LED TV 背光板

這塊demo board效果唔錯.  一塊driver board 推 8 channel LED, 每channel最多20個LED.


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Sorry, I am afraid you think in wrong way.

The actual variation contributor is the LED forward voltage (Vf) which can vary as much as +/- 15%.  If all the LED connected in parallel across the same voltage source, then the current flowing through each LED would be very much different, unless you match the resistor for each LED precisely .  So, I would say parallel topology is more difficult to match.

The LED brightness is primarily defined by the current flowing through it, and if all LED connected in serious, the brightness would be similar though the Vf would be different.

If you ask the FAE from the manufacturer, they will tell you the same thing.

The only benefit of all LED in series  I can think of, is the easier  current matching.

唔知點解你話pros既我覺係cons
同電流令luminosity variation表現哂出來
粒LED luminosity上下限一無遺
無處躲
YES_MAN 發表於 2010-8-7 15:17

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The only benefit of all LED in series  I can think of, is the easier  current matching.

唔知點解你話pros既我覺係cons
同電流令luminosity variation表現哂出來
粒LED luminosity上下限一無遺
無處躲

TOP

所有大廠都係Parallel (channels) + Series (up to 20 LED per channel), 總有原因的.

1. 若果太多LED in series,  step up ratio會好高, 導致efficient降低
2. 高電壓, 大電流既 PWM driving circuit會好貴(we need brightness control for your TV), size也大, 不適合consumer product like thin LED TV
3. 若果所有LED串埋一起,  若果有一粒壞左, 就比較難搵邊粒壞.  若果係做part replace 要成條燈條換, 成本也貴好多.
4. 所有LED串埋一起做唔到advance features, e.g.  Local Dimming (locality controlling), Motion blur compensaiton (row controlling)

The only benefit of all LED in series  I can think of, is the easier  current matching.

點解唔一次串哂160粒LED
聖誕燈飾都係咁用3V燈泡串起
串夠數就直接插濕電
慳水慳力

唔想flickering
咪PF ...
YES_MAN 發表於 2010-8-7 10:40

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其實咁多粒,大約有幾多w電

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估唔到你地最大興趣係focus on 電容...

長的電容分別係47uF 450V及100uF 100V.  為左放係LED TV, 一定要做 ...
hknightlife 發表於 2010-8-7 02:07

多謝師兄解答!

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點解唔一次串哂160粒LED
聖誕燈飾都係咁用3V燈泡串起
串夠數就直接插濕電
慳水慳力

唔想flickering
咪PFC controller升上400Vdc先串LED

TOP

估唔到你地最大興趣係focus on 電容...

長的電容分別係47uF 450V及100uF 100V.  為左放係LED TV, 一定要做 ...
hknightlife 發表於 2010-8-7 02:07


我想請問下它日個LED TV的LED其中一粒壞左, 係唔係要成個塊咁換, 定係換其中一粒就得?

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估唔到你地最大興趣係focus on 電容...

長的電容分別係47uF 450V及100uF 100V.  為左放係LED TV, 一定要做到好薄.  依塊demo board既電容用料唔好. 不過如果係大陸牌子量產, 都唔會用名牌子.

應該是用長度來換取電容的細身, 所以連變壓器都要係底板開個窿沉落下, 以減少厚度。 ...
peterma 發表於 2010-8-6 23:38

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對, 德儀. 不過唔夠Freescale勁.  人地已經有local dimming feature出production, Samsung LED TV就係用Freescale既solution.

oh... TI wooo~~~~
poonpoon 發表於 2010-8-7 00:39

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