The HV9931 is a fixed frequency PWM controller IC designed to control an LED lamp driver using a single-stage PFC buckboost-buck topology. It can achieve a unity power factor and a very high step-down ratio that enables driving a single high-brightness LED from the 85-264VAC input without a need for a power transformer. This topology allows reducing the filter capacitors and using non-electrolytic capacitors to improve reliability. The HV9931 uses open-loop peak current control to regulate both the input and the output current. This control technique eliminates a need for loop compensation, limits the input inrush current, and is inherently protected from input under-voltage condition. Capacitive isolation protects the LED Lamp from failure of the switching MOSFET. HV9931 provides a low-frequency PWM dimming input that can accept an external control signal with a duty ratio of 0100% and a frequency of up to a few kilohertz. The PWM dimming capability enables HV9931 phase control solutions that can work with standard wall dimmers.