An Analog Adaptive Gate Driver with Real- Time Miller Plateau Sensing for High Step-Up Flyback Converters

Portable battery-powered devices often need to boost a low-voltage battery source to a high-voltage DC bus of hundreds to thousands of volts, with step-up ratios from 20:1 to 100:1. At such extreme step-up ratios, compact MOSFET packages face an inherent trade-off between switching loss and electromagnetic interference (EMI). This paper proposes a multi-stage adaptive gate driver (MS-AGD) based on analog signal processing. The driver detects the Miller plateau in real time by differentiating the drain-source voltage and applying dual-threshold comparison. A cascode current mirror then generates a four-stage adaptive gate drive current, so that switching loss optimization and EMI control are decoupled into separate switching stages and handled independently. On a 5 W, 24-800 V flyback converter prototype, the MS-AGD reduces switching loss by 30% compared to a fixed gate-resistor drive scheme, achieving 94.5% efficiency at full load and improving light-load efficiency by 3.4 percentage points over the conventional approach, while lowering the device junction temperature by 0.79°C. The entire circuit is built with general-purpose discrete components at a bill-of-materials cost of $0.48 and a PCB footprint of only 13 times 14mm. It operates adaptively across a 12-48 V input voltage range and a 20-140 nC gate charge range without calibration.