Evaluation of MOS-FET RDSon resistance for current measurement purposes in power converter´s applications

This paper presents metal oxide semiconductor field effect transistor (MOS-FET) R_DSon resistance evaluation in order to perform the MOS-FET current-measurement. For calculation of R_DSon the thermal model of the MOS-FET is explored. For accurate R_DSon evaluation in the real time the voltage U_DSon is measured during the switch-on transistor operation mode. This measurement is synchronized by PWM triggering in order to measure the average voltage value and consequently the average current during the converter sampling time period. This measurement approach is verified by real-time measurement during the operation of the DC-DC step-up converter. The program algorithm is performed on 32-bit ARM M4 MCU, STM32F407.