EA038303B1 - Method and device to recuperate the dissipated power of inverse converter transformer - Google Patents

Abstract

The invention relates to electric engineering, in particular, to power pulse converters and concerns a method and device to limit voltage without losses at a transistor pulse switch loaded with a parasitic inductance. A device is proposed to recuperate the dissipated power of flyback converter transformer, including a series connected power source, load and pulse switch; the first electric circuit including auxiliary condenser; the first diode series connected to the first circuit containing a throttle, and the second circuit connected to the electrode of the first diode connection to the first circuit; the serial first diode and first circuit are connected in parallel to the load connection electrode in such a way that the first circuit is connected to the load connection electrode to the pulse switch, and the second circuit and the first diode are connected in parallel to the power source so that the first diode is oriented to the side of the positive electrode of the power source; the first circuit includes an additional auxiliary switch connected serially to the auxiliary control condenser to prevent discharge of the mentioned auxiliary capacity below a preset value. A method is proposed to recuperate the dissipated power of flyback converter transformer using the declared device where an auxiliary switch opens the first circuit in a cycle of an open pulse switch to prevent discharge of the auxiliary condenser below a preset voltage. The technical result is an ability of the declared device to function in a continuous current mode thus increasing the effectiveness of recuperation of dissipated magnetic field energy of a high frequency transformer.

Description

The invention relates to electrical engineering, in particular to power pulse converting equipment, and relates to a method and device for limiting voltage without losses on a transistor pulse switch loaded on an inductive load or a load with parasitic inductance.

The invention can be used to design high-power switching power supplies, LED drivers, micro-inverters of photovoltaic panels, power factor correctors, etc. based on the topology of the flyback converter.

The flyback converter topology is attractive for widespread use because it has such advantages as simplicity, inexpensive implementation and high reliability, which is especially important for converters connected to a common power distribution network. The topology has a number of inherent disadvantages, including imperfect coupling of the magnetic fluxes of the transformer windings. Although the materials of magnetic cores are continuously improving, the technology of manufacturing the transformer remains unchanged, therefore the main disadvantage associated with the design - leakage inductance - has not yet been substantially eliminated. The leakage inductance affects the high voltage surges of the power transistors when turned off and the losses associated with the leakage energy of the magnetic field. Many attempts are being made to solve the problem of suppressing and limiting voltage surges as cheaply and efficiently as possible.

In the scientific literature, a simple method of limiting the voltage is widely known using the so-called RCD snubber, consisting of a series connected capacitance and a diode connected in parallel with the transformer winding, and a resistor connected in parallel with the capacitance. When the main transistor is turned off, the current is redirected through the diode of the voltage limiter circuit (snubber) to the snubber capacitance, thus the voltage across the transistor is limited by the voltage across the capacitance that absorbs the excess current. The energy accumulated during each switching in the snubber capacitance is continuously and irrevocably discharged through the snubber resistor. The disadvantage of this practice is the significant loss of dissipated energy. There are solutions that allow you to limit the voltage on the main switch and at the same time recover some or all (in theory) the energy associated with the scattering of the magnetic field.

A known device is a Flyback converter with a voltage limiting circuit (H2M 1/34), declared in WO 2016/155737 A1 for WIPO patent dated October 06, 2016, in which the diode in the known RCD snubber was replaced with a passively controlled auxiliary transistor switch. The purpose of the transistor auxiliary switch is to provide bidirectional conduction for a sufficient but short time interval to charge and discharge the snubber's capacitance. In this case, during this interval, the snubber capacitance would have the opportunity to accumulate the energy of the parasitic inductance, turn the current in the transformer winding and recuperate the energy back into the primary winding for transformation to the secondary side. The disadvantage of the known device is that the energy of the parasitic inductance is recovered, but partially so that a significant part is dissipated when the auxiliary switch is opened. The passive method of controlling the auxiliary switch is cheaper than the active one, but in the known device does not theoretically lead to a high recuperation efficiency.

The closest analogue of the claimed invention is a non-dissipative LC voltage limiter device (HO2H 7/122), declared in US patent No. 4489373 dated December 18, 1984. The aforementioned patent describes a lossless snubber (voltage limiter) device for use in switching converters, including a constant voltage source; at least one controlled key, the voltage on which must be limited; main inductance connected to said switch; load and a reverse shunt diode, and characterized in that it includes improvements: a capacitance, a first diode and an auxiliary inductance connected in series in the circuit and so that the resulting circuit is connected in parallel with the main switch, and the first capacitance terminal is connected to the connection of the said switch with the said main inductance ; the second diode is connected between the second terminal of said capacitance and the positive potential of said constant voltage source, said first and second diodes being oriented in polarity so as to block the current of said constant source applied to the circuit formed by said diodes and inductance. As stated in the patent, the load can be a transformer, in particular a flyback transformer, connected in series with said switch, then said main inductance will be the leakage inductance of the transformer. In steady-state conditions with a flyback transformer, the known circuit works as follows.

1. When the controlled switch is turned off, the leakage inductance of the transformer (main inductance) will maintain the current in the primary winding, charging the snubber capacitance through the second diode. At the same time, under a reverse voltage on the winding, that is, under the voltage of the charged capacitance, the current in the primary winding will unfold, the current in the secondary winding will increase. When the current of the primary winding of the transformer dropped to zero, the second diode was closed, and now the capacitance is discharged by the current of the auxiliary inductance. The auxiliary inductance current discharges the auxiliary inductance itself, discharges the snubber capacitance without loss, flows through the primary winding of the trans

- 1,038303 shapers, transferring energy losslessly to the secondary side.

2. When the controlled key is closed (opened), the snubber capacitance is connected in parallel to the auxiliary inductance and is discharged without loss to the auxiliary inductance through the first diode.

In theory, the known device has no power losses, in reality there are significant losses associated with high effective values of currents in the auxiliary inductance, snubber capacitance, switching of the first and second diodes, magnetization reversal of the auxiliary inductance. To increase the efficiency of the snubber, it would be desirable to reduce the effective values of the currents, which would be achieved if the auxiliary inductance was operated in continuous current mode. The disadvantage of the known device is that the device cannot always operate in the mode of continuous currents of the auxiliary choke. For example, if the open time of the controlled key is longer than its closed time, then the snubber capacitance will be more discharged by the auxiliary choke to a voltage value insufficient to block the primary winding current, which can lead to failure of the entire electronic converter. Thus, the inductance in the known device is chosen small enough to guarantee the intermittent current mode, which leads to high rms currents in all components of the snubber and, as a consequence, to limited energy recovery efficiency. In addition, a diode is connected in series with the inductance to prevent reverse current and reduce the reactive component, but the diode causes additional losses.

The closest tax of the claimed invention is a reverse-forward converter device with a non-dissipative voltage limiter (Н02М 3/335, Н02М 3/156), declared in US patent No. 9362831 B2 dated June 7, 2016. The known device is characterized by the presence of lossless voltage limiting circuits similar to the above-described known device, except that they are used for two transformer converter circuits, one transformer being a flyback, the other being a forward, fly-forward circuit. The disadvantage of the known device, as in the above-described known device, is that the device cannot always operate in the mode of continuous currents of the auxiliary choke.

The closest tax of the claimed invention is a voltage limiting device and a method for a DC voltage converter (Н02М), declared in WO 02/41479 A2 for a WIPO patent dated May 23, 2002, and a leakage inductance energy recovery device and a method for a flyback converter (Н02М 3/335), claimed in U.S. Pat. No. 6,473,318 B1, Oct. 29, 2002. Both devices use equivalent circuits for limiting the voltage on the main switch and recuperating the energy of the inductive load, in particular the energy of the leakage inductance of high frequency transformers. The known devices differ from those discussed above in that instead of the auxiliary inductance in the snubber, an additional winding of the load transformer is used, or, in other words, the auxiliary inductance is integrated with the load transformer. This has the advantage that when the main controlled key is closed, the snubber capacitance is discharged to the auxiliary winding of the transformer, thereby the energy is transferred back to the accumulation of magnetic energy of the transformer for subsequent transfer to the secondary side in the next cycle of the key when the main key is closed. However, the applied energy recovery scheme has a similar topology in comparison with the previous ones, a similar operating logic and suffers from the same disadvantage that it cannot be used in the continuous current mode to reduce losses when the duty cycle of the main switch is more than 0.5.

The tasks to be solved by the present invention are to provide a continuous current mode of operation for an inductive-capacitive voltage limiting circuit in a wide range of duty cycle of the main switch. The task is achieved by introducing additional measures to prevent excessive discharge of the auxiliary capacitance of the limiting circuit, so that the choke of the regenerative circuit can operate in continuous current mode.

The technical result will be to increase the efficiency of recuperation of the energy of the magnetic field leakage of the high-frequency transformer.

The technical solution to the problem is proposed by using a method for recuperating the dissipation energy of a flyback converter transformer, including at least one series-connected source of unipolar electrical power, a load and a pulse switch using at least one first electrical circuit, including at least one electrically connected in series. an auxiliary capacitor and at least one auxiliary switch;

at least one first auxiliary diode electrically connected in series with the first circuit;

at least one second electrical circuit, including at least one auxiliary choke, and the second circuit is electrically connected to the electrode of the series connection of the first auxiliary diode to the first circuit, and wherein the first auxiliary diode and the first circuit are electrically connected in series

- 2 038303 are connected in parallel to said load so that the first circuit is connected to the electrode of the series connection of said load to said switching switch, and the second circuit and the first auxiliary diode are electrically connected in parallel to said power supply in such a way that the first auxiliary diode is oriented in the direction of rectification current towards the positive electrode of the power source, in which on the first cycle, an open pulse switch, said auxiliary capacitor is discharged to said auxiliary choke through said pulse switch and said auxiliary switch;

on the second cycle, closed pulse switch, first, the load current is redirected through the first auxiliary diode to the first circuit, storing energy in the said auxiliary capacitor until the energy of the load inductance runs out, while the auxiliary inductor current is recovered to the said power source, and after energy of the load inductance, the first auxiliary diode closes, after which the auxiliary choke current now flows through the first circuit to the load, thus the energy stored in the auxiliary choke and the auxiliary capacitor is recovered into the load, and characterized in that the said auxiliary switch is passively or actively controlling said auxiliary switch so that the auxiliary switch can open the first circuit in the first cycle, for all or part of the time of the first cycle, to prevent the auxiliary capacitor from discharging below a set voltage value.

The technical solution to the problem is also proposed through the use of a device for recuperating the dissipation energy of the flyback converter transformer, which includes at least one unipolar power supply source, at least one load and at least one controlled pulse switch, such that the mentioned load, pulse switch and source the power supplies are electrically connected in series;

at least one first electrical circuit including at least one auxiliary capacitor;

at least one first auxiliary diode electrically connected in series with the first circuit;

at least one second electrical circuit including at least one auxiliary choke, and the second circuit is electrically connected to an electrode of the series connection of the first auxiliary diode to the first circuit, and wherein the first auxiliary diode and the first circuit are connected in series in parallel to said load so, that the first circuit is connected to the electrode of the series connection of said load to the said pulse switch, and the second circuit and the first auxiliary diode are electrically connected in parallel to the said power supply in such a way that the first auxiliary diode is oriented in the direction of rectifying the current towards the positive electrode of the power supply, and different in that the first electrical circuit additionally includes at least one auxiliary switch electrically connected in series to said auxiliary capacitor, with the possibility of passive or active control with said auxiliary switch to prevent the discharge of said auxiliary capacitance below a predetermined value, for example, by opening the first circuit for the entire time or a fraction of the time of the open state of said pulse switch.

Universal block diagrams of the claimed technical solution implementations are shown in FIG. 1 and FIG. 2.

FIG. 3, 4, 5 are given to explain the operation of the claimed device and show equivalent circuits in the operation cycles of the device during the switching period of the main impulse switch. FIG. 3 is an equivalent diagram of the first cycle of the device. FIG. 4 is an equivalent circuit of the second cycle of operation of the device when parasitic inductance is acting. FIG. 5 is an equivalent circuit of the second cycle of operation of the device when the energy of the parasitic inductance has dried up.

FIG. 6 shows a block diagram of the claimed device as applied to a flyback converter.

FIG. 7 shows a block diagram of the claimed device as applied to a forward converter.

FIG. 8 shows a block diagram of the claimed device as applied to a flyback converter with an auxiliary choke integrated with a transformer.

FIG. 1 and 2 clearly explain that the claimed device for recuperating the energy dissipation of the flyback transformer transformer itself consists of a series auxiliary capacitor 101 and an auxiliary switch 105, constituting the first electrical circuit; the first auxiliary diode 104; an auxiliary choke 102 forming a second electrical circuit. Moreover, the order of the serial connection of the capacitor 101 and the key 105 in the first circuit can be any. FIG. 1 and 2 also show the power supply 108 loaded on the successor.

- 3 038303 but connected load 107 and the pulse switch 106. The auxiliary diode 104 and the first circuit are connected in series and are connected together in parallel with the load 107 in such a way that the first circuit is connected to the connection point of the load 107 and the pulse switch 106, and the sequential first auxiliary diode 104 and the second circuit, consisting of a choke 102, turns out to be connected in parallel with the power source 108, and so that the diode 104 is oriented in the direction of current rectification towards the positive electrode of the source 108. The load 107 can be a resistive load with parasitic inductance, it can be an inductive load, it can be a transformer in which the secondary side is loaded on the secondary circuits, and the primary winding is used for connection according to the diagram in FIG. 1. or according to the diagram in FIG. 2. The logic of the device is the same as in the implementation according to the diagram of FIG. 1 and according to the diagram in FIG. 2, which differ in the order of sequential switching on of the load and the pulse switch relative to the positive terminal of the power supply. If a field effect transistor is used as the pulse switch 106, then the circuit in FIG. 1 will be a circuit with the source of the transistor, the main switch, tied to a constant zero potential, and the circuit in FIG. 2, respectively - with the source of the transistor, the main switch, tied to the floating potential. FIG. 1 shows a capacitor 109 that can be applied and connected in parallel with a power supply to reduce the source impedance at high frequencies.

The claimed method and operation of the claimed device will be illustrated by the example of the implementation shown in FIG. 1. The general requirement for the operation of all converters is the requirement to observe the ampere-second balance for all capacitive components and the volt-second balance for all inductive components of the converter during the period of operation of the pulse switches. That is, the voltage across the auxiliary capacitor 101 should be sufficient to reversal the inductance or parasitic inductance of the load 107. Suppose that the voltage Ux across the capacitor 101 is large enough, and the auxiliary switch 105 is always open. Upon opening of the controllable pulse switch 106, the first cycle in FIG. 3, the load 107 is connected to the power supply, while the auxiliary capacitor 101 is discharged through the public switch 106 to the auxiliary inductance 102, and the auxiliary diode 104 in FIG. 1 is locked. The volt-second integral of the first cycle acting on the auxiliary choke 102 is equal to Ux * D * T, where D is the duty cycle and T is the period of the pulse switch 106. When the switch 106 is closed, the second cycle in FIG. 4, due to the load inductance 107, the current is not interrupted and is redirected through the auxiliary diode 104 to the first circuit, charging the capacitor 101 for a time until the energy of the load inductance runs out, at the same time through the diode 104 the choke 102 is discharged to the source 108, thus without losses recuperating back to the source the energy received from the capacitor 101 in the previous, first cycle. If the voltage Ux is large enough, then the load current dries up in a time shorter than the time of the second cycle, the diode 104 will close, and the inductance current 102 remaining until the beginning of the first cycle of the next period will flow through the first circuit into the load, see Fig. 5. In this way, energy is now recovered without loss directly to the load. But with large values of the duty cycle D of the pulse switch, the time of the second cycle (1-D) * T for magnetizing the load inductance is reduced, and the diode 104 will be open almost all the time of the second cycle, then the volt-second integral of the second cycle for inductor 102 is almost equal to -Uin (1-D) T, where Uin is the voltage of the power source 108. At high duty cycle values, the auxiliary capacitor 101 will discharge more into the choke 102, its voltage will decrease. Let us find the value of Ux at large D. Since the current of the auxiliary inductor must be continuous to increase the efficiency of the declared regenerative device, then for the inductor 102 it is possible to write down the volt-second balance for the entire period Ux * D * T = Uin (1-D) T, from here we find the equilibrium value voltage for auxiliary capacitor 101, Ux = Uin (1-D) / D. It can be seen that at large values of the duty cycle (D is close to 1), the voltage across the auxiliary capacitor 101 can be discharged by the auxiliary choke to small values and insufficient for the magnetization reversal of the load, which will lead to unstable operation of the converter, an increase in losses and other catastrophic consequences. Moreover, with an increase in the duty cycle, the value of the required magnetization reversal voltage for the load increases, since the time of application of the reverse voltage decreases according to (1-D) * T. To prevent excessive discharge of the capacitor in the first cycle of the pulse switch, an auxiliary switch 105 is provided, with the possibility of passive or active control. The switch 105 can be closed for a specific time interval of the first cycle, reducing the discharge time of the auxiliary capacitor, and be open during the second cycle to charge the auxiliary capacitor. This makes it possible to increase the range of operating values of the duty cycle of the impulse switch in comparison with known devices while maintaining the condition of current continuity for the auxiliary choke 102 and without disrupting the operation of the converter. In the known devices, it is impossible to provide the best conditions for recuperating the energy of the parasitic inductance when the pulse converter operates with the duty cycle of the main switch equal to or higher than 0.5.

The advantage of the proposed solution is that the optimal converters, from the point of view of reducing the effective values of currents and increasing the power efficiency, are designed to operate with a nominal duty cycle D of about 0.5, and the declared device will allow the converter to operate at a duty cycle of more than 0.5 and at the same time will have the best efficiency. recuperator

- 4 038303 load inductance energy as the inductor of the claimed regenerative device has the ability to operate in continuous current mode. In addition, in this mode it is not necessary to use an auxiliary diode connected in series with said inductor to prevent current reversal.

The load in the claimed device can be a transformer connected according to a flyback conversion circuit, for example, with an asymmetrically loaded primary inductance (SEPIC), or a flyback converter itself. FIG. 6 shows one of the implementations of the claimed device and its application in the flyback converter circuit with galvanic isolation. FIG. 6 shows that a transistor, in this case a field-effect transistor, can be used as an auxiliary switch 105. A transformer with a secondary circuit connected according to the flyback converter circuit is used as the load 107. The secondary circuit contains a rectifier diode 112, a ripple dampening capacitor 113, and a load can be connected. FIG. 6 shows a case where a transistor, in this case a field-effect transistor, is used as the pulse switch 106. If we assume that the voltage across the capacitor 101 is sufficient to reverse the magnetization of the transformer 107 and the auxiliary switch 105 is always on, then, provided that the primary winding current drops rapidly when the switch 106 is closed, an expression for the auxiliary capacitor voltage can be found: Ux = Uin. It is known that the required voltage of the primary winding for the magnetization reversal of the flyback transformer 107 is equal to Uin * D / (1-D). It can be seen that when the duty cycle is greater than 0.5, the voltage on the auxiliary capacitor will be less than that required for the magnetization reversal of the flyback transformer. To prevent an undesirable phenomenon, the key 105 is used according to the above method. In addition, since the auxiliary field-effect transistor 105 has a built-in diode, it is possible to operate when the transistor 105 can be closed for a certain number of periods of the pulse switch while the auxiliary capacitor is charged to a certain value, and be open for a certain number of periods while the capacitor 101 is discharged. to the minimum allowed voltage value. In this case, when the switch 106 is turned off, the capacitor 101 is charged by the parasitic inductance of the transformer 107 through the diode 104 and the internal diode of the turned off field-effect transistor 105, in the case of the transistor 105, oriented to conduct current in the same direction as the diode 104.

The auxiliary switch of the claimed device for recuperating the dissipation energy of the flyback converter transformer can be actively controlled, that is, synchronized with the pulse switch, for example, using a controller that controls the pulse switch.

In the claimed device, the auxiliary switch can be controlled passively, for example, by means of an additional auxiliary winding of the transformer, to power the control passive circuit and generate control signals for the auxiliary switch. FIG. 6, a passive method of controlling the voltage level on the auxiliary capacitor is implemented, when the auxiliary switch is controlled by the comparator circuit 201, which closes the switch 105 if the capacitor 101 is discharged to the minimum allowed voltage, and opens the switch 105 if the capacitor 101 is charged with a margin above the minimum allowed voltage. A divider 203, for example a resistive divider, is used to measure the voltage across the capacitor 101. Here, in particular, the auxiliary capacitor 101 is the power supply for the passive driving circuit 200.

The load in the claimed device can be a transformer connected according to the Forward converter circuit, as shown in FIG. 7. FIG. 7 shows one of the implementations of the claimed device, when the load 107 is a transformer connected according to the forward converter circuit. FIG. 7 additionally introduced rectifier diode 115, output choke 114.

The claimed device may additionally include a second auxiliary diode 103 shown in FIG. 7, connected in series with an auxiliary choke 102, and the sequence of activation can be any. The second auxiliary diode should be oriented in the direction of current rectification towards the positive electrode of the power source 108 and serves to prevent the current reversal in the choke 102 with significant current ripple in it.

In the claimed device, the auxiliary choke can be integrated with the transformer, that is, it is an additional auxiliary winding of the transformer, having a magnetic flux coupling with the primary winding of the transformer, as shown in FIG. 8. As an auxiliary inductance 102, an additional Naux-102 winding is used, for example, a flyback transformer 107.

The auxiliary inductor, or the auxiliary winding used as the auxiliary inductor, may be tapped to supply other external or internal circuits of the device, such as control circuits and the like. FIG. 8 shows that a circuit 117, such as a switching controller, is powered by an auxiliary winding 102 tapped through a diode 116.

In all implementations, the claimed device may include a current sensor connected electrically in series with the pulse switch to measure the pulse switch current and implement various control schemes.

Claims (20)

CLAIM 1. A device for recuperating the energy dissipation of the flyback converter transformer, including at least one unipolar power supply source, at least one load and at least one controlled pulse switch, such that said load, pulse switch and power supply are electrically connected in series; at least one first electrical circuit including at least one auxiliary capacitor; at least one first auxiliary diode electrically connected in series with the first circuit; at least one second electrical circuit including at least one auxiliary choke, and the second circuit is electrically connected to an electrode of the series connection of the first auxiliary diode to the first circuit, and wherein the first auxiliary diode and the first circuit are connected in series in parallel to said load so, that the first circuit is connected to the electrode of the series connection of said load to the said pulse switch, and the second circuit and the first auxiliary diode are electrically connected in parallel to the said power supply in such a way that the first auxiliary diode is oriented in the direction of rectifying the current towards the positive electrode of the power supply, and different in that the first electrical circuit additionally includes at least one auxiliary switch electrically connected in series to said auxiliary capacitor, with the possibility of passive or active control with said auxiliary switch to prevent the discharge of said auxiliary capacitance below a predetermined value, for example, by opening the first circuit for the entire time or a fraction of the time of the open state of said pulse switch. 2. The device according to claim 1, including at least one additional capacitor connected in parallel with said power supply. 3. The apparatus of claim 1, wherein said auxiliary switch comprises at least one field-effect transistor that can be oriented such that its internal diode rectifies current in the direction in which it rectifies the first auxiliary diode connected in series to the first circuit. 4. The device according to claim 1, wherein said pulse switch comprises at least one field-effect transistor controllable from a pulse-width or pulse-frequency modulating controller. 5. An apparatus according to claim 1, wherein said load comprises at least one transformer, and the primary winding of said transformer is connected in series with said power supply and a pulse switch. 6. The apparatus of claim 5, wherein said transformer is used in a flyback topology. 7. The apparatus of claim 5, wherein said transformer is used in a forward conversion topology. 8. The apparatus of claim 5, wherein the auxiliary choke is integrated with said transformer, that is, it is an auxiliary winding having magnetic flux engagement with the primary winding of said transformer. 9. The device according to claim 1, wherein said auxiliary choke has a branch for supplying external or internal electrical circuits of the claimed device. 10. A device according to claim 8, wherein said auxiliary transformer winding has a branch for supplying external or internal electrical circuits of the claimed device. 11. The device according to claim 1, including at least one current sensor, electrically connected in series with the pulse switch. 12. The apparatus of claim 1, wherein the second electrical circuit includes at least one second auxiliary diode in series electrically connected to said auxiliary inductor, the second auxiliary diode being polarly oriented so as to rectify current towards the positive electrode of said power source. 13. A method for recuperating the dissipation energy of a flyback converter transformer using the device according to claim 1, wherein said pulse switch is opened in the first cycle, said auxiliary capacitor being discharged to said auxiliary choke through the pulse switch and said auxiliary switch; on the second cycle, the impulse switch is closed, then first the load current is redirected through the first auxiliary diode to the first circuit, storing the energy of the said auxiliary capacitor - 6 038303 torr until the energy of the load inductance runs out, while the auxiliary inductor current is recovered to the said power source , and after the energy of the load inductance has expired, the first auxiliary diode closes, after which the auxiliary choke current now flows through the first circuit to the load, thus the energy stored in the auxiliary choke and the auxiliary capacitor is recovered to the load, and characterized in that said auxiliary switch open in the first cycle, for all or part of the time of the first cycle, to prevent the auxiliary capacitor from discharging below the set voltage value. 14. The method of claim 13, wherein said auxiliary switch comprises at least one field effect transistor. 15. The method of claim 13, wherein said pulse switch comprises at least one field-effect transistor controllable from a pulse-width or pulse-frequency modulating controller. 16. The method of claim 13, wherein the second electrical circuit includes at least one second auxiliary diode in series electrically connected to said auxiliary inductor, the second auxiliary diode being polarly oriented so as to rectify current in the direction of the first circuit. 17. The method of claim 13, wherein said load comprises at least one transformer, wherein the primary winding of said transformer is connected in series with said power supply and a pulse switch. 18. The method of claim 17, wherein said transformer is used in a flyback topology. 19. The method of claim 17, wherein said transformer is used in a forward conversion topology. 20. A method according to claim 17, wherein the auxiliary choke is integrated with said transformer, that is, is an auxiliary winding having magnetic flux engagement with the primary winding of said transformer.