Markov Model Based Reliability Analysis of LED TVs on PFC Converters with Control Loop Effects

Abstract

The Power Factor Correction (PFC) converter is a crucial part of TVs, and it is responsible for supplying power to both the Light-Emitting Diodes (LEDs) backlight and the motherboard. While performing AC-DC conversion, the PFC converter also provides a feedback signal to the controller to maintain a high Power Factor (PF). A fault in the PFC control loop can lead to more stress and a higher failure rate in TVs. Thus, this paper quantifies the impact of PFC control loop faults on system reliability in LED TVs. An actual 175 W board used in the TVs is selected as the experimental platform, where specific points in the circuit are intentionally disconnected to analyze the effects of PFC control loop failure. The reliability analysis calculates the total failure rate and Mean Time to Failure (MTTF) using Markov approaches, with each electronic component’s failure rate referring to the FIDES (Fiabilité des Équipements Électroniques) methodology fault library. After analysis, the MTTF decreased from 13.8 years to 7.6 years under the same load of 65.1% when the control loop was accidentally shut down. Additionally, the junction temperatures of MOSFETs and diodes are determined through a thermal model to compare which device heats the most. Results indicate that the second stage of dc-dc converter switch heated the most, reaching around 72 °C. Finally, the validation of the system with and without the PFC part is conducted through experiments. © 1975-2011 IEEE.