CN104202862B - Single-stage type LED drive power supply without electrolytic capacitor - Google Patents

Abstract

The invention discloses a single-stage type LED drive power supply without an electrolytic capacitor. The single-stage type LED drive power supply without the electrolytic capacitor is an AC/DC converter in essence, and the single-stage type LED drive power supply without the electrolytic capacitor is composed of an input filter rectification circuit, a fly-back primary switch circuit, an auxiliary winding full-bridge bidirectional circuit and a secondary rectification filter circuit. The single-stage type LED drive power supply without the electrolytic capacitor realizes the power factor correction through fixing the duty ratio of a main switch MOS tube Q1 and works in a current discontinuous mode to avoid the reverse recovery of a secondary diode QR; the main circuit thereof is a fly-back converter which is composed of the part 1, part 2 and part 4, an isolating transformer of the fly-back converter is provided with a winding, the auxiliary winding side uses a bidirectional power flow full-bridge converter to balance the instantaneous pulse difference between the input power and the output power, and the capacitance of an auxiliary energy storage capacitor is reduced through increasing the average voltage and voltage pulse of the auxiliary energy storage capacitor; the single-stage type LED drive power supply without the electrolytic capacitor removes double power frequency alternating current component of the output current, reduces the output filter capacitor capacitance and realizes the small volume and long service life, and the electrolytic capacitor can be substituted by a film capacitor; the output current of the LED drive power supply is constant current.

Description

A kind of single stage type no electrolytic capacitor led driving power supply

Technical field:

The present invention relates to a kind of single stage type no electrolytic capacitor led driving power supply, it belongs to Switching Power Supply especially led and drives Power supply application.

Background technology:

Developing rapidly with human society, energy-consuming demand increases sharply, and energy crisis is increasingly serious.Solve the energy Crisis mainly has two approach, and one of approach is exploitation regenerative resource, reduces the dependence to traditional fossil energy；Another way Footpath is to seek new power-saving technology, reduces the consumption of the energy, improves the utilization ratio of the energy.Wherein illumination is that the mankind consume the energy An importance, traditional illuminating product such as electric filament lamp, fluorescent lamp, high-pressure mercury lamp etc., there is power consumption rate low Serious problems.Therefore reduce the electric energy required for illumination, be beneficial to reduce global energy consumption.In recent years, green energy conservation shines The bright major issue having become countries in the world concern, also more and more urgent to the demand of new type light source.

Led (light emitting diode) light emitting diode relies on its clean and effective, light efficiency height, life-span length, simulation The advantages of natural light, obtain high speed development within several years at this, be widely used in various occasions.One of critically important advantage of led It is that service life is very long, about 30,000～100,000 hours.Traditional led driving power supply input power factor be 1 when, its input current It is to be phase place identical sine wave with its input voltage, the form of therefore its input power is sinusoidal square.And because it is permanent Press load characteristic and need constant-current driving, therefore its output is straight.So its driving power supply needs capacitance very big Storage capacitor comes equal input power and output, adopts electrochemical capacitor this storage capacitor more.And the life-span one of electrochemical capacitor As only 5000 hours, the life-span of led body has 100000 hours, and working life between the two differs greatly, and is therefore electrolysed Electric capacity is the key factor limiting the led driving power supply life-span.And electrochemical capacitor volume is larger, have impact on driving power supply power close The raising further of degree.For this reason, it may be necessary to remove the electrochemical capacitor in led driving power supply.

Content of the invention:

It is an object of the invention to provide a kind of single stage type no electrolytic capacitor led driving power supply, due to led driving power supply work( Rate is less, and output voltage is relatively low, using the simple anti exciting converter of structure as PFC main circuit, by One assists winding is increased on the isolating transformer of anti exciting converter, assists winding side adopts to and fro flow of power full-bridge converter Come balanced input and the instantaneous difference pulsed of output so that output filter capacitor can adopt the less thin-film capacitor of capacitance.

The present invention adopts the following technical scheme that a kind of single stage type no electrolytic capacitor led driving power supply, whole including input filter Current circuit, flyback primary side switch circuit, assists winding full-bridge two-way circuit, secondary current rectifying and wave filtering circuit and isolating transformer t₁；

Isolating transformer t₁It is made up of a primary side winding and two vice-side winding, including isolating transformer former limit inductance l_m And leakage inductance, flyback primary side switch is electrically connected to isolating transformer t₁Primary side winding on, secondary current rectifying and wave filtering circuit and auxiliary Winding full-bridge two-way circuit is connected to isolating transformer t₁Two vice-side winding on；

The filter circuit of input filter rectification circuit 1 is by input filter inductance l₁With input filter capacitor c₁In parallel after series connection In electrical network input two ends composition, the rectifying part of input filter rectification circuit 1 adopts four diode d₁、d₂、d₃、d₄Composition Full-bridge uncontrollable rectifier circuit in parallel is in both ends of filter capacitor；

Flyback primary side switch circuit 2 is by isolating transformer t₁The different name end of primary side winding and master switch mos pipe q₁Drain electrode phase Even form, master switch mos pipe q₁Including its parasitic diode and parasitic capacitance；

Assists winding full-bridge two-way circuit 3 is by first, second auxiliary igbt pipe q_s1、q_s2And first, second auxiliary mos pipe q_s3、q_s4, first, second booster diode d_s1、d_s2And auxiliary energy storage electric capacity c_bComposition, the wherein first auxiliary igbt pipe q_s1With One booster diode d_s1And first auxiliary mos pipe q_s3It is sequentially connected in series, the second auxiliary igbt pipe q_s2With the second booster diode d_s2 And second auxiliary mos pipe q_s4Form two brachium pontis parallel connections after being sequentially connected in series, and be connected in parallel on isolating transformer t₁Second pair Side winding two ends, isolating transformer t₁The different name end of second vice-side winding and first, second auxiliary igbt pipe q_s1、q_s2Current collection Extremely connected, Same Name of Ends and first, second assists mos pipe q_s3、q_s4Source electrode be connected, auxiliary energy storage electric capacity c_bOne end be connected in first Auxiliary igbt pipe q_s1With the first booster diode d_s1Junction point, the other end is connected in the second auxiliary igbt pipe q_s2With the second auxiliary Diode d_s2Junction point, first, second auxiliary igbt pipe q_s1、q_s2Each its parasitic capacitance self-contained, first, second auxiliary mos Pipe q_s3、q_s4Each its parasitic diode self-contained and parasitic capacitance；

Secondary current rectifying and wave filtering circuit 4 is by commutation diode d_r, rectification mos pipe q_rAnd output filter capacitor c₂With output filter Ripple inductance l₂Composition, isolating transformer t₁The different name end of first vice-side winding connects commutation diode d_rAnode, rectification two pole Pipe d_rWith rectification mos pipe q_r, output inductor l₂The positive output end of led load, isolating transformer t is connected after series connection₁First The negative output terminal that the Same Name of Ends of vice-side winding is loaded with led is connected, output filter capacitor c₂It is parallel to rectification mos pipe q_rSource electrode And the negative output terminal of led load between, rectification mos pipe q_rComprise its parasitic diode and parasitic capacitance.

The invention has the following beneficial effects:

(1) using fixing master switch mos pipe q₁Mode realize PFC；

(2) changer is operated in discontinuous mode, it is to avoid the Reverse recovery of secondary side diode；The isolation of anti exciting converter becomes Depressor increases a winding, and balanced input and output pulsation are come using to and fro flow of power full-bridge converter in assists winding side Difference, reduce auxiliary capacitor capacitance size by increasing the average voltage of auxiliary energy storage electric capacity and mains ripple, remove led and drive The twice industrial frequency AC component of the driving current in galvanic electricity source, reduces output filter capacitor capacitance size so as to thin film can be used Electric capacity replaces electrochemical capacitor, realizes small volume, long-life；

(3) auxiliary circuit increasing does not affect main circuit work, and auxiliary circuit only processes the pulsation of input and output instantaneous power Difference；

(4) output current of led driving power supply is constant current it is adaptable to need the led driving power supply applied field of constant current output Close.

Brief description:

Fig. 1 is the structural representation of single stage type no electrolytic capacitor led driving power supply of the present invention.

Fig. 2 is the main waveform diagram of single stage type no electrolytic capacitor led driving power supply.

Fig. 3-Fig. 7 is the equivalent circuit structure schematic diagram of each switch mode.

Primary symbols title in above-mentioned accompanying drawing: v_inLine voltage；l₁Input filter inductance；c₁Input filter electricity Hold；d₁、d₂、d₃、d₄Diode；q₁Master switch mos manages；q_s1First auxiliary igbt pipe；q_s2Second auxiliary igbt pipe； q_s3First auxiliary mos pipe；q_s4Second auxiliary mos pipe；d_s1First booster diode；d_s2Second booster diode； c_bAuxiliary energy storage electric capacity；t₁Isolating transformer；d_rCommutation diode；q_rRectification mos manages；c₂Output filter capacitor； l₂Output inductor；v_oOutput voltage；i_oOutput current；c_bAuxiliary energy storage electric capacity；p_inInput power；p_o— Output；p_ripThe difference that input power is pulsed with output instantaneous power；t_linePower frequency period；l_mFormer limit inductance； i_s2Electric current on second vice-side winding；i_s1Electric current on first vice-side winding；i_inElectrical network input current；i_p— Transformator t₁Primary current；v_cbAuxiliary energy storage electric capacity both end voltage；v_abVoltage between a point and b point.

Specific embodiment:

Refer to shown in Fig. 1, single stage type no electrolytic capacitor led driving power supply of the present invention is by input filter rectification circuit 1, anti- Sharp primary side switch circuit 2, assists winding full-bridge two-way circuit 3, secondary current rectifying and wave filtering circuit 4 form.Its main circuit is 1,2,4 The anti exciting converter being grouped into.

Isolating transformer t₁It is made up of a primary side winding and two vice-side winding, including former limit inductance (being produced by self-induction) And leakage inductance.The filter circuit of input filter rectification circuit 1 is by input filter inductance l₁With input filter capacitor c₁It is connected in parallel on electrical network defeated Enter two ends composition, rectifying part adopts four diode d₁、d₂、d₃、d₄The full-bridge uncontrollable rectifier circuit in parallel of composition is in filtered electrical Road two ends.Flyback primary side switch circuit 2 is by isolating transformer t₁The different name end of primary side winding and master switch mos pipe q₁Drain electrode phase Even form.Master switch mos pipe q₁Including its parasitic diode and parasitic capacitance.The composition of assists winding full-bridge two-way circuit 3 is, First is assisted igbt pipe q_s1With the first booster diode d_s1And first auxiliary mos pipe q_s3It is sequentially connected in series, the second auxiliary igbt Pipe q_s2With the second booster diode d_s2And second auxiliary mos pipe q_s4Two brachium pontis parallel connections are formed after being sequentially connected in series, and in parallel In isolating transformer t₁Second vice-side winding two ends.Isolating transformer t₁The different name end and first, second of second vice-side winding Auxiliary igbt pipe q_s1、q_s2Colelctor electrode be connected, Same Name of Ends with first, second assist mos pipe q_s3、q_s4Source electrode be connected.Auxiliary storage Can electric capacity c_bOne end be connected in the first auxiliary igbt pipe q_s1With the first booster diode d_s1Junction point, it is auxiliary that the other end is connected in second Help igbt pipe q_s2With the second booster diode d_s2Junction point.First, second auxiliary igbt pipe q_s1、q_s2Each its parasitism self-contained Electric capacity, first, second auxiliary mos pipe q_s3、q_s4Each its parasitic diode self-contained and parasitic capacitance.

Secondary current rectifying and wave filtering circuit 4 is by commutation diode d_r, rectification mos pipe q_rAnd output filter capacitor c₂With output filter Ripple inductance l₂Composition.Isolating transformer t₁The different name end of first vice-side winding connects commutation diode d_rAnode.Rectification two pole Pipe d_rWith rectification mos pipe q_r, output inductor l₂The positive output end of led load is connected after series connection.Isolating transformer t₁First The negative output terminal that the Same Name of Ends of vice-side winding is loaded with led is connected.Output filter capacitor c₂It is parallel to rectification mos pipe q_rSource electrode And the negative output terminal of led load between.Rectification mos pipe q_rComprise its parasitic diode and parasitic capacitance.

Electric main is through by input filter inductance l₁With input filter capacitor c₁The filter circuit of composition connects by diode d₁、d₂、d₃、d₄The rectifier bridge of composition, its positive pole and isolating transformer t₁The Same Name of Ends of primary side winding is connected.Isolating transformer t₁Former The different name end of side winding connects master switch mos pipe q₁Drain electrode, master switch mos pipe q₁Source electrode be connected with rectifier bridge negative pole.

Assists winding full-bridge two-way circuit 3 is by two auxiliary igbt pipe q_s1、q_s2And two auxiliary mos pipe q_s3、q_s4, two Booster diode d_s1、d_s2And auxiliary energy storage electric capacity c_bComposition.Wherein auxiliary energy storage electric capacity c_bEffect be used to balanced input work( The difference that rate is pulsed with output.

Isolating transformer t₁Secondary adopt commutation diode d_rWith rectification mos pipe q_rRectification, by output filter capacitor c₂ With output inductor l₂Filtering.

Structure and Fig. 2 single stage type no electrolytic capacitor led with reference to Fig. 1 single stage type no electrolytic capacitor led driving power supply The main waveform diagram explanation single stage type no electrolytic capacitor led driving power supply of driving power supply realizes the substantially square of no electrolytic capacitor Method.As seen from Figure 2, when power factor is 1, input voltage is identical with input current phase place, and therefore input power is

$p_{in}=v_{in}\left(t\right)i_{in}\left(t\right)=v_m\sin \mathrm{\ω}t\×i_m\sin \mathrm{\ω}t=\frac{v_m{i}_m(1-cos2\mathrm{\ω}t)}{2}---\left(1\right)$

V in formula_mFor the virtual value of electrical network input voltage, i_mVirtual value for input current.

Due to the constant voltage load characteristic of led, and need constant-current driving, therefore output is straight, is designated as p_o.False If the efficiency of changer is 100%, then Mean Input Power should be equal with output.It is hereby achieved that input power with The difference of output instantaneous power pulsation

p_rip=p_in(t)-p_o=-p_ocos2ωt (2)

Make the instantaneous power on auxiliary energy storage electric capacity equal with the difference of the instantaneous pulsation of input power output, you can flat The difference that weighing apparatus input power is pulsed with output.In [t_line/ 8,3tl_ine/ 8] in, auxiliary energy storage electric capacity c_bAbsorb energy be

$\mathrm{\δ}e={\&integral;}_{\frac{t_{line}}{8}}^{\frac{3t_{line}}{8}}\[p_{in}\left(t\right)-p_o\]dt=\frac{p_o}{\mathrm{\ω}}---\left(3\right)$

The energy that auxiliary energy storage electric capacity absorbed in this period simultaneously is also denoted as

$\mathrm{\δ}e-\frac{1}{2}{c}_b(v_{c\_\max }^2-v_{c\_\min }^2)---\left(4\right)$

Above two formulas are equal can to draw auxiliary energy storage capacitor's capacity size, be

$c_b=\frac{2p_o}{\mathrm{\ω}(v_{c\_\max }^2-v_{c\_\min }^2)}=\frac{p_o}{\mathrm{\ω}\·{\mathrm{\δv}}_c\·v_{c\_av}}---\left(5\right)$

Wherein ω is power frequency angular frequency, δ v_cFor assisting storage capacitor mains ripple value, v_{c_av}For assisting storage capacitor voltage Meansigma methodss.As can be seen from the above equation, by increasing δ v_cAnd v_{c_av}The capacitance that auxiliary energy storage electric capacity can be made significantly reduces.? In the present invention, δ v can be increased by adjusting second vice-side winding with the turn ratio of primary side winding_cAnd v_{c_av}, reduce further The size of auxiliary energy storage electric capacity, such that it is able to replace electrochemical capacitor with the less thin-film capacitor of capacitance.

To illustrate below in conjunction with the main waveform diagram of Fig. 2 and Fig. 3-7 each switch mode equivalent circuit structure schematic diagram The type of drive of single stage type no electrolytic capacitor led driving power supply and each mode concrete operating principle.As shown in Figure 2, this conversion Device mainly has two mode of operations, is designated as mode 1 when inputting instantaneous power and being more than output instantaneous power, when the instantaneous work(of output Rate is designated as mode 2 when being more than input instantaneous power.In mode 1, there are four kinds of switch mode in each switch periods, be respectively [t₀, t₁]、[t₁, t₂]、[t₂, t₃]、[t₃, t₄].Below the working condition of each switch mode is made a concrete analysis of.

Before analysis, make the following assumptions: 1. all switching tubes and diode are ideal component；2. all inductance, electricity Hold and isolating transformer is ideal element；3. outputting inductance is sufficiently large, and can be approximately considered output is a DC current source i_o, i_oFor output current；4. because power frequency period is far longer than switch periods, in switch periods, input voltage v_inApproximately see Make constant, be v_msinωt；Auxiliary energy storage inductance c_bBoth end voltage v_cbAlso approximately regard as constant.

1. switch mode 1 [t₀,t₁] (corresponding to Fig. 3)

In t₀In the moment, open master switch mos pipe q₁, isolating transformer t₁The different name end of first vice-side winding is negative voltage, Secondary commutation diode d_rReverse-biased cut-off, isolating transformer t₁Primary current i_pWith slope v_in/l_mLinear rise, electric main to Former limit inductive energy storage.l_mSize for former limit inductance.Powered to the load by output filter capacitor and output inductor.Through d_yt_sAfter time, that is, in t₁Moment turns off master switch mos pipe q₁.Wherein d_yIt is master switch mos pipe q₁Dutycycle, t_sIt is switch week Phase.Isolating transformer t₁The peak value of primary current is

$i_{p\_pk}=\frac{v_m\left|sin\mathrm{\ω}t\right|d_y}{l_m{f}_s}---\left(6\right)$

In switch periods, the meansigma methodss of primary current are

$i_{p\_av}=\frac{1}{2}{i}_{p\_pk}{d}_y=\frac{v_m\left|sin\mathrm{\ω}t\right|d_y^2}{2l_m{f}_s}---\left(7\right)$

In formula: f_sFor switching frequency；It can be seen that in half power frequency period, if dutycycle d_yKeep constant, then input Current average is proportional to input voltage, therefore fixes master switch mos pipe dutycycle, and working in discontinuous conduct mode can be automatically real Existing PFC.

2. switch mode 2 [t₁,t₂] (corresponding to Fig. 4)

In t₁Moment turns off master switch mos pipe q₁Afterwards, open the first auxiliary igbt pipe q_s1With the second auxiliary mos pipe q_s4, the Two auxiliary igbt pipe d_s2It is also switched on, secondary rectification mos pipe q_rCut-off, former limit inductance l_mEnergy is to auxiliary energy storage electric capacity c_bCharge, the The electric current i of two vice-side winding_s2Linear decline.Powered to the load by output filter capacitor and output inductor.When former limit electricity Sense l_mOn energy be reduced to when being exactly equal to energy needed for output in switch periods, i.e. t₂In the moment, turn off the first auxiliary Igbt pipe q_s1With the second auxiliary mos pipe q_s4.

3. switch mode 3 [t₂,t₃] [corresponding to Fig. 5]

In t₂Moment turns off the first auxiliary igbt pipe q_s1With the second auxiliary mos pipe q_s4After open secondary rectification mos pipe q_r, every From transformator t₁First vice-side winding different name end is positive voltage, commutation diode d_rConducting, former limit inductance l_mOn energy conversion For electric field energy to load and output capacitance c_oElectric discharge, isolating transformer t₁First vice-side winding on electric current i_s1Under linear Fall, until dropping to 0, i.e. t₃When, this mode terminates.

4. switch mode 4 [t₃,t₄] [corresponding to Fig. 6]

Isolating transformer t in this mode₁On winding, electric current is zero, for interrupted mode, all switching tubes and two poles Pipe is turned off.There is provided energy by output filter capacitor and output inductor for load.

In mode 2, equally there are four kinds of switch mode in each switch periods, be [t respectively₀, t₁]、[t₁, t₂]、[t₂, t₃]、[t₃, t₄].[t in wherein mode 2₀, t₁]、[t₁, t₂]、[t₃, t₄] [t in mode and mode 1₀, t₁]、[t₁, t₂]、[t₃, t₄] Modality work principle be similar to, will not be described here.

To make a concrete analysis of the switch mode 2 [t in lower mode 2 below₁,t₂] [corresponding to Fig. 7] when changer work former Reason.

In t₁Moment turns off master switch mos pipe q₁Afterwards, open the second auxiliary igbt pipe q_s2With the first auxiliary mos pipe q_s3, the One booster diode d_s1It is also switched on, secondary rectification mos pipe q_rCut-off, auxiliary energy storage electric capacity c_bFormer limit inductance to isolating transformer l_mCharge, the electric current i of second vice-side winding_s2Linear rise.Loaded to led from output filter capacitor and output inductor and supply Electricity.As former limit inductance l_mOn energy be raised to just equal in switch periods export needed for energy when, i.e. t₂In the moment, close Disconnected second auxiliary igbt pipe q_s2With the first auxiliary mos pipe q_s3.

It can be seen that isolating transformer t₁Electric current i on first vice-side winding_s1Do not contain twice power frequency component, contain only High fdrequency components can be filtered by less filter capacitor and filter inductance, be put down by switching frequency and higher harmonic components Straight output current.

Example of the present invention is as follows: input line voltage virtual value: v_m=220v；Electrical network work frequency: f_line =50hz；Output DC voltage: v_o=48v；Output current: i_o=0.7a；Isolating transformer t₁Former limit and first vice-side winding No-load voltage ratio: 4；Isolating transformer t₁Former limit and second vice-side winding no-load voltage ratio: 1；Former limit inductance: l_m=200uh；Master switch mos manages q₁, first auxiliary mos pipe q_s3, second auxiliary mos pipe q_s4: ixtp4n80p；First auxiliary igbt pipe q_s1, second auxiliary igbt pipe q_s2: sgp02n60；Secondary rectification mos pipe q_r: irf630；First booster diode d_s1, the second booster diode d_s2: us5j；Secondary Side commutation diode d_r: mbrs3200；Auxiliary energy storage electric capacity c_b: 4.7uf/400v；Input filter capacitor c₁: 0.47uf/400v； Input filter inductance l₁: 50uh；Output filter capacitor c₂: 10uf/100v；Output inductor l₂: 50uh；Switching frequency: f_s= 200khz.

The above is only the preferred embodiment of the present invention it is noted that ordinary skill people for the art For member, some improvement can also be made under the premise without departing from the principles of the invention, these improvement also should be regarded as the present invention's Protection domain.

Claims (1)

1. a kind of single stage type no electrolytic capacitor led driving power supply it is characterised in that: include input filter rectification circuit (1), flyback Primary side switch circuit (2), assists winding full-bridge two-way circuit (3), secondary current rectifying and wave filtering circuit (4) and isolating transformer (t₁)；

Isolating transformer (t₁) be made up of a primary side winding and two vice-side winding, including isolating transformer former limit inductance (l_m) And leakage inductance, flyback primary side switch circuit (2) is connected to isolating transformer (t₁) primary side winding on, secondary current rectifying and wave filtering circuit And assists winding full-bridge two-way circuit (3) is connected to isolating transformer (t (4)₁) two vice-side winding on；

The filter circuit of input filter rectification circuit (1) is by input filter inductance (l₁) and input filter capacitor (c₁) after series connection simultaneously It is associated in electrical network input two ends composition, the rectifying part of input filter rectification circuit (1) adopts four diode (d₁、d₂、d₃、d₄) The full-bridge uncontrollable rectifier circuit in parallel of composition is in both ends of filter capacitor；

Flyback primary side switch circuit (2) is by isolating transformer (t₁) different name end and the master switch mos of primary side winding manage (q₁) drain electrode It is connected to form, master switch mos manages (q₁) include its parasitic diode and parasitic capacitance；

Assists winding full-bridge two-way circuit (3) is by first, second auxiliary igbt pipe (q_s1、q_s2) and first, second auxiliary mos pipe (q_s3、q_s4), first, second booster diode (d_s1、d_s2) and auxiliary energy storage electric capacity (c_b) composition, the wherein first auxiliary igbt pipe (q_s1) and the first booster diode (d_s1) and the first auxiliary mos pipe (q_s3) be sequentially connected in series, the second auxiliary igbt pipe (q_s2) and the Two booster diode (d_s2) and the second auxiliary mos pipe (q_s4) be sequentially connected in series after form two brachium pontis parallel connections, and be connected in parallel on every From transformator (t₁) second vice-side winding two ends, isolating transformer (t₁) second vice-side winding different name end and first, second Auxiliary igbt pipe (q_s1)、(q_s2) colelctor electrode be connected, Same Name of Ends with first, second auxiliary mos manage (q_s3、q_s4) source electrode be connected, Auxiliary energy storage electric capacity (c_b) one end be connected in first auxiliary igbt pipe (q_s1) and the first booster diode (d_s1) junction point, another End is connected in the second auxiliary igbt pipe (q_s2) and the second booster diode (d_s2) junction point, first, second auxiliary igbt pipe (q_s1、 q_s2) each its parasitic capacitance self-contained, first, second auxiliary mos pipe (q_s3、q_s4) each its parasitic diode self-contained and parasitism electricity Hold；

Secondary current rectifying and wave filtering circuit (4) is by commutation diode (d_r), rectification mos manages (q_r) and output filter capacitor (c₂) and defeated Go out filter inductance (l₂) composition, isolating transformer (t₁) the different name end of first vice-side winding connects commutation diode (d_r) sun Pole, commutation diode (d_r) manage (q with rectification mos_r), output inductor (l₂) connect the positive output end of led load after series connection, Isolating transformer (t₁) negative output terminal that the Same Name of Ends of first vice-side winding is loaded with led is connected, output filter capacitor (c₂) and It is coupled to rectification mos pipe (q_r) source electrode and led load negative output terminal between, rectification mos manage (q_r) comprise its parasitic diode and Parasitic capacitance.