AN11041
SSL21081, SSL21083, and SSL2109 non-dimmable buck
converter in low ripple configurations
Rev. 1.3 — 23 October 2012
Application note
Document information
Info
Keywords
Abstract
Content
SSL21081, SSL21083, SSL2109, buck converter, down converter, driver,
topology, AC/DC, retrofit SSL, LED
This document describes how to design a buck converter in low ripple
configuration, using the SSL21081, the SSL21083 or the SSL2109 driver
platform for non-mains dimmable LED applications. It also illustrates the
method of calculating components for such applications.
NXP Semiconductors
AN11041
Non-dimmable buck converter in low ripple configuration
Revision history
Rev
v.1.3
v.1.2
v.1.1
v.1
Date
20121023
20110701
20110512
20110504
Description
fourth issue
third issue
second issue
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
AN11041
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1.3 — 23 October 2012
2 of 23
NXP Semiconductors
AN11041
Non-dimmable buck converter in low ripple configuration
1. Introduction
The SSL21081, the SSL21083, and the SSL2109 platforms are specially defined to
address the retrofit SSL application market. The platforms are optimized for use in
cost-effective, high-efficiency driver solutions for high voltage LED strings or LED
modules. The buck converter is one of the most commonly used Switch Mode Power
Supply (SMPS) topologies.
This application note discusses the general principles and considerations to be
addressed, when designing a buck converter using an IC from the SSL21081, the
SSL21083, or the SSL2109 platform. These drivers operate in Boundary Conduction
Mode (BCM) using peak current control and valley detection for efficient converter on-off
switching.
Further information regarding design tools can either be found on the www.nxp.com
product page for the specific SSL21081, SSL21083, or SSL2109 IC or is available
through your local sales office.
Remark:
All voltages unless otherwise specified are in V (DC).
1.1 Type number overview
The SSL21081, the SSL21083, and the SSL2109 platforms are available in two packages
with each two variants.
Table 1
shows the market segment that each variant is intended to
be used in.
Table 1.
Type
SSL21081T
SSL21081AT
SSL21083T
SSL21083AT
SSL2109T
SSL2109AT
SO8
100 to 230
external
SO8
230
600 V; 50
SSL21081, SSL21083, and SSL2109 type number overview
Package Nominal mains
(V (AC))
SO8
100 to 120
MOSFET characteristics
300 V; 20
SWP
yes
no
yes
no
yes
no
2. Basic theory of operation
Before going into detail about the SSL21081, SSL21083, and SSL2109 applications, it is
important to have a basic knowledge of buck converters.
The operation of the buck converter can consist of an inductor and a switch control the
inductor input current. It alternates between connecting the inductor to source voltage to
store energy in the inductor and discharging the energy into the load.
More detailed information about this principle is given in the general application note
“Buck converter for SSL applications” (AN10876)
(see
Ref. 1).
More detailed information about external MOSFET design considerations are described in
the application note
“SSL2109T/AT/SSL2129AT controller for SSL applications”
(AN11136)
(see
Ref. 4).
AN11041
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1.3 — 23 October 2012
3 of 23
NXP Semiconductors
AN11041
Non-dimmable buck converter in low ripple configuration
3. Functional description
The SSL21081, the SSL21083, and the SSL2109 are Multi-Chip Modules (MCM)
available in the SO8 package. The SSL21081 and SSL21083 variants have an integrated
switch.The SSL2109 required an external switch. Regardless of the switch, the main
difference between the variants, is the maximum voltage of the internal MOSFET switch
and SWP. See
Table 1
and
Table 2
for the specifics of each IC.
The SSL21081, SSL21083, and SSL2109 families of ICs provide the following features:
•
Switch-mode buck controller with power-efficient boundary conduction mode of
operation with:
–
No reverse recovery losses in freewheel diode
–
Zero Current Switching (ZCS) for turn-on of switch
–
Zero voltage or valley switching for turn-on of switch
–
Minimum inductance value and size for the inductor
•
High Power Factor (> 0.9) applicable (SSL2109AT only)
•
Direct Pulse-Width Modulation (PWM) dimming possible
•
Fast transient response through cycle-by-cycle current control:
–
Prevents overshoots or undershoots in the LED current
•
Internal Protective functions:
–
UnderVoltage LockOut protection (UVLO)
–
Leading Edge Blanking (LEB)
–
OverCurrent Protection (OCP)
–
Short Winding Protection (SWP; SSL21081T, SSL21083T, SSL2109T)
–
Internal OverTemperature Protection (OTP)
–
Brownout protection
–
Output short-circuit protection
–
Easy external temperature protection using an NTC resistor
Further details and full specifications can be found in the
SSL21081_SSL21083 and
SSL2109_SER data sheets
(Ref.
2, Ref. 3).
Table 2.
Symbol
SSL21081, SSL21083
HV
SOURCE
VCC
NTC
DVDT
GND
DRAIN
1
2
3
4
5
6, 7
8
high-voltage supply pin
low-side internal switch
supply voltage
LED temperature protection input
AC supply pin
ground
high-side internal switch
Pin description
Pin (SO8)
Description
AN11041
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1.3 — 23 October 2012
4 of 23
NXP Semiconductors
AN11041
Non-dimmable buck converter in low ripple configuration
Pin description
…continued
Pin (SO8)
1
2
3
4
5
6
7
8
Description
high-voltage supply pin
supply voltage
temperature protection input
low-side external switch
driver output
AC supply pin
ground
high-side external switch
Table 2.
Symbol
SSL2109
HV
VCC
NTC
SOURCE
DRIVER
DVDT
GND
DRAIN
4. Step-by-step design procedure
This section provides a step-by-step guide for designing a basic buck converter
application using the SSL21081, the SSL21083, or the SSL2109.
Remark:
The derivation of the equations applied is beyond the scope of this application
note. Where values used in formulas are application specific, reasonable estimates have
been made.
4.1 Basic configuration
A typical buck application in low-ripple configuration for the SSL21081 and SSL21083
platforms, driving a single LED chain, is shown in
Figure 1.
The mains voltage is rectified, buffered and filtered in the input section and connected via
the LED string through the inductor to the DRAIN pin of the SSL21081 and SSL21083.
When the internal MOSFET is switching, the stored energy in L2 modulates the current
through the LED chain. During the primary stage (1), the current through the inductor is
sensed by R1 and when V
th(ocp)SOURCE
is reached on the SOURCE pin, the internal
MOSFET is switched off and the secondary stage (2) starts.
The internal MOSFET switch is only switched on when it detects that no current is flowing
through the inductor by detecting a valley on the DRAIN pin. This system is called Valley
Detection and reduces the switching losses significantly (see
Section 4.4).
AN11041
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Application note
Rev. 1.3 — 23 October 2012
5 of 23
嵌入式系统
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
