| 摘要 |
PURPOSE: To prevent the generation of a resonance sound or a parasitic oscillation sound, by ON-driving an electric field effect transistor on the high electric potential side of a power source, via a pressure rise circuit, to drive an electric field effect transistor on the low electric potential side of the power source by the PWM signal out of an audio frequency range. CONSTITUTION: An electric motor drive circuit 9 is equipped with a bridge circuit composed of electric field effect transistors 30A, 30B, 31A, and 31B, and the transistors 30A and 30B and those of 31A and 31B, positioned on the opposite sides facing with each other of the bridge circuit, act as a set respectively. The collectors of transistors 34 and 36 are connected to a pressure rise circuit 39 connected to the output side of a relay circuit 28, and to these collectors, operating power source voltage, pressure risen by the pressure rise circuit 39, is supplied via a resistor 37 or 38. Consequently, electric field effect transistors on the low electric potential side of a power source can be driven by a PWM signal out of an audio frequency range. |
