A transformer (14) has a primary winding (16) connected in series with a direct current source (12), a solid state switch (Q1) and a current sensing resistor (R11). A reactive element (C2) is coupled to the primary winding to form a resonant circuit. A high voltage for exciting a gaseous discharge device (19) is produced across a first secondary winding (18) of the transformer (14). A second resistor (R1) couples a terminal of the direct current source (12) to one plate of a storage capacitor (C7) that has another plate connected to a second terminal of the direct current source. The one plate of the storage capacitor (C7) also is connected to a second secondary winding (20) of the transformer (14). The control circuitry (22) for the power supply (10) is biased by voltage stored across the storage capacitor (C7). A circuit branch applies a bias potential to a control electrode of the solid state switch (Q1) to render the switch conductive, and has a delay element (C4, R4) which prevents the solid state switch (Q1) from becoming conductive until a sufficient voltage level exists across the storage capacitor (C7) to bias the control circuitry into operation. A switch circuit (Q2) turns off the solid state switch (Q1) either when the voltage across the first resistor (R11) exceeds a given level or when the voltage across the second secondary winding (20) exceeds a predefined magnitude.
