CN112366947A - Control circuit of high-gain LLC resonant converter - Google Patents
Control circuit of high-gain LLC resonant converter Download PDFInfo
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- CN112366947A CN112366947A CN202011203420.1A CN202011203420A CN112366947A CN 112366947 A CN112366947 A CN 112366947A CN 202011203420 A CN202011203420 A CN 202011203420A CN 112366947 A CN112366947 A CN 112366947A
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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
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses a control circuit of a high-gain LLC resonant converter, which comprises an input Vin, a capacitor C1, a capacitor C2, a switch tube S1, a switch tube S2, an auxiliary switch S3, an inductor L1, a transformer T1, an output rectifying circuit DB1, an output capacitor Co, a negative feedback circuit and a secondary side rectifying ZCD detection circuit. Has the advantages that: the control circuit of the high-gain LLC resonant converter is simple in circuit and convenient to implement; the optimization of the full-load design efficiency near the resonance point can be well considered, and higher circuit gain can be ensured under other load conditions.
Description
Technical Field
The invention relates to an LLC resonant converter, in particular to a control circuit of a high-gain LLC resonant converter, which can control to obtain higher gain than a common LLC, can automatically adjust a circuit working mode according to a load, and gives consideration to full-load efficiency design optimization and circuit gain requirements.
Background
In recent years, dc converters have been widely used in various fields of life, and in particular, have attracted attention in dc micro-grids, power routers and dc distribution grids, and charging of electric vehicles, and have gained importance in power electronics research.
The LLC resonant converter not only can realize zero-voltage switching and zero-current switching due to its topological advantages, but also can easily integrate the resonant energy storage element into the transformer, so that it has very high power density and conversion efficiency, however, in recent years, with the increase of application occasions, there is a higher requirement for the load carrying capacity of the converter. As shown in fig. 8 and 9, the conventional LLC resonant converter is generally selected to operate near the resonant frequency under the rated operating condition, and the maximum gain of the circuit is limited. However, when the output voltage range is wide and the no-load voltage is high, for these applications, the conventional LLC design needs to increase resonant circulating current energy and reduce the transformer transformation ratio in order to ensure the voltage gain, so that when the LLC operates at the rated full load of the circuit, the resonant frequency point is deviated, and the full-load and heavy-load efficiency of the LLC circuit is obviously reduced by the excessive circulating current energy.
For such applications, it is necessary to research measures that can ensure full-load efficiency and also can give consideration to light-load and no-load circuit gains.
An effective solution to the problems in the related art has not been proposed yet.
Disclosure of Invention
In view of the problems in the related art, the present invention provides a control circuit for a high-gain LLC resonant converter, so as to overcome the above technical problems in the related art.
Therefore, the invention adopts the following specific technical scheme:
a control circuit of a high-gain LLC resonant converter comprises an input Vin, a capacitor C1, a capacitor C2, a switch tube S1, a switch tube S2, an auxiliary switch S3, an inductor L1, a transformer T1, an output rectifying circuit DB1, an output capacitor Co, a negative feedback circuit and a secondary side rectifying ZCD detection circuit; the input Vin is connected in parallel with a capacitor C1, the positive electrode of the capacitor C1 is connected to the first end of the switching tube S1, the negative electrode of the capacitor C1 is connected to the second end of the switching tube S2 and one end of a capacitor C2 and is grounded, the second end of the switching tube S1 is sequentially connected to the first end of the switching tube S2 and one end of the inductor L1, the other end of the inductor L1 is connected to the first input end of the transformer T1, the second input end of the transformer T1 is connected to the other end of the capacitor C2, the first output end of the transformer T1 is sequentially connected to the drain of the auxiliary switch S3 and the first end of the output rectification circuit DB1, the second end of the output rectification circuit DB1 is connected to the positive electrode of the output capacitor Co, the negative electrode of the output capacitor Co is sequentially connected to the source of the auxiliary switch S3 and the second output end of the transformer T1, the output capacitor Co is connected with the negative feedback circuit, and the output rectifying circuit DB1 is connected with the secondary side rectifying ZCD detection circuit.
Further, the capacitor C1 is a polar capacitor.
Further, the output capacitor Co is a polar capacitor.
Further, the negative feedback circuit comprises a first comparator, a resistor R1, a resistor R2, a capacitor C3, a Vo/Io signal terminal and a Vcomp signal terminal; the first input end of the first comparator is connected with a voltage reference, the second input end of the first comparator is sequentially connected with one end of the resistor R1 and one end of the resistor R2, the other end of the resistor R1 is connected with the Vo/Io signal end, the other end of the resistor R2 is connected with one end of the capacitor C3, and the other end of the capacitor C3 is sequentially connected with the output end of the first comparator and the Vcomp signal end.
Further, the secondary side rectification ZCD detection circuit comprises a second comparator, a third comparator, an RS trigger, a Vth _ l signal end, a Vth _ h signal end, an I _ D signal end and a ZCD signal end; the second input end of the second comparator is connected with the Vth _ h signal end, the output end of the second comparator is connected with the first end of the RS trigger, the first input end of the second comparator is sequentially connected with the I _ D signal end and the second input end of the third comparator, the first input end of the third comparator is connected with the Vth _ l signal end, the output end of the third comparator is connected with the second end of the RS trigger, and the third end of the RS trigger is connected with the ZCD signal end.
The invention has the beneficial effects that:
(1) according to the invention, the voltage can be boosted by controlling the conduction time or the duty ratio of the auxiliary switch S3, and the circuit gain higher than the traditional LLC is obtained. By monitoring the switching frequency, the switching control mode is automatically judged, and the circuit still works in the traditional LLC frequency conversion control mode in an LLC gain adjustment range. When higher gain is required, the auxiliary switch S3 PWM control mode automatically operates in the lowest frequency limit. When the auxiliary switch S3 is in the PWM control mode, the switching tube S1, the switching tube S2 and the output rectifying circuit DB1 can still operate in the soft-switching state.
(2) The control circuit of the high-gain LLC resonant converter is simple in circuit and convenient to implement. The optimization of the full-load design efficiency near the resonance point can be well considered, and higher circuit gain can be ensured under other load conditions.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a circuit diagram according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram of a negative feedback circuit according to a first embodiment of the invention;
FIG. 3 is a schematic diagram of a secondary side rectification ZCD detection circuit according to a first embodiment of the invention;
FIG. 4 is a flow diagram of a negative feedback circuit outputting a Vcomp signal, according to an embodiment of the invention;
FIG. 5 is one of the waveform diagrams of FIG. 1;
FIG. 6 is a second waveform diagram of FIG. 1;
FIG. 7 is a schematic diagram according to a second embodiment of the present invention;
FIG. 8 is a schematic diagram of a prior art LLC resonant converter;
fig. 9 is a frequency diagram of fig. 8.
Detailed Description
For further explanation of the various embodiments, the drawings which form a part of the disclosure and which are incorporated in and constitute a part of this specification, illustrate embodiments and, together with the description, serve to explain the principles of operation of the embodiments, and to enable others of ordinary skill in the art to understand the various embodiments and advantages of the invention, and, by reference to these figures, reference is made to the accompanying drawings, which are not to scale and wherein like reference numerals generally refer to like elements.
According to an embodiment of the invention, a control circuit of a high gain LLC resonant converter is provided.
Example one
Referring to the drawings and the detailed description, as shown in fig. 1-3, a control circuit of a high-gain LLC resonant converter according to an embodiment of the present invention includes an input Vin, a capacitor C1, a capacitor C2, a switch tube S1, a switch tube S2, an auxiliary switch S3, an inductor L1, a transformer T1, an output rectifier circuit DB1, an output capacitor Co, a negative feedback circuit, and a secondary side rectification ZCD detection circuit; the input Vin is connected in parallel with a capacitor C1, the positive electrode of the capacitor C1 is connected to the first end of the switching tube S1, the negative electrode of the capacitor C1 is connected to the second end of the switching tube S2 and one end of a capacitor C2 and is grounded, the second end of the switching tube S1 is sequentially connected to the first end of the switching tube S2 and one end of the inductor L1, the other end of the inductor L1 is connected to the first input end of the transformer T1, the second input end of the transformer T1 is connected to the other end of the capacitor C2, the first output end of the transformer T1 is sequentially connected to the drain of the auxiliary switch S3 and the first end of the output rectification circuit DB1, the second end of the output rectification circuit DB1 is connected to the positive electrode of the output capacitor Co, the negative electrode of the output capacitor Co is sequentially connected to the source of the auxiliary switch S3 and the second output end of the transformer T1, the output capacitor Co is connected with the negative feedback circuit, and the output rectifying circuit DB1 is connected with the secondary side rectifying ZCD detection circuit.
In one embodiment, the capacitor C1 is a polar capacitor.
In one embodiment, the output capacitor Co is a polar capacitor.
In one embodiment, the negative feedback circuit comprises a first comparator, a resistor R1, a resistor R2, a capacitor C3, a Vo/Io signal terminal and a Vcomp signal terminal; the first input end of the first comparator is connected with a voltage reference, the second input end of the first comparator is sequentially connected with one end of the resistor R1 and one end of the resistor R2, the other end of the resistor R1 is connected with the Vo/Io signal end, the other end of the resistor R2 is connected with one end of the capacitor C3, and the other end of the capacitor C3 is sequentially connected with the output end of the first comparator and the Vcomp signal end.
In one embodiment, the secondary side rectification ZCD detection circuit comprises a second comparator, a third comparator, an RS trigger, a Vth _ l signal end, a Vth _ h signal end, an I _ D signal end and a ZCD signal end; the second input end of the second comparator is connected with the Vth _ h signal end, the output end of the second comparator is connected with the first end of the RS trigger, the first input end of the second comparator is sequentially connected with the I _ D signal end and the second input end of the third comparator, the first input end of the third comparator is connected with the Vth _ l signal end, the output end of the third comparator is connected with the second end of the RS trigger, and the third end of the RS trigger is connected with the ZCD signal end.
In one embodiment, as shown in fig. 1 and 5, when the switching tube S1 and the auxiliary switch S3 are turned on, the inductor L1 is excited, and the excitation voltage across the inductor L1 is Vin-Vcr-Vin/2; when the auxiliary switch S3 is turned off, the inductor L1 is demagnetized, and the excitation voltage across the inductor L1 is N × Vo- (Vin-Vcr) ═ N × Vo-Vin/2. When the output rectifying circuit DB1 is turned off, the voltage across the inductor L1 is (Vin/2) × L1/(L1+ Lm). Where Lm is the transformer magnetizing inductance, typically significantly larger than inductance L1. The inductance L1 continues to be excited, but the excitation voltage drops significantly and the current rise rate drops significantly.
If the on duty of the auxiliary switch S3 is D1, the on duty of the output rectifier circuit DB1 is D2, and it is assumed that D1+ D2 is 1, there is approximately a relationship:
(Vin/2)*D1＝(N*Vo-Vin/2)*D2
N*Vo＝(Vin/2)*(D1+D2)/D2＝(Vin/2)/(1-D1)
it can be seen that increasing D1, a higher Vo can be obtained, achieving a higher gain than conventional LLC circuits.
Each time the switch tube S1 and the switch tube S2 are switched on, the auxiliary switch S3 is switched on, the switching-off of the auxiliary switch S3 is determined by the control circuit according to load feedback, and the switch tube S1 and the switch tube S2 on the primary side of the converter transformer still have ZVS switching-on similar to LLC; if the control is regulated, it is ensured that the secondary side rectifier circuit DB1 has ZCS off. Most devices still have soft switching characteristics, and the circuit conversion efficiency is high. At the moment, the circuit can work in a fixed frequency mode, and the circuit obtains the set output voltage Vo or output current Io mainly by adjusting the conduction time or conduction duty ratio of the auxiliary switch S3; by adjusting and controlling the conduction time or the conduction duty ratio of the auxiliary switch S3, higher circuit gain and higher Vo/Io can be obtained. The output voltage will rise by increasing the on-time or on-duty of the auxiliary switch S3; conversely, by decreasing the on-time or on-duty of the auxiliary switch S3, the output voltage will decrease.
When the auxiliary switch S3 is always on, the transformer T1 is always short-circuited, and the primary energy cannot be transferred to the output side, so this mode is not allowed in the control design. May be constrained by means of a maximum duty cycle limit, etc.;
when the auxiliary switch S3 is left off, the circuit degrades into a conventional LLC converter. The control mode of the frequency feedback control of the output voltage or the output current is similar to that of a general series resonance or series-parallel resonance circuit, the switch tube S1 and the switch tube S2 are symmetrically and complementarily driven, and the set output voltage Vo or the set output current Io is obtained through the frequency control.
In one embodiment, the control mode, such as on/off, can be switched according to the output load feedback, when Vo is in the LLC gain adjustment range, the circuit works in the LLC mode, and the switching frequency is adjusted to adjust the output; when Vo needs to be increased further and exceeds the LLC gain interval, the circuit is switched to a PWM control mode for adjusting the conduction time or duty ratio of the auxiliary switch S3 to obtain higher set Vo and Io.
In one embodiment, when the circuit operates in the auxiliary switch S3 PWM control mode, the auxiliary switch S3 is turned on each time the switch tube S1 and the switch tube S2 are turned on, and the turn-off of the auxiliary switch S3 is determined by the control circuit according to the load feedback. The switch tube S1 and the switch tube S2 are driven in a complementary symmetry mode, and still have ZVS opening characteristics similar to LLC.
In one embodiment, when the circuit is operating in the auxiliary switch S3 PWM control mode, the secondary rectifier circuit DB1 may be guaranteed to have ZCS off if the control is adjusted.
In one embodiment, when the circuit is operating in the auxiliary switch S3 PWM control mode, the auxiliary switch S3 is prevented from being turned on all the time by limiting the maximum duty cycle, etc., which results in a substantial inability to transfer energy to the output side.
In one embodiment, a negative feedback circuit for the output voltage Vo or current Io is shown in fig. 2, with PI compensation, and the output is Vcomp.
In one embodiment, as shown in fig. 3, the secondary side rectification ZCD detection circuit enables the RS flip-flop and the ZCD output is high when the current is less than the low detection threshold Vth _ l; when the current is greater than the high detection threshold Vth _ h, the RS trigger is reset, and the ZCD output is set low. When ZCD is high, turn on S3, can avoid output rectifier circuit DB1 to turn off hard, cause reverse recovery loss and stress spike.
In one embodiment, as shown in fig. 4, the control detection feedback circuit outputs a Vcomp signal to calculate the operating frequency. The higher the Vcomp, the lower the operating frequency of the calculation. Judging whether the calculated working frequency is lower than the set lowest working frequency, if not, indicating that the circuit is still in the LLC gain adjustment range at the moment, symmetrically and complementarily driving a switch tube S1 and a switch tube S2 by the circuit, and carrying out closed-loop adjustment to obtain the set Vo/Io;
if the value is lower than the set value, which indicates that the circuit is about to cross the LLC gain adjustment range, the switch tube S1 and the switch tube S2 are driven at the lowest working frequency, and the conduction duty ratio of the auxiliary switch S3 is calculated according to the Vcomp signal, wherein the higher the Vcomp signal is, the larger the conduction duty ratio of the auxiliary switch S3 is. The conduction of the auxiliary switch S3 is synchronous with the conduction edges of the switch tube S1 and the switch tube S2;
the maximum duty cycle of the auxiliary switch S3 is limited and can be set manually, for example, 90%.
In one embodiment, in order to avoid hard switching of the auxiliary switch S3 and the output rectifying circuit DB1, which may cause reverse recovery loss and device stress spike, when the auxiliary switch S3, the switch tube S1 or the switch tube S2 are ready to be turned on, if the ZCD signal is high, the switch tube S1, the switch tube S2 and the auxiliary switch S3 are driven at a set frequency and duty ratio; if the ZCD signal is low, wait is maintained until the ZCD signal goes high, turning on auxiliary switch S3, switch S1 or switch S2.
In one embodiment, as shown in fig. 5, for the key waveforms of the circuit when the circuit enters the auxiliary switch S3 PWM control mode, it can be seen that the ZCD signal is already high when the auxiliary switch S3 is turned on.
In one embodiment, fig. 6 shows the key waveforms of the circuit when the circuit enters the auxiliary switch S3 PWM control mode. Due to factors such as sudden load change, the auxiliary switch S3, the switch tube S1 or the switch tube S2 are turned on until the ZCD signal becomes high.
Example two
As shown in fig. 7, the control circuit of the high-gain LLC resonant converter according to the embodiment of the present invention includes an input Vin, a capacitor C1, a capacitor C2, a switch tube S1, a switch tube S2, an auxiliary switch S3, an inductor L1, a transformer T1, an output rectifier circuit DB1, an output capacitor Co, and a resonant driving control circuit; the input Vin is connected in parallel with a capacitor C1, the positive electrode of the capacitor C1 is connected with the first end of the switch tube S1, the negative electrode of the capacitor C1 is connected with the second end of the switch tube S2 and one end of the capacitor C2 and is grounded, the second end of the switch tube S1 is sequentially connected with the first end of the switch tube S2 and one end of the inductor L1, the other end of the inductor L1 is connected with the first input end of the transformer T1, the second input end of the transformer T1 is connected with the other end of the capacitor C2, the first output end of the transformer T1 is connected with the second end of the output rectification circuit DB1, the first end of the output rectification circuit DB1 is connected with the positive electrode of the output capacitor Co, the negative electrode of the output capacitor Co is sequentially connected with the source of the auxiliary switch S3 and the fifth end of the output rectification circuit DB1, the drain of the auxiliary switch S3 is connected with the third end of the output rectification circuit DB1, the fourth end of the output rectifying circuit DB1 is connected to the second output end of the transformer T1, the gate of the auxiliary switch S3 is connected to the third end of the resonant driving control circuit, the second end of the resonant driving control circuit is connected to the third end of the switching tube S2, and the first end of the resonant driving control circuit is connected to the third end of the switching tube S1.
For the convenience of understanding the technical solutions of the present invention, the following detailed description will be made on the working principle or the operation mode of the present invention in the practical process.
In practical application, when the switching tube S1 is turned on, the switching tube S2 is turned off, and the auxiliary switch S3 is turned on, a current passes through the switching tube S1, the inductor L1, the transformer T1, the auxiliary switch S3, the resonant capacitor C2, and the input capacitor C1;
when the switching tube S1 is turned off, the switching tube S2 is turned on, and the auxiliary switch S3 is turned on, current passes through the switching tube S2, the inductor L1, the transformer T1, the auxiliary switch S3, and the resonant capacitor C2;
when the switch tube S1 is turned on, the switch tube S2 is turned off, the auxiliary switch S3 is turned off, and the output rectifying circuit DB1 is turned on, current passes through the switch tube S1, the inductor L1, the transformer T1, the output rectifying circuit DB1, the output capacitor Co, the resonant capacitor C2, and the input capacitor C1;
when the switching tube S1 is turned off, the switching tube S2 is turned on, the auxiliary switch S3 is turned off, and the output rectifying circuit DB1 is turned on, current passes through the switching tube S2, the inductor L1, the transformer T1, the output rectifying circuit DB1, the output capacitor Co, and the resonant capacitor C2;
when the switching tube S1 is turned on, the switching tube S2 is turned off, the auxiliary switch S3 is turned off, and the output rectifying circuit DB1 is turned off, current passes through the switching tube S1, the inductor L1, the transformer T1, the resonant capacitor C2, and the input capacitor C1;
when the switching tube S1 is turned off, the switching tube S2 is turned on, the auxiliary switch S3 is turned off, and the output rectifying circuit DB1 is turned off, current passes through the switching tube S2, the inductor L1, the transformer T1, and the resonant capacitor C2;
for the convenience of analysis, the voltage of the resonant capacitor can be approximated to Vin/2, assuming that the value of the resonant capacitor is large enough and the voltage ripple in the switching period is small enough.
In summary, according to the above technical solution of the present invention, the voltage boost can be realized by controlling the on-time or duty ratio of the auxiliary switch S3, so as to obtain a higher Vo and a higher circuit gain than the conventional LLC. By monitoring the switching frequency, the switching control mode is automatically judged, and the circuit still works in the traditional LLC frequency conversion control mode in an LLC gain adjustment range. When higher gain is required, the auxiliary switch S3 PWM control mode automatically operates in the lowest frequency limit. When the auxiliary switch S3 is in the PWM control mode, the switching tube S1, the switching tube S2 and the output rectifying circuit DB1 can still operate in the soft-switching state. The control circuit of the high-gain LLC resonant converter is simple in circuit and convenient to implement. The optimization of the full-load design efficiency near the resonance point can be well considered, and higher circuit gain can be ensured under other load conditions.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (5)
1. A control circuit of a high-gain LLC resonant converter is characterized by comprising an input Vin, a capacitor C1, a capacitor C2, a switch tube S1, a switch tube S2, an auxiliary switch S3, an inductor L1, a transformer T1, an output rectifying circuit DB1, an output capacitor Co, a negative feedback circuit and a secondary side rectifying ZCD detection circuit;
wherein the input Vin is connected in parallel with a capacitor C1, the positive electrode of the capacitor C1 is connected to the first end of the switching tube S1, the negative electrode of the capacitor C1 is connected to the second end of the switching tube S2 and one end of the capacitor C2 and is grounded, the second end of the switching tube S1 is sequentially connected to the first end of the switching tube S2 and one end of the inductor L1, the other end of the inductor L1 is connected to the first input end of the transformer T1, the second input end of the transformer T1 is connected to the other end of the capacitor C2, the first output end of the transformer T1 is sequentially connected to the drain of the auxiliary switch S3 and the first end of the output rectifying circuit DB1, the second end of the output rectifying circuit DB1 is connected to the positive electrode of the output capacitor Co, and the negative electrode of the output capacitor Co is sequentially connected to the source of the auxiliary switch S3 and the second output end of the transformer T1, the output capacitor Co is connected with the negative feedback circuit, and the output rectifying circuit DB1 is connected with the secondary side rectifying ZCD detection circuit.
2. The control circuit of claim 1, wherein said capacitor C1 is a polar capacitor.
3. The control circuit of claim 1, wherein the output capacitor Co is a polar capacitor.
4. The control circuit of claim 1, wherein the negative feedback circuit comprises a first comparator, a resistor R1, a resistor R2, a capacitor C3, a Vo/Io signal terminal, and a Vcomp signal terminal;
the first input end of the first comparator is connected with a voltage reference, the second input end of the first comparator is sequentially connected with one end of the resistor R1 and one end of the resistor R2, the other end of the resistor R1 is connected with the Vo/Io signal end, the other end of the resistor R2 is connected with one end of the capacitor C3, and the other end of the capacitor C3 is sequentially connected with the output end of the first comparator and the Vcomp signal end.
5. The control circuit of a high-gain LLC resonant converter according to claim 1, wherein said secondary side rectification ZCD detection circuit comprises a second comparator, a third comparator, an RS flip-flop, a Vth _ l signal terminal, a Vth signal terminal, an I _ D signal terminal and a ZCD signal terminal;
the second input end of the second comparator is connected with the Vth _ h signal end, the output end of the second comparator is connected with the first end of the RS trigger, the first input end of the second comparator is sequentially connected with the I _ D signal end and the second input end of the third comparator, the first input end of the third comparator is connected with the Vth _ l signal end, the output end of the third comparator is connected with the second end of the RS trigger, and the third end of the RS trigger is connected with the ZCD signal end.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113381614A (en) * | 2021-06-21 | 2021-09-10 | 深圳中瀚蓝盾电源有限公司 | Control circuit, control system of LLC resonant circuit and switching power supply |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104237615A (en) * | 2013-06-09 | 2014-12-24 | 中兴通讯股份有限公司 | Current zero-crossing detection device, signal acquisition circuit and circuit system |
| CN105896986A (en) * | 2014-12-11 | 2016-08-24 | 南京航空航天大学 | Resonant converter and control method thereof |
| CN110365203A (en) * | 2019-06-19 | 2019-10-22 | 广州金升阳科技有限公司 | Current sampling circuit, current over-zero detection circuit, totem non-bridge PFC circuits and its control method |
| CN111107703A (en) * | 2019-12-06 | 2020-05-05 | 中国科学院电工研究所 | Current detection type synchronous rectification control method based on Rogowski coil |
-
2020
- 2020-11-02 CN CN202011203420.1A patent/CN112366947A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104237615A (en) * | 2013-06-09 | 2014-12-24 | 中兴通讯股份有限公司 | Current zero-crossing detection device, signal acquisition circuit and circuit system |
| CN105896986A (en) * | 2014-12-11 | 2016-08-24 | 南京航空航天大学 | Resonant converter and control method thereof |
| CN110365203A (en) * | 2019-06-19 | 2019-10-22 | 广州金升阳科技有限公司 | Current sampling circuit, current over-zero detection circuit, totem non-bridge PFC circuits and its control method |
| CN111107703A (en) * | 2019-12-06 | 2020-05-05 | 中国科学院电工研究所 | Current detection type synchronous rectification control method based on Rogowski coil |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113381614A (en) * | 2021-06-21 | 2021-09-10 | 深圳中瀚蓝盾电源有限公司 | Control circuit, control system of LLC resonant circuit and switching power supply |
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