CN201918897U - Soft switching DC-DC converter - Google Patents

Abstract

The utility model discloses a soft switching DC-DC converter, which comprises a direct-current input end and a direct-current output end. The soft switching DC-DC converter is characterized in that a serial connection branch circuit is connected between a positive end and a negative end of a direct-current input power source (U1), the serial connection branch circuit consists of a first switching tube (T1) and a second switching tube (T2), the first switching tube (T1) is connected with a serial connection resonance branch circuit in parallel, the serial connection resonance branch circuit consists of a first inductor (L1) and a first capacitor (C1), the second switching tube (T2) is connected with a second capacitor (C2), a linear commutation serial connection branch circuit is connected between a connecting point of the first switching tube (T1) with the second switching tube (T2) and the negative end of the direct-current input power source (U1), the linear commutation serial connection branch consists of a linear commutation inductor (Lx) and a linear commutation capacitor (Cx), a filter inductor (L) is connected between the connecting point of the first switching tube (T1) and the second switching tube (T2) and a positive output end of the direct-current output end, an output capacitor (C) is connected with the direct-current output end in parallel, the negative end of the direct-current input power source (U1) is connected together with a negative end of the direct-current output end, the first switching tube realizes ZVS (zero voltage switching) turn-off and ZCS (zero current switching) starting, the second switching tube operates in a reverse conduction state by the aid of a body diode most of the time and realizes ZVS starting and ZCS turn-off, residue energy of the serial connection branch circuit consisting of the linear commutation inductor (Lx) and the linear commutation capacitor (Cx) can be fed back to the input end.

Description

A kind of soft switch DC-DC converter

Technical field

The utility model relates to a kind of DC-DC converter, relates 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 comprises switch transistor T, diode D, inductance L and capacitor C as shown in Figure 1.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 zero voltage switch (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.

The utility model content

The purpose of this utility model provides the soft switch DC-DC converter that a kind of loss is low, reliability is high, efficient is high.

The purpose of this utility model is achieved through the following technical solutions:

Soft switch DC-DC converter of the present utility model, 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 described 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), second switch pipe (T2) is parallel with second electric capacity (C2), be 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 negative terminal of the tie point of first switching tube (T1) and second switch pipe (T2) and 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), the negative terminal of direct-current input power supplying (UI) negative terminal and dc output end links together, and described 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) is

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

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:

$\mathrm{Lx}\&GreaterEqual;\frac{\mathrm{Uo}(1-D)\mathrm{TsTd}}{\mathrm{IoTd}+\mathrm{UI}({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000422567800031.png"\; state="\{\{state\}\}">C</figure-callout>}1}^{\&prime;}+{C2}^{\&prime;})}$

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:

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

In the formula, U _CxBe linear change of current electric capacity (Cx) both end 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.

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

$\left.\begin{array}{c}C2\&le;\frac{{\mathrm{<figure-callout\; id="1"\; label="I\; S"\; filenames="HSA00000422567800031.png"\; state="\{\{state\}\}">I</figure-callout>}}_S\mathrm{Td}}{\mathrm{UI}}\\ C2\&le;\frac{\left|I_{S2}\right|\mathrm{Td}}{\mathrm{UI}}\end{array}\right\}$

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 described 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:

$\frac{1}{2\mathrm{\&pi;}\sqrt{L1\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000422567800031.png"\; state="\{\{state\}\}">C</figure-callout>}1}}=\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="HSA00000422567800031.png"\; state="\{\{state\}\}">f</figure-callout>}1\&GreaterEqual;3f$

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 utility model 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 utility model;

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

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

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

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 utility model;

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

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 utility model;

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 utility model;

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

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 utility model;

Fig. 5 g is that the L1-C1 series resonance branch road of the soft switch DC-DC converter of the utility model is at time zone G, H equivalent electric circuit;

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

Embodiment

Soft switch DC-DC converter of the present utility model, its best embodiment as shown in Figure 2.Fig. 2 is the topological diagram of the embodiment of the soft switch DC-DC converter of the utility model, 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 described 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, be connected with filter inductance L between the positive output end of S point and dc output end, 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 described first switch transistor T 1 and second switch pipe T2 are soft switch.

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 by 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 utility model 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, the drive signal waveform from figure as can be known, 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 disconnected simultaneously.

Below operation principle of the present utility model is done detailed description:

For the ease of analyzing, in a work period, the utility model 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 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 enters 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, can think the current i that S orders of flowing through in this time period _s=I _S1=const, promptly iS is 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 by the body diode VD2 afterflow of T2, contactor state and equivalent electric circuit such as Fig. 5 b.By equivalent electric circuit as can be seen the L1-C1 branch road 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)

$i_{C1}\left(t\right)=i_{L1}\left(t\right)=\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000422567800031.png"\; state="\{\{state\}\}">C</figure-callout>}1\frac{{\mathrm{du}}_{C1}\left(t\right)}{\mathrm{dt}}=\frac{U_I}{\mathrm{Za}}\sin {\mathrm{\&omega;}}_1(t-t_1)---\left(4\right)$

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 represents the capacitance of first electric capacity,

At time zone B, although circuit also is in Td dead time, the current i of the T2 that flows through _T2By body diode VD2 circulation, be not subjected to drive signal u _Gs2Influence.At time zone C, u _Gs2=1, T2 still is operated in the reverse-conducting state by 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, for iS provides path.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 enter 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 by 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 by VD1, series resonance takes place in L1-C1, contactor state such as Fig. 5 e.At time zone G, u _Gs1=0; At time zone F, ugs1=1.T1 is operated in the reverse-conducting state by 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.

At time zone G, H, 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 _O?cosω ₁(t-t ₆) (7)

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

In the formula, u _C1maxMaximum voltage on the expression C1.

Below method for designing of the present utility model and step are done detailed description:

Each parameter The design process of the soft switch DC-DC converter circuit of the utility model is as follows.

(1) selection of filter inductance L:

Described filter inductance L value is determined by following formula:

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

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).

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

In Fig. 6, Lx-Cx is in parallel 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 determined by following formula:

$\mathrm{Lx}\&GreaterEqual;\frac{\mathrm{Uo}(1-d)\mathrm{TsTd}}{\mathrm{IoTd}+\mathrm{UI}({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000422567800031.png"\; state="\{\{state\}\}">C</figure-callout>}1}^{\&prime;}+{C2}^{\&prime;})}$

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 determined by following formula:

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

In the formula, U _CxBe linear change of current electric capacity (Cx) both end 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:

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

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

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-C1 at the whole switch periods groundwork of circuit, i.e. f1 〉=3f, and the value of resonant inductance L1 can have following formula to determine:

$\frac{1}{2\mathrm{\&pi;}\sqrt{L1\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HSA00000422567800031.png"\; state="\{\{state\}\}">C</figure-callout>}1}}\&GreaterEqual;3f$

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 utility model, in above-mentioned the utility model specific embodiment, it is as follows 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 utility model specific embodiment is as follows: 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 Pspicel0.0 novel circuit has been carried out emulation, parameter is as follows: 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).Can draw from simulation result 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 by 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, experimental result shows: circuit of the present utility model has very high efficient (about 95%), prior art is 92% with the efficient of hard switching circuit, and the efficient of the utility model soft switch circuit brings up to about 95%.

All power switchs are soft switch in the utility model, 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; it only is the preferable embodiment of the utility model; but protection range of the present utility model is not limited thereto; anyly be familiar with those skilled in the art in the technical scope that the utility model discloses; the variation that can expect easily or replacement all should be encompassed within the protection range of the present utility model.

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 described 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), second switch pipe (T2) is parallel with second electric capacity (C2), be 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 negative terminal of the tie point of first switching tube (T1) and second switch pipe (T2) and 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), the negative terminal of direct-current input power supplying (UI) negative terminal and dc output end links together, and described 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, described 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 described 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 described filter inductance (L) is

$L=\frac{\mathrm{Uo}(1-d)\mathrm{Ts}}{{\mathrm{\&Delta;i}}_L}$

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 described linear change of current branch road inductance (Lx) satisfies:

$\mathrm{Lx}\&GreaterEqual;\frac{\mathrm{Uo}(1-D)\mathrm{TsTd}}{\mathrm{IoTd}+\mathrm{UI}({C1}^{\&prime;}+{C2}^{\&prime;})}$

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 described linear change of current branch road electric capacity (Cx) is:

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

In the formula, U _CxBe linear change of current electric capacity (Cx) both end 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 described second electric capacity (C2) satisfies:

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

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 described 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 described first inductance (L1) satisfies:

$\frac{1}{2\mathrm{\&pi;}\sqrt{L1C1}}=f1\&GreaterEqual;3f$

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.

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