| 摘要 |
PROBLEM TO BE SOLVED: To provide a device wherein a circuit in which the lamp current is not affected by the input voltage is constituted and deterioration of the brightness of the lamp due to input voltage fluctuations is not brought about, and wherein more inexpensive and smaller-sized components can be used. SOLUTION: A tuning circuit in which the resistance value varies by the input voltage is provided in parallel with a frequency setting resistor, and at the time of a low input voltage, the combined resistance value of the frequency setting resistor and the tuning circuit is increased and the frequency is decreased, thereby the lamp current is increased. In a high input voltage, the combined resistance value is decreased as opposed to the case of the low input voltage and the frequency is increased, thereby the lamp current is decreased. By these arrangement, the lamp current can be kept constant regardless of the input voltage. COPYRIGHT: (C)2004,JPO |
