The NCP1050 through NCP1055 are monolithic high voltage regulators that enable end product equipment to be compliant with low standby power requirements. This device series combines the required converter functions allowing a simple and economical power system solution for office automation, consumer, and industrial products. These devices are designed to operate directly from a rectified AC line source. In flyback converter applications they are capable of providing an output power that ranges from 6.0 W to 40 W with a fixed AC input of 100 V, 115 V, or 230 V, and 3.0 W to 20 W with a variable AC input that ranges from 85 V to 265 V. This device series features an active startup regulator circuit that eliminates the need for an auxiliary bias winding on the converter transformer, fault detector and a programmable timer for converter overload protection, unique gated oscillator configuration for extremely fast loop response with double pulse suppression, power switch current limiting, input undervoltage lockout with hysteresis, thermal shutdown, and auto restart fault detection. These devices are available in economical 8-pin dual-in-line and 4-pin SOT-223 packages.