Design and Analysis of a Hybrid Inverting Buck Converter With 5 μs Response Time and 92.9% Efficiency for Micro-LED Displays

A hybrid inverting buck (HIB) DC-DC converter with adjustable negative output voltage is designed for micro-LED display applications. The HIB converter achieved a voltage conversion ratio (VCR) of -D and only needs three power switches, one flying capacitor, and one inductor, and brings the benefits of simple buck-like PWM control and a compact volume compared to the existing designs. HIB converter's losses and small-signal model are analyzed and compared with the inverting buck-boost (IBB) and Cuk converters. The proposed HIB converter enables smaller passive components and simplified compensation control with only one pair of complex poles. The advantages include continuous output current capability, fast load transient response, and low output voltage ripple. The converter was fabricated using a 180nm process, and the measured results show that the converter delivers a negative voltage output of -1 to -2V within an input voltage range of 3 to 4V. The converter achieves a transient response time of 5μs, a peak efficiency of 92.9%, a maximum load current of 2.2A, and a maximum voltage ripple of only 10mV.