| 摘要 |
PURPOSE:To improve the drive efficiency of a DC motor by supplying the prescribed current of a motor drive current to a resistor which has a resistance value equal to the prescribed times of an internal resistance of the motor, and using as a reference voltage the sum of the voltage of the resistor and the voltage of a constant-voltage power source. CONSTITUTION:A differential amplifier IC2 outputs a differential voltage Vb between a voltage Vm between terminals of a DC motor 21 and a reference voltage Va, a level comparator IC3 compares a triangular wave voltage signal Vc with the voltage Vb at the level, and supplies a pulse width control signal Vd through a transistor drive circuit 25 to a switching transistor Q3. A 1/K current detector 26 detects the current of 1/K of the motor drive current Im when the transistor Q3 is ON, and supplies it to a resistor Rt which has the resistance value of K times of the resistor ra of the motor 21 at the ON and OFF times. The sum of the voltage Vr of the resistor Rt and the voltage Vref of the constant-voltage source is used as a reference voltage Va. |
