Patent ID: 7982405

Claim:
An igniter circuit for an HID lamp, the igniter circuit comprising: a DC input for coupling to a source of DC voltage, an output for coupling to the HID lamp, a resonant ignition circuit including: an oscillator operating at a self-oscillating resonant frequency coupled to said DC input for producing successive bursts of voltage having a frequency equal to the resonant frequency and having an amplitude that increases with time and for feeding said bursts of voltage across the output of the igniter until an HID lamp coupled thereto reaches breakdown, so as to cause the lamp impedance to fall to a low value and load the resonant circuit so that its Q factor falls significantly and stops resonating thereby stopping the oscillator from oscillating; a current source having a low frequency component and high frequency component; a transformer comprising a first coil and a second coil connected in series with each other, the second coil being connected in series with the lamp, the first coil being part of the oscillator prior to ignition and, after ignition, serving to block the high frequency component so as to pass the low frequency component to the lamp; and a first capacitor having a first end coupled to the first coil and having a second end coupled to both the lamp and to a first end of a second capacitor having a second end connected to ground (GND), said first capacitor and second capacitor being configured for passing the high frequency component from the current source to GND.