| 摘要 |
PURPOSE:To provide the phase control circuit for motor of vacuum cleaner whose output is not reduced by rapidly deteriorating the input even when the suction pressure becomes the prescribed value and the motor input reaches the limit value. CONSTITUTION:The detection voltage signal of a pressure sensor 2 is amplified by a signal amplifier circuit 3, resulting in obtaining a pressure detection voltage signal VB. Control signal generation circuits 4, 5, and 7 compare the pressure detection voltage signal VB and the power supply voltage signal VA. Everytime when the power supply voltage signal VA reaches the voltage value of the signal VB, they generate circulation angle phase control signals and control the circulation angle of a semiconductor switching element 9 for power control. The circulation angle of the switching element 9 exceeds the inflection point phase angle whose reduction rate of the motor input power changes remarkably when the suction pressure becomes higher than the prescribed value. |
