A synchronized ballast for a discharge lamp having an increased dimming range. The ballast includes semiconductor switches coupled to a generator to receive a high frequency signal. A variable pulse width modulator includes a one-shot multivibrator for generating a pulsed signal for interrupting conduction...http://www.google.co.uk/patents/US4998046?utm_source=gb-gplus-sharePatent US4998046 - Synchronized lamp ballast with dimming
