| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit for LED light source in which impression of spike voltage is prevented and changes of luminance due to temperature rise is prevented in an illumination apparatus using LED for a light source. SOLUTION: A spike voltage eliminating circuit NR, which is made of a resistor Rx and a capacitor Cx, is connected in parallel with a DC power supply DC. And a constant current circuit of current mirror by a transistor Trb and a transistor Trc is connected to an LED block Da. Each LED D1 -D4 is protected from the spike voltage by a spike voltage eliminating circuit NR. And since the load current Ia of each LED D1 -D4 is controlled to a constant value, change of luminance due to temperature rise when LED is in operation can be prevented. |
