| 摘要 |
<p>A high-voltage transformer driving circuit (12) and a high-voltage transformer (13) drive a discharge tube (1). A tube current synthesizing/high-pass filter circuit (15) synthesizes the tube current of the discharge tube (1), and extracts pulse components caused by arc discharge from the synthesized tube current. A pulse retaining circuit (16) retains the extracted pulse components for a predetermined period of time. A comparator (21a) compares the output from the pulse retaining circuit (16) with a threshold, and outputs a signal that indicates the occurrence or non-occurrence of arc discharge. When arc discharge is detected, a logic circuit (20) stops the high-voltage transformer driving circuit (12) operating. With this, arc discharge can be detected with high accuracy at low cost.</p> |
