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

Abstract

The paper presents an original architecture andimplementation of 9-bit Linearized Pulse Width Modulator(LPWM) for Class-BD amplifier, based on the hybrid methodusing STM32 microcontroller and Programmable Tapped DelayLine (PTDL). The analog input signals are converted into 12-bitPCM signals, then are directly transformed into 32-bit LBDDDPWM data of the pulse-edge locations within n-th period of theswitching frequency, next requantized to the 9-bit digitaloutputs, and finally converted into the two physical trains of 1-bitPWM signals, to control the output stage of the Class-BD audioamplifier. The hybrid 9-bit quantizer converts 6 MSB bits usingcounter method, based on the peripherals of STM32microcontroller, while the remaining 3 LSB bits - using a methodbased on the PTDL. In the paper extensive verification ofalgorithm and circuit operation as well as simulation inMATLAB and experimental results of the proposed 9-bit hybridLBDD DPWM circuit have been performed. It allows to attainSNR of 80 dB and THD about 0,3% within the audio baseband