A High-Efficiency QR Flyback DC–DC Converter with Reduced Switch Voltage Stress Realized by Applying a Self-Driven Active Snubber (SDAS)

Abstract

In this paper, a QR flyback converter using a self-driven active snubber (SDAS) was proposed to solve the problem of voltage surge in the switch of QR flyback converters. In the proposed converter, the SDAS consisting of a clamping capacitor and an active switch can be configured in parallel with the main switch or transformer to reduce the voltage surge in the switch. To confirm the steady-state characteristics of the QR flyback converter to which the proposed SDAS is applied, equivalent circuits for each state were constructed, and the equations and characteristics for each state were determined. A 60 W class small AC–DC adapter was constructed to confirm the effectiveness of the proposed converter and the control circuit method, and the experimental results were analyzed. The size of the experimental AC–DC adapter was 74×29×23 mm, and it had a high power density of 20 W/in3 or more. The experimental circuit was limited to the high power conversion efficiency of up to 91.56%, and the maximum voltage surge in the switch was approximately 450 V. One of the reasons for such high efficiency is the SDAS circuit, which sufficiently reduces the voltage surge of the QR flyback switch, compared with the RCD clamp circuit, and does not consume power in principle.

Analysis and Optimization of a Regenerative Snubber for a GaN-Based USB-PD Flyback Converter

“…There is a large interest in improving the efficiency of Flyback converters, characterized by a wide input voltage range and a variable input and output voltage due to its wide applications [1][2][3][4]. To this aim, several non-dissipative clamp circuits, passive [5,6] and active [7][8][9][10], have been proposed and optimized over the years to limit the voltage spikes on the main switch, typically a power MOSFET, due to the transformer leakage inductance and optimized to not excessively affect the overall efficiency system [11]. A regenerative solution has been proposed in the work presented in [12] as an improvement of the nondissipative passive LCD solution, replacing the snubber inductance with further winding in the transformer; this solution has been widely used in applications to increase the efficiency and power density of the converter [13].…”