The NCL30095A high power factor boost PWM switching regulator is designed to regulate the average current through a string of LEDs. The circuit operates in Critical Conduction Mode (CrM) based on a proven constant on-time control scheme to achieve near unity power factor. In addition to regulating a constant current, the switching regulator is optimized to support leading and trailing edge phase dimming applications. When a dimmer is detected on the AC input, an internal voltage reference of the current regulation loop adjusts the current level based on the dimmer conduction angle so the current through the LED string has a desired value based on a programmed dimming curve. The shape of the dimming curve is intended to emulate the response of an incandescent bulb while achieving NEMA SSL6 and NEMA SSL7A recommendations. An integrated HV MOSFET in a cascoded configuration supports biasing the controller during operation and eliminates the need for an auxiliary winding to provide bias power. A robust suite of protection features are included to ensure proper handling of expected fault conditions without the need for extra circuitry and a dedicated thermal fold-back input proves gradually reduction of the current above a user defined set-point.