A wide load range zvs phase-shifted full-bridge converter circuit

Abstract

The present application relates to a kind of wide load range ZVS phase-shift full-bridge converter circuit, including first MOS tube, the drain of first MOS tube, the cathode of first clamping diode, the drain of third MOS tube are all connected with the anode of DC input power supply, the other end of auxiliary inductance is connected with the other end of high-frequency transformer T primary coil, and high-frequency transformer T secondary coil is connected with rectifier circuit.The present application changes the charge-discharge condition of the parasitic capacitance of lagging bridge arm MOS tube by increasing an auxiliary inductance in the traditional phase-shift full-bridge, so that the soft switching of lagging bridge arm MOS tube is no longer dependent on the resonant inductance, and the soft switching of all MOS tubes in a wide load range is realized, and the dead time can be flexibly configured by adjusting the size of auxiliary inductance, to avoid the circuit short circuit problem caused by too short dead time;The circuit structure is simple, and easy to realize in actual engineering.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, and in particular to a wide load range ZVS phase-shifted full-bridge converter circuit. Background Technology

[0002] Phase-shifted full-bridge circuits are widely used in high-power power conversion applications due to their high power output and input-output electrical isolation, especially in communication power supplies, server power supplies, welding machines, electric vehicle on-board chargers, and DC charging piles. A phase-shifted full-bridge circuit consists of a full-bridge circuit with four power switches, a high-frequency transformer, and an output rectifier and filter circuit. Two diagonally opposite switches conduct simultaneously, creating alternating positive and negative voltages applied to the primary side of the transformer, thus achieving energy transfer. The output voltage is adjusted by regulating the phase difference between the diagonally opposite switches. Traditional phase-shifted full-bridge converters utilize the leakage inductance of the transformer or the resonant inductance connected in series on the primary side of the high-frequency transformer, along with the parasitic capacitance of the switching devices, to achieve zero-voltage switching (ZVS) of the switches, i.e., conduction when the switching voltage is zero. This reduces the conduction losses of the phase-shifted full-bridge control converter, improves conversion efficiency, and reduces switching losses and electromagnetic interference (EMI).

[0003] However, due to its inherent circuit structure, the ZVS range of the lagging arm in a traditional phase-shifted full-bridge circuit is affected by the load. Under light load conditions, the energy stored in the inductor may not be sufficient to fully charge and discharge the parasitic capacitance of the switching transistor, leading to ZVS failure. This increases switching losses and reduces efficiency, necessitating alternative methods to achieve soft switching of the lagging arm and reduce losses. Generally, increasing leakage inductance solves the soft switching problem, but excessive leakage inductance can cause significant loss of duty cycle on the load side, reducing the circuit's load-carrying capacity. Active clamping auxiliary circuits are currently one of the most effective methods to extend the ZVS range; however, this method adds at least one auxiliary high-voltage MOSFET, increasing the driving risk. An error in the driving signal can lead to a short circuit. Furthermore, the introduction of active clamping changes the system transfer function, making the compensation network design more complex. Another approach is to use a saturated inductor to generate sufficient resonant energy to achieve ZVS; however, saturated inductors require careful selection of core materials and air gaps, are temperature-sensitive, and may generate noise. Other solutions, such as modifying the load-side structure, are also overly complex. Summary of the Invention

[0004] To address the challenges of achieving zero-voltage switching (ZVS) in the lagging bridge arm and the tendency to lose ZVS under light loads in traditional phase-shifted full-bridge converters, the primary objective of this invention is to provide a wide-load-range ZVS phase-shifted full-bridge converter circuit that achieves soft switching of all MOSFETs over a wide load range and features a simple circuit structure.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a wide load range ZVS phase-shifted full-bridge converter circuit, including a first MOSFET. Second MOSFET Third MOSFET Fourth MOSFET First clamping diode Second clamping diode Resonant inductor DC blocking capacitor Auxiliary inductor High-frequency transformer T and rectifier circuit, first MOSFET Drain diode, first clamping diode Cathode, third MOS transistor The drains of both are connected to a DC input power supply. The positive terminal, the second MOSFET The source diode and the second clamping diode anode, fourth MOSFET The sources are all connected to a DC input power supply. The negative terminal of the first MOSFET The source and the second MOSFET The drains are connected, and the first clamping diode is connected. anode and second clamping diode The cathode is connected to the third MOS transistor. The source and the fourth MOSFET The drains are connected, and the resonant inductor is connected. One end is connected to the first MOSFET The source of the second MOSFET Between the drain and resonant inductance The other end is connected to the first clamping diode. anode, second clamping diode cathode, DC blocking capacitor One end is connected to the DC blocking capacitor. The other end is connected to the auxiliary inductor. One end is connected to one end of the primary coil of the high-frequency transformer T, and the auxiliary inductor The other end is connected to the other end of the primary coil of the high-frequency transformer T, and the secondary coil of the high-frequency transformer T is connected to the rectifier circuit.

[0006] The first MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the second MOSFET A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the third MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the fourth MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection, the parasitic capacitance During operation, the resonant inductor current flows through... Auxiliary inductor current Charging and discharging.

[0007] The rectifier circuit includes a first rectifier diode. Second rectifier diode Third rectifier diode Fourth rectifier diode Filter inductor Filter capacitor and load First rectifier diode The anodes are connected to one end of the secondary coil of the high-frequency transformer T and the second rectifier diode, respectively. The cathode, the first rectifier diode The cathodes are respectively connected to the third rectifier diode. Cathode, filter inductor One end is connected to the filter inductor. The other end is connected to the filter capacitor One end is connected to the second rectifier diode. The anodes are respectively connected to the fourth rectifier diode. anode, filter capacitor The other end is connected to the third rectifier diode. The anodes are respectively connected to the other end of the secondary coil of the high-frequency transformer T and the fourth rectifier diode. The cathode is connected, and the load Parallel connection to the filter capacitor At both ends.

[0008] The first MOS transistor With the second MOSFET Forming the advanced bridge arm, the first MOSFET With the second MOSFET The drive signal has a dead time. Parasitic capacitance , Dead time The charging and discharging are completed internally; the third MOSFET With the fourth MOSFET Forming the advanced bridge arm, the third MOSFET With the fourth MOSFET The drive signal has a dead time. Parasitic capacitance , Dead time The charging and discharging are completed internally; the resonant inductor current... parasitic capacitance , Charging and discharging, auxiliary inductor current parasitic capacitance , Charging and discharging.

[0009] The first rectifier diode Parallel parasitic capacitance The second rectifier diode Parallel parasitic capacitance The third rectifier diode Parallel parasitic capacitance The fourth rectifier diode Parallel parasitic capacitance .

[0010] The dead time Greater than parasitic capacitance Parasitic capacitance The time required to complete charging and discharging, the dead time Greater than parasitic capacitance Parasitic capacitance The time required to complete the charge and discharge process is less than the resonant inductor current. It will be past midnight.

[0011] Resonant inductor current For auxiliary inductor current With primary current sum:

[0012] ;

[0013] primary current The magnitude is the load current referred to the primary side:

[0014] ;

[0015] In the formula, For output voltage, The primary and secondary turns ratio of the high-frequency transformer T;

[0016] exist , Auxiliary inductor current before charging and discharging and resonant inductor current Increase to maximum value, auxiliary inductor current maximum value for:

[0017] ;

[0018] In the formula, f is the switching frequency, k is the proportion of the phase shift angle of the conduction signal of the leading and lagging bridge arms in the switching cycle, and m is the proportion of the dead time in the switching cycle.

[0019] Resonant inductor current The maximum value is:

[0020] .

[0021] As can be seen from the above technical solution, the beneficial effects of the present invention are as follows: First, the present invention adds an auxiliary inductor to the traditional phase-shifted full-bridge circuit. First, by changing the charging and discharging conditions of the parasitic capacitance of the lagging bridge arm MOSFETs, the soft switching of the lagging bridge arm MOSFETs no longer relies on the resonant inductor. This solves the problem that the energy stored in the resonant inductor of the traditional phase-shifted full-bridge is insufficient to fully charge and discharge the parasitic capacitance of the lagging bridge arm switching transistors under light load conditions, making it difficult to achieve soft switching of the lagging bridge arm. At the same time, it avoids the problem of severe loss of duty cycle on the load side caused by excessively large resonant inductors, which reduces the load-carrying capacity of the circuit. Second, this invention can meet the energy required for the complete charging and discharging of the parasitic capacitance of the lagging bridge arm MOSFETs under different load conditions by adjusting the size of the auxiliary inductor, realizing soft switching of all MOSFETs over a wide load range. At the same time, the dead time can be flexibly configured by adjusting the size of the auxiliary inductor, avoiding the short circuit problem caused by excessively short dead time. Third, this invention can achieve soft switching over a wide load range by adding only one passive auxiliary inductor device. The circuit structure is simple, does not change the original phase-shifted full-bridge control logic, avoids complex circuit operation analysis and control logic analysis, and is easy to implement in practical engineering. Attached Figure Description

[0022] Figure 1 This is a circuit topology diagram of the present invention;

[0023] Figure 2 This is a waveform diagram of the main working state of the present invention;

[0024] Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8These are schematic diagrams of the working states of modes 1, 2, 3, 4, 5, and 6 of the present invention. Detailed Implementation

[0025] like Figure 1 As shown, a wide load range ZVS phase-shifted full-bridge converter circuit includes a first MOSFET. Second MOSFET Third MOSFET Fourth MOSFET First clamping diode Second clamping diode Resonant inductor DC blocking capacitor Auxiliary inductor High-frequency transformer T and rectifier circuit, first MOSFET Drain diode, first clamping diode Cathode, third MOS transistor The drains of both are connected to a DC input power supply. The positive terminal, the second MOSFET The source diode and the second clamping diode anode, fourth MOSFET The sources are all connected to a DC input power supply. The negative terminal of the first MOSFET The source and the second MOSFET The drains are connected, and the first clamping diode is connected. anode and second clamping diode The cathode is connected to the third MOS transistor. The source and the fourth MOSFET The drains are connected, and the resonant inductor is connected. One end is connected to the first MOSFET The source of the second MOSFET Between the drain and resonant inductance The other end is connected to the first clamping diode. anode, second clamping diode cathode, DC blocking capacitor One end is connected to the DC blocking capacitor. The other end is connected to the auxiliary inductor. One end is connected to one end of the primary coil of the high-frequency transformer T, and the auxiliary inductor The other end is connected to the other end of the primary coil of the high-frequency transformer T, and the secondary coil of the high-frequency transformer T is connected to the rectifier circuit.

[0026] The first MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the second MOSFET A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the third MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the fourth MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection, the parasitic capacitance During operation, the resonant inductor current flows through... Auxiliary inductor current Charging and discharging. Auxiliary inductor current. The size can be adjusted by changing the auxiliary inductor. Size adjustment.

[0027] The rectifier circuit includes a first rectifier diode. Second rectifier diode Third rectifier diode Fourth rectifier diode Filter inductor Filter capacitor and load First rectifier diode The anodes are connected to one end of the secondary coil of the high-frequency transformer T and the second rectifier diode, respectively. The cathode, the first rectifier diode The cathodes are respectively connected to the third rectifier diode. Cathode, filter inductor One end is connected to the filter inductor. The other end is connected to the filter capacitor One end is connected to the second rectifier diode. The anodes of the four rectifier diodes are respectively connected to the fourth rectifier diode. anode, filter capacitor The other end is connected to the third rectifier diode. The anodes are respectively connected to the other end of the secondary coil of the high-frequency transformer T and the fourth rectifier diode. The cathode is connected, and the load Parallel connection to the filter capacitor At both ends.

[0028] The first MOS transistor With the second MOSFET Forming the advanced bridge arm, the first MOSFET With the second MOSFET The drive signal has a dead time. Parasitic capacitance , Dead time The charging and discharging are completed internally; the third MOSFET With the fourth MOSFET Forming the advanced bridge arm, the third MOSFET With the fourth MOSFET The drive signal has a dead time. Parasitic capacitance , Dead time The charging and discharging are completed internally; the resonant inductor current... parasitic capacitance , Charging and discharging, auxiliary inductor current parasitic capacitance , Charging and discharging.

[0029] The first rectifier diode Parallel parasitic capacitance The second rectifier diode Parallel parasitic capacitance The third rectifier diode Parallel parasitic capacitance The fourth rectifier diode Parallel parasitic capacitance .

[0030] The dead time Greater than parasitic capacitance Parasitic capacitance The time required to complete charging and discharging, the dead time Greater than parasitic capacitance Parasitic capacitance The time required to complete the charge and discharge process is less than the resonant inductor current. It will be past midnight.

[0031] Resonant inductor current For auxiliary inductor current With primary current sum:

[0032] ;

[0033] primary current The magnitude is the load current referred to the primary side:

[0034] ;

[0035] In the formula, For output voltage, The primary and secondary turns ratio of the high-frequency transformer T;

[0036] exist , Auxiliary inductor current before charging and discharging and resonant inductor current Increase to maximum value, auxiliary inductor current maximum value for:

[0037] ;

[0038] In the formula, f is the switching frequency, k is the proportion of the phase shift angle of the conduction signal of the leading and lagging bridge arms in the switching cycle, and m is the proportion of the dead time in the switching cycle.

[0039] Resonant inductor current The maximum value is:

[0040] .

[0041] like Figure 2 As shown, the converter has 12 operating modes within one switching cycle, namely: , , , , , , , , , , , ,in This is the first half of the cycle. This is the second half of the cycle. The following is an analysis of the working conditions of each working mode.

[0042] Before the analysis, the following assumptions are made: all devices are ideal devices, and parasitic capacitance is... Parasitic capacitance The output filter capacitor is very large, the output voltage ripple is negligible, the transformer magnetizing inductance is very large, the leakage inductance is negligible, and the output filter inductance is regarded as a constant current source. , All are intermediate variables.

[0043] Working mode 1 ( )like Figure 3 As shown:

[0044] At this stage, the first MOSFET Fourth MOSFET First rectifier diode Fourth rectifier diode It is in the on state because the first MOSFET is in the on state. Fourth MOSFET On, auxiliary inductor The voltage on the output is the voltage referred to the primary winding of the high-frequency transformer T, where the voltage flows through the auxiliary inductor. Auxiliary inductor current It increases linearly, and the slope of the increase is:

[0045] ;

[0046] Let the half-switching period be If the switching frequency is f, then The phase shift value of the MOSFET turn-on signal is Dead time is Then the auxiliary inductor current The linearly increasing time is Auxiliary inductor current The linear increase is :

[0047] ;

[0048] The auxiliary inductance can be obtained based on symmetry. maximum value for:

[0049] ;

[0050] During this stage, the current flows through the resonant inductor resonant inductor current For auxiliary inductor current The sum of the primary current and the output current equals the primary current. Current referred to the primary side of the transformer:

[0051] ;

[0052] Resonant inductor current at all times Get the maximum value The output current at that moment Therefore, the resonant inductor current maximum value :

[0053] ;

[0054] Working Mode 2 ( )like Figure 4 As shown:

[0055] First MOSFET Turn off, fourth MOSFET The first MOSFET remains on. At the moment of shutdown, due to parasitic capacitance The voltage cannot change abruptly; the first MOSFET... It can be approximated as zero-voltage turn-off. Furthermore, since the inductor current cannot change abruptly, the resonant inductor current... From the first MOSFET Transfer to parasitic capacitance and parasitic capacitance parasitic capacitance Charging, for parasitic capacitance Discharge, voltage at points a and b decline, Parasitic capacitance at all times After charging and discharging is complete, the potential at point a drops to 0, and the voltage across the primary and secondary sides of the high-frequency transformer T decreases accordingly. The second rectifier diode... Second rectifier diode parasitic capacitance The discharge continues to power the load. During this phase, the auxiliary inductor... With filter inductor The inductance converted to the primary side is connected in parallel with the resonant inductance. In series, the values ​​are usually large, so the parasitic capacitance is approximated. and by Assuming the current remains constant, let the parasitic capacitance be... Charging time, parasitic capacitance The discharge time is all ,exist Within a time period, parasitic capacitance The voltage increases from 0 to Parasitic capacitance The voltage on is from Reduced to 0. This stage... , , Satisfying instantaneous relationships:

[0056] ;

[0057] According to the above formula, we can obtain... for:

[0058] ;

[0059] Because the potential at point a is Reduced to 0, ignoring the effect of DC blocking capacitance, current flows through the resonant inductor. The rate of change of current is:

[0060] ;

[0061] Combined with parasitic capacitance and Charge / discharge duration and resonant inductance The rate of change of current is obtained The current flows through the resonant inductor at all times current for:

[0062] ;

[0063] An auxiliary inductor is typically used to reduce circulating current. The value should be as large as possible, much larger than the resonant inductance. It is approximated that the flow passes through the auxiliary inductor during this stage. Auxiliary inductor current Keep the maximum value constant.

[0064] Working mode 3 ( )like Figure 5 As shown:

[0065] After a certain time, due to the parasitic diode Turn on, second MOSFET The voltage on the second MOSFET is clamped to the diode's forward voltage. Zero-voltage conduction can be achieved by simply turning on the circuit, in order to ensure the parasitic capacitance... , Fully charged and discharged, dead time Must meet:

[0066] ;

[0067] In this mode, the resonant inductor current With auxiliary inductor current The voltage remains unchanged, in a primary-side circulating current state, and the voltage between points a and b is... The value is 0, indicating the first rectifier diode. Fourth rectifier diode In freewheeling mode, parasitic capacitance Continue discharging, primary current It is still equal to the value of the secondary winding current referred to the primary winding.

[0068] Working Mode 4 ( )like Figure 6 As shown:

[0069] Second rectifier diode at time Third rectifier diode parasitic capacitance The voltage drops to zero, and the second rectifier diode... Third rectifier diode Natural conduction, resonant inductor current Auxiliary inductor current Primary current It remains in a state of natural continuous flow and remains unchanged until The process ends at that point.

[0070] Working mode 5 ( )like Figure 7 As shown:

[0071] exist At that moment, the fourth MOSFET Turn off, auxiliary inductor current Start supplying the third MOSFET parasitic capacitance Discharge, and simultaneously supply power to the fourth MOSFET. parasitic capacitance Charge, Parasitic capacitance at all times Charging and discharging are complete. During this stage, the potential at point b gradually increases, the coupling relationship between the primary and secondary sides is no longer present, and the primary current... Gradually decreasing to 0, the resonant inductor current It also gradually decreases with the auxiliary inductor current. Equal. Under normal circumstances, to reduce circulating current, the auxiliary inductor... The parasitic capacitance is relatively large, and can be approximated as large. and by Assuming the magnitude of the charging and discharging current remains constant, and considering the parasitic capacitance... Charging time, parasitic capacitance The discharge time is all ,exist Within a time period, parasitic capacitance The voltage increases from 0 to Parasitic capacitance The voltage on is from Reduced to 0; this stage , , The following instantaneous relationships are satisfied:

[0072] ;

[0073] According to the above formula, we can obtain... for:

[0074] ;

[0075] Working mode 6 ( )like Figure 8 As shown:

[0076] At that moment, the third MOSFET parasitic diode Turn on, third MOSFET The voltage on the diode is clamped to the parasitic diode. The on-state voltage, After a certain time, the third MOSFET Zero-voltage conduction can be achieved by turning on the circuit. Since the voltage at point b is... Since the potentials at points a and c are lower than those at point b, the resonant inductor current... and auxiliary inductor current The resonant inductor current begins to decrease. Starting from 0 and increasing in reverse, the primary and secondary currents of the high-frequency transformer T gradually increase, and the coupling relationship begins to be established, flowing through the parasitic diode. The current is transferred to the second MOSFET. Third MOSFET The voltage value referred from the primary side to the secondary side of the high-frequency transformer T will affect the second rectifier diode. Third rectifier diode Second rectifier diode Third rectifier diode In freewheeling mode, the first rectifier diode Fourth rectifier diode parasitic capacitance , Start charging. At a certain moment, the primary current increases in the reverse direction to provide energy to the secondary side, and the mode ends.

[0077] To ensure the third MOSFET Zero-voltage turn-on requires the dead time of the lagging bridge arm to meet the dead time requirement. This makes the third MOSFET The conduction signal appears after the voltage on it is 0. Additionally, because... Auxiliary inductor current after time From the maximum value Start decreasing as the auxiliary inductor current decreases. Reduce to the level of the primary current When they are equal, the resonant inductor current After crossing zero, the reverse current on the primary side will supply the parasitic capacitance. Charging, third MOSFET The voltage across the bridge arm is not zero, thus losing its soft-switching characteristics. Therefore, the dead time of the lagging bridge arm must satisfy the auxiliary inductor current. Based on the above analysis, the dead time of the lagging bridge arm The following conditions must be met:

[0078] ;

[0079] At that moment, the first rectifier diode Fourth rectifier diode parasitic capacitance , Once charging is complete, the primary side begins to transfer energy to the secondary side. After this, the converter circuit enters the negative half-cycle, and its operation is symmetrical to that of the positive half-cycle.

[0080] In summary, this invention introduces an auxiliary inductor into the traditional phase-shifted full-bridge circuit. The ZVS condition of the hysteresis arm can be changed by altering the auxiliary inductance. By adjusting the magnitude of the charging and discharging current of the parasitic capacitance of the lagging bridge arm MOSFET and the zero-crossing time of the resonant inductor current, the parasitic capacitance of the lagging bridge arm MOSFET can be fully charged and discharged. At the same time, the reverse charging and discharging of the parasitic capacitance caused by the decrease in resonant current is avoided, ensuring that the lagging bridge arm switch can achieve ZVS in a wide load range, thus solving the problem of the difficulty in implementing soft switching of the lagging bridge arm in traditional phase-shifted full-bridge circuits.

[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A wide load range ZVS phase-shifted full-bridge converter circuit, characterized in that: Including the first MOSFET Second MOSFET Third MOSFET Fourth MOSFET First clamping diode Second clamping diode Resonant inductor DC blocking capacitor Auxiliary inductor High-frequency transformer T and rectifier circuit, first MOSFET Drain diode, first clamping diode Cathode, third MOS transistor The drains of both are connected to a DC input power supply. The positive terminal, the second MOSFET The source diode and the second clamping diode anode, fourth MOSFET The sources are all connected to a DC input power supply. The negative terminal of the first MOSFET The source and the second MOSFET The drains are connected, and the first clamping diode is connected. anode and second clamping diode The cathode is connected to the third MOS transistor. The source and the fourth MOSFET The drains are connected, and the resonant inductor is connected. One end is connected to the first MOSFET The source of the second MOSFET Between the drain and the resonant inductor The other end is connected to the first clamping diode. anode, second clamping diode cathode, DC blocking capacitor One end is connected to a DC blocking capacitor. The other end is connected to the auxiliary inductor. One end is connected to one end of the primary coil of the high-frequency transformer T, and the auxiliary inductor The other end is connected to the other end of the primary coil of the high-frequency transformer T, and the secondary coil of the high-frequency transformer T is connected to the rectifier circuit.

2. The wide load range ZVS phase-shifted full-bridge converter circuit according to claim 1, characterized in that: The first MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the second MOSFET A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the third MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection; the fourth MOS transistor A parasitic diode is connected between the drain and source. Parasitic capacitance With parasitic diodes Parallel connection, the parasitic capacitance During operation, the resonant inductor current flows through... Auxiliary inductor current Charging and discharging.

3. The wide load range ZVS phase-shifted full-bridge converter circuit according to claim 1, characterized in that: The rectifier circuit includes a first rectifier diode. Second rectifier diode Third rectifier diode Fourth rectifier diode Filter inductor Filter capacitor and load First rectifier diode The anodes are connected to one end of the secondary coil of the high-frequency transformer T and the second rectifier diode, respectively. The cathode, the first rectifier diode The cathodes are respectively connected to the third rectifier diode. Cathode, filter inductor One end is connected to the filter inductor. The other end is connected to the filter capacitor One end is connected to the second rectifier diode. The anodes are respectively connected to the fourth rectifier diode. anode, filter capacitor The other end is connected to the third rectifier diode. The anodes are respectively connected to the other end of the secondary coil of the high-frequency transformer T and the fourth rectifier diode. The cathode is connected, and the load Parallel connection to the filter capacitor At both ends.

4. The wide load range ZVS phase-shifted full-bridge converter circuit according to claim 2, characterized in that: The first MOS transistor With the second MOSFET Forming the advanced bridge arm, the first MOSFET With the second MOSFET The drive signal has a dead time. Parasitic capacitance , Dead time The charging and discharging are completed internally; the third MOSFET With the fourth MOSFET Forming the advanced bridge arm, the third MOSFET With the fourth MOSFET The drive signal has a dead time. Parasitic capacitance , Dead time The charging and discharging are completed internally; the resonant inductor current... parasitic capacitance , Charging and discharging, auxiliary inductor current parasitic capacitance , Charging and discharging.

5. The wide load range ZVS phase-shifted full-bridge converter circuit according to claim 3, characterized in that: The first rectifier diode Parallel parasitic capacitance The second rectifier diode Parallel parasitic capacitance The third rectifier diode Parallel parasitic capacitance The fourth rectifier diode Parallel parasitic capacitance .

6. The wide load range ZVS phase-shifted full-bridge converter circuit according to claim 4, characterized in that: The dead time Greater than parasitic capacitance Parasitic capacitance The time required to complete charging and discharging, the dead time Greater than parasitic capacitance Parasitic capacitance The time required to complete the charge and discharge process is less than the resonant inductor current. It will be past midnight.

7. The wide load range ZVS phase-shifted full-bridge converter circuit according to claim 4, characterized in that: Resonant inductor current For auxiliary inductor current With primary current sum: ； primary current The magnitude is the load current referred to the primary side: ； In the formula, For output voltage, The primary and secondary turns ratio of the high-frequency transformer T; exist , Auxiliary inductor current before charging and discharging and resonant inductor current Increase to maximum value, auxiliary inductor current maximum value for: ； In the formula, f is the switching frequency, k is the proportion of the phase shift angle of the conduction signal of the leading and lagging bridge arms in the switching cycle, and m is the proportion of the dead time in the switching cycle. Resonant inductor current The maximum value is: 。

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