CN101795066A - 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 drive signal realizes circuit, belongs to the switch control field of DC converter.

Background technology

Use the rooftop applications field at the photovoltaic family, the array power grade is generally 2～5kW, by the about 200～700VDC of a plurality of solar panel series connection output voltages, its wide input voltage range brings very big challenge for 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 conversion and the MPPT maximum power point tracking (MPPT) of cell voltage to intermediate-bus voltage in the two-stage type structure, and non-isolated DC converter is not owing to be with high frequency transformer can improve conversion efficiency.Generally adopt the Boost converter now, when cell voltage is low, realize boost function,, will certainly increase the capacity of inverter like this if cell voltage rising then stopping Boost converter is realized the step-down and the function that is incorporated into the power networks simultaneously by back level 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.Following two switching tubes of synchro switch mode turn on and off simultaneously, need bigger 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 phase shift constantly 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 a PWM chip, the 2nd PWM chip, the 3rd PWM chip, first photo coupler, second photo coupler, high-side driver chip, low side chip for driving;

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 first photo coupler, the output of 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 second photo coupler, the output of second photo coupler connects the input of low side chip for driving, and the output of low side chip for driving connects the drive end of Boost switching tube;

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 drive signal of Buck-Boost converter of the present invention realizes electrical block diagram;

Fig. 3 (a)～(b) is an 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 separate the lotus root capacitor C _Dc

As shown in Figure 2, the staggered drive signal of Buck-Boost converter realizes circuit, comprises a PWM chip, the 2nd PWM chip, the 3rd PWM chip, first photo coupler, second photo coupler, high-side driver chip, low side chip for driving; 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 first photo coupler, the output of 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 second photo coupler, the output of second photo coupler connects the input of low side chip for driving, and the output of low side chip for driving connects the drive end of Boost switching tube;

Interleaved switching mode of the present invention is: Buck switching tube S ₁With Boost switching tube S ₂Open 180 degree of phase shift constantly, 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.Obtain the expression formula of the 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 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, high-side driver chip and low side chip for driving.The burst pulse of SG3525-1 generation phase shift 180 degree inserts the 4 pin oscillator output end OSC OUTPUT of SG3525-2 and SG3525-3 respectively, guaranteed that SG3525-2 is consistent with SG3525-3 sawtooth waveforms frequency, phase shift 180 degree, can guarantee maximum, the minimum value unanimity of both sawtooth waveforms especially, guarantee the consistency of output duty cycle size.Interleaved switching drive waveforms of the present invention produces circuit to be formed 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 phase shift constantly 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 no mode of operation is switched.

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 (2)

1. the interleaved switching method of a Buck-Boost converter is characterized in that: Buck switching tube and Boost switching tube open 180 degree of phase shift constantly, and duty ratio equal and opposite in direction, the change in duty cycle scope is 0～1, non-mode switches.

2. a circuit that is used to realize the interleaved switching method of the described Buck-Boost converter of claim 1 is characterized in that: comprise a PWM chip, the 2nd PWM chip, the 3rd PWM chip, first photo coupler, second photo coupler, high-side driver chip, low side chip for driving;

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 first photo coupler, the output of 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 second photo coupler, the output of second photo coupler connects the input of low side chip for driving, and the output of low side chip for driving connects the drive end of Boost switching tube;

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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