CN112332674A - LLC resonant converter and wide gain control method - Google Patents
LLC resonant converter and wide gain control method Download PDFInfo
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- CN112332674A CN112332674A CN202011174959.9A CN202011174959A CN112332674A CN 112332674 A CN112332674 A CN 112332674A CN 202011174959 A CN202011174959 A CN 202011174959A CN 112332674 A CN112332674 A CN 112332674A
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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
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/4815—Resonant converters
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- 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 wide gain control method of an LLC resonant converter, which comprises the steps of dividing an input voltage range into two voltage sections, using two control modes, adopting a full-bridge LLCPFM control mode in a low-voltage section of the input voltage range, and changing output voltage gain by changing switching frequency; in the high-voltage section of the input voltage range, a full-bridge LLC variable duty ratio control mode is adopted, in the whole high-voltage section range, the switching frequency is equal to the resonance frequency fr, and the output voltage gain is changed by changing the duty ratio of a primary side switching tube. The invention also discloses an LLC resonant converter using the control method. The invention can realize smooth switching between modes, improve the working efficiency, the gain range and the power density of the converter and meet the requirement of wide voltage gain range conversion occasions.
Description
Technical Field
The invention relates to the field of switching converters, in particular to an LLC resonant converter and a control method for realizing wide gain.
Background
With the rapid development of the power electronic field, the application of the switching converter is more and more extensive. More requirements are put on switching converters: high power density, high reliability, high efficiency, small volume, wide input voltage range. An LLC resonant converter, as a resonant converter, has many advantages, such as low noise, low stress, low switching losses, etc. However, the conventional LLC resonant converter generally needs to adjust the output voltage by changing the switching frequency, when the input voltage range is wide, the switching frequency needs to be changed in a wide range, when the frequency is too low, it is difficult to achieve zero-voltage turn-on, and when the frequency is too high, it is difficult to achieve zero-current turn-off; meanwhile, the wider frequency brings great difficulty to the design of the transformer and the control of the circuit. Therefore, when the operating frequency variation range is wide, the efficiency of the conventional LLC resonant converter is significantly reduced.
Many researchers study to improve the gain of the LLC resonant converter by changing the control mode, and widen the range of the input voltage thereof.
A paper, LLC circuit applied to ultra-wide input range, was published in 2013 by lao political feast et al, which doubles the circuit gain by using a full-bridge LLC frequency conversion control mode in the low-voltage section and a half-bridge LLC frequency conversion control mode in the high-voltage section, but the working states of the circuit before and after the control mode switching differ greatly, and smooth switching is difficult to achieve.
"research on variable mode control LLC in small-sized photovoltaic grid-connected inverter" by the thesis of chessman university in 2016, an FBLLC frequency conversion control mode is adopted when the input voltage is in a low-voltage section, a full-bridge LLC fixed-frequency control mode is adopted when the input voltage is in a medium-voltage section, and a half-bridge LLC frequency conversion control mode is adopted when the input voltage is in a high-voltage section, but this three-mode scheme still cannot achieve smooth switching between the two modes, full-bridge LLC fixed-frequency control mode and half-bridge LLC frequency conversion control mode.
Patent application No. CN201910859317 discloses a tri-modal control scheme that can achieve smooth switching between two adjacent voltage segments, but the control scheme is complex and difficult to achieve smooth switching when the variation of the input voltage crosses three voltage segments.
Disclosure of Invention
In view of the above, the technical problems to be solved by the present invention are: the LLC resonant converter and the wide gain control method thereof can improve the voltage gain range of the converter and enable the control mode to be switched simply and reliably.
In order to achieve the above purpose, the technical solutions provided by the embodiments of the present invention are as follows:
a wide gain control method of LLC resonant converter, through dividing the input voltage range into low and high two voltage sections, correspond to two kinds of control modes separately, in the low-voltage section of the input voltage range, adopt the full-bridge LLC PFM control mode, change the gain of output voltage through changing the switching frequency; in the high-voltage section of the input voltage range, a full-bridge LLC variable duty ratio control mode is adopted, in the whole high-voltage section range, the switching frequency is equal to the resonance frequency fr, and the output voltage gain is changed by changing the duty ratio of a primary side switching tube.
Preferably, the voltage switching point setting between the two control modalities should satisfy: when the input voltage rises to be higher than the modal switching voltage, namely the switching frequency is equal to the corresponding voltage V _ fr when the resonant frequency fr, the LLC resonant converter enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode; the input voltage is reduced to be lower than the modal switching voltage, namely the corresponding voltage V _ fr when the switching frequency is equal to the resonant frequency fr, and the LLC resonant converter enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
Preferably, the switching mode of the two control modes is as follows: after the switching frequency is increased to be equal to the resonance frequency fr, the switching frequency is stabilized at the value, the duty ratio of the primary side switching tube is gradually reduced to be stable, and the control mode enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode; after the duty ratio of the primary side switching tube is increased to be equal to 50%, the duty ratio of the primary side switching tube is stabilized at the value, the switching frequency is gradually reduced to be stable, and the control mode enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
The invention also provides an LLC resonant converter, which comprises an input source Vin, a primary side LLC resonant circuit, a transformer T and a secondary side rectification filtering output circuit, wherein the LLC resonant converter has two control modes and is suitable for different stages: dividing an input voltage range into a low voltage section and a high voltage section, and changing output voltage gain by changing switching frequency in the low voltage section of the input voltage range by adopting a full-bridge LLC PFM control mode; in the high-voltage section of the input voltage range, a full-bridge LLC variable duty ratio control mode is adopted, in the whole high-voltage section range, the switching frequency is equal to the resonance frequency fr, and the output voltage gain is changed by changing the duty ratio of a primary side switching tube.
Preferably, the voltage switching point setting between the full-bridge LLC PFM control mode and the full-bridge LLC variable duty cycle control mode should satisfy: when the input voltage rises to be higher than the modal switching voltage, namely the switching frequency is equal to the corresponding voltage V _ fr when the resonant frequency fr, the LLC resonant converter enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode; the input voltage is reduced to be lower than the modal switching voltage, namely the corresponding voltage V _ fr when the switching frequency is equal to the resonant frequency fr, and the LLC resonant converter enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
Preferably, the switching mode between the full-bridge LLC PFM control mode and the full-bridge LLC variable duty cycle control mode is: after the off frequency is increased to be equal to the resonant frequency fr, the switching frequency is stabilized at the value, the duty ratio of the primary side switching tube is gradually reduced to be stable, and the control mode enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode; after the duty ratio of the primary side switching tube is increased to be equal to 50%, the duty ratio of the primary side switching tube is stabilized at the value, the switching frequency is gradually reduced to be stable, and the control mode enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
As a specific embodiment of the primary LLC resonant circuit, the resonant circuit comprises a primary switch tube S1, a primary switch tube S2, a primary switch tube S3, a primary switch tube S4, a primary switch tube S5, a primary switch tube S6, a resonant capacitor Cr, a resonant inductor Lr and a magnetizing inductor Lm, wherein a drain of the primary switch tube S1 is connected to a drain of the primary switch tube S2 and a positive terminal of an input source Vin, a source of the primary switch tube S1 is connected to a drain of the primary switch tube S3 and a terminal of the resonant capacitor Cr, the other terminal of the resonant capacitor Cr is connected to one terminal of the resonant inductor Lr and a drain of the primary switch tube S5, a source of the primary switch tube S5 is connected to a source of the primary switch tube S6, the other terminal of the resonant inductor Lr is connected to a terminal of the magnetizing inductor and a terminal of a transformer T winding Np, a non-dotted terminal of the transformer T winding LmNp is connected to the other terminal of the magnetizing inductor Lm, and a source of the inductor S2, The drain electrode of the primary side switching tube S4, the drain electrode of the primary side switching tube S6 and the source electrode of the primary side switching tube S4 are connected with the source electrode of the primary side switching tube S3 and the negative electrode of the input source Vin.
As another embodiment of the primary LLC resonant circuit, the primary LLC resonant circuit comprises a primary switch tube S1, a primary switch tube S2, a primary switch tube S3, a primary switch tube S4, a primary switch tube S5, a primary switch tube S6, a resonant capacitor Cr, a resonant inductor Lr and a magnetizing inductor Lm, wherein a drain of the primary switch tube S1 is connected to a drain of the primary switch tube S2 and a positive terminal of an input source Vin, a source of the primary switch tube S1 is connected to a drain of the primary switch tube S3 and a terminal of the resonant capacitor Cr, another terminal of the resonant capacitor Cr is connected to one terminal of the resonant inductor Lr and a source of the primary switch tube S6, a drain of the primary switch tube S6 is connected to a drain of the primary switch tube S5, another terminal of the resonant inductor Lr is connected to a primary terminal of the magnetizing inductor and a primary terminal of a transformer T winding Np, a non-dotted terminal of the transformer T winding Lmp is connected to another terminal of the magnetizing inductor Lm, and a source of the transformer T2, The drain electrode of the primary side switching tube S4 and the source electrode of the primary side switching tube S5, and the source electrode of the primary side switching tube S4 are connected to the source electrode of the primary side switching tube S3 and the negative electrode of the input source Vin.
Preferably, the full-bridge LLC PFM control modality is: the switching frequencies of the primary side switching tubes S1-S4 are equal but not fixed, the primary side switching tube S1 and the primary side switching tube S2 are conducted complementarily, the primary side switching tube S1 and the primary side switching tube S4 are conducted and turned off simultaneously, the primary side switching tube S2 and the primary side switching tube S3 are conducted and turned off simultaneously, the primary side switching tube S5 and the primary side switching tube S6 are always in a turned-off state, the control of output voltage is achieved by adjusting the switching frequencies of the primary side switching tubes S1-S4, and the larger the switching frequency is, the smaller the gain of the output voltage is.
Preferably, the full-bridge LLC variable duty cycle control mode is: switching frequencies of the primary side switching tubes S1 to S6 are equal and fixed, the primary side switching tube S1 and the primary side switching tube S5 are in complementary conduction, the primary side switching tube S2 and the primary side switching tube S6 are in complementary conduction, the primary side switching tube S1 and the primary side switching tube S4 are in conduction and off simultaneously, the primary side switching tube S2 and the primary side switching tube S3 are in conduction and off simultaneously, the duty ratio of the primary side switching tube S1 is equal to that of the primary side switching tube S2, not more than 50% and 180% of phase difference between the primary side switching tube S2 and the primary side switching tube S5, the duty ratio of the primary side switching tube S5 is equal to that of the primary side switching tube S6, not less than 50% and 180% of phase difference between the primary side switching tube S2, control over voltage is achieved by adjusting the duty ratio of the primary side.
Advantageous effects
1. According to the invention, through the circuit switch setting, the output voltage gain can be changed by changing the switching frequency or the duty ratio, and the voltage gain range of the converter is improved;
2. according to the invention, the method that the low-voltage section of the input voltage range adopts a full-bridge LLC PFM control mode and the high-voltage section of the input voltage range adopts a full-bridge LLC variable duty ratio control mode is adopted, so that the number of control modes is simplified, and the control modes are switched simply and reliably.
Drawings
FIG. 1 is a diagram of an LLC resonant converter circuit of the invention;
fig. 2 is a waveform diagram of the circuit state of the LLC resonant converter of the present invention before and after mode switching.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings. The circuit structure of the LLC resonant converter is shown in figure 1 and comprises an input source Vin, a primary LLC resonant circuit, a transformer T, a secondary rectifying circuit and an output load Ro, wherein the primary LLC resonant circuit consists of a primary switching tube S1, a primary switching tube S2, a primary switching tube S3, a primary switching tube S4, a primary switching tube S5, a primary switching tube S6, a resonant capacitor Cr, a resonant inductor Lr and an excitation inductor Lm, and the secondary rectifying circuit consists of a secondary rectifying diode D1, a secondary rectifying diode D2, a secondary rectifying diode D3, a secondary rectifying diode D4 and a secondary output filter capacitor Co;
the drain electrode of a primary side switch tube S1 is connected with the drain electrode of a primary side switch tube S2 and the positive end of an input source Vin, the source electrode of the primary side switch tube S1 is connected with the drain electrode of a primary side switch tube S3 and one end of a resonant capacitor Cr, the other end of the resonant capacitor Cr is connected with one end of a resonant inductor Lr and the drain electrode of a primary side switch tube S5, the source electrode of a primary side switch tube S5 is connected with the source electrode of a primary side switch tube S6, the other end of the resonant inductor Lr is connected with one end of a magnetizing inductor Lm and the same name end of a primary side winding Np of a transformer T, the non-same name end of the primary side winding Np of the transformer T is connected with the other end of the magnetizing inductor Lm, the source electrode of a primary side switch tube S2, the drain electrode of a primary side switch tube S4 and the drain electrode of a primary side switch tube S;
the anode of the secondary rectifier diode D1 is connected to the dotted terminal of the secondary winding Ns of the transformer T and the cathode of the secondary rectifier diode D3, the cathode of the secondary rectifier diode D1 is connected to the cathode of the secondary rectifier diode D2, one end of the capacitor Co and one end of the output load Ro, the anode of the secondary rectifier diode D2 is connected to the non-dotted terminal of the secondary winding Ns of the transformer T and the cathode of the secondary rectifier diode D4, and the anode of the secondary rectifier diode D4 is connected to the anode of the secondary rectifier diode D3, the other end of the capacitor Co and the other end of the output load Ro.
The input voltage range is divided into a low voltage section and a high voltage section which respectively correspond to two control modes:
in a low-voltage section of an input voltage range, the LLC resonant converter adopts a full-bridge LLC PFM control mode, and the output voltage gain is changed by changing the switching frequency; there is a minimum switching frequency fmin at the minimum input voltage of the low-voltage section, a maximum switching frequency fmax at the maximum input voltage of the low-voltage section, and the maximum switching frequency fmax is ideally the resonance frequency fr of the LLC resonant converter.
The working process of the LLC resonant converter adopting the full-bridge LLC PFM control mode is as follows:
the switching frequencies from the primary side to the switching tubes S1-S4 are equal but not fixed, the primary side switching tube S1 and the primary side switching tube S2 are conducted complementarily, the primary side switching tube S1 and the primary side switching tube S4 are conducted and turned off simultaneously, the primary side switching tube S2 and the primary side switching tube S3 are conducted and turned off simultaneously, the primary side switching tube S5 and the primary side switching tube S6 are always in a turned-off state, the control of output voltage is achieved by adjusting the switching frequency from the primary side to the switching tubes S1-S4, and the larger the switching frequency is, the smaller the gain of the output voltage is.
In the high-voltage section of the input voltage range, the LLC resonant converter adopts a full-bridge LLC variable duty ratio control mode, in the whole high-voltage section range, the switching frequency is equal to the resonant frequency fr, the output voltage gain is changed by changing the duty ratio of the switching tube S1, the maximum duty ratio Dmax is arranged at the minimum input voltage of the high-voltage section, and the minimum duty ratio Dmin is arranged at the maximum input voltage of the high-voltage section.
The working process of the LLC resonant converter adopting the LLC variable duty ratio control mode is as follows:
switching frequencies of the primary side switching tubes S1 to S6 are equal and fixed, the primary side switching tube S1 and the primary side switching tube S5 are in complementary conduction, the primary side switching tube S2 and the primary side switching tube S6 are in complementary conduction, the primary side switching tube S1 and the primary side switching tube S4 are in conduction and off simultaneously, the primary side switching tube S2 and the primary side switching tube S3 are in conduction and off simultaneously, the duty ratio of the primary side switching tube S1 is equal to that of the primary side switching tube S2, not more than 50% and 180% of phase difference between the primary side switching tube S2 and the primary side switching tube S5, the duty ratio of the primary side switching tube S5 is equal to that of the primary side switching tube S6, not less than 50% and 180% of phase difference between the primary side switching tube S2, control over voltage is achieved by adjusting the duty ratio of the primary side.
When the input voltage changes between the low-voltage section and the high-voltage section, the switching of control modes is involved, namely the switching between a full-bridge LLC PFM control mode and a full-bridge LLC variable duty ratio control mode of the LLC resonant converter. When the input voltage rises to be higher than the modal switching voltage, namely the switching frequency is equal to the resonant frequency fr, the corresponding voltage V _ fr, the LLC resonant converter enters a full-bridge LLC variable duty ratio control mode, the control mode switching mode is that the maximum switching frequency fmax of the full-bridge LLC PFM control mode is equal to the resonant frequency fr and is kept, and the duty ratio is gradually reduced to be stable after the switching frequency is increased to be equal to the resonant frequency fr; when the input voltage is reduced to be lower than the mode switching voltage, namely the corresponding voltage V _ fr when the switching frequency is equal to the resonance frequency fr, the LLC resonant converter enters a full-bridge LLC PFM control mode, the mode switching mode is controlled in a manner that the maximum duty ratio Dmax is equal to 50% and is kept, and the switching frequency is gradually reduced to be stable after the duty ratio is increased to be equal to 50%.
The maximum switching frequency fmax of the full-bridge LLC PFM control mode is close to the resonance frequency fr as much as possible, the maximum duty ratio Dmax of the full-bridge LLC variable duty ratio control mode is close to 50% as much as possible, smooth switching between the full-bridge LLC PFM control mode and the full-bridge LLC variable duty ratio control mode of the LLC resonant converter can be realized, and the converter is high in efficiency in a working range.
Fig. 2 is a waveform diagram of the circuit operation state of the LLC resonant converter (left diagram in fig. 2) when the input voltage rises to reach the mode switching voltage V _ fr in the low-voltage stage and a waveform diagram of the circuit operation state when the input voltage drops to reach the mode switching voltage V _ fr in the high-voltage stage (right diagram in fig. 2). Vgs1 is a driving signal of a primary side switching tube S1, Vgs2 is a driving signal of a primary side switching tube S2, Vgs3 is a driving signal of a primary side switching tube S3, Vgs4 is a driving signal of a primary side switching tube S4, Vgs5 is a driving signal of a primary side switching tube S5, Vgs6 is a driving signal of a primary side switching tube S6, VAB is a resonant cavity voltage, VCr is a resonant capacitor Cr voltage, ILr is a resonant current, ILm is an excitation current, because working waveforms of a primary side switching tube S1 driving signal Vgs1, a primary side switching tube S2 driving signal Vgs2, a primary side switching tube S3 driving signal Vgs3, a primary side switching tube S4 driving signal Vgs4, a resonant capacitor voltage, a resonant cavity voltage VAB, a resonant current ILr and an excitation current ILm of two control modes are basically the same, only a primary side switching tube S5 driving signal Vgs5 and a primary side switching tube S5 are different, and a primary side switching tube S5 is in series connection with each other switching tube 5, the driving signal Vgs5 of the primary side switching tube S5 and the driving signal Vgs6 of the primary side switching tube S6 do not simultaneously enable the primary side switching tube S5 and the primary side switching tube S6 to be conducted, and a series branch formed by the primary side switching tube S5 and the primary side switching tube S6 before and after switching is disconnected, so smooth switching can be achieved between the two modes at the time.
The primary side switch tube S5 and the primary side switch tube S6 can be interchanged in position, and the effect is the same.
Specifically, when the actual mode switching voltage V _ fr1 is implemented to the product, the actual mode switching voltage V _ fr1 may be slightly larger than or slightly smaller than the voltage V _ fr corresponding to the switching frequency fr, and correspondingly, the actual value of the "resonant frequency fr" in the switching mode may be slightly larger than or slightly smaller than the resonant frequency fr, so as to ensure stable operation of the LLC resonant converter.
According to the description of the working process of the converter, the converter adopts different control modes in two voltage range sections, the working states of the circuit are basically the same before and after mode switching, and smooth switching between the modes is easy to realize. In addition, the converter can improve the voltage gain range, efficiency and power density and meet the requirement of wide voltage gain conversion occasions.
The above description of the embodiments is only for helping understanding the inventive concept of the present application, and is not intended to limit the present invention, the secondary side rectifying and filtering output circuit of the LLC resonant converter may be a full-wave rectifying structure; each rectifier diode in the secondary side rectifier filter output circuit can be replaced by a selective switch tube; the 50% duty ratio is to omit dead zones for simplifying expression, and the dead zones are considered in specific implementation, so that the duty ratio is properly reduced; it will be understood by those skilled in the art that various changes, substitutions of equivalents, and alterations can be made without departing from the spirit and scope of the invention.
Claims (10)
1. A wide gain control method of an LLC resonant converter is characterized in that: by dividing the input voltage range into two voltage sections, low and high, corresponding to two control modes,
in a low-voltage section of an input voltage range, a full-bridge LLC PFM control mode is adopted, and the output voltage gain is changed by changing the switching frequency;
in the high-voltage section of the input voltage range, a full-bridge LLC variable duty ratio control mode is adopted, in the whole high-voltage section range, the switching frequency is equal to the resonance frequency fr, and the output voltage gain is changed by changing the duty ratio of a primary side switching tube.
2. The wide gain control method of the LLC resonant converter as claimed in claim 1, wherein: the voltage switching point setting between the two control modes is to meet the following conditions: when the input voltage rises to be higher than the modal switching voltage, namely the switching frequency is equal to the corresponding voltage V _ fr when the resonant frequency fr, the LLC resonant converter enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode; the input voltage is reduced to be lower than the modal switching voltage, namely the corresponding voltage V _ fr when the switching frequency is equal to the resonant frequency fr, and the LLC resonant converter enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
3. The wide gain control method of the LLC resonant converter as claimed in claim 1, wherein:
the switching mode of the two control modes is as follows:
after the switching frequency is increased to be equal to the resonance frequency fr, the switching frequency is stabilized at the value, the duty ratio of the primary side switching tube is gradually reduced to be stable, and the control mode enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode;
after the duty ratio of the primary side switching tube is increased to be equal to 50%, the duty ratio of the primary side switching tube is stabilized at the value, the switching frequency is gradually reduced to be stable, and the control mode enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
4. The LLC resonant converter comprises an input source Vin, a primary LLC resonant circuit, a transformer T and a secondary rectification filter output circuit, and is characterized in that:
there are two control modes of the LLC resonant converter, and are applicable to different phases: dividing an input voltage range into a low voltage section and a high voltage section, and changing output voltage gain by changing switching frequency in the low voltage section of the input voltage range by adopting a full-bridge LLC PFM control mode; in the high-voltage section of the input voltage range, a full-bridge LLC variable duty ratio control mode is adopted, in the whole high-voltage section range, the switching frequency is equal to the resonance frequency fr, and the output voltage gain is changed by changing the duty ratio of a primary side switching tube.
5. An LLC resonant converter as claimed in claim 4, wherein:
the voltage switching point setting between the full-bridge LLC PFM control mode and the full-bridge LLC variable duty ratio control mode is satisfied: when the input voltage rises to be higher than the modal switching voltage, namely the switching frequency is equal to the corresponding voltage V _ fr when the resonant frequency fr, the LLC resonant converter enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode; the input voltage is reduced to be lower than the modal switching voltage, namely the corresponding voltage V _ fr when the switching frequency is equal to the resonant frequency fr, and the LLC resonant converter enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
6. An LLC resonant converter as claimed in claim 4, wherein:
the switching mode between the full-bridge LLC PFM control mode and the full-bridge LLC variable duty ratio control mode is as follows:
after the switching frequency is increased to be equal to the resonance frequency fr, the switching frequency is stabilized at the value, the duty ratio of the primary side switching tube is gradually reduced to be stable, and the control mode enters a full-bridge LLC variable duty ratio control mode from a full-bridge LLC PFM control mode;
after the duty ratio of the primary side switching tube is increased to be equal to 50%, the duty ratio of the primary side switching tube is stabilized at the value, the switching frequency is gradually reduced to be stable, and the control mode enters a full-bridge LLC PFM control mode from a full-bridge LLC variable duty ratio control mode.
7. An LLC resonant converter as claimed in claim 4, wherein: the primary LLC resonant circuit comprises a primary switch tube S1, a primary switch tube S2, a primary switch tube S3, a primary switch tube S4, a primary switch tube S5, a primary switch tube S6, a resonant capacitor Cr, a resonant inductor Lr and a magnetizing inductor Lm, wherein the drain of the primary switch tube S1 is connected to the drain of the primary switch tube S2 and the positive terminal of an input source Vin, the source of the primary switch tube S1 is connected to the drain of the primary switch tube S3 and one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected to one end of the resonant inductor Lr and the drain of the primary switch tube S5, the source of the primary switch tube S5 is connected to the source of the primary switch tube S6, the other end of the resonant Lr is connected to one end of the primary winding Np of a transformer T, the non-synonym end of the primary winding Np of the transformer T is connected to the other end of the magnetizing inductor Lm, the source of the primary switch tube S2, the drain of the primary switch tube S4 and the drain of the primary switch tube S6, the source of the primary side switch tube S4 is connected to the source of the primary side switch tube S3 and the negative pole of the input source Vin.
8. An LLC resonant converter as claimed in claim 4, wherein: the primary LLC resonant circuit comprises a primary switch tube S1, a primary switch tube S2, a primary switch tube S3, a primary switch tube S4, a primary switch tube S5, a primary switch tube S6, a resonant capacitor Cr, a resonant inductor Lr and a magnetizing inductor Lm, wherein the drain of the primary switch tube S1 is connected to the drain of the primary switch tube S2 and the positive terminal of an input source Vin, the source of the primary switch tube S1 is connected to the drain of the primary switch tube S3 and to one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected to one end of the resonant inductor Lr and to the source of the primary switch tube S6, the drain of the primary switch tube S6 is connected to the drain of the primary switch tube S5, the other end of the resonant Lr is connected to one end of the primary winding Np of a transformer T, the non-synonym end of the primary winding Np of the transformer T is connected to the other end of the magnetizing inductor Lm, the source of the primary switch tube S2, the drain of the primary switch tube S4 and the source of the primary switch tube S, the source of the primary side switch tube S4 is connected to the source of the primary side switch tube S3 and the negative pole of the input source Vin.
9. An LLC resonant converter as claimed in claim 7 or 8, wherein: the full-bridge LLC PFM control mode is as follows: the switching frequencies of the primary side switching tubes S1-S4 are equal but not fixed, the primary side switching tube S1 and the primary side switching tube S2 are conducted complementarily, the primary side switching tube S1 and the primary side switching tube S4 are conducted and turned off simultaneously, the primary side switching tube S2 and the primary side switching tube S3 are conducted and turned off simultaneously, the primary side switching tube S5 and the primary side switching tube S6 are always in a turned-off state, the control of output voltage is achieved by adjusting the switching frequencies of the primary side switching tubes S1-S4, and the larger the switching frequency is, the smaller the gain of the output voltage is.
10. An LLC resonant converter as claimed in claim 7 or 8, wherein: the full-bridge LLC variable duty ratio control mode is as follows: switching frequencies of the primary side switching tubes S1 to S6 are equal and fixed, the primary side switching tube S1 and the primary side switching tube S5 are in complementary conduction, the primary side switching tube S2 and the primary side switching tube S6 are in complementary conduction, the primary side switching tube S1 and the primary side switching tube S4 are in conduction and off simultaneously, the primary side switching tube S2 and the primary side switching tube S3 are in conduction and off simultaneously, the duty ratio of the primary side switching tube S1 is equal to that of the primary side switching tube S2, not more than 50% and 180% of phase difference between the primary side switching tube S2 and the primary side switching tube S5, the duty ratio of the primary side switching tube S5 is equal to that of the primary side switching tube S6, not less than 50% and 180% of phase difference between the primary side switching tube S2, control over voltage is achieved by adjusting the duty ratio of the primary side.
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| PCT/CN2021/104748 WO2022088744A1 (en) | 2020-10-28 | 2021-07-06 | Llc resonant converter, and wide gain control method |
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| CN114142737A (en) * | 2021-12-08 | 2022-03-04 | 中国科学院广州能源研究所 | Control method of full-bridge CLLC resonant converter |
| WO2022088744A1 (en) * | 2020-10-28 | 2022-05-05 | 广州金升阳科技有限公司 | Llc resonant converter, and wide gain control method |
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