| 摘要 |
PURPOSE:To enable to operate a stable SCR converter by generating a protection signal by an overvoltage applied to an SCR bulb and a detection signal of a current flowed to the bulb or an abnormal pulse of a gate circuit, thereby preventing the damage of the SCR. CONSTITUTION:A forward voltage detector FVD, a reverse voltage detector RVD and an overvoltage detector OVD connected in parallel with SCR bulb TV transmit via light guides LG1-LG3 a forward voltage signal FV, a reverse voltage signal RV and an overvoltage signal OV to a gate pulse generator PG. After the light signals are converted via photoelectric converters LE1-LE3 to electric signals, the signal OV is inputted to an OR circuit OR2, the signal FV is inputted to an AND circuit AND1, and the signal RV is inputted through a timer circuit TM1 to the reset input of an FF2. Another input to the OR circuit OR2 is a phase control signal PHS-ON, and the output becomes the set input to an FF1. |
