I. Introduction
AS THE demand for low-cost and low-power user-end audio products increases, traditional linear power amplifiers are progressively replaced by switching power amplifiers, referred to as class-D amplifiers or 1-bit digital switching amplifiers (DSAs). These 1-bit DSAs transform an analog audio input signal into a pulse signal controlling output power switches. Therefore, the losses due to quiescent currents are small compared to their linear counterpart, leading to higher power efficiency. Whereas the maximum theoretical power efficiency of a class-B audio amplifier is 78.6% [1], it reaches 100% for a DSA.