| 摘要 |
<p>PURPOSE:To make the lighting output of an LED by mounting a resistance-type poten tial divider circuit compensating the fluctuation of the voltage of an LED driving control circuit generated from a power supply and a circuit resistor on the basis of the lighting factor of the LED and a varistor circuit compensating the fluctuation of the light output of the LED generated from a temp. change. CONSTITUTION:Correction control voltage Vrf is represented by formula I. Further, V2=R1/(R1+R2).VDD is formed. Herein, the forward voltage VF of a varistor 15 does not change too much even when a forward current If changes. Therefore, the correction control voltage Vrf is represented by formula II. This change component (AC component) DELTAV2 is respresented by formula III through a condenser 6. The correc tion of temp. is also carried out on the basis of the forward voltage VF of the varistor 15. A varistor circuit and a resistance-type potential divider circuit satisfying the above mentioned formulae are provided and, by making the synthesized supply voltage of the varistor circuit and the resistance-type potential divider circuit same to the supply voltage of an LED drive IC 3, the voltage drop component of supply voltage due to the lighting factor of an LED head is converted to the fluctuation of the correc tion control voltage Vrf simultaneously with the correction of temp. to be compensated.</p> |
