derived through intelligent monitoring of the input voltage waveform the circuit and method described is adapted to higher current applications such as led lighting systems using the latest high power leds application_number US 201213656475 A description fig5 7 show the typical shapes of the ac voltage input presented to a light or lighting system by standard ac dimmers fig5 shows a forward phase control chopped sinewave typical of most silicon controlled rectifier scr type incandescent wall dimmers fig6 shows a reverse phase waveform which is sometimes provided by dimmers made for electronic or capacitive loads fig7 shows the type of ac voltage waveform presented by an autotransformer and some higher end dimming systems designed for theater lighting in all of these cases it is the input voltage that is modified reduced in amplitude or chopped out during part of the sinewave in order to present a lower average or rms voltage to the load as explained in the background section this type of dimming can cause non linear and unpredictable results when it is used with a switcher regulator circuit as is often the case in led lighting products the present invention is best understood by starting with a typical implementation of a prior art switching regulator led driver circuit fig8 shows a diagram of a typical buck switching regulator circuit configured to output a constant current to a load a detailed description of the operation of a buck switching regulator is beyond the scope of this discussion but can be found in such reference documents as the national semiconductor application note an 556 and the article.