| 摘要 |
PROBLEM TO BE SOLVED: To make it possible to precisely perform an automatic adjustment of a focus voltage by supplying a pulse voltage, which is in proportion to a reference voltage, between an embitter and a base of a medium voltage generation transistor equipped on the high voltage side of a flyback transformer and varying a medium voltage taken out from the output side of the medium voltage generation transistor. SOLUTION: A variable medium voltage generation device is equipped with plural high voltage coils 2 and a high voltage diode 3 on a secondary side of a flyback transformer, a DC voltage V occurs in a cathode part 4 of the high diode 3 in the middle stage and a DC potential part is constituted. This cathode part 4 is provided with a transistor 8 together with a resistor or the like. When a focus voltage is taken out of an emitter part of the transistor 8, it is possible to greatly vary the focus voltage by a pulse voltage of several Vs only by varying a voltage between the emitter and a base into around 0.7 V. An adjustment of the focus voltage is performed by varying a reference voltage V1. |
