| 摘要 |
PROBLEM TO BE SOLVED: To provide a current detecting circuit for detecting forward currents and backward currents inputted to an inverter circuit by using a single power supply voltage, and to provide an excess current protecting circuit using the current detecting circuit. SOLUTION: In the driving device of a brushless motor 42 in which a double voltage rectifier circuit 22 is combined with an inverter circuit 25, a serial circuit constituted of resistances 46 and 47 for detecting currents is inserted into a negative side current power line 24, and a voltage Va generated in the resistance 46 by forward currents is detected by a first detecting circuit 48, and a voltage Vb generated in the resistance 47 by backward currents is detected by a second detecting circuit 49 with the common connection of those resistances 46 and 47 as a reference potential (ground terminal). Those voltages Va and Vb are compared with reference voltages V3 and V4 by single voltage driving comparators 50 and 58, and a forward excess current signal Sa and a backward excess current signal Sb are obtained. |
