This application note describes Linear Technology’s 2-Wire Virtual Remote Sensing technology for voltage regulators. The technology eliminates the line-drop effect on the source output voltage and does not require additional sense wires.
The document introduces a method called "Virtual Remote Sensing" (VRS) that allows power supplies to estimate and compensate for voltage drops caused by wire resistance without requiring dedicated sense wires. This is achieved using the LT4180 IC, which superimposes a small square wave current onto the output current. By measuring the resulting voltage drop at the supply side, the system can calculate the wiring loss and adjust the output voltage accordingly to maintain accurate load regulation.
The note provides detailed circuit examples for implementing this technique in various configurations, including discrete linear regulators, monolithic IC regulators (such as LT3080), flyback boost converters, step-down buck converters, and fully isolated switching supplies. It highlights that minimal changes are typically needed to existing designs to integrate the VRS feature.
The LT4180 forces a small square wave current with a peak-to-peak amplitude equal to 10% of the DC current.
The design simplifies with a 3V to 50V input range for the power supply.
A wiring drop equal to 50% of the load voltage results in only a 1.5% shift in load voltage value.