The Supertex HV9904 is a second order PWM controller designed to provide a constant average current output or a constant average voltage output from an input of 10V to 400V DC or directly from rectified AC mains up to 280V. The second order topology is capable of extremely high dynamic control range, allowing operation directly from rectified AC mains without the need for bulky and expensive high voltage input electrolytic capacitor. The PWM control utilizes feed forward circuitry to compensate for large variations in input voltage (i.e. rectified AC) and a novel integrator lock loop PLL scheme to regulate a differentially sensed feedback node where the signal may be discontinuous. This feedback node could be a current sense resistor or divider from regulated output voltage. For a constant load the switching frequency will be nearly constant with a dither of a few kHz helping to meet FCC conducted emissions requirements.