A High-precision Digital Measurement System Design based on PSR

Abstract

In engineering practice, a constant voltage output control system of synchronous rectifier primary side regulator (PSR) flyback converter is proposed to overcome the sampling defect of the existing digital approximation double line sampling scheme for primary side control synchronous rectifier structure. Regardless of the slope of the sampling waveform and the knee point, the single-output DAC midpoint sampling can achieve high sampling accuracy and good knee point following effect. At the same time, the neutral-point sampling error of the single-output DAC is analyzed, and a sampling compensation scheme which can simultaneously act in continuous current mode (CCM) and discontinuous current mode (DCM) is designed to further correct the sampling voltage obtained by neutral-point sampling, so as to compensate the voltage error of neutral-point sampling. Thus, the output voltage can be accurately constant in DCM and CCM.