Braking delay circuit for computer hard disc, until heads are parked

摘要

The braking delay controller has a comparator (4) and a counter (6). The circuit counts the number of zero crossings of the back EMF of the motor. When a predetermined count is reached the braking action is initiated. The comparator (4) compares the back EMF against a reference potential (Vref), and delivers a count signal (SC) to the counter. The counter delivers a signal (SB) to brake the motor. The signal is delivered to the module (2) which controls the motor. The counter is initiated by a signal requesting braking, or an error condition that removes the supply from the disc drive motor.