Patent ID: 7323832

Claim:
A control circuit for an inverter for driving a fluorescent lamp, comprising: an error amplifier which amplifies an error between an externally-input analog dimming control voltage for adjustment of a brightness of the fluorescent lamp driven and a detection voltage that depends on a current that flows in the secondary coil of a transformer of the inverter; a first triangular wave signal generator which outputs a first triangular wave signal; a pulse width modulation comparator which compares an error voltage output from the error amplifier with the first triangular wave signal output from the first triangular wave signal generator; a second triangular wave signal generator which generates a second triangular wave signal at a frequency lower than that of the first triangular wave signal; a comparator for burst dimming which compares an externally-input burst dimming control voltage with the second triangular wave signal output from a second triangular wave signal generator; and a logic controller which subjects a current through the primary coil of the transformer to switching control in accordance with the pulse width modulation signal output from the pulse width modulation comparator, and refers to an output signal of the comparator for burst dimming, so as to terminate the switching control while the burst dimming control voltage is lower than the second triangular wave signal, wherein a semiconductor substrate on which the control circuit is integrated is partitioned into at least two areas by a fixed potential wiring, the first triangular wave signal generator being placed in one of the areas, and the second triangular wave signal generator and the comparator for burst dimming being placed in the other area.