Cost-Effective Transformerless Offline Supply for Light Load Applications (Rev. A)

This design idea provides a simple non-isolated AC/DC power supply for low power applications. Thedesign uses a capacitive-dropper front-end combined with a LM46000 SIMPLE SWITCHER® buckregulator from Texas Instruments. The circuit provides 3.3 V at a minimum of 100 mA from a line supply of90 VAC to 265 VAC. Theory of operation as well as design equations and performance results are given.