| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a light-emitting diode-driving power supply unit capable of changing the waveform of an input current to an almost sinusoidal waveform without using a smoothing capacitor. <P>SOLUTION: The power supply unit has rectifying means (2-5) to rectify a commercial ac power supply voltage and is to drive a group of light-emitting diodes (10) connected in series by using the output voltage of the rectifying means (2-5). The power supply unit includes: means (14a, 14b, 100) to reduce and change the number of serial connections of the light-emitting diodes in the group of the light-emitting diodes (10) in a first period spent until the output voltage of the rectifying means (2-5) reaches a prescribed value and in a second period in which it decreases from the prescribed value; and current control means (7, 17) interposed between the rectifying means (2-5) and the group of the light-emitting diodes (10) to control a supply current to the group of the light-emitting diodes (10) so that the instantaneous input current of the means (2-5) has a waveform similar to the waveform of an instantaneous input voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
