| 摘要 |
PROBLEM TO BE SOLVED: To prevent a motor from being rotated almost with no load in three- phase motor drive circuit. SOLUTION: A power device FET is provided in each phase of a motor M on the high side and on the low side. These power devices are controlled by a high-side pre-driver circuit 2 and a low-side pre-driver circuit 3, respectively. Transistors Q5, Q6, Q7 that are turned on/off according to the input of drive signals are added to the high-side pre-driver 2. A supply voltage for the high-side pre-driver obtained by adding the output of a 12-V regulator 5 to the voltage of a battery BT, is applied to the gate of the power device FET 1 through series-connected resistors R1, R2 by turning on the transistor Q7. Current flowing to the signal line through Zener diodes ZD2, ZD3 for gate breakdown voltage protection through the other power devices that are turned on according to position signals, and a motor, is reduced by means of the resistors R1, R3 to a value equal to or below the motor current at no load. Motor rotation is thereby prevented. |
