Analog Isolated Multilevel Quantizer for Voltage Sensing while Maintaining Galvanic Isolation

A low-power, compact device for performing measurements in electrical systems with isolated voltage domains is proposed. Isolated measurements are required in numerous applications. For instance, a measurement of the bus voltage for a system with a high supply voltage and lower isolated local voltage level may be needed for system health monitoring and control. Such a requirement may necessitate the use of isolation amplifiers to provide voltage telemetry for the local system. Isolation amplifiers require dual galvanically isolated supplies and use magnetic, capacitive, or optical barriers between primary and secondary sides. Producing this supplemental voltage requires an extra voltage converter, which consumes power and generates electromagnetic interference which must, in turn, be filtered. Complex designs incorporating feedback are needed to achieve linear response. The proposed Analog Isolated Multilevel Quantizer (AIMQ) addresses these issues by monitoring the primary-side signal and communicating the results to the secondary side using a novel scheme involving Zener diodes, optocouplers, transistors, one-hot coding, and discrete outputs. The result is a low power isolated transducer that can in principle be extended to an arbitrary bit depth.