| 摘要 |
PURPOSE:To prevent the break of the neck of a Braun tube to protect the Braun tube by providing a charging/discharging circuit and a high voltage breaking circuit which generate a short-circuit detection output for short-circuit of a vertical connection capacitor. CONSTITUTION:The voltage at negative-side terminal d of vertical connection capacity C1 charges capacity C4 with the time constant of capacity C4 and resistance R10 and discharges capacity C4 with the time constant of capacity C4 and resistance R11. The potential at point c of the positive-side end of capacity C4 is set to a value near zero and is prevented from being fluctuated, and emitter-grounded transistor Q5 of X-ray protection circuit P2 is held off. When capacity C1 is short-circuited, a DC is superposed to deflection yoke Y1, and the voltage at point d rises, and as the result, the potential at point c rises with the average value of point d, and Q5 is turned on to operate circuit P2, thereby protecting Braun tube BT1. By this constitution, in case that capacity C1 is interposed between Q1 and Q2 for vertical output and yoke Y1, tube BT1 is protected to prevent neck break. Even in case that no reference voltage giving circuit from the external exists in circuit P2, tube BT1 can be protected. |
