Design of Digital Robust Controller for a Class-D Amplifier Using A2DOF

AbstractIn recent years, it is desired that the bandwidth of a class-D amplifier is widened using sampling frequencies as low as possible. For example, it is expected in the application of the power supply of a low frequency immunity test, or an audio power amplifier, or the power amplifier of vibration generator. In this paper, it is shown that the bandwidth of the class-D amplifier can be widened to 20[kHz] by an A2DOF (Approximate 2-Degree-Of-Freedom) digital controller with 500[kHz] sampling frequencies. The controller is implemented by a DSP (digital signal processor). It is shown from experiments that 20[kHz] bandwidth can be maintained even if load changes

A Single-Stage LED Driver Based on ZCDS Class-E Current-Driven Rectifier as a PFC for Street-Lighting Applications

This paper presents a light-emitting diode (LED) driver for street-lighting applications that uses a resonant rectifier as a power-factor corrector (PFC). The PFC semistage is based on a zero-current and zero-derivative-switching (ZCDS) Class-E current-driven rectifier, and the LED driver semistage is based on a zero-voltage-switching (ZVS) Class-D LLC resonant converter that is integrated into a single-stage topology. To increase the conduction angle of the bridge-rectifier diodes current and to decrease the current harmonics that are injected in the utility line, the ZCDS Class-E rectifier is placed between the bridge-rectifier and a dc-link capacitor. The ZCDS Class-E rectifieris driven by a high-frequency current source, which is obtained from a square-wave output voltage of the ZVS Class-D LLC resonant converter using a matching network. Additionally, the proposed converter has a soft-switching characteristic that reduces switching losses and switching noise. A prototype for a 150-W LED street light has been developed and tested to evaluate the performance of the proposed approach. The proposed LED driver had a high efficiency (>91%), a high PF (>0.99), and a low total harmonic distortion (THD i <; 8%) under variation of the utility-line input voltage from 180 to 250 V rms . These experimental results demonstrate the feasibility of the proposed LED scheme