Patent ID: 6316756
Filing Date: 2001-11-13
Classification: H02M,H05B

Abstract:
A radio frequency (RF) power system for heating a workpiece, comprising:a circuit;a direct current (DC) voltage source that provides a DC voltage within a first predetermined range;an amplifier, coupled to said DC voltage source, to provide an alternating voltage to said circuit;a frequency controller, coupled to said amplifier, to control a frequency of said alternating voltage provided by said amplifier; anda power sensor being coupled to said circuit for providing a signal to said frequency controller, wherein said frequency controller controls said frequency of said alternating voltage based on said signal provided from said power sensor, and wherein said power sensor senses both forward and reflected power, and said signal represents a ratio of said reflected power to said forward power, whereinsaid frequency controller comprises a resonant frequency tracking means for tracking a resonant frequency of said circuit while the workpiece is being heated, thereby enabling said frequency controller to control said frequency of said alternating voltage so that said frequency of said alternating voltage tracks said resonant frequency of said circuit while the workpiece is being heated, wherein said resonant frequency tracking means uses said signal that represents a ratio of said reflected power to said forward power to track said resonant frequency of said circuit.