Abstract: A start-up circuit for a sensorless, brushless DC motor modifies a conventional start-up circuit to include an intermittently-accelerated-rate clock generator for supplying a clock signal intermittently accelerated in rate to a shift register that is connected as a ring counter for selectively generating three-phase commutation signals during start-up and six-phase phase commutation signals during running. The intermittently-accelerated-rate clock generator facilitates the start-up circuit increasing the magnitude of a back electromotive force by adjusting the rate of a starting clock during start-up of the motor, so as to be capable of both a normal start-up with a normal-rate clock signal and an accelerating start-up with an accelerated-rate clock signal. This permits a stable and rapid start-up without need for a microprocessor or complicated circuitry.