Motor control circuit for a power tool

摘要

A motor control module for a power tool includes a controller and a triac for controlling current to the given tool motor. The module includes a circuit within the controller for implementing a plurality of control methodologies related to synchronizing the module to the AC input signal, estimating average current flowing through the triac, compensating for amplifier offset to improve accuracy of current measurements in the module, and providing speed measurement and control for the tool motor using principles of hysteresis in a comparator of the controller. Additionally, the controller is configured to calibrate an oscillation calibration register therein.