Patent ID: 8351480
Filing Date: 2013-01-08
Classification: H01S,H03K

Abstract:
1. A pulse width modulation method, for controlling the output of an RF power supply for a gas discharge laser, comprising: delivering a train of digital pulses having a predetermined number of pulses therein to the RF power supply, each pulse in the train having an incrementally variable duration; arranging the power supply to deliver a train of RF pulses corresponding in number and duration to the train of digital pulses received, the train of RF pulses having an average power dependent on the duration of the RF pulse train and an aggregate duration of pulses in the train; and incrementally varying the duration of one or more, but less than all, of the digital pulses in the train thereof to selectively vary the average power in the corresponding RF pulse train wherein the duration of the digital pulses is controlled by pulses delivered by a digital clock having a clock-cycle period, and wherein the variation of the duration of individual pulses is a multiple of one clock cycle period.