Patent ID: 7202617
Filing Date: 2007-04-10
Classification: H02P

Abstract:
1. A circuit for controlling a brushless permanent magnet motor comprising: a plurality of windings, each of the windings having a first end connected at a common node and each of the windings having a second end connectable directly to supply voltages by switches, the second end connected to an upper supply voltage or connected to a lower supply voltage or disconnected from the supply voltages; blocking circuitry connectable with the second ends, the blocking circuitry producing a blocked voltage, the blocked Voltage representing a voltage across an associated winding; a comparator receiving the blocked voltage on one input and a reference voltage on another input, the comparator result indicating polarity of a back emf voltage in the associated winding, wherein one input of the comparator is connected via a single direction switch to the second end of a winding and said single direction switch has an anode connected to one input of the comparator and a cathode to receive voltage signal from the second end of a winding; and a latch providing control signals for the circuit, an input of the latch enabled by an enable signal, an output of the latch comprising a back emf voltage detection signal, wherein the blocking circuitry and the comparator are duplicated for each of the windings.