The NCP101X series integrates a fixed−frequency current−mode controller and a 700 V MOSFET. Housed in a PDIP−7 or SOT−223 package, the NCP101X offers everything needed to build a rugged and low−cost power supply, including soft−start, frequency jittering, short−circuit protection, skip−cycle, a maximum peak current setpoint, and a Dynamic Self−Supply (no need for an auxiliary winding). Unlike other monolithic solutions, the NCP101X is quiet by nature: during nominal load operation, the part switches at one of the available frequencies (65 − 100 − 130 kHz). When the current setpoint falls below a given value, e.g. the output power demand diminishes, the IC automatically enters the so−called skip−cycle mode and provides excellent efficiency at light loads. Because this occurs at typically 1/4 standby power is reduced to the minimum without acoustic noise generation. Short−circuit detection takes place when the feedback signal fades away, e.g. in true short−circuit conditions or in broken Optocoupler cases. External disabling is easily done either simply by pulling the feedback pin down or latching it to ground through an inexpensive SCR for complete latched−off. Finally, soft−start and frequency jittering further ease the designer's task to develop low−cost and robust offline power supplies quickly. For improved standby performance, the connection of an auxiliary winding stops the DSS operation and helps to consume less than 100 mW at high line. In this mode, a built−in latched overvoltage protection prevents lethal voltage runaways in case the Optocoupler would brake. These devices are available in economical 8−pin dual−in−line and 4−pin SOT−223 packages.
