| 摘要 |
PURPOSE:To reduce the number of components and to reduce the size of a step motor driver by constituting a switching element of a FET and utilizing voltage drop across the FET for detection of motor load current. CONSTITUTION:When a controller 100 provides a High level driving signal DRV to turn a FET 32A ON and a voltage higher than a rated component voltage is applied on a winding 1A, current 1m flowing through the winding 1A rises abruptly. When the motor load current Im rises sufficiently and the voltage drop Vf across the FET 32A exceeds a refere voltage Vref., output Vo of a current detecting circuit 25 makes a transition from Low to High level. A chopper circuit 21 receives a feedback signal Vo and turns the FET 32A OFF. Consequently, voltage drop Vf across the FET 32A lowers below the reference voltage Vref. and the output Vo of the current detecting circuit 25 makes a transition from High to Low thus turning the FET 32A ON through the chopper circuit 21. |
