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Diplomarbeit 2005 (DA05): Arbeits-Archiv
 
DA Ltt 05/2 - Novel, simple ac-step-up-converter
Studierende: Thomas Buhler, buhletho
  Andreas Heller, helleand

Betreuer: Jakob Lattmann, latj

The novel, simple ac-step-up-converter has an automatic net recognition and voltage adjustment. The aim is to operate equipment world-wide, produced in Europe for 230 V and an achievement of up to 500 W, with the help of the ac-step-up-converter. The voltage converter converts an ac-single-phase voltage from between 85 V and 146 V to 230 V. Thereby has the output voltage the same frequency as the feeding voltage. The simulation shows that the converter functions perfectly both with ohmic and inductive load and with capacitive load. A maximum efficiency is reached by 88.2% (R-load). The power factor is likewise load-sensitive and amounts to at best 98.4% (RL-load). The ac-step-up-converter is based on the principle of the DC-Boost-Converter. Two bi-directional switches clock the converter with 20 kHz. Thanks to an innovative circuit a switch can be realized with only one IGBT. The control of the IGBT's is made by pulse width modulation (PWM) by a PIC-Microcontroller. For switching on, a zero crossover of the entrance ac-voltage is detected. Thus the start-up peak current can be reduced to a minimum. A control algorithm (PI-Regulation) changes the duty cycle of the PWM signal between 30 and 62%, so that the output voltage is always held on 230 V. The PI-Regulation reaches 220 ms after switching on 230 V without overshooting.

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