AN10754
SSL2101 and SSL2102 dimmable mains LED driver
Rev. 4.1 — 5 November 2012
Application note
Document information
Info
Keywords
Abstract
Content
LED, LED driver, mains, dimming, dimmable, LED lighting, LED lamp,
SMPS, SSL2101/2102, power conversion, flyback, power factor
This application note describes how to design a mains dimmable LED
driver using the NXP SSL2101/2102 LED Driver IC in flyback mode. It
includes a description of how mains dimmer compatibility is achieved
NXP Semiconductors
AN10754
SSL2101 and SSL2102 dimmable mains LED driver
Revision history
Rev
v.4.1
v.4
Date
20121105
20101122
Description
Update to
Figure 3 “Flyback equivalent circuits and waveforms (DCM mode)”
Fourth issue.
Modifications:
•
•
•
v.3
v.2
v.1
20091016
20091010
20090130
All illustrations updated to revised AQL standard.
Section 13 “Legal information”
updated.
Template updated to latest NXP template.
Third issue.
Second issue.
First issue.
AN10754
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 4.1 — 5 November 2012
2 of 37
NXP Semiconductors
AN10754
SSL2101 and SSL2102 dimmable mains LED driver
1. Introduction
Light Emitting Diodes (LEDs) have been used in electronic systems for many years,
primarily as indicator lights on electronic devices. Recent advances in terms of brightness
and available colors mean that LEDs can now be used in a wide range of applications -
from fun lighting in cell phones and media players to replacing conventional light sources
in commercial and domestic lighting applications.
Key enablers driving the expansion of LED lighting are the availability of high brightness
LEDs and intelligent LED controllers. Product designers incorporating high brightness
LEDs face many challenges. Among them are thermal management, driver
scheme/topology and existing infrastructure.
To replace an existing dimmable incandescent or halogen light source, an electronic lamp
driver system must be implemented that is compatible with the existing dimmer switch
while replicating the dimming behavior of the existing light source. The SSL2101/2102 IC
provide this functionality and, in addition, provides an efficient power converter. These are
the first ICs to combine these capabilities, enabling the lamp/module designer to integrate
electronics in a cost and size effective way, whilst benefiting from optimal thermal
trade-off.
AN10754
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 4.1 — 5 November 2012
3 of 37
NXP Semiconductors
AN10754
SSL2101 and SSL2102 dimmable mains LED driver
2. LED properties
LEDs need completely different types of driver to those used with incandescent or
halogen lamps. While incandescent lamps act as resistive loads with self stabilizing
properties, LEDs require a current source. The amount of light generated by an LED is
approximately proportional to the current flowing through the device. The voltage drop
across the device increases with current but decreases with temperature. In this respect,
LEDs behave like diodes. However, the voltage drop during operation (the forward voltage
or V
F
) is greater. This voltage drop is related to the amount of energy (eV) generated
when an electron is converted into a photon, and the amount of energy generated is
directly related to the color of the light. Additionally, V
F
can vary greatly between batches
due to production spread.
1500
I
LED
(mA)
0
2.9
V
F
(V)
4
019aaa413
Fig 1.
Typical LED curve (warm white)
2.1 Serial/parallel configuration
In most applications where LEDs replace existing lamps, multiple units need to be
connected to the driver since a single LED would not generate enough light. The LEDs
can be connected in series or in parallel.
If the LEDs are connected in series, the total voltage across the LED chain is equal to the
sum of the forward voltages (the current is the same in all the LEDs).
If LEDs are connected in parallel, the current is distributed among the branches. However,
because the forward voltage of an LED tends to fall as the temperature rises, this
configuration is intrinsically unstable. As the temperature rises, more and more of the
current generated will flow through the branches with the lower forward voltages - which
becomes brighter as the branches with the higher forward voltages get darker.
One reason for persisting with the parallel configuration (or a series-parallel combination),
is that it allows a large number of LEDs to be combined for a safe supply voltage. An
unacceptably high voltage would be needed to achieve the same degree of brightness
with a series configuration.
AN10754
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 4.1 — 5 November 2012
4 of 37
NXP Semiconductors
AN10754
SSL2101 and SSL2102 dimmable mains LED driver
The parallel configuration also offers the advantage of redundancy. If a single LED or
connection in a series-connected LED chain fails, resulting in an open circuit, the light will
go out in all the LEDs in the chain. This would not happen if the LEDs were connected in
parallel. With a parallel configuration, it is recommended that current regulation be added
at each branch to prevent thermal runaway and the unequal distribution of current and
light. In general, power converters operate at optimal efficiency when the difference
between output and input voltages is minimized. With mains powered drivers and LEDs,
optimizing this aspect will generate higher output voltages, allowing more LEDs to be
connected in series.
AN10754
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 4.1 — 5 November 2012
5 of 37
无线连接
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
