Apparatus for producing high voltage pulses by capacitor discharge

Claim 1

Apparatus for generating a high voltage output signal having a limited duration, said apparatus comprising: a network of capacitors including a plurality of capacitors; charging means for charging each of said capacitors to a predetermined value; a voltage step-up transformer having at least one primary winding, a core, and at least one secondary winding; switch means for serially discharging a predetermined number of said capacitors through said at least one primary winding so as to generate a high voltage output signal in said at least one secondary winding, said switch means controlling the duration of said high voltage output signal by controlling the length of time during which said network of capacitors discharges through said at least one primary winding, said switch means discharging said network of capacitors at a rate which is independent of the rate at which said charging means charges said network of capacitors; means for disconnecting said charging means from said network of capacitors prior to the instant at which said switch means begins discharging said predetermined number of capacitors.

Claim 19

An apparatus for generating high voltage pulses by capacitor discharge, comprising a plurality of capacitors, means for charging up each capacitor, a voltage step-up transformer having at least one primary winding, a core and at least one secondary winding, switching means selectively operable to at least partly discharge the capacitors sequentially through said at least one primary winding in such a manner as to induce an alternating magnetic field in the core and a high alternating voltage in said at least one secondary winding, and rectifier means to rectify the high alternating voltage from the secondary winding; filter means, comprising at least one smoothing capacitor, to smooth the output from the apparatus; selectively operable means to control the number of capacitors discharged and hence to control the total energy of the output; means for selectively varying the voltage step-up ratio of the voltage step-up transformer by variation of the number of turns of the primary winding through which each of said plurality of capacitors is discharged; a further capacitor and means connecting said further capacitor to said primary winding to cause said further capacitor to impress a relatively low slowly decaying voltage across said at least one primary winding of the voltage step-up transformer to produce an initial flux in the core opposite in polarity to that to be produced by the discharge of the first one of said plurality of capacitors in the sequence; and means for pre-selecting one of said plurality of capacitors to always be the first to discharge in the sequence, wherein the first capacitor to discharge in the sequence of said plurality of capacitors has a different capacitance to that of each of at least a last group of said capacitors to discharge; wherein the first capacitor to discharge in the sequence of said plurality of capacitors is arranged to discharge into a different number of primary winding turns than each of at least the last group of said capacitors to discharge.

Claim 20

An apparatus for generating high voltage pulses by capacitor discharge, comprising a plurality of capacitors, means for charging up each capacitor, a voltage step-up transformer having at least one primary winding, a core and at least one secondary winding, switching means selectively operable to at least partly discharge the capacitors sequentially through said at least one primary winding in such a manner as to induce an alternating magnetic field in the core and a high alternating voltage in said at least one secondary winding, and rectifier means to rectify the high alternating voltage from the secondary winding; filter means, comprising at least one smoothing capacitor, to smooth the output from the apparatus; selectively operable means to control the number of capacitors discharged and hence to control the total energy of the output; means for selectively varying the voltage step-up ratio of the voltage step-up transformer by variation of the number of turns of the primary winding through which each of said plurality of capacitors is discharged; a further capacitor and means connecting said further capacitor to said primary winding to cause said further capacitor to impress a relatively low slowly decaying voltage across said at least one primary winding of the voltage step-up transformer to produce an initial flux in the core opposite in polarity to that to be produced by the discharge of the first one of said plurality of capacitors in the sequence; and means for pre-selecting one of said plurality of capacitors to always be the first to discharge in the sequence, wherein the first capacitor to discharge in the sequence of said plurality of capacitors has a different capacitance to that of each of at least a last group of said capacitors to discharge; wherein the first capacitor to discharge in the sequence of said plurality of capacitors is arranged to discharge into a different number of primary winding turns than each of at least the last group of said capacitors to discharge.