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In many applications, efficiency and service quality are improved with an appropriate power control. This paper focuses on a power-measurement method designed to deal with medium/high frequencies (tens to hundreds of kilohertz). It requires a previous knowledge of application and exploits some characteristics of the power topology and control, in this case, a full-bridge series resonant inverter. It is a new method based on a low-cost analog circuit that integrates the high-frequency load current, in order to reduce the computational complexity of measuring power. Harmonic analysis is carried out to determine the A/D converter requirements, and the theoretical results are verified using a digital-signal-processor (DSP)-based experimental setup. The power measurement may be implemented on the microcontroller or low-performance DSP used to control the power stage, with an error below of 2% independent of the load and mains variations.
Date of Publication: Feb. 2009