The invention relates to a drive device for an electric motor, in particular for a brushless DC motor in an electrical tool, which is powered by a rechargeable battery. The drive device has at least one power semiconductor, in particular for controllable application of an electrical voltage to the electric...http://www.google.co.uk/patents/US7359628?utm_source=gb-gplus-sharePatent US7359628 - Control device for an electric motor
