CN113938020A - Half-bridge LLC resonant converter - Google Patents
Half-bridge LLC resonant converter Download PDFInfo
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- CN113938020A CN113938020A CN202111112833.3A CN202111112833A CN113938020A CN 113938020 A CN113938020 A CN 113938020A CN 202111112833 A CN202111112833 A CN 202111112833A CN 113938020 A CN113938020 A CN 113938020A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping 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 relates to the field of switching converters, and discloses a half-bridge LLC resonant converter which is composed of a primary LLC resonant circuit, a transformer and a secondary rectification circuit. Two resistors with the same resistance value are added in the primary LLC resonant circuit to ensure that voltages at two ends of the resonant capacitor are in a voltage-sharing state in a light and no-load intermittent working mode, so that the resonant currents in the first few pulse periods in the intermittent working mode are kept symmetrical, and the switching tube can be ensured to realize zero-voltage switching-on. Meanwhile, the resistor can also pre-charge the resonant capacitor when the switch is started, so that the voltage change rate between drain and source electrodes of the switch tube at the moment of starting the switch can be effectively reduced, and the crosstalk generated by the switch tube driving to cause the switch tube to be connected in common and further damage the system is avoided. The half-bridge LLC resonant converter circuit is simple in structure, does not need additional logic control, improves the working reliability of the half-bridge LLC converter on different voltage occasions, and widens the application prospect of the converter in a wide voltage gain range.
Description
Technical Field
The invention relates to the field of switching converters, in particular to a wide-gain LLC resonant converter.
Background
With the rapid development of the industrial level in recent years, people have increasingly increased demands for medium-high power converters, and the traditional flyback architecture cannot simultaneously meet the requirements of high power density, high reliability, high efficiency and high gain. The LLC converter, as a resonant converter, has the advantages of low noise, low EMI, low stress, low switching loss, and the like. When the traditional LLC resonant converter is applied to the occasion of a wider input voltage range, in order to realize high-gain output, the adjustment range of the switching frequency is wider by adopting a PWM (pulse-width modulation) strategy, and when the switching frequency is low, the converter works in a capacitive region, zero-voltage conduction (ZVS) is difficult to realize, and the efficiency of the converter is also obviously reduced.
Based on the fact that many scholars at home and abroad propose to adopt various control modes and various novel LLC topologies to improve the gain of the LLC converter under wide-range input. For example, chinese patent application publication No. CN 112332674 a discloses a dual-mode control scheme, which adopts a full-bridge LLC frequency conversion control mode when the input voltage is in a low-voltage section, a full-bridge LLC fixed-frequency control mode when the input voltage is in a medium-voltage section, and a half-bridge LLC frequency conversion control mode when the input voltage is in a high-voltage section; the gain range of full-bridge frequency conversion PFM control is 2-1, the gain range of full-bridge fixed frequency PWM control is 1-0.5, the gain range of half-bridge fixed frequency PWM control is 0.5-0.25, the full-bridge topology PFM control mode is switched to full-bridge topology PWM, and the circuit gain range of half-bridge topology PWM is switched to 2-0.25.
In a high-voltage input occasion, the input current of the primary side of the LLC resonant converter is small, a half-bridge LLC circuit is generally selected to be used, and compared with a full-bridge LLC circuit, the LLC resonant converter is simple in structure, the design difficulty of the primary side driving circuit is greatly reduced, and meanwhile the cost and the volume of the system are effectively saved. In a resonant cavity of a traditional half-bridge LLC resonant converter, only a single resonant capacitor Cr is arranged, as shown in figure 1, a split resonant capacitor structure is derived on the basis, as shown in figure 2, for the LLC resonant converter with the single resonant capacitor, the LLC resonant converter adopting the split resonant capacitors Cr1 and Cr2 has smaller input current ripple and root mean square value, and the capacitance value of each split resonant capacitor is only half of that of the single resonant capacitor.
In order to further improve the efficiency of the half-bridge LLC resonant converter, a clamping branch is added, as shown in fig. 3, when the switching tubes S3 and S4 of the clamping branch are simultaneously turned on, current circulates between the resonant inductor Lr, the excitation inductor Lm and the clamping branch, so that the resonant current is prevented from flowing through the resonant capacitors Cr1 and Cr2 when the switching tubes S1 and S2 on the primary side are turned off, which is beneficial to reducing the energy loss on the parasitic resistors of the resonant capacitors Cr1 and Cr2, thereby effectively improving the efficiency of the converter.
With the increasing importance of energy efficiency and environmental protection, people expect higher standby efficiency of the switching power supply, in order to reduce the loss of the switching power supply in light and no load and improve the efficiency, some researchers propose that the converter works in an intermittent mode, namely a Burst mode, and in the mode, the converter can continuously work for a plurality of cycles and then be turned off for a plurality of cycles according to the condition of load feedback, and the method can effectively reduce the switching loss and reduce the static power consumption. For portable power converter device applications, efficiency under light load is a very important indicator, and therefore Burst control mode is essential. When the input voltage of the half-bridge LLC resonant converter is suddenly changed or is in a high-voltage light no-load or Burst mode, the transient voltage change rate (dv/dt) of the short-time drain source of the switching tube is overlarge, and meanwhile, the working reliability of the converter is seriously influenced because the voltage and current stress at two ends of the switching tube is aggravated by the asymmetry of the parasitic resistance of the resonant capacitor and the equivalent resistance of a PCB circuit. In order to reduce the drain-source stress of the switching tube in light no-load and large dynamic processes to enable the leakage-source stress to meet the protection requirement of output voltage, the traditional control method is to compare the voltage at two ends of an input/output and a resonant capacitor with a reference threshold value after sampling, and then enable a controller to control the driving pulse of the switching tube to achieve the purpose of soft switching, or adopt a buffer circuit to absorb the stress of the switching tube, but the control methods need additional hardware circuits to realize the control methods, the cost is higher, the control strategy is more complex, the response time of protection action is longer relative to the switching period when the system is abnormal, and the transient voltage change rate (dv/dt) of the short-term drain-source of the switching tube is too large to enable the switching tube to be damaged.
In view of this, the invention provides a half-bridge LLC resonant converter circuit to solve the problems of high-voltage startup and Burst mode switch tube damage of a wide-gain LLC resonant converter in the prior art.
SUMMARY OF THE PATENT FOR INVENTION
In view of this, the technical problems to be solved by the present invention are: the half-bridge LLC resonant converter circuit not only can provide a pre-charging path for the resonant capacitor of the wide-gain LLC resonant converter during startup to reduce the stress of a switch tube, but also can enable the voltages at two ends of the resonant capacitor to be basically consistent, has a simple and reliable circuit structure, does not need to increase the complexity of a control system, does not delay protection action, and has lower cost.
In order to achieve the above purpose, the technical solutions proposed by the patent embodiments of the present invention are as follows:
a half-bridge LLC resonant converter comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, wherein the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a first resonant capacitor, a second resonant capacitor, a resonant inductor and an excitation inductor;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resistor and the second resistor are connected in series and then connected in parallel to the positive electrode of the input end and the negative electrode of the input end, the first resonant capacitor is connected in parallel with the first resistor, and the second resonant capacitor is connected in parallel with the second resistor;
one end of the resonant inductor is connected to the source electrode of the first switching tube, the other end of the resonant inductor is connected to one end of the excitation inductor and one end of the primary winding of the transformer, and the other end of the excitation inductor is connected to the connection point of the first resistor and the second resistor and the other end of the primary winding of the transformer.
The invention also provides a half-bridge LLC resonant converter, which comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, wherein the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a resonant capacitor, a resonant inductor and an excitation inductor;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resistor and the second resistor are connected in series and then connected in parallel to the positive electrode of the input end and the negative electrode of the input end, one end of the resonance capacitor is connected to the source electrode of the second switching tube, the other end of the resonance capacitor is connected to one end of the excitation inductor, and the other end of the resonance capacitor is connected to the middle connection point of the first resistor and the second resistor;
one end of the resonant inductor is connected to the source electrode of the first switching tube, and the other end of the resonant inductor is connected to the other end of the excitation inductor.
The invention also provides a half-bridge LLC resonant converter, which comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, wherein the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a resonant capacitor, a resonant inductor and an excitation inductor;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resistor and the second resistor are connected in series and then connected to the anode of the input end and the cathode of the input end in parallel, and the middle connecting point of the first resistor and the second resistor is connected with the source electrode of the first switching tube; one end of the resonant capacitor is connected to the source electrode of the first switching tube, and the other end of the resonant capacitor is connected to one end of the resonant inductor;
the other end of the resonant inductor is connected to one end of the excitation inductor, and the other end of the excitation inductor is connected to the source electrode of the second switching tube.
The invention also provides a half-bridge LLC resonant converter, which comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, and is characterized in that the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a resistor, a resonant inductor, an excitation inductor, a first resonant capacitor, a second resonant capacitor and a clamping switch;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resonant capacitor and the second resonant capacitor are connected in series and then connected in parallel to the positive electrode of the input end and the negative electrode of the input end, and the resistor is connected in parallel with the first resonant capacitor;
one end of the resonant inductor is connected to the source electrode of the first switching tube, the other end of the resonant inductor is connected to one end of the excitation inductor, and the other end of the excitation inductor is connected to a connection point of the first resonant capacitor and the second resonant capacitor.
The invention further provides a half-bridge LLC resonant converter, which comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, wherein the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a resonant inductor, an excitation inductor, a resonant capacitor and a clamping switch;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resistor and the second resistor are connected in series and then connected to two ends of an input source in parallel, and a middle connection point of the first resistor and the second resistor is connected to one end of the resonant capacitor; one end of the resonant inductor is connected to the source electrode of the first switching tube, and the other end of the resonant inductor is connected to one end of the excitation inductor.
Preferably, the resonant capacitor is composed of a single resonant capacitor, and a middle connection point of the first resistor and the second resistor connected in series is connected with one end of the resonant capacitor.
Preferably, the resonant capacitor includes a first resonant capacitor and a second resonant capacitor, the first resonant capacitor is connected in parallel with the first resistor, and the second resonant capacitor is connected in parallel with the second resistor.
Preferably, the half-bridge LLC resonant converter is further provided with a clamping circuit, the clamping circuit is formed by a third switching tube and a fourth switching tube connected in series in reverse, and a middle connection point of the series connection of the first resistor and the second resistor is connected to a drain of the fourth switching tube and one end of the primary winding of the transformer, respectively.
Preferably, the secondary side rectification circuit is a full-wave rectification structure or a full-bridge rectification structure; the secondary side rectifying circuit comprises a switching tube which is an MOS tube or a diode.
Preferably, the first resistor and the second resistor have the same resistance.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention discloses a wide-gain half-bridge LLC resonant converter, when the half-bridge LLC converter is in a high-voltage startup or short-circuit restart state, the transient voltage change rate dv/dt of drain-source electrodes of a first switching tube and a second switching tube is suddenly increased, so that crosstalk occurs in driving signals of the first switching tube and the second switching tube, the first switching tube and the second switching tube are in common, the system is damaged, after a first resistor is added, the first resonant capacitor and the second resonant capacitor can be pre-charged during high-voltage startup and short-circuit restart, the drain-source electrode stress of the first switching tube and the second switching tube at the startup moment can be effectively reduced, and therefore, the system is well protected, and no time delay exists;
(2) on the basis of increasing a first resistor connected with a first resonant capacitor in parallel, and after a second resistor with the same specification is merged into two ends of a second resonant capacitor, the voltage symmetry of two ends of the first resonant capacitor and the second resonant capacitor can be ensured when the converter is started in a high-voltage light and no-load mode or in a Burst mode, so that the initial current of a resonant cavity is symmetrical, the first switching tube and the second switching tube are prevented from entering a hard switching mode, the efficiency of the converter is improved, harmonic components near the switching frequency of an input side are greatly inhibited, the EMI (electro-magnetic interference) characteristic of the half-bridge LLC converter is good, and the influence of the increased resistor on the cost and the efficiency of a system can be ignored;
(3) the two first resistors and the two second resistors with the same resistance values are added in the primary LLC resonant circuit to ensure that voltages at two ends of the resonant capacitor are in a voltage-sharing state in a light and no-load intermittent working mode, so that the resonant currents in the first few pulse periods in the intermittent working mode are kept symmetrical, the primary switching tube is ensured to realize zero-voltage switching-on, and the working reliability of the system is effectively improved.
Drawings
Fig. 1 is a circuit structure diagram of a half-bridge LLC resonant converter in the prior art;
FIG. 2 is a diagram of a circuit structure of a conventional half-bridge LLC resonant converter using split resonant capacitors;
FIG. 3 is a circuit diagram of a half-bridge LLC resonant converter with a clamping branch circuit;
fig. 4 is a circuit configuration diagram of an LLC resonant converter in accordance with a first embodiment of the present invention;
fig. 5 is a circuit configuration diagram of an LLC resonant converter in a second embodiment of the invention;
FIG. 6 is a timing diagram of the control of the LLC resonant converter in the PWM mode according to the second embodiment of the invention;
FIG. 7 is a diagram showing the main waveforms of an LLC resonant converter according to the second embodiment of the invention when the voltages across the resonant capacitors are asymmetric;
FIG. 8 is a diagram showing the main waveforms of an LLC resonant converter according to the second embodiment of the invention when the voltages at the two ends of the resonant capacitor are symmetrical;
fig. 9 is a circuit configuration diagram of an LLC resonant converter in a third embodiment of the invention;
fig. 10 is a circuit configuration diagram of an LLC resonant converter in a fourth embodiment of the invention.
Detailed Description
First embodiment
The present embodiment will be described in detail with reference to fig. 4. The embodiment provides a wide-gain LLC resonant converter, which comprises an input source Vin, a primary LLC resonant circuit 10, a transformer T, a secondary rectification circuit 20 and an output load Ro, wherein the input source Vin, the primary LLC resonant circuit 10, the transformer T, the secondary rectification circuit 20 and the output load Ro are sequentially connected from input to output, the primary LLC resonant circuit 10 comprises an anode connected to the input source Vin, a cathode connected to the input source Vin, a half-bridge switching circuit, a clamping circuit, a resistor R1, a first resonant capacitor Cr1, a second resonant capacitor Cr2, a resonant inductor Lr and an excitation inductor Lm, the secondary rectification circuit comprises a switching tube SR1, a switching tube SR2 and an output filter capacitor Co, and the switching tube SR1 and the switching tube SR2 are MOS tubes or diodes.
The half-bridge switching circuit is provided with a first switching tube S1 and a first switching tube S2, the drain electrode of the first switching tube S1 is connected to the positive electrode of the input end of the primary LLC resonant circuit 10, the source electrode of the first switching tube S1 is connected to the drain electrode of the first switching tube S2, and the source electrode of the first switching tube S2 is connected to the negative electrode of the input end; the first resonant capacitor Cr1 and the second resonant capacitor Cr2 are connected in series and then connected in parallel to the positive electrode of the input end and the negative electrode of the input end of the primary LLC resonant circuit 10, and the resistor R1 is connected in parallel with the first resonant capacitor Cr 1; one end of the resonant inductor Lr is connected to the source of the first switching tube S1, and the other end of the resonant inductor Lr is connected to the end of the primary winding Np of the transformer T.
The clamping circuit is formed by reversely connecting a third switching tube S3 and a fourth switching tube S4 in series, the drain electrode of the third switching tube S3 is connected with the middle connection point of the first switching tube S1 and the second switching tube S2, the source electrode of the third switching tube S3 is connected with the source electrode of the fourth switching tube S4, and the drain electrode of the fourth switching tube S4 is connected with the middle connection point of the first resonant capacitor Cr1 and the second resonant capacitor Cr 2.
In this embodiment, the LLC resonant converter adopts a bimodal control in the full voltage range, that is, in the low voltage input section, the LLC resonant converter adopts a PFM control mode, and in the high voltage input section, a PWM control mode.
The input power Vin adopts the bus voltage of an AC/DC output end, and because the invention only aims at the high-voltage input section, the subsequent control description part only unfolds the high-voltage input section. In the whole high-voltage input section range, the LLC resonant converter works in a PWM control mode, the switching frequency is equal to the resonant frequency fr, and the output voltage gain is adjusted by changing the duty ratio D of the first switching tube S1 and the second switching tube S2; there is a maximum duty cycle Dmax at the minimum input voltage of the high voltage input section and a minimum duty cycle Dmin at the maximum input voltage of the high voltage input section.
In the prior art, a first switching tube S1 and a second switching tube S2 of an LLC resonant converter are directly connected in parallel with an input source Vin, and when a high-voltage starting machine is instantaneously started, the drain-source electrodes of the first switching tube S1 and the second switching tube S2 have larger dv/dt, so that the first switching tube S1 and the second switching tube S2 are driven to have crosstalk, and the common crosstalk is caused, and further the switching tubes are damaged. After the resistor R1 connected with the first resonant capacitor Cr1 in parallel is added, at the startup moment, a loop consisting of the input source Vin, the first resistor R1, the first resonant capacitor Cr1 and the second resonant capacitor Cr2 can charge the first resonant capacitor Cr1 and the second resonant capacitor Cr2, so that the influence of overlarge drain-source electrode dv/dt of the first switch tube S1 and the second switch tube S2 on a primary side switch tube during high-voltage startup is avoided, the drain-source electrode stress of the first switch tube S1 and the second switch tube S2 at the startup moment can be effectively reduced, and a better protection effect on a system is further achieved. The product of the resistance of the resistor R1 and the capacitance of the first and second resonant capacitors Cr1 and Cr2 is called a time constant tau, which is used for describing the charging and discharging speeds of the first and second resonant capacitors Cr1 and Cr2, and when the capacitance of the first and second resonant capacitors Cr1 and Cr2 is determined, the smaller the resistance of the resistor R1 is, the smaller the time constant is, the faster the charging and discharging speeds of the first and second resonant capacitors Cr1 and Cr2 are, and vice versa.
Second embodiment
The present embodiment will be described in detail with reference to fig. 5. The wide gain LLC resonant converter in this embodiment includes: the primary LLC resonant circuit 10 comprises an input end anode, an input end cathode, a half-bridge circuit consisting of a first switch tube S1 and a second switch tube S2, a clamping circuit consisting of a third switch tube S3 and a fourth switch tube S4 which are reversely connected in series, a first resistor R1, a second resistor R2, a first resonant capacitor Cr1, a second resonant capacitor Cr2, a resonant inductor Lr and an excitation inductor Lm; the secondary side rectification circuit consists of a switch tube SR1, a switch tube SR2 and a secondary side output filter capacitor Co, and the switch tube SR1 and the switch tube SR2 are MOS tubes or diodes.
In this embodiment, the LLC resonant converter adopts a bimodal control in the full voltage range, that is, in the low voltage input section, the LLC resonant converter adopts a PFM control mode, and in the high voltage input section, a PWM control mode.
The input source Vin adopts the bus voltage of an AC/DC output end, and because the invention only aims at the high-voltage input section, the subsequent control description part only unfolds the high-voltage input section. In the whole high-voltage input section range, the LLC resonant converter works in a PWM control mode, the switching frequency is equal to the resonant frequency fr, and the output voltage gain is adjusted by changing the duty ratio D of a switching tube; there is a maximum duty cycle Dmax at the minimum input voltage of the high voltage input section and a minimum duty cycle Dmin at the maximum input voltage of the high voltage input section.
When the LLC resonant converter operates in the PWM control mode, the control timing is shown in fig. 6. Wherein, VGS1Is a first switch tube S1 driving signal, VGS2For the second switching tube S2 driving signal, VGS3For the third switching tube S3 driving signal, VGS4For the fourth switching tube S4 driving signal, iSR1For switching tube SR1 current, iSR2For switching tube SR2 current, VGSR1For the driving signal of the switching tube SR1, VGSR2For driving the signal of the switching tube SR2, ILmFor exciting inductor current, ILrFor resonant cavity current, the switching frequencies of the first to fourth switching tubes S1-S4 are equal and fixed, the first switching tube S1 and the third switching tube S3 are complementarily conducted, the second switching tube S2 and the fourth switching tube S4 are complementarily conducted, the duty ratio of the first switching tube S1 is equal to the duty ratio of the second switching tube S2, both are smaller than 50% and 180% out of phase, the duty ratio of the third switching tube S3 is equal to the duty ratio of the fourth switching tube S4, both are larger than 50% and 180% out of phase, the control of the output voltage is realized by adjusting the duty ratio of the first switching tube S1, and the larger the duty ratio of the first switching tube S1 is, the larger the gain of the output voltage is.
In order to reduce the voltage stress of the drain-source electrodes of the first and second switching tubes S1, S2 during a large dynamic process and meet the output voltage protection requirement, the driving pulses of the first and second switching tubes S1, S2 are generally controlled by comparing the sampled input/output voltage with a reference threshold, but the response time of these protection actions is long relative to the switching frequency, and the short-time large dv/dt of the drain-source electrodes of the first and second switching tubes S1, S2 is enough to damage the switching tubes. When the converter starts, the input voltage is too high, the first resonant capacitor Cr1 and the second resonant capacitor Cr2 are respectively connected in parallel with the first resistor R1 and the second resistor R2 and then connected in series, and then connected in parallel with the input source Vin, the first resonant capacitor Cr1 and the second resonant capacitor Cr2 can be charged at the starting moment through a series loop of the input source Vin, the first resistor R1 and the second resistor R2, and the influence on the first switching tube S1 and the second switching tube S2 caused by the overlarge voltage transient change rate (dv/dt) of the drain-source electrodes of the first switching tube S1 and the second switching tube S2 at the starting moment can be effectively avoided through charging the first resonant capacitor Cr1 and the second resonant capacitor Cr2, so that the drain-source electrode stress of the first switching tube S1 and the second switching tube S2 at the starting moment can be effectively reduced, and a better protection effect on a system is further achieved.
The light and no-load efficiency of the switching power supply is a key index, and in order to reduce the power loss of the switching power supply during light and no-load and improve the efficiency, the switching power supply needs to be controlled to be in an intermittent working mode during light and no-load. When the wide-gain LLC resonant converter is in a high-voltage light-no-load Burst mode, if the incomplete discharge of the switching tube junction capacitance during the Burst pause period can cause the Burst start of the next period, the first to fourth switching tubes S1-S4 are in a hard switching state, ZVS cannot be realized, meanwhile, when there is tolerance in the first and second resonant capacitors Cr1, Cr2 or the equivalent resistances at the two ends of the first and second resonant capacitors Cr1, Cr2 are different (including the case of adding only the first resistor R1 in the embodiment), the voltages at the two ends of the resonant capacitors are asymmetric, thereby causing the asymmetric resonant current in the first several periods in the Burst mode, the large current spikes at the moment of turning on and off the first and second switching tubes S1, S2 damage the switching tubes, the circuit operating waveforms are shown in fig. 7, wherein VGS1 is the driving signal of the first switching tube S1, and Vds1 is the drain-source voltage of the first switching tube S1, ids1 drain-source current of the first switch tube S1, Ids2 drain-source current of the second switch tube S2, VCr1 is voltage across the first resonant capacitor Cr1, VCr2 is voltage across the second resonant capacitor Cr2, and Ir is resonant cavity current.
In this embodiment, after the first and second resistors R1 and R2 are added, voltage sharing is realized, so that voltages at two ends of the first and second resonant capacitors Cr1 and Cr2 are substantially the same, resonant currents of the first several cycles in the Burst mode are also symmetrical, and current spikes at the switching instants of the first and second switching tubes S1 and S2 are reduced by half, so that an effective protection effect is provided for a system, and a circuit operating waveform is as shown in fig. 8.
Third embodiment
A third embodiment of the present invention is shown in fig. 9, and this embodiment provides a half-bridge LLC converter based on a single resonant capacitor, which includes an input source Vin, a primary wide-gain LLC resonant circuit, a transformer, a secondary rectifying circuit, and an output load, which are connected in sequence from input to output. The difference from the first embodiment is that the resonant capacitor is a single resonant capacitor Cr1, the middle connection point after the first resistor R1 and the second resistor R2 are connected in series is connected with one end of the resonant capacitor Cr1, the drain of the fourth switch tube S4 and the synonym end of the primary winding Np of the transformer T, and the other end of the resonant capacitor Cr1 is connected with the second resistor R2, the source of the second switch tube S2 and the negative electrode of the input source Vin. The connection mode and the specific working principle of other components in this embodiment are the same as those in the first embodiment, and are not described herein again.
Fourth embodiment
A fourth embodiment of the present invention is shown in fig. 10, and this embodiment provides another half-bridge LLC resonant converter based on a single resonant capacitor, which includes an input source Vin, a primary wide-gain LLC resonant circuit, a transformer, a secondary rectifying circuit, and an output load, which are connected in sequence from input to output. The resonant capacitor of the transformer T also only has a single resonant capacitor Cr1, the middle connection point of the first resistor R1 and the second resistor R2 after being connected in series is connected with the middle connection point of the first switch tube S1 and the second switch tube S2 after being connected in series, and then is connected with one end of the resonant capacitor Cr1, the other end of the resonant capacitor Cr1 is connected with the drain of the third switch tube S3 and the resonant inductor Lr, the positive electrode of the input source Vin is connected with the first resistor R1 and the drain of the first switch tube S1, and the negative electrode of the input source Vin is connected with one end of the second resistor R2, the source of the second switch tube S2, the drain of the fourth switch tube S4 and the synonym end of the primary winding Np of the transformer T. The connection mode and the specific working principle of other components in this embodiment are the same as those in the first embodiment, and are not described herein again.
The wide-gain LLC resonant converters in the second to fourth embodiments disclosed in the present invention can achieve the above-mentioned beneficial effects in each switching cycle, as long as there is a voltage at two end points after the first resistor R1 and the second resistor R2 are connected in series, it can be ensured that the voltage at two ends of each resonant capacitor is about half of the input source Vin, the waveform symmetry is better, and the resonant cavity current stress is smaller, which plays a role in protecting the primary side switching tube, without time delay, and solves the problems of the prior art that the control circuit design is complex and the response of the protection circuit is delayed.
The invention not only solves the problems of large drain source electrode dv/dt of the primary side switch tube and asymmetric high-voltage light and no-load Burst mode resonant current when the machine is started at high voltage, effectively improves the stability and reliability of the wide-gain LLC resonant converter under the condition of ultra-wide input voltage, can simultaneously meet the high-gain range of the wide-gain LLC resonant converter, and further widens the application occasions of the wide-gain LLC resonant converter.
The above embodiments are only for the purpose of understanding the inventive concepts of the present application and are not intended to limit the present patent, and any modifications, equivalents, improvements and the like, which may be made by those skilled in the art without departing from the inventive concept, shall be included in the scope of the present patent.
Claims (10)
1. A half-bridge LLC resonant converter comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, and is characterized in that the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a first resonant capacitor, a second resonant capacitor, a resonant inductor and an excitation inductor;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resistor and the second resistor are connected in series and then connected in parallel to the positive electrode of the input end and the negative electrode of the input end, the first resonant capacitor is connected in parallel with the first resistor, and the second resonant capacitor is connected in parallel with the second resistor;
one end of the resonant inductor is connected to the source electrode of the first switching tube, the other end of the resonant inductor is connected to one end of the excitation inductor and one end of the primary winding of the transformer, and the other end of the excitation inductor is connected to the connection point of the first resistor and the second resistor and the other end of the primary winding of the transformer.
2. A half-bridge LLC resonant converter comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, and is characterized in that the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a resonant capacitor, a resonant inductor and an excitation inductor;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resistor and the second resistor are connected in series and then connected in parallel to the positive electrode of the input end and the negative electrode of the input end, one end of the resonance capacitor is connected to the source electrode of the second switching tube, the other end of the resonance capacitor is connected to one end of the excitation inductor, and the other end of the resonance capacitor is connected to the middle connection point of the first resistor and the second resistor;
one end of the resonant inductor is connected to the source electrode of the first switching tube, and the other end of the resonant inductor is connected to the other end of the excitation inductor.
3. A half-bridge LLC resonant converter comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, and is characterized in that the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a resonant capacitor, a resonant inductor and an excitation inductor;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resistor and the second resistor are connected in series and then connected to the anode of the input end and the cathode of the input end in parallel, and the middle connecting point of the first resistor and the second resistor is connected with the source electrode of the first switching tube; one end of the resonant capacitor is connected to the source electrode of the first switching tube, and the other end of the resonant capacitor is connected to one end of the resonant inductor;
the other end of the resonant inductor is connected to one end of the excitation inductor, and the other end of the excitation inductor is connected to the source electrode of the second switching tube.
4. A half-bridge LLC resonant converter comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, and is characterized in that the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a resistor, a resonant inductor, an excitation inductor, a first resonant capacitor, a second resonant capacitor and a clamping switch;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the first resonant capacitor and the second resonant capacitor are connected in series and then connected in parallel to the positive electrode of the input end and the negative electrode of the input end, and the resistor is connected in parallel with the first resonant capacitor;
one end of the resonant inductor is connected to the source electrode of the first switching tube, the other end of the resonant inductor is connected to one end of the excitation inductor, and the other end of the excitation inductor is connected to a connection point of the first resonant capacitor and the second resonant capacitor.
5. A half-bridge LLC resonant converter comprises a primary LLC resonant circuit, a transformer and a secondary rectification circuit which are sequentially connected from input to output, and is characterized in that the primary LLC resonant circuit comprises an input end anode, an input end cathode, a half-bridge switching circuit, a first resistor, a second resistor, a resonant inductor, an excitation inductor, a resonant capacitor and a clamping switch;
the half-bridge switching circuit is provided with a first switching tube and a second switching tube, the drain electrode of the first switching tube is connected to the positive electrode of the input end, the source electrode of the first switching tube is connected to the drain electrode of the second switching tube, and the source electrode of the second switching tube is connected to the negative electrode of the input end;
the method is characterized in that: the first resistor and the second resistor are connected in series and then connected to two ends of an input source in parallel, and a middle connection point of the first resistor and the second resistor is connected to one end of the resonant capacitor; one end of the resonant inductor is connected to the source electrode of the first switching tube, and the other end of the resonant inductor is connected to one end of the excitation inductor.
6. The half-bridge LLC resonant converter according to claim 5, wherein the resonant capacitor is formed by a single resonant capacitor, and an intermediate connection point of the series connection of the first resistor and the second resistor is connected to one end of the resonant capacitor.
7. The half-bridge LLC resonant converter of claim 5, wherein the resonant capacitor comprises a first resonant capacitor and a second resonant capacitor, the first resonant capacitor being connected in parallel with the first resistor, the second resonant capacitor being connected in parallel with the second resistor.
8. The half-bridge LLC resonant converter according to claim 6, further comprising a clamping circuit, wherein the clamping circuit is composed of a third switching tube and a fourth switching tube connected in series in an opposite direction, and a middle connection point of the series connection of the first resistor and the second resistor is respectively connected with a drain electrode of the fourth switching tube and one end of the primary winding of the transformer.
9. The half-bridge LLC resonant converter of claim 1, wherein the secondary rectification circuit is a full-wave rectification structure or a full-bridge rectification structure; the secondary side rectifying circuit comprises a switching tube which is an MOS tube or a diode.
10. The half bridge LLC resonant converter of claim, wherein said first and second resistors have the same resistance.
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