Ignitor for high intensity discharge lamps

An electronic ballast for igniting and operating a high intensity discharge lamp, comprising:

• a DC power supply having output nodes;
• a commutator having input nodes coupled to the output nodes of the DC power supply and having output nodes;
• a gapped transformer having a primary winding and at least one secondary winding;
• an ignition secondary circuit comprising the secondary winding of the gapped transformer, a first capacitor coupled in parallel with the secondary winding of the gapped transformer, and first and second lamp connection nodes coupled in series with the secondary winding of the gapped transformer between the output nodes of the commutator;
• and
• an ignition primary circuit comprising an inductor, the primary of the gapped transformer, a voltage-dependent breakover element;
• and a second capacitor coupled in series between the output nodes of the DC power supply, the ignition primary circuit further having a resistor coupled in parallel with the second capacitor.

A method of igniting a high intensity discharge lamp having a predetermined ignition pulse specification and a predetermined maximum operating load current, comprising:

• applying a voltage pulse to a primary winding of a transformer to produce a high voltage pulse on a secondary winding thereof;
• shaping the high voltage pulse with a first capacitor connected in parallel with the secondary winding of the transformer to create an ignition pulse in compliance with the predetermined ignition pulse specification of the high intensity discharge lamp;
• applying the ignition pulse to the high intensity discharge lamp to start the lamp;
• and
• furnishing the predetermined maximum operating load current to the lamp through the secondary winding of the transformer without causing the transformer to saturate.