A low visual noise, jitterized pulse width modulation brightness control circuit
is provided. The circuit uses a brightness control signal generating unit to receive
a brightness adjusting signal and to generate a brightness control signal in response
to the brightness adjusting signal. The brightness control pulse signal has a duty
cycle or frequency varying in a predetermined range. An inverter coupled to the
brightness control signal generating unit drives the fluorescent lamp in response
to the brightness control pulse signal to reduce the visual interference due to
the adjustment of the current beam density.
