517 KB21 KB198520251999Babič, RudolfBezjak, MarjanMilanovič, Miroštevilka:2letnik:29str. 79-84ISSN:0352-9045COBISSID:1577812URN:URN:NBN:SI:doc-Y71DDG53slStrokovno društvo za mikroelektroniko, elektronske sestavne dele in materialeInformacije MIDEMkonstruiranjemočnostna elektronikaojačevalnikipretvornikistikalaStikalni močnostni tonski ojačevalnik| Switching type audio power amplifier|A class-D amplifier which amplifies an analog input signal in the low frequency range from 10 Hz to 1000 Hz through pulse width modulation techniques is presented in this article. This frequency range which is only one part of audio frequency range is selected with active frequency switch. Class D amplifier can be easily explained in four stages; analog input stage, audio modulation stage, pulse width modulation power stage and low pass filtering stage. The audio modulation stage changes the analog input signal into a constant frequency, varying duty cycle. This operation is accomplished with integrated circuit SN3524. For power stage amplifier realization the experiences with DC-DC converters are used and for pulse width gain stage the DC-Dc Buck converter with continuous input current in bridge configuration is used. The mode of operation is very similar to switch mode power suppliers. The main goal for this decision is better power efficiency over Class-AB power amplifiers and its reduction in heat dissipation. This is in audio power amplifiers of great importance just at low frequencies. Design requirements are as follows; output volatge 28 V on the load resistance of 8 Ohms and the switching frequency is 150 KHz. The simulation and experimental results of frequency response are presented. In the expected frequency range the output power of 100 W is obtained at total harmonic distortion of 2,3% and power efficiency of 87%. The increasing of the output power up to 1000 W is possiblewithout difficultiesČlanek opisuje izvedbo tonskega ojačevalnika v stikalni tehniki za ojačanje signalov v nizkofrekvenčnem področju od 10 do 1000 Hz. Tako izvedbo ojačevalnika označujemo kot D razred delovanja, ki vsebuje štiri ločene stopnje: analogno vhodno stopnjo, pulzno širinski modulator, močnostnostikalno stopnjo in nizkoprepustno sito. Posebni poudarek je bil podan pri izvedbi močnostne izhodne stopnje, ki jo predstavlja mostični DC-DC pretvornik. Zanj smo uporabili študijo dinamičnega obnašanja z metodo povprečenja v prostoru stanj. Na podlagi te metode je ocenjena frekvenčna karakteristika izhodne stopnje, ki jo predstavljata mostično DC-DC pretvorniško vezje ter sito z bremenomTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaStrokovno društvo za mikroelektroniko, elektronske sestavne dele in materiale