CN103546038B - A kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation - Google Patents

Abstract

The invention discloses a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation, including DC source V_in, the first inverter bridge leg and the second inverter bridge leg, auxiliary induction, auxiliary transformer, auxiliary capacitor, isolating transformer and current rectifying and wave filtering circuit.The present invention adopts phase-shift control mode, owing to adding the auxiliary network of auxiliary induction, auxiliary transformer and auxiliary capacitor composition, the primary current of this changer commutates in advance under the voltage source effect that auxiliary transformer provides, the vibration of secondary rectifier output voltage obtains good suppression, and in wider loading range, realize the ZVT of primary side switch pipe, being absent from the loss of secondary dutycycle, filter inductance current ripples is little, reduces output noise.

Description

A kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation

Technical field

The present invention relates to a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation.

Background technology

Phase shifting control soft switch full bridge converter is owing to combining PWM switch and the advantage of mode of resonance switch, in switching process, harmonic technology is utilized to realize no-voltage/Zero Current Switch, switching process is returned to common PWM state after terminating, it is little that it has been provided simultaneously with switching loss, on-state loss is low and the advantage such as PWM pressure regulation, therefore in powerful DC converting occasion favored widely.

And there is reverse-recovery problems because of secondary commutation diode in traditional phase shifting control full-bridge converter of zero-voltage switch, the resonance of former limit leakage inductance and commutation diode parasitic capacitance makes secondary rectifier output voltage there is serious peak voltage and vibration, thus significantly improves voltage stress and the output voltage noise of rectifier tube.In order to solve the problems referred to above, Chinese scholars has done a large amount of research work.Secondary adopts RCD absorbing circuit, and as shown in Figure 1, the effect of its suppression peak voltage and vibration is better, but absorbing circuit power dissipation problems is serious, reduces the overall efficiency of changer.Secondary adopts the mode of active or lossless passive-clamp to suppress secondary-side voltage oscillation, inhibition is obvious, and solve power dissipation problems well, but this type of method all needs bigger clamping capacitance, easily cause the current spike of primary side, additionally the mode of active-clamp needs to introduce extra switch, and this just need to increase extra control circuit and drive circuit, adds cost and the complexity of system.The method of former limit string pulsactor can substantially increase the soft-switching range of lagging leg, duty-cycle loss is little, and the change of current of former limit terminate after the equivalent series inductance value I of main power transfer path effectively suppress due to voltage spikes and the vibration of secondary, but pulsactor works in dual quadrant, its core volume is big, heating is serious, is unfavorable for the integrated of changer.RichardRedl et al. adds two clamp diodes and a bigger resonant inductance on former limit, as shown in Figure 2, widen soft-switching range, and greatly suppress due to voltage spikes and the vibration of commutation diode, but the duty-cycle loss that the addition of bigger resonant inductance causes is serious, and can not the voltage oscillation that causes of eliminating transformer leakage inductance, and the working condition of clamp diode is often poor, reduces changer functional reliability and efficiency thereof.

Summary of the invention

Present invention aims to the technological deficiency existing for above-mentioned changer and a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation is provided, based on the advanced change of current thought in former limit, change of current voltage source is introduced by auxiliary transformer, auxiliary coupling inductance provides the energy realizing primary side switch pipe Sofe Switch, significantly widen converter soft switch scope, the vibration of secondary rectifier output voltage obtains good suppression, and secondary is absent from the loss of dutycycle, filter inductance current ripples reduces simultaneously, reduces conduction loss and output noise.

The present invention for achieving the above object, adopts the following technical scheme that

A kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation of the present invention, first inverter bridge leg identical including DC source, structure and the second inverter bridge leg, isolating transformer and current rectifying and wave filtering circuit；nullWherein each inverter bridge leg includes two switching tubes、Two individual diodes and two parasitic capacitances，The drain electrode of the first switching tube respectively with the first body diode negative electrode、One end of first parasitic capacitance connects and composes the positive input terminal of inverter bridge leg，The source electrode of the first switching tube respectively with the first body diode anode、The other end of the first parasitic capacitance、The drain electrode of second switch pipe、Second body diode negative electrode、One end of second parasitic capacitance connects and composes the outfan of inverter bridge leg，The source electrode of second switch pipe respectively with the second body diode anode、The other end of the second parasitic capacitance connects and composes the negative input end of inverter bridge leg，The positive pole of DC source connects the first inverter bridge leg and the positive input terminal of the second inverter bridge leg respectively，The negative pole of DC source connects the first inverter bridge leg and the negative input end of the second inverter bridge leg respectively，The input of the output termination current rectifying and wave filtering circuit of isolating transformer vice-side winding，It is characterized in that:

Also include the auxiliary network being made up of auxiliary induction, auxiliary transformer and auxiliary capacitor；Wherein auxiliary induction is coupling inductance, the outfan of one termination the first brachium pontis of primary side winding, one end of another termination coupling inductance vice-side winding different name with it of primary side winding constitutes the midpoint of coupling inductance, and another of vice-side winding terminates the outfan of the second inverter bridge leg.The midpoint of one termination auxiliary coupling inductance of auxiliary transformer primary side winding, one end of another termination auxiliary capacitor, the negative pole of another termination DC source of auxiliary capacitor, the one end connecing auxiliary capacitor in auxiliary transformer vice-side winding with auxiliary transformer primary side winding is the outfan that the one of Same Name of Ends terminates the first inverter bridge leg, one end of another termination isolating transformer primary side winding of auxiliary transformer vice-side winding, another of isolating transformer primary side winding terminates the outfan of the second inverter bridge leg.

The present invention discloses a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation, it can effectively suppress spike and the vibration that secondary commutating voltage exists, and realize the ZVT of switching tube at wide loading range.Its technical characteristics is compared with original technology, based on the advanced change of current thought in former limit, utilize the vice-side winding voltage of described auxiliary transformer as change of current voltage source, namely primary current realizes commutation in the circulation stage, secondary is absent from the loss of dutycycle, and the energy being stored in described auxiliary coupling inductance can realize the ZVT of primary side switch pipe in wide scope.Introducing due to auxiliary transformer so that isolating transformer is provided energy by auxiliary capacitor to secondary in traditional zero state stage, and filter inductance current ripples is little, reduces conduction loss and the output noise of filter circuit, and the performance of changer is improved.

Accompanying drawing explanation

Accompanying drawing 1 is the phase-shifted full-bridge converter electrical block diagram that secondary adds RCD absorbing circuit.

Accompanying drawing 2 is the phase-shifted full-bridge converter electrical block diagram that former limit adds clamp diode.

Accompanying drawing 3 is a kind of soft switching full-bridge direct-current converter electrical block diagram suppressing secondary-side voltage oscillation of the present invention.

Accompanying drawing 4 be the present invention a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation in auxiliary coupling inductance equivalence after electrical block diagram.

Accompanying drawing 5 is a kind of soft switching full-bridge direct-current converter key operation waveforms schematic diagram suppressing secondary-side voltage oscillation of the present invention.

Accompanying drawing 6～accompanying drawing 11 is each switch mode schematic diagram that the present invention a kind of suppresses the soft switching full-bridge direct-current converter of secondary-side voltage oscillation within half working cycle.

Accompanying drawing 12 is a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation and the conventional full bridge converter secondary rectifier output voltage v of the present invention_rectWith output voltage V_oSimplify waveform diagram.

Primary symbols title in above-mentioned accompanying drawing: V_in, supply voltage.Q₁～Q₄, power switch pipe.C₁～C₄, parasitic capacitance.D₁～D₄, body diode.T_ra, auxiliary transformer.C_a, auxiliary capacitor.L_a, auxiliary coupling inductance.T_r, isolating transformer.L_k, isolating transformer leakage inductance.L_r, series resonance inductor.L_m, magnetizing inductance.D_R1、D_R2, output commutation diode.C_DR1、C_DR2, output commutation diode junction capacity.D_c、C_c、R_c, respectively the diode in RCD absorbing circuit, Absorption Capacitance, absorption resistance.D_a1、D_a2, clamp diode.v_rect, rectifier output voltage.L_f, filter inductance.C_f, filter capacitor.R_Ld, load.V_a, output voltage.v_AB, A and B point-to-point transmission voltage.v_OP, auxiliary transformer primary side winding O and P point-to-point transmission voltage.v_AC, auxiliary transformer vice-side winding A and C point-to-point transmission voltage.

Detailed description of the invention

Below in conjunction with accompanying drawing, the technical scheme of invention is described in detail:

Shown in accompanying drawing 3 is a kind of soft switching full-bridge direct-current converter electrical block diagram suppressing secondary-side voltage oscillation.It is made up of 1, two inverter bridge legs 2 and 3 of DC source, isolating transformer 4, auxiliary coupling inductance 5, auxiliary transformer 6, auxiliary capacitor 7 and current rectifying and wave filtering circuit 8.Q₁～Q₄It is four power switch pipes, D₁～D₄It is switching tube Q respectively₁～Q₄Body diode, C₁～C₄It is switching tube Q respectively₁～Q₄Parasitic capacitance, T_raIt is auxiliary transformer, L_aIt is auxiliary coupling inductance, C_aIt is auxiliary capacitor, T_rIt is isolating transformer, L_kIt is the leakage inductance of isolating transformer, D_R1、D_R2It is output commutation diode, C_DR1、C_DR2It is commutation diode D respectively_R1、D_R2Junction capacity, L_fIt is output inductor, C_fIt is output filter capacitor, R_LdFor load.Wherein L_aFor turn ratio n_LaThe coupling inductance of=1, and coupling inductance is similar to an ideal transformer with specific magnetizing inductance, for the ease of analyzing, accompanying drawing 3 can be equivalent to the circuit shown in accompanying drawing 4.This changer adopts phase shifting control, switching tube Q₄And Q₂Lag behind switching tube Q respectively₁And Q₃One phase place, claims switching tube Q₁And Q₃First inverter bridge leg of composition is leading-bridge, switching tube Q₂And Q₄Second inverter bridge leg of composition is then lagging leg.Auxiliary capacitor C_aVoltage be input voltage V_inHalf, i.e. v_Ca=V_in/ 2, can be considered a voltage source.

For easy analysis, below with the main circuit structure after the equivalence shown in accompanying drawing 4, describe the specific works principle of the present invention in conjunction with accompanying drawing 6～accompanying drawing 11.There are 12 kinds of switch mode by known one switch periods of whole changer of accompanying drawing 5, are [t respectively₀-t₁]、[t₁-t₂]、[t₂-t₃]、[t₃-t₄]、[t₄-t₅]、[t₅-t₆]、[t₆-t₇]、[t₇-t₈]、[t₈-t₉]、[t₉-t₁₀]、[t₁₀-t₁₁]、[t₁₁-t₁₂], wherein, [t₀-t₆] for first half cycle, [t₆-t₁₂] for the later half cycle.Below the working condition of each switch mode is made a concrete analysis of.

Before analysis, first make the following assumptions: 1. all switching tubes and diode are ideal component；2. filter inductance is sufficiently large, and therefore the output of isolating transformer secondary can be equivalent to constant-current source, and auxiliary capacitor is sufficiently large, can be considered constant pressure source, and voltage is V_in/ 2, all inductance, electric capacity are ideal element；③C₁=C₃=C_lead, C₂=C₄=C_lag.1. switch mode 1 [t₀-t₁] [corresponding to accompanying drawing 6]

Q₁And Q₄Conducting, Q₂And Q₃Cut-off, primary current is similar to constant, i_p=I_o/ n (wherein n is the former secondary turn ratio of isolating transformer), v_AB=V_in, upper commutation diode D_R1Flow through whole load current, D_R2Cut-off, former limit powering load.Owing to auxiliary capacitor voltage stabilization is at V_in/ 2, the former vice-side winding voltage of auxiliary transformer is zero.Auxiliary coupling inductance equivalence magnetizing inductance L_inBoth end voltage is V_in, exciting current i_mLinear rise, simultaneously advanced arm auxiliary current i₁With lagging leg auxiliary current i₂Also linear rise.i_m(t)、i₁(t)、i₂(t) and i_aT () is represented by

$i_m\left(t\right)=\frac{V_{\mathrm{in}}}{{L:}_m}(t-t_0)-i_m\left(t_0\right)---\left(1\right)$

$i_1\left(t\right)=i_m\left(t\right)+\frac{i_a}{2}---\left(2\right)$

$i_2\left(t\right)=i_m\left(t\right)-\frac{i_a}{2}---\left(3\right)$

i_a(t)=i_p(t)(4)

Wherein, L_mFor assisting the equivalent magnetizing inductance of coupling inductance, i_m(t₀) for assisting coupling inductance exciting current at t₀The value in moment.

And by formula (1) it can be seen that within the whole working cycle coupling inductance exciting current amplitude can approximate representation be

$I_m=\frac{1}{2}\frac{V_{\mathrm{in}}}{L_m}D\frac{T_s}{2}---\left(5\right)$

The energy being stored in auxiliary coupling inductance is represented by

$E_m=\frac{1}{2}{L}_m{I_m}^2=\frac{1}{32}\frac{{V_m}^2{T_s}^2}{L_m}{D}^2---\left(6\right)$

2. switch mode 2 [t₁-t₂] [corresponding to accompanying drawing 7]

t₁Moment turns off Q₁, electric current (i_p+i₁) from Q₁In transfer to C₁And C₃In branch road.In this period, i_pAnd i₁Give C simultaneously₁Charging, to C₃Electric discharge, v_ABBy V_inIt is gradually reduced, v_rectAlso decline accordingly.Owing to auxiliary coupling inductance and filter inductance are all relatively big, (i_p+i₁) can be considered constant-current source, thus v_AB、v_rectAll linearly change.Until t₂Moment, v_rectFirst dropping to zero, secondary two commutation diode simultaneously turns on, and the former vice-side winding voltage of isolating transformer is clamped at zero.This stage v_ABWith v_rectRelation is represented by:

v_AB=v_AC+n_vrect(7)

Wherein v_ACVoltage for auxiliary transformer vice-side winding two ends.

It can be seen that the impact of auxiliary transformer, v_ABCan't with v_rectDrop to zero simultaneously.And v_ACCan be expressed as again:

$v_{\mathrm{AC}}=v_{\mathrm{OP}}=v_{\mathrm{Ca}}-\frac{v_{\mathrm{AB}}}{2}---\left(8\right)$

Can be released by formula (7) (8), work as v_rectWhen dropping to zero, i.e. t₂Moment, v_AC(t₂)=V_in/3。

3. switch mode 3 [t₂-t₃] [corresponding to accompanying drawing 8]

Leakage inductance L_kStart to bear negative voltage, primary current i_pStart to reduce.C₃At i_pAnd advanced arm auxiliary current i₁Effect under continue electric discharge, v_ABContinue to decline, v_OPContinue to increase.At t₃Moment, C₃Voltage drop to zero, Q₃Anti-paralleled diode D₃Naturally conducting.

4. switch mode 4 [t₃-t₄] [corresponding to accompanying drawing 9]

D₃After conducting, Q can be opened₃, now Q₃Open-minded for no-voltage.Q₁And Q₃Drive the Dead Time t between signal_d(lead)> t₁₃.A point current potential drops to zero, so v_AB=0, the auxiliary former vice-side winding voltage of coupling inductance is zero, v_OpStable at V_in/2.Voltage (the i.e. v of auxiliary transformer vice-side winding coupling_AC) reversely it is added in leakage inductance L_kTwo ends, primary current continues to decline and reverse.Owing to forcing the voltage V of the former limit change of current_in/ 2 is relatively big, and former limit commutation time is very of short duration.And compared with conventional full bridge converter, the moment of this changer primary current commutation is in advance.

5. switch mode 5 [t₄-t₅] [corresponding to accompanying drawing 10]

At t₄Moment primary current reversely rises to-I_o/ n, former limit change of current success, D_R1Turn off, D_R2Flow through whole load current.Now due to v_ABBeing still zero, auxiliary transformer vice-side winding voltage is still V_in/2.Leakage inductance L_kWith rectifier tube junction capacity C_DR1Constitute resonant tank, secondary rectifier output voltage v_rectT () is represented by

$v_{\mathrm{rect}}\left(t\right)=\frac{1}{n}{v}_{\mathrm{Ct}}\left(t\right)=\frac{1}{n}[\frac{V_{\mathrm{in}}}{2}-\frac{V_{\mathrm{in}}}{2}\cos \left({\mathrm{\ω}}_0(t-t_4)\right)]---\left(9\right)$

Wherein:C_tFor junction capacity C_DR1The equivalent capacity on conversion extremely former limit.

As can be seen from the above equation, there is V in commutation diode_inThe crest voltage of/n, but this does not improve the voltage stress of commutation diode.Energy is still transmitted to secondary in this stage former limit, and the power of transmission is 1/2 under normal active.The energy of now former limit transmission is not provided by DC source, but by auxiliary capacitor C_aRelease and can maintain.

6. switch mode 6 [t₅-t₆] [corresponding to accompanying drawing 11]

t₅Moment, Q₄Turn off, due to now primary current reversely, lagging leg auxiliary current i₂To compensate primary current on the one hand, to provide C on the one hand₂And C₄Charging and discharging currents.Similarly, i₂Can be similar to and regard constant-current source as, thus C₄Both end voltage approximately linear rises, C_DR1Also at lagging leg auxiliary current i₂Effect under continue charging, v_rectContinue to rise.Ignore the impact of leakage inductance, v_Q4(t)、v_rect(t) and v_ACT () is represented by

$v_{Q4}\left(t\right)=\frac{i_p\left(t_5\right)+i_2\left(t_5\right)}{2C_{\mathrm{oss}}+C_t}(t-t_5)---\left(10\right)$

$v_{\mathrm{rect}}\left(t\right)=\frac{v_{Q4}\left(t\right)+v_{\mathrm{AC}}\left(t\right)}{n}---\left(11\right)$

$v_{\mathrm{AC}}\left(t\right)=v_{\mathrm{OP}}\left(t\right)=v_{\mathrm{Ca}}-\frac{v_{Q4}\left(t\right)}{2}---\left(12\right)$

V is found out by above formula_rectApproximately linear rises, it does not have vibration.Until t₆In the moment, B point current potential rises to input voltage V_in, D₂Naturally conducting, now opens Q₂Its ZVT can be realized.v_rectRise to V_in/ n, energy is transmitted to secondary in former limit, and circuit enters lower half working cycle [t₆-t₁₂], its working condition is similar to above-mentioned half period [t₀-t₆], repeat no more here.

In order to illustrate that in the present invention, output inductor current ripples is less than traditional phase-shifted full-bridge converter, accompanying drawing 12 gives the present invention and rectifier output voltage v in conventional full bridge converter_rectWith output voltage V_oSimplification oscillogram.

Assuming that the full-bridge converter that conventional full bridge converter and the present invention propose has identical Input and Output Indexes, and both main transformer turn ratioes are identical.Thus having:

$V_o=\frac{V_{\mathrm{in}}}{n}{D}_1=\frac{V_{\mathrm{in}}}{n}{D}_2+\frac{V_{\mathrm{in}}}{2n}(1-D_2)---\left(13\right)$

Filter inductance current ripples Δ I in conventional full bridge converter_o1With changer filter inductance current ripples Δ I in the present invention_o2Can be expressed as follows:

$\mathrm{\Δ}{I}_{o1}=\frac{\frac{V_{\mathrm{in}}}{n}-V_o}{L_f}{D}_1\frac{T_s}{2}---\left(14\right)$

$\mathrm{\Δ}{I}_{o2}=\frac{\frac{V_{\mathrm{in}}}{n}-V_o}{L_f}{D}_2\frac{T_s}{2}---\left(15\right)$

In conjunction with (13) (14) (15), can release:

$\frac{\mathrm{\Δ}{I}_{o2}}{\mathrm{\Δ}{I}_{o1}}=2-\frac{1}{D_1}---\left(16\right)$

Ignore the loss of secondary dutycycle in conventional full bridge converter, it is assumed that the full duty cycle of secondary rectifier output voltage, i.e. D when input voltage is minimum₁=1, two kinds of changer filter inductance current ripples are equal.But the increase D along with input voltage₁Correspondingly reduce, D when input voltage is maximum₁Minimum, Δ I_o2/ΔI_o1Minimum, the advantage that now in the present invention, changer filter inductance current ripples reduces is also the most obvious.

From the description above it is known that a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation advantage with following several respects of proposing of the present invention:

1) utilizing the voltage on auxiliary transformer to realize the advanced change of current in former limit, after the change of current, secondary commutating voltage spike obtains good suppression, reduces voltage stress and conduction loss, the problem simultaneously solving duty-cycle loss of output commutation diode.

2) energy of auxiliary coupling inductance storage has widened the soft-switching range of primary side switch pipe.

3) reduce output inductor current ripples, reduce conduction loss and output noise, improve the reliability of system, alleviate EMI.

Claims (2)

1. suppress a soft switching full-bridge direct-current converter for secondary-side voltage oscillation, first inverter bridge leg (2) identical including DC source (1), structure and the second inverter bridge leg (3), isolating transformer (4) and current rectifying and wave filtering circuit (8)；nullWherein each inverter bridge leg includes two switching tubes、Two individual diodes and two parasitic capacitances，The drain electrode of the first switching tube respectively with the first body diode negative electrode、One end of first parasitic capacitance connects and composes the positive input terminal of inverter bridge leg，The source electrode of the first switching tube respectively with the first body diode anode、The other end of the first parasitic capacitance、The drain electrode of second switch pipe、Second body diode negative electrode、One end of second parasitic capacitance connects and composes the outfan of inverter bridge leg，The source electrode of second switch pipe respectively with the second body diode anode、The other end of the second parasitic capacitance connects and composes the negative input end of inverter bridge leg，The positive pole of DC source (1) connects the first inverter bridge leg (2) and the positive input terminal of the second inverter bridge leg (3) respectively，The negative pole of DC source (1) connects the first inverter bridge leg (2) and the negative input end of the second inverter bridge leg (3) respectively，The input of output termination current rectifying and wave filtering circuit (8) of isolating transformer (4) vice-side winding，It is characterized in that:

Also include the auxiliary network being made up of auxiliary induction (5), auxiliary transformer (6) and auxiliary capacitor (7)；Wherein auxiliary induction is coupling inductance, the outfan of one termination the first inverter bridge leg of primary side winding, one end of another termination auxiliary induction vice-side winding different name with it of primary side winding constitutes the midpoint of auxiliary induction, another of vice-side winding terminates the outfan of the second inverter bridge leg, the midpoint of one termination auxiliary induction of auxiliary transformer (6) primary side winding, one end of another termination auxiliary capacitor, the negative pole of another termination DC source (1) of auxiliary capacitor, the one end connecing auxiliary capacitor in auxiliary transformer vice-side winding with auxiliary transformer primary side winding is the outfan that the one of Same Name of Ends terminates the first inverter bridge leg, one end of another termination isolating transformer primary side winding of auxiliary transformer vice-side winding, another of isolating transformer primary side winding terminates the outfan of the second inverter bridge leg.

2. a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation as claimed in claim 1, it is characterised in that the former vice-side winding turn ratio of described auxiliary transformer is 1: 1, the former vice-side winding turn ratio of described auxiliary induction is 1: 1.