參數(shù)資料
型號： 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.
文件頁數(shù)： 26/29頁
文件大小： 797K
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
26 of 29
NXP Semiconductors
AN10876
Buck converter for SSL applications
6. Current tolerance and stability
6.1 Current tolerance
In essence, there are only two main components that determine current tolerance. One is
the spread on detection voltage and the second is the tolerance sense resistor. This can
be derived from
Equation 46
:
(46)
Example: If V
ocp(min
) = 0.48 V, V
ocp(avg)
= 0.50 V
ocp(max)
= 0.52 V,
V
ocp
=
4 % and
R
6
=
1 %, then
I
led
=
5 %.
There is the possibility that the variation of C
p
and L
p
with valley detection will have some
influence, but in practice, the time influenced is much smaller then the total cycle time.
Example: If
L
p
= 10 % and
3 / t
total
= 0.052 then
I
led
= 0.5
L
p
0.05 = 0.25 %.
6.2 Current stability
For the buck converter using peak current control, stability is seldom an issue. This is
because the current is controlled per cycle and it is intrinsically stable. If some other
means is used to stabilize the current, such as current mirror detection, accuracy might
increase but the loop response must be calculated. The main component that determines
response at peak current control, is the output capacitor C5. It has to be charged and
discharged. At switch-on, the discharged capacitor will have to reach working voltage
before any current flows through the LED's and light is produced. This time is equal to the
charge time of
Equation 47
.
(47)
Example: With
V = 100 V, I
CC
= 700 mA and C5 = 3.3
F, then
t will be at least 471
s.
At turn-off, the diode characteristic of the LED will be effective. Instead of a sudden drop,
there will be an exponential drop of current, starting with the nominal current. The LED
current will slowly fade until it is no longer visible. In practice, this can take several
seconds. Since the LED's are placed in a self-rectification loop with the freewheel diode,
any capacitive coupling on the drain side, or inductive coupling over the loop with an AC
source will induce a current through the LEDs. Even a current as small as 100
A, could
be visible. This can happen if large, ungrounded objects such as heat-sinks connected to
phase, are in close proximity to the LEDs,
I
led
I
peak
V
ocp
R
6
+
=
=
t
--------------------
I
CC
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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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