| 摘要 |
<p>PROBLEM TO BE SOLVED: To maintain constant brightness, when the battery of a light-emitting element is driven, the consumption of the battery is suppressed, and the service life of the battery is prolonged. SOLUTION: A switching means such as a transistor, for example, is provided between a battery 1 and a light-emitting diode 3. A current control resistor 2 is series-connected to the light-emitting diode. A current is applied or shut off at a constant cycle by a pulse width modulation means 6 on the switching means 4. For the cycle, a value of an extent, where the blinking of light is about imperceptible by human eyes, is selected. The rate of the pulse width in constant pulse cycle is determined by a pulse width adjusting means 5. The pulse width adjusting means 5 monitors the voltage of the battery 1, and duty ratio is adjusted in such a manner that the time in which a current is applied to an LED 3 becomes short, when battery voltage is high and the time when a current is applied to the LED becomes long, when the battery voltage is low.</p> |
