The yellow trace (TP1) shows the pulsating DC voltage from the bridge rectifier. The blue trace (TP2) shows that the peak voltage across the LEDs and resistor is controlled at 108 V regardless of input voltage. This is confirmed by the current probe (the green trace) measuring 25 mA in all cases. The blue trace also shows that the On-time for the LEDs will vary from 47% to 56% with a +/- 10% change in the input voltage. This results in an approximate +/- 10% change in light output.