The MP155 is a primary-side regulator that provides accurate constant voltage regulation without the opto-coupler, and supports Buck, Buck-boost, Boost and Flyback topologies. An integrated 500V MOSFET simplifies the structure and reduces costs. These features make it a competitive candidate for off-line lowpower applications, such as home appliances and standby power. The MP155 is a green-mode-operation regulator. Both the peak current and the switching frequency decrease as the load decreases. As a result, it offers excellent efficiency performance at light load, thus improving the overall average efficiency. The MP155 features various protections such as thermal shutdown (TSD), VCC under-voltage lockout (UVLO), overload protection (OLP), short-circuit protection (SCP), and open loop protection. The MP155 is available in the TSOT23-5 and SOIC8 packages.Primary-side constant voltage (CV) control, supporting Buck, Buck-boost, Boost and Flyback topologies Integrated 500V/20? MOSFET < 100mW No-load power consumption Up to 4W output power Maximum DCM output current of 130mA Maximum CCM output current of 220mA Low VCC operating current Frequency foldback Maximum frequency limit Peak current compression Internal high-voltage current source Internal 350ns leading-edge blanking Thermal shutdown (auto restart) VCC under-voltage lockout with hysteresis (UVLO) Timer-based overload protection Short circuit protection Open loop protection