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

Abstract

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

Active common‐mode filter for capacitive‐coupled isolated signalling

“…Industry‐established applications include digital isolator integrated circuits (ICs) [1], isolated RS‐485 transmission systems [2] and the replacement of Ethernet magnetics [3]. Moreover, capacitive coupled signalling is proposed for IGBT drivers [4] and distributed battery management systems [5].…”

“…Coupling capacitors are simpler and cheaper compared to magnetic or optical systems. Suitable capacitors can be either PCB-mount components [3], printed in the layers of a PCB [4], or formed by conductors and dielectric material [5]. The voltage rating can be almost freely chosen as required by the application.…”

Integrated galvanically isolated MOSFET and IGBT gate-driver circuit with switching speed control

“…The ASIC input stage has two functions: the signal transmission and the power transmission over the galvanic isolation. For signal transmission, the ASIC input stage encodes the PWM signal generated by the microcontroller by using a modified Manchester code [2] that is transferred differentially over two ceramic capacitors providing the necessary galvanic isolation, especially when used for the high-side power switch in power converters using a half-bridge or a full-bridge topology. For the power transmission, the ASIC input stage uses a transformer connected in a push-pull configuration to transfer up to 2W of power from a 15V DC supply.…”