HIGH RESOLUTION PULSE WIDTH MODULATION (PWM) FREQUENCY CONTROL USING A TUNABLE OSCILLATOR

摘要

A fluorescent lamp light intensity dimming control generates a pulse width modulation (PWM) signal at about a fifty percent duty cycle and has very fine frequency change granularity to allow precise and smooth light dimming capabilities. Intermediate PWM signal frequencies between the frequencies that are normally generated from values in a period register of the PWM generator are provided with a variable frequency clock source to the PWM generator. Selection of each frequency from the plurality of frequencies available from the variable frequency clock source may be determined from a value stored in a variable frequency clock register, A microcontroller may be used to select appropriate frequencies for dimming control of the fluorescent lamp from the variable frequency clock source, and the period and duty cycle values used in generating the PWM signal at about a fifty percent duty cycle.