CN205356155U - Single tube buck -Boost -flyback voltage step -up and step -down typed circuit - Google Patents

Abstract

The utility model discloses a single tube buck -Boost -flyback voltage step -up and step -down typed circuit, include: DC power supply, MOSFET switch tube, the turn ratio 1: N's transformer, first diode, second diode, first electric capacity, second electric capacity, the utility model discloses a voltage step -up and step -down typed circuit presses formula DC -DC circuit and isolated flyback circuit to combine buck -boost's lift, realize the lift transform of DC voltage, the transformer that wherein turn over to swash the formula circuit (former limit inductance and leakage inductance) the inductance as the buck -Boost circuit that once inclines, it turns over to have eliminated swashs inefficiency and the too high scheduling problem of switch tube voltage stress that topological leakage inductance leads to, the efficiency of the converter is improved with the voltage gain under the mode of stepping up.

Description

A kind of single tube Buck-Boost-flyback buck-boost type circuit

Technical field

This utility model belongs to electric and electronic technical field, relates to a kind of buck-boost type circuit, particularly relates to a kind of single tube Buck-Boost-flyback buck-boost type circuit.

Background technology

DC dc converter (abbreviation DC-DC converter) is the galvanic Power Electronic Circuit topology that the unidirectional current of a kind of electric pressure is changed into other electric pressure.The power supplys such as current communication equipment, integrated circuit and various electronic product charging adapters are DC source, all refer to DC-DC converter in their Power Management Design.So DC source has extremely wide application market and application.

Electric energy is one of basic energy resource of modern society, and efficiently utilizing of electric energy is significant for energy-saving and emission-reduction and environmental conservation.2013, in global range, 22% in electric power was from regenerative resource, and along with the exhaustion of fossil energy, this numeral will increase year by year.But major part new forms of energy electric energy be required for boosting, inversion, grid-connected, then just can deliver to huge numbers of families.Therefore studying efficient DC-DC converter for the popularization of new forms of energy electric energy and efficiently utilizes impact great.

For present most photovoltaic battery panels, output voltage only has 20-50V, if it is grid-connected, then need the booster converter of higher gain, the basic topology such as the main Boost of conventional boost variator, flyback, Buck-Boost, cuk, sepic, zeta, current existing high-gain DC converter has coupling inductance high gain boost DC converter, Boost-flyback DC converter.But all there is structure complexity, analyze the drawbacks such as loaded down with trivial details, leakage inductance problem is serious in these converter topologies.

Summary of the invention

The purpose of this utility model is in that for problem of the prior art, it is proposed to a kind of simple in construction, efficiency are high, have the single tube Buck-Boost-flyback buck-boost type circuit topology of higher boosting gain.

Single tube Buck-Boost-flyback buck-boost type circuit of the present utility model, including: DC source, switch mosfet pipe, the transformator of turn ratio 1:n, the first diode, the second diode, the first electric capacity, the second electric capacity；The positive pole of DC source and transformer primary side Same Name of Ends, one end of the second electric capacity, load one end be connected, the drain electrode of the other end of transformer primary side and the positive pole of the second diode, switching tube is connected, the source electrode of switching tube connects the negative pole of DC source, transformer secondary Same Name of Ends and the negative pole of the second diode, the other end of the second electric capacity, the first electric capacity one end be connected, the other end of transformer secondary connects the positive pole of the first diode, and the other end of the negative pole of the first diode and the other end of the first electric capacity and load is connected.

Step-down/up type DC-DC circuit and the isolated flyback circuit of Buck-Boost are organically combined by buck-boost type circuit of the present utility model, realize the lifter change of DC voltage, wherein the transformator primary side of reverse excitation circuit is as the inductance of Buck-Boost, eliminate that efficiency that flyback converter leakage inductance causes is low and switch tube voltage stress crosses the problems such as height, improve the voltage gain under transducer effciency and boost mode.

Accompanying drawing explanation

Fig. 1 is circuit of reversed excitation topological diagram；

Fig. 2 is that in circuit of reversed excitation, transformator changes ideal transformer series connection leakage inductance circuit diagram into；

Fig. 3 is Buck-Boost circuit topology figure；

Fig. 4 is the circuit diagram after Buck-Boost is deformed；

Fig. 5 is Buck-Boost-flyback buck-boost type circuit topology figure of the present utility model；

Fig. 6 is that in Buck-Boost-flyback, transformator changes ideal transformer series connection leakage inductance circuit diagram into；

Fig. 7 is this utility model Buck-Boost-flyback circuit stage 1 path；

Fig. 8 is this utility model Buck-Boost-flyback circuit stage 2 path.

Detailed description of the invention

The main circuit topology of circuit of reversed excitation is as shown in Figure 1, by DC source DC, switching tube (low-voltage high-frequency can adopt MOSFET) Q1, transformator (turn ratio 1:n), diode D1, electric capacity C1, load R form, capacitance voltage is born just down, under continuous operation (CCM) pattern, input and output DC voltage steady state relation is:

$\frac{V_{out}}{V_{in}}=n\frac{D}{(1-D)}$

Wherein V_outRepresent the voltage on load resistance, V during steady operation under CCM pattern_inRepresenting the voltage of input DC power DC, D represents the dutycycle of switching tube gate-drive PWM.

Transformator in circuit of reversed excitation is changed into ideal transformer series connection leakage inductance model, circuit diagram is as shown in Figure 2, it is in parallel that real transformer model can be converted into the ideal transformer that magnetizing inductance Lm and one no-load voltage ratio is 1:n, then overall and leakage inductance Ld is composed in series, such equivalence can facilitate analysis circuit duty, is also very accurate equivalence.

Buck-Boost circuit topology figure is as shown in Figure 3, by DC source DC, switching tube (low pressure can adopt MOSFET) Q2, inductance L3, diode D2, electric capacity C2, load R form, just lower negative on capacitance voltage, then under CCM mode of operation, input and output DC voltage steady state relation is:

$\frac{V_{out}}{V_{in}}=-\frac{D}{(1-D)}$

Wherein V_outRepresent the voltage on load resistance, V during steady operation under CCM pattern_inRepresenting the voltage of input DC power DC, D represents the dutycycle of switching tube gate-drive PWM.

As shown in Figure 4, deformation principle is the position by the position and diode changing switching tube MOSFET in series arm to circuit diagram after Buck-Boost is deformed, and operation principle and the output-input voltage relation of circuit all remain unchanged.

Single tube Buck-Boost-flyback buck-boost type circuit of the present utility model, as shown in Figure 5.Circuit of reversed excitation and Buck-Boost circuit are organically combined, has shared an input DC power, a switching tube.Topology includes 1 DC source DC, 1 MOSFET carrying anti-paralleled diode, 1 transformator (no-load voltage ratio is 1:n), 2 diodes D1, D2,2 electric capacity C1, C2, also has load resistance R, constitutes main power circuit.By analysis it can be seen that the voltage of two electric capacity of load-side is just lower negative, so under boost mode, output voltage rises the voltage of a Buck-Boost than flyback Boost topology, adding amplification, leakage inductance energy is used by Buck-Boost topology simultaneously, improves circuit efficiency.

As shown in Figure 6, transformator in Buck-Boost-flyback is changed into ideal transformer series connection leakage inductance circuit diagram.

The analysis circuit current path when switch device conductive: be defined as the stage 1 when being turned on by Q1.As it is shown in fig. 7, when Q1 turns on, primary voltage of transformer is upper just lower negative, secondary be upper negative under just, the then reverse-biased cut-off of D1.And D2 reversed bias voltage is C2 voltage plus supply voltage, then D2 is also switched off.For mains side, DC source DC magnetizes to transformator equivalence magnetizing inductance Lm, and the electric current of inductance Lm rises, and the electric current of leakage inductance Ld is also rising simultaneously.For load-side, because two diodes are turned off, so only electric capacity provides electric current to load resistance R, electric capacity discharges, and voltage declines.This stage is equivalent to the combination that transformator magnetizing inductance when the switching tube of circuit of reversed excitation is opened magnetizes and inductance magnetizes when Buck-Boost contactor pipe opens.

The analysis circuit current path when switching device turns off: be defined as the stage 2 when being turned off by Q1.As shown in Figure 8, when Q1 turns off, transformer primary side magnetizing inductance and leakage inductance electric current are no longer flow through switching tube and return to power supply DC negative pole, but find other loop afterflow.When Q1 just turns off; leakage inductance electric current will turn on afterflow by diode D2; charge to electric capacity C2; this process is equivalent to Buck-Boost circuit freewheeling period under discontinuous operating mode, well achieves the energy of leakage inductance and transfers to load-side and be utilized, rather than causes that Q1 voltage stress rises through MOSFET parasitic capacitance; so reducing switch tube voltage stress; this allows to the MOSFET selecting conducting resistance less, thus improve efficiency, protects switching tube.Leakage inductance Ld and the former limit L1 of ideal transformer carries out the change of current simultaneously, and after waiting the change of current to terminate, when namely leakage inductance electric current drops to 0, the L1 electric current electric current equal to Lm, secondary time-dependent current is following inflow, flows out above, then diode D1 conducting, charges to C1.The voltage of C1 charging and the voltage of C2 are just lower negative, and then the voltage of load resistance is the superposition of two voltages.So that voltage amplification factor rises when circuit is operated under boost mode.The combination of inductance afterflow when transformator magnetizing inductance exoergic and Buck-Boost contactor pipe turn off when this stage is equivalent to the switching tube shutoff of circuit of reversed excitation.

Generally speaking, buck-boost buck-boost type circuit and flyback isolated DC translation circuit are organically combined by buck-boost-flyback, eliminate the problem that leakage inductance is brought, reduce the voltage stress of switching tube, add amplification during voltage amplification so that DC-DC converter circuit performance is better.Comparing with single buck-boost buck-boost type circuit, step-up ratio is about improve n+1 times by buck-boost-flyback circuit；Compare with flyback circuit so that leakage inductance problem is well eliminated, reduce the stress of switching tube, improve the efficiency of circuit simultaneously.For the production technology of transformator, then have only to pay close attention to efficiency and step-up ratio (turn ratio relation), the problem no longer brought by worry leakage inductance.

Claims (1)

1. a single tube Buck-Boost-flyback buck-boost type circuit, it is characterised in that including: DC source, switch mosfet pipe, the transformator of turn ratio 1:n, the first diode, the second diode, the first electric capacity, the second electric capacity；The positive pole of DC source and transformer primary side Same Name of Ends, one end of the second electric capacity, load one end be connected, the drain electrode of the other end of transformer primary side and the positive pole of the second diode, switching tube is connected, the source electrode of switching tube connects the negative pole of DC source, transformer secondary Same Name of Ends and the negative pole of the second diode, the other end of the second electric capacity, the first electric capacity one end be connected, the other end of transformer secondary connects the positive pole of the first diode, and the other end of the negative pole of the first diode and the other end of the first electric capacity and load is connected.