Linearized 9-Bit Hybrid LBDD PWM Modulator for Digital Class-BD Amplifier

Abstract

The paper presents an original architecture and
implementation of 9-bit Linearized Pulse Width Modulator
(LPWM) for Class-BD amplifier, based on the hybrid method
using STM32 microcontroller and Programmable Tapped Delay
Line (PTDL). The analog input signals are converted into 12-bit
PCM signals, then are directly transformed into 32-bit LBDD
DPWM data of the pulse-edge locations within n-th period of the
switching frequency, next requantized to the 9-bit digital
outputs, and finally converted into the two physical trains of 1-bit
PWM signals, to control the output stage of the Class-BD audio
amplifier. The hybrid 9-bit quantizer converts 6 MSB bits using
counter method, based on the peripherals of STM32
microcontroller, while the remaining 3 LSB bits - using a method
based on the PTDL. In the paper extensive verification of
algorithm and circuit operation as well as simulation in
MATLAB and experimental results of the proposed 9-bit hybrid
LBDD DPWM circuit have been performed. It allows to attain
SNR of 80 dB and THD about 0,3% within the audio baseband.