CN101795066B - Interleaved switching method of Buck-Boost convertor and realization circuit thereof - Google Patents

Abstract

The invention provides an interleaved switching method of a Buck-Boost convertor and a realization circuit thereof, wherein the Buck-Boost convertor comprises a first PWM (Pulse-Width Modulation) chip, a second PWM chip, a third PWM chip, a first optical coupler, a second optical coupler, a high-end driving chip and a low-end driving chip; and the interleaved switching method is characterized in that the phases of a Buck switching tube and a Boost switching tube are shifted by 180 degrees at the switching-on moment, the Buck switching tube and the Boost switching tube have equal duty cycles, the change range of the duty cycles is 0-1, and the Buck switching tube and the Boost switching tube have no mode switching. A switching control circuit of the Buck-Boost convertor minimizes energy-storage inductance, improves the efficiency of the convertor and has the advantages of no switching of working modes, simple realization and good working property; and two paths of PWM signals outputted by an interleaved driving signal generating circuit has good consistency of the duty cycles.

Description

The interleaved switching method of Buck-Boost converter and realization circuit thereof

Technical field

The present invention relates to a kind of ON-OFF control circuit of Buck-Boost converter, especially a kind of staggered driving signal is realized circuit, belongs to the switch control field of DC converter.

Background technology

Use the rooftop applications field at photovoltaic door, the array power grade is generally 2～5kW, by the about 200～700VDC of a plurality of solar panels series connection output voltages, its wide input voltage range is brought very big challenge to the optimal design of single stage type combining inverter, the two-stage type structure can make system level optimization and control, therefore the whole system design is very convenient, and present photovoltaic combining inverter generally adopts the two-stage type structure.The prime DC converter is mainly finished cell voltage to conversion and the MPPT maximum power point tracking (MPPT) of intermediate-bus voltage in the two-stage type structure, and non-isolated DC converter is not owing to being with high frequency transformer can improve conversion efficiency.Generally adopt now the Boost converter, when cell voltage is low, realize boost function, realize simultaneously step-down and the function that is incorporated into the power networks if the cell voltage rising then stops the Boost converter by the rear class inverter, will certainly increase like this capacity of inverter.

Two-tube Buck-Boost converter has input and output voltage same polarity and buck characteristic, is fit to be applied to the prime DC converting of the two-stage type combining inverter of wide input voltage.In the existing document, two-tube Buck-Boost converter mainly contains synchro switch and two kinds of control modes of unit switch.Two switching tubes turn on and off simultaneously under the synchro switch mode, need larger energy storage inductor, are unfavorable for the improvement of transducer effciency and volume size; And the unit switch mode is to be operated in the Boost pattern when input voltage is lower than output voltage, and the Buck pipe is in pass-through state, and works in the Buck pattern when input voltage is higher than output voltage, and the Boost pipe is in off state.The unit switch mode can reduce switching loss, but seamlessly transitting of two kinds of mode of operations is very difficult, needs complicated control logic and control circuit to realize.

Summary of the invention

Goal of the invention:

The objective of the invention is for the synchro switch that overcomes the Buck-Boost converter and the defective under the unit switch mode, a kind of ON-OFF control circuit that energy storage inductor reduces, conversion efficiency improves and need not to seamlessly transit control that can realize the Buck-Boost converter is provided.

Technical scheme:

The present invention adopts following technical scheme for achieving the above object:

A kind of interleaved switching method of Buck-Boost converter, the constantly phase shift 180 of opening of Buck switching tube and Boost switching tube is spent, and the duty ratio equal and opposite in direction, and the change in duty cycle scope is 0～1, and non-mode switches.

A kind of realization circuit of the present invention comprises that a PWM chip, the 2nd PWM chip, the 3rd PWM chip, the first photo coupler, the second photo coupler, high-side driver chip, low side drive chip;

Wherein the 14th pin of a PWM chip is connected with the 4th pin of the 2nd PWM chip, and the 11st pin of a PWM chip is connected with the 4th pin of the 3rd PWM chip, the fixing narrow duty cycle control signal of the 9th pin output of a PWM chip;

The 14th pin of the 2nd PWM chip, the 11st pin are respectively with after diode is connected, be connected with the input of the first photo coupler, the output of the first photo coupler connects the input of high-side driver chip, the drive end of the output termination Buck switching tube of high-side driver chip;

The 14th pin of the 3rd PWM chip, the 11st pin are respectively with after diode is connected, be connected with the input of the second photo coupler, the output of the second photo coupler connects the input that low side drives chip, and low side drives the drive end of the output connection Boost switching tube of chip;

The 9th pin of the 2nd PWM chip is connected the output duty cycle control signal with the 9th pin of the 3rd PWM chip.

Beneficial effect:

Can there be the switching of mode of operation in the ON-OFF control circuit of Buck-Boost converter of the present invention so that energy storage inductor is minimum and the raising transducer effciency, realizes that simply operating characteristic is good; The two-way pwm signal duty ratio size identical property of staggered drive signal generation circuit output is good.

Description of drawings

Fig. 1 is the main circuit structure schematic diagram of the applied Buck-Boost converter of the present invention;

Fig. 2 is that the staggered driving signal of Buck-Boost converter of the present invention is realized electrical block diagram;

Fig. 3 (a)～(b) is interleaved switching mode working waveform figure of the present invention, (a) U _Pv＞U _Dc, (b) U _Pv＜U _Dc

Fig. 4 (a)～(d) is the operation mode of interleaved switching mode downconverter of the present invention, (a) S ₁Open, S ₂Open, (b) S ₁Shutoff, S ₂Shutoff, (c) S ₁Open, S ₂Shutoff, (d) S ₁Shutoff, S ₂Open-minded;

Fig. 5 (a)～(c) is the experimental waveform of the present invention on Buck-Boost converter embodiment, (a) U _Pv=250V, U _Dc=375V, P _o=2.8kW, (b) U _Pv=370V, U _Dc=375V, P _o=2.8kW, (c) U _Pv=450V, U _Dc=375V, P _o=2.8kW, scale is ch1:S among the figure ₁Drive signal, 10V/div; Ch2:S ₂Drive signal, 10V/div; Ch3: inductance L both end voltage, 200V/div; Ch4: flow through the inductance L electric current, 3.75A/V.

The main symbol of above-mentioned accompanying drawing and label title: U _Pv---the solar panel output voltage; L---energy storage inductor; S ₁, S ₂---power switch pipe; D ₁, D ₂---power diode; C _Pv---the battery side electrochemical capacitor; C _Dc---the bus bar side decoupling capacitance; U _Dc---intermediate-bus voltage; u _L---the voltage on the energy storage inductor L.

Embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated:

As shown in Figure 1, be enforcement main circuit of the present invention, it comprises Buck switching tube S ₁With diode D ₁, Boost switching tube S ₂With diode D ₂, intermediate energy storage inductance L, bus solution lotus root capacitor C _Dc

As shown in Figure 2, the staggered driving signal of Buck-Boost converter is realized circuit, comprises that a PWM chip, the 2nd PWM chip, the 3rd PWM chip, the first photo coupler, the second photo coupler, high-side driver chip, low side drive chip; Wherein the 14th pin of a PWM chip is connected with the 4th pin of the 2nd PWM chip, and the 11st pin of a PWM chip is connected with the 4th pin of the 3rd PWM chip, the fixing narrow duty cycle control signal of the 9th pin output of a PWM chip; The 14th pin of the 2nd PWM chip, the 11st pin are respectively with after diode is connected, be connected with the input of the first photo coupler, the output of the first photo coupler connects the input of high-side driver chip, the drive end of the output termination Buck switching tube of high-side driver chip; The 14th pin of the 3rd PWM chip, the 11st pin are respectively with after diode is connected, be connected with the input of the second photo coupler, the output of the second photo coupler connects the input that low side drives chip, and low side drives the drive end of the output connection Boost switching tube of chip;

Interleaved switching mode of the present invention is: Buck switching tube S ₁With Boost switching tube S ₂Open constantly phase shift 180 degree, and duty ratio equal and opposite in direction, the change in duty cycle scope is 0～1.Need not mode of operation switches.Accompanying drawing 3 and accompanying drawing 4 are respectively steady operation oscillogram and the operation mode equivalent electric circuit under the control mode of the present invention.Obtained the expression formula of input/output relation and the inductance value of converter by inductance " weber balance ":

$\frac{U_{\mathrm{dc}}}{U_{\mathrm{pv}}}=\frac{D}{1-D}---\left(1\right)$

$L=\left\{\begin{array}{c}\frac{(U_{\mathrm{pv}}-U_{\mathrm{dc}})U_{\mathrm{dc}}}{(U_{\mathrm{pv}}+U_{\mathrm{dc}})\mathrm{\&Delta;}{\mathrm{if}}_s},0.5>D<\frac{\mathrm{\&phi;}}{360}\mathrm{and}\frac{\mathrm{\&phi;}}{360}+D<1\\ \frac{U_{\mathrm{pv}}{U}_{\mathrm{dc}}/(U_{\mathrm{pv}}+U_{\mathrm{dc}})-U_{\mathrm{pv}}(1-\mathrm{\&phi;}/360)}{\mathrm{\&Delta;}{\mathrm{if}}_s},0.5<D<\frac{\mathrm{\&phi;}}{360}\mathrm{and}\frac{\mathrm{\&phi;}}{360}+D>1\\ \frac{U_{\mathrm{pv}}{U}_{\mathrm{dc}}/(U_{\mathrm{pv}}+U_{\mathrm{dc}})-U_{\mathrm{dc}}(1-\mathrm{\&phi;}/360)}{\mathrm{\&Delta;}{\mathrm{if}}_s},0.5>D<\frac{\mathrm{\&phi;}}{360}\mathrm{and}\frac{\mathrm{\&phi;}}{360}+D>1\\ \frac{U_{\mathrm{pv}}{U}_{\mathrm{dc}}/(U_{\mathrm{pv}}+U_{\mathrm{dc}})-U_{\mathrm{pv}}\mathrm{\&phi;}/360}{\mathrm{\&Delta;}{\mathrm{if}}_s},0.5<D>\frac{\mathrm{\&phi;}}{360}\mathrm{and}\frac{\mathrm{\&phi;}}{360}+D<1\\ \frac{U_{\mathrm{pv}}{U}_{\mathrm{dc}}/(U_{\mathrm{pv}}+U_{\mathrm{dc}})-U_{\mathrm{dc}}\mathrm{\&phi;}/360}{{\mathrm{\&Delta;if}}_s},0.5>D>\frac{\mathrm{\&phi;}}{360}\mathrm{and}\frac{\mathrm{\&phi;}}{360}+D<1\\ \frac{U_{\mathrm{pv}}(U_{\mathrm{dc}}-U_{\mathrm{pv}})}{(U_{\mathrm{pv}}+U_{\mathrm{dc}}){\mathrm{\&Delta;if}}_s},0.5>D>\frac{\mathrm{\&phi;}}{360}\mathrm{and}\frac{\mathrm{\&phi;}}{360}+D>1\end{array}\right.---\left(2\right)$

On-off mode of the present invention does not change the input and output voltage relation of converter under former synchro switch mode, but energy storage inductor current pulsation amount identical condition under can be so that required energy storage inductor sense value be minimum.

Interleaved switching drive waveforms of the present invention produces circuit and comprises PWM chip SG3525-1, SG3525-2, SG3525-3, light lotus root 1 and 2, and high-side driver chip and low side drive chip.The burst pulse of SG3525-1 generation phase shift 180 degree accesses respectively the 4 pin oscillator output end OSC OUTPUT of SG3525-2 and SG3525-3, guaranteed that SG3525-2 is consistent with SG3525-3 sawtooth waveforms frequency, phase shift 180 degree, can guarantee that especially the maximum of both sawtooth waveforms, minimum value are consistent, guarantee the consistency of output duty cycle size.Interleaved switching drive waveforms of the present invention produces circuit and forms by integrated chip, and required board area is little, reliability is high.

Example of the present invention is as follows: cell plate voltage U _Pv=200～550V, line voltage U _Grid=220VRMS, mains frequency f _Grid=50Hz, rated power P _N=3kW; Inductance L=0.36mH, bus capacitor C=2820 μ F, busbar voltage U _Dc=375V, power switch S ₁, S ₂-3 * STY60NM60, power diode D ₁, D ₂-3 * RHRG5060; Switching frequency f=50kHZ.Accompanying drawing 5 is the concrete experimental waveform figure of this example.

The interleaved switching mode of the switch control of Buck-Boost converter of the present invention is: the constantly phase shift 180 of opening of Buck switching tube and Boost switching tube is spent, and the duty ratio equal and opposite in direction, and the change in duty cycle scope is 0～1, switches without mode of operation.

Switch control when the present invention is equally applicable to the Buck-Boost converter and works in the SPWM mode.

Switch control when the present invention is equally applicable to the Boost-Buck cascade converter and works with SPWM or PWM mode.

Claims (1)

1. circuit that is used for realizing the interleaved switching method of two-tube Buck-Boost converter, the interleaved switching method of described two-tube Buck-Boost converter is: the constantly phase shift 180 of opening of Buck switching tube and Boost switching tube is spent, and duty ratio equal and opposite in direction, the change in duty cycle scope is 0～1, and non-mode switches; It is characterized in that: be used for realizing that the circuit of this interleaved switching method comprises that a PWM chip, the 2nd PWM chip, the 3rd PWM chip, the first photo coupler, the second photo coupler, high-side driver chip, low side drive chip; The model of a described PWM chip, the 2nd PWM chip, the 3rd PWM chip is SG3525;

Wherein the 14th pin of a PWM chip is connected with the 4th pin of the 2nd PWM chip, and the 11st pin of a PWM chip is connected with the 4th pin of the 3rd PWM chip, the fixing narrow duty cycle control signal of the 9th pin output of a PWM chip;

The 14th pin of the 2nd PWM chip, the 11st pin are respectively with after diode is connected, be connected with the input of the first photo coupler, the output of the first photo coupler connects the input of high-side driver chip, the drive end of the output termination Buck switching tube of high-side driver chip;

The 14th pin of the 3rd PWM chip, the 11st pin are respectively with after diode is connected, be connected with the input of the second photo coupler, the output of the second photo coupler connects the input that low side drives chip, and low side drives the drive end of the output connection Boost switching tube of chip;

The 9th pin of the 2nd PWM chip is connected the output duty cycle control signal with the 9th pin of the 3rd PWM chip.

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