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| 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. |
| 文件頁數(shù)： | 19/29頁 |
| 文件大小： | 797K |
| 代理商： | SSL2102 |
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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
19 of 29
NXP Semiconductors
AN10876
Buck converter for SSL applications
5. Power calculations
The efficiency of a buck converter is one of the critical specifications for the design. One of
the things to consider, is that efficiency is always relative. Some of the losses of a buck
converter, such as the IC V
CC
generation, are fixed and depend on the IC. Because of
fixed losses, efficiency tends to deteriorate with lower output power. The variable losses
consist of a number of factors, and these are discussed in next sub-chapters. The
formulas in these chapters will give the designer insight into the parameters that
determine the losses for each component.
5.1 Resistive switch dissipation
In addition to capacitive losses (see
Equation 7
), there are also resistive losses in the
switch. The main parameters that determine these losses are the peak current and the
resistance of the switch, which is expressed as R
DSon
for MOSFET switches. There is a
momentary peak dissipation and an average dissipation.
(30)
For the duration of period t1, the total dissipation will be as shown in
Equation 31
(31)
For the total time period, the average resistive switch dissipation will be as shown in
Equation 32
:
(32)
Example: If f = 89.6 kHz, R
DSon
= 2.2
, I
peak
= 1.48 A and t1 = 5.28
s, then P = 0.76 W.
5.2 Capacitive switch dissipation
The capacitive switch losses have already been discussed in
Section 4.3
Equation 7
. It is
important to note that these losses are independent of the peak current and subsequently
the LED current. By using valley detection and an output voltage that is half the input
voltage, these capacitive switching losses can be avoided.
Without this option, the balance between switch size causing lower R
DSon
losses, and
capacitive switch losses will shift. A larger switch will have lower R
DSon
, but higher drain
capacitance. In such a situation, the optimum has to be selected:
For the following examples, I
peak
= 1.48 A, t1 = 5.28
s, V
sw1
= 100 V and f = 89.6 kHz.
1. If I
d
= 1.5 A, R
DSon
= 5.5
, C = 300 pF, P
RDSon
= 1.9 W and P
csw
= 0.13 W, then
P
tot
= 2.03 W
2. If I
d
= 3.5 A, R
DSon
= 2.2
, C = 550 pF, P
RDSon
= 0.76 W and P
csw
= 0.24 W, then
P
tot
= 1 W
3. If I
d
= 13 A, R
DSon
= 0.42
, C = 3.1 nF, P
RDSon
= 0.14 W and P
csw
= 1.39 W, then
P
tot
= 1.53 W
Remark:
Of the three previous examples, example 2 provides the best performance.
P
peak
I
peak
2
R
DSon
=
P
1
3
--
I
peak
2
R
DSon
=
P
1
3
--
t
1
f
I
peak
2
R
DSon
=
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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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