| 摘要 |
The on screen display (OSD) circuit detects brightness of television room, displayes the brightness on a screen and generates alarm signal when the brightness is over or below the recommended brightness range. The circuit includes a brightness level detector (5) comprising a photo sensor (1) for sensing the brightness, a current to voltage converter (2) for converting output level of sensor current to voltage level, an amplifier (3) for amplifying the voltage level, and an interfacing unit (4) for transmitting output voltage level of the amplifier to a microcomputer, a switch (12) for controlling the brightness level detector (5) according to control signal transmitted from a microcomputer, a level comparator (9) for checking that the output voltage level of the brightness level detector is within a certain range, and an alarm signal generator (10) for generating alarm signal for outranged brightness. |
