CN1595781A - A circuit for realizing switch changeover with zero-voltage switch power - Google Patents

Abstract

The invention advances a new method of realizing the zero-voltage-switching (ZVS) transition of a switch by unidirectional charge and discharge of an absorption capacitance and its control method. An absorption capacitance as well as other components composes a double end network, making the absorption capacitance work in a unidirectional charge-discharge state, i.e. the absorption capacitance makes charge and discharge at a top-positive and bottom-negative unidirectional voltage, and thus providing a condition for a switch tube to realize ZVS transition. The double end network cooperates with some components to largely reduce the variation rates of voltage waveform of a drain of the switch tube and current waveform of a transformer, radically reducing EMI, and also providing a full condition for the secondary side to adopt a simple circuit so as to realize synchronous rectification. It can by a large margin increase SPS converting efficiency and reduces the EMI, and can reduce the cost of SPS and realize a small-sized high-frequency SPS.

Description

A kind of circuit of realizing the conversion of Switching Power Supply zero voltage switch

(1) technical field:

The present invention relates to a kind of circuit of Switching Power Supply zero voltage switch conversion of realizing and newly design, employing absorption electric capacity is unidirectional to discharge and recharge and the control circuit realization.

(2) background technology:

Switching Power Supply (SPS) is being represented the developing direction of DC power supply, has been widely applied to the productive life various aspects, at present to high frequencyization, high efficiency, miniaturization and the development of better electromagnetic compatibility (EMC) effect.For reaching above-mentioned requirements, adopting zero voltage switch (ZVS), Zero Current Switch (ZCS) is that so-called resonant type soft-switch technology and field effect transistor replace the synchronous rectification of diode to become effective means.But existing soft switch technique and synchronous rectification circuit structure complexity, design, making and debugging difficulty are big, and generally will cost be improved with special IC control, so only be used in high-power SPS aspect.Accompanying drawing 1 is the Switching Power Supply frame principle figure, and accompanying drawing 2 is switching tube Q when providing the RCC inverse-excitation type switch power-supply circuit schematic diagram of a present practicality and steady operation ₁Drain voltage and transformer TR primary and secondary current i ₁, i ₂Waveform.Q among Fig. 2 ₁In the conducting of a point, direct voltage Vh is added in elementary winding n ₁On, set up magnetic field energy in the TR magnetic circuit, controlled circuit adjustment effect, Q ₁Turn-off at the b point; Vd reaches the c point by jumping with big slope near 0V.Vd forms a leakage inductance spike at the c point, and (Vr is n to carry out the transition to steady-state value Vh+Vr after several all damped oscillations ₂In rectification when output, is at n ₂The reflected voltage of last induction).Finish TR winding n from secondary release in d point magnetic field energy ₁, n ₂, n ₃Going up end of the same name is that positive induced voltage descends rapidly.n ₃And R ₄, C ₄Effect make Q ₁Change conducting state at the e point, begin next week vibration.Bc section rate of rise R ₁And de section descending slope, R ₂Can regulate by changing component parameters.But the too little meeting of slope significantly increases Q ₁Switching loss can produce very strong electromagnetic interference (EMI) again too greatly.So R ₁, R ₂A midrange is arranged, cause Q ₁Produce certain turn-off power loss at the b point.In the de section because drain voltage is not 0 to make Q ₁Produce certain turn-on consumption during conducting.D ₁, R ₃, C ₃The leakage inductance of forming absorbs network also can consume most of leakage inductance energy and a part of mutual inductance energy.Q ₁Fast-changing Vd and i when opening and turn-offing ₁, i ₂Waveform is the immediate cause that produces EMI, has increased the cost of SPS aspect EMC, has limited the scope of application of SPS; Simultaneously also increased the complexity of secondary employing circuit of synchronous rectification and reduced reliability, made synchronous rectification become unrealistic.These shortcomings have hindered SPS and have further improved operating frequency and efficient, reduce volume, reduce EMI.

(3) summary of the invention:

The designed circuit that goes out of the present invention just can reliably be realized the ZVS conversion and the SPS operating state of SPS switching tube with several discrete components, be that switching tube and transformer primary and secondary voltage, electric current are improved at all, can significantly improve efficient, reduce electromagnetic interference (EMI), and for using simple and reliable circuit of synchronous rectification to create condition.

The designed switching power circuit of the present invention as shown in Figure 3, it includes rectification circuit, switching tube, isolating transformer, rectifying and wave-filtering, the electric current and voltage sampling is relatively amplified, the protection control Driver Circuit is relatively amplified in photoelectricity coupling, error signal.Newly-designed leakage inductance absorbs lattice network for absorbing capacitor C ₁Negative terminal and Q ₂Source electrode and D ₂(can be Q ₂Body diode) anode links to each other, C ₁Anode (both network A ends) links to each other Q with primary winding one end ₂Drain electrode and negative electrode (both network B ends) link to each other C with the elementary winding other end ₂With R ₁Terminal network A end in parallel, another termination D ₃Anode and D ₅Negative electrode, D ₃Negative electrode meets Q ₂Gate pole, D ₅Anode meets Q ₂Source electrode, voltage-stabiliser tube Z ₁With C ₃(can be Q ₂Gate pole is to the source drain distributed capacitance) parallel connection, its negative electrode meets Q ₂Gate pole, anode meets Q ₂Source electrode; D ₄Anode meets Q ₂Gate pole, negative electrode connect the network A end.Absorption electric capacity proposed by the invention is unidirectional to discharge and recharge network and also can be applicable to DC-DC and do not realize switching tube ZVT conversion in the isolation boosting converter; Boost inductance is equivalent to the primary winding, and operation principle is similar.

After the leakage inductance of Switching Power Supply absorbed lattice network and done such design, because C ₁And C ₂Can select larger capacity for use, the first electrode current waveform of Vd waveform and TR rate of change when switch transition reduces greatly, and EMI is improved at all; Reduced the requirement that the inferior utmost point adopts circuit of synchronous rectification simultaneously, it is simple and reliable that synchronous rectification becomes.In sum, the present invention significantly raises the efficiency the reduction electromagnetic interference for Switching Power Supply, thereby realizes that high frequencyization, miniaturization and electromagnetic compatibility optimization provide a kind of new method.

(4) description of drawings:

Accompanying drawing 1 is the Switching Power Supply frame principle figure.

Switching tube Q when accompanying drawing 2 is present RCC inverse-excitation type switch power-supply schematic diagram and steady operation ₁With transformer TR primary and secondary and current i ₁, i ₂Waveform.

Accompanying drawing 3 is designed circuit theory diagrams and the switching tube Q of the present invention ₂The capable figure of drain voltage Vd point ripple during steady operation.

(5) embodiment:

The designed switching power circuit of the present invention as shown in Figure 3; it includes rectification circuit, switching tube, isolating transformer, rectifying and wave-filtering; the electric current and voltage sampling is relatively amplified, photoelectricity is coupled, error signal is relatively amplified the protection control Driver Circuit, has newly designed leakage inductance and has absorbed lattice network.D among Fig. 3 ₁, D ₂Be respectively Q ₁, Q ₂The body fast recovery diode, can be external when there is not body diode in switching tube diode replace.C ₃Be nonessential element, C when this electric capacity of peripheral hardware not ₃Represent Q ₂Gate pole is to the source drain distributed capacitance, this moment C ₂Parameter is wanted corresponding adjustment.Same C ₄Be nonessential element, C when time electric capacity of peripheral hardware not ₄Represent Q ₁Drain electrode is to source electrode gate pole distributed capacitance.From g point beginning Q ₁Conducting.TR sets up behind the certain magnetic field energy at a point Q ₁Turn-off at once, because C ₄The nature that exists can implement Q ₁Extremely fast ZVS turn-off Q ₁Turn-off power loss is very little, C ₄Vd is opened on less slope in the ab section, reduced ENI greatly.Vd reaches Vh on the b point, absorb electric C ₁Also begin from about OV charging, the bc slope over 10 is littler.n ₁The existence of leakage inductance makes the small size mistake of Vd be charged to the C point and carries out the transition to steady-state value Vh+Vr through damped oscillation, and Vr is n ₂In rectification when output, is at n ₁The reflected voltage of induction.The b point in the c point process, C ₁Last voltage is applied to C simultaneously ₂, D ₃, C ₃On the series arm, C ₃To be charged to appropriate voltage and make Q ₂Be in conducting state, C when Vr=110V ₃The about 10V of voltage.Z ₁Play amplitude limit effect protection Q ₂R ₁Go up little electric current through D ₃Replenish Z ₁Electric leakage makes C ₃Voltage is stable.Vd during to the d point magnetic field energy from n ₂Release finishes, C ₁Beginning is through Q ₂, n ₁Discharge, C4 is also thereupon through n ₁, Vh discharge.To e point C ₁Voltage drops to 0, and electric field energy is converted into TR magnetic field.At C ₁Voltage drops to C ₃During voltage, C ₃Through D ₄Be discharged to about 0V and with Q ₂Turn-off C ₂Then pass through D ₅Discharge.As seen at e point Vd=Vh, Q ₂Turn-off; Thereby make C ₁Realize unidirectional discharging and recharging, and discharge and recharge under the unidirectional voltage condition that can only on just descending, bear that this is Q ₁Realize the key of ZVS conducting, at e point Vd=Vh, n ₁Electric current makes progress, corresponding magnetic field energy $\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">C</figure-callout>}}_1{\mathrm{<figure-callout\; id="2"\; label="Vr"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">Vr</figure-callout>}}^2+\frac{1}{2}{C}_4{(\mathrm{Vh}+\mathrm{Vr})}^2-\frac{1}{2}{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">C</figure-callout>}}_4{\mathrm{Vh}}^2-{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\mathrm{Vr}$ Vh; After this n ₁In exciting current with magnetic field energy and C ₄In electric field energy transform and to feed back among the DC high-voltage power supply Vh, Vd also descends thereupon.When f point Vd dropped to 0V, the energy that Vh obtains was C from the e point ₄Vh ², and C ₄The energy that discharges is So as long as the appropriate design circuit parameter makes energy $\frac{1}{2}{\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">C</figure-callout>}}_1{\mathrm{<figure-callout\; id="2"\; label="Vr"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">Vr</figure-callout>}}^2+\frac{1}{2}{C}_4{(\mathrm{Vh}+\mathrm{Vr})}^2-\frac{1}{2}{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">C</figure-callout>}}_4{\mathrm{Vh}}^2-{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">C</figure-callout>}}_4\mathrm{VrVh}>{\mathrm{<figure-callout\; id="4"\; label="C"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">C</figure-callout>}}_4{\mathrm{<figure-callout\; id="2"\; label="Vh"\; filenames="A20041001038600081.png"\; state="\{\{state\}\}">Vh</figure-callout>}}^2$ , both satisfied C ₁Vr ²＞C ₄Vh ²-C ₄Vr ²Just can make Vd drop to n behind the 0V ₁In still have electric current upwards to exist, D then ₁To play the afterflow effect, Vd drops to pact-0.7V.Just can implement Q at the g point like this ₁ZVS and ZCS open-minded, turn-on consumption is 0.Control circuit CTL is one 5 end network among Fig. 3, and its effect is described below: 1 end ground connection; 2 ends are voltage stabilizing feedback and first limit current control end, and its current potential is used to transfer Q by primary current and the decision of optocoupler electric current ₁ON time realizes output voltage stabilizing and current limliting; 3 is the control output end; Conducting is arranged over the ground, end two states, be used for driving Q ₁Switch transition; 4 is Vd current potential test side; 5 termination accessory power supply C ₅Anodal.When 5 terminal potentials were 0V, 3 were cut-off state over the ground, like this Q when connecting the interchange input ₁Can pass through R ₃Start vibration; (power initiation vibration back C when 5 ends are not 0V ₅Set up voltage), then in case 3 over the ground conducting with Q ₁Having no progeny in the pass, has only 4 ends to detect just to make when Vd is negative potential 3 to transfer to over the ground and end Q ₁Can realize that ZVS is open-minded.The control circuit function only just can make with several discrete components.N after the f point among Fig. 3 ₁In the electric current that makes progress drop to 0 and begin to increase to set up magnetic field very soon downwards, establish next cycling of beginning by cable.The model of components and parts and data mark in circuit in the circuit, no longer explanation.

Claims (3)

1, a kind of circuit of Switching Power Supply zero voltage switch conversion; employing absorption electric capacity is unidirectional to discharge and recharge and the control method realization; it includes that rectification circuit, switching tube, isolating transformer, rectifying and wave-filtering, electric current and voltage sampling are relatively amplified, the protection control Driver Circuit is relatively amplified in photoelectricity coupling, error signal, and it is characterized in that: the leakage inductance of design absorbs lattice network for absorbing capacitor C ₁Negative terminal and Q ₂Source electrode and D ₂Anode links to each other, C ₁Anode both network A end links to each other Q with primary winding one end ₂Drain electrode and negative electrode, both the network B end linked to each other C with the elementary winding other end ₂With R ₁Terminal network A end in parallel, another termination D ₃Anode and D ₅Negative electrode, D ₃Negative electrode meets Q ₂Gate pole, D ₅Anode meets Q ₂Source electrode, voltage-stabiliser tube Z ₁With C ₃Parallel connection, its negative electrode meets Q ₂Gate pole, anode meets Q ₂Source electrode; D ₄Anode meets Q ₂Gate pole, negative electrode connect the network A end.

2, the circuit of a kind of Switching Power Supply zero voltage switch conversion according to claim 1 is characterized in that: D ₂Can be Q ₂Body diode, C ₃Can be Q ₂Gate pole is to the source drain distributed capacitance.

3, the circuit of a kind of Switching Power Supply zero voltage switch conversion according to claim 1, it is characterized in that: absorption electric capacity proposed by the invention is unidirectional to discharge and recharge network and also can be applicable to DC-DC and do not realize switching tube ZVT conversion in the isolation boosting converter, and boost inductance is equivalent to the primary winding.

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