| 摘要 |
PURPOSE:To prevent the breakdown of a horizontal output transistor arising at the abnormal time of high horizontal oscillating frequency by detecting the rise of high voltage in a cathode-ray tube and stopping a horizontal driving output while detecting the drop of high voltage and stopping a main power supply circuit. CONSTITUTION:While stopping the rise of high voltage in a cathode-ray tube and stopping a horizontal driving output, the drop of high voltage is detected and a main power supply circuit 32 is stopped. That is, as the voltage in a cathode-ray tube 24 is boosted, an output from a rectified current smoothing circuit 20 is increased, a Zener diode ZD1 is turned on to activate a hold-down circuit 22, and the operation of a horizontal output transistor Tr1 is stopped for protecting the horizontal output transistor Tr1. Thus, the horizontal output transistor Tr1 can be protected by the simple constitution of circuits. |
