Quasi-Resonant Flyback Converter as Auxiliary Power-Supply of an 800 V Inductive-Charging System for Electric Vehicles

Abstract

This paper presents evaluation of quasi-resonant flyback (QRF) dc-dc converter 57 W with valley-switching in an emerging application. The QRF was supplied from an 800 V variable dc-link and was used as the auxiliary power-supply of a wireless inductive-charging system (ICS). Comparison of stateof-the-art QRF control ICs is presented and suggestions for their improvements are given. Notes on the power-supply architecture, design items specific for the ICS application, over-power protection, and keycomponent choice are provided. During experiments several original and novel results are generated. The efficiency graphs in ICS power transfer, ICS stand-by, and constant-load operation are analyzed. The maximum efficiency of 87.1 % was reached at 620 V and rated load. Moreover, the unique analysis of QRF losses at no-load, showed their quadratic dependency vs. input-voltage. The measured "switching frequency vs. load" graph is presented. It was changeable with load and input-voltage as expected. From Bode plots the bandwidth, phase-margin, and gain-margin are extracted and plotted versus input-powerfor the first time. They were changeable with input-voltage and load as expected. Comparison of simulated and measured Bode plots showed that, even when they were not matched, one can design a Type-2 compensator that ensures stable operation. Evaluation of cross-regulation, when output with 24.1 % of total power was regulated, showed that such approach-contrary to the more common of regulating the biggest one-is feasible too. It is discovered that, for a QRF with variable switching frequency, choice of compensator or the regulated output has influence on its efficiency. The power-thresholds to ensure valleyswitching operation represented as "input power vs. input voltage" are shown for the first time. Comparison of bandwidth, phase margin, and gain margin vs. input power, between an ACF and the QRF, were discussed. Conclusion is that QRF, for the same specification, cannot have the same compensator as an ACF. The difference must be at least in a placement of a zero.

A Comparative Study of Cutting-Edge Bi-Directional Power Converters and Intelligent Control Methodologies for Advanced Electric Mobility

“…A comparison of the simulation and measurement results indicated that Type-2 compensation can ensure stable operation. The study determined that compensation and regulated output selection influence the Quasi-Resonant Flyback (QRF) converter efficiency at varying switching frequencies [26].…”

Design and development of variable frequency modulation-based isolated DC–DC converter with green mode of operation

“…These converters are having high efficiency than normal flyback converter. A wireless inductive charging system utilized the quasi resonant frequency (QRF) as an auxiliary power source, which was powered by an 800V variable dc-link source [10]. Because of the leakage inductance of transformer there is a problem of ringing effect in these isolated converters, so active clamp and passive clamp techniques are used and simulated.…”

Quasi-Resonant Flyback Converter in an 800 V Inductive Charging System: Abnormal Operation and Control Aspects

“…Majority of literature was covering, e.g., power conversion, efficiency improvements, compensation techniques, control, coil design, protection methods, etc. [4]. The first publications that were covering auxiliary power supplies (APS) of the primary, i.e.…”

“…ground, side of ICS were [5], [6], [7], [8], [9]. In [5]- [9] the active-clamped flyback (ACF) dc-dc converter was used as an APS whilst in [4] the quasi-resonant flyback (QRF) dc-dc converter was analyzed.…”

“…The detailed description of the 11 kVA ICS from BRUSA, where those APS were used, are given in [10] and [11].…”