Improved Error Correction Methods for Filterless Digital Class D Audio Power Amplifier Based on FCLNF

This paper presents the design and implementation of a high-performance fully-digital PWM DAC and switching output stage which can drive a speaker in portable devices, including cellular phones. Thanks to the quaternary pulse-width modulation scheme, filter-less implementation are possible. A pre-modulation DSP algorithm eliminates the harmonic distortion inherent to the employed modulation process, and an oversampling noise shaper reduces the modulator clock speed to facilitate the hardware imp...

This paper presents a second-order pulsewidth modulation (PWM) feedback loop to improve power supply rejection (PSR) of any open-loop PWM class-D amplifiers (CDAs). PSR of the audio amplifier has always been a key parameter in mobile phone applications. In contrast to class-AB amplifiers, the poor PSR performance has always been the major drawback for CDAs with a half-bridge connected power stage. The proposed PWM feedback loop is fabricated using GLOBALFOUNDRIES' 0.18-μm CMOS process technology...

This paper presents a feed-forward power-supply noise cancellation technique to achieve high power-supply rejection ratio (PSRR) in single-ended class-D audio amplifiers. To show the effectiveness of the technique, it is implemented on a first-order single-ended pulse-width modulation (PWM) class-D amplifier. The implemented technique improves the PSRR from 20 Hz to 20 kHz independently of the close-loop compensator's filter-order. The design methodology, implementation, and tradeoffs for the pr...

A class-D amplifier with pulse code modulated (PCM) digital input is developed for a low-power digital hearing aid. A 16-bit 40-kbps PCM digital input is noise-shaped by a third-order digital sigma-delta modulator (SDM) which provides 1.5-bit digital output. The 1.5-bit digital output of the digital SDM is converted to a three-level analog signal by a simple digital-to-analog converter (DAC) and then applied to an analog SDM. The analog SDM provides pulse density modulated (PDM) signal to drive ...

An area-efficient pulsewidth modulation (PWM)-residual-aliasing reduction technique is proposed for Class-D audio amplifiers by utilizing a low-complexity feed-forward path to cancel the PWM high-frequency components inside the feedback loop. The proposed technique reduces the PWM-residual-aliasing distortion without increasing the required switching frequency or power-hungry controller circuits, thereby lowering both the quiescent current and total harmonic distortion plus noise (THD+N) in Clas...

In single-ended digital audio class D amplifiers (CDAs), the errors caused by power supply noise in the power stages degrade the output performance seriously. In this article, a novel power supply error correction method is proposed. This method introduces the power supply noise of the power stage into the digital signal processing block and builds a power supply error corrector between the interpolation filter and the uniform-sampling pulse width modulation (UPWM) lineariser to pre-correct the ...

This paper presents a fully integrated CMOS filterless class D amplifier that can directly hook up lithium battery in mobile application The proposed amplifier embodies a 2-order feedback path architecture instead of direct feedback of output to input of the integrator to decrease the high frequency intermodulation distortion associated with direct feedback and eliminate the integrator input common mode disturbance from the output in ternary modulation. The prototype class D amplifier realized i...

A high-performance class D audio amplifier using unipolar pulse-width-modulation (PWM) with double-sided natural sampling is presented in this article. In order to comprehend and design the system properly, the class D audio amplifier is modelled and analysed. A wide range triangle-wave signal with good linearity and magnitude proportional to supply voltage is embedded in the proposed class D audio amplifier for maximum output power, high power supply rejection ratio (PSRR) and low total harmoni...

This paper presents the technique to dynamically enhance the power efficiency of PWM class-D amplifier over a wide range of modulation indexes. The power stage of amplifier is segmented into several small stages and selectively enabled according to the power demand (i.e. modulation indexes). The capability of power delivery is dynamically adjusted to minimize the power loss in case of different modulation indexes improving the power efficiency, especially for small modulation index. The simulati...

A class-D audio amplifier for a digital hearing aid is described. The class-D amplifier operates with a pulsecode modulated (PCM) digital input and consists of an interpolation filter, a digital sigma-delta modulator (SDM), and an analog SDM, along with an H-bridge power switch. The noise of the power switch is suppressed by feeding it back to the input of the analog SDM. The interpolation filter removes the unwanted image tones of the PCM input, improving the linearity and power efficiency. The...