| 摘要 |
PURPOSE:To obtain a cathode-ray tube free from blooming by providing a means to take out a part of electron beam at a prescribed proportion as a focus electrode current, and a focus power supply circuit which outputs an output voltage close to the most suitable focus voltage in accordance with the magnitude of a focus electrode current. CONSTITUTION:A limiter 9 is provided in a focus electrode 3 that constitutes the means to capture a part of an electron beam at a prescribed proportion and to take out it as a focus electrode current IGf. The limiter 9 functions to limit the diameter of the electron beam 6 that passes through the focus electrode 3 and makes it constant. Thus captured electron beam is made the focus electrode current IGf that flows through the focus power supply circuit 5b to reduce its output voltage EF. In this case, such constitution that the limiter 9 is provided in the focus electrode 3 and the current IGf is taken out, however, such constitution that the length of the diameter of the electron beam passage hole of the focus electrode 3 is set at a suitable value to take out the necessary amount of current IGf, is acceptable. |
