| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To generate down light without using an AC dimmer. <P>SOLUTION: This DC lighting system 1000 includes a voltage-variable DC power source not shown in the figure, in its foregoing part. In a control voltage generating part 101, the outputs of operation amplifiers IC2B, IC2C for forming voltage followers become V<SB>b</SB>, V<SB>0</SB>respectively. The emitter potential of a pnp transistor Q<SB>2</SB>becomes V<SB>0</SB>. A potential difference of V<SB>b</SB>-V<SB>0</SB>is produced between the terminals of a resistance R<SB>10</SB>. If V<SB>b</SB>is larger than V<SB>0</SB>, I<SB>R10</SB>=(V<SB>b</SB>-V<SB>0</SB>)/R<SB>10</SB>flows. If V<SB>b</SB>is not more than V<SB>0</SB>, no current flowing into the emitter of the pnp transistor Q<SB>2</SB>is produced. The emitter current I<SB>3e</SB>of a pnp transistor Q<SB>3</SB>is an LED current of a light emitting part 200, and the operation amplifier IC2A controls the pnp transistor Q<SB>3</SB>so that R<SB>14</SB>I<SB>3e</SB>becomes equal to V<SB>C</SB>. The LED current of the light emitting part 200 is 0 when the cathode potential V<SB>a</SB>of a diode D<SB>1</SB>is the minimum value V<SB>amin</SB>, and is I<SB>3emax'</SB>when the potential V<SB>a</SB>is the maximum value V<SB>amax</SB>. The potential is linearly controlled between the maximum and minimum values. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
