WO2000031872A1

WO2000031872A1 - Pulsed power generator with energy recovery and energy regulation

Info

Publication number: WO2000031872A1
Application number: PCT/IL1999/000635
Authority: WO
Inventors: Israel Smilanski
Original assignee: Rotem Industries Ltd
Current assignee: Rotem Industries Ltd
Priority date: 1998-11-26
Filing date: 1999-11-25
Publication date: 2000-06-02
Anticipated expiration: 2001-05-26
Also published as: AU1406200A; IL127302A0

Abstract

A method for recovering the energy that is reflected from a load, upon providing a pulse of power to it in a pulsed power generator, the said pulsed power generator having a storage capacitor, which is charged from a resonant charging circuit in forward polarity, the method being characterized by a voltage regulator that is used in said charging circuit for effecting a current flow carrying the charge accumulated in the said storage capacitor in reversed polarity that is due to said energy reflection, said current flowing through a DC power supply feeding said resonant charging circuit, back to said storage capacitor for charging it in forward polarity.

Description

PULSED POWER GENERATORWITH ENERGYRECOVERYAND

ENERGY REGULATION

Field of the Invention

The invention relates to pulsed power circuits. More particularly, the invention relates to means for regulating energy, recovering energy, increasing efficiency, and improving the reliability of pulsed power circuits.

Background of the Invention

Pulsed power is widely used in the art when it is needed to provide to a load pulses of high power. Pulsed power is used, for example, for exciting lasers, for activating magnetrons or klystrons in radar systems, or in other applications in which a supply of high-power pulses is required. In order to provide high energy and short-duration pulses, i.e., high power pulses, it is common to use a circuit comprising a storage capacitor to charge the same with an electric charge from a charging circuit, and to rapidly discharge the capacitor into the load. In some cases, the storage capacitor is replaced by a Pulse Forming Network (P.F.N), which is a network comprising a plurality of capacitors (hereinafter, when the term "storage capacitor" is used, it should be noted that it may also refer to the use of a P.F.N).

There are several types of circuits for charging the storage capacitor of a pulsed power (hereinafter "the charging circuit"). When a pulsed power is required to provide high power pulses in a relatively low frequency, e.g., in the range of about 1-100 Hz, it is common to use a Capacitor Charging Power Supply (CCPS), which generates and supplies to the storage capacitor a plurality of low power charging pulses for each single high-power pulse at the output of the pulsed power generator. When a higher pulse rate is desired at the output of the pulsed power generator, e.g., in the range of several kiloHertz, it is preferable to use a resonance charging circuit. In that case, the charging circuit comprises a DC source, in series with an inductive component and a first switching component. During the charging period, the components of the charging circuit form a serial resonant circuit with the storage capacitor. The inductive component in the charging circuit enables the establishing of a high Q in the circuit, and the said first switching component controls the times in which charge is supplied to the storage capacitor.

The resonance charging circuit provides a uni-polar charge to the storage capacitor during a period designated for charging, hereinafter referred to as "the charging period". During the charging period, a second switching element in the pulsed power generator, such as an SCR, Thyratron, Spark gape, etc. (hereinafter, although the switching components can be of different types, it is assumed that switching components of the SCR type are used. Therefore, for convenience throughout the application the terms "switching component" and "SCR" are used synonimously), which is located in the branch connecting the storage capacitor and the load, is kept in an "OFF" state, thereby inhibiting current flow and discharge of the storage capcitor to the load, and allowing charge accumulation in said capacitor. When the charge in the storage capacitor reaches a predetermined desired level, the operation of the resonance charging circuit is deactivated. A control signal can now be provided to the second switching element, thereby to turn it ON and cause the capacitor to rapidly discharge its accumulated charge into the load. Said capacitor discharge takes place during a period hereinafter referred to as "the discharging period", a period which is much shorter than the above-mentioned charging period. Therefore, the pulsed power circuit actually provides a power gain of the ratio τι/τ₂, wherein τi is the charging period, and τ₂ is the discharging period. Generally, the load to which the power pulses are supplied is not purely resistive, but has a complex nature. To the complex nature of the load may further be contributed parasitic inductivity of the circuit conductors, the inductivity of magnetic compression elements, if existing, or any complex contribution from other possible elements in the circuit. This complex nature, if mismatched with the previous circuit, allows only a portion of the energy to dissipate on the load, and causes the rest of the energy to be reflected back from it in the form of some damped oscillations. These oscillations, above and below the zero potential level, tend to cause the storage capacitor to alternatively charge and discharge in alternating directions. These oscillations may continue as long as the second switching element is ON, and stop only when it switches to OFF. The switching OFF of the second switching element occurs only after a characteristic recovery period of the second switching element lapses, in which the current through it is below some current level I_n. The said oscillations, involve in some cases energy reflection from the load of as high as 20% of the total storage capacitor discharge energy, and are harmfull to the circuit components and tend to disturb its proper operation. Special means are required in order to remove this reflected energy from the circuit. One such means for solving the problem of the energy reflected from the load, when using a resonant charging circuit for charging the storage capacitor, is called "a snubber". The snubber generally comprises a diode for directing the reflected energy into a serial resistive element in which the reflected energy is dissipated. The resistive element should therefore be capable of maintaining the significant amount of power resulting from the reflected energy. This resistive element therefore generally has a high volume, requires special means for cooling it, and is expensive. Moreover, the use of a snubber for dissipating the reflected energy significantly reduces the efficiency of the whole circuit, as a high amount of the total energy is wasted by dissipation into that resistive element.. The snubber solution to this problem, and all other solutions which have been suggested up to now for the removal of the reflected energy in cases of using a resonant charging circuit are located in the pulsed power generator, and away from the resonant charging circuit which charges the storage capacitor.

Another problem, which is characteristic of resonant charging circuits, is the problem of energy regulation. In some cases, when the first switching component is turned OFF at the end of the charging period, some electromagnetic energy remains occluded in the inductive component of the resonance charging circuit. This energy, if not suitably treated, is lost energy that reduces the efficiency of the whole apparatus, and moreover, causes a significant, high-power voltage spark that may damage the circuitry. One common way to solve the problem is to return the remaining energy back to the DC power supply, and to resupply it to the storage capacitor in the next charging period. Resonant charging circuits which comprise means for returning the said energy to the DC power supply (hereinafter: "energy regulation") are also known.

As mentioned, the said two energy problems occur at different times. The problem of the energy occluded in the inductive component occurs at the end of the charging period and before the discharge of the storage capacitor takes place. The problem of the energy reflected from the load occurs after the discharge of the storage capacitor, and before the next charging period of the capacitor (hereinafter V_c(0 ). Circuits which are devoted to separately solving one of said problems are known. There is no known single, simple and compact circuitry which can concurrently solve the said two energy problems. Moreover, in resonance charging circuits, the following formula holds:

V_C = 2V_CC - V_C(0^~ ) where V_c denotes the target voltage to which the storage capacitor charges, V_cc is the voltage of the DC power supply, and V_c(0^~) is the voltage of the storage capacitor at the beginning of each charging period. V_c(0^~) , of course, depends also on the energy reflected from the load in the previous discharging period. A situation in which V_c(0^~) is not zero should not be allowed, as it may cause the storage capacitor to charge each period to a higher voltage than in a former period, up to a voltage that the circuit cannot sustain, that may result in failure of one or more components of the circuit. Therefore, it is highly desirable to provide means for assuring output pulses of the same power from the pulsed power generator, no matter how much energy is reflected from the load, and is stored in the storage capacitor prior to the charging period. This task is also accomplished by the invention.

The use of a voltage regulator for solving the problem of the energy occluded in the inductive component of the resonant charging circuit, i.e., for carrying out energy regulation, has been well known in the art for a long time now. For example, such a circuit is described in 'Godfrey T. Coate & Laurence R. Swain, Jr., "High-Power Semiconductor-Magnetic Pulse Generators", pages 57-63, The MIT Press, Cambridge, Massachusetts, 1966' and is also disscussed in 'Robert J. Froelich, "A high efficiency dequeing circuit for a thyratron modulator" IEEE pages 177-180, 1992'. However, in the prior art when the voltage regulator has been used in conjunction with a pulsed power generator, it has been solely used for solving the energy regulation problem. When a solution to the problem of the energy reflected from the load was needed, the use of separate circuitry was required, such as a snubber, or another suitable solution, which dealt with this energy remote from the charging circuit. It has been found by the inventors that the a voltage regulator can concurrently solve the said two energy problems, and there is no need for using any separate, inefficient means, as has been used used in the prior art, for carrying out the energy recovery.

It is therefore an object of the invention to provide means for recovering the energy reflected from the load in pulsed powers which are fed by resonance charging circuits.

It is another object of the invention to provide means for returning to the DC power supply the energy occluded in the inductive component of the resonance charging circuit.

It is still another object of the invention to increase the efficiency of existing pulsed powers, by recovering unused energy.

It is a further object of the invention to provide means for assuring that the pulsed power will provide to the load always pulses of equal power.

It is still an object of the invention to improve the reliability and durability of pulsed powers.

It is a further object of the invention to accomplish the said objects by a simple low-cost and compact circuitry.

Other objects and advantages of the invention will become apparent as the description proceeds. Summary of the Invention

The invention relates to a method for recovering the energy that is reflected from a load, upon providing a pulse of power to it in a pulsed power generator, the said pulsed power generator having a storage capacitor, which is charged from a resonant charging circuit in forward polarity, the method being characterized by using a voltage regulator in said charging circuit for effecting a current flow carrying the charge accumulated in the said storage capacitor in reversed polarity due to said energy reflection, said current flowing through a DC power supply feeding said resonant charging circuit back to said storage capacitor for charging it in forward polarity.

Preferably, the said voltage regulator is also used for carrying out energy regulation, by returning the energy remaining in the inductive element at the output of said charging circuit back to the DC power supply, after termination of the charging current to the said storage capacitor.

The energy recovery according to the method of the invention takes place after providing a pulse of power by said pulsed power generator to the load, during subsequent charging of the storage capacitor of said pulsed power generator.

Preferably, the voltage regulator comprises at least one transformer having primary and secondary windings, and at least one switching component. The said switching component may be, for example, an SCR.

The resonant charging circuit preferably comprises, in addition to said voltage regulator, a DC power supply for providing energy, and a second switching component for initiating and terminating charging of the storage capacitor of the pulsed power circuit. More particularly, the invention relates to a method for resonantly charging a storage capacitor of a pulsed power, which comprises: a. Providing a DC power supply; b. Providing a transformer having primary and secondary windings, the primary winding of the transformer being connected to the DC power supply and forming a series resonant circuit with the said storage capacitor of the pulsed power; c. Providing a first switching component in series to the primary winding of the transformer; d. Providing a second switching component in series to the secondary winding of the transformer; e. Predefining a voltage level to which the storage capacitor should charge and providing means for continuously sensing the voltage level of the capacitor; f. Commencing a charging period by first turning ON the first switching component to effect current flow, that first recovers the energy previously reflected from the load, by transferring any charge accumulated in reversed polarity in the storage capacitor, through the DC power supply, the primary winding, and the first switching component back to the storage capacitor in forward polarity, and simultaneously charge the storage capacitor with the charge originating from the DC power supply; g. Providing a sensing unit for checking the voltage level of the storage capacitor; h. When the voltage level of the storage capacitor reaches the said predefined voltage level as checked by the said sensing unit, turning ON the second switching component, thereby to produce a voltage over the secondary winding, that is induced to the primary winding, thereby causing the first switching component to turn OFF, terminating the charging current to the storage capacitor. The current flow through the secondary winding further returns any energy remaining in the primary winding due to the termination of the charging current back to the DC power supply.

Said method is characterized in that it provides both recovery of the energy reflected from the load in the pulsed power to which it is connected, and regulation of the energy remaining in the primary winding upon termination of the charging current.

Preferably, the said first and second switching components are SCRs. Alternatively, the first and second switching components can be Thyratrons.

Preferably, the transformer is a step -up transformer, wherein the secondary winding has 7ϋ times windings in comparison to the number of windings in the primary winding, and m is an integer greater than 1.

The invention also relates to a circuit for resonantly charging the storage capacitor of a pulsed power, which comprises:

a. A DC power supply; b. A first transformer having primary and secondary windings, a first end of the primary winding and a first end of the secondary winding being connected to the positive pole of the DC power supply; c. A first controlled switch connected between the second end of the primary winding and the storage capacitor, for enabling current flow from the DC power supply through the primary winding to the storage capacitor, or preventing the same; d. A second controlled switch connected between the second end of the secondary winding of the transformer and the negative pole of the DC power supply, for allowing or terminating current flow in the secondary winding of the transformer; e. A control unit for activating the first switch, for sensing the voltage of the storage capacitor, and for activating the second switch when the voltage on the storage capacitor is above a predefined threshold level.

The said resonant charging circuit is characterized in that, when it is connected to a pulsed power, it effects recovery of the energy reflected from the load, and regulates the energy remaining in its inductive component upon termination of its charging operation.

The first and second controlled switches of the circuit for resonantly charging the storage capacitor of a pulsed power, according to a preferred embodiment of the invention, are SCRs.

According to a preferred embodiment of the invention, the winding ratio between the secondary winding and the primary winding of the first transformer is ni'.l,

being an integer larger than 1.

According to a preferred embodiment of the invention, the circuit for resonantly charging the storage capacitor of a pulsed power, further comprises a diode, and a second transformer having a primary and secondary windings, a first end of the primary winding of the second transformer is connected to the first end of the secondary winding of the first transformer, and the second end of the second transformer is connected to the second switch, the first end of the secondary winding of the second transformer is connected to the negative pole of the DC power supply, the diode is connected to the positive pole of the DC power supply and to the second end of the secondary winding of the second transformer, thereby to allow current to flow in the direction from the secondary winding towards the positive pole of the DC power supply. Preferably, the winding ratio between the primary and secondary windings of the first transformer is l:n_?, and between the primary and secondary windings of the second transformer is ns.-l, n∑ and ns being integers larger than 1.

More generally, the invention relates to an apparatus for generating a high power pulse into a load, which comprises:

- a pulsed power generator for providing a pulse of power into said load; and

- a resonant charging unit which comprises a voltage regulator, for providing energy to said pulsed power generator;

The apparatus is characterized in that the pulsed power generator does not have means for dissipating or absorbing energy that is reflected from the load, but instead, said voltage regulator in the resonant charging unit maneuvers said reflected energy into a DC power supply feeding the apparatus, or back to the pulsed power generator, the proportions are determined by the voltage regulator.

Preferably, the means for maneuvering the reflected energy into the resonant charging unit, and back to the pulsed power generator, is a voltage regulator located in the resonant charging unit.

Brief Description of the Drawings

In the drawings:

- Fig. 1 shows the basic structure of an exemplary apparatus which comprises a pulsed power generator fed by a resonant charging circuit; - Fig. 2 shows a pulsed power generator circuit fed by a resonant charging circuit according to one embodiment of the invention;

- Fig. 3a illustrates the voltage across the storage capacitor of the pulsed power circuit;

- Fig. 3b illustrates the current through the SCR at the secondary winding of the transformer shown in figure 2;

- Fig. 3c illustrates the current through SCR 6 of figure 2;

- Fig. 3d illustrates the current through SCR 9 of figure 2;

- Fig. 3e illustrates the voltage on the cathode of SCR 37 at the secondary winding of the transformer;

- Fig. 4 shows a pulsed power generator fed by a resonant charging circuit, with energy recovery and energy regulation, according to another embodiment of the invention.

Detailed Description of Preferred Embodiments

Fig. 1 shows a basic structure of an apparatus which comprises a pulsed power fed by a resonance charging circuit. This structure is given here for illustrative puposes, as it demonstrates the necessity and importance of the invention. The resonance charging circuit 4 comprises a DC power supply 2, an inductor 5, and first switch 6. The switch 6, for example, an SCR, controls the charging of the storage capacitor 7 of the pulsed power generator 1. When the first switch 6 is ON, a charging current flows from the DC power supply, through inductor 5 and the first switch 6, to charge the storage capacitor 7. During the charging period of the storage capacitor 7, the switch 9 is OFF. When the charge in the storage capacitor 7 accumulates to a sufficient level, switch 6 is forced to turn OFF in order to stop the charging of storage capacitor 7. Then, a control signal is provided to the control 16 of the second switch 9, to turn it ON, and to cause the charge of the first storage capacitor to discharge into the second storage capacitor 19. The second storage capacitor 19 and the saturable-core inductor 20, form a pulse compression unit 24, for compressing the pulse to the load 21. More particularly, the pulse compression unit increases the power of the pulse by making its duration shorter and its power intensity higher. The pulse compression means 24 may comprise one or more stages of a storage capacitor 19 and saturable-core inductor 20, as is known in the art. When the saturable-core inductor saturates, the second storage capacitor 19 discharges into the load 21, causing a high power pulse.

The basic apparatus of Fig. 1 suffers from the following major drawbacks:

1. If switch 14 is turned OFF while the current through it is not zero, there may be some energy remaining occluded in the inductor 5. In this structure this energy, if not properly treated, can cause a significant spark that may endanger some of the circuit components.

2. The reflected energy from the load accumulates in a form of a charge in the storage capacitor 7, generally in a reversed polarity than that required. More particularly, the charge in the storage capacitor 7 accumulates so that the potential of its plate 7b is more positive than that of its plate 7a.

The apparatus of the invention provides a compact circuit for satisfying all of the abovementioned demands. Fig. 2 illustrates a pulsed power generator circuit fed by a resonant charging circuit according to one embodiment of the invention. The apparatus comprises a transformer 55 replacing the inductor 5 of the apparatus of Fig. 1, an additional third switching component, SCR 37, and a control circuit comprising the two resistors 57 and 58, and comparator 56. Figs. 3a, 3b, 3c, 3d, and 3e are timing diagrams illustrating the current and voltage signals in different parts of the circuit. Fig. 3a illustrates the voltage over the storage capacitor 7, Fig. 3b the current through SCR 37, Fig. 3c the current through SCR 6, Fig. 3d the current through SCR 9, and Fig. 3e the voltage on the cathode of SCR 37.

At the beginning of the charging period, Ti, SCRs 9 and 37, are OFF, and SCR 6 is turned ON by providing to its control 14 a positive command pulse. At that time, the transformer 55 can be considered as an inductor, as only its primary inductor 55a is connected, and the loop of the secondary winding 55b is open. Current starts to flow through the primary inductor 55a, and through SCR 6 to charge the first storage capacitor 7 The voltage Vc over the first storage capacitor can be expressed by the following formula:

(1) Vc(t) = Vcc [l-Cos(ωt)] + V_c(0)Cos(ωt)

wherein Vcc is the voltage of the power supply 2, Vc(0) is the voltage of storage capacitor 7 when the charging starts, and ω is the resonance frequency of the resonant circuit comprising the primary winding 55a of the transformer 55, and the storage capacitor 7. If, as is generally the case, at the beginning of the charging period Ti, the storage capacitor 7 is reversely charged due to an energy reflected from the load, the closure of SCR 6 first causes a current to flow from the storage capacitor plate 7b, through the negative pole of the power supply 2, the primary winding 55a, to plate 7a of the storage capacitor 7, thereby reversing the polarity of the charge in the storage capacitor 7. There is voltage induction Vs from the primary winding 55a to the secondary winding 55b, according to formula (2), which describes the voltage on the cathode of SCR 37:

(2) V₈(t) = cc [l+mCos(ωt)] - m V_c(0-)Cos(ωt)

wherein m is the winding ratio of the transformer. Fig. 3e describes the voltage Vs(t). It can be seen that the voltage Vs is positive at the beginning of the charging period Ti, and becomes negative later, e.g., at T3. More particularly, from the following formula

-V,

(3) Cosa =

",[^ - ^(0)]

the angle α at which the voltage Vs is negative can be determined. Comparator 56 samples the potential on the first storage capacitor 7 by receiving at its positive input the potential of point 61 between resistors 57 and 58, a potential which directly relates to the potential of plate 7a. When the potential of plate 7a of the storage capacitor 7 reaches a certain, predefined level Vi, at time T4, the comparator 56, which compares the voltage of point 61 to a reference voltage Vre_f, provides a command signal through transformer 17 to the control 40 of SCR 37 to turn it ON. Transformer 17 provides a buffer between comparator 56 and the high voltage of SCR 37, and protects it from that high voltage. At that time, T4, the potential on the cathode of SCR 37, is negative with respect to the potential on its anode, and therefore SCR 37 turns ON. Turning ON SCR 37, causes the voltage of the power supply to spread over the secondary winding 55b, which in turn induces a negative voltage to the primary winding, thereby reversely biasing SCR 6, and turning it OFF. Turning OFF SCR 6 causes a sudden termination of the charging current to the storage capacitor, which leaves energy occluded in the transformer 55, that if not properly treated is lost energy, and moreover, may cause a significant spark that endanger components of the circuit. By means of the circuit of Fig. 2, however, this problem is eliminated by returning this energy to the power supply. Turning ON SCR 37 at T₄ produces a current flow through SCR 37 and the secondary winding in a counterclockwise direction 66 to the power supply 2, a current which empties the transformer 55 from its energy, and transfers the energy back to the power supply for use in the next charging period.

The apparatus of Fig. 2 assures uniform pulses of the same energy into the load, no matter how much energy was returned from the load in the previous discharging period. The energy of the pulses to the load can be accurately adjusted by defining the level of ref. The voltage Vref is provided to the comparator 56 as a reference. A higher Vref, enables a longer charging period and accumulation of more energy in the storage capacitor 7, and therefore pulses of higher energy to the load. Moreover, the reflected energy while being conserved, is removed from the pulsed power generator section to which it is harmful.

Fig. 4 shows a pulsed power circuit with energy recovery and energy regulation according to another embodiment of the invention. This circuit is similar in its structure to the circuit of Fig. 2, and its operation is similar. However, it has the advantage that SCR 137 in Fig. 2 has to sustain a much lower voltage than SCR 37 of Fig. 2.

In the circuit of Fig. 4, the transformer 155 is a nr.l step-down transformer, while the transformer 55 of Fig. 2 is an l.tti step-up transformer. Furthermore, while in transformer 55 of the circuit of Fig. 2, the winding direction of the primary winding is opposite with respect to the winding direction of the secondary winding, in the circuit of Fig. 4 both windings of transformer 155 are to the same direction. The second transformer, 199, is a 1:M3 step-down transformer in which the winding direction of the primary winding is opposite with respect to the direction of the secondary winding. The above arrangement is an example, and some variation can be made according to design needs.

In the circuit of Fig. 2, the SCR 37 has to be a high voltage SCR, as it must sustain the voltage of the primary winding of the transformer 55, stepping up by a factor of m. This may be a relatively expensive SCR. In the circuit of Fig. 4, the transformer 155 is a stepping down transformer having a winding ratio of τι-?:l. Therefore SCR 137 can be an SCR of a lower voltage. The circuit of Fig. 4, however, requires an additional, stepping up transformer 199 having a winding ratio of l: , and an additional diode 100. In this case the diode has to sustain a high voltage, however the cost of a high voltage diode is often less than the cost of a high voltage SCR.

The proces of the recovery of the energy that is returned from the load, and which is reversely accumulated in storage capacitor 7, is carried out at the beginning of the charging period, exactly in the same manner as in the circuit of Fig. 2, and therefore, this process will not be repeated here, for the sake of brevity.

The triggering of the SCR 137 by the comparator 156 through transformer 117 takes place essentially within the same timing as it takes place in the circuit of Fig. 2. Transformer 117 provides a buffer between comparator 156 and the high voltage of SCR 137, and protects it from that high voltage. When this triggering takes place, SCR 137 is forwardly biased, and therefore it turns ON. Turning ON SCR 137 causes a current to flow through the secondary winding in the the direction as shown by arrow 166, causing a voltage to spread over the secondary winding 155b, which in turn induces to the primary winding 155a in a direction to cause the voltage on the anode of SCR 106 to drop, thereby turning SCR 106 OFF, and terminating the charging current to the storage capacitor 107. The regulation of the energy remaining in the primary winding of transformer 155 is carried out by the current I22 flowing through the secondary winding of this transformer, in the direction of arrow 166. Current I22 is n.3 times amplified by the transformer 199, and therefore the current In in the secondary winding 199b of transformer 199 flows in the direction of arrow 177, as shown. Diode 100 enables the current to flow only in this direction.

As said, the invention shows that when a voltage regulator is used in the resonant charging circuit, it can provide not only energy regulation, but also recovery of the energy that is reflected from the load in the pulsed power generator of a type that is fed by said resonant charging circuit. Therefore, there is no need at all for any additional means for dealing with this reflected energy, such means being not only expensive and of large volume, but also significantly reducing the efficiency of the whole system. The circuits of Figs. 2 and 4 provide recovery of the energy that is reflected from the load, and regulation of the energy that remains occluded in the primary of the transformer (37 in Fig. 2, and 137 in Fig. 4). Moreover, these circuits enable accurate adjustment of the amount of power in the output pulses to the load, and assure that they all have the same energy, no matter how much energy was returned from the load in a previous period. All these targets are achieved by the compact circuits of the invention.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried into practice with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without departing from the spirit of the invention or exceeding the scope of the claims.

Claims

1. A method for recovering the energy that is reflected from a load, upon providing a pulse of power to it in a pulsed power generator, the said pulsed power generator having a storage capacitor, which is charged from a resonant charging circuit in forward polarity, the method being characterized by using a voltage regulator in said charging circuit for effecting a current flow carrying the charge accumulated in the said storage capacitor in reversed polarity due to said energy reflection, said current flowing through a DC power supply feeding said resonant charging circuit, back to said storage capacitor for charging it in forward polarity.

2. A method according to claim 1, further comprising using the said voltage regulator also for carrying out energy regulation, by returning the energy remaining in the inductive element at the output of said charging circuit back to the DC power supply, after termination of the charging current to the said storage capacitor.

3. A method according to claim 1, wherein the energy recovery takes place after providing a pulse of power by said pulsed power generator to the load, during subsequent charging of the storage capacitor of said pulsed power generator.

4. A method according to claim 1, wherein the said voltage regulator comprises at least one transformer having primary and secondary windings, and at least one switching component.

5. A method according to claim 4, wherein the said switching component is an SCR.

6. A method according to claim 4, wherein the resonant charging circuit comprises, in addition to said voltage regulator, a DC power supply for providing energy, and a second switching component for initiating and terminating charging of the storage capacitor of the pulsed power circuit.

7. A method for resonantly charging a storage capacitor of a pulsed power, comprising: a. Providing a DC power supply; b. Providing a transformer having primary and secondary windings, the primary winding of the transformer being connected to the DC power supply and forming a series resonant circuit with the said storage capacitor of the pulsed power; c. Providing a first switching component in series to the primary winding of the transformer; d. Providing a second switching component in series to the secondary winding of the transformer; e. Predefining a voltage level to which the storage capacitor should charge and providing means for continuously sensing the voltage level of the capacitor; f. Commencing a charging period by first turning ON the first switching component to effect current flow, that first recovers the energy previously reflected from the load, by transferring any charge accumulated in reversed polarity in the storage capacitor, through the DC power supply, the primary winding, and the first switching component back to the storage capacitor in forward polarity, and simultaneously charge the storage capacitor with the charge originating from the DC power supply; g. Providing a sensing unit for checking the voltage level of the storage capacitor; h. When the voltage level of the storage capacitor reaches the said predefined voltage level as checked by the said sensing unit, turning ON the second switching component, thereby to produce a voltage over the secondary winding, that is induced to the primary winding, thereby causing the first switching component to turn OFF, terminating the charging current to the storage capacitor. The current flow through the secondary winding further returns any energy remaining in the primary winding due to the termination of the charging current back to the DC power supply.

8. A method according to claim 7, wherein the first and second switching components are SCRs.

9. A method according to claim 7, wherein the first and second switching components are Thyratrons.

10. A method according to claim 7, wherein the transformer is a step-up transformer, wherein the secondary winding has m times windings in comparison to the number of windings in the primary winding, m is an integer greater than 1.

11. A circuit for resonantly charging the storage capacitor of a pulsed power, comprising:

a. A DC power supply; b. A first transformer having primary and secondary windings, a first end of the primary winding and a first end of the secondary winding being connected to the positive pole of the DC power supply; c. A first controlled switch connected between the second end of the primary winding and the storage capacitor, for enabling current flow from the DC power supply through the primary winding to the storage capacitor, or preventing the same; d. A second controlled switch connected between the second end of the secondary winding of the transformer and the negative pole of the DC power supply, for allowing or terminating current flow in the secondary winding of the transformer; and e. A control unit for activating the first switch, for sensing the voltage of the storage capacitor, and for activating the second switch when the voltage on the storage capacitor is above a predefined threshold level.

The said resonant charging circuit is characterized in that, when it is connected to a pulsed power, it effects recovery of the energy reflected from the load, and regulates the energy remained in its inductive component upon termination of its charging operation.

12. A circuit for resonantly charging the storage capacitor of a pulsed power according to claim 11, wherein the first and second controlled switches are SCRs.

13. A circuit for resonantly charging the storage capacitor of a pulsed power according to claim 11, wherein the winding ratio between the secondary winding and the primary winding of the first transformer is n-i.l, τiι being an integer larger than 1.

14. A circuit for resonantly charging the storage capacitor of a pulsed power according to claim 11, further comprising a diode, and a second transformer having a primary and secondary windings, a first end of the primary winding of the second transformer is connected to the first end of the secondary winding of the first transformer, and the second end of the second transformer is connected to the second switch, the first end of the secondary winding of the second transformer is connected to the negative pole of the DC power supply, the diode is connected to the positive pole of the DC power supply and to the second end of the secondary winding of the second transformer, thereby to allow current to flow in the direction from the secondary winding towards the positive pole of the DC power supply.

15. A circuit for resonantly charging the storage capacitor of a pulsed power according to claim 14, wherein the winding ratio between the primary and secondary windings of the first transformer is V.n∑, and between the primary and secondary windings of the second transformer is n3:l, n∑ and n.3 being integers larger than 1.

16. An apparatus for generating a high power pulse into a load, comprising:

- a pulsed power generator for providing a pulse of power into said load; and