| 摘要 |
The retrace pulse voltage developed across a television receiver flyback transformer winding is rectified and filtered to develop a voltage representative of picture tube ultor voltage. This representative voltage is applied to an input terminal of a comparator. A beam current representative voltage, obtainable, for example, at the input of a beam limiter circuit, is applied to a filter. The filter output voltage, which is the time integration voltage of the beam current representative voltage, is applied to another input terminal of the comparator. The comparator develops a disabling signal that is utilized to disable normal television operation when the ultor voltage exceeds a magnitude which differs with different values of the filter output voltage. The beam current information from the filter output increases the comparator sensitivity to ultor voltage increases at the higher beam current levels where greater amounts of X-radiation may be produced while avoiding unnecessary disabling of television operation at the lower beam current levels where greater increases in ultor voltage may be tolerated. The time constant associated with the filter is relatively short for relatively light beam current loading conditions and is changed to a relatively long time constant value under severe beam current loading conditions in order to ascertain whether a permanent current overload condition exists that requires disabling of the television receiver. |
