1 Description

This TI Design implements a class 0.5 three-phase transformerless energy measurement system with isolated shunt sensors by using isolated delta-sigma modulators. The delta-sigma modulators have their output circuitry capacitively isolated from input circuitry, thereby providing transformerless data isolation. The high-side of each modulator is powered by a cap-drop supply that is also transformerless. Because a transformer is not used here, this TI Design is inherently magnetically immune. In addition, the high-side cap-drop power supply reduces the entire system cost, has inherently low conducted and radiated emissions, and reduces the current consumption drawn from the low-side power supply because the high-side is separately powered from mains instead of being derived from the low-side power supply.