The UC3844 is a fixed frequency current-mode PWM controller. This IC is specially designed for Off-Line and DC to DC converter applications with minimum external components.
The VIPER22A is a Popular SMPS controller IC form STMicroelectronics that has been extensively used in AC to DC Converters in offline power circuit designs.
The VIPER12A is a SMPS controller IC that consists of a PWM controller with a power MOSFET. It can take in AC voltage from 85V to 265V and convert to low level voltage like 5V with output current from 10mA to 200mA.