CN201118451Y - No loss absorption circuit for reverse activation switch power - Google Patents

Abstract

The utility model discloses a lossless snubber circuit for a flyback switching power supply, comprising a switch tube whose upper end pins are connected with a primary coil of a transformer in series, a control chip which is connected to the control pin of the switch tube to control the work of the switch tube, a lossless snubber loop composed of a first inductor, a first diode, a first capacitor and a second diode, as well as a power supply loop which is composed of the first inductor, a third diode and a second capacitor and used for absorbing the energy generated by the lossless snubber loop and supplying auxiliary electric power to the control chip. The positive and negative ends of the third diode of the power supply loop are respectively connected to the node between the first inductor and the first diode of the lossless snubber loop and the power supply input terminal VDD of the control chip; the two ends of the second capacitor are respectively connected to the power supply input terminal VDD of the control chip and the negative end of a DC power supply VDC. The circuit makes full use of the energy in the lossless snubber circuit, saves auxiliary power supply and eliminates the limiting conditions in the application of the lossless snubber circuit.

Description

The lossless absorption circuit that is used for inverse-excitation type switch power-supply

Technical field

It is the circuit of one that the utility model relates to a kind of harmless absorption of collection and accessory power supply that is used for inverse-excitation type switch power-supply.

Background technology

Basic flyback power supply circuit (see figure 1), in inverse-excitation type switch power-supply, because existence and other effects of distribution parameters of transformer leakage inductance, the shutdown moment of switching tube Q1 can produce very big peak voltage Vclamp in power work, sees the voltage waveform that drains in Fig. 2 switching tube Q1 turn off process.The operate as normal of switching tube Q1 in this peak voltage Vclamp serious threat, influences the stable and safety of whole system, and produces the EMI problem, must take measures it is carried out Pliers position or absorption.At present, there are a variety of methods to achieve this end, RCD absorption plant wherein is simple in structure with it, characteristics with low cost and be able to extensive use, absorb basic circuit as Fig. 3 for RCD, dash area is the RCD absorption portion among the figure, and Lpri1 is the primary inductance, and Llr is a transformer leakage inductance.This device course of work is as follows: when controller control switch pipe M1 conducting, the electric current among transformer Lpri1, the transformer leakage inductance Llr increases gradually, and energy is stored among primary inductance L pri1 and the transformer leakage inductance Llr; When switching tube M1 closes, the energy among the Lpri1 will be transferred to secondary output, but the energy among the transformer leakage inductance Llr can not be delivered to secondary, if do not have the RCD absorption plant, the energy among the transformer leakage inductance Llr

(L refers to leakage inductance, and I refers to the maximum current that flows through before switching tube turn-offs) will leak in the stray capacitance of level at drain-source interelectrode capacitance and the switching tube M1 that switching tube M1 shutdown moment is transferred to switching tube M1, and this energy is distributed electric capacity and absorbs, according to the energy rule in the electric capacity

Because the capacity of these distributed capacitance is very little,, thereby make the drain electrode of switching tube M1 produce very high peak voltage, i.e. Vclamp among Fig. 2 so distributed capacitance can produce very high voltage.And the voltage stress that switching tube M1 bears is Vc+Vor+Vin, and wherein Vc is the peak voltage that produces on the electric capacity, $\mathrm{Vor}=\frac{\mathrm{Np}}{\mathrm{Ns}}\mathrm{Vout},$ Np: number of primary turns, Ns: the secondary coil number of turn, Vout: output voltage.If after adding the RCD absorption plant, capacitor C 2 capacity wherein are much larger than distributed capacitance, most of energy among the transformer leakage inductance Llr will be transferred on the Pliers position capacitor C 2 of Pliers position circuit at switching tube M1 shutdown moment, formula according to capacitance energy storage, under the situation of constant in energy, square U of capacitor C and voltage ²Be inversely proportional to, so the peak voltage that electric capacity capacious produces is lower, this part energy is consumed by Pliers position resistance R 0 then, prepares for absorbing next time, has just significantly reduced the voltage stress of switching tube M1 like this in switching tube M1 turn off process.

As mentioned above, the RCD absorption plant is alleviated the high pressure stress of switching tube M1, by transformer leakage inductance Llr energy consumption is finished on Pliers position resistance R 0, this has caused the waste of this part energy, will obtain assimilation effect preferably when absorbing leakage inductance energy, promptly allow the spike of peak voltage Vclamp less, it is enough big that the value that makes Pliers position capacitor C 2 is so just wanted, and will have been consumed the energy of each absorption by Pliers position resistance R 0, because the energy of Pliers position capacitor C 2 is $\mathrm{Wc}=\frac{1}{2}\mathrm{CU}2=\frac{1}{2}C2*\mathrm{Vclamp}2,$ So it is just bigger than normal to obtain the value of good more effect capacitor C 2, loss is many more like this.In order to reduce power loss, can also use lossless absorption circuit as shown in Figure 4.

Lossless absorption circuit as shown in Figure 4 also is by the energy absorption of transformer leakage inductance when switching tube M2 turn-offed, and feed back in input or the output, this device course of work is as follows: when controller control switch pipe M2 turn-offs, the drain voltage of switching tube M2 rises rapidly, capacitor C 3 begins charging, absorb the energy in the leakage inductance, slow down the dV/dT of switching tube M2 drain electrode.Till the energy of capacitor C 3 chargings leakage inductance until have no progeny in switching tube M2 pass has been absorbed, this moment, capacitor C 3 both end voltage A points were for just, the B point is for negative, the magnitude of voltage at capacitor C 3 two ends, stable back is VOR, after controller control switch pipe M2 opens once more, the current potential that the right-hand member pin A of capacitor C 3 is ordered drops to 0, because capacitor C 3 left ends are than the voltage height of right-hand member, its voltage difference is VOR, when so switching tube M2 has just opened, the voltage of capacitor C 3 left end pins drops to-VOR, cause the D4 conducting, capacitor C 3 forms resonance by diode D4 and inductance L 1 so, energy shifts between inductance L 1 and capacitor C 3, energy is transferred to inductance L 1 by capacitor C 3 discharges earlier, because the sustainability of inductance L 1 electric current, release energy by inductance L 1 again after capacitor C 3 discharges are finished C3 is charged, energy in inductance L 1 is transferred to capacitor C 3 once more, half period through resonant process, voltage on the capacitor C 3 is converted into 0 and is converted into-VOR again by+VOR, as Fig. 6,7 are depicted as the capacitor C 3 of lossless absorption circuit LC resonance half period when the switching tube conducting, voltage change process on the inductance L 1, that is to say in switching tube conducting inductance L 1, behind capacitor C 3 half harmonic period, the voltage of capacitor C 3 has changed direction, prepare for absorbing leakage inductance energy next time, the voltage condition at its two ends was that A is negative after this moment, capacitor C 3 charging was finished, and B is for just.Because the unidirectional conduction of diode, diode D4 ends, and energy is kept in the capacitor C 3.When switching tube M2 turn-offs once more, when B point voltage during greater than input voltage, diode D5 conducting, capacitor C 3 discharges, energy wherein feeds back in the transformer coil, once more to its charging, absorbs the energy in the transformer leakage inductance after the release of the energy in the capacitor C 3 finishes, along with the control action of controller, lossless absorption circuit repeats such cycle.In absorbing circuit, mostly be non-energy dissipation device, do not produce loss,, produce a spot of energy loss on switching tube M2 and the some other parasitic antenna only at diode D4.Because not produce power loss of lossless absorption circuit so can come the buffer switch process with bigger absorption capacitor C 3, reduces EMI and disturbs, favourable system stablizes, and has reduced energy loss to greatest extent.

Lossless absorption circuit has many good qualities but also can't popularize use at present, be because its use needs restrictive condition, in the analytic process in front, the voltage of capacitor C 3 is opened back from the negative time course of the negative needs of the positive A of B that forwards to of the positive B of A at switching tube M2, be half of the harmonic period of capacitor C 3 and inductance L 1, the ON time that requires switching tube is greater than this time, if switching tube can not meet this requirement, switching tube M2 closes before finishing in Conversion of energy between capacitor C 3 and the inductance L 1, capacitor C 3 so, the resonant tank of inductance L 1 is closed, the energy of inductance L 1 also is not transferred to capacitor C 3 fully so, cause in the inductance L 1 energy accumulation is arranged, because the electric current on the inductance L 1 can not be zero moment, cause inductance L 1 energy to discharge nowhere, very big surge voltage be can form on the inductance L 1, thereby device breakdown or breaking-up such as pair of switch M2 made easily.Because inverse excitation type converter opening and turn-offing by control chip or control circuit control switch pipe M2, when changing, secondary load makes that switching tube M2 ON time demand is inconsistent, the inverse-excitation type switch power-supply that most of control chip is formed can not all guarantee this condition in the different operating process, so can't use this lossless absorption circuit.On the other hand, in inverse-excitation type switch power-supply, needing usually increases the powerup issue that ancillary coil solves control chip in transformer, and as shown in Figure 7, ancillary coil Las and primary coil Lpri4 homophase come to power to control circuit as accessory power supply.Ancillary coil Las can with primary coil Lpri4 homophase, also can be anti-phase with it.Switching tube M3 switch once, then ancillary coil is given capacitor C 4 power supplies once, makeup energy repeatedly is to guarantee that the control module working power is in normal operation interval.

Summary of the invention

The purpose of this utility model is in order to overcome the deficiencies in the prior art, a kind of lossless absorption circuit that is used for inverse-excitation type switch power-supply is provided, it can be in the harmless absorption plant advantage of performance, make full use of the energy in the lossless absorption circuit, saved accessory power supply, simplify circuit, reduced loss.

Realize that the above-mentioned purpose technical scheme is: a kind of lossless absorption circuit that is used for inverse-excitation type switch power-supply, comprise the switching tube M2 that a upper end pin is connected with transformer, one is connected the control chip and that is used for control switch pipe M2 work of switching tube M2 control pin by the first inductance L OA, the first diode D0, first capacitor C 0 and the second diode D1 constitute is used to absorb the harmless absorption circuit of the peak voltage that switching tube M2 produces at shutdown moment, should can't harm the second diode D1 in the absorption circuit, be connected on the positive and negative polarities end of DC power supply VDC after the first diode D0 and the first inductance L OA are connected in series successively with after transformer that is connected in series and switching tube M2 are in parallel, the two ends of described first capacitor C 0 are connected on the node between node between the first diode D0 and the second diode D1 and transformer and the switching tube upper end pin, also comprise one by the first inductance L OA, the 3rd diode D2 and second capacitor C 1 constitute is used to absorb energy that harmless absorption circuit produces and the current supply circuit that accessory power supply is provided to control chip, the 3rd diode D2 of this current supply circuit positive and negative extremely is connected on the power input VDD of the node between the first inductance L OA and the first diode D0 and control chip in the harmless absorption circuit, the two ends of described second capacitor C 1 are connected on the power input VDD and place of working end of control chip, and this place of working end is the negative pole end of DC power supply VDC.

The above-mentioned lossless absorption circuit that is used for inverse-excitation type switch power-supply, wherein, described harmless absorption circuit comprises that also a series connection is connected the second inductance L OB between the first inductance L OA and the first diode D0.

The above-mentioned lossless absorption circuit that is used for inverse-excitation type switch power-supply, wherein, described current supply circuit comprises that also one is connected the current-limiting resistance R1 between the power input VDD of the negative pole end of the 3rd diode D2 and control chip.

The above-mentioned lossless absorption circuit that is used for inverse-excitation type switch power-supply, wherein, described current supply circuit comprises that also a parallel connection is connected the voltage stabilizing didoe D3 at second capacitor C, 1 two ends.

Owing to adopted the technical scheme that is used for the lossless absorption circuit of inverse-excitation type switch power-supply of the present utility model, be that the utility model improves on the basis of the lossless absorption circuit of prior art, on the basis of original lossless absorption circuit, increase the energy absorption device, energy on the absorption inductor, utilization energy wherein is as accessory power supply, lossless absorption circuit is used as the control chip power supply, the problem and the harm that may occur in the harmless absorption use had both been eliminated, can under the situation that realizes harmless all advantages of absorption, realize accessory power supply and eliminate the restrictive condition that harmless absorption is used again, lossless absorption circuit is widely used.In the advantage that obtains all energy-conservation and low EMI interference of lossless absorption circuit, solved the accessory power supply function.Expand the function of lossless absorption circuit, in the harmless absorption advantage of performance, made full use of the energy in the lossless absorption circuit, saved accessory power supply, simplified circuit, reduced loss.

Description of drawings

Fig. 1 is basic flyback power supply circuit theory diagrams;

Fig. 2 is the change curve of drain voltage in the switching tube turn off process in the basic flyback power supply circuit;

Fig. 3 is the circuit theory diagrams of the RCD absorption plant of prior art;

Fig. 4 is the circuit theory diagrams of the harmless absorption plant of prior art;

Fig. 5,6 is respectively harmless absorption plant inductance L and the capacitor C 3 of capacitor C resonance half period, the change in voltage curve chart on the inductance L 1 when the switching tube conducting;

Fig. 7 is the circuit theory diagrams of prior art to control chip power supply in the flyback power supply circuit;

Fig. 8 is the schematic diagram of first kind of embodiment of the lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model;

Fig. 9 is the lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model inductance L and first capacitor C 0 of capacitor C resonance half period, the change in voltage curve chart on the first inductance L 0A when the switching tube conducting;

Figure 10 is the schematic diagram of second kind of embodiment of the lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model;

Figure 11 is the schematic diagram of the third embodiment of the lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model;

Figure 12 is the schematic diagram of the 4th kind of embodiment of the lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model.

Embodiment

In order to understand the technical solution of the utility model better, below by embodiment particularly and be described in detail in conjunction with the accompanying drawings:

See also Fig. 8, first kind of lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model, comprise the switching tube M2 that a upper end pin is connected with transformer Lpri1, one is connected the control chip that is used for control switch pipe M2 work of switching tube M2 control pin, an one harmless absorption circuit and a current supply circuit, wherein, M2 can be a metal-oxide-semiconductor, also can use triode, or other switching device, harmless absorption circuit is by the first inductance L OA, the first diode D0, first capacitor C 0 and the second diode D1 constitute, be used to absorb the peak voltage that switching tube M2 produces at shutdown moment, should can't harm the second diode D1 in the absorption circuit, the first diode D0 and the first inductance L OA be connected in series successively the back be connected on the positive and negative polarities end of DC power supply VDC after transformer Lpri1 that is connected in series and switching tube M2 are in parallel, and the two ends of first capacitor C 0 in the harmless absorption circuit are connected on node between the first diode D0 and the second diode D1 and transformer Lpri1 and the switching tube M2 on the node between the pin.Current supply circuit is made of the first inductance L OA, the 3rd diode D2 and second capacitor C 1, be used to absorb the energy of harmless absorption circuit generation and provide accessory power supply to control chip, the 3rd diode D2 of this current supply circuit positive and negative extremely is connected on the power input VDD of the node between the first inductance L OA and the first diode D0 and control chip in the harmless absorption circuit, the two ends of second capacitor C 1 of current supply circuit are connected on the power input VDD and place of working end of control chip, and this place of working end is the negative pole end of DC power supply VDC.

Second kind of lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model sees also Figure 10, and harmless absorption circuit comprises that also a series connection is connected the second inductance L OB between the first inductance L OA and the first diode D0.Its effect is to regulate the size that energy is provided to second capacitor C 1 by the relative size of regulating the lossless absorption circuit first inductance L 0A and the second inductance L 0B.

Of the present utility model the third is used for the lossless absorption circuit of inverse-excitation type switch power-supply, see also Figure 11, current supply circuit comprises that also one is connected the current-limiting resistance R1 of the adjustable resistance size between the power input VDD of the negative pole end of the 3rd diode D2 and control chip, and its effect also is to regulate the energy size of supplying with second capacitor C 1 by the size of regulating this current-limiting resistance R1.

The 4th kind of lossless absorption circuit that is used for inverse-excitation type switch power-supply of the present utility model sees also Figure 12 current supply circuit and comprises that also a parallel connection is connected the voltage stabilizing didoe Z1 at second capacitor C, 1 two ends, and its effect is to stablize control chip power supply energize.

The operation principle of the above-mentioned lossless absorption circuit that is used for inverse-excitation type switch power-supply is: inner or outside at control chip, second capacitor C 1 and voltage stabilizing didoe Z1 parallel connection are used for restraint of labour voltage.During switching tube M2 opens, the first inductance L 0A will form resonance with first capacitor C 0, energy is in the first inductance L 0A and 0 transfer of first capacitor C, its change in voltage as shown in Figure 9, the terminal voltage of the first inductance L 0A initially is a sinusoidal voltage, when the first inductance L 0A terminal voltage be sinusoidal waveform rise to be enough to make the 3rd diode D2 conducting after, the first inductance L 0A will provide energy to second capacitor C 1, just as ancillary coil provides energy, because the 1 energy storage effect of second capacitor C, the voltage of the first inductance L 0A will be by the Pliers position at Vc1.The every switch of switching tube M2 once, the first inductance L 0A provides primary energy to second capacitor C 1, like this with regard to having avoided energy in the lossless absorption circuit in the first inductance L 0A, to accumulate breakdown switch pipe M2 may, absorb when alleviating switching tube M2 and turn-offing in the drain voltage stress harmless, saved accessory power supply, simplify circuit, saved the energy.

Those of ordinary skill in the art will be appreciated that, above embodiment is used for illustrating the utility model, and be not to be used as qualification of the present utility model, as long as in connotation scope of the present utility model, all will drop in claims scope of the present utility model variation, the modification of the above embodiment.

Claims (4)

1. lossless absorption circuit that is used for inverse-excitation type switch power-supply, comprise the switching tube M2 that a upper end pin is connected with transformer, one is connected the control chip and that is used for control switch pipe M2 work of switching tube M2 control pin by the first inductance L OA, the first diode D0, first capacitor C 0 and the second diode D1 constitute is used to absorb the harmless absorption circuit of the peak voltage that switching tube M2 produces at shutdown moment, should can't harm the second diode D1 in the absorption circuit, be connected on the positive and negative polarities end of DC power supply VDC after the first diode D0 and the first inductance L OA are connected in series successively with after transformer that is connected in series and switching tube M2 are in parallel, the two ends of described first capacitor C 0 are connected on the node between node between the first diode D0 and the second diode D1 and transformer and the switching tube M2 upper end pin, it is characterized in that, also comprise one by the first inductance L OA, the 3rd diode D2 and second capacitor C 1 constitute is used to absorb energy that harmless absorption circuit produces and the current supply circuit that accessory power supply is provided to control chip, the 3rd diode D2 of this current supply circuit positive and negative extremely is connected on the power input VDD of the node between the first inductance L OA and the first diode D0 and control chip in the harmless absorption circuit, the two ends of described second capacitor C 1 are connected on the power input VDD and place of working end of control chip, and this place of working end is the negative pole end of DC power supply VDC.

2. the lossless absorption circuit that is used for inverse-excitation type switch power-supply according to claim 1 is characterized in that, described harmless absorption circuit comprises that also a series connection is connected the second inductance L OB between the first inductance L OA and the first diode D0.

3. the lossless absorption circuit that is used for inverse-excitation type switch power-supply according to claim 1 is characterized in that, described current supply circuit comprises that also one is connected the current-limiting resistance R1 between the power input VDD of the negative pole end of the 3rd diode D2 and control chip.

4. the lossless absorption circuit that is used for inverse-excitation type switch power-supply according to claim 1 is characterized in that, described current supply circuit comprises that also a parallel connection is connected the voltage stabilizing didoe Z1 at second capacitor C, 1 two ends.

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