An Adaptive Constant Voltage Control Scheme for Primary-Side Controlled Flyback Converter
Yongyuan Li, Qiang Wu, Lianxi Liu, Zhangming Zhu
Abstract
An adaptive multimode constant voltage (CV) control scheme for primary-side regulation flyback converters operating in discontinuous conduction mode and continuous conduction mode operation is presented, which significantly enhances the light-load efficiency and thereby the overall average efficiency. Compared to conventional control scheme, the proposed control scheme performs analog control approach to integrate multiple operating modes adaptively based on load conditions. Besides, line voltage compensation and freewheeling diode compensation are proposed to improve the CV precision operating in multiple modes. The proposed adaptive multimode control scheme is implemented in 0.18 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m 5 V/40 V BCD process and occupies a die size (with pads) of 1.05×0.8 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The experimental results show that the average efficiency is 88.52% under 265 Vac, whereas peak efficiency can reach 89.65% under 265 Vac. The deviation of the output voltage is within ± 2.33%.