Non-resonant soft switching converter topology

Abstract

The invention discloses a non-resonant soft switching converter topology, and belongs to the technical field of converters. Comprising a switching tube, a filter inductor, an auxiliary inductor, a clamping capacitor, a filter capacitor, a clamping diode, a fly-wheel diode, a first junction capacitor and a second junction capacitor. According to the invention, the soft switch-on and soft switch-off of the switch tube, the clamping diode and the freewheel diode can be realized only through one auxiliary inductor. Compared with a PFM control mode of a traditional resonant soft switching converter, the converter provided by the invention can be suitable for a PWM control mode, an active switching device does not need to be added, and the EMI problem of a system is optimized while the electric energy conversion efficiency of the converter is improved. And meanwhile, the switch stress of the power switch tube and the diode does not change along with the change of the input voltage, so that the device cost is saved in a high input voltage occasion.

Description

Technical Field

[0001] The invention relates to the technical field of converters, and in particular to a non-resonant soft-switching converter topology. Background Art

[0002] Photovoltaic power generation is the most representative industry in the field of renewable energy power generation. It has the advantages of both distributed and centralized types. Among them, indoor DC power supply systems and photovoltaic storage and charging DC microgrids are the most typical representatives, and the buck converter is an important part of the photovoltaic system. For traditional buck converters, the voltage stress of the power switch tube and diode will increase with the increase of input voltage, which means higher device cost in high-voltage situations. In addition, the power switch tube has the characteristic of hard opening, which will cause higher losses in high-frequency situations and reduce the efficiency of power conversion. Summary of the invention

[0003] In view of the defects of the prior art, the present invention provides a non-resonant soft-switching converter topology, which aims to solve the high hard-switching losses of traditional buck converters and the EMI problem caused by hard switching, thereby improving the power conversion efficiency of the power devices of the entire system and the system stability.

[0004] In order to achieve the above object, the present invention provides a non-resonant soft switching converter topology, including: a switch tube S, a filter inductor L 1 , auxiliary inductor L 2 , Clamping capacitor C 1 、Filter capacitor C 2 , clamping diode D 1 , freewheeling diode D 2 , the first junction capacitance C D1 , the second junction capacitance C D2 ;

[0005] The drain of the switch tube S is connected to the DC input power supply V in The positive electrode is connected to the filter inductor L 1 and auxiliary inductor L 2 The first end of the auxiliary inductor L 2 The second end of the clamp capacitor C 1 The first end of the clamping capacitor C 1 The second end of the clamping diode D 1 The anode and first junction capacitance C D1 The second end, the second junction capacitance C D2 The first end of the freewheeling diode D 2 The cathode of the clamping diode D 1 The cathode and first junction capacitance C D1 The first end of the filter inductor L 1 The second end and filter capacitor C2 The first end is connected to form the output voltage V o The positive terminal of the filter capacitor C 2 The second end is connected to the DC input power supply V in The negative pole of the freewheeling diode D 2 The anode and second junction capacitance C D2 The second end is connected to form the output voltage V o The negative terminal.

[0006] Furthermore, the DC input power supply V in In sequence with the switch tube S, filter inductor L 1 、Filter capacitor C 2 Connected in series to form a first closed loop;

[0007] The DC input power supply V in In sequence with the switch tube S, filter inductor L 1 , the output load R is connected in series to form a second closed loop;

[0008] The DC input power supply V in In sequence with the switch tube S, auxiliary inductor L 2 , Clamping capacitor C 1 , clamping diode D 1 、Filter capacitor C 2 Connect in series to form a third closed loop;

[0009] The DC input power supply V in In sequence with the switch tube S, auxiliary inductor L 2 , Clamping capacitor C 1 , clamping diode D 1 , the output load R is connected in series to form a fourth closed loop;

[0010] The clamping capacitor C 1 In sequence with the auxiliary inductor L 2 , filter inductor L 1 、Filter capacitor C 2 , freewheeling diode D 2 Connected in series to form a first freewheeling loop;

[0011] The clamping capacitor C 1 In sequence with the auxiliary inductor L 2 , filter inductor L 1 , output load R, freewheeling diode D 2 Connected in series to form a second freewheeling circuit;

[0012] The filter capacitor C 2 It is connected in series with the output load R to form a third freewheeling loop.

[0013] Furthermore, the first junction capacitance CD1 The second junction capacitance C D2 The capacitance values ​​are equal;

[0014] The auxiliary inductor L 2 satisfy:

[0015]

[0016] D r =2i Lf (1-D) / i La_peak

[0017]

[0018] Where: V o is the output voltage, P o is the output power, C D is the first junction capacitance C D1 The capacitance value, D is the conduction duty cycle of the switch tube S, i Lf is the filter inductor L 1 Average current, T s is the switching period of the switch tube S.

[0019] Furthermore, the non-resonant soft-switching converter has five operating modes in one cycle.

[0020] Furthermore, the five modes are specifically:

[0021] t 1 ~t 2 Always working in mode 1: t 1 Before the moment, the switch tube S is turned off, the non-resonant soft-switching converter is in the freewheeling state, and the auxiliary inductor L 2 The current i L2 The direction is opposite to the reference direction; t 1 At this moment, the switch tube S is turned on, and due to the auxiliary inductor L 2 The existence of the switch tube S current i S Linear increase, so the switch tube S is turned on with zero current, and the filter inductor L 1 The current i L1 Linear increase, auxiliary inductance L 2 The current i L2 Linear decrease; t 2 At this moment, the auxiliary inductor L 2 The current i L2 Drops to 0, then the freewheeling diode D 2 Zero current shutdown;

[0022] t 2 ~t 3Always working in mode 2: the switch tube S is turned on, the first junction capacitor C D1 discharge, the second junction capacitance C D2 charging, the auxiliary inductor L 2 The current i L2 The filter inductance L increases linearly with the reference direction. 1 The current i L1 linearly increases, the clamping capacitor C 1 Charging; 3 At this moment, the first junction capacitance C D1 Discharge to 0, the second junction capacitance C D2 Charge to V o ; Therefore, in Mode 2, the clamping diode D 1 Zero current switching;

[0023] t 3 ~t 4 Always working in mode 3: the switch tube S, clamping diode D 1 Turn on, the freewheeling diode D 2 The switch tube S and the auxiliary inductor L remain unchanged when the reverse voltage is applied. 2 , clamping diode D 1 The current decreases linearly, the filter inductor L 1 The current rises linearly, the clamping capacitor C 1 Charging; 4 At this moment, the switch tube S 1 The current i S and filter inductor L 1 The current i L1 equal, and the auxiliary inductor L 2 The current i L2 , clamping diode D 1 The current i D1 drops to 0, at which point the clamping diode D 1 Zero current shutdown;

[0024] t 4 ~t 5 Always working in mode 4: the switch tube S is turned off, and the current i S linearly decreases; due to the auxiliary inductance L 2 The existence of auxiliary inductance i L2 It rises linearly and in the opposite direction to the reference direction, i S with i L2 The change of both is the same; the filter inductor L 1 The current decreases linearly, the clamping capacitor C 1 Discharge, the first junction capacitance C D1 Charging, the second junction capacitance CD2 Discharge; t 5 Moment, C D1 The capacitor voltage is the output voltage V o , C D2 The capacitor voltage drops to 0; therefore, in mode 4, the freewheeling diode D 2 Zero current switching;

[0025] t 5 ~t 6 Always working in mode 5: the switch tube S is turned off, the clamping diode D 1 The first junction capacitance C D1 The voltage remains unchanged and fully enters the freewheeling state. The filter inductor L 1 The current decreases linearly, the clamping capacitor C 1 Discharge, to t 6 moment, entering the next switching cycle.

[0026] Furthermore, the clamping capacitor C 1 、Filter capacitor C 2 All use film capacitors.

[0027] Furthermore, the switch tube S is a metal oxide semiconductor field effect transistor or an insulated gate bipolar transistor.

[0028] Furthermore, the first junction capacitance C D1 For external parallel capacitor or clamping diode D 1 Its own junction capacitance; the second junction capacitance C D2 For external parallel capacitor or freewheeling diode D 2 Its own junction capacitance.

[0029] Beneficial effects of the present invention:

[0030] 1. The present invention uses only one auxiliary inductor L 2 , the soft opening and soft closing of the switch tube, clamping diode and freewheeling diode can be realized. Compared with the PFM control method of the traditional resonant soft switching converter, the converter provided by the present invention can be applied to the PWM control method. While improving the power conversion efficiency of the converter, the EMI problem of the system is optimized.

[0031] 2. The power switch tube and diode switch stress of the converter provided by the present invention do not change with the input voltage change, thus saving device costs in high input voltage situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the topology of a non-resonant soft switching converter according to an embodiment of the present invention.

[0033] Figure 2Schematic diagram of the circuit of Mode 1 to Mode 5 of the non-resonant soft switching converter in steady state according to an embodiment of the present invention.

[0034] Figure 3 Schematic diagram of main waveforms of the non-resonant soft-switching converter in steady state according to an embodiment of the present invention.

[0035] Where: V GS Represents the gate-source voltage of the switch tube S, V DS Represents the drain-source voltage of the switching tube S. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The described embodiments should not be regarded as limiting the present application, and all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] In the following description, reference is made to “some embodiments”, “one or more embodiments”, which describe a subset of all possible embodiments, but it can be understood that “some embodiments”, “one or more embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0038] In the following description, the terms "first\second\third" are only used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described here can be implemented in an order other than that shown or described.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0040] like Figure 1 As shown, the embodiment of the present invention provides a non-resonant soft switching converter topology, including: a DC input power supply V in , switch tube S, filter inductor L 1 , auxiliary inductor L 2 , Clamping capacitor C 1 、Filter capacitor C 2 , clamping diode D 1 , freewheeling diode D 2 , the first junction capacitance C D1 , the second junction capacitance C D2 .

[0041] In the embodiment of the present invention, the DC input power supply V in It can provide DC power to all power supply devices, such as photovoltaic cells, car batteries, fuel cells, etc.

[0042] In this topology, the drain of the switch tube S is connected to the DC input power supply V in The positive electrode is connected to the filter inductor L 1 and auxiliary inductor L 2 The first end of the auxiliary inductor L 2 The second end of the clamp capacitor C 1 The first end of the clamping capacitor C 1 The second end of the clamping diode D 1 The anode and first junction capacitance C D1 The second end, the second junction capacitance C D2 The first end of the freewheeling diode D 2 The cathode connection of the clamping diode D 1 The cathode and first junction capacitance C D1 The first end of the filter inductor L 1 The second end and filter capacitor C 2 The first end is connected to form the output voltage V o The positive terminal of the filter capacitor C 2 The second end is connected to the DC input power supply V in The negative pole of the freewheeling diode D 2 The anode and second junction capacitance C D2 The second end is connected to form the output voltage V o The negative terminal.

[0043] DC input power supply V in The switch tube S, the filter inductor L are sequentially connected to the 1 、Filter capacitor C 2 Connected in series to form the first closed loop.

[0044] DC input power supply V in In sequence with the switch tube S, filter inductor L 1 , the output load R is connected in series to form a second closed loop.

[0045] DC input power supply V in In sequence with the switch tube S, auxiliary inductor L 2 , Clamping capacitor C 1 , clamping diode D 1 、Filter capacitor C 2 Connected in series to form a third closed loop.

[0046] DC input power supply V in Sequentially with the first switch, the auxiliary inductor L 2, Clamping capacitor C 1 , clamping diode D 1 , the output load R is connected in series to form a fourth closed loop.

[0047] Clamping capacitor C 1 In sequence with the auxiliary inductor L 2 , filter inductor L 1 、Filter capacitor C 2 , freewheeling diode D 2 Connected in series to form the first freewheeling circuit.

[0048] Clamping capacitor C 1 In sequence with the auxiliary inductor L 2 , filter inductor L 1 , output load R, freewheeling diode D 2 Connected in series to form a second freewheeling circuit.

[0049] Filter capacitor C 2 It is connected in series with the output load R to form a third freewheeling loop.

[0050] In this embodiment, the filter inductor L is considered 1 The inductance value is large enough, and the current ripple can be ignored, so it can be regarded as a constant current source. 2 Since the inductor current in the branch cannot change suddenly, the current cannot change suddenly after the switch tube S is turned on. Therefore, the switch tube S and the clamping diode D can be realized. 1 , freewheeling diode D 2 Zero current switching.

[0051] In the embodiment of the present invention, the first junction capacitor C D1 Capacitance, second junction capacitance C D2 The capacitance is equal. The first junction capacitance C D1 It can be an external parallel capacitor or a clamping diode D 1 Its own junction capacitance; the second junction capacitance C D2 It can be an external parallel capacitor or a freewheeling diode D 2 Its own junction capacitance.

[0052] Auxiliary inductor L 2 satisfy:

[0053]

[0054] D r =2i Lf (1-D) / i La_peak

[0055]

[0056] Where: V o is the output voltage, Po is the output power, C D is the first junction capacitance C D1 (C D1 =C D2 =C D ) is the capacitance value, D is the conduction duty cycle of the switch tube S, i Lf is the filter inductor L 1 Average current, T s is the switching period of the switch tube S.

[0057] When the above formula is satisfied, the auxiliary inductor L 2 , clamping diode D 1 The peak current generated by the branch is greater than the clamping diode D 1 The peak current can achieve zero current shutdown of the clamping diode and the freewheeling diode.

[0058] In order to more clearly explain the embodiment of the present invention, the principle of the present invention is described in detail below. When the non-resonant soft switching converter works in CCM mode, there are 5 working modes, such as Figure 2 As shown, the main working waveform is as follows Figure 3 The specific description is as follows:

[0059] Because the clamping capacitor C 1 、Filter capacitor C 2 The capacitance value of is relatively large. At this time, the voltage ripple is ignored and the clamping capacitor C 1 、Filter capacitor C 2 The voltage is constant, and non-polar film capacitors can be used in practice. The switch tube S is a metal oxide semiconductor field effect transistor (MOSFET) tube or an insulated gate bipolar transistor (IGBT). The filter inductor L 1 The inductance of is large enough, and the current ripple can be ignored, so it can be regarded as a constant current source. 1 , freewheeling diode D 2 Considering that the junction capacitance is equal, C D1 =C D2 =C D .

[0060] There are five modes in total:

[0061] t 1 ~t 2 Always working in mode 1: t 1 Before the moment, the switch tube S is turned off, the non-resonant soft-switching converter is in the freewheeling state, and the auxiliary inductor L 2 The current i L2 The direction is opposite to the reference direction. 1At this moment, the switch tube S is turned on, and due to the auxiliary inductor L 2 The existence of the switch tube S current i S Increases linearly, so the switch tube S is turned on with zero current. Filter inductor L 1 The current i L1 Linear increase, auxiliary inductance L 2 The current i L2 Linear decrease; t 2 At this moment, the auxiliary inductor L 2 The current i L2 Drops to 0, then the freewheeling diode D 2 Zero current shutdown.

[0062] t 2 ~t 3 Always working in mode 2: switch tube S is turned on, the first junction capacitor C D1 Discharge, the second junction capacitance C D2 Charging, auxiliary inductor L 2 The current i L2 The filter inductance L increases linearly in the same direction as the reference. 1 The current i L1 Linear rise, clamping capacitor C 1 Charging. 3 At this moment, the first junction capacitance C D1 Discharge to 0, the second junction capacitance C D2 Charge to V o , so due to the existence of junction capacitance, in mode 2, the clamping diode D 1 Zero current switching.

[0063] t 3 ~t 4 Always working in mode 3: switch tube S, clamping diode D 1 Turn on, freewheeling diode D 2 The reverse voltage remains unchanged; the switch tube S and auxiliary inductor L 2 , clamping diode D 1 The current decreases linearly, and the filter inductance L 1 The current rises linearly, the clamping capacitor C 1 Charging. 4 At this moment, the current i of the switch tube S S and filter inductor L 1 The current i L1 equal, and the auxiliary inductor L 2 The current i L2 , clamping diode D 1 The current i D1 drops to 0, at which point the clamping diode D 1 Zero current shutdown.

[0064] t 4 ~t 5 Always working in mode 4: the switch tube S is turned off, and the current i S Linear decrease; due to the auxiliary inductance L 2 The existence of auxiliary inductance i L2 It rises linearly and in the opposite direction to the reference direction, i S with i L2 The changes of both are the same; the filter inductance L 1 The current decreases linearly, the clamping capacitor C 1 Discharge, the first junction capacitance C D1 Charging, the second junction capacitance C D2 Discharge. 5 Moment, C D1 The capacitor voltage is the output voltage V o , C D2 The capacitor voltage drops to 0. Therefore, due to the existence of the junction capacitance, in mode 4, the freewheeling diode D 2 Zero current switching;

[0065] t 5 ~t 6 Always working in mode 5: switch tube S is turned off, clamping diode D 1 The first junction capacitance C D1 The voltage remains unchanged and fully enters the freewheeling state. The filter inductor L 1 The current decreases linearly, the clamping capacitor C 1 Discharge, to t 6 moment, entering the next switching cycle.

[0066] The embodiment of the present invention utilizes an auxiliary inductor L 2 , realizing the soft start of the switch tube S and the soft shut-off and soft start of all diodes. In addition, it solves the disadvantage that the voltage stress of the power device of the traditional buck converter changes with the input voltage change, and finally improves the stability and efficiency of the whole system.

[0067] The above is only an embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement and improvement made within the spirit and scope of the present application are included in the protection scope of the present application.

Claims

1. A non-resonant soft switching converter topology, characterized in that: include: Switch tube S, filter inductor L1, auxiliary inductor L2, clamp capacitor C1, filter capacitor C2, clamp diode D1, freewheeling diode D2, first junction capacitor C D1 , the second junction capacitance C D2 ; The drain of the switch tube S is connected to the DC input power supply V in The positive electrode of the clamping diode D1 is connected, and the source electrode thereof is connected to the first end of the filter inductor L1 and the auxiliary inductor L2; the second end of the auxiliary inductor L2 is connected to the first end of the clamping capacitor C1; the second end of the clamping capacitor C1 is connected to the anode of the clamping diode D1, the first junction capacitor C D1 The second end, the second junction capacitance C D2 The first end of the clamp diode D1 is connected to the cathode of the freewheeling diode D2; the cathode of the clamp diode D1 is connected to the first junction capacitor C D1 The first end of the filter inductor L1, the second end of the filter capacitor C2 and the first end of the filter inductor L1 are connected to form an output voltage V o The positive terminal of the filter capacitor C2 is connected to the DC input power supply V in The negative electrode, the anode of the freewheeling diode D2, and the second junction capacitor C D2 The second end is connected to form the output voltage V o The negative terminal.

2. The non-resonant soft switching converter topology according to claim 1, characterized in that: The DC input power supply V in It is connected in series with the switch tube S, the filter inductor L1, and the filter capacitor C2 in sequence to form a first closed loop; The DC input power supply V in It is connected in series with the switch tube S, the filter inductor L1, and the output load R in sequence to form a second closed loop; The DC input power supply V in The third closed loop is sequentially connected in series with the switch tube S, the auxiliary inductor L2, the clamping capacitor C1, the clamping diode D1, and the filter capacitor C2; The DC input power supply V in The fourth closed loop is sequentially connected in series with the switch tube S, the auxiliary inductor L2, the clamping capacitor C1, the clamping diode D1, and the output load R; The clamping capacitor C1 is sequentially connected in series with the auxiliary inductor L2, the filter inductor L1, the filter capacitor C2, and the freewheeling diode D2 to form a first freewheeling loop; The clamping capacitor C1 is sequentially connected in series with the auxiliary inductor L2, the filter inductor L1, the output load R, and the freewheeling diode D2 to form a second freewheeling loop; The filter capacitor C2 is connected in series with the output load R to form a third freewheeling loop.

3. The non-resonant soft switching converter topology according to claim 1, characterized in that: The first junction capacitance C D1 The second junction capacitance C D2 The capacitance values ​​are equal; The auxiliary inductor L2 satisfies: D r =2i Lf (1-D) / i La_peak Where: V o is the output voltage, P o is the output power, C D is the first junction capacitance C D1 The capacitance value, D is the conduction duty cycle of the switch tube S, i Lf is the average current of the filter inductor L1, T s is the switching period of the switch tube S.

4. The non-resonant soft switching converter topology according to claim 1, characterized in that: The non-resonant soft-switching converter has five operating modes in one cycle.

5. The non-resonant soft switching converter topology according to claim 4, characterized in that: The five modes are specifically: At t1-t2, the converter works in mode 1: before t1, the switch tube S is turned off, the non-resonant soft-switching converter is in the freewheeling state, and the current i of the auxiliary inductor L2 is L2 The direction is opposite to the reference direction; at time t1, the switch tube S is turned on. Due to the existence of the auxiliary inductor L2, the current i S Linear increase, so the switch tube S is turned on with zero current, and the current i of the filter inductor L1 L1 The current i of the auxiliary inductor L2 rises linearly. L2 Linearly decreases; at time t2, the current i of the auxiliary inductor L2 L2 Drops to 0, at which time the freewheeling diode D2 is turned off with zero current; From t2 to t3, the switch S is turned on and the first junction capacitor C D1 discharge, the second junction capacitance C D2 Charging, the auxiliary inductor L2 current i L2 The current i of the filter inductor L1 increases linearly with the reference direction. L1 Linearly rising, the clamping capacitor C1 is charged; at t3, the first junction capacitor C D1 Discharge to 0, the second junction capacitance C D2 Charge to V o ; Therefore, in the process of mode 2, the clamping diode D1 is turned on with zero current; From t3 to t4, the system works in mode 3: the switch tube S and the clamping diode D1 are turned on, and the freewheeling diode D2 remains unchanged under the reverse voltage; the currents of the switch tube S, the auxiliary inductor L2, and the clamping diode D1 decrease linearly, the current of the filter inductor L1 increases linearly, and the clamping capacitor C1 is charged; at t4, the current i S The current i of the filter inductor L1 L1 equal, and the current i of the auxiliary inductor L2 L2 , the current i of the clamping diode D1 D1 Drops to 0, at which time the clamping diode D1 is turned off with zero current; At t4-t5, the switch S is turned off and the current i S Linearly decreases; due to the existence of the auxiliary inductor L2, the auxiliary inductor i L2 It rises linearly and in the opposite direction to the reference direction, i S with i L2 The amount of change in both is the same; The current of the filter inductor L1 decreases linearly, the clamping capacitor C1 discharges, and the first junction capacitor C D1 Charging, the second junction capacitance C D2 Discharge; at t5, C D1 The capacitor voltage is the output voltage V o , C D2 The capacitor voltage drops to 0; therefore, in mode 4, the freewheeling diode D2 is turned on with zero current; At t5-t6, the switch S is turned off, and the first junction capacitance C of the clamping diode D1 is D1 The voltage remains unchanged and completely enters the freewheeling state. The current of the filter inductor L1 decreases linearly, and the clamping capacitor C1 discharges. At time t6, the next switching cycle begins.

6. The non-resonant soft switching converter topology according to claim 1, characterized in that: The clamping capacitor C1 and the filter capacitor C2 are both film capacitors.

7. The non-resonant soft switching converter topology according to claim 1, characterized in that: The switch tube S is a metal oxide semiconductor field effect transistor or an insulated gate bipolar transistor.

8. The non-resonant soft switching converter topology according to claim 1, characterized in that: The first junction capacitance C D1 is the external parallel capacitor or the junction capacitance of the clamping diode D1 itself; the second junction capacitance C D2 It is the external parallel capacitor or the junction capacitance of the freewheeling diode D2 itself.

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