Razvoj in izdelava 50 W ojačevalnika električnih pulzov frekvenc do 500 kHz

OBLAK, PETER (author), Križaj, Dejan (mentor)

V magistrski nalogi je opisana izdelava ojačevalnika za ultrazvočne oddajnike do frekvence 500 kHz. Zasnova vezja je bila uporabljena že v nekaterih podobnih aplikacijah. Dodal sem nekaj dodatnih komponent, saj je ojačevalnik prilagojen za ojačanje signalov, ki so specifični in so namenjeni za uporabo v medicini. V uvodu se bralec seznani z vsebino in problematiko magistrske naloge, predstavljene so osnove, ki so pomembne za razumevanje nadaljnjih poglavij. Pri načrtovanju vezja sem uporabil SPICE simulacijo, s pomočjo katere sem preizkusil delovanje različnih topologij vezij, ki so primerna za ojačanje ultrazvočnega signala. S simulacijo sem optimiral delovanje vezja in okvirno določil vrednosti elementov tako, da je na izhodni stopnji signal želene moči. V simulaciji sem izrisal poteke napetosti, tokov in moči na posameznih stopnjah ojačevalnika. Sledila je izdelava tiskanega vezja s programom KiCad. Vezje sem prilagodil tako, da je bil napajalni del ločen od signalnega. S tem sem izločil motnje, ki bi lahko nastale zaradi delovanja stikalnih naprav in transformatorja za napajanje vezja. Meritve signala na izhodni stopnji sem izvedel s pomočjo osciloskopa. Delovanje vezja sem testiral pri različnih frekvencah s priklopljenim ultrazvočnim oddajnikom, ki ima deklarirano resonančno frekvenco 350 kHz. Ugotovil sem, da ojačevalnik najbolje deluje v frekvenčnem območju od 350 do 400 kHz, kar je bilo tudi pričakovati glede na izmerjeno impedančno karakteristiko oddajnika. Za zajem ultrazvočnega signala sem uporabil hidrofon s katerim sem opazoval potek ultrazvočnega signala. Izdelana naprava omogoča generiranje izhodnih signalov amplitude 200 V in izhodne moči 50 W. Uporabljen je bil ultrazvočni oddajnik GS350-D19-BNC-PK US. Maksimalna izmerjena napetost na sponkah hidrofona je bila 20 mV, kar predstavlja intenziteto signala 5,11 · 10^5 W/m^2.

• Language: Slovenian
• Keywords: Ultrazvočni ojačevalnik, ultrazvočni oddajnik, ultrazvok, push-pull vezava.
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2015
• PID: 20.500.12556/RUL-72346
• Publication date in RUL: 14.09.2015

Secondary language

• Language: English
• Title: Research and development of a 50 W amplifier for generation of pulses of frequencies up to 500 kHz

Abstract

The thesis describes the construction of an amplifer for ultrasonic transmitters of a frequency up to 500 kHz. Similar design of an amplifer has already been used in some other applications. However, several modifcations and adaptations were necessary to meet the requirements for intended use in medicine. I used SPICE simulation for designed the circuit by means of which I tested the operation of various circuit topologies that are suitable for amplifcation of the ultrasound signal. In simulation I optimized operation of the circuit and determined the optimal values of the elements. In the simulation I measured voltage, current and power at each stage of the amplifer. Then I manufactured the PCB (printed circuit boards) with a KiCad program. In the circuit I separated the power section from the signals to eliminate an interference which might arise during operation of the switches and transformers used for powering the circuit. I performed measurements of the signal at the output stage using an oscilloscope. The operation of the circuit was tested at various frequencies with the connected ultrasonic transmitter, which has a resonant frequency declared at 350 kHz. I have found that it works best in the frequency range from 350 to 400 kHz, which was also expected if we look at the impedance characteristic of the transmitter. To capture the ultrasonic signal hydrophone detector is needed. Using the hydrophone RP 41 s, I measured the ultrasonic signal using an osciloscope. The developed amplifer worked as expacted providing max. 200 V at output resulting in an electrical power of 50 W using the Ultran GS350-D19-BNC-PK US transducer. The maximum measured ultrasound signal with hydrophone detector was 20 mV which translates to a US intensity of 5, 11 · 10^5 W/m^2.

• Keywords: Ultrasound amplifer, ultrasound transducer, ultrasound, push-pull topology.