Galvanically isolated differential data transmission using capacitive coupling and a modified Manchester algorithm for smart power converters

In this paper, a method for encoding and decoding digital data signals using a modified form of the standard Manchester code for the application in galvanically isolated data transmission in smart power electronics is described. The method includes a modified encoder circuit and a matching decoder circuit that is able to rebuild the original clock and data signal without a separate transmission of the clock signal. A capacitive coupling element with a corresponding signal conditioning circuit was placed between the encoder and decoder circuit to achieve a galvanic isolation between the primary side that processes the data signals and the secondary side that is responsible for the processing of power in smart power devices. After a description of basic principles of the transmission of data over a galvanic isolation and the state-of-the-art of Manchester code based data transmission, the encoding and decoding process of the modified Manchester code is elaborated and experimental results are presented.