AN-9736 Datasheet, PDF (1/13 Pages) Fairchild Semiconductor – Design Guideline of AC-DC Converter Using FL6961, FL6300A for 70W LED Lighting

www.fairchildsemi.com
AN-9736
Design Guideline of AC-DC Converter Using FL6961 &
FL6300A for 70W LED Lighting
Summary
This application note describes a design strategy for a Power
Factor Correction (PFC) circuit and higher-power
conversion efficiency using FL6961 and FL6300A. Based
on this design guideline and several functions of each
controller for LED lighting applications, a design example
with detailed parameters demonstrates the performance.
Introduction
Figure 1 shows the typical application circuit, with the BCM
PFC converter in the front end and the Quasi-resonant (QR)
flyback converter in the back end. FL6961 and FL6300A
achieve high efficiency with relatively low cost for
75~200W applications where BCM and QR operation with
a single switch shows best performance. BCM boost PFC
converter can achieve better efficiency with lower cost than
Continuous Conduction Mode (CCM) boost PFC converter.
These benefits result from the elimination of the reverse-
recovery losses of the boost diode and zero-voltage
switching (ZVS) or near-ZVS (also called valley switching)
of boost switch. The QR flyback converter for the DC-DC
conversion achieves higher efficiency than the conventional
hard-switching converter with valley switching.
The FL6961 provides a controlled on-time to regulate the
output DC voltage and achieves natural power factor
correction. The maximum on-time of the switch is
programmable to ensure safe operation during AC
brownouts. The FL6300A ensures thepower system
operates in quasi-resonant operation in wide range line
voltage and reduces switching loss to minimize switching
voltage in drain of the power MOSFET. To minimize
standby power consumption and improve light-load
efficiency, a proprietary Green-Mode provides off-time
modulation to decrease switching frequency and perform
extended valley voltage switching to keep to a minimum
switching voltage.
© 2011 Fairchild Semiconductor Corporation
Rev. 1.0.0 • 4/8/11
Figure 1. Typical Application Circuit
www.fairchildsemi.com