Adjustable DC electronic load

Elektronsko breme za enosmerne razmere je laboratorijski testni instrument, ki v testnem okolju doprinese veliko dodatnih možnosti testiranja. Uporablja se za testiranje napajalnikov, usmernikov, sončnih celic itd., saj se z napravo lahko nastavi poljubno breme. Poleg nastavljivega bremena instrument meri še napetost, tok in moč ter ob oplemenitvi s programsko opremo izračuna še energijo itd. Vse to seveda privede do velike kompleksnosti in tudi cene, zato je v nalogi predstavljena teorija delovanja elektronskega bremena, ki se nato uporabi za izgradnjo preproste in cenovno ugodne naprave z večino funkcij, kot jih ponuja komercialna izvedba. Prvi korak naloge predstavlja izbiro funkcij, ki smo jih želeli implementirati, sledi načrtovanje, pri katerem se s pomočjo enostavnih struktur izvedejo posamezni deli elektronskega bremena in nato s pomočjo simulacije preveri delovanje, preden se prototip sestavi. Ob zadovoljivih rezultatih simulacije se je sestavil prototip, na katerem smo izvedli funkcionalne teste in krajše meritve, ki pa so pokazale neprimerne regulacije hladilnega sistema in merjenje toka. V nalogi sledi opis načrtovanja druge revizije, kjer smo napake odpravili in optimizirali s pomočjo simulacije. Nato smo načrtali izboljšano tiskano ploščico, na katero smo namestili nove komponente in jo namestili v ohišje, v katerem je poleg tiskanine tudi hladilni sistem in uporabniški vmesnik. Pred testiranjem izdelka smo izvedli kalibracijski postopek, ki zagotovi pravilno merjenje in nastavljanje regulacijske zanke. Meritve so pokazale linearnost merilnih delov vezja in natančnost znotraj želenih omejitev na tokovnem, napetostnem in močnostnem področju. Prav tako smo preverili tudi uspešnost odvajanja toplote iz tranzistorjev v hladilno rebro in nato ven iz instrumenta. Ob analizi vseh rezultatov smo sklenili, da je cilj načrtovanja in izdelave elektronskega bremena dosežen. Poleg tega pa smo podali možne izboljšave, kot so bolj natančno merjenje, sprememba tokovne zmogljivosti in dodajanje večjih programskih funkcij, kot so zunanja komunikacija med instrumentom in računalnikom.The DC electronic load is a laboratory test instrument that provides a wide range of additional options in the test environment. It is used to test power supplies, rectifiers, solar cells, etc., as any adjustable load. In addition to adjustable load, the instrument also measures voltage, current and power and when enriched with software, also calculates energy, etc. Naturally, all this leads to great complexity and higher price, so the thesis presents the theory of electronic load operation, which is then used to build a simple and affordable device with most of the functions offered by the commercial implementations. The first step presents the selection of the implemented functions, followed by the design part, where individual parts of the electronic load are designed using simple structures, and then with the help of simulation, the operation is checked before the prototype is built. With the satisfactory results of the simulation, a prototype was made and functional tests with short measurements were performed, which showed inappropriate current measurement and regulation of the cooling system. The next step was the second revision, where the errors were eliminated and optimized through simulation. After a successful simulation results, an improved printed circuit board was designed, where new components were used and a housing was built which encloses the prototype, the cooling system and the user interface. Before the product testing, a calibration procedure was performed to ensure correct measurement and adjustment of the control loop. The measurements showed the linearity of the circuit measuring parts, and the accuracy within the desired current and voltage limits, and power ranges. The effectiveness of heat flow from the transistors to the heat sink and then out of the instrument was also checked. After analyzing all the results, it was concluded that the goal of electronic load design and manufacture has been achieved. In addition, possible improvements such as more accurate measurement, change in current capacity and addition of major software functions such as external communication between the instrument and the computer are given