CN204179944U - A kind of Sofe Switch DC-DC conversion circuit - Google Patents

Abstract

The utility model discloses a kind of Sofe Switch DC-DC conversion circuit, comprise direct-flow input end, DC output end.Direct-flow input end (U _in) positive polarity with connect between load (R) have main switch (S ₁) and filter inductance (L); Main switch (S ₁) with the tie point of filter inductance (L) and direct-flow input end (U _in) negative polarity between connect have fly-wheel diode (D), inductance (L _r) and diode (D ₂) and electric capacity (C ₃) series arm, resistance (R) is in parallel with electric capacity (C); Main switch (S ₁) in parallel there is electric capacity (C ₁), diode (D ₁), auxiliary switch (S ₂) and electric capacity C ₂in parallel; Main switch (S ₁) and auxiliary switch (S ₂) be all Sofe Switch.Main switch (S ₁) be ZCS and ZVS unlatching and ZVS shutoff, auxiliary switch (S ₂) be that ZVS opens and ZVS turns off, fly-wheel diode (D) is that ZVS opens and ZCS turns off; Sofe Switch can be realized within the scope of duty cycle adjustment.

Description

A kind of Sofe Switch DC-DC conversion circuit

Technical field

The utility model relates to a kind of DC-DC conversion circuit, particularly relates to a kind of buck chopper translation circuit.

Background technology

Brushless DC motor has that volume is little, efficiency advantages of higher, is widely used in a lot of fields.In more than ten years in the past, the development of brshless DC motor mainly concentrates on the research of control method and the design and optimization of topological structure, but, the translation circuit topological structure of major part brshless DC motor is all utilize hard switching technology, this just causes very large switching loss and electromagnetic interference accordingly, and simultaneously in order to make the volume of translation circuit reduce, increasing switching frequency is only way, but this also brings loss to increase accordingly, and soft switch technique can address these problems.Although design various soft switch conversion circuit, such as zero voltage switch resonant circuit, zero voltage switch circuit, zero-current switching circuit etc., but for the feature of brshless DC motor, requirement electric current is little, and response is fast, and torque pulsation is steady, harmonic components is few, loss is low, the requirements such as the large and duty cycle adjustment wide ranges of load variations scope, various soft switch conversion circuit has respective shortcoming, is not used widely on brshless DC motor.Zero voltage switch quasi-resonance circuit (ZVS-QRC), although current stress is little, voltage stress is large, and voltage stress and load proportional, it is only suitable for the circuit being applied to input voltage and load variations narrow range.Zero voltage switch multi-resonant circuit (ZVS-MRC), although voltage stress is little, loading range is wide, and conduction loss is larger.Resonance DC loop circuit (RDCLI) is although electric current and voltage stress is little, and loading range is large, and its control principle is complicated, there is the phenomenon of electromagnetic torque pulsation and Torque ripple, and containing subharmonic in output circuit.Zero voltage transition circuit (ZVT), resonant tank, although it is so can effective Loss reducing not on major loop, but has certain restriction to the selection of power tube.Zero-current switching circuit (ZCT), switch conduction and turn-off power loss are all very little, can realize ZCS, and current/voltage stress is also very little, but the device that it uses is many, and control procedure is complicated.

Utility model content

Technology of the present utility model is dealt with problems and is: for the feature of brushless DC motor and the deficiency of translation circuit, provides that a kind of loss is low, efficiency is high, control simple Sofe Switch DC-DC conversion circuit.

The technical scheme that the utility model technical solution problem adopts is:

The utility model Sofe Switch DC-DC conversion circuit, comprises direct-flow input end and DC output end, it is characterized in that direct-flow input end U _inpositive polarity and the first switching tube S ₁collector electrode, second switch pipe S ₂collector electrode be connected, the first switching tube S ₁with the first electric capacity C ₁, the first diode D ₁parallel connection, second switch pipe S ₂with the second electric capacity C ₂parallel connection, resonant inductance L _rtwo ends and the first switching tube S ₁emitter and second switch pipe S ₂emitter be connected, the second diode D ₂with the 3rd electric capacity C ₃with resonance inductance L _rseries connection, the first diode D ₁negative electrode and direct-flow input end U _inpositive polarity be connected, the second diode D ₂anode and the 3rd electric capacity C ₃be connected, the negative electrode of the 3rd diode D and the first switching tube S ₁emitter be connected, the anode of the 3rd diode D and direct-flow input end U _innegative polarity be connected, the two ends of filter inductance L and the first switching tube S ₁emitter be connected with load R, the 4th electric capacity C is in parallel with load R.

The utility model Sofe Switch DC-DC conversion circuit topological structure as shown in Figure 1, is described in detail operation principle of the present utility model below:

Process to simplify the analysis, first do basic assumption:

(1) translation circuit is operated in stable state;

(2) all power switchs, diode are all ideal component;

(3) inductance, electric capacity are desirable energy-storage travelling wave tube;

(4) input voltage is constant;

(5) output inductor is enough large, makes the electric current flowing through filter inductance can regard constant current I as ₀;

(6) resonant inductance is far smaller than filter inductance;

A switch periods, suppose that this circuit working is under continuous operation mode, the utility model can be divided into 7 operating states, and the equivalent circuit diagram of its each operating state is as shown in Fig. 2 a-2g.

Working stage 1 [t ₀, t ₁]: at t ₀before moment, switching tube S ₁, S ₂all be in off state, as shown in Figure 2 a, inductance L passes through diode D afterflow to its equivalent electric circuit, now, and i _s1=0, i _s2=0, i _lr=0, U _c2=U _in.T=t ₀moment, S ₁conducting, due to the existence of inductance L, switching tube S ₁electric current be restricted, can not suddenly change immediately, realize zero current passing, meanwhile, inductance L _rin current i _lrlinear rising.Because the value of inductance L is relatively large, its current i _lapproximately constant, namely has I _l=I ₀, so the electric current in main diode D is along with i _s1rising and linearly decline, i _s1with i _dcan be expressed as:

$i_{S_1}\left(t\right)=\frac{U_{\mathrm{in}}}{L_r}(t-t_0)---\left(1\right)$

$i_D\left(t\right)=I_0-\frac{U_{\mathrm{in}}}{L_r}\left(t{-t}_0\right)---\left(2\right)$

This phase duration is:

$T_{01}=\frac{L_r{I}_0}{U_{\mathrm{in}}}---\left(3\right)$

At this stage switch pipe S ₁zero current passing, i.e. switching tube S ₁turn-on consumption is zero.

Working stage 2 [t ₁, t ₂]: t=t ₁moment, i _s1(t ₁)=I ₀, i _d(t ₁)=0, as shown in Figure 2 b, diode D is zero-current switching to its equivalent electric circuit.After this, electric capacity C ₂and inductance L _rthere is series resonance, resonant inductance L _relectric current and electric capacity C ₂terminal voltage expression formula is as follows:

$i_{L_r}\left(t\right)=I_0+\frac{U_{\mathrm{in}}}{Z_p}\sin \mathrm{\ω}(t-t_1)---\left(4\right)$

u _C2(t)＝U _incosω(t-t ₁) (5)

Wherein, $\mathrm{\ω}=\frac{1}{\sqrt{L_r{C}_2}},Z_p=\sqrt{\frac{L_r}{C_2}}.$

Work as U _c2when reducing to zero, L _ron electric current reach maximum now electric capacity C ₂on energy storage all transfer to resonant inductance L _ron, resonant inductance L _ron current increment Δ I _lrmeet equation below:

$\frac{1}{2}{C}_2{U}_{C_2}^2\left(t\right)=\frac{1}{2}{C}_2{U}_{\mathrm{in}}^2=\frac{1}{2}{L}_r\mathrm{\Δ}{I}_{L_r}^2---\left(6\right)$

Be zero-current switching at this stage diode D, so diode D turn-off power loss is zero.

Working stage 3 [t ₂, t ₃]: work as t=t ₂time, U _c2reduce to zero, its equivalent electric circuit as shown in Figure 2 c, now auxiliary switch S ₂conducting be ZVS open.

At this stage switch pipe S ₂for no-voltage is open-minded, so switching tube S ₂turn-on consumption be zero.

Working stage 4 [t ₃, t ₄]: at t=t ₃time, shutdown switch S ₁, its equivalent electric circuit as shown in Figure 1 d.

Now, from equivalent circuit diagram, electric capacity C ₁with main switch S ₁in parallel, and electric capacity C ₁the voltage at two ends slowly rises, so switch S ₁that ZVS turns off.

At this stage switch pipe S ₁that ZVS turns off, so switching tube S ₁turn-off power loss is zero.

Working stage 5 [t ₄, t ₅]: in this stage, this circuit is identical with traditional BUCK circuit working state, and circuit is by a switching tube S ₂carry out work, its equivalent electric circuit as shown in Figure 2 e.

Working stage 6 [t ₅, t ₆]: work as t=t ₅time, on-off switching tube S ₂, its equivalent electric circuit as shown in Figure 1 f, now starts to electric capacity C ₂charging, its terminal voltage slowly rises, so switching tube S ₂the approximate ZVS that achieves turns off.Work as U _c1(t)+U _c3(t)=U _intime, diode D ₂that ZVS opens.At t=t ₆time, U _c1(t ₆)=U _in, U _c3(t ₆)=0, diode D ₂achieve ZVS to turn off.

At this stage switch pipe S ₂for ZVS turns off, so switching tube S ₂turn-off power loss is zero, simultaneously diode D ₂for no-voltage turns on and off, so diode D ₂the loss that turns on and off also be zero.

Working stage 7 [t ₆, t ₇]: t=t ₆time, C ₁, C ₂, C ₃both end voltage be all zero, its equivalent electric circuit as shown in Figure 2 g, now sustained diode afterflow, achieve ZVS open, this stage is identical with traditional BUCK circuitry operating conditions.T=t ₇time, switching tube S ₂again open, start to enter the circulation of next switch periods.

This stage diode D be ZVS open, so diode D turn-on consumption is zero.

The utility model has the advantages that while realizing circuit function, all power switch pipes are Sofe Switch, what greatly reduce switching tube turns on and off loss, and the electric current of power switch pipe, voltage stress are less, the conduction loss of switching tube is also reduced, this circuit structure is simple simultaneously, control is convenient, can realize Sofe Switch within the scope of whole duty cycle adjustment.

Accompanying drawing explanation

Fig. 1 is the topological structure of the utility model Sofe Switch DC-DC conversion circuit;

Fig. 2 a is the equivalent circuit diagram of the utility model Sofe Switch DC-DC conversion circuit working stage 1;

Fig. 2 b is the equivalent circuit diagram of the utility model Sofe Switch DC-DC conversion circuit working stage 2;

Fig. 2 c is the equivalent circuit diagram of the utility model Sofe Switch DC-DC conversion circuit working stage 3;

Fig. 2 d is the equivalent circuit diagram of the utility model Sofe Switch DC-DC conversion circuit working stage 4;

Fig. 2 e is the equivalent circuit diagram of the utility model Sofe Switch DC-DC conversion circuit working stage 5;

Fig. 2 f is the equivalent circuit diagram of the utility model Sofe Switch DC-DC conversion circuit working stage 6;

Fig. 2 g is the equivalent circuit diagram of the utility model Sofe Switch DC-DC conversion circuit working stage 7;

Fig. 3 is main switch S in the utility model Sofe Switch DC-DC conversion circuit ₁and auxiliary switch S ₂drive signal waveform figure;

Embodiment

The utility model Sofe Switch DC-DC conversion circuit preferably execution mode as shown in Figure 1, comprises direct-flow input end, DC output end, is provided with positive pole circuit and negative pole circuit between direct-flow input end and DC output end, and what positive pole circuit was connected has main switch S ₁with filter inductance L, auxiliary switch S ₂in parallel has electric capacity C ₂, main switch S ₁in parallel has diode D ₁, main switch S ₁with tie point and the direct-current input power supplying U of filter inductance L _innegative polarity between connect have sustained diode, the series arm be made up of filter inductance L and filter capacitor C of sustained diode parallel connection, resonant inductance L _rwith diode D ₂with electric capacity C ₃the series arm of composition.Main switch S ₁with auxiliary switch S ₂be respectively Sofe Switch.

In FIG, L is filter inductance, L _rresonant inductance, and L>>L _r; S ₁main switch, S ₂be auxiliary switch, D is fly-wheel diode, and R is the steady-state equivalent load of brshless DC motor.Main switch S in this topological structure ₁achieve ZCS (Zero Current Switch) and ZVS (zero voltage switch) unlatching and ZVS shutoff, auxiliary switch S ₂achieve ZVS to open and ZVS shutoff, sustained diode achieves ZVS and opens and ZCS shutoff.

As shown in Figure 3, main switch S is respectively ₁with auxiliary switch S ₂drive signal waveform, main switch S as we know from the figure ₁auxiliary switch S in advance ₂opening, is auxiliary switch S ₂zVS open create conditions, as main switch S ₁during unlatching, owing to having filter inductance L and resonance inductance L _rexistence, main switch S ₁electric current can not suddenly change immediately, so main switch S ₁for ZCS opens; As resonant inductance L _rwith resonant capacitance C ₂when there is resonance, this moment auxiliary switch S ₂both end voltage is zero, now opens auxiliary switch S ₂for ZVS opens, again due to auxiliary switch S ₂electric current be also zero, so auxiliary switch S ₂also for ZCS opens; As main switch S ₁during shutoff, electric capacity C ₁both end voltage slowly rises, so main switch S ₁for ZVS turns off; As shutoff auxiliary switch S ₂time, start to electric capacity C ₂charging, electric capacity C ₂both end voltage slowly rises, so auxiliary switch S ₂for ZVS turns off.

In a word, the power switch tube S in the utility model topological structure ₁, S ₂be all Sofe Switch, so have less power loss, higher efficiency.

Below the realization condition of the utility model Sofe Switch is described in detail:

(1) this circuit to be realized and can realize Sofe Switch condition in whole loading range from zero load to load, just must meet inequality:

I _0.max≤I _S1.max(9)

I _0.maxfor output inductor current maxima.

(2) if diode D ₁there is not conducting time delay and switch S ₁there is not leakage current, at any time opening switch S of mode 3 ₂be all no-voltage and zero current passing.

(3) switching tube S ₁should at t ₅turned off before moment, if at t ₅moment does not still turn off, then in inductance L _rwith electric capacity C ₃on then there is circuit oscillation, Simultaneous Switching pipe S ₂electric current increase fast, be a significant increase switching tube S ₁conduction loss and turn-off power loss.

Below the design of the utility model soft switch circuit parameter is described in detail:

(1) selection of inductance L

Require that circuit working is under continuous operation mode, under high frequency situation, in inductance, the filtered electric capacity C of most of harmonic current absorbs, therefore, it is too little that output inductor can not select, otherwise, inductive current pulsation can be made sharply to increase, and the maximum current flowing through switching tube also can increase, and the operating state of switching tube is worsened.Be Δ i in the maximum induction current pulsation of given license _pp, output inductor L demand fulfillment:

$L\≥\frac{1-D}{2f_s}R---\left(10\right)$

$L\≥\frac{U_i-U_0}{\mathrm{\Δ}{i}_{\mathrm{pp}}{f}_s}D---\left(11\right)$

F _sfor switching frequency, D is duty ratio.

(2) selection of electric capacity C

Output capacitance C is obtained by following formula:

$C\≥\frac{U_0}{8L{f}_s^2\mathrm{\Δ}{U}_0}(1-D)---\left(12\right)$

Δ U ₀for output ripple component.

(3) resonant inductance L _rselection

First, L _rshould not obtain excessive, otherwise can make the overlong time of working stage 2, so just limit the operating frequency of switch, it can not obtain too little, L _rtime too little, Δ I _lrcan be very large, which adds the conduction loss of switching tube.In engineering design, general Δ t ₁=(t ₂-t ₁)=0.02D _s1t _s, L can be calculated according to (1) formula like this _rvalue:

$L_r=\frac{U_{L_r}\mathrm{\Δ}{t}_2}{i_{L_r}\left(t_1\right)}=\frac{0.01D_{S_1}{T}_s{U}_{\mathrm{in}}}{I_0}---\left(13\right)$

(4) resonant capacitance C ₂selection

In order to make switching tube S ₂open under ZVS condition, be stored in electric capacity C ₂on energy all must transfer to inductance L when working stage 2 _ron, therefore C ₂meet following formula:

$C_2=\frac{L_r\mathrm{\Δ}{I}_{L_r}^2}{U_{\mathrm{in}}^2}---\left(14\right)$

Test at 4Kw brshless DC motor; brushless DC motor control system topological structure comprises rectification circuit, soft switch BUCK circuit, three phase bridge circuit, logic control circuit and isolation drive protective circuit; wherein three phase bridge circuit is only responsible for commutation; do not modulate; can avoid like this in son, producing very large iron loss because stator current modulating frequency is very high fixed turning; also can reduce motor eddy current loss, thus reduce motor power consumption.Experiment condition is: input voltage U=540V, output voltage U ₀=162V, switching frequency f=20kHZ, duty ratio D=0.3.Experimental result shows: the utility model Sofe Switch DC-DC conversion circuit has higher efficiency, utilizes numerical integrating computational efficiency to be approximately 92%, improves 3% than the hard switching BUCK translation circuit used now.

Power switchs all in the utility model is Sofe Switch, reduces switching loss, improve the delivery efficiency of circuit, and circuit components is less, and structure is simple, and it is convenient to control, and enhances the reliability of system.

The above; be only the utility model preferably embodiment; 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; change can be expected easily or replace, all should be encompassed within protection range of the present utility model.

Claims (3)

1. a Sofe Switch DC-DC conversion circuit, comprises direct-flow input end and DC output end, it is characterized in that direct-flow input end U _inpositive polarity and the first switching tube S ₁collector electrode, second switch pipe S ₂collector electrode be connected, the first switching tube S ₁with the first electric capacity C ₁, the first diode D ₁parallel connection, second switch pipe S ₂with the second electric capacity C ₂parallel connection, resonant inductance L _rtwo ends and the first switching tube S ₁emitter and second switch pipe S ₂emitter be connected, the second diode D ₂with the 3rd electric capacity C ₃with resonance inductance L _rseries connection, the first diode D ₁negative electrode and direct-flow input end U _inpositive polarity be connected, the second diode D ₂anode and the 3rd electric capacity C ₃be connected, the negative electrode of the 3rd diode D and the first switching tube S ₁emitter be connected, the anode of the 3rd diode D and direct-flow input end U _innegative polarity be connected, the two ends of filter inductance L and the first switching tube S ₁emitter be connected with load R, the 4th electric capacity C is in parallel with load R, the second electric capacity C ₂with resonant inductance L _rcomposition resonant circuit.

2. Sofe Switch DC-DC conversion circuit as claimed in claim 1, is characterized in that: the first switching tube S ₁, second switch pipe S ₂for controllability power device, the 3rd diode D, the first diode D ₁, the second diode D ₂for fast restorative diode.

3. Sofe Switch DC-DC conversion circuit as claimed in claim 1, is characterized in that: filter inductance L is greater than resonant inductance L _rmore than 200 times.