in a first preferred embodiment shown in fig2 , a circuit which may be used to provide resonant striking by means of resonating a capacitor and inductor to multiply a stimulating voltage is shown . a stimulating voltage 6 is provided by switching means 4 and 5 which are controlled to turn on and off in opposition and in response to gate signals provided by controller circuit 1 . the stimulating voltage 6 is resultant of the alternate switching of the node of switching means 4 and 5 and inductor 7 alternately connecting the inductor 7 to a first positive dc voltage rail 2 and a second negative dc voltage rail 3 . the controller circuit 1 is designed or programmed to operate the switching means 4 and 5 at a frequency or several frequencies chosen to coincide with the resonant frequency of the inductor 7 and capacitor 8 . in this case , a secondary winding 7 a is provided which is connected in one instance to the mid node of the serially connected capacitors 11 and 12 and in the other instance to the junction of the two serially connected diodes 13 and 14 . additionally , a second pair of diodes ( not shown ) may be utilized in parallel with capacitors 11 and 12 . the voltage in both windings of inductor 7 is substantially defined by the turns ratio of the windings . during the high frequency operation of the switching means the mid node of capacitors 11 and 12 remains substantially at the mid voltage between the + ve dc rail 2 and the − ve dc rail 3 . high frequency voltage 9 intended for striking the lamp 10 is transformed by the turns ratio of the two windings on the inductor 7 so that a proportional voltage appears on the secondary winding 7 a of inductor 7 . the turns ratio of the inductor 7 is chosen such that at the desired peak lamp striking voltage , the peak secondary winding 7 a voltage is equal to half of the dc rail voltage . since one end of the secondary winding 7 a is held at mid rail voltage at the mid node of the capacitors 11 and 12 , the voltage at the opposing end of the secondary winding will forward bias either one of the diodes 13 and 14 if the peak secondary voltage exceeds the half rail voltage . by these means , excess voltage is prevented from occurring in the lamp striking circuit by diverting energy from the resonant circuit if the voltage exceeds the desired value . this energy is substantially recovered into the dc voltage rails such that the limiting of voltage does not result in increased losses . in fig3 , a modified circuit is shown which uses a primary low pass filter comprising inductor 15 and capacitor 16 . this additional low pass filter is used to reduce the high frequency current ripple applied to the lamp during normal low frequency square wave operation of the ballast circuit . the operation of the striking voltage control circuit is as described in reference to fig2 . in fig4 , a modified circuit is shown which uses two buck converters / primary low pass filters each comprising an inductor 15 or 17 and capacitor 16 . this additional low pass filter is used to reduce the high frequency current ripple applied to the lamp during normal low frequency square wave operation of the ballast circuit . the operation of the striking voltage control circuit is as described in reference to fig2 . other combinations and interconnections of inductors , capacitors , switching means and rectifying elements are possible and the arrangements shown here are in no way intended to limit the scope of the invention . in a second preferred embodiment shown in fig5 , a circuit which may be used to provide resonant striking by means of resonating a capacitor and inductor to multiply a stimulating voltage is shown . a stimulating voltage 6 is provided by switching means 4 and 5 which are controlled to turn off and on in opposition in response to gate signals provided by controller circuit 1 . the stimulating voltage 6 is resultant of the alternate switching of the node of switching means 4 and 5 and inductor 7 alternately connecting the inductor 7 to a first positive dc voltage rail 2 and a second negative dc voltage rail 3 . the controller circuit 1 is designed or programmed to operate the switching means 4 and 5 at a frequency or several frequencies chosen to coincide with the resonant frequency of the inductor 7 and capacitor 8 . in this case , a secondary winding 7 a is provided which is connected in one instance to the mid node of the serially connected capacitors 11 and 12 and in the other instance to the node of the two serially connected diodes 13 and 14 and lamp 10 . the voltage in both windings of inductor 7 is substantially defined by the turns ratio of the windings . during the high frequency operation of the switching means , the mid node of capacitors 11 and 12 remains substantially at the mid voltage between the + ve dc rail 2 and the − ve dc rail 3 . high frequency voltage 9 intended for striking the lamp 10 is transformed by the turns ratio of the two windings on the inductor 7 so that a proportional voltage appears on the secondary winding 7 a of inductor 7 . the turns ratio of the inductor 7 is chosen such that at the desired peak lamp striking voltage , the peak secondary winding 7 a voltage is equal to half of the dc rail voltage . since one end of the secondary winding 7 a is held at mid rail voltage at the mid node of the capacitors 11 and 12 , the voltage at the opposing end of the secondary winding will forward bias either one of the diodes 13 and 14 if the peak secondary voltage exceeds the half rail voltage . by these means , excess voltage is prevented from occurring in the lamp striking circuit by diverting energy from the resonant circuit if the voltage exceeds the desired value . this energy is substantially recovered into the dc voltage rails such that the limiting of voltage does not result in increased losses . in fig6 , a modified circuit is shown which uses a primary low pass filter comprising inductor 15 and capacitor 16 . this additional low pass filter is used to reduce the high frequency current ripple applied to the lamp during normal low frequency square wave operation . the operation of the striking voltage control circuit is as described in reference to fig5 . in fig7 , a modified circuit is shown which uses two buck converters / primary low pass filters each comprising an inductor 15 or 17 and capacitor 16 . this additional low pass filter is used to reduce the high frequency current ripple applied to the lamp during normal low frequency square wave operation . the operation of the striking voltage control circuit is as described in reference to fig5 . other combinations , interconnections and topologies of inductors , capacitors , switching means and rectifying elements are possible and the arrangements shown here are in no way intended to limit the scope of the invention . in fig8 , a partial block diagram of a typical high intensity discharge lamp ballast is shown . mains terminals connect the mains input to an electromagnetic interference filter 29 which comprises inductive and capacitive elements such as to allow the reduction of conducted electrical interference generated within the ballast to be suppressed according to standards and regulations in force . 28 is a bridge rectifier circuit typically comprising four diodes which act upon the incoming mains ac voltage to rectify the voltage to a dc voltage . 26 is a power factor controller and power supply circuit which boosts the half sine dc voltage from the output of the rectifier circuit to a dc voltage suitable for the ballast output circuit . this dc voltage appears on dc voltage rails 2 and 3 . the capacitors 11 and 12 serve to smooth the voltage and store energy during the mains voltage zero crossing events . a third voltage rail is provided which is intended to supply the low voltage electronics circuits of the ballast at typically 15v dc . 25 is a micro controller or other control circuit which oversees the operation of the ballast and controls and monitors the striking of the lamp and operation of the lamp . typically , there are two discrete modes of operation of the lamp . in a first discrete mode of operation , the ballast output switching means 4 and 5 are alternately switched on and off at one or several different high frequencies , typically although not exclusively , in the range 40 khz to 400 khz by the action of the microcontroller 25 in response to a stored program , in order to stimulate resonance in the l c resonant circuit comprising inductor 7 and capacitor 8 and thereby generate sufficient voltage to breakdown or ionise the gas filling of the arc tube in a connected lamp 10 . once the lamp has been broken down by the generated high voltage , the arc in the lamp &# 39 ; s arc tube is maintained by the high frequency voltage applied to the inductor and capacitor network comprising inductors 15 , 17 and 7 and the capacitors 16 and 8 . lamp current is returned to the voltage rails 2 and 3 via inductor winding 7 a , current monitoring device 20 and capacitors 11 and 12 . the impedance of the various reactive components 15 , 17 , 7 , 16 and 8 and the operating frequency of the switching means 4 and 5 serve to control the current in the lamp during this first discrete mode of operation . in a second discrete mode of operation , ballast output switching means 4 and 5 are alternately switched on and off at low frequency typically , although not exclusively , in the range 20 hz to 400 hz by the action of microcontroller 25 in response to a stored program . during each low frequency half cycle of operation relating to the programmed on time of each switching means , the current in the lamp circuit is monitored by current monitoring device 20 and a current proportional voltage signal is compared with a reference voltage signal at the node of resistors 23 and 24 . if the current proportional voltage signal exceeds the reference voltage signal , the comparator 22 applies a shutdown signal to the switching means driver 30 . this shutdown signal terminates or interrupts the on time of the active switching mean , switching the switching means off , until the lamp current proportional voltage signal falls below the reference voltage value at the node of resistors 23 and 24 causing the comparator 22 to remove the shutdown signal from the input of the switching means driver 30 which causes the driver to turn on the active switching means once again . this turning on and off of the switching means in response to the lamp current signal causes the lamp current to oscillate around the value set by the reference voltage signal at the node of resistors 23 and 24 . the reference voltage value at the node of resistors 23 and 24 is also responsive to the output of lamp current and voltage multiplier and integrator 21 such that once the product of lamp voltage and current exceeds the lamp power desired the output of the multiplier and integrator 21 ramps down reducing the voltage reference signal at the node of resistors 23 and 24 thus reducing the lamp current responsive voltage signal and therefore the value of lamp current at which the active switching means is switched off , until the desired lamp power is achieved and controlled in response to the multiplier and integrator 21 . in the following , opposite low frequency half cycle relating to the programmed on time of each switching means , the current in the lamp circuit is monitored by current monitoring device 20 and a current proportional voltage signal is compared with a reference voltage signal at the node of resistors 23 and 24 . if the current proportional voltage signal , exceeds the reference voltage signal the comparator 22 applies a shutdown signal to the switching means driver 30 . this shutdown signal terminates or interrupts the on time of the active switching mean , switching the switching means off , until the lamp current proportional voltage signal falls below the reference voltage value at the node of resistors 23 and 24 causing the comparator 22 to remove the shutdown signal from the input of the switching means driver 30 which causes the driver to turn on the active switching means once again . this turning on and off of the switching means in response to the lamp current signal causes the lamp current to oscillate around the value set by the reference voltage signal at the node of resistors 23 and 24 . the reference voltage value at the node of resistors 23 and 24 is also responsive to the output of lamp current and voltage multiplier and integrator 21 such that once the product of lamp voltage and current exceeds the lamp power desired the output of the multiplier and integrator 21 ramps down reducing the voltage reference signal at the node of resistors 23 and 24 thus reducing the lamp current responsive voltage signal and therefore the value of lamp current at which the active switching means is switched off , until the desired lamp power is achieved and controlled in response to the multiplier and integrator 21 . thus , a low frequency square wave of alternating current is applied to the lamp with a small , superimposed , high frequency ripple current which is limited and bypassed by the various inductors and capacitors in the connected ballast circuit . other combinations , interconnections and topologies of inductors , capacitors , switching means and rectifying elements are possible and the arrangements shown here are in no way intended to limit the scope of the invention . other ballasting circuits are possible using , for instance a full bridge ballast output circuit shown in fig9 with 4 switching elements , e . g . transistors 4 , 5 , 4 ′ and 5 ′ where the operation of 1 or 2 or more than 2 switching means is under the control of a control means . as may be seen in this fig9 , a second pair of diodes 13 ′ and 14 ′ are coupled to the opposite end of secondary winding 7 a . in this embodiment , no capacitors ( similar to capacitors 11 , 12 in fig2 ) are used to return the lamp current to the rails 2 , 3 . as such , there is no capacitor mid - point to which to return a second winding 7 a . in this absence the second pair of diodes 13 ′ and 14 ′ are utilized . other ballasting means are possible where the lamp is operated at high frequency continuously after ionisation of the gas filling of the arc tube and no low frequency square wave mode of operation follows . the scope of the invention is not limited to ballasting means , embodiments and methodologies described herein . the scope of the invention is not limited to ballasting of high intensity discharge lamps . all references , including publications , patent applications , and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein . for purposes of this disclosure , the term “ coupled ” means the mechanical or electrical joining of two components directly or indirectly to one another . such joining may be stationary in nature or moveable in nature . such joining may be achieved with the two components and any additional intermediate members being integrally formed as a single unitary body with one another or the two components and any such additional member being attached to one another . such adjoining may be permanent in nature or alternatively be removable or releasable in nature . the use of the terms “ a ” and “ an ” and “ the ” and similar referents in the context of describing the invention ( especially in the context of the following claims ) is to be construed to cover both the singular and the plural , unless otherwise indicated herein or clearly contradicted by context . the terms “ comprising ,” “ having ,” “ including ,” and “ containing ” are to be construed as open - ended terms ( i . e ., meaning “ including , but not limited to ,”) unless otherwise noted . recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range , unless otherwise indicated herein , and each separate value is incorporated into the specification as if it were individually recited herein . all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context . the use of any and all examples , or exemplary language ( e . g ., “ such as ”) provided herein , is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed . no language in the specification should be construed as indicating any non - claimed element as essential to the practice of the invention . preferred embodiments of this invention are described herein , including the best mode known to the inventors for carrying out the invention . variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description . the inventors expect skilled artisans to employ such variations as appropriate , and the inventors intend for the invention to be practiced otherwise than as specifically described herein . accordingly , this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law . moreover , any combination of the above - described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context .