| 摘要 |
A TRIAC dimmer gates an AC waveform from an AC power source in proportion to a control signal and outputs a TRIAC pulse having part of the waveform missing. The TRIAC pulse is rectified and is applied to an LED array and the drive current flowing to the LED array is detected at a current detection resistor. The drive current value and a predetermined value are compared at a comparator and in accordance with the comparison result thereof the control transistor is turned off. Then, the TRIAC pulse is converted to a DC voltage signal and in accordance with the obtained DC voltage signal the drive current value or the predetermined value input by the comparator are changed. Furthermore, instead of the TRIAC pulse, a PWM pulse supplied from an external source may also be utilized. |
