| 摘要 |
<P>PROBLEM TO BE SOLVED: To reduce the generation of heat from a switching element when excess current flows in a motor and certainly start up the motor by a circuit having a simple and low-cost structure. <P>SOLUTION: A driving circuit of a brushless DC motor includes a group of switching elements 3 and 4 which are connected between power supplies 1 and 2 for driving a motor and a motor coil 5 and switches the conduction state of the motor coil; a current detecting section 11 for detecting a value of current in the motor coil; and a control circuit 7 which turns the group of switching elements into a non-conducting state when it receives an excess current detection signal which is issued when the current value detected by the current detecting section exceeds a predetermined value. A non-conducting time period until the group of switching elements turned into a non-conducting state after excess current detection is turned into a conducting state again is made different at the start-up of the motor and at a predetermined time after the start-up of the motor such that the non-conducting time period at the start-up of the motor is shorter. The non-conducting time period after excess current detection is shortened to ensure start-up of the motor, while at the same time, the non-conducting time period is lengthened after a predetermined time from the start-up of the motor to suppress the generation of heat of the group of switching elements. <P>COPYRIGHT: (C)2009,JPO&INPIT |
