| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a dimming device in which flickering of a light source is reduced by accurately detecting zero crossing of an AC power source. <P>SOLUTION: A dimming device A comprises: a triac Q1 having a self-holding function; a zero-cross detecting circuit 1 which outputs a zero-cross signal, if an input voltage from a commercial AC power source AC is within a predetermined range near zero crossing; a microcomputer 3 which counts the signal width of the zero-cross signal output from the zero-cross detecting circuit 1, and constitutes a zero-cross determining means for determining the zero-cross signal to be a zero crossing of the commercial AC power source AC, if the count value is equal to or greater than a predetermined reference value; and a dimming control circuit 2 which performs phase control in DC trigger method which continues to give a trigger signal that drives the triac Q1 during an on-period set in synchronization with the zero-cross signal determined by the microcomputer 3. <P>COPYRIGHT: (C)2012,JPO&INPIT |
