| 摘要 |
PURPOSE:To facilitate soft start at the time of the start of a motor by a method wherein a circuit which integrates the number of rotations of a rotor is provided and the output of a power supply circuit is controlled by the output of the integrating circuit. CONSTITUTION:An output voltage which is determined by a threshold input at the time of the start of a motor is applied to the motor. When a rotor starts rotation, a phase reduction circuit detects the rotation and generates a phase detection signal (a). The phase detection signals are inputted to the clock input terminal of a counter IC1 and integrated and an output Q0 is outputted in accordance with the integrated value. The output Q0 is supplied to the base of a transistor Tr1 through a current limiting resistor R1 and a threshold voltage which has been determined by a variable resistor Vr1 and a resistor R9 is now determined by the variable resistor Vr1, the resistor R9 and a resistor R5 and becomes lower than the initial value. Therefore, the output voltage of a switching power supply becomes higher than the initial value and the rotation speed of the rotor is increased. In the same way, transistors Tr2, Tr3 and Tr4 are successively turned on and the threshold voltage is successively lowered, so that soft-start can be realized. |
