Low Power and Low Distortion Filterless Class D Power Amplifier
|關鍵字:||D類放大器;功率放大器;音頻;Class D Amplifier;Power Amplifier;Audio|
Amplifiers play an important role in the audio system. Class-AB amplifiers seem to be the dominative design in recent markets. Compared by power efficiency, Class-D power amplifiers have better performance than Class-AB amplifiers. It is based on the fact that Class-D power amplifiers use the switching operation to fully turn on or off the transistors. Class-D power amplifiers have less power dissipation than Class-AB amplifiers. The focus on this thesis is to develop the modulation of Class-D amplifiers with high power efficiency. This circuit is different from the traditional H-bridge Class-D power amplifier. It has improved the shortcoming of the traditional Class-D power amplifier with too big signal distortion, but not make the power efficiency diminished at the same time. The addition of the feedback system can improve the shortcoming； this is a technology that can reduce noise. And the circuit is realized by changing the way of the Pulse Width Modulation（PWM） method. In addition, this circuit has another advantage that it eliminates the Class-D output filter. This technology can reduce the area of the circuit and can improve power efficiency at the same time. This circuit was fabricated by TSMC 0.35mμ 2P4M（Mixed－Signal）process. It includes two error amplifiers, two comparators, triangular wave generator, buffer, gate-driver, and H-bridge. The Class-D power amplifier has the input sinusoidal-wave frequency of 2 KHz, the amplitude of 0.7 V. It is operated at 250 KHz with the cutoff frequency of 20 KHz. The result shows the power efficiency of 85%, the Total Harmonic Distortion is 0.12%, and the power dissipation is about 12.57 mW. All the modulation simulations are shown in this thesis, and we can obviously compare their advantages and disadvantages. If THD＜1％ is desired, then it is better to choose the amplitude of the input signal to be within 0.7 times of the carrier wave. In fact, the power efficiency of Class-D power amplifier is about 85％ to 95％ generally. If we still would like to increase the power efficiency, the tradeoff is between the power efficiency and the chip area.
|Appears in Collections:||Thesis|
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