MOTOR DRIVE CIRCUIT AND WINDING CURRENT SENSING

摘要

A drive circuit and method for sensing motor winding current. An FET drive transistor (301) has its ON resistance periodically increased to about five times the normal ON resistance for short sensing intervals during motor drive. An analog-to-digital converter senses the voltage across this FET during the sensing intervals. The resulting digital signal is used to calculate motor current. The time at high ON resistance is much less than the time at normal. The ON resistance can be changed using two FETs (301, 302) or one FET with gate fingers over differing parts of the channel region.