Patent ID: 6815911
Filing Date: 2004-11-09
Classification: H05B,Y02B

Abstract:
A filament lamp light quantity control method for controlling a light quantity of a filament lamp, comprising:providing a current detection sensor connected in series to the filament lamp having a characteristic in which a change in a light quantity of the lamp is substantially proportionate to a square of a power consumption; providing a multiplication circuit for generating a voltage Vw proportionate to a product of a terminal voltage V of the filament lamp and an output voltage Vi of said current detection sensor; providing a square root circuit for generating a voltage V2 proportionate to a square root of a control voltage V1; providing an error amplifier circuit for controlling an error to a minimum by comparing the output voltage Vw of said multiplication circuit and the output voltage V2 of said square root circuit; providing a constant voltage source unit for supplying an electric power to the filament lamp, the unit being connected to an output terminal of the error amplifier circuit; and controlling the light quantity of the filament lamp by controlling said control voltage.