1. Technical Field of the Invention
The present invention relates to: an LED (Light Emitting Diode) drive circuit that drives an LED; and an LED illumination apparatus that uses an LED as a light source.
2. Description of the Prior Art
An LED has features of a low electric-current consumption, a long life and the like and is spreading its application into not only a display apparatus but also an illumination apparatus and the like (e.g., see JP-A-2008-235530 and JP-A-2006-319172). Here, in an LED illumination apparatus, to obtain a desired illuminance, a plurality of LEDs are used in many cases.
A general illumination apparatus often uses a commercial 100 VAC power supply; and considering a case and the like where an LED illumination apparatus is used instead of the general illumination apparatus such as an incandescent lamp and the like, it is desirable that the LED illumination apparatus also is so structured as to use the commercial 100 VAC power supply like the general illumination apparatus.
Besides, in a case where light adjustment control is applied to an incandescent lamp, a phase control type of light adjuster (generally called incandescent lamp light controller) is used which is able to easily perform the light adjustment control by turning on a switching element (generally, a thyristor element or a TRIAC element) at a phase angle of an a.c. power supply voltage and by supplying electricity to the incandescent lamp by means of only one volume element.
Various techniques are necessary to connect the LED illumination apparatus to an existing phase control type of light adjuster; and a design value as one of the techniques significantly depends on the light adjuster that is used. However, there are many kinds of light adjusters, so that there are many cases where it is hard to imagine to what kind of light adjuster the LED illumination apparatus is connected in designing an LED drive circuit and an LED of the LED illumination apparatus. There is a case where even if erroneous operation does not occur and a light adjustment characteristic is appropriate in a light adjuster, erroneous operation such as a flicker and the like occurs and the light adjustment characteristic is improper in another light adjuster. Besides, there is a case where a design value is set to deal with various kinds of light adjusters, which however causes problems that the electric-current consumption of the LED increases and the efficiency deteriorates.