CN112087147A - Converter wide gain control method and application thereof - Google Patents
Converter wide gain control method and application thereof Download PDFInfo
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- CN112087147A CN112087147A CN202011039113.4A CN202011039113A CN112087147A CN 112087147 A CN112087147 A CN 112087147A CN 202011039113 A CN202011039113 A CN 202011039113A CN 112087147 A CN112087147 A CN 112087147A
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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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- 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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Abstract
The invention provides a wide gain control method of a converter, which is applied to an LLC resonant converter consisting of an inverter circuit, a resonant circuit, an auxiliary branch circuit, a transformer and a rectification filter circuit, wherein the method divides an input voltage into a low voltage section and a high voltage section, and the low voltage section and the high voltage section respectively correspond to two modes: when the voltage is input into the low-voltage section, the frequency conversion PFM is adopted for control, and the gain of the output voltage is changed by changing the switching frequency; when the high-voltage section of the input voltage is input, the constant-frequency duty ratio shift PWM control is adopted, and the output voltage gain is changed by changing the duty ratio. According to the invention, through switching of frequency conversion PFM and fixed frequency PWM control, the voltage gain range of the converter can be widened, ZVS can be realized on all switching tubes, and the overall efficiency of the circuit is higher; the control mode of the invention is simple, and the clamping mode of the single switch tube can effectively reduce the cost of the converter; compared with single PFM control, the frequency variation range of the invention is smaller when the same output voltage gain is achieved, and the design requirements of magnetic core elements such as a transformer are reduced.
Description
Technical Field
The invention relates to the technical field of switching converters, in particular to a converter wide gain control method and application thereof.
Background
With the development of power electronic technology, the switching converter is also gradually developed to a higher power density direction, which needs to further increase the switching frequency of the converter to reduce the size of the passive device, and an important factor limiting the increase of the switching frequency is the switching loss of the switching device, such as the switching loss of a MOS transistor.
In order to reduce the switching losses, LLC resonant converters have been developed vigorously. The converter can realize zero voltage switching-on (hereinafter referred to as ZVS) of the switching tube, thereby greatly reducing the switching loss at high frequency. However, in the conventional half-bridge LLC resonant converter, the output voltage gain is changed by changing the frequency, and when the input voltage and load change range is wide, the frequency change range of the converter is large, which greatly increases the difficulty in designing the magnetic device of the converter. Therefore, the traditional half-bridge LLC resonant converter has great limitation and is difficult to be applied to wide input voltage occasions.
Aiming at the problem that the input voltage of the LLC resonant converter is limited, related research is carried out in the industry at present, the output voltage gain range of the LLC resonant converter is widened by changing the form of topology, and wide-voltage input is realized.
A variable-mode control method is provided in 'a wide gain control method of a variable-topology LLC resonant converter' with the patent number of CN110768535, and is applied to a full-bridge LLC converter, and the wide voltage gain is realized by detecting input voltage and changing a topology structure and a control mode. However, in the control method, the auxiliary branch needs two switching tubes, and the logic time sequences of the main switch and the auxiliary switch must be strictly controlled, so that the control mode is complex; meanwhile, the switch tube on the auxiliary branch needs to be driven in an isolation mode, and the complexity of the circuit is further increased.
The patent number CN100421344C "zero voltage switch half-bridge dc-dc converter topology" proposes a half-bridge LLC resonant converter with an auxiliary branch, the auxiliary branch of the converter is composed of a diode and a switching tube, and through the clamping effect of the auxiliary branch, the topology can realize ZVS of all switching tubes, but still cannot solve the problem of limitation when the LLC resonant converter is applied to a wide input voltage.
Disclosure of Invention
The invention provides a converter wide gain control method and application thereof, aiming at solving the problem that the voltage gain range of the existing LLC resonant converter is narrow.
The technical scheme adopted by the invention is as follows:
a wide gain control method of a converter is applied to an LLC resonant converter consisting of an inverter circuit, a resonant circuit, an auxiliary branch circuit, a transformer and a rectification filter circuit, wherein the inverter circuit comprises a switching tube S1 and a switching tube S2, the resonant circuit comprises a resonant inductor Lr, an excitation inductor Lm and a resonant capacitor Cr, the auxiliary branch circuit comprises a clamping diode D1 and a clamping switching tube S3, the rectification filter circuit is connected in series with two ends of a secondary winding of the transformer, a drain electrode of the switching tube S1 is connected with an anode of an input power Vin, a source electrode of a switching tube S1 is connected with a drain electrode of the switching tube S2 and one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected with one end of the resonant inductor Lr, the other end of the resonant inductor Lr is connected with one end of the excitation inductor Lm and a 1 end of a primary winding of the transformer, a 2 end of the primary winding of the transformer is connected with the other end of the excitation inductor Lm, the source electrode, the clamping diode D1 and the clamping switch tube S3 are connected in series and then bridged at the 1 end and the 2 end of the primary winding of the transformer, wherein the anode of the clamping diode D1 is connected with the connection point of the other end of the resonant capacitor Cr and one end of the resonant inductor Lr, the cathode of the clamping diode D1 is connected with the drain of the clamping switch tube S3, and the source of the clamping switch tube S3 is connected with the 2 end of the primary winding of the transformer;
divide into low and high two voltage sections with the input voltage range, correspond two kinds of different modals respectively:
the LLC resonant converter adopts frequency conversion PFM control in the low-voltage section of input voltage, and changes the gain of output voltage by changing the switching frequency;
the LLC resonant converter adopts the constant-frequency duty ratio shift PWM control in the high-voltage section of the input voltage, and the output voltage gain is changed by changing the duty ratio.
The frequency conversion PFM control is specifically that the clamping switch tube S3 is continuously turned off, the auxiliary branch does not work, the duty ratios of the switch tube S1 and the switch tube S2 are equal and fixed, and the switch tube S1 and the switch tube S2 are complementarily turned on.
The duty cycle of the switch tube S1 and the switch tube S2 are equal and specifically, the duty cycle of the switch tube S1 and the switch tube S2 are both 0.5.
The switching frequency is changed specifically by changing the switching frequency of the switching tube S1 and the switching tube S2.
The constant-frequency duty ratio shift PWM control is specifically that the switching frequency of the switching tube S1 and the switching tube S2 are equal and the duty ratio is equal, after the switching tube S1 is turned off, the switching tube S2 is turned on immediately, and the switching tube S1 and the clamping switching tube S3 are turned on complementarily.
The duty cycle is changed by changing the duty cycles of the switching tubes S1, S2 and S3.
An application of a wide gain control method of a converter is applied to an LLC resonant converter composed of an inverter circuit, a resonant circuit, an auxiliary branch circuit, a transformer and a rectification filter circuit, wherein the inverter circuit comprises a switching tube S1 and a switching tube S2, the resonant circuit comprises a resonant inductor Lr, an excitation inductor Lm and a resonant capacitor Cr, the auxiliary branch circuit comprises a clamping diode D1 and a clamping switching tube S3, the rectification filter circuit comprises a diode D2, a diode D3 and a capacitor C0, the drain electrode of the switching tube S1 is connected with the anode of an input power Vin, the source electrode of the switching tube S1 is connected with the drain electrode of the switching tube S2 and one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected with one end of the resonant inductor Lr, the other end of the resonant inductor Lr is connected with one end of the excitation inductor Lm and the 1 end of the primary side of the transformer, the 2 end of the winding of the transformer is connected with, The source of the switching tube S2 is connected with the cathode of the input power Vin, the clamping diode D1 and the clamping switching tube S3 are connected in series and then bridged across the 1 end and the 2 end of the primary winding of the transformer, wherein the anode of the clamping diode D1 is connected with the connection point of the other end of the resonant capacitor Cr and one end of the resonant inductor Lr, the cathode of the clamping diode D1 is connected with the drain of the clamping switching tube S3, the source of the clamping switching tube S3 is connected with the 2 end of the primary winding of the transformer, the secondary winding of the transformer is formed by connecting a secondary first winding and a secondary second winding in series, the dotted end of the secondary second winding is connected with the synonym end of the secondary first winding, the anode of the diode D2 is connected with the dotted end of the secondary first winding, the cathode of the diode D2 is connected with the cathode of the diode D3 and one end of the capacitor C0, the other end of the capacitor C0 is connected with the connection point of the secondary first winding and the dotted end of the secondary second winding, the anode of the diode D,
when the input voltage of an input power Vin is a low-voltage section, the circuit works in a frequency conversion PFM control mode, a clamping switch tube S3 is continuously turned off, an auxiliary branch does not work, the duty ratios of a switch tube S1 and a switch tube S2 are equal and fixed, the switch tube S1 and the switch tube S2 are complementarily turned on, the switching frequency of the switch tube S1 and the switching frequency of the switch tube S2 are adjusted to realize the control of the output voltage, and the smaller the switching frequency is, the larger the gain of the output voltage is;
when the input voltage of an input power Vin is in a high-voltage section, the circuit works in a fixed-frequency PWM control mode, the switching frequency of the switching tube S1 is equal to that of the switching tube S2, the duty ratio of the switching tube S1 is equal to that of the switching tube S2, the switching tube S2 is immediately conducted after the switching tube S1 is turned off, the switching tube S1 and the clamping switching tube S3 are conducted in a complementary mode, the duty ratio of the switching tube S1 is adjusted, the conducting time of the clamping switching tube S3 can be changed synchronously, the output voltage is controlled, and the larger the duty ratio of the switching tube S1 is, the larger the output.
A wide gain control method for converter is applied to half-bridge LLC resonant converter, and is characterized by that the input voltage range is divided into low and high voltage sections,
when the input voltage is in a low-voltage section, the half-bridge LLC resonant converter adopts a variable-frequency PFM control mode, namely two switching tubes of a half bridge are complementarily conducted, the output voltage gain is changed by changing the switching frequency of the switching tubes, and the smaller the switching frequency of the switching tubes is, the larger the output voltage gain is;
when the input voltage is in a high-voltage section, the half-bridge LLC resonant converter adopts a PWM control mode, namely two switching tubes of a half bridge are in complementary conduction, the output voltage gain is changed by changing the duty ratio of the switching tubes, and the larger the duty ratio of the switching tubes is, the larger the output voltage gain is.
Advantageous effects
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in:
by switching the control of the frequency conversion PFM and the fixed frequency PWM, the voltage gain range of the converter can be widened, ZVS can be realized by all the switching tubes, and the overall efficiency of the circuit is higher;
compared with the traditional double-switch tube clamping mode, the control mode of the invention is simple, and the clamping mode of a single switch tube can effectively reduce the cost of the converter;
compared with the traditional half-bridge LLC resonant topology single PFM control, the control method has smaller frequency change range when reaching the same output voltage gain range, and greatly reduces the design requirements of magnetic core elements such as a transformer and the like;
compared with the traditional PFM control, the control method has the advantages of wider voltage gain range, simple design and higher overall efficiency, and is suitable for being applied to wide-voltage and high-power occasions.
Drawings
FIG. 1 is a gain profile of a circuit employing the method of the present invention;
FIG. 2 is a schematic circuit diagram of a half-bridge LLC resonant converter using the method of the invention;
FIG. 3 is a diagram of the main operating waveforms of a half-bridge LLC resonant converter using the method of the invention in low-voltage PFM control;
FIGS. 4 to 9 are equivalent circuit diagrams of switching modes of a half-bridge LLC resonant converter using the method of the invention in low-voltage PFM control;
FIG. 10 is a diagram of the main operating waveforms of a half-bridge LLC resonant converter using the method of the invention in high voltage PWM control;
fig. 11 to 17 are equivalent circuit diagrams of each switching mode of the half-bridge LLC resonant converter using the method of the present invention in the high-voltage PWM control.
Detailed Description
As shown in fig. 2, the circuit schematic diagram of the half-bridge LLC resonant converter applying the method of the present invention includes a slave inverter circuit 10, a resonant circuit 20, an auxiliary branch circuit 30, a transformer T, and a rectifier filter circuit 40. Vin in fig. 2 is an input power source, and the resistor Ro is a load.
The inverter circuit 10 is a half-bridge structure circuit composed of a switch tube S1 and a switch tube S2, the resonant circuit 20 includes a resonant inductor Lr, an excitation inductor Lm and a resonant capacitor Cr, the auxiliary branch 30 includes a clamp diode D1 and a clamp switch tube S3, and the rectifying and filtering circuit 40 includes a rectifying module and a filtering module, wherein the rectifying module is composed of a diode D2 and a diode D3 and is full-wave rectification, and the filtering module is composed of a capacitor C0.
The specific circuit connection mode is as follows:
the drain electrode of the switch tube S1 is connected with the positive electrode of an input power Vin, the source electrode of the switch tube S1 is connected with the drain electrode of the switch tube S2 and one end of a resonance capacitor Cr, the other end of the resonance capacitor Cr is connected with one end of a resonance inductor Lr, the other end of the resonance inductor Lr is connected with one end of an excitation inductor Lm and one end of a primary winding of a transformer T, the 2 end of the primary winding of the transformer T is connected with the other end of the excitation inductor Lm, the source electrode of the switch tube S2 is connected with the negative electrode of the input power Vin, a clamping diode D1 and a clamping switch tube S3 are connected in series and then bridged with the 1 end and the 2 end of the primary winding of the transformer T, wherein the anode of a clamping diode D1 is connected with the connecting point of the other end of the resonance capacitor Cr and one end of the resonance inductor Lr, the cathode of a clamping diode D1 is connected with the drain electrode of a clamping, the secondary winding of the transformer T is formed by connecting a secondary first winding and a secondary second winding in series, the dotted terminal of the secondary second winding is connected with the different-dotted terminal of the secondary first winding, the anode of a diode D2 is connected with the dotted terminal of the secondary first winding, the cathode of a diode D2 is connected with the cathode of a diode D3 and one end of a capacitor C0, the other end of the capacitor C0 is connected with the connection point of the secondary first winding and the secondary second winding, the anode of a diode D3 is connected with the different-dotted terminal of the secondary second winding, and a resistor R0 is connected with the capacitor C0 in parallel.
The specific control method comprises the following steps:
the input voltage range is divided into a low voltage section and a high voltage section which respectively correspond to two different modes.
When the half-bridge LLC resonant converter is in an input voltage low-voltage section, the variable frequency PFM control is adopted, and the output voltage gain is changed by changing the switching frequency;
the half-bridge LLC resonant converter adopts fixed frequency PWM control to change the output voltage gain by changing the duty ratio in the high-voltage section of the input voltage.
When the input voltage is in a low-voltage section, the circuit works in a frequency conversion PFM control mode, the clamping switch tube S3 is continuously turned off, the auxiliary branch does not work, the duty ratios of the switch tube S1 and the switch tube S2 are equal and fixed and are both about 50%, the switch tube S1 and the switch tube S2 are complementarily turned on, the control of the output voltage is realized by adjusting the switching frequencies of the switch tube S1 and the switch tube S2, and the smaller the switching frequency is, the larger the gain of the output voltage is;
when the input voltage is in a high-voltage section, the circuit works in a fixed-frequency PWM control mode, the switching frequencies of the switching tubes S1 and S2 are equal, the duty ratios are equal, after the switching tube S1 is turned off, the switching tube S2 is immediately turned on, the switching tube S1 and the clamping switching tube S3 are complementarily turned on, the duty ratio of the switching tube S1 is adjusted, the turn-on time of the clamping switching tube S3 is synchronously changed, the control of the output voltage is realized, and the larger the duty ratio of the switching tube S1 is, the larger the gain of the output voltage is.
The operation of the half-bridge LLC resonant converter using the method of the present invention at low voltage and high voltage is specifically described below with reference to the accompanying drawings.
When the input voltage of the converter is low voltage, the half-bridge LLC resonant converter works in a PFM control mode, at this time, the clamp switching tube S3 remains off, that is, the auxiliary branch 30 does not work, fig. 3 is a main working waveform diagram when the input voltage of the half-bridge LLC resonant converter is low voltage and the PFM control mode is adopted, where Vgs1 is a control signal of the switching tube S1, Vgs2 is a control signal of the switching tube S2, ip is a primary side current of the transformer, im is a primary side excitation current of the transformer, VA is an a-point voltage, and Io is a secondary side current of the transformer, and according to the working state, the converter has seven switching modes in one switching period, which are shown in fig. 4 to 9, respectively.
Switching mode 1(t0, t 1): as shown in fig. 4a, at time t0, the switch tube S2 is turned off, the primary side current of the transformer discharges the parasitic capacitor of the switch tube S1 and charges the parasitic capacitor of the switch tube S2 until the voltage across the parasitic capacitor of the switch tube S1 is zero, the body diode of the switch tube S1 is turned on (as shown in fig. 4 b), a condition is provided for the switch tube S1 to be turned on at zero voltage, the diode D2 in the secondary side circuit is turned on at this stage, and the diode D3 is turned off.
Switching mode 2(t1, t 2): as shown in fig. 5, at time t1, the switch tube S1 is turned on at zero voltage, the primary side of the transformer is connected to the input power source through the switch tube S1, forward excitation is performed, the diode D2 in the secondary side circuit is turned on, and the diode D3 is turned off.
Switching mode 3(t2, t 3): as shown in fig. 6, at time t2, the switching tube S1 is still turned on, the diode D2 and the diode D3 are in an off state, the primary side excitation current is equal to the resonance current, the excitation inductor Lm, the resonance inductor Lr and the resonance capacitor Cr participate in resonance, and the diode D2 realizes ZCS.
Switching mode 4(t3, t 4): as shown in fig. 7a, at time t3, the switching tube S1 is turned off, the primary side current of the transformer charges the parasitic capacitor of the switching tube S1, and discharges the parasitic capacitor of the switching tube S2, until the voltage across the parasitic capacitor of the switching tube S2 is zero, the body diode of the switching tube S2 is turned on (as shown in fig. 7 b), and a zero-voltage turn-on condition is provided for the switching tube S2.
Switching mode 5(t4, t 5): as shown in fig. 8, at time t4, the switch tube S2 is turned on at zero voltage, the primary side of the transformer receives reverse voltage, the diode D3 in the secondary side circuit is turned on, and the diode D2 is turned off.
Switching mode 6(t5, t 6): as shown in fig. 9, at time t5, the switching tube S2 is still turned on, and the diode D2 and the diode D3 are in an off state, and at this stage, the primary side excitation current is equal to the resonance current, and at this time, the excitation inductor Lm, the resonance inductor Lr and the resonance capacitor Cr participate in resonance, and the diode D3 realizes ZCS.
The traditional half-bridge resonant converter only works in an up-conversion PFM mode, when input voltage rises, in order to stabilize output voltage, the resonant frequency of the converter rises to reduce output voltage gain, if the input voltage is too high and exceeds the range of 1:2, the change range of the resonant frequency is required to be wider, the magnetic core is required to work in a wider frequency range, and the design difficulty of the magnetic core is greatly improved. In the invention, in order to widen the gain range of the output voltage, when the input voltage is increased to a certain value, the gain of the output voltage is reduced by reducing the duty ratio of the switching tube, and the stability of the output voltage at high voltage can be ensured without further changing the switching frequency.
When the input voltage of the converter is high, the converter works in a PWM control mode, and FIG. 10 is a main working waveform diagram of the converter in low-voltage PWMWherein Vgs1 is a control signal of the switching tube S1, Vgs2 is a control signal of the switching tube S2, Vgs3 is a control signal of the clamping switching tube S3, ip is a primary current of the transformer, and V isCBFor the voltage between two points CB, the converter has seven switching modes in one switching cycle according to the operating state, which are shown in fig. 11 to 17.
Switching mode 1(t0, t 1): as shown in fig. 11, at time t0, the switching tube S1 is turned on at zero voltage, the input power source excites the primary winding of the transformer through the switching tube S1, and at this stage, the primary current ip of the transformer is from left to right, the diode D2 in the secondary circuit is turned on, and the diode D3 is turned off in the reverse direction.
Switching mode 2(t1, t 2): as shown in fig. 12a, at time t1, the switching tube S1 is turned off, the primary current charges the parasitic capacitance of the switching tube S1 and discharges the parasitic capacitance of the switching tube S2, when the voltage drop across the parasitic capacitance of the switching tube S2 becomes zero, the body diode of the switching tube S2 is turned on (as shown in fig. 12 b), providing a zero-voltage turn-on condition for the switching tube S2, and during this time, the diode D2 and the diode D3 in the secondary circuit are turned off, and follow current is output from the capacitor Co.
Switching mode 3(t2, t 3): as shown in fig. 13, at time t2, when switch S2 is turned on at zero voltage, switch S2 is turned on, the primary side current of the transformer is reduced to zero and is reversed, and when the primary side current reaches the current reflected by the secondary side current, diode D3 is turned on, during which diode D2 is reversed.
Switching mode 4(t3, t 4): as shown in fig. 14, at time t3, clamp switch S3 is on, but since switch S2 is still on, no current flows through the auxiliary branch at this stage.
Switching mode 5(t4, t 5): as shown in fig. 15, at time T4, the switch tube S2 is turned off, the clamp switch tube S3 is turned on, and the primary current of the transformer T discharges the parasitic capacitance of the switch tube S1 and charges the parasitic capacitance of the switch tube S2.
Switching mode 6(t5, t 6): as shown in fig. 16, at time t5, the clamp switching tube S3 is turned on, the voltage across the parasitic capacitor of the switching tube S2 is charged to the voltage of the resonant capacitor Cr, the clamp diode D1 is turned on, the primary current flows through the auxiliary branch, and the transformer leakage inductance energy is clamped by the auxiliary branch, during which time, the diode D2 and the diode D3 in the secondary circuit are both turned off.
Switching mode 7(t6, t 7): as shown in fig. 17a, at time t6, the clamping switch tube S3 is turned off, the primary side current of the transformer charges the parasitic capacitance of the switch tube S2 and the parasitic capacitance of the switch tube S3, and discharges the parasitic capacitance of the switch tube S1, and when the voltage across the parasitic capacitance of the switch tube S1 is discharged to zero, the body diode of the switch tube S1 is turned on (as shown in fig. 17 b), so as to provide a zero-voltage turn-on condition for the switch tube S1.
It can be seen that in the high-voltage section of the input voltage, the frequency of the switching tube is kept fixed, the output voltage gain is reduced along with the rise of the voltage by adjusting the duty ratio of the switching tube, and the stability of the output voltage at the high voltage is ensured.
According to the working process of the converter, the half-bridge resonant converter can realize zero-voltage switching-on of all the switching tubes, and meanwhile, the gain range of the output voltage is widened on the basis of the half-bridge resonant converter. In order to meet the design requirements and reduce the requirements of a magnetic core, the traditional half-bridge LLC resonant converter has an input voltage range of 1:2 or even narrower, and the input voltage range of the half-bridge LLC resonant converter adopting the control method can reach 1:4 or even higher.
The invention adopts a control mode of combining PFM and PWM, when being applied to a half-bridge resonant converter, on one hand, the invention can exert the advantages of the resonant converter to realize the soft switching of all switch tubes, on the other hand, the invention also overcomes the defect of narrower voltage gain range of the resonant converter, and is suitable for high-power, high-voltage and high-power occasions.
The above embodiments are only for the understanding of the inventive concept of the present application and are not intended to limit the present invention, and any modification, equivalent replacement, improvement, etc. made by those skilled in the art without departing from the principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A wide gain control method of a converter is applied to an LLC resonant converter composed of an inverter circuit, a resonant circuit, an auxiliary branch circuit, a transformer and a rectification filter circuit, wherein the inverter circuit comprises a switch tube S1 and a switch tube S2, the resonant circuit comprises a resonant inductor Lr, an excitation inductor Lm and a resonant capacitor Cr, the auxiliary branch circuit comprises a clamping diode D1 and a clamping switch tube S3, the rectification filter circuit is connected in series with two ends of a secondary winding of the transformer, a drain electrode of the switch tube S1 is connected with an anode of an input power Vin, a source electrode of the switch tube S1 is connected with a drain electrode of a switch tube S2 and one end of a resonant capacitor Cr, the other end of the resonant capacitor Cr is connected with one end of the resonant inductor Lr, the other end of the resonant inductor Lr is connected with one end of the excitation inductor Lm and a 1 end of a primary winding of the transformer, and a 2 end of a primary winding of the transformer, The source electrode of the switch tube S2 is connected with the negative electrode of the input power Vin, the clamping diode D1 and the clamping switch tube S3 are connected in series and then bridged to the 1 end and the 2 end of the primary winding of the transformer, wherein the anode of the clamping diode D1 is connected with the connecting point of the other end of the resonant capacitor Cr and one end of the resonant inductor Lr, the cathode of the clamping diode D1 is connected with the drain electrode of the clamping switch tube S3, and the source electrode of the clamping switch tube S3 is connected with the 2 end of the primary winding of the transformer;
the method is characterized in that the input voltage range is divided into a low voltage section and a high voltage section which respectively correspond to two different modes:
the LLC resonant converter adopts frequency conversion PFM control in the low-voltage section of input voltage, and changes the gain of output voltage by changing the switching frequency;
the LLC resonant converter adopts the constant-frequency duty ratio shift PWM control in the high-voltage section of the input voltage, and the output voltage gain is changed by changing the duty ratio.
2. The converter wide gain control method of claim 1, wherein: the frequency conversion PFM control is specifically that the clamping switch tube S3 is continuously turned off, the auxiliary branch does not work, the duty ratios of the switch tube S1 and the switch tube S2 are equal and fixed, and the switch tube S1 and the switch tube S2 are complementarily turned on.
3. The converter gain control method of claim 2, wherein: the duty cycles of the switch tube S1 and the switch tube S2 are equal, and specifically, the duty cycles of the switch tube S1 and the switch tube S2 are both 0.5.
4. The converter wide gain control method of claim 1, wherein: the changing of the switching frequency specifically changes the switching frequency of the switching tube S1 and the switching tube S2.
5. The converter wide gain control method of claim 1, wherein: the constant-frequency duty ratio shift PWM control is characterized in that the switching frequency of the switching tube S1 is equal to that of the switching tube S2, the duty ratio of the switching tube S2 is equal to that of the switching tube S1, the switching tube S2 is immediately conducted, and the switching tube S1 and the clamping switching tube S3 are conducted in a complementary mode.
6. The converter wide gain control method of claim 1, wherein: the changing duty cycle is to change the duty cycles of the switching tubes S1, S2 and S3.
7. An application of a wide gain control method of a converter is applied to an LLC resonant converter composed of an inverter circuit, a resonant circuit, an auxiliary branch circuit, a transformer and a rectification filter circuit, wherein the inverter circuit comprises a switching tube S1 and a switching tube S2, the resonant circuit comprises a resonant inductor Lr, an excitation inductor Lm and a resonant capacitor Cr, the auxiliary branch circuit comprises a clamping diode D1 and a clamping switching tube S3, the rectification filter circuit comprises a diode D2, a diode D3 and a capacitor C0, the drain electrode of the switching tube S1 is connected with the anode of an input power Vin, the source electrode of the switching tube S1 is connected with the drain electrode of the switching tube S2 and one end of the resonant capacitor Cr, the other end of the resonant capacitor Cr is connected with one end of the resonant inductor Lr, the other end of the resonant inductor Lr is connected with one end of the excitation inductor Lm and the 1 end of the primary side of the transformer, the 2 end of the winding of the transformer is connected with, The source of the switching tube S2 is connected with the cathode of the input power Vin, the clamping diode D1 and the clamping switching tube S3 are connected in series and then bridged across the 1 end and the 2 end of the primary winding of the transformer, wherein the anode of the clamping diode D1 is connected with the connection point of the other end of the resonant capacitor Cr and one end of the resonant inductor Lr, the cathode of the clamping diode D1 is connected with the drain of the clamping switching tube S3, the source of the clamping switching tube S3 is connected with the 2 end of the primary winding of the transformer, the secondary winding of the transformer is formed by connecting a secondary first winding and a secondary second winding in series, the dotted end of the secondary second winding is connected with the synonym end of the secondary first winding, the anode of the diode D2 is connected with the dotted end of the secondary first winding, the cathode of the diode D2 is connected with the cathode of the diode D3 and one end of the capacitor C0, the other end of the capacitor C0 is connected with the connection point of the secondary first winding and the dotted end of the secondary second winding, the anode of the diode D,
when the input voltage of an input power Vin is a low-voltage section, the circuit works in a frequency conversion PFM control mode, a clamping switch tube S3 is continuously turned off, an auxiliary branch does not work, the duty ratios of a switch tube S1 and a switch tube S2 are equal and fixed, the switch tube S1 and the switch tube S2 are complementarily turned on, the switching frequency of the switch tube S1 and the switching frequency of the switch tube S2 are adjusted to realize the control of the output voltage, and the smaller the switching frequency is, the larger the gain of the output voltage is;
when the input voltage of an input power Vin is in a high-voltage section, the circuit works in a fixed-frequency PWM control mode, the switching frequency of the switching tube S1 is equal to that of the switching tube S2, the duty ratio of the switching tube S1 is equal to that of the switching tube S2, the switching tube S2 is immediately conducted after the switching tube S1 is turned off, the switching tube S1 and the clamping switching tube S3 are conducted in a complementary mode, the duty ratio of the switching tube S1 is adjusted, the conducting time of the clamping switching tube S3 can be changed synchronously, the output voltage is controlled, and the larger the duty ratio of the switching tube S1 is, the larger the output.
8. A wide gain control method for converter is applied to half-bridge LLC resonant converter, and is characterized by that the input voltage range is divided into low and high voltage sections,
when the input voltage is in a low-voltage section, the half-bridge LLC resonant converter adopts a variable-frequency PFM control mode, namely two switching tubes of a half bridge are complementarily conducted, the output voltage gain is changed by changing the switching frequency of the switching tubes, and the smaller the switching frequency of the switching tubes is, the larger the output voltage gain is;
when the input voltage is in a high-voltage section, the half-bridge LLC resonant converter adopts a PWM control mode, namely two switching tubes of a half bridge are in complementary conduction, the output voltage gain is changed by changing the duty ratio of the switching tubes, and the larger the duty ratio of the switching tubes is, the larger the output voltage gain is.
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