www.fairchildsemi.com
AN-9741
Design Guideline for LED Lamp Control Using Primary-
Side Regulated Flyback Converter, FL103M
Introduction
Many LED lamp systems use the flyback converter
topology. In applications where precise output current
regulation is required, current sensing in the secondary side
is always necessary, which results in additional sensing loss.
For power supply designers struggling to meet increasing
regulatory pressures, the output current sensing is a daunting
design challenge.
Primary-Side Regulation (PSR) for power supplies can be
an optimal solution for compliance and cost in LED lamp
systems. Primary-side regulation controls the output voltage
and current precisely with information in the primary side of
the LED lamp controller only. This removes the output
current sensing loss and eliminates secondary-feedback
circuitry. This facilitates a higher efficiency power supply
design without incurring tremendous costs. Fairchild’s
PWM PSR controller FL103M simplifies meeting tighter
efficiency requirements with few external components.
This application note presents design considerations for
LED lamp systems employing Fairchild Semiconductor
components. It includes designing the transformer and
output filter, selecting the components, and implementing
constant-current control. The step-by-step procedure
completes a power supply design. The design is verified
through an experimental prototype converter using FL103.
Figure 1 shows the typical application circuit for an LED
lamp using FL103M.
Figure 1. Typical Application Circuit
© 2011 Fairchild Semiconductor Corporation
Rev. 1.0.0 • 6/27/11
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