CN2917083Y - Normal/reverse excitation combined DC/DC isolated transformer - Google Patents

Abstract

The utility model relates to a forward-flyback combined DC/DC isolated converter, main circuit of which is composed of a switch tube (VQ), a transformer (T), a rectifying and filtering circuit (1) and a buffer network (2). The transformer (T) is provided with a primary winding (N <P>). Each set of secondary winding comprises a forward winding (N <s1>) and a flyback winding (N <s2>). Each output terminal of the rectifying and filtering circuit (1) is composed of rectifying diodes (VD <1> and VD <2>), buffer diodes (VD <r1> and VD <r2>), a buffer capacitor (C <r>), a filtering capacitor (C <0>) and a filtering inductance (L<0>). Single switch tube of the converter can realize dual-end switching without magnetic-core reset circuit, thus improving power density, lowering rectifying diode voltage stress, reducing output current ripple, decreasing size of filtering inductance and speeding up dynamic response. The utility model has advantages of simple structure, easy control, high efficiency, and can be widely applied to isolating switch power source.

Description

Normal shock-anti-sharp combination type DC/DC isolated converter

One, technical field

The utility model relates to a kind of normal shock-anti-sharp combination type DC/DC isolated converter, is a kind of direct-current switch power supply technology, belongs to electric and electronic technical field.

Two, background technology

At present, the single-ended off-line type DC/DC converter that is applied to Switching Power Supply has two kinds: the one, and anti exciting converter, the 2nd, forward converter.Anti exciting converter has simply efficiently, is easy to advantages such as parallel connection; But exist rectifier diode current stress and output voltage ripple bigger, the deficiency that voltage and load regulation are low.So generally only be applied to small-power (below 150W) and than the occasion of high output voltage.Advantages such as forward converter has that power output is big, current stress is little, low ripple and high regulation; But need magnetic core to reset, rectifier diode voltage stress height, little loaded work piece is unfavorable.So generally be applied to low pressure, big electric current, occasion that power is bigger.In addition, these two kinds of monofocal converters also have a common shortcoming, are exactly that magnetic core utilance low power density is less, and promptly transformer is only exported energy to load under a kind of mode of switching tube conducting or shutoff.

The purpose of this utility model is, overcomes above-mentioned the deficiencies in the prior art, and a kind of normal shock-instead swash combination type DC/DC isolated converter is provided, and adopts single switching tube to realize double-end type output, i.e. secondary winding normal shock-instead swash alternation, raising power density; Have the advantage of normal shock and anti exciting converter concurrently, rectifier diode voltage and current stress is all less, and ripple reduces, and dynamic responding speed improves, and does not need the magnetic core reset circuit.

Realization of the present utility model is according to following principle.

1, by basic pwm converter---the Buck-Boost converter is deduced, and increases isolation link again, then draws a kind of converter of extensive use---anti exciting converter (Flyback converter), as shown in Figure 1.Switching tube VQ is opposite with fast diode VD work phase place.VD blocking-up when the VQ conducting, the former limit of transformer winding N _pElectric current increases and energy storage; VD conducting when VQ turn-offs, the transformer energy storage is through secondary winding N _sOutput.Capacitor C plays the energy storage filter action.

2, combine with single-ended isolating transformer by Buck (voltage-dropping type) converter, can draw another kind of typical converter---forward converter (Forward converter), as shown in Figure 2.This is the circuit that a former limit and secondary are worked simultaneously, i.e. VQ and VD ₁The work phase place is identical, L and VD ₂Play the afterflow effect.Because former limit winding N _pWhat pass through is unidirectional pulsating current, and the forward converter circuit of a practicality must be taken measures, and magnetic core of transformer is resetted, thereby obtains a collection of distortion circuit (can referring to the books of Switching Power Supply aspect).Reset schemes commonly used is to add the elementary winding N that resets _PrWith diode VD _r(see figure 2).

Three, summary of the invention

According to above-mentioned principle, the utility model is achieved in that

A kind of normal shock-instead swash combination type DC/DC isolated converter, as shown in Figure 3.Its main circuit is made of switching tube VQ, isolating transformer T, secondary commutation filter circuit (1) and elementary buffer network (2); Isolating transformer T has an elementary winding N _pWith one or more sets secondary winding, every cover secondary winding comprises a normal shock winding N _S1With an anti-sharp winding N _S2Secondary commutation filter circuit (1) can be one or more groups output, one or more sets secondary winding of corresponding transformer T; Every group of output is by rectifier diode (VD ₁, VD ₂), buffering diode (VD _R1, VD _R2), buffer capacitor (C _r), filter capacitor (C ₀), filter inductance (L ₀) constitute.Elementary buffer network (2) can be RCD network or LCD network.

The annexation of these each components and parts of converter is: the elementary winding N of isolating transformer T _pAn end connect DC power supply V _iPositive pole, N _pThe other end connect the drain electrode (or claiming collector electrode) of switching tube VQ; The source electrode of VQ (or claiming emitter) connects DC power supply V _iNegative pole.The normal shock winding N of isolating transformer T _S1An end swash winding N with anti- _S2Non-same polarity link to each other 2. N as lead-out terminal _S1Another termination rectifier diode VD ₁Anode, N _S2Another termination rectifier diode VD ₂Anode and buffering diode VD _R1Anode; Buffering diode VD _R1Negative electrode meet VD _R2Anode and the buffering capacitor C _rPositive pole, C _rNegative pole connect lead-out terminal 2.; Rectifier diode VD ₁, VD ₂Negative electrode and buffering diode VD _R2Negative electrode link to each other and meet filter inductance L ₀An end.Filter inductance L ₀Another termination filter capacitor C ₀Anodal and 1. as lead-out terminal, C ₀Negative pole connect lead-out terminal 2..1., 2. lead-out terminal organizes the link of output and load as this.

1, the main electric weight relational expression of this converter

1), output voltage V _oWith input voltage V _i, duty ratio D relation:

If anti-swash output and output inductor all works in continuous current mode, then normal shock, secondary output voltage V when anti-sharp _Sec1, V _Sec2And output voltage V _oBe respectively:

V _sec1＝V _i·n ₁-V _D (1)

${\mathrm{<figure-callout\; id="2"\; label="V\; sec"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\sec }=V_i\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\&CenterDot;\frac{D}{1-D}-V_D---\left(2\right)$

V _o＝V _sec1·D+V _sec2·(1-D)

＝(n ₁+n ₂)·D·V _i-V _D (3)

In the formula: V _Sec1, V _Sec2---be respectively normal shock, the secondary commutation output voltage when instead swashing;

V _o---output voltage;

Y _i---input voltage;

V _D---rectifier diode VD ₁, VD ₂Conduction voltage drop;

D---switching tube VQ conducting duty ratio;

n ₁, n ₂---be respectively the turn ratio of normal shock, anti-sharp winding and elementary winding.

As seen, this converter has the feature that the Buck type derives from the isolation double-end converter, output voltage V _oD is linear with duty ratio.

2), maximum conducting duty ratio D _MaxConstraints:

Definition normal shock, the anti-energy that swashs output than m are:

$m=\frac{P_{o1}}{P_{o2}}---\left(4\right)$

In the formula: P _O1, P _O2---be respectively normal shock, anti-sharp winding output energy.Then have when ignoring diode drop VD:

$m=\frac{P_{o1}}{P_{o2}}=\frac{{\mathrm{<figure-callout\; id="1"\; label="V\; sec"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\sec }\&CenterDot;\mathrm{<figure-callout\; id="2"\; label="D\; V\; sec"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">D</figure-callout>}}{V_{\sec }}\&ap;\frac{n_1}{n_2}---$ $\left(5\right)$

Solve by formula (3), (5):

${\mathrm{<figure-callout\; id="2"\; label="V\; sec"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\sec }=\frac{V_o}{(1-D)\&CenterDot;(1+m)}---\left(6\right)$

In order to reduce to flow through buffering diode VD when instead swashing _R1, VD _R2Electric current, then should make under the specified input voltage, the electric current rate of descent that instead swashs winding equals filter inductance L _oThe electric current rate of descent, that is:

$\frac{V_o-V_{\sec 2\left(e\right)}}{L_o}=\frac{V_{\sec 2\left(e\right)}+V_D}{L_{s2}}---\left(7\right)$

In the formula: L _S2---instead swash the inductance value of winding.Also should satisfy simultaneously: at maximum duty cycle D _MaxWhen (corresponding to minimum input voltage, maximum output current), instead swash output voltage and be not higher than output voltage V _o, promptly;

V _sec2(Max)≤V _o (8)

Solve maximum conducting duty ratio D by formula (6), (8) _MaxConstraints be:

$D_{\mathrm{Max}}\&le;\frac{m}{(1+m)}---\left(9\right)$

Generally speaking, desirable m=1～1.5.

3), the reverse voltage stress V of output rectifier diode _VD:

During normal shock output, rectifier diode VD ₂Reverse voltage stress V _VD2For:

V _VD2=(n ₁+ n ₂) V _iWhen (10) instead swashing output, rectifier diode VD ₁Reverse voltage stress V _VD1For:

$V_{\mathrm{<figure-callout\; id="1"\; label="VD"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">VD</figure-callout>}1}=({\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_1+n_2)\&CenterDot;V_i\&CenterDot;\frac{D}{1-D}---\left(11\right)$

So, output rectifier diode VD ₁, VD ₂Reverse voltage stress maximum V _{VD (Max)}For:

$V_{\mathrm{VD}\left(\mathrm{Max}\right)}=({\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_1+n_2)\&CenterDot;V_i\&CenterDot;\mathrm{MAX}[1,\frac{D}{1-D}]---\left(12\right)$

$=(V_o+V_D)\&CenterDot;\mathrm{MAX}$ $[\frac{1}{D},\frac{1}{1-D}]$

In the formula: MAX[... ... ]---maximum is wherein got in expression.

As seen, reverse voltage stress and the normal shock or the anti exciting converter of output rectifier diode suitable (the rectifier diode voltage stress of normal shock or anti exciting converter is (V _o+ V _D)/D) compared when adopting full-wave rectification with double-end converter such as bridge-type, and the rectifier diode voltage stress reduces approximately half.

4), the absolute value ET of the positive and negative voltagesecond product of output inductor _M:

Draw the absolute value ET of the positive and negative voltagesecond product of output inductor through derivation _MFor:

$E{T}_M=|V_o-{\mathrm{<figure-callout\; id="2"\; label="V\; sec"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">V</figure-callout>}}_{\sec }|\&CenterDot;(1-D)\&CenterDot;T_s$

$=|\frac{m}{1+m}-D|\&CenterDot;V_o\&CenterDot;T_s$

As seen, this normal shock-instead swashs the absolute value of the positive and negative voltagesecond product of output inductor of combination type converter (absolute value of the positive and negative voltagesecond product of output inductor of forward converter is (1-D) V much smaller than forward converter _oT _s).That is: normal shock-anti-sharp combination type converter can reduce the ripple of output current, voltage greatly, under the same ripple index, can reduce output inductor value and volume, improves dynamic responding speed.

2, the major parameter design procedure of this converter

1), determines that the energy of normal shock, anti-sharp output is than m and maximum conducting duty ratio D _Max

2), determine nominal duty cycles D _e

Switching tube conducting duty ratio when so-called nominal duty cycles is meant specified input, output voltage, nominal load.Can get D by formula (3) _eWith D _MaxThe pass be:

$D_e=\frac{V_{i\left(\min \right)}}{V_{i\left(e\right)}}\&CenterDot;D_{\mathrm{Max}}$

In the formula: V _{I (min)}---the minimum value of input voltage;

V _{I (e)}---the rated value of input voltage.

3), determine the turn ratio n of normal shock winding, anti-sharp winding and elementary winding ₁, n ₂

Solve by formula (3), (5):

$\left\{\begin{array}{cc}{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_2=\frac{V_o+V_D}{(1+m)\&CenterDot;D_e\&CenterDot;V_{i\left(e\right)}}& \\ {\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_1=m\&CenterDot;n_2& \end{array}\right.---\left(15\right)$

4), determine output inductor L _o

In order to work in continuous current mode, output inductor L _oShould satisfy following condition:

$\frac{(V_o-V_{\sec 2})\&CenterDot;(1-D)}{2L_o\&CenterDot;f_s}\&le;I_o=\frac{P_o}{V_o}---\left(16\right)$

That is:

$L_o\&GreaterEqual;\frac{{\mathrm{<figure-callout\; id="2"\; label="V\; o"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">V</figure-callout>}}_o^{}}{2P_o\&CenterDot;f_s}[\frac{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">m</figure-callout>}}{1+m}-D_{\min }]---\left(17\right)$

Desirable generally speaking:

$L_o=(1~2.5)\&CenterDot;\frac{V_o^2}{P_e\&CenterDot;f_s}[\frac{\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">m</figure-callout>}}{1+m}-D_{\min }]---\left(18\right)$

In the formula: P _o---power output;

P _e---rated output power;

D _Min---switching tube conducting duty ratio minimum value;

f _s---switching frequency.

5), determine the anti-inductance value L that swashs winding _S2

Solve by formula (6), (7):

$L_{s2}=\frac{1-\frac{V_D}{V_o}(1+m)\&CenterDot;(1-D_e)}{(1+m)\&CenterDot;(1-D_e)-1}\&CenterDot;L_o---\left(19\right)$

6), determine the inductance value L of elementary winding _pAnd number of turn N _p

L _p＝L _s2/n ₂ ² (20)

Because the exciting current of transformer is the flyback converter component in the elementary winding, and the normal shock current component does not influence magnetic flux.So the number of turn of elementary winding can be determined according to anti-sharp peak current.The peak I of the flyback converter component in the elementary winding _{P2 (M)}For:

$I_{p2(m)}=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\&CenterDot;I_{o\left(M\right)}\&CenterDot;(1-D_{\min })}{D_{\min }\&CenterDot;{\mathrm{\&eta;}}_2}+\frac{V_i\&CenterDot;D}{2_{L_P}\&CenterDot;f_s}$

$=\frac{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_2\&CenterDot;I_{o\left(M\right)}\&CenterDot;(1-D_{\min })}{D_{\min }\&CenterDot;{\mathrm{\&eta;}}_2}+\frac{V_o+V_D}{2({\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="Y20052013223200101.png"\; state="\{\{state\}\}">n</figure-callout>}}_1+n_2)\&CenterDot;L_p\&CenterDot;f_s}---\left(21\right)$

In the formula: I _{O (M)}---the load current maximum;

η ₂---the anti-efficient that swashs output.

The number of turn N of elementary winding then _pFor:

$N_p=\frac{L_p\&CenterDot;I_{P^2\left(M\right)}}{A_e\&CenterDot;B_M}---\left(22\right)$

In the formula: A _e---the net sectional area of magnetic core of transformer;

B _M---the maximum functional magnetic flux of magnetic core of transformer.

The utility model compared with prior art has following superiority:

1. single switching tube of this converter has promptly been realized double-end type isolation output, does not need the magnetic core reset circuit.Compare with normal shock or anti exciting converter, improve nearly one times of power density;

Compare when 2. double-end converters such as this converter and bridge-type adopt full-wave rectification, the voltage stress of rectifier diode reduces approximately half.

3. this converter can reduce the ripple of output current, voltage greatly; Under the same ripple index, can reduce output inductor value and volume, improve dynamic responding speed.

Four, description of drawings

Fig. 1 is the anti exciting converter circuit diagram;

Fig. 2 is the forward converter circuit diagram;

Fig. 3 is the main circuit diagram that normal shock-instead swashs combination type DC/DC isolated converter;

In Fig. 1, Vs---input power supply; VQ---switching tube; N _p, N _s---elementary winding and secondary (anti-sharp) winding of switch transformer; VD---rectifier diode; C---filter capacitor.

In Fig. 2, Vs---input power supply; VQ---switching tube; N _p, N _s---elementary winding and secondary (normal shock) winding of switch transformer; N _Pr---the winding that resets of switch transformer; VD ₁, VD ₂---rectifier diode; VDr---reset diode; L---filter inductance; C---filter capacitor.

In Fig. 3, VQ---switching tube; T---isolating transformer; N _p---the elementary winding of isolating transformer T; N _S1, N _S2---normal shock winding and the anti-sharp winding of isolating transformer T; VD ₁, VD ₂---rectifier diode; VD _R1, VD _R2---buffering diode; C _r---buffer capacitor; C _o---filter capacitor; L _o---filter inductance; 1---the secondary commutation filter circuit; 2---elementary buffer network, adopt the LCD network here.

Five, embodiment

With most preferred embodiment in detail the utility model is described in detail below in conjunction with accompanying drawing.

As shown in Figure 3, a kind of normal shock-instead swash combination type DC/DC isolated converter, its main circuit is made of switching tube (VQ), isolating transformer (T), secondary commutation filter circuit (1) and elementary buffer network (2); Isolating transformer (T) has an elementary winding (N _p) and a cover secondary winding, secondary winding comprises a normal shock winding (N _S1) and an anti-sharp winding (N _S2).Secondary commutation filter circuit (1) is by rectifier diode (VD ₁, VD ₂), buffering diode (VD _R1, VD _R2), buffer capacitor (C _r), filter capacitor (C _o), filter inductance (L _o) constitute.Elementary buffer network (2) adopts the LCD network.

The annexation of these each components and parts of converter is: the elementary winding (N of isolating transformer (T) _p) an end connect DC power supply (V _i) positive pole, (N _p) the other end connect the drain electrode (or claiming collector electrode) of switching tube (VQ); (VQ) source electrode (or claiming emitter) connects DC power supply (V _i) negative pole.Normal shock winding (the N of isolating transformer (T) _S1) an end swash winding (N with anti- _S2) non-same polarity link to each other 2. (N as lead-out terminal _S1) another termination rectifier diode (VD ₁) anode, (N _S2) another termination rectifier diode (VD ₂) anode and buffering diode (VD _R1) anode; Buffering diode (VD _R1) negative electrode meet (VD _R2) anode and buffering electric capacity (C _r) positive pole, (C _r) negative pole connect lead-out terminal 2.; Rectifier diode (VD ₁, VD ₂) negative electrode and buffering diode (VD _R2) negative electrode link to each other and meet filter inductance (L _o) an end.Filter inductance (L _o) another termination filter capacitor (C _o) anodal and 1. as lead-out terminal, (C _o) negative pole connect lead-out terminal 2..1., 2. lead-out terminal organizes the link of output and load as this.

Main circuit parameter is: m=1.5, D _Max=0.5, D _e=0.4, D _Min=0.33, f _s=10kHz; P _o=90W, V _o=18V, I _o=5A, L _{O (M)}=1.5Io, V _D=0.5V, V _i=300V ± 20%, η ₂=0.85; n ₂=0.0617, n ₁=0.0925, L _o=20 μ H, L _S2=38.3 μ H, L _p=5.25 μ H, I _{P2 (M)}=1.2A.

Claims (1)

1, a kind of normal shock-anti-sharp combination type DC/DC isolated converter, its main circuit is made of switching tube (VQ), isolating transformer (T), secondary commutation filter circuit (1) and elementary buffer network (2); Isolating transformer (T) has an elementary winding (N _p) and one or more sets secondary winding; Secondary commutation filter circuit (1) can be one or more groups output, one or more sets secondary winding of corresponding isolating transformer (T); Elementary buffer network (2) can be RCD network or LCD network; 1., 2. lead-out terminal organizes the link of output and load as this; It is characterized in that: every cover secondary winding of isolating transformer (T) comprises a normal shock winding (N _S1) and an anti-sharp winding (N _S2), every group of output of secondary commutation filter circuit (1) is by rectifier diode (VD ₁, VD ₂), buffering diode (VD _R1, VD _R2), buffer capacitor (C _r), filter capacitor (C ₀), filter inductance (L ₀) constitute; The annexation of each components and parts is: the elementary winding (N of isolating transformer (T) _p) an end connect DC power supply (V _i) positive pole, elementary winding (N _p) the other end connect the drain electrode of switching tube (VQ) or claim collector electrode; The source electrode of switching tube (VQ) or title emitter connect DC power supply (V _i) negative pole; Normal shock winding (the N of isolating transformer (T) _S1) an end swash winding (N with anti- _S2) non-same polarity link to each other 2. normal shock winding (N as lead-out terminal _S1) another termination rectifier diode (VD ₁) anode, instead swash winding (N _S2) another termination rectifier diode (VD ₂) anode and buffering diode (VD _R1) anode; Buffering diode (VD _R1) negative electrode meet buffering diode (VD _R2) anode and buffering electric capacity (C _r) positive pole, buffer capacitor (C _r) negative pole connect lead-out terminal 2.; Rectifier diode (VD ₁, VD ₂) negative electrode and buffering diode (VD _R2) negative electrode link to each other and meet filter inductance (L ₀) an end, filter inductance (L ₀) another termination filter capacitor (C ₀) anodal and 1. as lead-out terminal, filter capacitor (C ₀) negative pole connect lead-out terminal 2..

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