| 摘要 |
<p>PROBLEM TO BE SOLVED: To suppress the wasteful power consumption and omit a smoothing circuit by generating a pulse width modulation signal changed in modulation degree according to a comparative value obtained by arithmetically processing the voltage of a battery power source with a reference voltage by arithmetic processing, and controlling a current switching means between a lighting load and the battery power source. SOLUTION: A one-chip type microcomputer 7 controls the pulse width modulation degree from a data obtained by dividing an input voltage data Vin by potential dividing resistors 13, 15 and a rated voltage Vu of reference voltage according to an arithmetic program stored in a ROM, and switches a drive element 11 by a rectangular wave signal modulated by a Duty (the ON rate per repeat period of the rectangular wave signal) satisfying the arithmetic expression so that a lighting bulb 5 consumes an average power PL. Since the flicker can be made inconspicuous by setting the frequency of the repeat period of the Duty high to drive the lighting bulb 5 with a high frequency switching signal, it is not required to provide a smoothing circuit between a switching element 9 and the lighting bulb 5.</p> |
