Auxiliary resonance full-soft switching FSS-BUCK direct current converter and control method thereof

Abstract

The invention discloses an auxiliary resonance full-soft switching FSS-BUCK direct current converter which comprises an input filter capacitor C0, a main switching tube S1, an auxiliary resonance switching tube S1a, a resonant capacitor Cr1, an output filter inductor L1, a resonant inductor Lr1, a fly-wheel diode D1 and an output filter capacitor C1. The invention further discloses a control method. The control method of the FSS-BUCK direct-current converter is as simple as control of a common BUCK topology, the efficiency of a traditional BUCK topology circuit is greatly improved, the limitation of the switching frequency of a power electronic device is broken through, the power electronic device can be used in an over-limit mode, and the FSS-BUCK direct-current converter is a breakthrough key technical invention in the field of new energy in the future.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of power supply and relates to an auxiliary resonant full-soft switching FSS-BUCK direct current converter and a control method thereof.

[0002] In today's era of pursuing high-efficiency energy conversion, as the core of power supply, the performance of a DC / DC converter directly determines the performance upper limit of various electronic devices, new energy systems (such as lithium battery charging and discharging, photovoltaic inverters, etc.), server power supplies and industrial power supplies. Increasing the switching frequency is the key path to reduce the size of the converter and improve the power density. However, in traditional non-isolated Buck, Boost and other basic PWM converters, the power switching device works in a hard switching mode, and the voltage-current overlap is long during the switching transient, resulting in high switching loss. This not only restricts the increase of the switching frequency, but also causes electromagnetic interference noise and heat management problems, which become the bottleneck of achieving high efficiency and high power density design.

[0003] The existing soft switching topology has the problems of increased auxiliary devices, complex control, high cost and only partial soft switching of power electronic switching devices.

[0004] Therefore, developing a high-efficiency, few auxiliary devices, simple control, low-cost and full-soft switching power conversion topology is a key power conversion technology urgently needed in the field of new energy in the era of high efficiency. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies of the existing applications, one of the purposes of the present application is to provide an auxiliary resonant full-soft switching FSS-BUCK direct current converter topology, which can be used in the fields of lithium battery charging and discharging, photovoltaic inverters, server power supplies and industrial power supplies, etc., and can greatly reduce the converter loss and significantly improve the efficiency of the power converter.

[0006] In order to achieve the above object, the technical scheme adopted by the present application to solve its technical problems is: an auxiliary resonant full-soft switching FSS-BUCK direct current converter, the circuit comprising an input filter capacitor C0, a main switch S1, an auxiliary resonant switch S1a, a resonant capacitor Cr1, an output filter inductor L1, a resonant inductor Lr1, a freewheeling diode D1 and an output filter capacitor C1; the first end of the input filter capacitor C0 is connected with the positive pole of an input voltage Vin and the first end of the main switch S1 and the auxiliary resonant switch S1a, the second end of the input filter capacitor C0 is connected with the negative pole of the input voltage Vin, the negative pole of an output voltage Vout and the second end of the freewheeling diode D1 and the output filter capacitor C1; the first end of the main switch S1 is connected with the positive pole of the input voltage Vin, the auxiliary resonant switch S1a and the first end of the input filter capacitor C0, the second end of the main switch S1 is connected with the first end of the output filter inductor L1 and the resonant inductor Lr1; the first end of the auxiliary resonant switch S1a is connected with the positive pole of the input voltage Vin and the first end of the main switch S1 and the input filter capacitor C0, the second end of the auxiliary resonant switch S1a is connected with the first end of the resonant capacitor Cr1; the first end of the resonant capacitor Cr1 is connected with the second end of the auxiliary resonant switch S1a, the second end of the resonant capacitor Cr1 is connected with the second end of the resonant inductor Lr1 and the first end of the freewheeling diode D1; the first end of the resonant inductor Lr1 is connected with the second end of the main switch S1 and the first end of the output filter inductor L1, the second end of the resonant inductor Lr1 is connected with the second end of the resonant capacitor Cr1 and the first end of the freewheeling diode D1; the first end of the freewheeling diode D1 is connected with the second end of the resonant capacitor Cr1 and the resonant inductor Lr1, the second end of the freewheeling diode D1 is connected with the negative pole of the input voltage Vin, the negative pole of the output voltage Vout and the second end of the input filter capacitor C0 and the output filter capacitor C1; the first end of the output filter inductor L1 is connected with the second end of the main switch S1 and the first end of the resonant inductor Lr1, the second end of the output filter inductor L1 is connected with the first end of the output filter capacitor C1 and the positive pole of the output voltage Vout; the first end of the output filter capacitor C1 is connected with the positive pole of the output voltage Vout and the second end of the output filter inductor L1, the second end of the output filter capacitor C1 is connected with the negative pole of the input voltage Vin, the negative pole of the output voltage Vout and the second end of the freewheeling diode D1 and the input filter capacitor C0.

[0007] Further, the main switch S1 is an IGBT, IGCT or MOSFET; the auxiliary resonant switch S1a is an IGBT, IGCT or MOSFET; the resonant capacitor Cr1 is a non-polarity capacitor; the input filter capacitor C0 and the output filter capacitor C1 are electrolytic capacitors, film capacitors or super capacitors with polarity.

[0008] The second object of the present application is to provide a control method of an auxiliary resonant full-soft switching FSS-BUCK direct current converter, and the steps are as follows: before the main switch S1 is turned on, the converter is in a freewheeling mode, the current flows through the freewheeling diode D1 and the output filter inductor L1 to the output voltage, when the main switch S1 is turned on, the main switch S1 realizes ZCS turn-on due to the existence of the resonant inductor Lr1; at the same time, the freewheeling diode D1 can realize reverse ZVS turn-off due to the existence of the resonant capacitor Cr1; after a certain time Δt1, the current flowing through the auxiliary resonant switch S1a is negative, at this time, the auxiliary resonant switch S1a can realize ZVS turn-off, after the resonant inductor Lr1 and the resonant capacitor Cr1 resonate, the converter is in a freewheeling mode; after a certain time, the auxiliary resonant switch S1a is turned on, the resonant inductor Lr1 and the resonant capacitor Cr1 start reverse resonance, the auxiliary resonant switch S1a can realize ZCS turn-on due to the existence of the resonant inductor Lr1; after a certain time Δt2, the current flowing through the main switch S1 is negative, the main switch S1 can realize ZVS turn-off, so that the turn-on loss and turn-off loss of the main switch S1 and the auxiliary resonant switch S1a are both zero, and the reverse recovery loss of the freewheeling diode D1 is zero.

[0009] The further steps are as follows: Before t0, the circuit is in a freewheeling stage, the current flows back to the output side through the freewheeling diode D1 and the output filter inductor L1; At t0, the main switch S1 is turned on, the main switch S1 is ZCS turned on, the freewheeling diode D1 current and the resonant inductor Lr1 current flow from I L to 0, the freewheeling diode D1 is in a forward conducting state, the resonant inductor Lr1 voltage is clamped at the DC bus voltage, the resonant capacitor Cr1 voltage is kept at the DC bus voltage, and the main switch S1 current starts to gradually increase from 0 to the output filter inductor current I L ; At t1, the freewheeling diode D1 current decreases to zero and naturally turns off, at this time, the main switch current is I L , the resonant inductor Lr1 current decreases to zero, the resonant capacitor Cr1 voltage is left positive and right negative, the resonant circuit composed of the main switch S1, the auxiliary resonant switch S1a, the resonant capacitor Cr1 and the resonant inductor Lr1 starts to resonate, the resonant capacitor Cr1 voltage decreases, the resonant inductor Lr1 and the auxiliary resonant switch S1a current starts to increase from zero in reverse, and the main switch current starts to increase from I L ; In the time of t2~t3, the resonance circuit continues to resonate, the resonance capacitor Cr1 voltage starts from zero and reversely charges, the resonance capacitor Cr1 current gradually decreases from the positive maximum value to zero until the time t3, the current of the auxiliary resonance switch tube S1a and the resonance inductor Lr1 gradually decreases from the negative maximum value to zero, the current of the main switch tube S1 gradually decreases from the positive maximum value to the current I L , At the time t3, the resonance capacitor Cr1 voltage reaches the reverse maximum value V in , the resonance current of the resonance circuit is zero, the auxiliary resonance switch tube S1a blocks the resonance circuit and stops resonating, the current of the main switch tube S1 is equal to the current of the output filter inductor L1 I L , the circuit enters the forward conduction energy transmission stage, the auxiliary resonance switch tube S1a bears the reverse voltage equal to the resonance capacitor Cr1 voltage V in , the freewheeling diode D1 reverse voltage is equal to the input voltage V in , the voltage and current of the resonance inductor Lr1 are zero; At the time t4, the auxiliary resonance switch tube S1a is turned on, the resonance circuit starts to resonate reversely, the current of the main switch tube S1 gradually decreases, the current of the auxiliary resonance switch tube S1a and the resonance inductor Lr1 gradually increases from zero, realizing the ZCS turn-on of the auxiliary resonance switch tube S1a, the resonance capacitor Cr1 starts to resonate and discharge, the current gradually reversely increases from zero, and the voltage gradually decreases; Until the time t5, the current of the main switch tube S1 decreases from I L to zero, and the current of the auxiliary resonance switch tube S1a increases to I L ; In the time of t5~t6, the resonance circuit continues to resonate reversely, the current of the main switch tube S1 decreases to zero and starts to reversely increase, the current of the auxiliary resonance switch tube S1a, the resonance capacitor Cr1 and the resonance inductor Lr1 continues to increase according to the resonance law; From the time t6, the current of the auxiliary resonance switch tube S1a and the resonance inductor Lr1 gradually decreases from the positive maximum value, the current of the resonance capacitor Cr1 starts to rise from the negative maximum value, and the voltage starts to increase reversely from zero; From the time t7, the resonance capacitor Cr1 voltage starts to reversely charge with constant current I L , the resonance capacitor Cr1 voltage linearly increases to the input side voltage V in .

[0010] Further, at the t5 moment, the current of the auxiliary resonant switch S1a, the resonant capacitor Cr1 and the resonant inductor Lr1 continues to increase according to the resonance law until the t6 moment when the resonance reaches 1 / 4 of the resonance period.

[0011] Further, at the t6 moment, the resonance loop reaches 1 / 4 of the resonance period, the current of the main switch S1 reaches the maximum negative value, the current of the auxiliary resonant switch S1a and the resonant inductor Lr1 reaches the maximum positive value, and the current of the resonant capacitor Cr1 reaches the maximum negative value, and the voltage is zero.

[0012] Further, at the t7 moment, the current of the main switch S1 again resonates to zero, the current of the auxiliary resonant switch S1a, the resonant capacitor Cr1 and the resonant inductor Lr1 reaches I L .

[0013] The present application has the following beneficial effects: 1, the pioneering all-zero switching loss performance: the auxiliary resonant commutation switch in the FSS-BUCK topology is only put into work within a certain time before and after the main switch is turned on and off, and forms a resonance loop with the main switch and the resonant inductor and the resonant capacitor to assist commutation, so as to achieve ZVS turn-off and ZCS turn-on of the main switch, ZVS turn-off and ZCS turn-on of the auxiliary resonant switch, and ZVS turn-off of the freewheeling diode. All power electronic devices achieve soft switching. The FSS-BUCK topology can theoretically reach more than 99% in most of the full power and full voltage range, greatly improving the flatness of the efficiency curve. The main loss of the topology is only the conduction loss, which provides a new solution to break through the efficiency limit.

[0014] 2, the simplicity and high power density potential of the auxiliary resonant topology: the FSS-BUCK topology adopts auxiliary resonant commutation technology, which solves the pain point that large power IGBT and other switching devices can only work at low switching frequency, can completely ignore the switching loss of power electronic devices, breaks through the limit of high switching frequency, and makes it work reliably at a higher switching frequency. Avoid the complexity and volume limitation brought by the isolation transformer. Eliminate switching loss completely, clear the obstacles for working at several hundred kHz or even MHz level of ultra-high switching frequency, and have great potential for power density improvement.

[0015] 3, superior engineering application value: the FSS-BUCK topology structure is compact, and the control strategy is simple and efficient, especially suitable for non-isolated medium power application scenarios with strict requirements on efficiency, size and cost, such as data center 48V bus conversion, photovoltaic direct current optimization, electric vehicle on-board power supply, etc., which has clear engineering application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1is the circuit topology of the converter of the present application; Figure 2 is the working waveform schematic diagram of the FSS-BUCK circuit of the present application; Figure 3 is the working mode 0 schematic diagram before t0 moment; Figure 4 is the working mode 1 schematic diagram from t0 to t1 moment; Figure 5 is the working mode 2 schematic diagram from t1 to t2 moment; Figure 6 is the working mode 3 schematic diagram from t2 to t3 moment; Figure 7 is the working mode 4 schematic diagram from t3 to t4 moment; Figure 8 is the working mode 5 schematic diagram from t4 to t5 moment; Figure 9 is the working mode 6 schematic diagram from t5 to t6 moment; Figure 10 is the working mode 7 schematic diagram from t6 to t7 moment; Figure 11 is the working mode 8 schematic diagram from t7 to t8 moment; Figure 12 is the working mode 0 schematic diagram after t8 moment. DETAILED DESCRIPTION

[0017] In order to make the present application clearer, the following further describes the application content with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and the protection scope is not limited to the examples.

[0018] The present application is further described in detail below with reference to specific examples, but the embodiments of the present application are not limited thereto.

[0019] Reference Figure 1 , Figure 2As shown, the embodiment provides an auxiliary resonant full-soft switching FSS-BUCK direct current converter, the circuit comprises an input filter capacitor C0, a main switch tube S1, an auxiliary resonant switch tube S1a, a resonant capacitor Cr1, an output filter inductor L1, a resonant inductor Lr1, a freewheeling diode D1 and an output filter capacitor C1. The main switch tube S1 and the freewheeling diode D1 are used to realize power conversion of the BUCK direct current converter; the auxiliary resonant circuit comprises the auxiliary resonant switch tube S1a, the auxiliary resonant inductor Lr1 and the auxiliary resonant capacitor Cr1, which is used for auxiliary resonant commutation before and after the main switch tube S1 is turned on and turned off, so as to achieve the functions of ZVS turn-off and ZCS turn-on. By introducing the auxiliary resonant circuit, the main switch and the auxiliary switch both realize ZVS turn-on and ZCS turn-off, and the freewheeling diode realizes ZVS turn-off, so that all switching devices realize full-soft-switching.

[0020] The first end of the input filter capacitor C0 is connected with the positive pole of the input voltage Vin, the first end of the main switch tube S1 and the first end of the auxiliary resonant switch tube S1a, and the second end of the input filter capacitor C0 is connected with the negative pole of the input voltage Vin, the negative pole of the output voltage Vout, the second end of the freewheeling diode D1 and the second end of the output filter capacitor C1.

[0021] The first end of the main switch tube S1 is connected with the positive pole of the input voltage Vin, the first end of the auxiliary resonant switch tube S1a and the first end of the input filter capacitor C0, and the second end of the main switch tube S1 is connected with the first end of the output filter inductor L1 and the first end of the resonant inductor Lr1. The main switch tube S1 is IGBT, IGCT or MOSFET.

[0022] The first end of the auxiliary resonant switch tube S1a is connected with the positive pole of the input voltage Vin, the first end of the main switch tube S1 and the first end of the input filter capacitor C0, and the second end of the auxiliary resonant switch tube S1a is connected with the first end of the resonant capacitor Cr1. The auxiliary resonant switch tube S1a is IGBT, IGCT or MOSFET.

[0023] The first end of the resonant capacitor Cr1 is connected with the second end of the auxiliary resonant switch tube S1a, and the second end of the resonant capacitor Cr1 is connected with the second end of the resonant inductor Lr1 and the first end of the freewheeling diode D1. The resonant capacitor Cr1 is a non-polarity capacitor.

[0024] The first end of the resonant inductor Lr1 is connected with the second end of the main switch tube S1 and the first end of the output filter inductor L1, and the second end of the resonant inductor Lr1 is connected with the second end of the resonant capacitor Cr1 and the first end of the freewheeling diode D1.

[0025] The first end of the freewheeling diode D1 is connected with the second end of the resonance capacitor Cr1 and the second end of the resonance inductor Lr1, and the second end of the freewheeling diode D1 is connected with the negative pole of the input voltage Vin, the negative pole of the output voltage Vout, the second end of the input filter capacitor C0 and the second end of the output filter capacitor C1.

[0026] The first end of the output filter inductor L1 is connected with the second end of the main switch S1 and the first end of the resonance inductor Lr1, and the second end of the output filter inductor L1 is connected with the first end of the output filter capacitor C1 and the positive pole of the output voltage Vout.

[0027] The first end of the output filter capacitor C1 is connected with the positive pole of the output voltage Vout and the second end of the output filter inductor L1, and the second end of the output filter capacitor C1 is connected with the negative pole of the input voltage Vin, the negative pole of the output voltage Vout, the second end of the freewheeling diode D1 and the second end of the input filter capacitor C0. The input filter capacitor C0 and the output filter capacitor C1 are electrolytic capacitors, film capacitors or super capacitors with polarity.

[0028] The positive terminal of the input voltage Vin and the negative terminal of the input voltage Vin are respectively connected with the positive pole and the negative pole of a direct current power grid or an energy storage element, and the positive terminal of the output voltage Vout and the negative terminal of the output voltage Vout are respectively connected with the positive pole and the negative pole of an energy storage element or a direct current power grid.

[0029] In the embodiment, the control method of the auxiliary resonance full-soft switching FSS-BUCK direct current converter is as follows.

[0030] Before the main switch S1 is turned on, the converter is in a freewheeling mode, and the current flows through the freewheeling diode D1 and the output filter inductor L1 to the output voltage; when the main switch S1 is turned on, the main switch S1 realizes ZCS turn-on due to the existence of the resonance inductor Lr1; at the same time, the freewheeling diode D1 can realize reverse ZVS turn-off due to the existence of the resonance capacitor Cr1.

[0031] After a certain time Δt1, the current flowing through the auxiliary resonance switch S1a is negative, at which time ZVS turn-off of the auxiliary resonance switch S1a can be realized, and after the resonance of the resonance inductor Lr1 and the resonance capacitor Cr1 ends, the converter is in a freewheeling mode.

[0032] After a certain time, the auxiliary resonance switch S1a is driven to be turned on, and the resonance inductor Lr1 and the resonance capacitor Cr1 start to resonate reversely, and the auxiliary resonance switch S1a can realize ZCS turn-on due to the existence of the resonance inductor Lr1.

[0033] When a certain time Δt2, the current flowing through the main switch tube S1 is negative, the ZVS turn-off of the main switch tube S1 can be realized, so that the turn-on loss and turn-off loss of the main switch tube S1 and the auxiliary resonant switch tube S1a are all zero, and the reverse recovery loss of the freewheeling diode D1 is zero.

[0034] In the embodiment, the specific working principle of the auxiliary resonant full-soft switching FSS-BUCK direct current converter is as follows. The working mode diagram of each working mode is as shown in the figure. Figures 3-12

[0035] Working mode 0: Before t0, the circuit is in the freewheeling stage, the current flows through the freewheeling diode D1 and the output filter inductor L1, and then flows back to the output side. Although the auxiliary resonant switch tube S1a is in the on state in this mode, the main switch tube S1 is in the off state, so the auxiliary resonant circuit is in the off state and no current flows through it.

[0036] Working mode 1: At t0, the main switch tube S1 is turned on, and due to the series resonant inductor Lr1, the main switch tube S1 is ZCS turned on. The freewheeling diode D1 current and the resonant inductor Lr1 current in the freewheeling circuit gradually decrease from I L to 0. Since the freewheeling diode D1 is in the forward conducting state during this mode, the resonant inductor Lr1 voltage is still clamped at the DC bus voltage, and the resonant capacitor Cr1 voltage remains at the DC bus voltage during this mode. At the same time, the main switch tube S1 current starts to gradually increase from 0 to the output filter inductor current I L .

[0037] The duration of this mode is , wherein L r is the inductance value of the resonant inductor Lr1; V in is the input side voltage value. During this mode, the main switch tube S1 current , and during this mode, the freewheeling diode D1 current .

[0038] Working mode 2: At t1, the freewheeling diode D1 current decreases to zero and naturally turns off. At this time, the main switch tube current is I L , the current on the resonant inductor Lr1 decreases to zero, and the voltage on the resonant capacitor Cr1 is left positive and right negative.

[0039] ​From t1 moment by the main switch S1, auxiliary resonant switch S1a, resonant capacitor Cr1, resonant inductor Lr1 constitute the resonant circuit resonates, resonant capacitor Cr1 voltage drop, resonant inductor Lr1 and auxiliary resonant switch S1a current starts from zero reverse increase. Main switch current from I L Start to increase.

[0040] To t2 moment, the resonance has experienced 1 / 4 resonance period, the main switch S1 current reaches the maximum value, auxiliary resonant switch S1a and resonant inductor Lr1 current reaches the negative maximum value, resonant capacitor Cr1 current reaches the maximum value, resonant capacitor Cr1 voltage decreases to zero.

[0041] In engineering, ignore the switch voltage drop, auxiliary resonant circuit resistance and other factors, the resonant circuit resonant frequency is , the resonant period is , the resonant angular frequency , the equivalent resonant impedance of the resonant circuit is , the modal duration is . At t2 moment, the negative maximum value of auxiliary resonant switch S1a and resonant inductor Lr1 current is .

[0042] Working mode 3: in t2~t3 time, by the main switch S1, auxiliary resonant switch S1a, resonant capacitor Cr1, resonant inductor Lr1 constitute the resonant circuit continues to resonate. Resonant capacitor Cr1 voltage from zero reverse charging, resonant capacitor Cr1 current gradually decreases from the maximum positive value, until t3 moment decreases to zero. Auxiliary resonant switch S1a and resonant inductor Lr1 current gradually decreases from the negative maximum value to zero. The current of main switch S1 gradually decreases from the maximum positive value to the current I L .

[0043] The modal duration is t 23 = t 12 , the modal end moment t 3 - , the reverse voltage of freewheeling diode D1 reaches the maximum value, about V D1max =2 V in .

[0044] Working mode 1~working mode 3, equivalent to the main switch of ordinary BUCK topology open process. The main idea of this topology is to realize the energy of the hard open process through the resonant circuit, the ZCS open of the main switch and the ZVS off of the auxiliary resonant switch.

[0045] In the time t1-t3 of the working mode 2 and the working mode 3, the ZVS turn-off of the auxiliary resonant switch S1a can be realized. That is, after the main switch S1 is turned on, the overlap turn-on time of the main switch S1 and the auxiliary resonant switch S1a should satisfy the following formula: 0 < Δt < t1-t3 t 1 < t 3 - t 1 .

[0046] Working mode 4: After the time t3, the voltage of the resonant capacitor Cr1 reaches the maximum reverse value V in , the resonant current of the resonant circuit is zero, the auxiliary resonant switch S1a blocks the resonant circuit, and the resonance stops. The current of the main switch S1 is equal to the current of the output filter inductor L1 I L , and the circuit enters the forward conduction energy transmission stage. During this working mode, the auxiliary resonant switch S1a bears the reverse voltage equal to the voltage of the resonant capacitor Cr1 V in . The reverse voltage of the freewheeling diode D1 is approximately equal to the input voltage V in . The voltage and current of the resonant inductor Lr1 are both zero.

[0047] Working mode 5: At the time t4, the auxiliary resonant switch S1a is turned on, and the resonant circuit composed of the main switch S1, the auxiliary resonant switch S1a, the resonant capacitor Cr1 and the resonant inductor Lr1 starts reverse resonance. The current of the main switch S1 gradually decreases. The current of the auxiliary resonant switch S1a and the resonant inductor Lr1 gradually increases from zero, realizing the ZCS turn-on of the auxiliary resonant switch S1a. The resonant capacitor Cr1 starts resonant discharge, and the current gradually increases in reverse from zero, and the voltage gradually decreases.

[0048] Until the time t5, the current of the main switch S1 decreases to zero from I L , and the current of the auxiliary resonant switch S1a increases to I L . Among them, the currents of the auxiliary resonant switch S1a and the resonant capacitor Cr1 change according to the formula . Then the time t4-t5 lasts .

[0049] Working mode 6: In the time t5-t6, the resonant circuit composed of the main switch S1, the auxiliary resonant switch S1a, the resonant capacitor Cr1 and the resonant inductor Lr1 continues reverse resonance.

[0050] At time t5, the current of the main switch S1 decreases to zero and then begins to increase in the opposite direction. The currents of the auxiliary resonant switch S1a, the resonant capacitor Cr1, and the resonant inductor Lr1 continue to increase according to the resonance law until they resonate to 1 / 4 of the resonant period at time t6.

[0051] The duration of working mode 6 is Part 2 of the formula The ZVS turn-off angle of the main switch S1 is defined as .

[0052] The total duration of working mode 5 and working mode 6 is .

[0053] At time t6, the currents in the auxiliary resonant switch S1a, resonant capacitor Cr1, and resonant inductor Lr1 reach their maximum values. .

[0054] At time t6, the current of the main switch S1 reaches its negative maximum value. .

[0055] Operating Mode 7: At time t6, the resonant circuit consisting of the main switch S1, the auxiliary resonant switch S1a, the resonant capacitor Cr1, and the resonant inductor Lr1 reaches 1 / 4 of its resonant cycle. The current of the main switch S1 reaches its negative maximum value. The currents of the auxiliary resonant switch S1a and the resonant inductor Lr1 reach their positive maximum values. The current of the resonant capacitor Cr1 reaches its negative maximum value, and its voltage is zero.

[0056] Starting from time t6, the currents in the auxiliary resonant switch S1a and the resonant inductor Lr1 gradually decrease from their positive maximum values. The current in the resonant capacitor Cr1 starts to rise from its negative maximum value, and the voltage increases negatively from zero.

[0057] During the time intervals t5 to t7 of modes 6 and 7, the main switch S1 can be turned off via ZVS.

[0058] At time t7, the current in the main switch S1 resonates to zero again.

[0059] The duration of working mode 7 is equal to the duration of working mode 6. .

[0060] At time t7, the current in the auxiliary resonant switch S1a, resonant capacitor Cr1, and resonant inductor Lr1 reaches I L .

[0061] Operating Mode 8: At time t7, the current of the main switch S1 resonates to zero. Since the main switch S1 has been turned off, the resonant circuit is broken, and the resonance stops. At this time, the currents of the auxiliary resonant switch S1a, the resonant inductor Lr1, and the resonant capacitor Cr1 are equal to the current of the output filter inductor L1.I L Starting from time t7, the voltage across the resonant capacitor Cr1 begins to reverse and maintain a constant current. I L As the capacitor Cr1 charges, the voltage across it increases linearly to the input voltage. V in .

[0062] This invention introduces an auxiliary resonant commutator switch, a resonant inductor, and a resonant capacitor to form a resonant circuit with the main switch to assist commutation. This achieves ZVS turn-off and ZCS turn-on for the main switch, ZVS turn-off and ZCS turn-on for the auxiliary resonant switch, and ZVS turn-off for the freewheeling diode. All power electronic devices achieve soft switching.

[0063] In this invention, the auxiliary resonant commutator switch operates only for a certain period before and after the main switch is turned on and off, further improving the efficiency of the topology and the flatness of the efficiency curve across the entire voltage and power range. The main loss of this topology is only the conduction loss, providing a novel solution for overcoming efficiency limits.

[0064] In this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or particular data points described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or particular data points described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0065] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An auxiliary resonant fully soft-switching FSS-BUCK DC-DC converter, characterized in that: The system includes an input filter capacitor C0, a main switch S1, an auxiliary resonant switch S1a, a resonant capacitor Cr1, an output filter inductor L1, a resonant inductor Lr1, a freewheeling diode D1, and an output filter capacitor C1. The first terminal of the input filter capacitor C0 is connected to the positive terminal of the input voltage Vin and the first terminals of the main switch S1 and the auxiliary resonant switch S1a. The second terminal of the input filter capacitor C0 is connected to the negative terminal of the input voltage Vin, the negative terminal of the output voltage Vout, and the second terminal of the freewheeling diode D1 and the output filter capacitor C1. The first terminal of the main switch S1... The first terminal of the main switch S1 is connected to the positive terminal of the input voltage Vin, the first terminal of the auxiliary resonant switch S1a, and the first terminal of the input filter capacitor C0. The second terminal of the main switch S1 is connected to the first terminal of the output filter inductor L1 and the first terminal of the resonant inductor Lr1. The first terminal of the auxiliary resonant switch S1a is connected to the positive terminal of the input voltage Vin, the first terminal of the main switch S1, and the first terminal of the input filter capacitor C0. The second terminal of the auxiliary resonant switch S1a is connected to the first terminal of the resonant capacitor Cr1. The first terminal of the resonant capacitor Cr1 is connected to the second terminal of the auxiliary resonant switch S1a. The second terminal of the resonant capacitor Cr1 is connected to the first terminal of the resonant capacitor Cr1. The two terminals are connected to the second terminal of the resonant inductor Lr1 and the first terminal of the freewheeling diode D1; the first terminal of the resonant inductor Lr1 is connected to the second terminal of the main switch S1 and the first terminal of the output filter inductor L1, and the second terminal of the resonant inductor Lr1 is connected to the second terminal of the resonant capacitor Cr1 and the first terminal of the freewheeling diode D1; the first terminal of the freewheeling diode D1 is connected to the second terminal of the resonant capacitor Cr1 and the second terminal of the resonant inductor Lr1, and the second terminal of the freewheeling diode D1 is connected to the negative terminal of the input voltage Vin, the negative terminal of the output voltage Vout, the input filter capacitor C0, and the output filter capacitor C0. The second terminal of capacitor C1 is connected to the following: the first terminal of the output filter inductor L1 is connected to the second terminal of the main switch S1 and the first terminal of the resonant inductor Lr1; the second terminal of the output filter inductor L1 is connected to the first terminal of the output filter capacitor C1 and the positive terminal of the output voltage Vout; the first terminal of the output filter capacitor C1 is connected to the positive terminal of the output voltage Vout and the second terminal of the output filter inductor L1; the second terminal of the output filter capacitor C1 is connected to the negative terminal of the input voltage Vin, the negative terminal of the output voltage Vout, the freewheeling diode D1, and the second terminal of the input filter capacitor C0.

2. The auxiliary resonant fully soft-switching FSS-BUCK DC-DC converter according to claim 1, characterized in that, The main switch S1 is an IGBT, IGCT, or MOSFET; the auxiliary resonant switch S1a is an IGBT, IGCT, or MOSFET; the resonant capacitor Cr1 is a non-polarized capacitor; and the input filter capacitor C0 and the output filter capacitor C1 are polarized electrolytic capacitors, film capacitors, or supercapacitors.

3. A control method for the assisted resonant fully soft-switching FSS-BUCK DC-DC converter as described in claim 1, characterized in that the steps are as follows: include: Before the main switch S1 is turned on, the converter is in freewheeling mode, and the current flows through the freewheeling diode D1 and the output filter inductor L1 to the output. When the main switch S1 is turned on, ZCS is achieved, and the freewheeling diode D1 achieves reverse ZVS turn-off. After time Δt1, the current flowing through the auxiliary resonant switch S1a is negative, achieving ZVS turn-off of the auxiliary resonant switch S1a. After the resonance of the resonant inductor Lr1 and the resonant capacitor Cr1 ends, the converter is in freewheeling mode. Then, the auxiliary resonant switch S1a is driven to turn on, and the resonant inductor Lr1 and the resonant capacitor Cr1 begin to resonate in reverse, achieving ZCS turn-on of the auxiliary resonant switch S1a. After time Δt2, the current flowing through the main switch S1 is negative, achieving ZVS turn-off of the main switch S1. The turn-on loss and turn-off loss of the main switch S1 and the auxiliary resonant switch S1a are both zero, and the reverse recovery loss of the freewheeling diode D1 is zero.

4. The control method for an assisted resonant fully soft-switching FSS-BUCK DC-DC converter according to claim 3, characterized in that, The specific steps are as follows: Before time t0, the circuit is in the freewheeling phase, and the current flows back to the output side after passing through the freewheeling diode D1 and the output filter inductor L1. At time t0, the main switch S1 is turned on, and the main switch S1 is ZCS turned on. The current of the freewheeling diode D1 and the current of the resonant inductor Lr1 flow from... I L As the current gradually decreases to 0, the freewheeling diode D1 is in the forward conducting state, the voltage of the resonant inductor Lr1 is clamped at the DC bus voltage, the voltage of the resonant capacitor Cr1 remains at the DC bus voltage, and the current of the main switch S1 gradually increases from 0 to the current of the output filter inductor. I L ; At time t1, the current in the freewheeling diode D1 decreases to zero and it turns off naturally. At this time, the current in the main switch is... I L The current in the resonant inductor Lr1 decreases to zero, and the voltage across the resonant capacitor Cr1 is positive on the left and negative on the right. The resonant circuit consisting of the main switch S1, the auxiliary resonant switch S1a, the resonant capacitor Cr1, and the resonant inductor Lr1 begins to resonate. The voltage across the resonant capacitor Cr1 decreases, and the currents in the resonant inductor Lr1 and the auxiliary resonant switch S1a begin to increase in the reverse direction from zero. The current in the main switch starts to increase from zero. I L Start to increase; During the time interval t2 to t3, the resonant circuit continues to resonate. The voltage of the resonant capacitor Cr1 starts to reverse charge from zero, and the current of the resonant capacitor Cr1 gradually decreases from its positive maximum value until it decreases to zero at time t3. The currents of the auxiliary resonant switch S1a and the resonant inductor Lr1 gradually decrease from their negative maximum values ​​to zero, and the current of the main switch S1 gradually decreases from its positive maximum value to zero. I L , After time t3, the voltage across the resonant capacitor Cr1 reaches its reverse maximum value. V in The resonant current of the resonant circuit is zero. The auxiliary resonant switch S1a blocks the resonant circuit from resonating and stops the resonance. The current of the main switch S1 is equal to the current of the output filter inductor L1. I L When the circuit enters the forward conduction stage, the auxiliary resonant switch S1a experiences a reverse voltage equal to the voltage across the resonant capacitor Cr1. V in The reverse voltage of the freewheeling diode D1 is equal to the input voltage. V in The voltage and current of the resonant inductor Lr1 are both zero; At time t4, the auxiliary resonant switch S1a is turned on, the resonant circuit begins to resonate in reverse, the current of the main switch S1 gradually decreases, and the current of the auxiliary resonant switch S1a and the resonant inductor Lr1 gradually increases from zero, realizing the ZCS turn-on of the auxiliary resonant switch S1a. The resonant capacitor Cr1 begins to resonate and discharge, the current gradually increases in reverse from zero, and the voltage gradually decreases. Until time t5, the current of the main switch S1 from I L The current drops to zero, and the current in the auxiliary resonant switch S1a rises to... I L ; During the time interval t5 to t6, the resonant circuit continues to resonate in the reverse direction. The current of the main switch S1 decreases to zero and then begins to increase in the reverse direction. The currents of the auxiliary resonant switch S1a, the resonant capacitor Cr1, and the resonant inductor Lr1 continue to increase according to the resonant law. Starting from time t6, the current of the auxiliary resonant switch S1a and the resonant inductor Lr1 gradually decreases from their positive maximum values, the current of the resonant capacitor Cr1 starts to rise from its negative maximum value, and the voltage increases negatively from zero. Starting from time t7, the voltage across the resonant capacitor Cr1 begins to reverse and maintain a constant current. I L As the capacitor Cr1 charges, the voltage across it increases linearly to the input voltage. V in .

5. The control method for an assisted resonant fully soft-switching FSS-BUCK DC-DC converter according to claim 4, characterized in that, At time t5, the currents in the auxiliary resonant switch S1a, resonant capacitor Cr1, and resonant inductor Lr1 continue to increase according to the resonance law until they resonate to 1 / 4 of the resonant period at time t6.

6. The control method for an assisted resonant fully soft-switching FSS-BUCK DC-DC converter according to claim 5, characterized in that, At time t6, the resonant circuit reaches 1 / 4 of its resonant cycle. The current of the main switch S1 reaches its negative maximum value, the current of the auxiliary resonant switch S1a and the resonant inductor Lr1 reaches its positive maximum value, the current of the resonant capacitor Cr1 reaches its negative maximum value, and the voltage is zero.

7. The control method for an assisted resonant fully soft-switching FSS-BUCK DC-DC converter according to claim 6, characterized in that, At time t7, the current of the main switch S1 resonates to zero again, and the currents of the auxiliary resonant switch S1a, resonant capacitor Cr1, and resonant inductor Lr1 reach... I L .

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