| 摘要 |
PURPOSE:To save a LED display current amounting almost all power consumption of a LED display wrist watch, etc., by adjusting the brightness of a LED by the use of a photo oscillation semiconductor element whose oscillation frequency varies in proportion to luminous intensity. CONSTITUTION:With luminous-intensity measurement display switch 9 of a LED display wrist watch depressed, the resetting of shift register 20 is released and transmission gate 24 becomes conductive through OR gate 26, so that photo oscillation semiconductor element 5 will oscillate at a frequency proportional to luminous intensity. At this time, the resetting of counter 29 is also released to count the oscillation frequency of semiconductor element 5. On the other hand, since controller 31 has been set under optimum LED brightness conditions by output discrete value 30 of counter 29, display part 34 is displayed with brightness which corresponds to ambient brightness. It is also recommended to vary the luminous intensity of display part 34 either by controlling the duty ratio of pulse waves by output 30 or by changing over several LED driving-current limiting resistances different in value by a switching signal. |
