We have added the PWM dimming to a number of the boards. The photo here shows the PWM dimming with the low voltage application. The circuit inside the square at the top left of the PC board is the same as the circuit that was on the previous application for low voltage. The circuitry just immediately to the right of that is a 555 timer to do the 100 Hertz PWM. We implement the dimming by controlling the feedback pin and making it think it is over current, so that it turns the current on and off to the LED.