ROTATING SPEED COTROLLING CIRCUIT

PURPOSE:To obtain a rotating speed control circuit which is not affected by the variations in a load and environmental conditions by composing a speed feedback circuit of a rotating speed loop of a rotating speed detector, a dither signal generator, an adder, a voltage comparator and a compensator. CONSTITUTION:A dither signal generator 4 generates a sawtooth wave or a sinusoidal wave having a dasic frequency of twice or more of the response of a speed control loop. The output of a rotating speed detector 3 and the output of the generator 4 are added by an adder 5, and applied to a voltage comparator 6. The comparator 6 compares the output voltage of the adder 5 with a reference voltage (a). The compared output suppresses the frequency component of high band and is supplied through a compensator 7 to a drive amplifier 1.