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Analyzing and reducing switching frequency ripple of class D amplifiers by active filtering

Knol, E.J. (2018) Analyzing and reducing switching frequency ripple of class D amplifiers by active filtering.

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Abstract:A class D amplifier creates, next to the desired signal, also a PWM frequency ripple at the output. This ripple can radiate from the speaker wires as electromagnetic radiation, which is undesirable. Feedback models are designed to reduce the amplitude of the output ripple and the magnitude at 620 kHz (lowest ripple frequency). In this report, two feedback models are analyzed and optimized. One feedback model from the output voltage to a controlled current source and another feedback model from the inductor voltage to a controlled current source. The feedback models use a first or second order high pass filter. Both options are analyzed and optimized for each feedback model. All models reduce the output ripple voltage, except the feedback model from the output voltage with a first order high pass filter. The best feedback model is the model with feedback from the inductor voltage with a second order high pass filter, which reduced the output voltage ripple amplitude from 60.8 mV to 4.65 mV (reduction of 92.4\%) and the magnitude at 620 kHz (lowest PWM frequency) from -53.7 dB till -87.8 dB (decrease of 64.7\%).
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/75281
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