification switch tube Sk，s1A second synchronous rectification switch tube Sk，s2And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a first synchronous rectification switch tube Sk，s1Input terminal c of the drain electrode and secondary side full-wave active rectification switch networkkAre connected to each other for the first timeCurrent diode Dk，1And a second rectifying diode Dk，2Anode of (2), auxiliary switch tube Sk，aIs connected with the source electrode of the first synchronous rectification switch tube Sk，s1Source electrode of and the second synchronous rectification switch tube Sk，s2Source electrode, output filter capacitor CoNegative electrode of (1), output load RoIs connected to the negative pole of a second rectifier diode Dk，2And a second synchronous rectification switch tube Sk，s2Input terminal e of drain electrode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aDrain and secondary side full wave active rectification switch network input terminal dkAn output filter capacitor CoPositive electrode, output load RoThe positive electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
As shown in fig. 13, 14, 15 or 16, the secondary side full-wave rectification switch network is a full-wave rectification switch network or a full-wave rectification switch network with a synchronous rectification function.
The control strategy of the full-wave active rectification type LLC resonant converter is that when the input voltage is near a rated working point, the auxiliary switching tube is kept closed, the output voltage is kept constant by adjusting the switching frequency of a primary side switching network of the converter, and the converter works near a resonant frequency point.
The control strategy of the full-wave active rectification type LLC resonant converter is that when input voltage drops and output voltage cannot be maintained through frequency conversion control, an auxiliary switching tube adopts a pulse width modulation strategy, the converter fixedly works at a resonant frequency point, and the output voltage is maintained to be constant by increasing the duty ratio of the auxiliary switching tube. Firstly, the auxiliary switch tube S is increased1，aThe duty ratio of (1) to maintain the output voltage constant; as an auxiliary switch tube Sk，aWhen the duty ratio reaches 1, the auxiliary switch tube S is increasedk+1，aDuty cycle of (d); if the number m of the secondary side full-wave rectification switch networks is 0, the duty ratio of the nth secondary side full-wave active rectification switch network is required to be less than 1; if the number m of the secondary side full-wave rectification switch networks is more than or equal to 1, the duty ratio of the nth secondary side full-wave active rectification switch network can reach the maximum duty ratio1。
The invention aims to realize high-efficiency and high-power-density isolated direct current conversion in a power-down maintaining occasion, and in order to realize the purpose, the invention adopts a full-wave active rectification switch network mode to widen the input voltage range of a converter. According to the invention, an auxiliary active switching tube is introduced into a traditional LLC secondary side full-wave rectification switching network, the resonant frequency point is fixedly operated in a power-down holding mode, pulse width modulation is adopted, and a converter has a specific working mode, namely a voltage gain shown in a formula (1). The working mode greatly reduces the requirement on the peak gain of the converter working in a frequency conversion mode, the efficiency of the converter can be obviously improved by optimizing the parameters of the resonant cavity, the capacitance of the input bus is reduced, and the requirement on power failure holding occasions is met.
The working principle of the present invention will be described below by taking as an example a full-wave active rectification type LLC resonant converter with a primary side switching network 10 shown in fig. 17, which employs an asymmetric half-bridge switching network, a full-wave active rectification switching network with only one common cathode on the secondary side, and no secondary side full-wave rectification switching network. When the input voltage is near the normal rated point, the auxiliary switch tube S1，aKeeping the converter off, the converter adopts the conventional frequency conversion control, the working principle and the characteristics are the same as those of the traditional LLC, and the working waveform is shown in the attached figure 2 and is not described in detail here.
Fig. 18 shows a typical operating waveform of the present invention when the input power is turned off. In FIG. 18, the first switching tube S on the primary side of the converter1Drive uGS1And a second switching tube S2Drive uGS2Is a square wave with a duty ratio of 50 percent and is complementarily conducted. Rectangular wave voltage u output by switching network 10abPositive pulse amplitude of UinNegative pulse amplitude of 0, uabThe positive and negative pulse widths were both 50%.
t0Before the moment, the second switch tube S on the primary side2Auxiliary switch tube S1，aIn the on state, the inductor L is excitedm，1Short-circuited, resonant inductor LrAnd a resonance capacitor CrAnd (4) resonating. Secondary side third, fourth rectifier diode D1，3And D1，4Are all in the reverse blocking state.
t0Second switch tube S on primary side2Off, resonant current iLrFor the first switching tube S on the primary side1The parasitic capacitor discharges and simultaneously gives the second switch tube S on the primary side2The parasitic capacitance is charged. The secondary current flows through the secondary first rectifier diode D1，1And an auxiliary switching tube S1，a. Due to the transformer T1Has a secondary side voltage of 0 and an excitation current iLmRemain unchanged. Resonant inductor LrAnd a resonance capacitor CrResonant, output filter capacitor CoTo the output load R aloneoSupply of power, t0～t1The modal equivalent circuit over the time period is shown in figure 21.
t1First switch tube S on primary side1Switch-on and auxiliary switch tube SaKeeping on, and secondary side third and fourth rectifier diodes D1，3And D1，4Still in the reverse blocking state. Resonant inductor LrContinuing to resonate the capacitor CrResonance, resonant current iLrRising rapidly from input source UinAbsorbing energy, and flowing secondary current through the first and second rectifier diodes D1，1、D1，2And an auxiliary switching tube S1，a. Due to the transformer T1Has a secondary side voltage of 0 and an excitation current imRemain unchanged. Output filter capacitor CoTo the output load RoSupply power until t2Time auxiliary switch tube S1，aIs turned off. t is t1～t2The modal equivalent circuit over the time period is shown in figure 22.
t2Time of day, auxiliary switch tube S1，aTurn-off, secondary side third rectifier diode D1，3On, the transformer is output with voltage UoClamping, current iLmAnd (4) increasing linearly. In this mode, the resonant inductance LrAnd a resonance capacitor CrResonant with the input source UinCommon direction load RoProviding energy. t is t2～t3The modal equivalent circuit over the time period is shown in figure 23.
t3Time of day, auxiliary switch tube S1，aThird and fourth rectifying diodes D on turn-on and secondary side1，3And D1，4Reverse cut-off, primary side first switch tube S1Remain on. Resonant inductor LrContinuing to resonate the capacitor CrResonant from an input source UinAbsorbing energy, and flowing secondary current through the first and second rectifier diodes D1，1、D1，2And an auxiliary switching tube S1，a. Transformer T1Has a secondary side voltage of 0 and an excitation current iLmRemain unchanged. Output filter capacitor CoTo the output load RoAnd (5) supplying power. t is t3～t4Working process and t in time period1～t2The time periods are the same and the modal equivalent circuit is shown in figure 22.
t4First switch tube S on primary side1And turning off, starting the next half of the switching period, and working processes are similar and are not described repeatedly.
During the whole operation of FIG. 18, the resonant capacitor CrThe DC bias voltage is an input power supply UinHalf of U ofin/2. Assumed excitation inductance LmInfinity, the excitation current is constantly equal to 0, and the converter voltage gain at the moment is derived by adopting a time domain analysis method, as shown in formula (1).
Transformer T1After the secondary side introduces active rectification, the voltage gain range of the converter shown in fig. 17 is obviously expanded, and as shown in fig. 24, a wider working range can be achieved. In comparison with the converter of the prior art document, the transformer T of the converter shown in fig. 171The transformer works in a symmetrical state, no magnetic bias exists, and the structure of the transformer is simpler.
As shown in fig. 25, it can be seen from the diagram that after the converter shown in fig. 17 introduces active rectification to the secondary side, the working range of the input voltage of the converter can be effectively widened, and the working process is consistent with that of theoretical analysis.
FIG. 19 shows a full-wave active rectification LLC resonance with synchronous rectificationThe operation of the converter is similar to that of the converter shown in fig. 17, except that the third and fourth rectifying diodes D in fig. 171，3、D1，4By replacing the first and second synchronous rectification switching tubes S in FIG. 191，s1、S1，s2The converter operates in the synchronous rectification mode, so that the efficiency of the converter can be further improved, and the operating waveform of the converter is shown in fig. 20 and is not described herein.
According to the description of the above embodiments, compared with the converter in the prior document, the transformer of the present invention operates in a symmetrical state, has no magnetic bias, and has a simple structure; the method can meet two requirements of a power supply system for maintaining the efficiency of a steady-state working point and the transient voltage drop, overcomes the defect that the traditional variable frequency control LLC resonant converter cannot give consideration to the steady-state efficiency and the transient voltage regulation capability, and is particularly suitable for application occasions requiring the power supply system to have the power failure maintaining capability, such as a server power supply and a rail transit power supply.
The above description of the present invention is intended to be illustrative. Various modifications, additions and substitutions for the specific embodiments described may be made by those skilled in the art without departing from the scope of the invention as defined in the accompanying claims.

Claims (8)

1. A full-wave active rectification type LLC resonant converter and a control strategy thereof are characterized in that:
the full-wave active rectification type LLC resonant converter is composed of an input source UinInput bus capacitor CinPrimary side switch network, resonant inductor LrResonant capacitor CrN + m transformers, n secondary side full-wave active rectification switch networks, m secondary side full-wave rectification switch networks and output filter capacitor CoAnd an output load RoWherein n is more than or equal to 1, m is more than or equal to 0, and transformer TkPrimary side excitation inductance value of Lm，kWherein k is more than or equal to 1 and less than or equal to n + m; the two input ends of the primary side switching network are respectively connected with an input source UinAre connected with the output end a of the primary side switch network and the resonant inductor LrAre connected to one end of a resonant inductor LrThe other end of the transformer and the transformer T1Transformer T with primary winding connected to the same name terminal1Different name terminal of primary winding and transformer T2The homonymous terminals of the primary windings are connected, and so on, and the transformer Tk-1Different name terminal of primary winding and transformer TkTransformer T with primary winding connected to the same name terminaln+mSynonym terminal and resonant capacitor C of primary windingrIs connected to one end of a resonant capacitor CrThe other end of the primary side switch network is connected with the output end b of the primary side switch network; when k is more than or equal to 1 and less than or equal to n, the transformer TkHomonymous terminal of secondary winding and input terminal c of secondary full-wave active rectification switch networkkConnected to each other, a transformer TkCenter tap of secondary winding and input end d of secondary full-wave active rectifier switch networkkConnected to each other, a transformer TkSynonym terminal of secondary winding and input terminal e of secondary full-wave active rectification switch networkkConnecting; when k is more than or equal to n +1 and less than or equal to n + m, the transformer TkHomonymous terminal of secondary winding and input terminal c of secondary full-wave rectification switch networkkConnected to each other, a transformer TkCenter tap of secondary winding and input end d of secondary full-wave rectification switch networkkConnected to each other, a transformer TkSynonym terminal of secondary winding and input terminal e of secondary full-wave rectification switch networkkThe two output ends of the secondary side full-wave active rectification switch network and the two output ends of the secondary side full-wave rectification switch network are respectively connected with an output filter capacitor CoTwo ends of (1), output load RoTwo ends are connected;
an auxiliary switch tube S in the secondary side full-wave active rectification switch network when the input voltage is near the rated working pointk，aKeeping the switching-off, keeping the output voltage constant by adjusting the switching frequency of a primary side switching network of the converter, and enabling the converter to work near a resonant frequency point; when the input voltage drops and the output voltage can not be maintained through the frequency conversion control, the auxiliary switch tube Sk，aThe converter fixedly works at a resonant frequency point by adopting a pulse width modulation strategy and increasing an auxiliary switching tube Sk，aDuty ratio ofKeeping the output voltage constant, wherein k is more than or equal to 1 and less than or equal to n.
2. A full wave active rectification type LLC resonant converter and control strategy thereof as claimed in claim 1, wherein: the primary side switch network is an asymmetric half-bridge switch network, or a symmetric half-bridge switch network, or a full-bridge switch network.
3. A full wave active rectification type LLC resonant converter and control strategy thereof as claimed in claim 1, wherein: the secondary side full-wave active rectification switch network is a common-cathode full-wave active rectification switch network and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A third rectifying diode Dk，3A fourth rectifying diode Dk，4And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a third rectifying diode Dk，3Input end c of anode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Cathode and auxiliary switch tube Sk，aIs connected to the drain of the third rectifying diode Dk，3And a fourth rectifying diode Dk，4Cathode and output filter capacitor CoPositive electrode, output load RoIs connected to the anode of a second rectifying diode Dk，2And a fourth rectifying diode Dk，4Input terminal e of anode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aInput terminal d of the source and secondary full-wave active rectification switch networkkAn output filter capacitor CoNegative electrode of (1), output load RoThe negative electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
4. A full wave active rectification type LLC resonant converter and control strategy thereof as claimed in claim 1, wherein: the secondary side full-wave active rectification switch network is a common-positive full-wave active rectification switch network consisting ofFirst rectifying diode Dk，1A second rectifying diode Dk，2A third rectifying diode Dk，3A fourth rectifying diode Dk，4And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a third rectifying diode Dk，3Input terminal c of cathode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Anode of (2), auxiliary switch tube Sk，aIs connected to the source of the third rectifying diode Dk，3And a fourth rectifying diode Dk，4Anode and output filter capacitor CoNegative electrode of (1), output load RoIs connected to the negative pole of a second rectifier diode Dk，2And a fourth rectifying diode Dk，4Input terminal e of cathode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aDrain and secondary side full wave active rectification switch network input terminal dkAn output filter capacitor CoPositive electrode, output load RoThe positive electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
5. A full wave active rectification type LLC resonant converter and control strategy thereof as claimed in claim 1, wherein: the secondary side full-wave active rectification switch network is a full-wave active rectification switch network with a synchronous rectification function and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A first synchronous rectification switch tube Sk，s1A second synchronous rectification switch tube Sk，s2And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a first synchronous rectification switching tube Sk，s1Input terminal c of source and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Cathode and auxiliary switch tube Sk，aIs connected with the drain electrode of the first synchronous rectification switch tube Sk，s1And a second synchronous rectification switching tube Sk，s2Drain electrode of (1), and output filter capacitor CoPositive electrode, output load RoIs connected to the anode of a second rectifying diode Dk，2And a second synchronous rectification switching tube Sk，s2Input terminal e of source electrode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aInput terminal d of the source and secondary full-wave active rectification switch networkkAn output filter capacitor CoNegative electrode of (1), output load RoThe negative electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
6. A full wave active rectification type LLC resonant converter and control strategy thereof as claimed in claim 1, wherein: the secondary side full-wave active rectification switch network is another full-wave active rectification switch network with synchronous rectification function and is composed of a first rectification diode Dk，1A second rectifying diode Dk，2A first synchronous rectification switch tube Sk，s1A second synchronous rectification switch tube Sk，s2And an auxiliary switching tube Sk，aIs composed of a first rectifying diode Dk，1And a first synchronous rectification switch tube Sk，s1Input terminal c of the drain electrode and secondary side full-wave active rectification switch networkkConnected, a first rectifier diode Dk，1And a second rectifying diode Dk，2Anode of (2), auxiliary switch tube Sk，aIs connected with the source electrode of the first synchronous rectification switch tube Sk，s1Source electrode of and the second synchronous rectification switch tube Sk，s2Source electrode, output filter capacitor CoNegative electrode of (1), output load RoIs connected to the negative pole of a second rectifier diode Dk，2And a second synchronous rectification switch tube Sk，s2Input terminal e of drain electrode and secondary side full-wave active rectification switch networkkConnected with an auxiliary switch tube Sk，aDrain and secondary side full wave active rectification switch network input terminal dkAn output filter capacitor CoPositive electrode, output load RoThe positive electrodes are connected, wherein k is more than or equal to 1 and less than or equal to n.
7. A full wave active rectification type LLC resonant converter and control strategy thereof as claimed in claim 1, wherein: the secondary side full-wave rectification switch network is a full-wave rectification switch network or a full-wave rectification switch network with a synchronous rectification function.
8. A full wave active rectification type LLC resonant converter and control strategy thereof as claimed in claim 1, wherein: when the input voltage drops and the output voltage can not be maintained through the frequency conversion control, the auxiliary switch tube S is firstly increased1，aThe duty ratio of (1) to maintain the output voltage constant; as an auxiliary switch tube Sk-1，aWhen the duty ratio reaches 1, the auxiliary switch tube S is increasedk，aWherein k is more than or equal to 1 and less than or equal to n; if the number m of the secondary side full-wave rectification switch networks is 0, the duty ratio of the nth secondary side full-wave active rectification switch network is required to be less than 1; if the number m of the secondary side full-wave rectification switch networks is larger than or equal to 1, the maximum duty ratio of the nth secondary side full-wave active rectification switch network is 1.
CN201811233483.4A 2018-10-18 2018-10-18 Full-wave active rectification type LLC resonant converter and control strategy thereof Expired - Fee Related CN109302071B (en)

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