Abstract: An electronic power supply device for driving a D.C. commutatorless motor utilizes a plurality of driving coils for supplying power to the motor and at least one control coil, magnetically interconnected with the driving coils, to generate a control signal in response to operation of the motor such that a power transistor, having an output connected to the driving coils, and an input controlled by the at least one control coil to provide the driving current to the driving coils. A Zener diode having a nominal breakdown voltage lower than the breakdown voltage of the power transistor is interconnected therewith.In modifications of the power supply device a flip-flop circuit, controlled by a control signal generated by the at least one control coil, controls the commutation of the motor by controlling the conduction of the power transistor.