AN-9738 Datasheet, PDF (1/25 Pages) Fairchild Semiconductor – Design Guideline on 150W Power Supply for LED Street Lighting Design Using FL7930B and FAN7621S

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AN-9738
Design Guideline on 150W Power Supply for LED
Street Lighting Design Using FL7930B and FAN7621S
Introduction
This application note describes a 150W rating design
guideline for LED street lighting. The application design
consists of CRM PFC and LLC SRC with high power factor
and high power conversion efficiency using FL7930B and
FAN7621S. To verify the validity of the application board
and scheme, a demonstration board 150W (103V/1.46A)
AC-DC converter was implemented and its results are
presented in this application note. In CRM active PFC, the
most popular topology is a boost converter. This is because
boost converters can have continuous input current that can
be manipulated with peak current mode control techniques
to force peak current to track changes in line voltage. The
FAN7930B is an active Power Factor Correction (PFC)
controller for boost PFC applications that operate in critical
conduction mode (CRM). Since it was first introduced in
early 1990s, LLC-SRC (series resonant converter) has
became a most popular topology because of its outstanding
performance in areas such as the output regulation of
switching frequency, ZVS capability for entire load range,
low turn-off current, small resonant components using the
integrated transformer, zero current switching (ZCS), and no
reverse recovery loss on secondary rectifier. Figure 1 shows
the typical application circuit, with the CRM PFC converter
in the front end and the LLC SRC DC-DC converter in the
back end. FL7930B and FAN7621S achieve high efficiency
with medium power for 150W rating applications where
CRM and LLC SRC operation with a two-stage shows best
performance. CRM boost PFC converters can achieve better
efficiency with light and medium power rating than
Continuous Conduction Mode (CCM) boost PFC
converters. These benefits result from the elimination of the
reverse-recovery losses of the boost diode and Zero-Current
Switching (ZCS). The LLC SRC DC-DC converter achieves
higher efficiency than the conventional hard switching
converter. The FL7930B provides a controlled on-time to
regulate the output DC voltage and achieves natural power
factor correction. The FAN7621S includes a high-side gate
driver circuit, accurate current-controlled oscillator,
frequency -limit circuit, soft-start, and built-in protections.
The high-side gate drive circuit has a common-mode noise
cancellation capability, which guarantees stable operation
with excellent noise immunity. Using Zero Voltage
Switching (ZVS) dramatically reduces switching losses and
significantly improves efficiency. ZVS also reduces
switching noise noticeably, which allows a small-sized
Electromagnetic Interference (EMI) filter.
Figure 1. Typical Application Circuit
© 2011 Fairchild Semiconductor Corporation
Rev. 1.0.0 • 4/20/11
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