參數(shù)資料
型號(hào)： SSL2102
廠商： NXP Semiconductors N.V.
中文描述： Demoboard description SSL2102 12W-230V Triac dimmable fly-back demonstration board The SSL2102 is a Switched Mode Power Supply (SMPS) controller IC that operates in combination with a phase cut dimmer directly from rectified mains. It is designed to drive LED devices. Our SSL2102 demonstration boards are suitable for 120 V or 230 V mains.
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代理商： SSL2102
AN10876
All information provided in this document is subject to legal disclaimers.
NXP B.V. 2011. All rights reserved.
Application note
Rev. 2 — 23 June 2011
12 of 29
NXP Semiconductors
AN10876
Buck converter for SSL applications
4.4 Peak current limit
In the example schematic (see
Figure 3
), resistor R5 limits the peak current. When the
voltage level over this resistor reaches a threshold, the cycle will stop and the switch will
stop conducting. This threshold can be used to control peak current. Using peak current
control, the LED current is half the peak current in BCM mode. The tolerance on this
detection is proportional to the tolerance on the LED current. The value of R5 is calculated
using the threshold level V
ocp
in
Equation 20
.
(20)
Example: If I
peak
= 1.48 A and V
ocp
= 0.52 V then R5 = 0.35
.
4.5 Ripple current calculation
Capacitor C5 filters the current through the LEDs so that it will approach the average
current through the inductor. The remaining variation is known as ripple and can be
expressed as a percentage of the average current. If the current waveform is symmetrical,
which is the case for buck converters, the ripple current is also symmetrical.
Equation 21
provides an approximation of the ripple current.
(21)
In
Equation 21
, R
dyn
is the differential resistance of the LED string at the average rated
current. This value is derived by taking the tangent of the UI graph as provided in the data
sheet for the LED. This must not be confused with the division between voltage and
current at the point of operation of the LED.
Example: Ten LED's are used in series and are driven at 100 mA. Each LED has a
dynamic resistance of 1
, resulting in a total dynamic resistance of 10
. With a ripple of
5 % and a frequency of 100 kHz, C5 will be 3.18
F. Use 3.3
F.
or, alternatively,
One LED is used at 1 A. It has a dynamic resistance of 0.1
. With a ripple of 1% and a
frequency of 100 kHz, C5 will be 1.6 mF.
The value calculated using this formula is intended to filter ripple current caused by
converter operation. It is not intended to filter current variation due to input voltage
fluctuations. The input voltage ripple often has an amplitude that does not allow the linear
approximation as used in
Equation 21
, especially when rectifying and buffering 50 Hz or
60 Hz mains voltage. For mains buffer calculations, use
Equation 22
.
(22)
where:
P
tot
= P
in
+ IC losses. C3 + C4 is equal to the input buffer capacity
R
5
V
I
peak
-----------
=
C
5
2
-----------
f
Ripple
%
R
dyn
----------------------------------------------
=
C3
C4
+
2
P
t
V
mainspeak
V
buff min
2
–
-----------------------------------------------------------
=
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
SSL2102DB/17W120V,598 功能描述:LED 照明開(kāi)發(fā)工具 17W 120V dimmable LED Drvr RoHS:否 制造商:Fairchild Semiconductor 產(chǎn)品:Evaluation Kits 用于:FL7732 核心: 電源電壓:120V 系列: 封裝:
SSL2102T/DB/FLYB120V,598 功能描述:LED 照明開(kāi)發(fā)工具 SSL Mains Dimmable LED Driver Demo RoHS:否 制造商:Fairchild Semiconductor 產(chǎn)品:Evaluation Kits 用于:FL7732 核心: 電源電壓:120V 系列: 封裝:
SSL2102T/DB/FLYB120V598 制造商:NXP Semiconductors 功能描述:IC LED DRVR SOP-20
SSL2102T/DB/FLYB230V,598 功能描述:LED 照明開(kāi)發(fā)工具 SSL Mains Dimmable LED Driver Demo RoHS:否 制造商:Fairchild Semiconductor 產(chǎn)品:Evaluation Kits 用于:FL7732 核心: 電源電壓:120V 系列: 封裝:
SSL2102T/DB/FLYB230V598 制造商:NXP Semiconductors 功能描述:IC LED DRVR SOP-20
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