| 摘要 |
PURPOSE:To obtain a constant voltage necessary for generating a constant current by providing a light emitting device driving circuit which supplies a driving current to a light emitting element in accordance with an input signal, a constant current circuit which supplies constant current to the light emitting device driving circuit in accordance with the voltage applied to a constant voltage input terminal and a constant voltage circuit which supplies a constant voltage to the constant voltage input terminal. CONSTITUTION:By connecting a constant voltage output terminal 13 to a constant voltage input terminal 14, a constant voltage is applied to a constant current circuit 12 by a constant voltage circuit 11 and the constant current circuit 12 supplies a constant current to an LED driving circuit 3. The LED driving circuit 3 switches the constant current supplied by the constant current circuit 12 in accordance with an input signal and supplies the switched current to an LED 5 as a driving current. When the designed constant voltage can not be obtained from a constant voltage circuit 11 due to the variation in manufacture of integrated circuits or environmental conditions, by only applying the predetermined constant voltage to the constant voltage input terminal 14 by an external circuit, the operation as a light emitting device driving integrated circuit can be realized. |
