CN112072921A

CN112072921A - Primary side regulation control system and control method of double-clamping ZVS Buck-Boost converter

Info

Publication number: CN112072921A
Application number: CN202010830452.8A
Authority: CN
Inventors: 孙伟锋; 丁松; 谷诚; 杨兰兰; 钱钦松; 时龙兴
Original assignee: Southeast University
Current assignee: Southeast University
Priority date: 2020-08-18
Filing date: 2020-08-18
Publication date: 2020-12-11

Abstract

The invention discloses a primary side regulation control system and a primary side regulation control method of a double-clamping ZVS Buck-Boost converter, and belongs to the technical field of power generation, power transformation or power distribution. The control system comprises a sampling and signal processing circuit, a control circuit taking a microcontroller as a core and a gate driver; the control method can accurately predict and calculate the secondary output voltage and the secondary output current according to the primary sampling value of the double-clamping ZVS Buck-Boost converter, so that accurate constant voltage or constant current control is realized. The double-clamping ZVS Buck-Boost converter primary side regulation control system and the control method thereof reduce the use of an optical coupler and other isolation elements while ensuring the working efficiency of the converter, improve the system integration level and can obtain very high output voltage precision and output current precision.

Description

Primary side regulation control system and control method of double-clamping ZVS Buck-Boost converter

Technical Field

The invention relates to a primary side regulation control technology of a switching converter, in particular to a primary side regulation control system and a control method of a double-clamping ZVS Buck-Boost converter, and belongs to the technical field of power generation, power transformation or power distribution.

Background

With the continuous development of information technology, various power supply devices objectively require miniaturization, light weight and improved reliability, and improving the efficiency and power density of a distributed power supply module is an important direction for the development of the power supply module. Currently, the chip-type power module is a development direction of the distributed power module, i.e. a new packaging technology is used to greatly reduce the size of the converter and increase the power density.

The main topology of the double-clamping ZVS Buck-Boost converter is shown in FIG. 1 and comprises the following components: a main power circuit composed of a main transformer T, a clamp circuit, and an output rectifier circuit₁Connected with the main switch tube, and the clamping circuit is composed of a clamping switch tube Q₃And a clamp capacitor C_clampConnected to form an output rectifying circuit comprising a synchronous rectifying tube Q₅And an output capacitor C_outAnd connecting to form the product. Therefore, the double-clamping ZVS Buck-Boost topology is a type of flyback topology, and is mainly characterized in that the equivalent leakage inductance of the primary winding of the transformer and the resonance of the clamping capacitor are utilized, the energy in the leakage inductance is absorbed and stored in the converter, and therefore the efficiency of the converter is improved, and the slew rate of the secondary current is limited. Meanwhile, the double-clamping ZVS Buck-Boost topology can realize ZVS starting of the primary side switching tube and the secondary side synchronous rectifier tube, so that the efficiency of the converter is further improved, and the heating loss of the system is reduced.

Sampling and regulation control are carried out on the primary side of the converter, so that the use of isolation elements such as an optical coupler and the like can be reduced, the circuit structure becomes simpler and is easy to design, and therefore, a primary side regulation control system is widely adopted in a flyback converter. However, for a double-clamp ZVS Buck-Boost converter with a complex working state and a nonlinear change of current waveform, how to obtain accurate output voltage and output current by collecting a voltage and current signal of a primary side of the converter is a difficulty of primary side sampling regulation control. Meanwhile, considering that the main advantage of the double-clamp ZVS Buck-Boost converter is that ZVS of the switching tube can be realized under complex working conditions to realize smaller switching loss, how to use the simplest detection sampling scheme to realize complete or partial ZVS of the switching tube is also the key point of control strategy design.

At present, the primary side sampling scheme adopted in the DCM module is to calculate the secondary side output voltage by sampling the voltage of the primary side clamping capacitor, thereby realizing the constant voltage output. The DCM module of Vicor company is a DC-DC module which adopts a double-clamping ZVS Buck-Boost topology disclosed by US patent US7561446B1, can realize high-frequency and high-efficiency voltage regulation, the adopted scheme of primary side sampling feedback control of a converter is shown in US patent US7859859B2, referring to fig. 11, a complex sampling circuit formed by an RS trigger and a gate device is used for collecting primary side voltage, only constant voltage output can be realized, besides a main switching tube, a clamping switching tube and a synchronous rectifier tube, a switching tube S1 is additionally used for forming a sampling holding circuit, and the complexity of the sampling circuit is increased; the voltage sampling stage added between the energy transmission stage and the ZVS B stage ensures that Q is obtained₃、Q₅The switching states of the tubes are not completely synchronous, affecting Q₄ZVS of (d) is turned on, increasing losses. Aiming at the defects in the prior art, the primary side regulation control system and the control method of the double-clamping ZVS Buck-Boost converter are provided, so that high-frequency and high-efficiency constant-current or constant-voltage output can be realized, and the system and the method have important significance for improving the power density and reducing the volume of the double-clamping ZVS Buck-Boost converter.

Disclosure of Invention

The invention aims to provide a primary side regulation control system and a control method of a double-clamping ZVS Buck-Boost converter aiming at the defects of the background technology, which sample primary side current and primary side voltage through less hardware resources and accurately calculate output voltage and output current, thereby realizing accurate constant voltage or constant current control of the double-clamping ZVS Buck-Boost converter, improving the power density of the system, reducing power consumption and solving the technical problems that the existing primary side sampling control scheme can not only realize constant voltage output but also realize constant current output and the control circuit is complicated.

The invention adopts the following technical scheme for realizing the aim of the invention:

for simplicity and clarity of description, in all expressions of the invention, four switching tubes of an H-type full bridge formed by a primary side and a primary side winding of a double-clamping ZVS Buck-boost converter are respectively defined as a first main switching tube, a second main switching tube, a clamping switching tube and a fourth main switching tube, one bridge arm formed by connecting the first main switching tube and the second main switching tube in series is connected to two ends of a direct-current input power supply in parallel, the other bridge arm formed by connecting the clamping switching tube and the fourth main switching tube in series is connected between two stages of a clamping capacitor in parallel, a primary side winding of a transformer is connected between midpoints of the two bridge arms, and a synchronous rectifier tube is connected in a secondary side loop of the transformer.

A primary side regulation control system of a double-clamping ZVS Buck-Boost converter comprises: the device comprises an inductive current detection module, a source-drain voltage detection module for detecting drain-source voltage of each switch tube on an H bridge, a clamping voltage detection module for detecting voltage of a clamping capacitor, an input voltage detection module, a secondary side synchronous rectification circuit, an auxiliary winding and logic circuit, a timer, a gate driver and a controller. The controller includes: the device comprises a voltage operation module, a current operation module and a constant voltage and constant current module.

The voltage operation module is used for acquiring the voltage V of the clamping capacitor at the beginning of the zero-voltage conduction phase of the fourth main switch after the energy transmission phase_clampCalculating the output voltage value V_O，

Wherein, V_f2、V_f3、V_f5Respectively the conduction voltage drop of the second main switch tube, the clamping switch tube and the synchronous rectifier tube, N_PSIs the equivalent turn ratio of the primary and secondary windings of the transformer.

Sampling input voltage in energy input stage to obtain primary side input voltage value V_IN(ii) a Sampling the primary current at the end of the energy input stage to obtain the maximum value I of the primary inductive current_max(ii) a Sampling the primary current at the clamping stage to obtain the minimum value I of the primary inductive current_min(ii) a The fourth main switching tube is subjected to current sampling at the zero voltage conduction stage of the clamping switching tube to obtain the charging current I passing through the fourth main switching tube at the stage_ZVSAAccording to the current theorem of the Kilofski and the conservation of energy, the output current value I_OThe approximation is:

wherein, t_dead1、T_SThe zero voltage conduction stage and the duration time of the whole working cycle of the clamping switch tube are respectively obtained by a timer; c_OSS3Is a source-drain end parasitic capacitance of the clamping switch tube; l is_m、L_rThe equivalent excitation inductance and the equivalent leakage inductance of the primary winding of the transformer are respectively.

The first, second and fourth main switch tubes are directly controlled by the gate drive receiving the instruction of the controller, the synchronous rectification switch tube is controlled by the secondary synchronous rectification control circuit, and the clamping switch tube is controlled by the controller, the auxiliary winding for processing the gate signal of the synchronous rectification tube and the logic circuit.

The switching state of the synchronous rectifier tube, namely the grid signal, is fed back to the primary side through the auxiliary winding. Under the steady state work, the switching state of the clamping switch tube is consistent with that of the synchronous rectifier tube, so that the grid signal of the synchronous rectifier tube fed back to the primary side can be connected with the logic circuit to generate the grid signal of the clamping switch tube. If the gate signal of the clamping switch tube is completely determined by the synchronous rectifier tube and is consistent with the synchronous rectifier tube, under some special working conditions (such as hot plug condition), the phenomenon that the clamping switch tube and the fourth main switch tube are conducted simultaneously and the clamping capacitor is short-circuited can occur when the synchronous rectifier tube is switched on by mistake in a stage (such as an energy input stage) which is not switched on, and the circuit is damaged. Therefore, the gate signal of the clamp switch is also determined according to the control enable signal of the clamp switch output by the controller, so that the clamp switch is not conducted in the non-clamping stage. The auxiliary winding includes: the primary side loop, the Zener diode and the capacitor which are connected in parallel at two ends of the primary side loop form a primary side loop, and the primary side loop outputs grid signals of the synchronous rectifier tube which are refracted to the primary side after voltage stabilization. The logic circuit includes: the D latch outputs the feedback signal of the synchronous rectifier tube after latching the output voltage of the primary side loop, and the AND gate carries out logic operation on the feedback signal of the synchronous rectifier tube and the control enabling signal of the clamping switch tube. The addition of a D-latch between the auxiliary winding and the and gate allows the auxiliary winding to be made smaller by only having to pass positive or negative pulses, and not having to pass positive or negative signals continuously.

When the converter works in an energy input stage, a fourth main switching tube zero voltage conduction stage, a clamping stage and a first main switching tube zero voltage conduction stage, the clamping switching tube controls an enabling signal to be negative; when the converter works in the zero voltage conduction stage and the energy transmission stage of the clamping switch tube, the clamping switch tube controls the enabling signal to be positive. The clamping switch tube and the synchronous rectifier tube are ensured to be synchronously started through the processing of the logic circuit and are not mistakenly started in the non-working stage.

And comparing the voltage value or the current value with a preset voltage output value or a preset current output value, and adjusting the time length of the energy input stage to adjust the voltage value or the current value output by the converter. In the constant-voltage (constant-current) mode, the constant-voltage and constant-current control module calculates I_OAnd V_OReference voltage value V_ref(reference Current value I_ref) And the output voltage value V_O(output Current value I_O) Subtracting to obtain a voltage output error E_V(Current output error E_I) Error of voltage output E_V(Current output error E_I) Then obtaining a current threshold I through a differentiator and a PI compensator_th. In the energy input phase, the primary current I_PLinearly rising as primary current I_PRising to current threshold I_thAnd when the energy input stage is controlled to be finished, the constant-voltage constant-current function can be realized.

Meanwhile, under the common working condition of the converter, the duration of the clamping stage is used for keeping the working period unchanged and is the minimum working period, namely the minimum working period corresponds to the highest switching frequency. Under the condition of low-voltage input and large-current output, the switching frequency can be reduced by setting the minimum duration of the clamping stage and setting the working period to be greater than the minimum working period, so that higher efficiency can be realized under various input and output condition combinations.

By adopting the technical scheme, the invention has the following beneficial effects:

(1) the primary side regulation control scheme provided by the application aims at the double-clamping ZVSBuck-Boost converter, ZVS (zero voltage switching) opening of a switching tube is realized on the premise of not changing the working state of the converter by using a simpler sampling circuit and a clamping switching tube grid signal control circuit, synchronous opening of a synchronous rectifier tube and the clamping switching tube is ensured, and mistaken opening of the synchronous rectifier tube is prevented, accurate primary side predicted values of output voltage and output current of the double-clamping ZVS buck-Boost converter can be obtained, a primary side regulation constant voltage and constant current control function is realized, the use of an optical coupler or other isolation devices is reduced, the power density of a system is further improved, and the size is reduced.

(2) According to the method and the device, the duration of the clamping stage is selected and the minimum clamping duration is set, so that the frequency conversion control is realized, the efficiency is improved, the working state of opening of the primary side power tube and the secondary side rectifier tube ZVS is ensured while the high output voltage precision and the output current precision are realized, and the higher working efficiency is obtained.

(3) The method and the device can adaptively adjust the internal parameter values, such as the switching period, according to the working state of the system, so that better dynamic characteristics and steady-state characteristics are obtained.

Drawings

FIG. 1 is a circuit topology diagram of a dual-clamped ZVS Buck-Boost converter.

Fig. 2 is a waveform diagram of gate signals of each switching tube in one working cycle.

Fig. 3 is a circuit topology diagram of a primary side regulation control system of a double-clamp ZVS Buck-Boost converter in the first embodiment of the present application.

FIG. 4 shows an auxiliary winding side clamp switch gate signal G₃A circuit diagram of a controller.

FIG. 5 shows a feedback signal G of a synchronous rectifier_5FBThe clamp switch tube controls the enable signal G_3FBGate signal G of clamp switch₃A waveform diagram of (a).

FIG. 6 is an equivalent circuit diagram of the ZVS A phase.

Fig. 7 is a schematic diagram of the control logic of the constant voltage and constant current module in the first embodiment of the present application.

Fig. 8 is a waveform diagram of the primary side inductor current in the first embodiment of the present application.

Fig. 9 is a circuit topology diagram of a primary side regulation control system of a double-clamp ZVS Buck-Boost converter in a second embodiment of the present application.

Fig. 10 is a schematic diagram of the control logic of the constant voltage and constant current module in the second embodiment of the present application.

Fig. 11 is a circuit topology diagram of Vicor corporation for a primary side sampling control scheme for a dual-clamp ZVS Buck-Boost converter.

The reference numbers in the figures illustrate: t is₁Is a main transformer, L_rIs the equivalent leakage inductance of the primary winding of the main transformer, L_mEquivalent excitation inductance, Q, of primary winding of main transformer₁、Q₂And Q₄Is a first, a second and a fourth main switch tube Q₃For clamping the switching tube, C_clampAs a clamping capacitor, Q₅Being a synchronous rectifier tube, C_outIs the output capacitance.

Detailed Description

The technical scheme of the invention is explained in detail in the following with reference to the attached drawings.

The circuit topology of the double-clamp ZVS Buck-Boost converter is shown in FIG. 1, and comprises a main transformer T₁And a main transformer T₁First main switch tube Q with primary side winding forming H-type full bridge₁A second main switch tube Q₂Clamping switch tube Q₃And a fourth main switching tube Q₄First main switch tube Q₁And a second main switch tube Q₂A bridge arm formed by serial connection is connected in parallel at two ends of a direct current input power supply, and a clamping switch tube Q₃And a fourth main switch tube Q₄Another bridge arm formed by series connection is connected in parallel with the clamping capacitor C_clampBetween two stages, the primary winding of main transformer is connected between the middle points of two bridge arms, and synchronous rectifier tube Q₅An output capacitor C_outAnd the secondary winding of the main transformer is connected in series to form a secondary loop.

The present application proposes a primary side regulation control system as shown in fig. 3 for a dual-clamp ZVS Buck-Boost converter as shown in fig. 1, the primary side regulation control system comprising: the device comprises an inductive current detection module, a source-drain voltage detection module, a clamping voltage detection module, an input voltage detection module, a secondary side synchronous rectification circuit, an auxiliary winding and logic circuit, a timer, a gate driver and a controller. The controller includes: the device comprises a voltage operation module, a current operation module and a constant voltage and constant current module.

As shown in fig. 4, the auxiliary winding includes: a secondary coil connected in series between the secondary synchronous rectification control circuit and the secondary side ground, and a primary coil, wherein the primary coil, a Zener diode and a capacitor connected in parallel at two ends of the primary coil form a primary loop, and the primary loop refracts a synchronous rectification tube grid signal G to the primary side₅And (5) outputting after voltage stabilization. The logic circuit includes: latch primary side loop output voltage and then output synchronous rectifier tube feedback signal G_5FBD latch of (1), and, feeding back signal G to synchronous rectifier_5FBAnd a clamp switch tube control enable signal G_3FBAND gate for logic operation, and gate output clamping switch tube grid signal G₃. Feedback signal G of synchronous rectifier tube_5FBThe clamp switch tube controls the enable signal G_3FBGate signal G of clamp switch₃The waveform of (c) is shown in fig. 5.

The inductive current detection module acquires the output current I of the fourth main switching tube at each stage_PThe source-drain voltage detection module collects the drain-source voltage V of each switch tube on the H bridge_DS1、V_DS2、V_DS3、V_DS4The clamping voltage detection module acquires the voltage V of the clamping capacitor at the initial zero-voltage conduction moment of the fourth main switching tube_clampThe input voltage detection module samples the primary input voltage V of the energy input stage_IN。

The voltage operation module is used for conducting the voltage V of the clamping capacitor at the initial moment according to the zero voltage of the fourth main switching tube_clampCalculating converter output voltage V_O. The current operation module outputs current I according to the ending moment of the fourth main switch tube in the energy input stage, the clamping stage and the zero voltage conduction stage of the clamping switch tube_max、I_min、I_ZVSAZero voltage conduction phase and whole working cycle of clamping switch tubeDuration t of time_dead1、T_SPrimary side input voltage V of energy input stage_INCalculating the converter output current I_OAnd the constant voltage and constant current module calculates a current threshold according to the output voltage error of the converter or the output current error of the converter. Output current I of the fourth main switch tube_PWhen the voltage rises to the threshold value, the first main switching tube and the fourth main switching tube are turned off, and the energy input stage is ended; when the drain-source voltage of the second main switch tube and the clamping switch tube is reduced to 0 and the synchronous rectifier tube feedback signal is positive, the second main switch tube and the clamping switch tube are conducted, and the clamping switch tube control enabling signal changed from negative to positive is generated according to the synchronous rectifier tube feedback signal output by the logic circuit; output current I of the fourth main switch tube_PWhen the leakage current is reduced and the feedback signal of the synchronous rectifier tube is negative, the clamping switch tube and the synchronous rectifier tube are turned off, and the energy transmission stage is ended; when the drain-source voltage of the fourth main switching tube is reduced to 0, the fourth main switching tube is conducted; determining the end time of the clamping stage according to the difference value between the minimum working period and the actual working period and the minimum value in the shortest duration time of the clamping stage, and turning off the second main switching tube when the end time of the clamping stage arrives; when the drain-source voltage of the first main switch tube is reduced to 0 or the output current I of the fourth main switch tube_PWhen the voltage rises to 0, the first main switch tube is conducted.

A complete working cycle of the double-clamping ZVS Buck-Boost topology is divided into the following six stages, wherein grid signals are t in the figure 2₀-t₆As shown.

1. Energy input phase t₀-t₁

At t₀At time, the fourth main switch tube Q₄The first main switch tube Q is kept conductive from the last stage of the last working period of the converter₁Starting to conduct, the second main switch tube Q₂Clamping switch tube Q₃Synchronous rectifier tube Q₅Remains off, thereby initiating the energy input phase. In the energy input stage, the source V is input_INCharging the primary winding of a transformer with a primary current I_PLinearly increasing (the direction of the arrow in fig. 1 is the positive direction). At t₁First main switch is switched off at any momentClosing tube Q₁And the fourth main switch tube Q₄The energy input phase ends.

ZVS A phase t₁-t₂

At t₁At any moment, the first main switch tube Q₁And the fourth main switch tube Q₄Turn off and switch the second main switching tube Q₂Clamping switch tube Q₃Synchronous rectifier tube Q₅Remain off and begin ZVS a phase. In ZVS A stage, current I in primary winding_PUnder the action of (1), the second main switch tube Q₂Clamping switch tube Q₃The parasitic capacitance of the source and drain ends and the primary winding inductance are discharged in a resonant mode, and a first main switching tube Q₁And the fourth main switch tube Q₄The parasitic capacitance of the source and drain terminals and the primary winding inductance are charged in a resonant mode, so that the second main switching tube Q is charged₂Clamping switch tube Q₃Ready for ZVS turn on. t is t₂At the moment, the second main switch tube Q₂Clamping switch tube Q₃The voltage of the source and drain electrodes is reduced to zero, and a second main switch tube Q₂Clamping switch tube Q₃Turn on begins and ZVS a phase ends.

3. Energy transfer phase t₂-t₃

At t₂At the moment, the second main switch tube Q₂Clamping switch tube Q₃Synchronous rectifier tube Q₅Starts to conduct and the first main switch tube Q₁And the fourth main switch tube Q₄Remains off and begins the energy transfer phase. Equivalent excitation inductance L stored in primary winding_mThe energy in (3) is transferred to the secondary side, and the exciting inductance current is linearly reduced. Equivalent leakage inductance L of primary winding at the same time_rAnd a clamp capacitor C_clampAnd (3) resonance, wherein energy stored in the leakage inductance circulates on the primary side, and the leakage inductance current is in damped oscillation due to the conduction resistance of the conducted MOS tube. At t₃At the moment, the exciting inductance current is reduced to be equal to the leakage inductance current, and the energy transmission stage is finished.

ZVS B phase t₃-t₄

At t₃Time of day, clamp switch Q₃Synchronous rectifier tube Q₅Begin to shut downBreaking, the first main switch tube Q₁And the fourth main switch tube Q₄Keep off, the second main switch tube Q₂Remains on and begins the ZVS B phase. In the ZVS B stage, the exciting inductance current and the leakage inductance current are equal and are equal to the primary side current. At t₃At that moment, the primary current is substantially equal to zero. In the ZVS B stage process, the parasitic capacitance at the source and drain ends of the clamping switch tube Q3 is charged with the primary winding in a resonant mode, and the fourth main switch tube Q₄The parasitic capacitance at the source and drain ends and the primary winding are discharged in a resonant mode, and the primary current is increased in a negative direction. t is t₄At time, the fourth main switch tube Q₄The voltage of the source and drain electrodes is reduced to be near zero, and a fourth main switch tube Q₄On and ZVS B phase ends.

5. Clamping phases t4-t5

At t₄At time, the fourth main switch tube Q₄Starting to conduct, the first main switch tube Q₁Clamping switch tube Q₃Synchronous rectifier tube Q₅Keep off, the second main switch tube Q₂Remains on and begins the clamping phase. In the clamping phase, the second main switch tube Q₂And a fourth main switching tube Q₄A short circuit is formed at two ends of a primary winding of the transformer, the voltage at two ends of the primary winding is clamped to zero volt, and a primary negative current is kept unchanged. At t₅At the moment, the second main switch tube Q₂And turning off and finishing the clamping phase. The purpose of the clamping phase is to maintain a negative current in the primary winding to help realize the first main switching tube Q₁ZVS of on.

ZVS C-stage t5-t6

At t₅At the moment, the second main switch tube Q₂Turn-off, first main switch tube Q₁Clamping switch tube Q₃Synchronous rectifier tube Q₅Keep off, fourth main switch tube Q₄Remains on and begins the ZVS C phase. In the ZVS C stage, under the action of the primary side negative current, the first main switching tube Q₁The parasitic capacitance of the source and drain ends is discharged with the primary winding in a resonant way, and a second main switch tube Q₂The parasitic capacitance of the source and drain terminals is charged with the primary winding in a resonant manner, thereby providing a first main switch tube Q₁In preparation for ZVS turn on, the absolute value of the primary side negative current decreases. t is t₆At any moment, the first main switch tube Q₁The voltage of the source and drain electrodes is reduced to near zero, and a first main switch tube Q₁On, ZVS C phase ends. One duty cycle ends.

The technical scheme of the invention is further explained in detail by combining the attached drawings:

the first embodiment of the control system operates as shown in fig. 3. In one working cycle, the control system needs to sample voltage at A, B, C, D, E5 points at different times and perform G operation₅Feedback signal G_5FBSampling, in which the inductor current I_PSampling the voltage V from point E_ESampling composition

R_SIs a sampling resistor; source-drain voltage (V) of MOS tube at primary side_DS1、V_DS2、V_DS3、V_DS4) The voltage (V) at point A, B, C, D, E is sampled_A、V_B、V_C、V_D、V_E) Composition of samples, V_DS1＝V_A-V_B，V_DS2＝V_B，V_DS3＝V_C-V_D，V_DS4＝V_D-V_E(ii) a Voltage V of clamping capacitor_clmapSampling the voltage V from point C_CComposition of samples, V_clamp＝V_C(ii) a Input voltage V_INSampling voltage V from point A_AComposition of samples, V_IN＝V_A. The timer works continuously, records the duration of each stage and inputs the duration into the controller. The control and regulation method of each stage is as follows:

1. energy input phase t₀-t₁

t₀Before the moment, the fourth main switch tube Q₄In a conducting state, the first main switch tube Q₁A second main switch tube Q₂Clamping switch tube Q₃Synchronous rectifier tube Q₅Off, G₃Control enable signal G_3ENIs negative. From t₀At any moment, the control system switches on the first main switch tube Q₁And keeps the fourth main switch tube Q₄Conducting and simultaneously starting to detect the voltage V at the point A_AVoltage V at point E_ECalculating an input voltage value V_INAnd primary side inductance current I_PTo obtain V_IN＝V_A，

When primary side current I_PRises to I_thTime-off first main switch tube Q₁And the fourth main switch tube Q₄Switching to ZVS A stage to detect that the detected signal is greater than I_thThe maximum value of the inductance current is marked as I_max。I_thThe value of the voltage is an output voltage value V obtained by the constant voltage and constant current module according to the primary side sampling_OAnd an output current value I_OIs calculated to obtain_thIs a set reference voltage V_ref(or reference current I_ref) And the calculated output voltage V_O(or output current I_O) And the voltage error E obtained by subtraction_V(Current error E)_I) The current threshold I is obtained by a differentiator and a PI compensator_th1(I_th2) As shown in fig. 7.

ZVS A phase t₁-t₂

From t₁At any moment, the control system turns off the first main switch tube Q₁And the fourth main switch tube Q₄Output G₃Control enable signal G_3ENIs positive, and starts to detect the voltage V at the point B_BVoltage V at point C_CVoltage V at point D_DVoltage V at point E_EAnd G₅Feedback signal G_5FBCalculating the second main switch tube Q₂Clamping switch tube Q₃Voltage V of source-drain terminal_DS2＝V_B，V_DS3＝V_C-V_DAnd ZVS A stage is performed through a fourth main switching tube Q₄Current of

In ZVS A stage, the equivalent model of the circuit is shown in FIG. 6, the first main switch tube Q₁A second main switch tube Q₂Clamping switch tube Q₃And the fourth main switch tube Q₄Tube cut-off, synchronous rectifier tube Q₅The tube is also shut off. First main switch tube Q₁And the fourth main switch tube Q₄The parasitic capacitance of the source and drain ends is charged in a resonant mode, and a second main switch tube Q₂Clamping switch tube Q₃The parasitic capacitance at the source and drain ends of the tube discharges in resonance, I in FIG. 6₁，I₂，I₃，I₄And I_PAre both greater than zero. Because the value of the parasitic capacitance is small, the source-drain voltage of the MOS tube is approximately linearly changed, the current passing through the four MOS tubes is approximately constant, and the current I input into the converter from the input source_charge(i.e. I)₁) And is also substantially a constant value. From the Kill Howski current law at points B and D, I₁+I₂＝I_P＝I₃+I₄Since the first main switch tube Q1 and the second main switch tube Q2 use the same switch tube, the parasitic capacitances of the two tubes are equal, and at this time, the first main switch tube Q passes through₁A second main switch tube Q₂Current of equal magnitude in the tube I₁＝I₂Then there is I_charge＝I₁＝(I₃+I₄) [ 2 ] I in the formula₄＝I_ZVSA. Because of the clamping switch tube Q₃The source-drain voltage drops approximately linearly and does not consider the fluctuation of the clamping voltage in the period, at t₁Time clamping switch tube Q₃Source drain voltage is approximately N_PS×V_OAt t₂Time clamping switch tube Q₃The source-drain voltage is approximately 0, then at t₁-t₂Clamping switch tube Q within time₃Approximate linear voltage drop N between two ends of parasitic capacitor at source and drain ends_PS×V_OThen, then

Wherein, C_OSS3Is the parasitic capacitance, t, of the source and drain of the clamping switch tube Q3_dead1＝t₂-t₁I.e., the duration of the ZVS a phase. The current operation module can calculate the magnitude of the charging current input from the input source to the converter in the ZVS a stage:

in the ZVS a phase, the energy input to the converter from the input source:

calculating the input current I of the input source to the converter in the ZVS A stage_chargeWhen it is, the first main switch tube Q is considered₁A second main switch tube Q₂The parasitic capacitances of the two transistors are equal by using the same switch tube, so that the current passing through the first main switch tube Q1 and the second main switch tube Q2 is equal in magnitude I₁＝I₂But calculating I alone₃And I₄The reason for this is that in practical use, the fourth main switch tube Q can be used₄The source-drain terminal is connected with a small capacitor in parallel to store more energy, so that the first main switch tube Q is realized₁ZVS of is turned on so that there is I₃≠I₄。

When the second main switch tube Q₂Clamping switch tube Q₃Is reduced to substantially zero and G₅When the feedback signal becomes positive, the controller conducts the second main switch tube Q₂. When G is₅The feedback signal becomes positive, and the tube Q is synchronously arranged₅And a clamping switch tube Q₃In synchronous rectification controller and auxiliary winding and G₃The signal controller is also started, the ZVS A phase is ended, and the converter is switched to the energy transmission phase.

3. Energy transfer phase t₂-t₃

From t₂At that moment, the control system turns on the second main switch Q₂And continue to detect G₅Feedback signal G_5FB. When G is₅Feedback signal G_5FBWhen it becomes negative, the synchronous rectifier Q is illustrated₅And a clamping switch tube Q₃In synchronous rectification controller and auxiliary winding and G₃The converter is switched to the ZVS B stage when the converter is switched off under the action of the signal controller.

In the energy transfer phase, the clamping capacitor C_clampEquivalent leakage inductance L with primary winding_rResonance, resonance period

Considering the on-resistance of the MOS tube, the equivalent leakage inductance current I of the primary winding_rShowing damped oscillation, as shown in fig. 8; equivalent excitation inductance L of primary winding_mEnergy is transmitted to the secondary side, and the equivalent exciting inductive current I of the primary side winding_mThe linearity decreases. In the energy transfer phase, the clamping capacitor C_clampAnd an output capacitor C_outDirectly through the transformer. At the end of the energy transfer phase, the leakage-induced current I_rDamped oscillation amplitude close to zero, voltage V at point C_C(i.e. clamp capacitor voltage V)_clamp) Is substantially equal to N_PS×V_OWherein N is_PSIs the turn ratio of primary and secondary windings, V_OFor secondary side output voltage, consider the second main switch tube Q at this time₂Clamping switch tube Q₃Synchronous rectifier tube Q₅The conduction voltage drop of (a), namely:

wherein, V_f2、V_f3、V_f5Respectively a second main switch tube Q₂Clamping switch tube Q₃Synchronous rectifier tube Q₅Conduction voltage drop of, N_PSThe equivalent turn ratio of the primary winding and the secondary winding of the transformer is obtained. Therefore, the voltage output value of the secondary side can be estimated by sampling the voltage at the point C immediately after the energy transmission stage.

ZVS B phase t₃-t₄

From t₃At that time, the control system switches to the ZVS B phase. Controller output G₃Control enable signal G_3ENIs negative, and immediately detects the voltage at point C in a short time (10-20ns), continuously detects the voltage at point D, E, and calculates the clamping voltage value V_clamp＝V_CAnd a fourth main switching tube Q₄Voltage V of source-drain terminal_DS4＝V_D-V_E。t₃The reason why the clamp voltage is detected immediately in a short time is thatIn ZVS B stage, the switching tube Q is clamped₃The fourth main switch tube Q₄The parasitic capacitance of the source and the drain ends is discharged in a resonant mode, and the switching tube Q is clamped₃The resonant charging current causes the clamp capacitor voltage to drop. If the clamp voltage is sampled too late or too long, the calculated output voltage will be low, resulting in a high actual output voltage. When the fourth main switch tube Q₄Voltage V of source-drain terminal_DS4When the voltage drops to about zero, the controller conducts the fourth main switch tube Q₄Switching to the clamping phase.

5. Clamping phases t4-t5

At t₄At the moment, the control system records t of the last work cycle recorded by the timer₅-t₆T of the duty cycle₀-t₄Add to obtain T_otherAs shown in fig. 2. Assuming that the minimum duty cycle corresponding to the highest operating frequency is T_SminThe minimum duration of the clamping phase is t_clampminThe duration of the clamping phase should be T_Smin-T_otherAnd t_clampminThen turn off Q₂Switching to ZVS C phase. In this way, variable frequency control of the converter can be achieved. Under most common working conditions, the duration of the clamping stage is used for keeping the working period unchanged and is the minimum working period T_SminI.e. corresponding to the highest switching frequency, when the duration of the clamping phase is T_Smin-T_other. In the case of low-voltage input and large-current output, the minimum duration t of the clamping stage is set_clampminSuch that the duty cycle is greater than the minimum duty cycle.

Under the condition of high-voltage input and low-current output, the proportion of the time of the clamping stage in the whole working period is high and can even exceed 50%, the highest working frequency of the converter is limited in this way, and the conduction loss of the clamping stage is smaller than the switching loss caused by high switching frequency due to the fact that the negative current of the clamping stage is smaller. Under the condition of low-voltage input and large-current output, the lower the input voltage is, the higher the output power is, and the lower the switching frequency of the converter is, so that the ZVS (zero voltage switching) starting of a switching tube can still be realized by the converter through frequency reduction. Therefore, the converter can realize higher efficiency under various input and output condition combinations.

During the duration of the clamping phase, the magnitude of the negative current on the primary side is substantially constant and maintained at a minimum. Sampling E point voltage V_ECalculating the magnitude of the negative current on the primary side, and recording as

At t₁-t₃And in the stage, considering the total energy conservation of the converter, the magnitude of the energy stored in the parasitic capacitor of the MOS tube is far smaller than the energy of the inductor and the energy transmitted to the secondary side, so that the energy can be ignored, and meanwhile, the voltage of the primary side clamping capacitor is basically unchanged and can not participate in discussion. At t₁-t₂Stage, the input source inputs energy to the primary side as P_ZVSAAt t₂-t₃Stage, the energy transmitted from the primary side to the secondary side is the output energy T of the secondary side in the whole working period_S×V_O×I_OAnd t is₁Primary side energy at the moment of time is

the primary side energy at the time t3 is

Thus t₃Time t and₁the difference of the primary energy at time t₁-t₃The difference between the energy input to the primary side and the energy output from the primary side in stages is as follows:

substituting:

the output current I is obtained by trimming_OSize:

ZVS C phase t₅-t₆

From t₅At any moment, the control system turns off the second main switch tube Q₂Starting to detect A, B, E three-point voltage and calculating the first main switch tube Q₁Voltage V of source-drain terminal_DS1＝V_A-V_BAnd primary side inductance current

In ZVS C stage, the second main switch tube Q₂The parasitic capacitance of the source and drain ends is charged in a resonant mode, and a first main switch tube Q₁The parasitic capacitance at the source and drain ends is discharged in a resonant mode, the negative current of the primary side inductor is increased, and the absolute value is reduced. When the first main switch tube Q₁Source-drain terminal voltage V_DS1Reduced to near zero or primary side inductor current I_PWhen the rising is zero, the controller conducts the first main switch tube Q₁And when one working cycle is ended, switching to the next working cycle. The timer adds the total time length of the six stages to obtain the working period T of the converter_S。

If the triggering condition of the switching is the first main switch tube Q₁Source-drain terminal voltage V_DS1When the voltage drops to near zero, the first main switch tube Q₁Full ZVS can be achieved; if primary side inductor current I is switched_PRising to zero indicates that the first main switch tube Q is at that time₁Source-drain terminal voltage V_DS1Greater than zero, but only when the primary inductor current I_PWhen the voltage is less than zero, the first main switch tube Q can be supplied₁The parasitic capacitor is discharged, and the first main switch tube Q is at the moment₁Only partial ZVS can be implemented. As mentioned above, the fourth main switch tube Q may be arranged₄The source-drain terminal is connected with a small capacitor in parallel to store more energy, so that the first main switch tube Q is realized₁ZVS of on.

In a first embodiment, the duration t of the energy input phase₀-t₁Duration t of ZVS A phase₁-t₂Duration t of energy transfer phase₂-t₃Duration t of ZVS B phase₃-t₄Duration t of the clamping phase₄-t₅Duration t of ZVS C phase₅-t₆All calculated by a constant voltage and constant current module. The arithmetic logic is shown in fig. 7.

The controller of the first embodiment specifically operates as follows:

step A-1 at t₀Constantly conducting first main switch tube Q₁Keeping the fourth main switch tube Q₄Conducting and maintaining the second main switch tube Q₂Off, hold G₃Control enable signal G_3ENTo be negative, the voltage V at the point A is detected_AAnd voltage V at point E_ECalculating the input voltage V_IN＝V_APrimary side of the inductive current

When primary side inductance current I_PGreater than the current threshold I calculated by the controller_thWhen, the time is recorded as t₁At this time, the primary side inductance current I_PIs I_maxAnd turn off the first main switch tube Q₁And the fourth main switch tube Q₄Output G₃Control enable signal G_3ENIs positive.

Step A-2, at t₁The voltage V at the point B is detected at the beginning of time_BVoltage V at point C_CVoltage V at point D_DVoltage V at point E_EAnd G₅Feedback signal G_5FBCalculating the second main switch tube Q₂And the third main switch tube Q₃Voltage V of source-drain terminal_DS2＝V_B，V_DS3＝V_C-V_DAnd ZVS A stage is performed through a fourth main switching tube Q₄Current of

When V is_DS2And V_DS3Down to near zero and G₅Feedback signal G_5FBIf positive, the time is recorded as t₂And turn on the second main switch tube Q₂. Note t_dead1＝t₂-t₁。

Step A-3, at t₂Time of day start detection G₅FeedbackSignal G_5FBWhen G is₅Feedback signal G_5FBWhen the current is negative, the current time is recorded as t₃And output G₃Control enable signal G_3ENIs negative.

Step A-4, at t₃Immediately detecting the voltage at point C in a short time, continuously detecting D, E the voltage at two points, and calculating the clamping voltage value V_clamp＝V_CAnd a fourth main switching tube Q₄Voltage V of source-drain terminal_DS4＝V_D-V_E. Calculating secondary side output voltage:

wherein, V_f2、V_f3、V_f5Respectively a second main switch tube Q₂Clamping switch tube Q₃Synchronous rectifier tube Q₅Conduction voltage drop of, N_PSIs the equivalent turn ratio, V, of the primary and secondary windings of the transformer_f2、V_f3、V_f5、N_PSAre constants set within the controller. When the fourth main switch tube Q₄Voltage V of source-drain terminal_DS4When the current drops to zero, the time is recorded as t₄And turn on Q₄。

Step A-5, at t₄Voltage V at point E at the beginning of time_ECalculating the minimum value of the primary current as

Calculating the output current value I_O：

Wherein, C_OSS3Is a clamping switch tube Q₃The source-drain end parasitic capacitance; l is_m、L_rRespectively an equivalent excitation inductance and an equivalent leakage inductance of a primary winding of the transformer, C_OSS3、L_m、L_rAre constants set within the controller. T is_SIs the total switching period of the converter,obtained by a timer.

In constant voltage mode, a reference voltage V to be set_refAnd the calculated output voltage V_OAnd the voltage error E obtained by subtraction_V＝V_ref-V_OError in voltage E_VObtaining a current threshold I through a differentiator and a PI compensator_th1。

In constant current mode, a reference current I to be set_refAnd the calculated output current I_OAnd the current error I obtained by subtraction_V＝I_ref-I_OError in current I_VObtaining a current threshold I through a differentiator and a PI compensator_th2。

The timer will count the working period t₀To t₄Plus t of the last duty cycle₅To t₆Time, get T_otherComparison of T_Smin-T_otherAnd t_clampminTaking the larger value of the two as the clamping stage time T_SminAnd t_clampminThe minimum duty cycle and the minimum clamping duration, respectively, of the converter are constants that are set in the controller. After the clamp phase time continuously obtained from t4, let t be the time₅And turn off the second main switch tube Q₂。

Step A-6, at t₅A, B, E three-point voltage is detected at the beginning of time, and the first main switching tube Q is calculated₁Voltage V of source-drain terminal_DS1＝V_A-V_BAnd primary side inductance current

When the first main switch tube Q₁Voltage V of source-drain terminal_DS1Down to zero or primary side inductor current I_PWhen the voltage rises to zero, the time is recorded as t₆And turn on the first main switch tube Q₁. Calculating the total switching period T of the converter_S＝t₆-t₀And when one switching period is finished, the step A-1 is executed again.

The second embodiment of the control system operates as shown in fig. 9. In one working period, the control system is notAt the same time, A, C, E3 points need to be subjected to voltage sampling and G₅Feedback signal G_5FBSampling, in which the inductor current I_PSampling the voltage V from point E_ESampling composition

R_SIs a sampling resistor; voltage V of clamping capacitor_clmapSampling the voltage V from point C_CComposition of samples, V_clamp＝V_C(ii) a Input voltage V_INSampling voltage V from point A_AComposition of samples, V_IN＝V_A. The timer works continuously, records the duration of each stage and inputs the duration into the controller.

The method of the second embodiment is similar to that of the first embodiment, and the greatest difference is that the source-drain voltage sampling module of the first embodiment is omitted, and only A, C, E three points are subjected to voltage sampling. The duration time of the ZVS A stage, the ZVS B stage and the ZVS C stage is not judged by the source-drain voltage of the MOS tube any more, but the time of each ZVS stage is determined in a mode of calculation and lookup table.

The control and regulation method for each stage is explained in detail below:

1. energy input phase t₀-t₁

In the constant voltage (constant current) mode, the reference voltage value V is set, similarly to the first embodiment_ref(Current I)_ref) And the output voltage value V_O(output Current value I_O) Subtracting to obtain the output voltage error E_V(error in output Current E_I) Error of output voltage E_V(error in output Current E_I) Then obtaining a current threshold I through a differentiator and a PI compensator_th1(I_th2). In the energy input phase, the primary current I_PAnd (4) increasing linearly. When primary side current I_PRising to current threshold I_th1(I_th2) And the energy input stage is ended, and the ZVS A stage is switched to.

ZVS A phase t₁-t₂

Unlike the first embodiment, the minimum duration of the ZVS A phase is calculated to be offIn I_charge、V_INAs a function of (c). Minimum duration of ZVS A phase by second main switch tube Q₂The discharge time of the source-drain parasitic capacitance is determined. Because in the ZVS A stage, the second main switch tube Q₂The parasitic capacitance of the source and the drain is approximately linearly discharged, and the discharge time is recorded as the minimum duration t of the ZVS A stage_ZVSAmin：

The converter lasts for t in ZVS A phase_ZVSAminTime and detect G₅Feedback signal G_5FBTo switch to the energy transfer phase right after.

3. Energy transfer phase t₂-t₃

Similar to the first embodiment, the duration of the energy transfer phase is given by G₅Feedback signal G_5FBDetermine when G is₅Feedback signal G_5FBWhen the voltage becomes negative (namely the secondary side synchronous rectifier is turned off), the circuit is switched to a ZVS B stage.

ZVS B phase t₃-t₄

Unlike the first embodiment, the duration of the ZVS B phase is set by V_OThe duration of ZVS B phase is determined by table lookup as to V_OThe piecewise function of (2). The duration of ZVS B phase is controlled by the fourth main switch tube Q₄The discharge time of the source-drain parasitic capacitance is determined. Under the condition that the circuit parameters are fixed, the fourth main switching tube Q₄A fourth main switching tube Q when the discharge time of the source-drain parasitic capacitance starts from the ZVS B stage₄Source to drain voltage, i.e. V_O×N_PSDetermine so that the fourth main switch tube Q₄Is a discharge time of V_OAs a function of (c). Due to the influence of parasitic parameters, the formula derived from the equivalent model is inaccurate. Thus, the information about V can be utilized_OTo determine the duration of the ZVS B-phase. V within a certain range_OIn the output case, the duration of the ZVS B phase is fixed, and the switching to the clamping phase is performed after the duration of the fixed time.

5. Clamping phase t₄-t₅

Similar to the first embodiment, the control system adds the time recorded by the timer from the beginning of the ZVS C phase of the previous duty cycle to the end of the ZVS B phase of the duty cycle to obtain T_other. Assuming that the minimum duty cycle corresponding to the highest operating frequency is T_SminThe minimum duration of the clamping phase is t_clampminThe duration of the clamping phase should be T_Smin-T_otherAnd t_clampminThen switches to ZVS C phase.

ZVS C phase t₅-t₆

Unlike the first embodiment, the maximum duration of the ZVS C phase is determined by the primary negative current value I of the clamp phase_minAnd (4) determining the inductance current value obtained by looking up a table and calculating the voltage of the E point collected at the moment. The duration of the ZVSC phase is determined by the primary negative current value I of the clamping phase_minTo Q₂The charging time of the source-drain parasitic capacitance of the tube is determined. Second main switch tube Q₂The charging time of the source-drain parasitic capacitance is I_minAs a function of (c). Also, I_minMay be used to determine the maximum duration of ZVS phase C. In a fixed location I_minIn the case, the maximum duration of the ZVS C phase is fixed at the inductor current value I_PRising to the vicinity of zero or lasting for a maximum fixed time and then switching to the energy input phase of the next cycle.

In a second embodiment, the duration t of the energy input phase₀-t₁Duration t of ZVS A phase₁-t₂Duration t of energy transfer phase₂-t₃Duration t of ZVS B phase₃-t₄Duration t of the clamping phase₄-t₅Duration t of ZVS C phase₅-t₆All calculated by a constant voltage and constant current module. The arithmetic logic is shown in fig. 10.

The specific operation steps of the controller of the second embodiment are as follows:

step B-1, at t₀Constantly conducting first main switch tube Q₁Keeping the fourth main switch tube Q₄Conducting and maintaining the second main switch tube Q₂Off, hold G₃Control enable signal G_3ENTo be negative, the voltage V at the point A is detected_AAnd voltage V at point E_ECalculating the input voltage V_IN＝V_APrimary side of the inductive current

Step B-2, at t₁Detecting voltage V at point E at the beginning of time_EAnd G₅Feedback signal G_5FBAnd the ZVS A stage is calculated through a fourth main switching tube Q₄Current of

Duration t_ZVSAmin(I_charge,V_IN) After time, when G₅Feedback signal G_5FBIf positive, the time is recorded as t₂And turn on the second main switch tube Q₂。t_ZVSAmin(I_charge,V_IN) Is the controller with respect to I_charge，V_INAs a function of (a) or (b),

note t_dead1＝t₂-t₁。

Step B-3, at t₂Time of day start detection G₅Feedback signal G_5FBWhen G is₅Feedback signal G_5FBWhen the current is negative, the current time is recorded as t₃And output G₃Control enable signal G_3ENIs negative.

Step B-4, at t₃At that time, the voltage at point C is detected immediately in a short time, and the voltage value V of the clamp capacitor is calculated_clamp＝V_C. Calculating secondary side output voltage:

wherein, V_f2、V_f3、V_f5Respectively a second main switch tube Q₂Clamping switch tube Q₃Synchronous rectifier tube Q₅Conduction voltage drop of the tube, N_PSIs the equivalent turn ratio, V, of the primary and secondary windings of the transformer_f2、V_f3、V_f5、N_PSAre constants set within the controller. Duration t_ZVSB(I_O,V_O) After the time, the time is recorded as t₄And turn on the fourth main switch tube Q₄。t_ZVSB(I_O,V_O) Is the controller with respect to I_O，V_OThe contents of the table look-up function of (2) are a two-dimensional array and represent different I_O，V_OThe duration of the ZVS B-phase is combined.

Step B-5, at t₄Voltage V at point E at the beginning of time_ECalculating the minimum value of the primary current as

Calculating the output current value I_O：

Wherein, C_OSS3Is the parasitic capacitance of the source drain end of the clamping switch tube Q3; l is_m、L_rRespectively an equivalent excitation inductance and an equivalent leakage inductance of a primary winding of the transformer, C_OSS3、L_m、L_rAre constants set within the controller. T is_SIs the total switching period of the converter, which is obtained by a timer.

The timer will count the working period t₀To t₄Plus t of the last duty cycle₅To t₆Time of (2) to obtain T_otherComparison of T_Smin-T_otherAnd t_clampminTaking the larger value of the two as the clamping stage time T_SminAnd t_clampminThe minimum duty cycle and the minimum clamping duration, respectively, of the converter are constants that are set in the controller. From t₄After the clamp phase time for starting to continuously obtain, the time is recorded as t₅And turn off the second main switch tube Q₂。

Step B-6, at t₅Starting to detect the voltage at the point E at the moment, and calculating the primary side inductive current

When primary side inductance current I_PUp to zero or from t₅Duration t_ZVSCmax(I_O,V_O) After the time, the time is recorded as t₆And turn on the first main switch tube Q₁。t_ZVSCmax(I_O,V_O) Is the controller with respect to I_O，V_OThe contents of the table look-up function of (2) are a two-dimensional array and represent different I_O，V_OThe longest duration of the ZVS C phase under the combination. Calculating the total switching period T of the converter_S＝t₆-t₀And when one switching period is finished, the step B-1 is executed again.

In the embodiment of the invention, the whole primary side voltage and current sampling control circuit can complete the calculation of the secondary side output voltage and current of the double-clamping ZVS buck-boost converter under the conditions of occupying less area and generating no extra power consumption basically, and ensures higher precision, thereby reducing the volume of the converter, reducing the cost and improving the working efficiency and the working performance of the converter.

The foregoing is only a partial embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the spirit of the invention, and these modifications and decorations also fall into the protection scope of the invention.

Claims

1. A primary side regulation control system of a double-clamping ZVS Buck-Boost converter comprises a main transformer, a first main switching tube, a second main switching tube, a clamping switching tube and a fourth main switching tube, wherein a first bridge arm formed by connecting the first main switching tube and the second main switching tube in series is connected to two ends of a direct current input power supply in parallel;

the primary side regulation control system is characterized by comprising:

an input voltage detection module for sampling the primary side input voltage of the main transformer,

the source-drain voltage detection module samples the drain-source voltage of the first main switch tube, the second main switch tube, the clamping switch tube and the fourth main switch tube,

a clamp voltage detection module for sampling the voltage of the clamp capacitor,

the inductive current detection module samples the output current of the fourth main switching tube,

a secondary side synchronous rectification circuit which processes the sampled output current of the secondary side loop of the main transformer and outputs a synchronous rectification gate signal,

an auxiliary winding, which comprises a secondary coil connected in series between the secondary synchronous rectification circuit and the secondary side ground, and a primary side loop for outputting the grid signal of the synchronous rectification tube refracted to the primary side in a voltage stabilizing manner,

a logic circuit for receiving the output voltage of the primary loop of the auxiliary winding, outputting the feedback signal of the synchronous rectifier tube, generating a gate signal of the clamping switch tube according to the control enable signal of the clamping switch tube, and,

a controller for receiving the sampling signal output by the input voltage detection module, the source-drain voltage detection module, the clamping voltage detection module, the inductive current detection module and the feedback signal of the output synchronous rectifier tube output by the logic circuit, calculating the real-time output voltage or the real-time output current of the converter according to the zero voltage conduction stage and the duration time of the whole working period of the clamping switch tube, calculating the primary side current threshold according to the real-time output voltage or the real-time output current of the converter, taking the time when the output current of the fourth main switch tube rises to the threshold as the end time of the energy input stage, taking the time when the drain-source voltage of the second main switch tube and the clamping switch tube drops to zero and the feedback signal of the synchronous rectifier tube is positive as the end time of the zero voltage conduction stage of the clamping switch tube, and taking the time when the output current of the fourth main switch tube drops to the leakage inductive current and the feedback signal of the synchronous rectifier tube is negative as, and outputting a clamping switch tube control enabling signal which is negative in the energy input stage, the zero voltage conduction stage of the fourth main switch tube, the zero voltage conduction stage of the clamping switch tube and positive in the zero voltage conduction stage and the energy transmission stage of the clamping switch tube by taking the moment when the drain-source voltage of the fourth main switch tube is reduced to zero as the end moment of the zero voltage conduction stage of the fourth main switch tube, taking the difference value between the minimum working period and the actual working period of the converter and the minimum value in the shortest duration time of the clamping stage as the end moment of the clamping stage, taking the moment when the drain-source voltage of the first main switch tube is reduced to zero or the moment when the output current of the fourth main switch tube is increased to zero as the end moment of the zero voltage conduction stage of the first main switch tube.

2. The primary-side regulation control system of the dual-clamp ZVS Buck-Boost converter as claimed in claim 1, wherein the controller comprises:

the voltage operation module receives a voltage sampling value of the clamping capacitor at the initial zero voltage conduction moment of the fourth main switching tube, outputs the real-time output voltage of the converter,

the current operation module receives a sampling value of the primary output voltage of the main transformer, receives sampling values of the output current of the fourth main switching tube at the end time of the energy input stage, the clamping stage and the zero voltage conduction stage of the clamping switching tube, receives sampling values of the zero voltage conduction stage of the clamping switching tube and the duration time of the whole working period, outputs the real-time output current of the converter, and,

the constant voltage and constant current operation module receives the real-time output voltage or real-time output current of the converter, receives sampling values of drain-source voltage of the first main switching tube, the second main switching tube, the clamping switching tube and the fourth main switching tube and primary side current of the main transformer, receives feedback signals of the synchronous rectifier tube output by the logic circuit, and outputs grid signals of the first main switching tube, the second main switching tube and the fourth main switching tube and control enabling signals of the clamping switching tube.

3. The primary-side regulation control system of the dual-clamp ZVS Buck-Boost converter of claim 1, wherein the logic circuit comprises:

a D latch, the input end of which is connected with the output voltage of the primary side loop of the auxiliary winding and outputs the feedback signal of the synchronous rectifier tube, and,

and one input end of the AND gate is connected with the output end of the D latch, and the other input end of the AND gate receives a clamping switch tube control enabling signal output by the controller and outputs a clamping switch tube gate signal.

4. The primary regulation control system of the double-clamp ZVS Buck-Boost converter as claimed in claim 1, wherein the primary input voltage of the main transformer, the drain-source voltage of the first main switch tube, the drain-source voltage of the second main switch tube, the drain-source voltage of the clamp switch tube, the drain-source voltage of the fourth main switch tube, the voltage of the clamp capacitor, the voltage V of the output current of the fourth main switch tube through the sampling first bridge arm power access point A_AVoltage V of midpoint B of first bridge arm_BVoltage V of connection point C of clamping switch tube and clamping capacitor_CVoltage V of midpoint D of second bridge arm_DAnd the voltage V of the source end E of the fourth main switch tube_EThe primary side input voltage V of the main transformer is determined by post calculation_INIs a V_IN＝V_AFirst main switch tube drain-source voltage V_DS1Is a V_DS1＝V_A-V_BSecond main switch tube drain-source voltage V_DS2Is a V_DS2＝V_BVoltage V of clamp switch tube drain-source_DS3Is a V_DS3＝V_C-V_DFourth main switch tube drain-source voltage V_DS4Is a V_DS4＝V_D-V_EVoltage V of the clamping capacitor_clmapI.e. the voltage V of the connection point C of the clamping switch tube and the clamping capacitor_CThe fourth main switch tube outputs current I_PIs composed of

R_SThe sampling resistor is connected in series with the source end of the fourth main switch tube.

5. The primary side regulation control system of the double-clamp ZVS Buck-Boost converter as claimed in claim 1, wherein the expression for calculating the real-time output voltage of the converter is:

V_Ofor real-time output of voltage, V, by the converter_clampTo clamp the capacitor voltage, V_f2、V_f3、V_f5Respectively the conduction voltage drop of the second main switch tube, the clamping switch tube and the synchronous rectifier tube, N_PSIs the equivalent turn ratio of the primary and secondary windings of the transformer.

6. The primary side regulation control system of the double-clamp ZVS Buck-Boost converter as claimed in claim 1, wherein the expression for calculating the real-time output current of the converter is:

I_Ofor outputting electricity V in real time from the converter_INIs a main transformerPrimary side input voltage current of transformer, t_dead1、T_SRespectively the zero voltage conduction phase of the clamping switch tube and the duration time of the whole working cycle, I_max、I_min、I_ZVSAThe output current of the fourth main switch tube at the end moment of the energy input stage, the clamping stage and the zero-voltage conduction stage of the clamping switch tube, C_OSS3Is parasitic capacitance of source and drain of the clamping switch tube, N_PSIs the equivalent turn ratio, L, of the primary and secondary windings of the transformer_m、L_rThe equivalent excitation inductance and the equivalent leakage inductance of the primary winding of the main transformer are respectively.

7. The primary-side regulation control system of the double-clamp ZVS Buck-Boost converter as claimed in claim 1, wherein the minimum duty cycle of the converter is a duty cycle corresponding to the highest operating frequency, and the actual duty cycle of the converter is the sum of the zero-voltage conduction duration of the first main switching tube in the previous duty cycle and the duration from the energy input stage to the clamping stage in the current duty cycle.

8. A primary side regulation control method of a double-clamping ZVS Buck-Boost converter is realized based on the primary side control system of any one of claims 1 to 7, and is characterized by specifically comprising the following six stages:

an energy input stage: at t₀Constantly turning on the first main switch tube, keeping the fourth main switch tube on, keeping the second main switch tube off, keeping the control enable signal of the clamping switch tube negative, and when the output current of the fourth main switch tube rises to t of the primary side current threshold value₁The first main switching tube and the fourth main switching tube are turned off at any time, and the clamping switching tube is controlled to control the enabling signal to jump to be positive;

and (3) a zero voltage conduction stage of a clamping switch tube: t when the drain-source voltage of the second main switch tube and the clamping switch tube is reduced to zero and the feedback signal of the synchronous rectifier tube is positive₂At the moment, the second main switch tube and the clamping switch tube are conducted;

and (3) energy transmission stage: the output current of the fourth main switch tube is reduced to leakage inductance current and the feedback signal of the synchronous rectifier tube isNegative t₃The clamping switch tube and the synchronous rectifier tube are turned off at any time, and the clamping switch tube is controlled to control the enabling signal to jump to be negative;

and a fourth main switching tube zero voltage conduction stage: the drain-source voltage of the fourth main switch tube drops to zero and is t₄At any moment, the fourth main switching tube is conducted;

a clamping stage: with t₄T after the time interval of the minimum value in the minimum working period and the actual working period and the shortest duration of the clamping stage₅Turning off the second main switching tube at any moment;

the first main switching tube zero voltage conduction stage: t when the drain-source voltage of the first main switch tube is reduced to zero or the output current of the fourth main switch tube is increased to zero₆And at the moment, the first main switching tube is conducted.

9. The primary-side regulation control method of the dual-clamp ZVS Buck-Boost converter as claimed in claim 8, wherein t is₂The current I is output according to the fourth main switching tube at any moment_chargePrimary side input voltage V of main transformer_INThe calculation results in that,

t_ZVSAminfor a zero voltage conduction step duration of the clamping switch tube at t_ZVSAminUp-accumulation of t₁The moment of time can determine t₂Time of day, C_OSS2The parasitic capacitance of the source-drain end of the second main switch tube.

10. The primary-side regulation control method of the dual-clamp ZVS Buck-Boost converter as claimed in claim 8, wherein t is₄The time is determined by searching the relation between the zero voltage conduction time of the fourth main switching tube and the real-time output voltage and current of the converter t₆And determining the time by searching the relation between the conduction time of the zero point of the first main switching tube and the real-time output voltage and current of the converter.