Device and method for driving LED

1. FIRST EMBODIMENT

[0040] Hereafter, a first embodiment of the present invention is described by referring to FIG. 1. FIG. 1 is a schematic block diagram of an LED lighting device according to the first embodiment of the present invention.

[0041] An AC source 100 and a rectifier circuit 101 in FIG. 1 may be similar to those of conventional constitutions shown in FIGS. 8 to 10. As the AC source for an LED lighting device, a commercial source (having, for example, 100V to 220V and 50 Hz to 60 Hz) is generally used in consideration general versatility, but an AC source other than a commercial source may be used. Use of a single-phase AC source is assumed in this embodiment, but three-phase AC, etc. may be used as the source.

[0042] Numeral 101 denotes a full-wave rectifier circuit comprised of four rectified diodes 1011, 1012, 1013, and 1014, which rectifies a commercial AC source to output a rectified voltage waveform, as exemplified in FIG. 4, between a plus output terminal A and a minu

2. SECOND EMBODIMENT

[0068] Next, a second embodiment of the present invention is described by referring to FIG. 7. This embodiment has a constitution equivalent to one shown in FIG. 1 except that LEDs are arranged in parallel and a lighting LED selection circuit 204 and a switch circuit 205 are modified to a control logic circuit 204′ and a switch circuit 205′. Thus, the remaining parts of this embodiment are the same as those shown in FIG. 1.

[0069] In FIG. 7, LEDs 103′0-1 to 103′(N-1)-3 are divided into N number of blocks each having three LEDs as indicated by dotted frames. These blocks include block 0 comprised of 103′0-1, 103′0-2, and 103′0-3; block 1 comprised of 103′1-1, 103′1-2, and 103′1-3; likewise, block 2, block 3, . . . , block (N−2); and finally block (N−1) comprised of 103′(N-1)-1, 103′(N-1)-2, and 103′(N-1)-3. N represents an integer of not less than 1, which can be properly set depending on embodiment requirement.

[0070] In this embodiment, LEDs of each block are conne