Relays are used in many applications. The solid state relays built up from MOSFETs are suitable for substituting the mechanical relays. They are frequently used in power electronics and safety critical adaptations. In the frame of my bachelor thesis I examined the possibility of controlling of the avalanche effect in semiconductors. Based on the results I designed an appropriate solid state relay control circuit.
Firstly, I reviewed the scientific literature according to the requirements set up by Thyssenkrupp Presta Hungary. In addition, during the designing I utilised my knowledge about FETs and Pspice simulation acquired in the frame of “Independent Laboratory” subject at the university. One of the most important parts of the planning was the design of the gate driver. During this process primarily I had to take into consideration the speed, the number of components and the price of the devices as main parameters. The other components like the power supply and the transmission levels were formed in compliance with the gate drivers. The schematic diagram of the device was drawn in Orcad Capture, while the layout of the printed circuit board was created in Orcad Layout design program.
As results of investigations I worked out two solutions, too. The first of these was implemented by a microcontroller, while the second was built up from transistors. Both variations fulfilled the (automotive) requirements, but the solution characterized by a microcontroller contained half of components and was twice faster than the other. The solution built from transistors was more temperature-dependent, but more cost-effective. Nevertheless, the use of microcontroller provides better opportunities for application and developments. The most important factor of these is the possibility of measuring phase currents by minor modification of the schematic diagram.