CN1254217A - Constant ractive current compensation full-bridge phase-shifting resonance soft switch technique - Google Patents

Abstract

The present invention relates to a constant reactive current compensated full-bridge phase-shifting resonant soft switch technology, and is aimed at changing main transformer and its leakage inductance in main circuit of switching power supply or excitation current I8 on additional inductive branch to make it increase to I80 level and do not change its phase property, do not change its magnetic flux or slightly reduce it, make total current of primary side after I8 is increased by more than 10 times when it is underload, and when it is full-load its increment is very little. this is implemented mainly by opening larger air gap on the main transformer. Said invention obviously reduces switching loss and heat-producing quantity of main control device of switching power supply, effectively inhibits the surge voltage and current, not only raises the efficiency of switching power supply, but also greatly raises its stability and reliability.

Description

Constant ractive current compensation full-bridge phase-shifting resonance soft switch technique

The present invention relates to field of switch power, specifically be meant a kind of full-bridge phase-shifting resonance soft switch technique that adopts constant ractive current compensation.

Full-bridge phase-shifting resonance high frequency switch power proportion on Switching Power Supply market is more and more big, uses more and more extensively, and the whole efficiency of its module can reach 88%～92% level.Efficient than old-fashioned SCR phased switch power supply has improved more than 10%, and obvious improvement has been arranged.Can further improve the efficient of full-bridge phase-shifting resonance high frequency switch power, will be next step important goal will pursuing.In addition, the voltage stress that present high frequency switch power master control device bears, with

Value is explained, approximately all 3000 volts of every microseconds between 1000 volts of every microseconds because Be worth higherly, the surge voltage of each point and surge current still can not good restraining in the circuit, if can further reduce in the circuit Value, then the stability of high frequency switch power, reliability will have further improvement, and this is another important symbol that high frequency switch power advances.

The purpose of this invention is to provide a kind of the switching loss of the master control device in the full-bridge phase-shifting resonance high-frequency switching power supply module is reduced greatly, efficient further improves, can effectively reduce the module caloric value, improve the master control device condition of work, prolong components and parts useful life, effectively suppress surge voltage, surge current generation, reduce voltage stress and current stress that the master control device bears, make switching process be in a kind of smoothly stable operating state, and then improve high frequency switch power stability, technology of dependability greatly.

Before telling about relevant basic principle of the present invention and new design, following statement is arranged now, it is the control logic part of the related full-bridge phase-shifting resonance high frequency switch power of specification of the present invention, directly adopt commercial UC3875 or UC3879 integrated package, because this is an integrated package of having popularized very much, about it function and use and not belong to the explanation of this specification and to introduce category, the present invention does not have specific (special) requirements when using UC3875 or UC3879 to make control logic.

The main circuit of full-bridge phase-shifting resonance high frequency switch power is as figure (), and E is an applied voltage among the figure, and the master control device can be the IGBT pipe, also can be the MOSFET pipe, uses Q respectively ₁, Q ₂, Q ₃, Q ₄Expression, represents respectively with 1,2,3,4 footnotes also that main transformer is T, wherein inductance L with master control device diode connected in parallel and electric capacity _SRepresent the leakage inductance of main transformer and the various stray inductances in the circuit, also might be not enough to offer the enough rechargeable energies of shunt capacitance C, then also can add an inductance, after merging with former leakage inductance, still with L because the leakage inductance value of main transformer is too little _SExpression.According to the requirement of UC3875 control logic, Q ₄Pipe should compare Q ₁Pipe conducting in advance, Q ₃Pipe compares Q ₂So pipe conducting in advance is Q ₃Pipe and Q ₄The brachium pontis that pipe is formed is called leading-bridge, in like manner Q ₁Pipe and Q ₂The brachium pontis that pipe is formed is called lagging leg.

In the full-bridge circuit shown in the figure (), master control device Q ₁Q ₂Q ₃Q ₄Turn on and off loss, available figure (two) describes, and is existing with Q ₄Pipe is described as follows for example:

In figure (two), master control device Q has drawn ₄Operating current I _Q4, grid voltage U _G4With tube voltage drop U _CE4Curve in turn off process, wherein the oabd line segment is to turn-off Q under the full load condition ₄During pipe, voltage U _CE4The track that rises, U under this state _CE4Voltage is t by the time of the E of being raised to above freezing _a, the ocd line segment then is under the Light Condition, turn-offs Q ₄During pipe, voltage U _CE4The track that rises, obd line segment turn-off Q when then being the load of some centres ₄Pipe U _CE4The track that rises.T among the figure ₀Time is represented Q ₄Pipe closes has no progeny I _Q4Drop to for zero time, t _Q3Representative and Q ₄Another master control device Q on the brachium pontis of pipe series connection ₃Manage the time of actual conducting, t _Q3Should be greater than t ₀, otherwise it is straight-through that brachium pontis is formed power supply, and cause catastrophic effect.

By figure (two) as can be seen, full load turn-offs Q ₄Pipe is because the full load operating current is very big, again because L _SExistence, so turn-off Q ₄After freewheel current also very big, with Q ₄The capacitor C that pipe is in parallel ₄Be filled soon, so the oa line segment is very steep, t _aTime is very short.During moderate duty, operating current is little, so after turn-offing the master control pipe, freewheel current is also not very big, then C ₄It is unhappy to charge, shown in the ob line segment.During underloading, operating current is very little, turn-offs Q ₄After, to C ₄Charging current very little, so that the oc line segment rises is very slow, that is the U of this moment _CE4Up to t _Q3Constantly, it is still not high to rise, at t _Q3Constantly, Q ₃The pipe conducting that is triggered is because of U _CE4=U _C4, and (U _C3+ U _C4) be constantly equal to E, so work as Q ₃Pipe is at t _Q3During the time trigger conducting, U _C3Bust arrives zero, U _CE4Just be compelled to by the c point d point that jumps.

Q ₄Turn-off power loss, should be t ₀In period, i _Q4(t) and u _CE4(t) function of product, obvious full load, u _CE4(t) the area oabt that is surrounded ₀Value big, so loss is big.During underloading, because operating current is to when young 20 times, oc line segment gradient is very low again, so the turn-off power loss during underloading is very little, so research and analysis turn-off power loss problem, should under full load condition, analyze and research.

Referring to figure (three), oa ' among the figure ₄, oa ' ₃..., oa ₀..., oa " ₄, oa " ₅Represent respectively under the full load conditions on line segment and to turn-off Q ₄After the pipe, U _CE4The voltage ascending curve of the different gradients that may have, figure (one) if in continue to increase C ₄Value, then turn-off Q ₄Afterwards, to C ₄Charging interval will constantly prolong that is U _CE4On rise slowlyer, be reflected at that to show as corresponding line segment inclined degree among the figure (three) more and more low, if Q ₄Pipe closes has no progeny voltage U _CE4On rise just at t ₀Constantly reach supply voltage E, as oa among the figure (three) ₀Line segment, this is that a specific state (is I _Q4When electric current drops to zero, U _CE4Just in time rise to E).Can be called critical condition, existing just with the turn-off power loss under this critical condition as the reference standard, with observation C ₄Size and the relation of turn-off power loss.

In figure (three), current i _Q4(t) expression is: $i_{Q4}\left(t\right)=-\frac{I_{Q4}}{t_0}t+I_{\mathrm{<figure-callout\; id="4"\; label="Q"\; filenames="A9812166800281.png"\; state="\{\{state\}\}">Q</figure-callout>}4}$

And oa ₀U under this particular state of line segment _CE4(t) expression is: $u_{\mathrm{CE}4}\left(t\right)=\frac{E}{t_0}t$

The turn-off power loss W during critical condition then _OFFFor:

$=\frac{{\mathrm{<figure-callout\; id="4"\; label="I\; Q"\; filenames="A9812166800281.png"\; state="\{\{state\}\}">I</figure-callout>}}_Q\&CenterDot;E\&CenterDot;{\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="A9812166800272.png,A9812166800281.png"\; state="\{\{state\}\}">t</figure-callout>}}_0}{6}-----\left(1\right)$ If the existing C that reduces ₄Value, Q then ₄Have no progeny in the pass, U _CE4On rise to accelerate, establish U _CE4The time t that rises to E is respectively 0.8t ₀, 0.6t ₀, 0.4t ₀, 0.2t ₀[in figure (three), respectively with oa ₁', oa ₂', oa ₃', oa ₄' wait line segment to represent], write out u separately _CE4(t) integration after the expression formula, it is as follows to get the result:

Work as t=0.8t ₀The time [u _CE4(t) rise to the time ratio critical condition t of E ₀Leading 20%], its loss is , promptly turn-off power loss has increased by 24% and has worked as t=0.6t ₀, its loss is

, promptly turn-off power loss has increased by 56% and has worked as t=0.4t ₀, its loss is

, promptly turn-off power loss has increased by 96% and has worked as t=0.2t ₀, its loss is

Otherwise be that turn-off power loss has increased by 144%, if increase C ₄Value, then turn-off Q ₄After, U _CE4On rise and slow down, gradient reduces, and establishes U _CE4The time t that rises to E is respectively 1.2t ₀, 1.4t ₀, 1.6t ₀, 1.8t ₀, 2.0t ₀[figure (three) in respectively with oa ₁", oa ₂", oa ₃", oa ₄", oa ₅" wait line segment to represent], write out u separately _CE4(t) integration after the expression formula, it is as follows to get the result:

Work as t=1.2t ₀The time [u _CE4(t) rise to the t of the time ratio critical condition of E ₀Lag behind 20%], its loss is Be that turn-off power loss can reduce 16.7% and works as t=1.4t ₀, its loss is

, promptly turn-off power loss can reduce 28.6% and works as t=1.6t ₀, its loss is , promptly turn-off power loss can reduce 37.5% and works as t=1.8t ₀, its loss is

, promptly turn-off power loss can reduce 44.5% and works as t=2.0t ₀, its loss is

Be turn-off power loss can reduce 50% existing with top result of calculation tabulation as table () shown in: show (one) U _CE4Rise time is compared t ₀The leading list that concerns that lags behind with turn-off power loss that reaches

Leading and hysteretic state	Leading 80%	Leading 60%	Leading 40%	Leading 20%	Critical condition	Lag behind 20%	Lag behind 40%	Lag behind 60%	Lag behind 80%	Lag behind 100%
											????U CE4Rise to the time of E	?0.2t 0	?0.4t 0	?0.6t 0	?0.8t 0	??t 0	?1.2t 0	?1.4t 0	?1.6t 0	?1.8t 0	?2.0t 0
The turn-off power loss relative value	?2.44	?1.96	?1.56	?1.24	??1	?0.833	?0.714	?0.625	?0.555	?0.5
											Loss increases	?144％	?96％	?56％	?24％
Loss reduces						?16.7％	?28.6％	?37.5％	?44.5％	?50％

By the calculating done of figure (three) and the data of table (), after it is analyzed, as can be seen:

1. in order to reduce the turn-off power loss of full load, C ₄Electric capacity should be selected bigger numerical value for use, makes Q ₄Pipe closes has no progeny U _CE4Rising slow, the gradient of ascending curve is low, then its turn-off power loss is fewer, the time that rises to E in addition preferably is greater than t ₀

But then, from the data of figure (three) and table (), C ₄Excessively strengthen, at u _CE4(t) time that rises to E reaches 2.0t ₀Afterwards, strengthen the value of shunt capacitance again, the decline of turn-off power loss is not remarkable, loses duty ratio in rain, so the value of shunt capacitance on the master control device also needn't unconfinedly increase more.

2. because u whenever _CE4(t)+u _CE3(t) be constantly equal to applied voltage E, so in figure (three), work as u _CE4When (t) rising to E, inevitable u _CE3(t) dropped to zero volt, so Q ₃The actual firing point t of pipe _Q3Should be arranged in and U _CE4After a point of corresponding that oa curve, Q then ₃Pipe must be that no-voltage is open-minded, and no turn-on consumption realizes that this point is not difficult, in fact just adjusts Q ₄Pipe and Q ₃Dead band between the pipe drive signal is problem at interval.The front is mentioned in addition, t _Q3Also must be at t ₀Afterwards, to prevent that bridge arm direct pass from forming short trouble.

3. figure (three) and table () are though be at Q ₄Analysis that the turn-off power loss of pipe is made and calculating, but from the principle of formation turn-off power loss and the computational methods of turn-off power loss size, Q ₁, Q ₂, Q ₃, Q ₄Pipe all is the same, thus top analysis and result of calculation, to Q ₁, Q ₂, Q ₃Pipe also all is suitable for.It more than is the analytical calculation of full load turn-off power loss.

About turn-on consumption, through the discussion of front, Q is turn-offed in identification that can be clear and definite ₄Open Q ₃, or turn-off Q ₃Open Q ₄(to Q ₁, Q ₂The shutoff of pipe is opened too), as long as turn-off the U of pipe _CERising to after the E, open another pipe in the same brachium pontis again, must be that no-voltage is open-minded, no turn-on consumption.Because under full load conditions, operating current is very big, and the master control pipe closes has no progeny, and freewheel current is also very big, and is also big to the charging current of the shunt capacitance that is turned off pipe, then is turned off the U of pipe _CEVoltage ratio is easier to rise to the E value, and another pipe in the then same brachium pontis just realizes that than being easier to no-voltage is open-minded.

But when underloading and since this moment operating current than the operating current of full load to when young more than 20 times, the master control pipe closes has no progeny, freewheel current also will be little more than 20 times, and the size that is turned off the shunt capacitance of pipe does not change, so be turned off the U of pipe _CEVoltage is difficult to rise to the E value, and another pipe in the then same brachium pontis just is difficult to realize that no-voltage is open-minded that this clearly shows in figure (two).In figure (two), Q when the oc line segment is underloading ₄Pipe u _CE4(t) ascending curve is up to t _Q3Constantly, it also rises seldom, at t _Q3Constantly, Q ₃Still there is a sizable U at the pipe two ends _DcVoltage (this U in fact _DcVoltage promptly is t _Q3Moment Q ₃U on the pipe _C3Magnitude of voltage, the height that c is ordered then is t _Q3Moment Q ₄U on the pipe _C4Magnitude of voltage), because U _C3Voltage very high, this will produce very big turn-on consumption.

Referring to figure (), if Q ₃When pipe is opened, capacitor C ₃Go up and also have U _C3Voltage then is stored in capacitor C ₃In energy C ₃U _C3 ²/ 2 will all consume at Q ₃In pipe and the connecting line,,,, also can make Q in the time of seriously so can form very big surge current near short-circuit condition because of being that to be in impedance very little basically ₃Pipe damages.

Generally speaking, capacitor C two ends in parallel with the master control pipe before the master control pipe is opened also have voltage U, then open the turn-on consumption of this master control pipe and will represent with following formula: $W_{\mathrm{ON}}=\frac{{\mathrm{CU}}^2}{2}-----\left(2\right)$

Obviously, C is littler, and turn-on consumption is just little, but the front speak of, consider that from the turn-off power loss of full load it is suitable big that C wants, thus contradictory, be illustrated by figure (two) more now.

The oabd curve is full load U among the figure (two) _CE4The track that rises, it is steeper, so turn-off power loss is bigger, in order to reduce turn-off power loss, should strengthen electric capacity.Make move to right back as scheme shown in (four) of a point if strengthen electric capacity, being fully loaded with turn-off power loss can descend greatly, however the U during underloading _CE4(oc represents with line segment) is difficult to rise U more _DcNearly approximate E value.Again because electric capacity strengthens (common C ₃=C ₄, C ₄Strengthen C ₃Strengthen too), then this moment is because of C ₃In energy storage C ₃U _C3 ²/ 2 is bigger, conducting this moment Q ₃Great surge current will be arranged, might make Q ₃Pipe can not bear and burn.

Above analysis be to turn-off Q during at underloading ₄Or Q ₃Analysis and explanation, if to turn-offing the Q of lagging leg ₁Or Q ₂Guan Eryan is owing to turn-off Q ₁Or Q ₂After, its U _CEThe rise of voltage is to belong to the afterflow of boosting, to C ₁Or C ₂In the time of charging, also to export energy to load, simultaneously also will be to additional power source E feedback energy, so need consume L _SIn more energy storage, and L during underloading _SIn energy storage to reduce more than 400 times at least than full load, so, turn-off Q during underloading for lagging leg ₁Or Q ₂, its U _CEThe rise of voltage is than turn-offing Q ₃Or Q ₄The Shi Gengwei difficulty, thus the firm rise of oc line segment is soon, just because of L _SEnergy storage approach exhaustion and hang down into zero or very low numerical value shown in the oc ' curve among figure (two) and the figure (four), is then opened Q ₁Or Q ₂Loss will be bigger also, this is the distinctive phenomenon of lagging leg.

Solve the problem of above-mentioned existence, the most frequently used method has two kinds:

1. half-way house

Half-way house still shown in figure (two), is promptly selected the C of some intermediate values for use, allows full load oa line segment steep slightly, allow it that slightly bigger turn-off power loss is arranged, do not have turn-on consumption but can win full load, and allow it that slightly bigger turn-on consumption is arranged during underloading, and have only very little turn-off power loss.This is the most common present operating state that arrives, this is the utilization of full-bridge phase-shifting resonance circuit reduced levels, its reality has only solved a fully loaded lossless problem of opening, and the turn-on consumption of fully loaded turn-off power loss and underloading is all big slightly, and this operating state approximately can make the full-bridge phase-shifting resonance high frequency power module obtain 88%～90% efficient.

2. inductance compensation scheme

This scheme promptly adopts bigger electric capacity still to scheme (two) on the half-way house basis, make full load U _CERising a little slow slightly, reducing turn-off power loss, and when underloading, then rely on the energy storage of an extra pulsactor that increases, to improve the oc line segment, make U _DcReduce, the turn-on consumption when reducing underloading, its circuit are still as figure () shown in, but L at this moment _SBe the leakage inductance of main transformer itself and the value of the pulsactor merging that adds.

Outer coilloading is a pulsactor, rather than the main cause of a linear inductance is: when underloading, MN branch road operating current is very little, outer coilloading does not enter saturated, so very big inductance value is arranged, thereby more relatively energy storage arranged, when arbitrary master control device turn-offs in figure (), can keep in the longer time the existing of freewheel current that (note: it only is to have prolonged the time that freewheel current exists, can not increase the size of freewheel current), can make among figure (two) and the figure (four) because of L _SEnergy storage is not enough and cause sagging rise of underloading oc ' curve second half section, reverts to the height that oc should reach, then at t _Q3The Q of conducting constantly ₃The turn-on consumption of pipe can reduce, but owing to add the introducing of pulsactor, to on pulsactor, produce a sizable voltage drop, make the main transformer original edge voltage that sizable falling be arranged, though can be wide constant to guarantee output voltage by transferring automatically, if but the inductance value of pulsactor is excessive, duty ratio is used up, and just needs the change main transformer turn ratio just can keep rated voltage output.This has just limited the maximum induction amount that adds pulsactor.

When load increases the weight of, the main transformer operating current strengthens, by the electric current increasing of pulsactor, owing to be pulsactor, after electric current increases, the inductance value of pulsactor significantly descends, and the full load pulsactor should enter saturated fully, and its induced voltage should drive in zero, so no pressure drop, so the introducing of pulsactor, the afterflow ability during only to underloading plays humidification, and full load is inoperative substantially.Very big pressure drop is arranged on the pulsactor during underloading, and full load does not have pressure drop substantially on the pulsactor.

Owing to adopted bigger electric capacity to reduce the turn-off power loss of full load, turn-on consumption when adopting pulsactor with the minimizing underloading, so adopt the scheme that adds pulsactor, its efficient can make the efficient of full-bridge phase-shifting resonance high frequency power module reach about 90% to 92% than half-way house height.

The weak point that adds the pulsactor compensation scheme is:

1. it can only prolong holding time of freewheel current, turn-off the master control pipe when making underloading after, its U _CESagging being compensated that voltage causes because of leakage inductance energy storage deficiency, but it can not increase the size of freewheel current.

2. the afterflow ability when it can be to underloading plays humidification, but is cost with the operating voltage that reduces the former limit of main transformer reality, and this just makes the inductance value size of outer coilloading be restricted, and just it is limited to the compensation effect of afterflow ability.

Further reduce the loss of full-bridge phase-shifting resonance power module again, improve its efficient, go back neither one and consider relatively comprehensively and efficient ways.

The present invention is then based on following design:

1. in order further to improve the efficient of full-bridge phase-shifting resonance Switching Power Supply again, be exactly in fact to guarantee under the full load conditions, under the preceding topic that each master control Guan Junneng realization no-voltage is opened, reduce the turn-off power loss of each master control pipe under the full load conditions as far as possible.

2. reduce the turn-off power loss of each master control pipe full load, in the full-bridge phase-shifting resonance circuit, effective method is exactly the capacity that strengthens the electric capacity in parallel with the master control pipe, just a point of the middle oa line segment of figure (four) further will be moved to right again, be the master control pipe to be closed have no progeny its U in essence _CEVoltage rises to the time t that E experiences _aLonger, shown in figure (five), now set t _aFor:

t _a=(1.2～2.0) t ₀(3) t in the formula ₀After the shutoff of master control device, electric current drops to for zero time, after the master control device is selected, and t ₀Value can in handbook, find.For low speed devices, t ₀Be worth bigger, t _aCan select (1.2～1.5) t for use ₀About.To high speed device, t ₀Be worth less, t _aCan select (1.5～2.0) t for use ₀About.

3. if t _aBe arranged in 1.5t ₀The place then shown in figure (five), is no-voltage conducting, then its ON time t in order to guarantee another pipe in the brachium pontis really _QMust be at t _aAfterwards, now set the ON time t of this pipe _QFor

t _Q≥2t ₀?????????????????????(4)

4. determining t by afore mentioned rules _aAnd t _QAfterwards, fully loaded loss just can further descend, and efficient then can be further enhanced.But, must make oc line segment (U when being underloading because the electric capacity in parallel with the master control pipe is further strengthened _CEAscending curve) be difficult to more rise, shown in figure (five).Conduction loss during underloading becomes bigger, and this is flagrant, must manage to make the oc line segment to lift, to reduce the turn-on consumption of underloading.For this reason, this patent invention has designed a special method, make the oc line segment be raised to oc ' position, and c ' voltage will reach more than the 0.6E at least, just U _{Dc '}Size will be below 0.4E, simultaneously the position of oa line segment can remain on again near its original position constant substantially, shown in figure (five), if accomplished this point, then:

(1) turn-off power loss of full load is very little, and the turn-on consumption of full load is again zero simultaneously.

(2) turn-off power loss during underloading was original just very little, and the turn-on consumption during underloading reduces greatly again and (drops to and have only simultaneously

Or it is littler).

Satisfied above two, just can make the full-bridge phase-shifting resonance circuit working, promptly be implemented in the very wide loading range and can both obtain higher efficient at a kind of better state.

Key issue just is how to raise the oc line segment to oc ' time now, and makes the oa line segment maintain former invariant position substantially, has solved this problem, just can make the operating state of full-bridge phase-shifting resonance circuit reach a higher boundary.

From in essence, under the constant situation of capacitance size, make the oc line segment be lifted to oc ' position, only way can only be turn-off the master control pipe when underloading after, can to the master control pipe electric capacity in parallel with bigger charging current, to force U _CEIt is faster to rise, full load turn-off behind the master control pipe to the master control pipe the too much increase that then do not have of the charging current of electric capacity in parallel, so it is constant substantially that the oa line segment is remained near the original position.The specific requirement of this design, available figure (six) describes.

Figure (six) (a) be illustrated in strengthen the master control pipe behind the electric capacity in parallel, when not taking any measure, under the big or small loading condition of various differences, U _CEThe track that voltage rises.Its oa line segment represents under the full load conditions to turn-off U behind the master control pipe _CEThe track that rises, the time that its voltage rises to E is t _a, U behind the shutoff master control pipe when oc line segment is then represented underloading among the figure _CEThe track of change in voltage, because shunt capacitance uses very greatly, so during underloading, the oc line segment is smooth basically, promptly the voltage difference of c point representative mostly is not zero, thereby great turn-on consumption is arranged, and is about CE ²/ 2.

The state that on behalf of the distinctive design of the present invention, figure (six) (b) then to reach.Oa line segment and figure (six) the oa line segment position in (a) is roughly the same among the figure six (b), represent full load shutoff master control pipe after, U _CEThe track that voltage rises, different is that the oc line segment is smooth after turn-offing the master control pipe under the underloading situation, oc ' line segment is then at identical t _QConstantly risen to more than the 0.6E, this just requires can have when underloading a very big charging current to the charging of master control pipe shunt capacitance, makes at t _QC ' can reach more than the 0.6E constantly.

Careful comparison diagram (six) is (a) and scheme (six) and (b) can find:

1. during underloading, the percentage maximum of lifting on the oc line segment that oc ' line segment compares need increase the percentage maximum of charging current to shunt capacitance when that is to say underloading.

2. when 20% load, figure (six) is the middle 20%R that represents (b) _LCurve ratio figure (six) represent 20%R in (a) _LCurve on the percentage lifted reduce to some extent, when that is to say 20% load, need increase the percentage of charging current to shunt capacitance, descend to some extent during than underloading.

3. in like manner: during 40% load, figure (six) is the middle 40%R that represents (b) _LCurve ratio figure (six) represent 40%R in (a) _LCurve on the percentage lifted further reduce again, the percentage of the charging current that need increase to shunt capacitance when that is to say 40% load further descends again to some extent.So analogize, as can be seen figure (six) (b) in, along with increasing the weight of of load, represent each bar curve of load underloading more and more intensive, that is to say and increase the weight of along with load that need to increase the percentage of charging current to shunt capacitance more and more little.

4. full load, figure (six) the oa line segment and the position of the oa line segment of figure (six) in (b) in (a) is roughly the same.That is to say that full load need not to increase charging current to shunt capacitance.

In order to more clearly understand this requirement, contrast that can be in quantity, roughly illustrate the state of its work:

1. referring to figure (), arbitrary master control pipe closes has no progeny, because L is arranged _SExistence, freewheel current promptly is the operating current of MN branch road before turn-offing, and the operating current of the operating current of full load during than underloading is in general big more than 20 times, so full load L _SIn energy storage L _SI ²/ 2 energy storage during than underloading are big at least more than 400 times, so full load turn-offs master control pipe, its U _CEVoltage is big because of the value of freewheel current, L _SEnergy storage is many again, reaches the E value so be easy to rise.

2. during underloading, the capacitance size that is connected in parallel on the master control pipe does not change, so electric capacity was full of in the same time, required electric current should not change yet, but the operating current during underloading is at least littler 20 times than the operating current of full load, so turn-off the master control pipe when underloading after, to in the same time, shunt capacitance be charged to E, at least will additionally manage increases about charging current more than 20 times, if charge to 0.6E, then will manage to increase about charging current more than 10 times at least.

3. now in order further to reduce fully loaded turn-off power loss, again shunt capacitance is further strengthened, because only in this way could satisfy t _a〉=1.5t ₀Requirement, but after further strengthening shunt capacitance, t _QThe position do not change, then during underloading if still require at t _QConstantly shunt capacitance is charged to more than the 0.6E, then charging current is also big again, increases by more than 10 times to 20 times at least, just can make this shunt capacitance charge to 0.6E.

4. yet full load turn-offs the master control pipe, basically need not increases charging current to shunt capacitance, so the charging current of this increase is that inverse proportion changes with the weight variation of load, the amplitude size that changes reaches more than 10 times to 20 times more than, obviously only relies on one to add pulsactor and can't finish this requirement.

Design provided by the invention and embodiment can effectively realize above-mentioned requirements, promptly a kind of constant ractive current compensation full-bridge phase-shifting resonance soft switch technique, by master control device Q ₁, Q ₂, Q ₃, Q ₄And main transformer T constitutes the main circuit of full-bridge phase-shifting resonance high frequency switch power, Q ₁, Q ₂Be the lagging leg of this circuit, Q ₃, Q ₄Be the leading-bridge of this circuit, Q ₁Emitter and Q ₂Collector electrode link to each other Q ₃Emitter and Q ₄Collector electrode link to each other Q ₁, Q ₂Connected node M and Q ₃, Q ₄Connected node N between be connected with one and contain main transformer T and leakage inductance thereof or add inductance L _SBranch road, entire circuit is implemented control to finish power conversion by external control logic circuit; Feature of the present invention is: change in the aforementioned switches electric power main circuit between node M N main transformer T and leakage inductance thereof or add inductance L _SExciting curent I on the branch road of living in _B, make it increase to constant reactive current I _B0Level, i.e. I _B0=(0.6～1) I ' ₂(I ' ₂Be load current) do not change simultaneously I again _B0Phase place lags behind applied voltage E90 ° character, and magnetic flux Φ _BSize constant substantially or slightly reduce, making increases I _BThe former limit of back main transformer total current can increase when underloading and reaches more than 10 times, and full load only increases more seldom; This change is by adjusting main transformer T magnetizing inductance amount L _B0Realize; Particularly, L _B0Change be at its former limit winding N ₁Under the situation constant or that slightly reduce, make its iron core increase air-gap l, finally make L _B0Reach the required inductance value of following formula:

In the formula: E is the applied voltage of phase shift bridge circuit, T ₁Be the cycle, I _{On average}Be phase shift bridge circuit power input average current.The air-gap l that opens opens on E sections core center pillar on the described main transformer T, is increased to required I to guarantee exciting curent _B0Value, this air-gap maximum can reach more than the 1cm.Master control device Q ₁～Q ₄Emitter and inter-collector be parallel with capacitor C respectively ₁～C ₄, it is characterized in that: C ₁～C ₄Capacitance than this main circuit common usage be big, specifically be according to formula C=I ₁(1.2～2.0) t ₀/ 2E sets.In the formula: I ₁Total current during for the former edge work of main transformer, t ₀Be the master control device turn-off time.Below the invention will be further described.

An appendiron core transformer under the sinusoidal voltage effect, if be operated in the linear zone of iron core BH curve, its equivalent electric circuit can be represented with figure (seven).

In figure (seven):

r ₁, r ₂' be respectively the copper resistance of primary and secondary;

L _S1, L _S2' be respectively the leakage inductance of primary and secondary coil;

r _gIron loss resistance (representing the equivalent resistance of magnetic hysteresis loss and eddy current loss) for core material;

L _BRepresent the magnetizing inductance of iron core;

I _gIt is the active current that iron loss causes;

I _BBe the required magnetizing current of magnetizing inductance, it and applied voltage have 90 ° phase difference,

Be a reactive current, absorb energy to set up magnetic field, demagnetization from power supply during magnetization

The time, then send energy back to power supply.

Because high-power transformer, in general, copper loss, iron loss are all very little, and the pressure drop that causes on former limit only accounts for the very little part of original edge voltage, adds the pressure drop that leakage inductance causes, its proportion is still very little, as approximate calculation, can ignore, then the equivalent electric circuit of appendiron core transformer just can (c) be represented with figure (seven), now (c), research work electric current I from figure (seven) ₁With magnetizing current I _BRelation.

The polar plot that at first will scheme (seven) circuit (c) draw as figure (eight) (a) shown in, U among the figure ₁Be applied voltage, I _BBe magnetizing current, Φ _BBe the work magnetic flux, U ₂Be inferior polygonal voltage, reflexing to former limit is U ' ₂, existing U ' ₂=U ₁I ₂Be inferior limit load current, reflexing to former limit is I ' ₂, then former limit total current

Promptly

Because magnetizing current I _BUsually all very little, generally be roughly full load I ₂' below 5%, i.e. I ₂' (expiring)  20I _B, because I _BValue very little, so when load variations, no matter be fully loaded or underloading, I ₁With I ₂' difference very little, as figure (eight) (b) shown in.

If we look I ₂' 1/20 be underloading, i.e. I ₂' (expiring)=20I ₂' (gently) then can be similar to and think I ₂' (gently)  I _B, (b) can get by figure (eight):

Now if take certain any special measures with I _BIncrease to I _B0, and do not change I _B0Phase place lags behind the character of 90 ° of applied voltages, and magnetic flux Φ _BBig I constant, even also can reduce, i.e. Φ _B0≤ Φ _B, I then _BIncrease to I _B0After polar plot can with figure (eight) (c) represent I among the figure ₂' (gently) and I ' ₂The value of (expiring) is constant, but I ₁(gently) and I ₁The big young pathbreaker of (expiring) changes, respectively with I ₁₀(gently) and I ₁₀(expiring) expression, but the row formula is as follows:

Modern with I _BIncrease to I _B0,, establish I according to the front requirement _B0Be I _B(12～20) doubly, then because of I ₂' full  20I _B=20I ₂' (gently), so

=(0.6～1) I ₂(5) the present ' (expiring) is got I _B0=0.8I ₂' (expiring),, it is equivalent to I _B0Be I _B16 times, then: $=\sqrt{\frac{1+{16}^2}{1+1}}=11.34$ If this formula explanation is with I _BIncrease to 16I _BUnder the situation, the former limit of transformer total current will be not increase I during underloading _BThe time 11.34 times of transformer former limit total current.

Take another look at the contrast under the full load conditions: $=\sqrt{\frac{{20}^2+{16}^2}{{20}^2+1}}=1.279\stackrel{.}{=}1.28$ These calculation specifications, at full load if with I _BIncrease to 16I _B, the main transformer primary current is not increase I _BThe time 1.28 times of the transformer primary current, promptly only increased 28%, do not have what marked change comparatively speaking.

Above analytical calculation shows, increases I _BAfter, the former limit of transformer total current increases when underloading greatly, can reach tens times, and has only increased seldom little by little at full load, and this has just satisfied forenamed requirement.

Certainly, above analysis is that hypothesis transformer applied voltage is a sine voltage, so can analyze and calculate with polar plot, if but be operated in square wave or pulse width modulated wavy attitude, just can not be described with polar plot, but more than analyze the basic principle and the notion of institute's foundation, still can use for reference, but should be based on graphical analysis.

The present invention of let us concern now is the problem that increases substantially that how to realize more than ten times of magnetizing current energy.

In order to increase the simplest method of magnetizing current is exactly to reduce the number of turn of former limit coiling, because square being directly proportional of inductance value and number of turns, so after the number of turn minimizing, inductance value will reduce greatly, magnetizing current must increase considerably, but in this case, the work magnetic flux in the iron core will be by Φ _BRise to Φ _B', and Φ _B' enter dark saturation region already, as figure (nine) (a ₂) shown in, if be connected to time limit winding this moment, its induced voltage will sharply descend.Simultaneously, because Φ _B' enter saturation region, Φ _B' numerical value surpassed the maximum that operate as normal allows, because of core loss is directly proportional with (1.6～2.0) power of Φ, so core loss will sharply increase sharply, iron core will seriously generate heat, so relying on the reduction number of turns is impracticable with the scheme of obtaining the big capacity magnetizing current more than 10 times, also is unallowed.The design that this patent invention provides can make I _BIncrease more than 10 times and reach I _B0Afterwards, Φ _B0Can maintain former Φ _BNumerical value on constant, so the iron loss of magnetic core and caloric value do not have anything to change, even can also make Φ _B0Less than Φ _B, promptly iron loss can also reduce, and meanwhile, does not change I again _B0Phase place lags behind the character of 90 ° of applied voltages.This method adds air-gap l in the magnetic core cross section exactly, as figure (nine) (b ₁), here the air-gap l that is added, be far longer than normal ranges, it in addition can reach more than 1 centimeter, this directly exports high-power appendiron core transformer for requiring based on high efficiency, add so big air gap, must think one unconventional, rare behave, because under regular situation, establish very big air gap newly or further reduce number of turns, transmit powerful appendiron core transformer for requiring with high efficiency, usually all be considered to be a forbidden zone, and quilt is titled with " transformer loss increase ", " transformer heating ", too much lose duty ratio " and the defective of " efficient descends greatly " or the like " generally acknowledging " and not adopted by people.Yet the birth of an invention is based upon people exactly generally never to be expected, or thinks a kind of breakthrough on the incident that can not set up, thereby has founded a brand-new notion, has promoted advancing of things.

In figure (nine), if do not add air-gap, then at applied voltage U ₁Effect needs only very little magnetizing current down, just can obtain specified work magnetic flux Φ _B, as figure (nine) (a ₂) shown in.Under normal circumstances, set up same work magnetic flux Φ _BIf, required magnetizing current I _BLittler, iron core then is described better, or transformer performance is better, this is normal idea.

If require U ₁Constant, work magnetic flux Φ _BAlso constant, but wish magnetizing current I _BIncreasing more than more than 10 times, then obviously is a very special design.Method provided by the invention is exactly to increase the air-gap l of super quantity, because the magnetic resistance of the air-gap magnetic resistance in the magnetic core loop, so will form big magnetic flux Φ equally _B(existing Φ _B0=Φ _B) must need bigger magnetomotive force N ₁I _B0(N ₁I _B0Also claim the ampere circle).At N ₁When constant, then mean need be bigger magnetizing current I _B0, as figure (nine) (b ₂) shown in.Because appendiron core transformer has increased after the very big air-gap, (B-H) curve of its equivalence so be easy to find a suitable air-gap, makes magnetizing current reach the I of regulation by linearization(-sation) _B0The time, Φ _B0Also equal Φ just _B, perhaps Φ _B0More less than Φ _B, then can guarantee the unlikely increase of iron loss of iron core, in addition I _B0Remain a reactive current, with U ₁90 ° phase difference is still arranged, so just realized magnetizing current I _BIncrease more than 10 times purpose.Because I _B0Being magnetizing current, is applied voltage U ₁Function, as applied voltage U ₁Fixed, the size of air-gap l is fixed, then I _B0Size also just by relative fixed, no matter and load be heavily to be light, I _B0The few of substantially variation of value, so after turn-offing the master control device, it is a constant reactive current component in the total current of main transformer, this figure (eight) (c) in, can clearly demonstrate this characteristics, the main transformer total current there is no much variations when its existence made heavy duty, and when underloading, but can make the main transformer total current increase by tens times, play strong compensating action.Because I _B0Be a constant reactive current component, so this patent invention called after " constant ractive current compensation phase-shifting resonance soft switch technique ".This is the key feature place of this patent innovation and creation design.

According to above-mentioned design, the obtainable effect of the present invention is as follows:

1. owing to arrange master control pipe Q ₁～Q ₄Have no progeny in the pass, its U _CEVoltage rises to the time t of E _aEqual (1.2～2.0) t ₀About, for most of low pressure drops inexpensive field controller at a slow speed, t ₀Greatly about about (0.6～1.0) μ s, t then _aMaximum generally all can be arranged in more than the 1 μ s, if supply voltage E is 500 volts, then the master control device dV/dt value of bearing is: $\frac{\mathrm{dV}}{\mathrm{dt}}=\frac{500}{1}\frac{V}{\mathrm{\&mu;s}}=500V/\mathrm{\&mu;s}$

As seen, the t that adopts the present invention to set _aThe value scope, then no matter the master control pipe is fast device or slow device, the value of its dV/dt is general equal to be guaranteed in every microsecond below 500 volts.

2. because master control pipe Q ₁～Q ₄Have no progeny in the pass, U _CERise to the chronic of E, can reach more than the 1 μ s, because climbing speed is very slow, then over control is also suppressed basically fully, and when just the master control pipe turn-offed, surge voltage no longer occurred basically.

3. during owing to underloading, the present invention has set a very big reactive current I _B0, open master control pipe moment, its U when making underloading _CEValue drops to below the 0.4E, so the surge current when opening the master control pipe significantly reduces, and when 30% above load, then all is that no-voltage is open-minded, and surge current just equals zero substantially.

4. because closing, the master control pipe has no progeny U _CEThe time that rises to E can accomplish more than the 1 μ s, so turn-off power loss descends greatly [referring to table ()], simultaneously again because set a very big reactive current component I _B0So the turn-on consumption during underloading also descends greatly, its total effect is, loads on quite wide scope, can obtain very high efficient, and the power module that adopts this soft switch technique to make can make the efficient of module complete machine reach more than 95% generally speaking.

Above-mentioned four just high frequency switch power manufacturer fail the technical barrier of fine solution so far always, technical scheme provided by the invention solves these problems targetedly, and the existing index of high frequency switch power is greatly improved.

The present invention is applicable to communication high-frequency switching power supply module, High frequency power operating power module, high-frequency induction welder power module, and with 24 volts, 48 volts, 60 volts, 110 volts, 220 volts direct currents be output as the basis high power work power supply occasion, application surface is very wide.

This Figure of description is described as follows:

Figure (one) is a full-bridge phase-shifting resonance high frequency switch power main circuit electrical schematic diagram.

Figure (two) is Q in the main circuit ₄Pipe is turn-offing front and back, the track of voltage, electric current t variation in time on each electrode.

Figure (three) works as Q ₄The capacitor C that pipe is in parallel ₄Adopt different numerical value right, turn-offing Q ₄Behind the pipe, voltage U _CE4The voltage ascending curve of the different gradients that may have.

Figure (four) works as Q ₄The capacitor C that pipe is in parallel ₄After the increasing, turn-off Q ₄Before and after the pipe, the track of voltage, electric current t variation in time on each electrode.

Figure (five) works as Q ₄The capacitor C that pipe is in parallel ₄After further strengthening, turn-off Q ₄Before and after the pipe, the track of voltage, electric current t variation in time on each electrode.

Figure (six) is after strengthening master control pipe shunt capacitance (a), when not taking any measure, under the big or small loading condition of various differences, turn-off the master control pipe after, voltage U _CEThe track that rises.

Figure (six) is after strengthening master control pipe shunt capacitance, to turn-off the master control pipe under the big or small loading condition of various differences (b), if adopt the specific design of this patent invention can expect the U that reaches _CEThe voltage rising trace.

Figure (seven) is the appendiron core transformer under the sine voltage effect.

Figure seven (a) is the former limit of appendiron core transformer, inferior limit winding and electric current and voltage thereof.

Figure seven (b) is the equivalent circuit diagram of appendiron core transformer.

Figure seven (c) is appendiron core transformer simple equivalent circuit figure.

Figure (eight) is under the sinusoidal voltage effect, the polar plot of appendiron core transformer.

Figure (eight) is voltage, the current phasor figure of appendiron core transformer simple equivalent circuit (a).

Figure (eight) is an appendiron core transformer (b) when underloading and heavy duty, the polar plot of voltage, electric current in the simple equivalent circuit.

Figure (eight) is that appendiron core transformer increase reactive current component reaches I (c) _B0After the value, the polar plot of voltage, electric current in the simple equivalent circuit when underloading and heavy duty.

Figure (nine) is magnetization curve and the polar plot of appendiron core transformer when not having air gap and air gap being arranged.

Figure nine (a ₁) be no air-gap iron core transformer.

Figure nine (a ₂) be the magnetization curve of no air-gap iron core transformer.

Figure nine (a ₃) be no air-gap iron core transformer voltage, current phasor figure.

Figure nine (b ₁) be the appendiron core transformer that air gap is arranged.

Figure nine (b ₂) be that the appendiron core transformer magnetic flux of air gap and the relation curve of magnetizing current are arranged.

Figure nine (b ₃) be appendiron core transformer voltage, the current phasor figure that air gap is arranged.

Figure (ten) is average current and the pulse width modulated ripple electric current that power supply is exported to the phase shift bridge.

Figure (11) is main transformer applied voltage U ₁With load current I ₂' and magnetizing current I _B0The instantaneous value oscillogram.

The specific design implementation method of " soft switch technique " that relevant the present invention is specific is as follows:

1. by figure (one) circuit, power output as requested and specified input voltage E select the core material size according to a conventional method, and determine its net sectional area S (cm ²), press B _m=800～1000 Gausses design the former limit of transformer number of turns N ₁, N ₁Calculating formula is:

E＝4N ₁B _mSf·10 ^-8???????????????????(6)

Wherein: E is applied voltage V, B _mWork magnetic flux density G, S net sectional area cm ²,

F operating frequency Hz

2. inferior limit number of turn N ₂Can be according to the output voltage U of inferior limit needs ₂Calculate, because of being added with bigger air-gap, coupling coefficient slightly reduces, so the inferior limit number of turn that calculates should append about 2% as remedying.

3. according to the watt level of output, can obtain the average current value I that power supply E should provide _{On average}(establishing efficient in the calculating is 95%)

If go here and there a direct current ammeter, the value of its indication is this I between power supply E and phase shift bridge _{On average}Value, I _{On average}It is an active current of power branch output.

4. ask I ₂' and determine I _B0:

Because applied voltage E should have ± 15% draw partially, so under typicalness, the real work of phase shift bridge is approximately 0.65 state in duty ratio, and then the active current that provides of power supply E is actual is that a pwm pulse is transferred wide ripple, and the big I of this pulse width modulated ripple electric current is tried to achieve by figure (ten):

Obtain I ₂' afterwards,, set I by aforementioned design _B0=(0.6～1) I ₂', I then _B0=(0.6～1) 1.538I _{On average}=(0.923～1.538) I _{On average}(9) if get I _B0=0.8I ₂', then: I _B0=0.81.538I _{On average}=1.23I _{On average}

5. ask L _B0:

Referring to figure (11), connect the calculating formula of the electric current initial slope of DC power supply according to inductive circuit, can write out following formula: $I_{\mathrm{<figure-callout\; id="0"\; label="B"\; filenames="A9812166800272.png,A9812166800281.png"\; state="\{\{state\}\}">B</figure-callout>}0}=\frac{\mathrm{<figure-callout\; id="0"\; label="E\; L\; B"\; filenames="A9812166800272.png,A9812166800281.png"\; state="\{\{state\}\}">E</figure-callout>}}{L_B}\&CenterDot;0.65\&CenterDot;\frac{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A9812166800271.png"\; state="\{\{state\}\}">T</figure-callout>}}_1}{4}-----\left(10\right)$

If I _B0=0.8I ₂', then:

At former limit winding N ₁Under the constant situation, iron core increase air-gap l makes former limit inductance L _B0The value that reaches formula (11) calculating gained gets final product (can allow 10% deviation).

6. ask C ₁, C ₂, C ₃, C ₄Value:

Generally speaking, C ₁=C ₂=C ₃=C ₄, its calculation procedure is as follows:

(1) according to the power output size, and the selected used master control device of input voltage, output voltage, and finds its turn-off time t by handbook ₀

(2) establish full load, the time that electric capacity is charged to voltage E is t _a, t _aSize is appointed as according to formula (3): t _a=(1.2～2.0) t ₀(3) ask maximum operating currenbt I ₁: according to figure (11), I ₂' with U ₁Homophase,

Constantly the master control pipe turn-offs, the total current I in this transformer moment ₁For: I ₁=I ₂'+I _B0=I ₂'+(0.6～1) I ₂I is now got in ' (12) _B0=0.8I ₂', I then ₁=1.8I ₂'=1.81.538I _{On average}=2.768I _{On average}(13)

(4) ask C ₁～C ₄Value:

After the master control device turn-offed, the freewheel current of transformer branch road MN was I ₁, this freewheel current one tunnel is through last brachium pontis capacitor C ₃(or C ₁), one road warp is brachium pontis C down ₄(or C ₂) provide discharging current and charging current to electric capacity.Because the electric capacity of upper and lower bridge arm equates, so one tunnel charging charge amount wherein, discharge charge amount also inevitable and another road is equal, thereby can think that wherein one tunnel mean charging current must equate with the average discharge current on another road, all is approximately I ₁1/2nd, can be similar to thus and obtain C ₁～C ₄Value.Cause: $\frac{\mathrm{dQ}}{\mathrm{dt}}=C\frac{\mathrm{du}}{\mathrm{dt}}$ Promptly $\frac{1}{2}{I}_1=C\frac{E}{t_a}$ $C=\frac{I_1{t}_a}{2E}=\frac{I_1(1.2~2.0){\mathrm{<figure-callout\; id="0"\; label="t"\; filenames="A9812166800272.png,A9812166800281.png"\; state="\{\{state\}\}">t</figure-callout>}}_0}{2E}-----\left(14\right)$ Now get t _a=1.5t ₀, I _B0=0.8I ₂', then

During actual fabrication, because of C ₁, C ₂System is operated in lagging leg, belongs to the afterflow of boosting when charging, needs more energy, for guaranteeing the height of charging voltage, and can be with C ₁, C ₂Value compare C ₃, C ₄Reducing 10%～20% is advisable.

At last; need particularly point out; the aforementioned calculation method has satisfied the peculiar inventive concept of the present invention; but it only is above-mentioned some computational methods and the calculating formula of listing that protection scope of the present invention obviously is not limited to; also comprise those skilled in the art for satisfying the alternative of the extended conspicuous various derivations of the distinctive inventive concept of the present invention, and adopt various different computational methods of supporting selection for satisfying this design.For example on the distinctive basis that the constant reactive current is set of the present invention, additionally add a little pulsactor again, because reactive current increases greatly during underloading, then the effect of this pulsactor is just given full play to, compensating action is also promoted, but this is apparent that and belongs to extended a kind of derived scheme on the invention design basis.

Claims (3)

1, a kind of constant ractive current compensation full-bridge phase-shifting resonance soft switch technique, by master control device Q ₁, Q ₂, Q ₃, Q ₄And main transformer T constitutes the main circuit of full-bridge phase-shifting resonance high frequency switch power, Q ₁, Q ₂Be the lagging leg of this circuit, Q ₃, Q ₄Be the leading-bridge of this circuit, Q ₁Emitter and Q ₂Collector electrode link to each other Q ₃Emitter and Q ₄Collector electrode link to each other Q ₁, Q ₂Connected node M and Q ₃, Q ₄Connected node N between be connected with one and contain main transformer T and leakage inductance thereof or add inductance L _SBranch road, entire circuit is implemented control to finish power conversion by external control logic circuit; Feature of the present invention is: change in the aforementioned switches electric power main circuit between node M N main transformer T and leakage inductance thereof or add inductance L _SExciting curent I on the branch road of living in _B, make it increase to constant reactive current I _B0Level, i.e. I _B0=(0.6～1) I ₂' (I ₂' be load current), do not change I simultaneously again _B0Phase place lags behind applied voltage E90 ° character, and magnetic flux Φ _BSize constant substantially or slightly reduce, making increases I _BThe former limit of back main transformer total current can increase when underloading and reaches more than 10 times, and full load only increases more seldom; This change is by adjusting main transformer T magnetizing inductance amount L _B0Realize; Particularly, L _B0Change be at its former limit winding N ₁Under the situation constant or that slightly reduce, make its iron core increase air-gap l, finally make L _B0Reach the required inductance value of following formula:

In the formula: E is the applied voltage of phase shift bridge circuit, T ₁Be the cycle, I _{On average}Be phase shift bridge circuit power input average current.

2, full-bridge phase-shifting resonance soft switch technique as claimed in claim 1 is characterized in that: the air-gap l that opens opens on E sections core center pillar on the described main transformer T, is increased to required I to guarantee exciting curent _B0Value, this air-gap maximum can reach more than the 1cm.

3, full-bridge phase-shifting resonance soft switch technique as claimed in claim 1, its master control device Q ₁～Q ₄Emitter and inter-collector be parallel with capacitor C respectively ₁～C ₄, it is characterized in that: C ₁～C ₄Capacitance than this main circuit common usage be big, specifically be according to formula C=I ₁(1.2～2.0) t ₀/ 2E sets.In the formula: I ₁Total current during for the former edge work of main transformer, t ₀Be the master control device turn-off time.

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