The MAX5003 high-voltage switching power-supply controller has all the features and building blocks needed for a cost-effective flyback and forward voltagemode control converter. This device can be used to design both isolated and nonisolated power supplies with multiple output voltages that operate from a wide range of voltage sources. It includes a high-voltage internal start-up circuit that operates from a wide 11V to 110V input range. The MAX5003 drives an external Nchannel power MOSFET and has a current-sense pin that detects overcurrent conditions and turns off the power switch when the current-limit threshold is exceeded. The choice of external power MOSFET and other external components determines output voltage and power.