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Constant THD Class D Power Amplifier
Jirawath Parnklang,Panapong Laohawarit,Chaleampan Wangviwatana 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
This article presents a method to decrease a distortion from pulse width modulation (PWM) circuit that implemented in Class D amplifier circuit. The Classical method of PWM circuit uses only one frequency to modulate and demodulate. This method is a constant modulation ratio. The new method uses a microcontroller to get audio signal input and calculates the appropriate modulation ratio, then transfer the signal output to triangle pulse generator circuit to produce appropriate carrier signal for the modulation. The advantage is that carrier signal can be used at low frequency and the demodulation can be selected at the frequency very closed to input signal frequency. For this reason, the distortion of the transfer signal from PWM circuit to Class D amplifier circuit can be decreased. The simulation of classical PWM circuit and new PWM circuit using Simetrix program. Average of Distortion of the classical PWM is 4.297% and the one of the new PWM circuit is 0.004% respectively Total Harmonic Distortion. In conclusion, the result comply with the expected theory.