CN100433529C - ZCS-PWM switching unit circuit - Google Patents

Abstract

The invention comprises a main switch circuit and an auxiliary branch circuit. Wherein, the main switch circuit comprises a main switch tube and a diode connected to the main switch tube in inverse parallel; the auxiliary branch circuit comprises an auxiliary switch tube; the emitter of the auxiliary switch tube is connected to a resonance branch circuit where a clamping diode is connected in parallel; the cathode of clamping diode is connected to the emitter of the main switch tube, and its anode is connected to the emitter of the auxiliary switch tube. With the circuit based on the invention, a group of direct current converters can be acquired.

Description

ZCS-PWM switch element circuit

One, technical field

The present invention relates to a kind of switching circuit, relate in particular to a kind of ZCS-PWM switch element circuit that is applied to the switching mode power inverter.

Two, background technology

(MOSFET) compares with power field effect pipe, and insulated gate bipolar transistor (IGBT) conduction voltage drop is less, and rated voltage and current density are very high, thus in recent years by more applications in the high-tension high-power occasion.But, there are some shortcomings in the hard switching pwm converter that adopts IGBT to do switch element under the high-tension high-power occasion: (1) is because the IGBT switching speed is relatively slow, therefore the operating frequency of converter is difficult for improving, and the volume and weight of magnetic element is also bigger; (2) because the imperfect effect that melts pass behavior and circuit parasitic and distributed constant etc. of power electronic device on off state, cause power electronic device the hard switching effect in switch transient state, to occur, promptly in the switch transient process, the spike of high rate of change not only can appear in voltage waveform and current waveform, and both also have very big crossover region.For IGBT, because there is the current tail phenomenon in it when turn-offing, so turn-off power loss will be bigger, can reduce greatly in the functional reliability of high-frequency large-power occasions downconverter.

The effective ways that address the aforementioned drawbacks are Zero Current Switchs (Zero-current-switching is called for short ZCS) of realizing all IGBT in the pwm converter.Existing ZCS-PWM controlling schemes is a lot of both at home and abroad, though basic ideas are consistent, promptly utilizes resonant element to realize current over-zero, thus the purpose of Zero Current Switch; Interrupt resonant process by auxiliary switch, realized constant frequency control, but their performance still is some difference.Getting the most representative several technical scheme below analyzes:

(1) scheme 1: auxiliary branch is connected with the main switch loop and resonant inductance is connected with power tube

The main circuit topology that scheme 1 proposes as shown in Figure 1.As main switch S ₁When opening, resonant inductance L _rLimit the climbing of electric current, made S ₁Realized zero current turning-on; The resonant inductance electric current is reduced to zero and reverse flow, S ₁Anti-and diode D ₁Conducting, S ₁In electric current be zero, turn-off S this moment ₁, S so ₁It will be zero-current switching.Auxiliary switch S in addition ₂It also is Zero Current Switch.

(2) scheme 2: auxiliary branch is connected with power tube with parallel connection of main switch loop and resonant inductance

The main circuit topology that scheme 2 proposes as shown in Figure 2.By resonant inductance L _R1, L _R2Restriction main switch S ₁With auxiliary switch S ₂Current-rising-rate when opening realizes zero current turning-on; Resonant inductance L _R1, L _R2When middle electric current is reduced to zero and reverse flow, S ₁, S ₂Anti-and diode D ₁, D ₂S is worked as in conducting ₁, S ₂In electric current be zero, turn-off S this moment ₁, S ₂, S so ₁, S ₂It will be zero-current switching.

(3) scheme 3: auxiliary branch is not connected with power tube with parallel connection of main switch loop and resonant inductance

The main circuit topology that scheme 3 proposes as shown in Figure 3.By resonant inductance L _R1, L _R2Restriction main switch S ₁With auxiliary switch S ₂Current-rising-rate when opening realizes zero current turning-on; Resonant inductance L _R1, L _R2When middle electric current is reduced to zero and reverse flow, S ₁Anti-and diode current flow, S ₁In electric current be zero, turn-off S this moment ₁, S so ₁It will be zero-current switching.Auxiliary switch S in addition ₂It also is zero-current switching.

Such scheme can both be realized the Zero Current Switch of main switch and auxiliary switch, but has some shortcomings:

The shortcoming of scheme 1: main switch S ₁With resonant inductance L _rDirectly series connection makes that the current stress in the main switch is very big, and on-state loss is bigger, and the increase of the quota of selector switch pipe, makes cost increase; L in addition _rDirectly be connected in the main switch loop, on-state voltage drop is very big, has influenced the raising of transducer effciency.

The shortcoming of scheme 2: the auxiliary branch of this converter is in parallel with the main switch loop, and its work can not increase the voltage stress and the current stress of main switch, and the voltage stress and the current stress of main switch are very little.But resonant inductance is connected in main switch loop and the auxiliary branch, and loss is bigger.

The shortcoming of scheme 3: the auxiliary branch of this converter is in parallel with the main switch loop, and resonant inductance moves on in the afterflow branch road, so the voltage stress of main switch and current stress is very little and loss is less.But the existence of two resonant inductances makes that the structure of converter is not too succinct, and the voltage stress of auxiliary switch and current stress are very big in addition, and bear very large back-pressure in the reverse resonance of the resonant inductance stage.

Three, summary of the invention

1, goal of the invention: the purpose of this invention is to provide the ZCS-PWM switch element circuit that a kind of efficient height, loss are little, simple in structure, can overcome the defective that above-mentioned prior art exists.

2, technical scheme: in order to reach above-mentioned goal of the invention, the circuit of realizing first kind of scheme of the present invention comprises main switch loop and auxiliary branch, wherein, the main switch loop comprise main switch and with the antiparallel diode of main switch, auxiliary branch comprises auxiliary switch, the emitter of auxiliary switch is connected with a resonance branch road, this branch road comprises resonant inductance and the booster diode that is in series, booster diode is parallel with electric capacity, the negative electrode of booster diode is connected with resonant inductance, is provided with a main diode between the emitter of main switch and the emitter of auxiliary switch; The branch road that is connected with the emitter of auxiliary switch is parallel with clamping diode.The negative electrode of clamping diode is connected with the emitter of auxiliary switch, and anode is connected with the positive pole of booster diode.The negative electrode of main diode is connected with the emitter of main switch, and anode is connected with the emitter of auxiliary switch.

The circuit of realizing second kind of scheme of the present invention comprises main switch loop and auxiliary branch, wherein, the main switch loop comprise main switch and with the antiparallel diode of main switch, auxiliary branch comprises auxiliary switch, the emitter of main switch is connected with a branch road, this branch road comprises resonant inductance and the booster diode that is in series, booster diode is parallel with electric capacity, the negative pole of booster diode is connected with resonant inductance, be provided with a main diode between the emitter of main switch and the emitter of auxiliary switch, the anode of this main diode is connected with the emitter of main switch, and negative electrode is connected with the emitter of auxiliary switch; A branch road that is connected with the emitter of main switch is parallel with clamping diode.The negative electrode of clamping diode is connected with the emitter of main switch, and anode is connected with the anode of booster diode.

The circuit of realizing the third scheme of the present invention comprises main switch loop and auxiliary branch, wherein, loop of power circuit comprise main switch and with the antiparallel diode of main switch, auxiliary branch comprises auxiliary switch, the collector electrode of auxiliary switch is connected with a resonance branch road, this branch road comprises resonant inductance and the booster diode that is in series, booster diode is parallel with electric capacity, the anode of booster diode is connected with resonant inductance, be provided with a main diode between the collector electrode of main switch and auxiliary switch, the anode of this main diode is connected with the collector electrode of main switch, and negative electrode is connected with the collector electrode of auxiliary switch; A branch road that is connected with the collector electrode of auxiliary switch is parallel with a clamping diode.The anode of clamping diode is connected with the collector electrode of auxiliary switch, and negative electrode is connected with the negative electrode of booster diode.

Circuit of the present invention absorbs the advantage of scheme 3 main circuit topologies shown in Figure 3 and improves, and obtains a kind of new ZCS-PWM switch element circuit.Compare with the main circuit of existing scheme 3, new switch element circuit has been removed a resonant inductance L _R1, make in the real work auxiliary switch no longer bear back-pressure and current stress is reduced greatly, and main circuit structure also is simplified; Because diode D ₁Reverse recovery, its junction capacitance and resonant inductance L _rSeries resonance will take place, thus can be at n ₁Point produces very big negative potential, makes main switch and auxiliary switch produce very big due to voltage spikes.By at n ₁And clamping diode D in parallel between a point ₃, make n ₁The point current potential be clamped at a less negative value, finally the due to voltage spikes on main switch and the auxiliary switch can be suppressed at one little on negligible value.

ZCS-PWM switch element circuit based on this novelty can obtain gang's DC converter, as shown in Figure 5.They can both realize the zero voltage switch of Zero Current Switch He all passive switch devices of all active switch devices, and realize that the principle of soft switch aspect is identical.

3, beneficial effect: this circuit structure is succinct, controls simple and conveniently, and the voltage stress of power device and current stress are all very low, efficient is high, electromagnetic interference is little, reliable operation, can be applied to the high-tension high-power occasion.

Four, description of drawings

Fig. 1 is the main circuit topological structure schematic diagram that existing ZCS-PWM controlling schemes 1 proposes;

Fig. 2 is the main circuit topological structure schematic diagram that existing ZCS-PWM controlling schemes 2 proposes;

Fig. 3 is the main circuit topological structure schematic diagram that existing ZCS-PWM controlling schemes 3 proposes;

Fig. 4 is a ZCS-PWM switch element electrical block diagram of the present invention;

Fig. 5 is based on the transformer configuration schematic diagram that ZCS-PWM switch element circuit constitutes, wherein, and (a) Buck. (b) Boost. (c) Buck-boost. (d) Cuk. (e) Sepic. (f) Zeta;

Fig. 6 is based on the buck transformer configuration schematic diagram of ZCS-PWM switch element circuit;

Fig. 7 is the equivalent electric circuit of each operation mode correspondence of buck converter;

Fig. 8 is the main waveform schematic diagram of ZCS-PWM buck converter of the present invention in a work period;

Fig. 9 has clamping diode D ₃The time test waveform, wherein (a) is full load i _S1And v _S1Waveform, (b) be full load i _S2And v _S2Waveform, i when (c) being 10% load _S1And v _S1Waveform, i when (d) being 10% load _S2And v _S2Waveform: 100V/div, 6A/div, 4 μ s/div;

Figure 10 does not have clamping diode D ₃The time test waveform, wherein (a) is full load v _S1And v _S2Waveform, v when (b) being 10% load _S1And v _S2Waveform: 100V/div, 4 μ s/div;

Figure 11 is the efficiency curve schematic diagram.

Five, embodiment

Embodiment 1: as Fig. 4, Fig. 5 (a), (d) with (f), the ZCS-PWM switch element circuit of present embodiment comprises main switch loop and auxiliary branch, and wherein, the main switch loop comprises main switch S ₁With with main switch S ₁Antiparallel diode, auxiliary branch comprise auxiliary switch S ₂, auxiliary switch S ₂Emitter be connected with a resonance branch road, this branch road comprises the resonant inductance L that is in series _rWith booster diode D ₂, booster diode D ₂Be parallel with capacitor C _r, booster diode D ₂Negative electrode and resonant inductance L _rConnect main switch S ₁Emitter and auxiliary switch S ₂Emitter between be provided with a main diode D ₁With auxiliary switch S ₂The branch road that connects of emitter be parallel with a clamping diode D ₃Clamping diode D ₃Negative electrode and auxiliary switch S ₂Emitter connect anode and booster diode D ₂Positive pole connect.Main diode D ₁Negative electrode and main switch S ₁Emitter connect anode and auxiliary switch S ₂Emitter connect.

Embodiment 2: as figure (5) (c) shown in, present embodiment is the ZCS-PWM switch element circuit of another kind of structure, comprises main switch loop and auxiliary branch, wherein, the main switch loop comprises main switch S ₁With with main switch S ₁Antiparallel diode, auxiliary branch comprise auxiliary switch S ₂, main switch S ₁Emitter be connected with a resonance branch road, this branch road comprises the resonant inductance L that is in series _rWith booster diode D ₂, booster diode D ₂Be parallel with capacitor C _r, booster diode D ₂Negative pole and resonant inductance L _rConnect main switch S ₁Emitter and auxiliary switch S ₂Emitter between be provided with a main diode D ₁, this main diode D ₁Anode and main switch S ₁Emitter connect negative electrode and auxiliary switch S ₂Emitter connect; With main switch S ₁A branch road connecting of emitter be parallel with clamping diode D ₃Clamping diode D ₃Negative electrode and main switch S ₁Emitter connect anode and booster diode D ₂Anode connect.

Embodiment 3: as Fig. 5 (b) with (e), present embodiment is the ZCS-PWM switch element circuit of another kind of structure, comprises main switch loop and auxiliary branch, and wherein, loop of power circuit comprises main switch S ₁With with main switch S ₁Antiparallel diode, auxiliary branch comprise auxiliary switch S ₂, auxiliary switch S ₂Collector electrode be connected with a resonance branch road, this branch road comprises the resonant inductance L that is in series _rWith booster diode D ₂, booster diode D ₂Be parallel with capacitor C _r, booster diode D ₂Anode and resonant inductance L _rConnect main switch S ₁With auxiliary switch S ₂Collector electrode between be provided with main diode D ₁, this main diode D ₁Anode and main switch S ₁Collector electrode connect negative electrode and auxiliary switch S ₂Collector electrode connect; With auxiliary switch S ₂A branch road connecting of collector electrode be parallel with clamping diode D ₃Clamping diode D ₃Anode and auxiliary switch S ₂Collector electrode connect negative electrode and booster diode D ₂Negative electrode connect.

Embodiment 4: as shown in Figure 6, present embodiment is the buck converter based on switch element circuit shown in Fig. 5 (a).

The work of supposing the buck converter has been in stable state, and all active switch devices all are desirable devices, input voltage V _InConstant, n ₀Be zero-potential point, output inductor L _oMake it can regard current source I as very greatly _o, resonant inductance L _rBe far smaller than output inductor L _o

Based on these hypothesis, the work of buck converter in one-period can be divided into 9 mode, and the equivalent electric circuit of each operation mode correspondence is analyzed respectively as shown in Figure 7 below.

(1) operation mode 1[t ₀, t ₁] (equivalent electric circuit is shown in Fig. 7 (a)):

At t ₀Constantly, the buck converter is in the afterflow stage, output current I _oBe linear decline in fact, so resonant inductance L _rOn pressure drop and diode D ₂The conduction voltage drop sum less than clamping diode D ₃Conduction voltage drop, the freewheel current overwhelming majority all flows through resonant inductance and diode D ₂, this phenomenon is more obvious when output current is very big.For the convenience of analyzing, think that the electric current that flows through resonant inductance is exactly output current I _oAt t ₀Constantly open main switch S ₁, resonant inductance L _rBear back-pressure-V _In, the electric current that flows through resonant inductance descends linearity, flows through linear rising of electric current of main switch, therefore at t ₀Moment main switch S ₁It is zero current turning-on.Flowing through the electric current of resonant inductance and the voltage on the resonant capacitance is respectively: $i_{\mathrm{Lr}}\left(t\right)=I_o-\frac{V_{\mathrm{in}}}{L_r}(t-t_0),---\left(1\right)$

v _Cr(t)＝0. (2)

At t ₁Constantly, the electric current of resonant inductance is by I _oDrop to zero, the electric current that flows through main switch is by the I of being raised to above freezing _o, this moment diode D ₁, D ₂For no-voltage is turn-offed.The duration of operation mode 1 is:

$\mathrm{\Δ}{t}_1=\frac{I_o{L}_r}{V_{\mathrm{in}}}.---\left(3\right)$

(2) operation mode 2[t ₁, t ₂] (equivalent electric circuit is shown in Fig. 7 (b)):

In this stage, because diode D ₁Reverse recovery, flow through diode D ₁Electric current will oppositely increase by zero, this moment D ₁Can equivalence be its junction capacitance C _jSo C _j, L _rAnd C _rBe actually and be cascaded, and because C _j＜＜C _rSo, resonant capacitance C _rCan be left in the basket and disregard.From t ₁Constantly begin C _j, L _rSeries resonance will take place, and flow through the current i of resonant inductance _Lr(t) and the voltage v on the junction capacitance _Cj(t) be respectively:

$i_{\mathrm{Lr}}\left(t\right)=\frac{V_{\mathrm{in}}}{Z_{o1}}\sin {\mathrm{\ω}}_{r1}t,---\left(4\right)$

v _Cj(t)＝V _in-V _incosω _r1t (5)

In the formula, $Z_{o1}=\sqrt{L_r/C_j},$ ${\mathrm{\ω}}_{r1}=1/\sqrt{L_r{C}_j}.$

Thereby:

V _n1＝V _incosω _r1t. (6)

At t ₂Moment V _N1=-V _D3, V _D3Be clamping diode D ₃Conduction voltage drop, this moment should finish in the stage.The duration of operation mode 2 is:

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="C20061008578700132.png,C20061008578700161.png"\; state="\{\{state\}\}">t</figure-callout>}}_2=\frac{\mathrm{\&pi;}}{2{\mathrm{\&omega;}}_{r1}}+\frac{1}{{\mathrm{\&omega;}}_{r1}}{\sin }^{-1}\left(\frac{V_{D3}}{V_{\mathrm{in}}}\right).---\left(7\right)$

(3) operation mode 3[t ₂, t ₃] (equivalent electric circuit is shown in Fig. 7 (c)):

At t ₂Moment D ₃Conducting, n ₁The current potential of point by pincers at-V _D3, this moment C _jWith L _rSeries resonance finish.L _rWill with C _rSeries resonance takes place, and flows through the current i of resonant inductance _Lr(t) and the voltage v on the resonant capacitance _Cr(t) be respectively:

$i_{\mathrm{Lr}}\left(t\right)=i_{\mathrm{Lr}}\left(t_2\right)\cos {\mathrm{\&omega;}}_{r}t-\frac{V_{D3}}{Z_o}\sin {\mathrm{\&omega;}}_{r}t,---\left(8\right)$

v _Cr(t)＝-V _D3+V _D3cosω _rt+i _Lr(t ₂)ω _rsinω _rt，(9)

In the formula $Z_o=\sqrt{L_r/C_r},$ ${\mathrm{\&omega;}}_r=1/\sqrt{L_r{C}_r}.$

At t ₃Moment i _Lr(t)=0, this stage finishes.The duration of operation mode 3 is:

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="C20061008578700161.png"\; state="\{\{state\}\}">t</figure-callout>}}_3={\mathrm{ctg}}^{-1}\left(\frac{V_{D3}}{Z_o{i}_{\mathrm{Lr}}\left(t_2\right)}\right).---\left(10\right)$

(4) operation mode 4[t ₃, t ₄] (equivalent electric circuit is shown in Fig. 7 (d)):

In this stage, main switch S ₁Continue to keep conducting, flow through S ₁Electric current still be output current I _oBut auxiliary switch and all diodes all turn-off.Flow through the current i of resonant inductance _Lr(t) and the voltage v on the resonant capacitance _Cr(t) be respectively:

i _Lr(t)＝0， (11)

v _Cr(t)＝v _Cr(t ₃). (12)

The duration of mode 4 is:

Δt ₄＝DT _s-Δt ₁-Δt ₂-Δt ₃， (13)

D is a duty ratio in the formula, T _s=1/f _sBe switch periods, and f _sBe switching frequency.

(5) operation mode 5[t ₄, t ₅] (equivalent electric circuit is shown in Fig. 7 (e)):

At t ₄Open auxiliary switch S ₂, L _rWill with C _rSeries resonance takes place, and flows through S ₂Current i _S2(t) rise gradually by zero, so S ₂Be zero current turning-on.At this stage main switch S that flows through ₁Electric current still be I _o, flow through the current i of resonant inductance _Lr(t) and the voltage v on the resonant capacitance _Cr(t) be respectively:

$i_{\mathrm{Lr}}\left(t\right)=-\frac{[V_{\mathrm{in}}-v_{\mathrm{Cr}}\left(t_3\right)]}{Z_o}\sin {\mathrm{\&omega;}}_r(t-t_4),---\left(14\right)$

v _Cr(t)＝V _in-[V _in-v _Cr(t ₃)]cosω _r(t-t ₄). (15)

At t ₅Moment i _S2(t) reduce to zero again, turn-off auxiliary switch S this moment ₂, so S ₂Be zero-current switching.The duration of mode 5 is:

$\mathrm{\&Delta;}{t}_5=\frac{\mathrm{\&pi;}}{{\mathrm{\&omega;}}_r}.---\left(16\right)$

(6) operation mode 6[t ₅, t ₆] (equivalent electric circuit is shown in Fig. 7 (f)):

Because S ₂Turn-off, so L _rAnd C _rCan only pass through D ₁, S ₁And V _InContinue resonance.The voltage v of resonant capacitance _Cr(t) descend gradually by maximum, and inductive current i _Lr(t) then oppositely increase gradually by zero.The flow through this moment current i of main switch _S1(t) from I _oDescend gradually, and at t ₆Drop to zero, mode 6 end this moment.In this mode, flow through the current i of resonant inductance _Lr(t) and the voltage v on the resonant capacitance _Cr(t) be respectively:

$i_{\mathrm{Lr}}\left(t\right)=\frac{V_{\mathrm{in}}-v_{\mathrm{Cr}}\left(t_3\right)}{Z_o}\sin {\mathrm{\&omega;}}_r(t-t_5),---\left(17\right)$

v _Cr(t)＝V _in+[V _in-v _Cr(t ₃)]cosω _r(t-t ₅). (18)

The duration of mode 6 is:

$\mathrm{\&Delta;}{t}_6=\frac{1}{{\mathrm{\&omega;}}_r}{\sin }^{-1}\left[\frac{I_o{Z}_o}{V_{\mathrm{in}}-v_{\mathrm{Cr}}\left(t_3\right)}\right].---\left(19\right)$

(7) operation mode 7[t ₆, t ₇] (equivalent electric circuit is shown in Fig. 7 (g)):

At t ₆Moment current i _S1(t) drop to zero,,, turn-off S this moment so resonance can only be proceeded by the anti-and diode of main switch because IGBT can not flow through reverse current ₁So S ₁It will be zero-current switching.When resonance current by I _oIncrease to maximum gradually, have maximum to reduce to I again again _oThe time, i.e. t ₇Constantly, this stage finishes.In this mode, flow through the current i of resonant inductance _Lr(t) and the voltage v on the resonant capacitance _Cr(t) be respectively:

$i_{\mathrm{Lr}}\left(t\right)=\frac{V_{\mathrm{in}}-v_{\mathrm{Cr}}\left(t_3\right)}{Z_o}\sin {\mathrm{\&omega;}}_r(t-t_5),---\left(20\right)$

v _Cr(t)＝V _in+[V _in-v _Cr(t ₃)]cosω _r(t-t ₅). (21)

The duration of mode 7 is:

$\mathrm{\&Delta;}{t}_7=\frac{\mathrm{\&pi;}}{{\mathrm{\&omega;}}_r}-2\mathrm{\&Delta;}{t}_6.---\left(22\right)$

(8) operation mode 8[t ₇, t ₈] (equivalent electric circuit is shown in Fig. 7 (h)):

At t ₇Constantly, resonance current is I _o, flow through S this moment ₁Electric current anti-and diode is zero, so S ₁Anti-and diode be that no-voltage is turn-offed.After this, C _r, L _r, D ₁With current source be series relationship, so the electric current of the resonant inductance of flowing through is I _oConstant, resonance finishes, and resonant capacitance begins linear discharge.In this mode, flow through the current i of resonant inductance _Lr(t) and the voltage v on the resonant capacitance _Cr(t) be respectively:

i _Lr(t)＝I _o， (23)

$v_{\mathrm{Cr}}\left(t\right)=v_{\mathrm{Cr}}\left(t_7\right)-\frac{I_o}{C_r}(t-t_7).---\left(24\right)$

At t ₈Constantly, the voltage on the resonant capacitance reduces to zero, and mode 8 finishes.The duration of this mode is:

$\mathrm{\&Delta;}{t}_8=\frac{C_r}{I_o}\{V_{\mathrm{in}}+[V_{\mathrm{in}}-v_{\mathrm{Cr}}\left(t_3\right)\left]\cos {\mathrm{\&omega;}}_r(\mathrm{\&Delta;}{t}_5+\mathrm{\&Delta;}{t}_6)\right\}.---\left(25\right)$

(9) operation mode 9[t ₈, t ₉] (equivalent electric circuit is shown in Fig. 7 (i)):

At t ₈Constantly, electric energy stored discharges and finishes on the resonant capacitance, and current source passes through D ₂, D ₁, L _rAnd afterflow, this stage is maintained to t ₉Constantly, open S this moment ₁, next cycle restarts.In this mode, flow through the current i of resonant inductance _Lr(t) and the voltage v on the resonant capacitance _Cr(t) be respectively:

i _Lr(t)＝I _o， (26)

v _Cr(t)＝0. (27)

The duration of mode 9 is:

$\mathrm{\&Delta;}{t}_9=T_s-D{T}_s-\frac{2\mathrm{\&pi;}}{{\mathrm{\&omega;}}_r}+\mathrm{\&Delta;}{t}_6-\mathrm{\&Delta;}{t}_8.---\left(28\right)$

By top analysis, can draw the main waveform of this buck converter, as shown in Figure 8 at one-period.Can find, guarantee that this novel ZCS-PWM buck converter can both realize that under the situation of nonoverload the unique conditional of the soft switch of ZCS must satisfy following inequality exactly:

$I_{o,\max }\&le;\frac{V_{\mathrm{in}}}{Z_o},---\left(29\right)$

In the formula, I _{O, max}It is the maximum of output current.

According to above analysis, developed the buck converter model machine of a stylobate, input voltage V in ZCS-PWM switch element circuit shown in Figure 4 _In=100V, rated output voltage V _o=60V, rated output power P _o=300W, switching frequency f _s=30kHz, resonant inductance L _R1=L _R2=6 μ H, resonant capacitance C _r=100nF, filter inductance L _o=1mH, filter capacitor C _o=470 μ F.Model machine S ₁, S ₂Select G25N120 for use, D ₁, D ₂, D ₃Select HFA25TB60 for use.The experimental result that obtains under fully loaded and 10% loading condition as shown in Figure 9.Shown in Figure 10 is respectively not have clamping diode D under fully loaded and 10% loading condition ₃The time switching tube voltage waveform.The efficiency curve of converter as shown in figure 11.

Advantages such as it is simple for structure that above test waveform has illustrated that this buck converter has, and the voltage stress and the current stress of switching tube are all very little, can realize soft switch in whole loading range, and the efficient of converter is higher, and electromagnetic interference is less.

Other converters shown in Figure 5 realize that the principle of soft switch is similar to above-mentioned buck converter.

Claims (3)

1, a kind of ZCS-PWM switch element circuit comprises main switch loop and auxiliary branch, and wherein, the main switch loop comprises main switch (S ₁) and with main switch (S ₁) antiparallel diode, auxiliary branch comprises auxiliary switch (S ₂), main switch (S ₁) and auxiliary switch (S ₂) collector electrode connect auxiliary switch (S ₂) emitter be connected with a resonance branch road, this resonance branch road comprises the resonant inductance (L that is in series _r) and booster diode (D ₂), booster diode (D ₂) be parallel with electric capacity (C _r), booster diode (D ₂) negative electrode and resonant inductance (L _r) connect, it is characterized in that main switch (S ₁) emitter and auxiliary switch (S ₂) emitter between be provided with a main diode (D ₁), main diode (D ₁) anode and auxiliary switch (S ₂) emitter connect main diode (D ₁) negative electrode and main switch (S ₁) emitter connect; With auxiliary switch (S ₂) the resonance branch road that connects of emitter be parallel with a clamping diode (D ₃), clamping diode (D ₃) negative electrode and auxiliary switch (S ₂) emitter connect anode and booster diode (D ₂) anode connect.

2, a kind of ZCS-PWM switch element circuit comprises main switch loop and auxiliary branch, and wherein, the main switch loop comprises main switch (S ₁) and with main switch (S ₁) antiparallel diode, auxiliary branch comprises auxiliary switch (S ₂), main switch (S ₁) and auxiliary switch (S ₂) collector electrode connect main switch (S ₁) emitter be connected with a resonance branch road, this resonance branch road comprises the resonant inductance (L that is in series _r) and booster diode (D ₂), booster diode (D ₂) be parallel with electric capacity (C _r), booster diode (D ₂) negative pole and resonant inductance (L _r) connect, it is characterized in that main switch (S ₁) emitter and auxiliary switch (S ₂) emitter between be provided with a main diode (D ₁), this main diode (D ₁) anode and main switch (S ₁) emitter connect negative electrode and auxiliary switch (S ₂) emitter connect; With main switch (S ₁) the resonance branch road that connects of emitter be parallel with clamping diode (D ₃), clamping diode (D ₃) negative electrode and main switch (S ₁) emitter connect anode and booster diode (D ₂) anode connect.

3, a kind of ZCS-PWM switch element circuit comprises main switch loop and auxiliary branch, and wherein, the main switch loop comprises main switch (S ₁) and with main switch (S ₁) antiparallel diode, auxiliary branch comprises auxiliary switch (S ₂), auxiliary switch (S ₂) collector electrode be connected with a resonance branch road, this resonance branch road comprises the resonant inductance (L that is in series _r) and booster diode (D ₂), booster diode (D ₂) be parallel with electric capacity (C _r), booster diode (D ₂) anode and resonant inductance (L _r) connect, it is characterized in that main switch (S ₁) and auxiliary switch (S ₂) collector electrode between be provided with main diode (D ₁), this main diode (D ₁) anode and main switch (S ₁) collector electrode connect negative electrode and auxiliary switch (S ₂) collector electrode connect; Main switch (S ₁) and auxiliary switch (S ₂) emitter be connected; With auxiliary switch (S ₂) the resonance branch road that connects of collector electrode be parallel with clamping diode (D ₃), clamping diode (D ₃) anode and auxiliary switch (S ₂) collector electrode connect negative electrode and booster diode (D ₂) negative electrode connect.

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