Title: High Accuracy Knee Voltage Detection for Primary-Side Control in Flyback Battery Charger
Authors: Yang, Shang-Hsien
Tsai, Tsung-Hsun
Chen, Hsin
Chiu, Chao-Chang
Chen, Ke-Horng
Lin, Ying-Hsi
Lin, Jian-Ru
Tsai, Tsung-Yen
College of Engineering
Keywords: Band-pass filter;knee voltage detection (KVD) technique;primary side regulator;snubber circuit
Issue Date: 1-Apr-2017
Abstract: In a primary-side control flyback charger, the accuracy of a conventional knee voltage detection (KVD) approach to obtain the output voltage is influenced by the inclusion of a snubber circuit. Although the snubber circuit dampens the ringing voltages due to switching, it also affect the resonance frequency which would reduce the timing of the sampling circuit, resulting in the inaccurate sampling of output voltage. By analyzing the snubber circuit and its resonance on the primary side, this paper implements a proposed accuracy knee voltage detection (AKVD) technique to compensate for the induced resonance frequency. Furthermore, the proposed constant current (CC) regulator ensures the accuracy of CC mode by compensating the sensing current error caused by the switching delay of the power transistor. A prototype consisting of a test chip fabricated with a 0.5 mu m BCD process demonstrates a voltage accuracy exceeding 99.63%. This is achieved by mitigating abnormal detections and thus ensuring correct control of charging current throughout the charging period.
URI: http://dx.doi.org/10.1109/TCSI.2016.2624743
ISSN: 1549-8328
DOI: 10.1109/TCSI.2016.2624743
Volume: 64
Begin Page: 1003
End Page: 1012
Appears in Collections:Articles