Magnetically tunable starting circuit for an electrodeless high intensity discharge lamp

A starting circuit for an electrodeless high intensity discharge lamp of the type having an excitation coil situated about an arc tube for exciting an arc discharge in an ionizable fill contained in said arc tube, comprising:

• a starting probe disposed proximate to said arc tube and establishing a parasitic capacitance between said excitation coil and said starting probe;
• a series resonant circuit for receiving a radio frequency signal from a radio frequency power supply and providing a resonant starting voltage to said starting probe of sufficient magnitude to initiate the arc discharge in said arc tube, said series resonant circuit including a resonant inductance coupled in series with a resonant capacitance, said resonant capacitance comprising said parasitic capacitance, said resonant inductance comprising an electrically variable inductance;
• said electrically variable inductance comprising a magnetic core of variable permeability having a main winding wound thereon coupled in series with said resonant capacitance, said magnetic core further having a bias winding wound thereon and being coupled to a bias circuit supply means for supplying bias current to said bias winding in order to vary said resonant inductance and thereby tune said starting circuit.