Patent ID: 6943502

Claim:
An electronic ballast for a discharge lamp comprising: an AC-DC converter adapted to be connected to receive a source AC voltage and convert the source AC voltage into a DC voltage; an inverter providing a high frequency output voltage from said DC voltage for operating the discharge lamp, said inverter comprising at least one switching element, a control circuit for said switching element, and an output transformer adapted to be connected to said discharge lamp, said control circuit activating said switching element to repetitively interrupt said DC voltage to provide the high frequency output voltage to said discharge lamp through said output transformer; a single circuit board mounting thereon electric parts which constitute said converter and said inverter; a tubular casing accommodating therein said circuit board; and a dielectric sheet interposed between said circuit board and said casing for insulation of said circuit board and said electric parts from said casing, wherein said ballast includes a plurality of chip components forming a detection circuit for detection of a condition of said discharge lamp, said circuit board mounts said output transformer on its top surface and mounting said chip components on its bottom surface at a location immediately opposite of said output transformer, and said detection circuit is provided to detect an operating condition of said discharge lamp and includes a resistor network composed of chip resistors for dividing the output voltage of said inverter into a detection voltage which is fed to said control circuit for control of said inverter.