Abstract

In this study, a digital primary-side controller for a flyback light-emitting diode driver with superior line regulation, high power factor (PF), and low total harmonic distortion (THD) was proposed. Conventional constant on-time control is hampered by input current distortion, leading to high THD. To achieve high PF and low THD, a digital switching frequency limiter with quasi-resonant control was proposed. In addition, owing to the turn-off delay of the MOSFET and propagation delay of the feedback signals, a primary-side-controlled flyback converter experiences poor line regulation. To achieve superior line regulation, delay compensation was proposed and analyzed. A digital controller was realized using a field-programmable gate array and was applied to an input voltage of 90– $264~V_{\mathrm {ac}}$ and an output current of 1 A in a hardware prototype to verify the feasibility of the proposed control solution. The experimental results indicate that line regulation was within ±3%, PF was higher than 0.95, and THD was lower than 5% at universal input voltage.

Highlights

  • LEDs have become the most popular lighting source for solid-state lighting

  • For low-to-moderate power applications, a flyback converter is widely used owing to its advantages of low cost, compact driver size, and straightforward topology

  • Considering the aforementioned issues, this study proposes a digital primary-side regulation (PSR) constant on-time (COT) flyback LED driver with quasi-constant frequency control, quasi-resonant (QR) control, and delay compensation

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Summary

INTRODUCTION

LEDs have become the most popular lighting source for solid-state lighting. According to (10), the output current ILED (t) is reflected to the primary side and can be estimated from three variables: conduction time Tdis (t) of diode D1, primary-side peak current Ip_pk (t), and switching cycle Ts (t). Based on the detection of Ip_pk [n], Tdis [n], and Ts [n], three signals are sent to the average current estimation block to calculate the average current over a switching cycle. The output current can be regulated accurately

DELAY COMPENSATOR
DIGITAL QUASI-CONSTANT FREQUENCY CONTROLLER
Findings
CONCLUTION
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