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Switching ripple reduction in a class-D amplifier using a MOSFET in series with the filter capacitor

Goudswaard, J.C. (2019) Switching ripple reduction in a class-D amplifier using a MOSFET in series with the filter capacitor.

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Abstract:In high frequency PWM switching amplifiers, the output signal contains a ripple at the switching frequency. This research focuses on power efficient reduction of this ripple in an example class D audio amplifier with a second order output filter and a resistive load. In series with the filter capacitor, a MOSFET is placed. Since the study makes use of Simulink, a level 3 and a surface-potential based MOSFET model are examined. The level 3 model transition between triode and saturation region is discontinuous and the drain-source current is modelled as constant value in weak inversion. It was also found that the surface-potential based model lacks a body-diode. In the class D amplifier, the switching ripple at 0Vdc is examined. The voltage-current relations that exist in the filter capacitor are compared to those of the MOSFET. It was found that the MOSFET can only compensate between 12% and 20% of the values. This is due to the switching ripple having an integrating voltage-current relation, whereas the MOSFET has a linear relation. In time, the proposed solution can achieve complete reduction can only during 9% of the period. Concluding, the proposed solution is not a feasible way to reduce the switching ripple.
Item Type:Essay (Bachelor)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering BSc (56953)
Link to this item:http://purl.utwente.nl/essays/78917
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