Off-Line Switching Regulators Simplify Converter Designs

Operating from universal line sources of 85 to 276 vac, the MC33370 through MC33374 off-line switching regulators function at 100 kHz for low power loss with a smaller transformer. The devices incorporate both a BiCMOS controller and high-voltage MOSFET on the same chip, which is used to drive the primary side of a transformer in flyback-mode applications.Use of a five-leaded TO-220 plastic package allows the incorporation of additional functionality that competing regulators lack. With no additional circuitry, the regulators offer a programmable state controller that allows implementation of four converter on/off control methods. These include: primary-side manual toggle on/off; secondary-side MCU toggle on/off; primary-side toggle request with secondary-side MCU graceful shutdown; and programmable on or off state upon application of ac power.