| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a power supply device in which an increase in heat generation and lowering in efficiency can be prevented by suppressing a variation in the brightness of an LED regardless of the number of LEDs connected in series, and to provide an illuminator equipped with that power supply device. <P>SOLUTION: A current flowing through a plurality of LEDs 9, 9, ... is detected by a resistor 61 and converted into a voltage before being outputted to an operational amplifier 71. The operational amplifier 71 outputs a voltage Vo corresponding to the inputted voltage and a current Io outputted from the operational amplifier 71 depending on the voltage Vo is compared with a set current Ir flowing through resistors 74, 75. When the current Io exceeds the set current Ir, a surplus current Ie (Io-Ir) is fed through the series circuit of a resistor 77, a photodiode 76b and a shunt regulator 78, and a PWM control section 51 stops a drive signal outputted to the gate of an FET 53 and lowers the output voltage from a converter circuit 5, thus decreasing the current If. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
