AN-6747 Datasheet, PDF (1/12 Pages) Fairchild Semiconductor – Control a Flyback Power Supply with Peak Current Output

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AN-6747
Applying FAN6747 to Control a Flyback Power Supply with
Peak Current Output
1. Introduction
Highly integrated PWM controller, FAN6747, is optimized
for applications with motor load, such as printers and
scanners, that inherently impose some kind of overload
condition on the power supply during acceleration mode.
FAN6747 provides a two-level OCP function that allows the
SMPS to stably deliver peak power during the motor
acceleration without causing premature shutdown, while
protecting the SMPS from overload condition.
Green-mode and burst-mode functions with a low operating
current maximize the light-load efficiency so that the power
supply can meet stringent standby power regulations.
The frequency-hopping function reduces electro-magnetic
interference (EMI) of a power supply by spreading the
energy over a wider frequency range. The constant power
limit function minimizes the component stress in abnormal
condition and helps optimize the power stage. Protection
functions such as OCP, OLP, OVP, and OTP are fully
integrated into FAN6747, which improves the SMPS
reliability without increasing system cost.
This application note presents design considerations to
apply FAN6747 to a flyback power supply with peak load
current profile. It covers designing the transformer, selecting
the components, and closing the feedback loop. Figure 1
shows a typical application circuit using FAN6747.
Figure 1. Typical Application
© 2010 Fairchild Semiconductor Corporation
Rev. 1.0.1 • 9/16/10
www.fairchildsemi.com