CN102611303A - Soft switching DC-DC (direct current-direct current) converter - Google Patents

Abstract

The invention discloses a soft switching DC-DC (direct current-direct current) converter. The soft switching DC-DC converter comprises a direct-current input end and a direct-current output end, wherein a series branch of a first switch tube (T1) and a second switch tube (T2) is connected between a positive terminal and a negative terminal of a direct-current input power supply (UI); the first switch tube (T1) is connected with a series resonance branch of a first inductor (L1) and a first capacitor (C1) in parallel; the second switch tube (T2) is connected with a second capacitor (C2) in parallel; a linear commutation series branch of a linear commutation inductor (Lx) and a linear commutation capacitor (Cx) is connected between a connecting point of the first switch tube (T1) and the second switch tube (T2) and the negative terminal of the direct-current input power supply (UI); a filter inductor (L) is connected between the connecting point of the first switch tube (T1) and the second switch tube (T2) and the positive output end of the direct-current output end; the direct-current output end is connected with an output capacitor (C) in parallel; and the negative terminal of the direct-current input power supply (UI) is connected with the negative terminal of the direct-current output end. The soft switching DC-DC converter is low in circuit loss and high in reliability and efficiency.

Description

A kind of soft switch DC-DC converter

Technical field

The present invention relates to a kind of DC-DC converter, relate in particular to a kind of soft switch DC-DC converter.

Background technology

Direct-current switch power supply is to have DC converter and output voltage is constant or the DC power supply that changes on request, and it is input as direct current or alternating current.The core of direct-current switch power supply is the DC-DC converter, and it is the converter that a kind of direct current is converted to another kind of or multiple direct current energy, is the critical piece of direct-current switch power supply.

Along with the continuous development of power electronic technology, direct-current switch power supply is widely used in commercial plant power supply, communication power supply, large computer supply, Aero-Space power supply and the facilities for transport and communication power supply.

High frequencyization, miniaturization, modularization and intellectuality are the developing direction of direct-current switch power supply.In order to dwindle the volume of direct-current switch power supply, improve power density, at first do from the operating frequency that increases substantially Switching Power Supply.But high frequencyization but makes power device switching loss and drive loss increase considerably, and has reduced circuit efficiency.

The topological structure of DC/DC converter of the prior art is as shown in Figure 1, comprises switch transistor T, diode D, inductance L and capacitor C.The DC input voitage of DC/DC converter is u _d, the pressure drop on switch transistor T and the inductance L is respectively u _TAnd u _L, I _TBe the electric current that flows through switch transistor T, i _L, i _D, i _CIt is respectively the electric current that flows through inductance L, diode D and capacitor C.VD on the load resistance R is u _OSwitch transistor T is opened and is turn-offed with certain duty ratio under the control of drive signal, thereby realizes from DC input voitage u _dTo VD u _OThe DC/DC conversion.

There is following shortcoming at least in above-mentioned prior art: what switch transistor T adopted is hard switching, so its switching loss is big; Diode D has very big reverse recovery current, and loss is big, reliability is low, efficient is low.

Soft switch technique has appearred in the development along with the direct-current switch power supply technology.Soft switch greatly reduces the switching loss of power device owing to adopt ZVT (ZVS) and Zero Current Switch (ZCS), has reduced switch stress; Simultaneously because the development of device; Switching frequency greatly improves, and greatly reduces the volume of magnetic device, has improved the power density of product.Therefore soft switch circuit topology is the optimal circuit structure that Switching Power Supply is suitable for.

Summary of the invention

The purpose of this invention is to provide the soft switch DC-DC converter that a kind of loss is low, reliability is high, efficient is high.

The objective of the invention is to realize through following technical scheme:

Soft switch DC-DC converter of the present invention; Comprise direct-flow input end, dc output end; It is characterized in that; Be connected with the series arm of first switching tube (T1) and second switch pipe (T2) between said direct-current input power supplying (UI) anode and the negative terminal; First switching tube (T1) is parallel with the series resonance branch road of first inductance (L1) and first electric capacity (C1), and second switch pipe (T2) is parallel with second electric capacity (C2), is connected with the linear change of current series arm of linear change of current inductance (Lx) and linear change of current electric capacity (Cx) between the tie point of first switching tube (T1) and second switch pipe (T2) and the negative terminal of direct-current input power supplying (UI); Be connected with filter inductance (L) between the tie point of first switching tube (T1) and second switch pipe (T2) and the positive output end of dc output end; Dc output end is parallel with output capacitance (C), and the negative terminal of direct-current input power supplying (UI) negative terminal and dc output end links together, and said first switching tube (T1) and second switch pipe (T2) are soft switch.

Preferably, wherein said first switching tube (T1) and second switch pipe (T2) insert first, second drive signal (u respectively _Gs1, u _Gs2), and first, second drive signal (u wherein _Gs1, u _Gs2) between have dead time.

Preferably, the inductance value of wherein said filter inductance (L) is the inductance value of linear change of current inductance (Lx) or more than 30 times of inductance value of first inductance (L1).

Preferably, the inductance value L of wherein said ripple inductance (L) does

$L=\frac{\mathrm{Uo}(1-D)\mathrm{Ts}}{{\mathrm{\Δi}}_L}$

In the formula, Uo is the output voltage values of dc output end; D is the duty ratio of first switching tube (T1); Ts is the switch periods of first switching tube (T1); Δ i _LBe the linear rising increment of the electric current of filter inductance (L).

Preferably, the inductance value Lx of wherein said linear change of current branch road inductance (Lx) satisfies:

$\mathrm{Lx}\≥\frac{\mathrm{Uo}(1-D)\mathrm{TsTd}}{\mathrm{IoTd}+\mathrm{UI}({C1}^{\′}+{C2}^{\′})}$

In the formula, UI is the input voltage value of direct-current input power supplying (UI); Uo is the output voltage values of dc output end; Io is the output current value of dc output end; D is the duty ratio of first switching tube (T1); Ts is the switch periods of first switching tube (T1); Td is first, second drive signal (u of first switching tube (T1) and second switch pipe (T2) _Gs1, u _Gs2) dead time; C1 ' is the junction capacitance of first switching tube (T1); C2 ' is the junction capacitance of second switch pipe (T2).

Further preferably, the capacitance Cx of wherein said linear change of current branch road electric capacity (Cx) is:

$\mathrm{Cx}=\frac{\mathrm{Lx}{\left(i_{\mathrm{Lx}\max }\right)}^2}{U_{\mathrm{Cx}}{\mathrm{\ΔU}}_{\mathrm{Cx}}+{{\mathrm{\ΔU}}_{\mathrm{Cx}}}^2}$

In the formula, U _CxBe linear change of current electric capacity (Cx) voltage, and U _Cx=DUI=Uo; Δ U _CxBe the ripple voltage on the linear change of current electric capacity (Cx); i _{Lx max}Maximum current for the linear change of current inductance (Lx) of flowing through.

Preferably, wherein, the capacitance C2 of said second electric capacity (C2) satisfies:

$\left.\begin{array}{c}C2\≤\frac{I_{S1}\mathrm{Td}}{\mathrm{UI}}\\ C2\≤\frac{\left|I_{S2}\right|\mathrm{Td}}{\mathrm{UI}}\end{array}\right\}$

In the formula, UI is the input voltage of direct-current input power supplying (UI); Td is first, second drive signal (u of first switching tube (T1) and second switch pipe (T2) _Gs1, u _Gs2) dead time; I _S1For flow to the electric current (i of output from first switching tube (T1) and the tie point (S) of second switch pipe (T2) _S) maximum; I _S2For flow to the electric current (i of output from first switching tube (T1) and the tie point (S) of second switch pipe (T2) _S) minimum value.Further preferably, wherein, the capacitance C1 of said first electric capacity (C1) equates with the capacitance C2 of second electric capacity (C2), that is: C1=C2.

Preferably, the inductance value L1 of wherein said first inductance (L1) satisfies:

$\frac{1}{2\mathrm{\π}\sqrt{L1C1}}=f1\≥3f$

In the formula, C1 is the capacitance of first electric capacity (C1), and f1 is the resonance frequency of first inductance (L1) and first electric capacity (C1), and f is the contactor frequency.

Than other existing soft switch DC-DC converter, all power switch pipes of the present invention are soft switch, have reduced switching loss greatly; Fly-wheel diode has been removed in circuit and the contrast of common BUCK circuit, thereby there is not reverse recovery current in circuit.In a word, circuit has reduced loss, has strengthened reliability, has improved efficient.

Description of drawings

Fig. 1 is the topological structure of DC-DC converter in the prior art;

Fig. 2 is the topological structure of the soft switch DC-DC converter of the present invention;

Fig. 3 a is first drive signal waveform of first switching tube in the soft switch DC-DC converter of the present invention;

Fig. 3 b is second drive signal waveform of second switch pipe in the soft switch DC-DC converter of the present invention;

Fig. 4 divides the time zone main electric weight oscillogram for each working stage of the soft switch DC-DC converter of the present invention;

Fig. 5 a is on off state and the equivalent electric circuit of the time zone A of the soft switch DC-DC converter of the present invention;

Fig. 5 b is the time zone B of the soft switch DC-DC converter of the present invention, on off state and the equivalent electric circuit of C;

Fig. 5 c is on off state and the equivalent electric circuit of the time zone D of the soft switch DC-DC converter of the present invention;

Fig. 5 d is on off state and the equivalent electric circuit of the time zone E of the soft switch DC-DC converter of the present invention;

Fig. 5 e is the time zone F of the soft switch DC-DC converter of the present invention, on off state and the equivalent electric circuit of G;

Fig. 5 f is on off state and the equivalent electric circuit of the time zone H of the soft switch DC-DC converter of the present invention;

Fig. 5 g for the L1-C1 series resonance branch road of the soft switch DC-DC converter of the present invention in the time zone G, H equivalent electric circuit;

Fig. 6 is the Lx that the soft switch DC-DC converter of the present invention is used for confirming linear change of current series arm, the equivalent electric circuit of Cx parameter;

Embodiment

Soft switch DC-DC converter of the present invention, its best embodiment is as shown in Figure 2.Fig. 2 is the topological diagram of the embodiment of the soft switch DC-DC converter of the present invention; Comprise direct-flow input end, dc output end; Wherein direct-flow input end inserts direct-current input power supplying UI, and dc output end connects load R, and the VD value at load R two ends is Uo.Be connected with the series arm of first switch transistor T 1 and second switch pipe T2 between said direct-current input power supplying UI anode and the negative terminal; First switch transistor T 1 is parallel with the series resonance branch road of first inductance L 1 and first capacitor C 1; Second switch pipe T2 is parallel with second capacitor C 2; Be connected with the linear change of current series arm of linear change of current inductance L x and linear change of current capacitor C x between the tie point of first switch transistor T 1 and second switch pipe T2 and the negative terminal of direct-current input power supplying UI; First switch transistor T 1 is S with the tie point of second switch pipe T2, is connected with filter inductance L between the positive output end of S point and dc output end, and dc output end is parallel with output capacitance C; The negative terminal of direct-current input power supplying UI negative terminal and dc output end links together, and said first switch transistor T 1 is soft switch with second switch pipe T2.

Wherein, the electric current that flows through filter inductance L is a direct current, the current i of the linear change of current series arm Lx-Cx that flows through _LxBe the triangular wave alternating current, from the current i of S point outflow _SBe direct current and triangular wave alternating current sum.T1, T2 are first, second switching tube among Fig. 2, and VD1, VD2 are respectively the body diode of T1, T2.Linear change of current capacitor C x is used for smothing filtering, and capacity is enough big, and its two ends direct voltage is the same with the output voltage of DC-DC converter, by output duty cycle D decision, i.e. U _Cx=DUI=Uo, wherein D is the duty ratio of T1, and UI is the magnitude of voltage of direct-current input power supplying UI, and Uo is an output voltage values.L1-C1 is the series resonance branch road.The inductance value of filter inductance L is much larger than the inductance value of inductance L x or L1, and the inductance value of L is more than 30 times of inductance value of inductance L x or L1 usually.T1 has realized the ZVS shutoff, and ZCS opens; The T2 most of the time is operated in the reverse-conducting state through body diode VD2, has realized the ZVS unlatching, and ZCS turn-offs; Lx and Cx series arm excess energy can feed back to input; The energy of L1 and C1 series arm can feed back to input and load.In a word, all power switchs in the topology of the present invention are soft switch entirely, so it has only the switching loss of underfooting.

Fig. 3 a, Fig. 3 b are respectively the first drive signal u of first switch transistor T 1 _Gs1And the second drive signal u of second switch pipe T2 _Gs2Waveform, from figure drive signal waveform can know the first drive signal u _Gs1The second drive signal u during for high level _Gs2Be low level, the first drive signal u _Gs1The second drive signal u during for low level _Gs2Be high level, and in order to prevent the common-mode conducting, to first, second drive signal of T1 and T2 provide dead time Td, i.e. the first drive signal u _Gs1The rising edge and the second drive signal u _Gs2Trailing edge between free interval T d, the same first drive signal u _Gs1The trailing edge and the second drive signal u _Gs2Rising edge between also free interval T d, in dead time two switches are broken off simultaneously.

Do detailed description in the face of operation principle of the present invention down:

For the ease of analyzing, in a work period, the present invention can be divided into 8 kinds of on off states, and the on off state in its each time zone and equivalent circuit diagram are shown in Fig. 5 a-Fig. 5 f, and corresponding main electric weight waveform is as shown in Figure 4.

Among Fig. 4, u _Gs1, u _Gs2Represent first, second drive signal respectively, u _Ds1, u _Ds2Represent voltage between the D, the S utmost point of T1, T2 respectively, i _Lx, i _s, i _T1, i _T2, i _C2, i _C1Lx, S point, T1, T2, C2, the electric current of C1, U are flow through in expression respectively _C1The voltage of expression C1.

1.C2 constant-current discharge (time zone A): switch transistor T 1 conducting before t=t0, T2 ends, and series resonance takes place in L1-C1.During to t=t0, the electric current that flows through T1 has reached maximum I _S1, the analysis of time zone H is seen in concrete analysis.

During t=t0, the voltage U s at C2 two ends, i.e. u _s=UI.During greater than t0, the drive signal of T1 disappears, u at t _Gs1=0, circuit gets into Td dead time, contactor state and equivalent electric circuit such as Fig. 5 a.C2 begins discharge, and the L1-C1 branch road begins to regulate energy, u _sBegin to descend, to t=t ₁The time, u _s=0, T1 ends.

The time zone A time is very short, in this time period, can think the current i that S orders of flowing through _s=I _S1=const, i.e. i _SBe a constant, wherein I _S1For flow to the current i of output from tie point S _SMaximum.The voltage of S end is:

2.T1 end T2 reverse-conducting (time zone B, C): at t=t ₁The time, u _s=0.T is greater than t ₁The time, T1 ends, the T2 reverse-conducting, and output is through the body diode VD2 afterflow of T2, contactor state and equivalent electric circuit such as Fig. 5 b.Can find out that by equivalent electric circuit the L1-C1 branch road has sealed in a direct voltage source generation resonance, the energy of L1-C1 branch road increases.Can obtain following relational expression:

u _C1(t)＝U _I-U _Icosω ₁(t-t ₁) (2)

u _L1(t)＝U _Icosω ₁(t-t ₁) (3)

$i_{C1}\left(t\right)=i_{L1}\left(t\right)=C1\frac{{\mathrm{du}}_{C1}\left(t\right)}{t}=\frac{U_I}{\mathrm{Za}}{\sin \mathrm{\ω}}_1(t-t_1)---\left(4\right)$

In the formula, u _C1, u _L1The voltage of expression C1, L1, i _C1, i _L1Expression C1, the electric current of L1, U _IBe DC input voitage, C1 representes the capacitance of first electric capacity,

The B in the time zone, although circuit also is in Td dead time, the current i of the T2 that flows through _T2Through body diode VD2 circulation, do not receive drive signal u _Gs2Influence.The C in the time zone, u _Gs2=1, T2 still is operated in the reverse-conducting state through body diode.

3.T2 forward conduction (time zone D): when t=t3, the current i of the VD2 that flows through _VD2=0, the current i of the T2 that promptly flows through _T2The beginning zero passage.T is greater than t ₃After, S end negative current occurs, i.e. is＜0.This moment, the drive signal of T2 also existed, i.e. u _Gs2=1.T2 begins forward conduction, is i _SPath is provided.L1-C1 this moment resonance still, and begin to regulate energy.Contactor state and equivalent electric circuit such as Fig. 5 c.Circuit still satisfies relational expression (2), (3), (4).

4.C2 constant current charge (time zone E): t is greater than t ₄The time, the T2 drive signal disappears, and circuit begins to get into Td dead time, i _SBegin charging, u to C2 _sBegin to rise.To the output conveying capacity, the L1-C1 branch energy begins to reduce UI through the L1-C1 branch road.Contactor state and equivalent electric circuit such as Fig. 5 d.The time zone E time is very short, can think i _s=I _S2=const, i.e. i _SBe a constant, wherein I _S2For flow to the current i of output from tie point S _SMinimum value.To t=t ₅, the C2 end of charging, u _s=UI, T2 ends.

5.T1 reverse-conducting (time zone F, G): t is greater than t ₅The time, negative current i _SFeed back to input UI through VD1, series resonance takes place in L1-C1, contactor state such as Fig. 5 e.The G in the time zone, u _Gs1=0; The F in the time zone, ugs1=1.T1 is operated in the reverse-conducting state through body diode, until t ₇Moment negative current i _SDisappear.

6.T1 forward conduction (time zone H): t is greater than t ₇The time, i _S＞0, u _Gs1=1, T1 is operated in the forward conduction state.Contactor state and equivalent electric circuit are shown in Fig. 5 f.To moment t ₈, circuit is got back to time zone A operating state again.

G, H in the time zone, i.e. t6＜t＜t8, the voltage that is added on the L1-C1 branch road is 0, in whole switch periods, the L1-C1 auxiliary branch seals, and does not have energy exchange with the external world, the equivalent electric circuit of L1-C1 branch road such as Fig. 5 g.Obtain following relational expression:

u _L1(t-t ₆)+u _C1(t-t ₆)＝0 (6)

u _C1(t)＝U _Ocosω ₁(t-t ₆) (7)

$i_{C1}\left(t\right)=-\frac{U_O}{\mathrm{Za}}{\sin \mathrm{\ω}}_1(t-t_6)---\left(8\right)$

In the formula,

u _C1maxMaximum voltage on the expression C1.

Face method for designing of the present invention and step down and do detailed description:

Each parameter The design process of the soft switch DC-DC converter circuit of the present invention is following.

(1) selection of filter inductance L:

Said filter inductance L value is confirmed through following formula:

$L=\frac{\mathrm{Uo}(1-D)\mathrm{Ts}}{{\mathrm{\Δi}}_L}$

In the formula, Uo is the output voltage values of dc output end; D is the duty ratio of first switching tube (T1); Ts is the switch periods of first switching tube (T1); Δ i _LBe the linear rising increment of the electric current of filter inductance (L).

(2) selection of linear change of current inductance L x, Cx:

In Fig. 6, Lx-Cx is parallelly connected with T2, and VD1, VD2 are respectively the body diode of switch transistor T 1, T2, and C1 ', C2 ' are respectively T1, T2 parasitic capacitance (junction capacitance).Lx can be confirmed by following formula:

$\mathrm{Lx}\≥\frac{\mathrm{Uo}(1-D)\mathrm{TsTd}}{\mathrm{IoTd}+\mathrm{UI}({C1}^{\′}+{C2}^{\′})}$

In the formula, UI is the input voltage value of direct-current input power supplying (UI); Uo is the output voltage values of dc output end; Io is the output current value of dc output end; D is the duty ratio of first switching tube (T1); Ts is the switch periods of first switching tube (T1); Td is first, second drive signal (u of first switching tube (T1) and second switch pipe (T2) _Gs1, u _Gs2) dead time; C1 ' is the junction capacitance of first switching tube (T1); C2 ' is the junction capacitance of second switch pipe (T2).

Cx can be confirmed by following formula:

$\mathrm{Cx}=\frac{\mathrm{Lx}{\left(i_{\mathrm{Lx}\max }\right)}^2}{U_{\mathrm{Cx}}{\mathrm{\ΔU}}_{\mathrm{Cx}}+{{\mathrm{\ΔU}}_{\mathrm{Cx}}}^2}$

In the formula, U _CxBe linear change of current electric capacity (Cx) voltage, and U _Cx=DUI=Uo; Δ U _CxBe the ripple voltage on the linear change of current electric capacity (Cx); i _LxmaxMaximum current for the linear change of current inductance (Lx) of flowing through.

(3) selection of capacitor C 2:

Can find out that by Figure 11 time zone A [t0, t1], time zone E [t4, t5] must promptly must be suppressed at the time of discharging and recharging of C2 in Td dead time in dead time Td.Obtain by formula (1), (5):

$\left.\begin{array}{c}C2\≤\frac{I_{S1}\mathrm{Td}}{\mathrm{UI}}\\ C2\≤\frac{\left|I_{S2}\right|\mathrm{Td}}{\mathrm{UI}}\end{array}\right\}---\left(23\right)$

In the formula, UI is the input voltage of direct-current input power supplying (UI); Td is first, second drive signal (u of first switching tube (T1) and second switch pipe (T2) _Gs1, u _Gs2) dead time; I _S1For flow to the electric current (i of output from first switching tube (T1) and the tie point (S) of second switch pipe (T2) _S) maximum; I _S2For flow to the electric current (i of output from first switching tube (T1) and the tie point (S) of second switch pipe (T2) _S) minimum value.

(4) selection of capacitor C 1:

Generally get C1=C2.

(5) selection of resonant inductance L1:

In resonance condition, the resonance frequency f1 that gets L1, C1 on the engineering usually is more than three times of contactor frequency f to auxiliary branch L1-Cl at the whole switch periods groundwork of circuit, i.e. f1 >=3f, and the value of resonant inductance L1 can have following formula to confirm:

$\frac{1}{2\mathrm{\π}\sqrt{L1C1}}\≥3f$

In the formula, C1 is the capacitance of first electric capacity (C1), and f1 is the resonance frequency of first inductance (L1) and first electric capacity (C1), and f is the contactor frequency.

In order to test the performance of DC-DC converter of the present invention, in the invention described above specific embodiment, it is following to design following technical indicator: input voltage UI=300VDC; Output voltage U o=105VDC; Power output is 1500W, output resistance R=10 Ω, the operating frequency f=50kHz of circuit; Get C=2.2 μ F, get Td=1 μ s.

According to top discussion and rule, the parameter that we calculate the specific embodiment of the invention is following: D=0.35, L=1mH, Lx=33.6 μ H, Cx=42 μ F, L1=27 μ H, C1=C2=26.7nF, UI=300Vdc.

Emulation and experimental result:

With Pspice10.0 novel circuit has been carried out emulation, parameter is following: L=1mH, R=10 Ω, Lx=33.6 μ H, Cx=42 μ F, L1=27 μ H, C1=C2=26.7nF, C=2.2 μ F, UI=300Vdc, D=0.35, f=50kHz, Td=1 μ s.(D is the duty ratio of T1, and Td is the dead time of T1, T2 drive signal).From simulation result, can draw to draw a conclusion: (1) switch transistor T 1 is that no-voltage is turn-offed, and zero current is opened; (2) 2 mosts of the time of switch transistor T are operated in the reverse-conducting state through body diode, have realized that press off zero point to open zero-current switching; (3) Lx and Cx series arm excess energy can feed back to input, and the energy of L1 and C1 series arm can feed back to input and load.

Make an experimental prototype that power output is 1500W, selected for use switch transistor T 1 and switch transistor T 2 to be the power MOSFET of same model.Coming to the same thing of the result of experiment measuring and emulation.And measured the efficient of novel circuit with power analyzer, and experimental result shows: circuit of the present invention has very high efficient (about 95%), and it is 92% that prior art is used the efficient of hard switching circuit, and the efficient of soft switch circuit of the present invention brings up to about 95%.

All power switchs are soft switch among the present invention, have reduced switching loss greatly; Fly-wheel diode has been removed in circuit and the contrast of common BUCK circuit, thereby there is not reverse recovery current in circuit.In a word, circuit has reduced loss, has strengthened reliability, has improved efficient.

The above; Be merely the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, any technical staff who is familiar with the present technique field is in the technical scope that the present invention discloses; The variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.

Claims (9)

1. soft switch DC-DC converter; Comprise direct-flow input end, dc output end; It is characterized in that; Be connected with the series arm of first switching tube (T1) and second switch pipe (T2) between said direct-current input power supplying (UI) anode and the negative terminal; First switching tube (T1) is parallel with the series resonance branch road of first inductance (L1) and first electric capacity (C1), and second switch pipe (T2) is parallel with second electric capacity (C2), is connected with the linear change of current series arm of linear change of current inductance (Lx) and linear change of current electric capacity (Cx) between the tie point of first switching tube (T1) and second switch pipe (T2) and the negative terminal of direct-current input power supplying (UI); Be connected with filter inductance (L) between the tie point of first switching tube (T1) and second switch pipe (T2) and the positive output end of dc output end; Dc output end is parallel with output capacitance (C), and the negative terminal of direct-current input power supplying (UI) negative terminal and dc output end links together, and said first switching tube (T1) and second switch pipe (T2) are soft switch.

2. soft switch DC-DC converter according to claim 1 is characterized in that, said first switching tube (T1) and second switch pipe (T2) insert first, second drive signal (u respectively _Gs1, u _Gs2), and first, second drive signal (u wherein _Gs1, u _Gs2) between have dead time.

3. soft switch DC-DC converter according to claim 1 and 2 is characterized in that, the inductance value of said filter inductance (L) is the inductance value of linear change of current inductance (Lx) or more than 30 times of inductance value of first inductance (L1).

4. soft switch DC-DC converter according to claim 1 and 2 is characterized in that, the inductance value L of said filter inductance (L) does

$L=\frac{\mathrm{Uo}(1-D)\mathrm{Ts}}{\mathrm{\Δ}{i}_L}$

In the formula, Uo is the output voltage values of dc output end; D is the duty ratio of first switching tube (T1); Ts is the switch periods of first switching tube (T1); Δ i _LBe the linear rising increment of the electric current of filter inductance (L).

5. soft switch DC-DC converter according to claim 1 and 2 is characterized in that, the inductance value Lx of said linear change of current branch road inductance (Lx) satisfies:

$\mathrm{Lx}\≥\frac{\mathrm{Uo}(1-D)\mathrm{TsTd}}{\mathrm{IoId}+\mathrm{UI}({C1}^{\′}+{C2}^{\′})}$

In the formula, UI is the input voltage value of direct-current input power supplying (UI); Uo is the output voltage values of dc output end; Io is the output current value of dc output end; D is the duty ratio of first switching tube (T1); Ts is the switch periods of first switching tube (T1); Td is first, second drive signal (u of first switching tube (T1) and second switch pipe (T2) _Gs1, u _Gs2) dead time; C1 ' is the junction capacitance of first switching tube (T1); C2 ' is the junction capacitance of second switch pipe (T2).

6. soft switch DC-DC converter according to claim 5 is characterized in that, the capacitance Cx of said linear change of current branch road electric capacity (Cx) is:

$\mathrm{Cx}=\frac{\mathrm{Lx}{\left(i_{\mathrm{Lx}\max }\right)}^2}{U_{\mathrm{Cx}}{\mathrm{\ΔU}}_{\mathrm{Cx}}+{{\mathrm{\ΔU}}_{\mathrm{Cx}}}^2}$

In the formula, U _CxBe linear change of current electric capacity (Cx) voltage, and U _Cx=DUI=Uo; Δ U _CxBe the ripple voltage on the linear change of current electric capacity (Cx); i _LxmaxMaximum current for the linear change of current inductance (Lx) of flowing through.

7. soft switch DC-DC converter according to claim 1 and 2 is characterized in that, the capacitance C2 of said second electric capacity (C2) satisfies:

$\left.\begin{array}{c}C2\≤\frac{I_{S1}\mathrm{Td}}{\mathrm{UI}}\\ C2\≤\frac{\left|I_{S2}\right|\mathrm{Td}}{\mathrm{UI}}\end{array}\right\}$

In the formula, UI is the input voltage of direct-current input power supplying (UI); Td is first, second drive signal (u of first switching tube (T1) and second switch pipe (T2) _Gs1, u _Gs2) dead time; I _S1For flow to the electric current (i of output from first switching tube (T1) and the tie point (S) of second switch pipe (T2) _S) maximum; I _S2For flow to the electric current (i of output from first switching tube (T1) and the tie point (S) of second switch pipe (T2) _S) minimum value.

8. soft switch DC-DC converter according to claim 7 is characterized in that, the capacitance C1 of said first electric capacity (C1) equates with the capacitance C2 of second electric capacity (C2).

9. soft switch DC-DC converter according to claim 1 and 2 is characterized in that, the inductance value L1 of said first inductance (L1) satisfies:

$\frac{1}{2\mathrm{\π}\sqrt{L1C1}}=f1\≥3f$

In the formula, C1 is the capacitance of first electric capacity (C1), and f1 is the resonance frequency of first inductance (L1) and first electric capacity (C1), and f is the contactor frequency.

Images