AN11411
SSL3401HN dimmable driver for MR16/12 V GU5.3
Rev. 1 — 23 January 2014
Application note
Document information
Info
Keywords
Abstract
Content
dimmable MR16 lamps, SL3401HN low-voltage LED driver
This application note describes how to design an MR16 low voltage LED
driver using the NXP Semiconductors SSL3401 LED driver IC.
NXP Semiconductors
AN11411
SSL3401HN dimmable driver for MR16/12 V GU5.3
Revision history
Rev
v.1
Date
20140123
Description
first issue
Contact information
For more information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
AN11411
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2014. All rights reserved.
Application note
Rev. 1 — 23 January 2014
2 of 26
NXP Semiconductors
AN11411
SSL3401HN dimmable driver for MR16/12 V GU5.3
1. Introduction
Light Emitting Diodes (LEDs) have been used in electronic systems for many years,
primarily as indicator lights on electronic devices. Recent developments in terms of
brightness and available colors have made it possible to use LEDs in a wide range of
applications. These include lighting in cell phones, media players, and replacing
conventional light sources in commercial and domestic lighting applications.
The key enablers driving the expansion of LED lighting are the availability of
high-brightness LEDs and intelligent LED controllers. Product designers who incorporate
high-brightness LEDs face many challenges, like thermal management, driver
scheme/topology and existing lamp shape and regulation compliancy. The optimized lamp
shape ensures that a low-component application BOM is required for building the
application.
The SSL3401 offers hysteretic control for the power converter. It is suitable for use with a
linear LED current source. Two embedded Proportional-Integral (PI) controllers and a
0.052 % resolution Pulse-Width Modulation (PWM) generator, adjusted by the dimmer
conduction phase, ensure excellent LED current stability for a dimming range from 100 %
to less than 5 %. The power loss across the LED current source is also minimized.
The SSL3401 enables the low-voltage lamp/module designer to produce an LED driver
that:
•
•
•
•
•
•
•
Eases migration to an existing lighting control infrastructure
Supports most available dimming and low-voltage transformation solutions
Provides excellent stability of LED current
Enhances the line regulation of the LED current
Optimizes the dimming curve for low-voltage transformer compatibility
Operates with 50 Hz, 60 Hz or DC sources
Provides protections like OverVoltage Protection (OVP), shorted LED protection and
opened LED protection
AN11411
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2014. All rights reserved.
Application note
Rev. 1 — 23 January 2014
3 of 26
NXP Semiconductors
AN11411
SSL3401HN dimmable driver for MR16/12 V GU5.3
2. Hysteretic boost basics
The operation of the boost converter is relatively simple. It incorporates an inductor and
two switches that control the inductor input current. The converter changes between
connecting the inductor to the source voltage to store energy in the inductor and
discharging the inductor into the load.
Figure 1
shows a simplified application diagram of a boost converter connected to a
voltage supply and a load. For a basic understanding of the application, VI (supply
voltage) and VO (load voltage) can be regarded as DC. In a practical application, a
MOSFET or a bipolar transistor replaces switch S1. A diode replaces switch S2.
Fig 1.
Basic configuration circuit
The state of the switches defines the circuit. With two switches, there are four modes. But
not all of them are applicable. Modes 1 and 2 are the most important modes and nearly
always present. Mode 3 is only present in Discontinuous Conduction Mode (DCM). Mode
4 must be prevented, since it would short circuit the supply.
Table 1
shows the state of the
switches in modes 1 to 4.
Table 1.
Mode
1
2
3
4
Possible modes of operation
S1
closed
open
open
closed
S2
open
closed
open
closed
Duration
t1
t2
t3
n/a
Figure 2
briefly explains the operation of the boost converter. It shows the equivalent
circuit diagrams for the first two modes when working in Continuous Conduction Mode
(CCM). Simplified waveforms are also shown for one complete switching cycle.
AN11411
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2014. All rights reserved.
Application note
Rev. 1 — 23 January 2014
4 of 26
NXP Semiconductors
AN11411
SSL3401HN dimmable driver for MR16/12 V GU5.3
a. Equivalent circuits
Fig 2.
b. Waveforms
Boost wave forms in Continuous Conduction Mode (CCM)
During the time
t1
(Mode 1), switch S1 is closed (switched on). Current starts to flow
through inductor L. When switch S1 is switched off, the secondary switch (S2) is closed
and a current flows towards the output. During the conduction time of switch S2 (t2), the
current in the inductor is reduced. If the next step (t1
(n+1)
) begins (after step
t2
(n)
) before
the inductor current has dropped to 0 A, the application operates in Continuous
Conduction Mode (CCM). The input power equals the input voltage multiplied by the
average inductor current (I
L(AV)
). The resulting input current ripple varies also with the
comparator delay, the inductance value and the parasitic capacitances.
AN11411
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2014. All rights reserved.
Application note
Rev. 1 — 23 January 2014
5 of 26
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