| 摘要 |
<P>PROBLEM TO BE SOLVED: To suppress a high frequency fluctuating voltage related to overshoot and/or ringing resulting from switching by self-control. <P>SOLUTION: A fluctuating voltage detection circuit 10 includes a capacitor 11 having an AC coupling function, and a voltage doubler detection circuit 12, and detects a high frequency fluctuating voltage such as overshoot or ringing appearing between power lines 3, 4 when a MOSFET 5 is PWM-driven. A drive circuit 17 compares an A/D-converted detection voltage Vdo with a preset changeover reference value, and decreases the slope of a driving signal if the detected detection voltage Vdo exceeds the changeover reference value, and increases the slope of the driving signal if the detected detection voltage Vdo is equal to or lower than the changeover reference value. The changeover reference value is determined such that EMI is smaller than a prescribed value on the basis of a predetermined relationship between the magnitude of the high frequency fluctuating voltage and EMI. <P>COPYRIGHT: (C)2013,JPO&INPIT |
