This bachelor's thesis describes the design and development of an isolated printed circuit board for an in-cylinder pressure measurement system used in an internal combustion engine.
Measuring cylinder pressure enables monitoring of the combustion process and provides an important basis for improving engine efficiency, reducing emissions, and detecting undesirable phenomena. As the measurement circuit operates in a demanding environment with high temperatures, vibrations, electromagnetic interference, and large pressure fluctuations, it must be designed to ensure reliable signal processing, galvanic isolation, and adequate immunity to disturbances.
The basic operation of the circuit is described first, followed by the requirements the circuit must fulfil. Before the design process begins, various methods for meeting these requirements are presented. Isolated power converters are introduced first, along with their operating principles, advantages, and disadvantages. This is followed by a chapter on galvanic isolation and ratiometricity, in which different approaches to achieving these two properties are analysed.
The circuit design procedure is presented, with a detailed description of the selected methods and components. First, the selection of the isolated power converter is discussed, including a detailed explanation of its operation and the determination of its components. Next, the methods chosen for galvanic isolation of the output measurement signal and for ensuring ratiometricity with respect to the supply voltage are presented and justified. The selection of these methods is supported by simulation results and measurements performed on test circuits.
Compliance of the developed printed circuit board with the specified requirements is verified by measuring power consumption, validating the correct operation of individual circuit modules, and confirming the ratiometric behaviour of the output signal within the measurement operating range.
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