| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an LED illumination device emitting white-color light with stable brightness. <P>SOLUTION: An input pulse signal D is turned into a drive pulse signal Dg shifted in phase by a time constant tg by a resistor Rg and a capacitor Cg. The drive pulse signal Dg is inputted into a base of a transistor Tr10, a collector is connected to a current limiting resistor Rg' through an LED 12, and the current limiting resistor Rg' is connected to a power supply voltage Vcc. When the pulse drive signal Gf is H, the transistor Tr10 is turned on for a drive current to flow, and a light-emitting efficiency of the LED 12 is controlled by the current limiting resistor Rg'. Likewise, when the input pulse D is H, the drive signals Dg, Dr, Db are time-shifted in turn to become H, and LEDs 12, 14, 16 of RGB are lit in turn. Since resistance values of current limiting resistors Rg', Rr', Rb' are set in accordance with forward-direction voltages Vf of the LEDs 12, 14, 16, the light-emitting efficiency of the LEDs at light emission is made uniform. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
