AN-8033 Datasheet, PDF (1/16 Pages) Fairchild Semiconductor – Primary Side Regulated (PSR) Flyback Converter

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Application Note AN-8033
Design Guideline for Primary Side Regulated (PSR)
Flyback Converter Using FAN103 and FSEZ13X7
1. Introduction
More than half of the external power supplies are used for
portable electronics such as laptops, cellular phones, and
MP3 players and; therefore, have output voltage and
output current regulation capabilities for battery charging.
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 in an environment of
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 alleviating the burden of achieving
international energy efficiency regulations (California
Energy Commission (CEC) and Energy Star) in charger
designs. The primary-side regulation controls the output
voltage and current precisely with the information in the
primary side of the power supply only, not only removing
the output current sensing loss, but also eliminating all
secondary-feedback circuitry. This facilitates a higher
efficiency power supply design without incurring
tremendous costs. Fairchild Semiconductor PWM PSR
controller FAN103 and Fairchild Power Switch (FPS)
(MOSFET + Controller, EZ-PSR) FSEZ13X7 significantly
simplify the challenge of meeting tighter efficiency
requirements while eliminating external components.
FAN103 and FSEZ13x7 also have an integrated output
cable voltage drop compensation and external component
temperature variation compensation circuit, which allows
high accuracy even at the end of the output cable for
charger applications.
This application note presents practical design
considerations for battery chargers employing Fairchild
Semiconductor PWM PSR controller FAN103 and Power
Switch (MOSFET + Controller, EZ-PSR) FSEZ13X7. It
includes designing the transformer and output filter,
selecting the components, and implementing constant-
current / constant-voltage control. The step-by-step design
procedure described helps engineers design a power supply
more easily. The design procedure is verified through an
experimental prototype converter using FSEZ1317. Figure 1
shows the typical application circuit of primary-side
controlled flyback converter using FSEZ1317.
Figure 1. Typical Application Circuit of FSEZ1317
© 2009 Fairchild Semiconductor Corporation
Rev. 1.0.1 • 5/6/10
www.fairchildsemi.com