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Class-E converters enable high-efficiency switching at high switching frequencies and thus fulfil the fundamental preconditions for miniaturization. This, however, must be paid for with a relatively high voltage stress across the switch causing problems when the converter is operated from the mains. A 500-kHz 21-W electronic lamp ballast for 220-V mains is presented. A cascaded bipolar MOS (BIMOS) incorporating a TV deflection transistor combines rapid switching with the required excessive voltage capability for mains drive. An excellent efficiency of 93 percent could be achieved.