| 摘要 |
PURPOSE:To reduce power loss by providing a PWM control circuit and a circuit for switching the control based on an external command signal in addition to a linear control circuit. CONSTITUTION:A motor driving current feedback loop comprising a motor current detecting circuit 9, an operational amplifier 10, a comparator 11, a triangular wave generating circuit 12, an output stage driving circuit 6, and the like can select between linear control and PWM control through a linear/ PWM switching circuit 17. The linear/PWM switching circuit 17 selects a low noise linear control for a read mode in which data are read out from a disc based on a read mode signal 18 otherwise selects a highly efficient PWM control by switching the switches 15, 16. In other words, linear control may be employed only under read mode where the noise level may cause a trouble. According to the constitution, average power loss can be lowered. |
