PURPOSE: To make the prevention of increase of a voltage between both terminals of a switching element possible by a method wherein the rotating direction of a DC motor(DM) is detected and when the detected direction is the reverse direction to a predetermined rotating direction, an excitation control means is controlled by a rotating direction switching means so that the switching order of the switching element becomes reverse to a predetermined exciting order.

CONSTITUTION: When an automatic door, driven by a DC motor(DM) 32, is operated by an external force such as an input and the like under the stopping condition of the DM 32, an electromotive force, reverse to the case of rotation of forward direction, is generated in coils 33-35. In this case, a rotating direction detecting circuit 59 detects the rotation of reverse direction of the DM 32 and outputs a H signal corresponding to the rotation of reverse direction. When a brake control signal BK is L, a direction control signal RD is intercepted by a buffer 55. The signal of an XOR circuit 53 is outputted with a signal level as it is under a condition that a buffer 57 is in excited condition. In this case, the H signal, showing the rotating condition of reverse direction of the DC motor 32, is inputted into a rotation control unit 50 whereby the same unit 50 switches the exciting order of transistors 39, 41, 43 into an order reverse to the case of forward direction.