AND8393 - Universal Input AC-DC Printer Adapter using NCP1219

Introduction The NCP1219 is the newest part in the NCP12XX family of current−mode flyback controllers. The controller features dynamic self supply (DSS), eliminating the need for external startup circuitry, contributing to a cost effective, low parts count flyback controller design. The NCP1219 also includes a user programmable skip cycle threshold, reducing power dissipation at light loads and in standby mode. An externally provided latch signal delivered to the Skip/latch pin allows the realization of protection functionality. The 48 W ac adapter demonstration board targets a printer adapter application with a 24 V output, reconfigurable to 7.25 V in standby mode selectable with an external signal. The use of DSS mode is demonstrated for low input voltages, while an auxiliary winding is used for higher input voltages to maintain standby power below 1 W. The NCP1219 demonstration board shows latched−mode protection function through the optional primary and secondary overvoltage protection circuits. The demonstration board is designed as an off−line printer adapter power supply. The adapter operates across universal inputs, 85 Vac to 265 Vac (47 Hz – 63 Hz). The adapter supplies a regulated 24 V output. It can deliver a steady state 30 W output with transient capability of 48 W, as defined in Figure 1.