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| SM8207 Datasheet, PDF (7/9 Pages) SamHop Microelectronics Corp. – SM8207是一顆降壓型定電流的LED驅動IC,可應用 | |||
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SM8207
(LED Short Protection)
SM8207çCSè
³æä¾å
©ååè½:輸åºé»æµæª¢æ¸¬åéé»
æµä¿è·. ç¶CSé»å£è¶
éè¨å®å¼1.0Væ,é極輸åºç«
å»è¢«éæ·,é²èæQ1éé,æ¤ç¾è±¡ææçºç´å°ä¸ä¸å
é±æçéå§. é種é±æéçä¿è·æ©å¶å¯ä»¥é¿å
å¤é¨
é¶ä»¶çæå£å¨æ¸¬è©¦æçç¢çéç¨ä¸.å¦æ輸åºå´LED
被ç¬éçè·¯æåæçºçè·¯å°å°,輸åºé»å£æéä½,å
æVINå¾ä¸å°è½éçè£å
ä¹é¨ä¹éä½,ä¸æ¦VINä½æ¼
8V,SM8207å°æåæ¢æä½,æ¥èICæéçè½éå°±å¿
é
ç±æ©å¼æ´æµå¨è¼¸åºé»å£ç¶ç±èµ·ååé»é»å¨ä¾æä¾,
å¦æ¤ä¸ä¾;æ´é«çååç¨åºå°±æå¦åæè¿°,éæ°æ
ä½.
(LED Open Protection)
æ£å¸¸æä½ä¸,å¦æLEDè² è¼è¢«éè·¯,é»æµè®å¾å¾å°,
æ§å¶å¨ææå°éé±æå 大試åå調æ´.å¨æ¤æ¢ä»¶è¼¸
åºé»å£æå¢å å¾å¿«ç´å°ZCDè
³ç檢測å°2.65Vçé»
å£ä¸¦ç¶æ1.6usæéæ·Q1.çºäºé²æ¢éåç°å¸¸çé«
å£çç¬IC,SM8207èç±å¤é¨ç¨½ç´äºæ¥µé«(Vzn=27V)
ä½éä½é»å£ä¿è·. SM8207æçºééç´å°VINéè³8V
並åç´14Vå¾æåéæ°åå.
å¨å¹³å¸¸æä½æ¢ä»¶ä¸,è¨è¨è
å¿
é 注æé¸æR11,R12ç
å¼,使å
¶é é¢ZCDçè·³è«å¼(2.65V)åè½è®é¶é»æµæª¢
測é»è·¯ç©©å®çå·¥ä½.èä¾èªªæå¦ä¸:
å·²ç¥çå·¥ä½æ¢ä»¶å¦ä¸:
VLED=32V, VZCD_UP=1.5V,VZCD_OVP=2.65V
å
¬å¼2 ---
VZCD_UP < VLED x
RZCD
< VZCD_OVP
(R11+R12)+RZCD
代å
¥å·²ç¥å¼ ---
12KΩ
1.5V < 32V x
< 2.65V
(R11+R12)+12KΩ
é¸æVZCD=2.0V, å¾å°R11+R12=180KΩ, åæ¨æº
çé»é»180KΩ.
IL
IPK
IPK=(Vac-VLED) / L * T_ON
IPK=VLED / L * T_OFF
T
T_ON
T_OFF
FET_ON
FET_OFF
1 Cycle
å4: é»æé»æµç波形
å
¬å¼3-é»æè¨ç®å
¬å¼:
L=
VLED
1
x
x Vac -VLED x Ke
2.7 * ILED
FSW
Vac
å
¶ä¸; VLEDæ¯LED串é£ç總é»å£
ILEDæ¯LEDé åé»æµ
FSWæ¯åé±æé »ç
Vacæ¯äº¤æµé»å£çææå¼(R.M.S)
Keå¼æ¯è£åç³»æ¸ç´0.9(ç¶VLED=32Væ)
90 â sin-1 (VLED /â2Vrms) 2
Ke = (
)
90
ç±æ¼LEDèé»ææ¯ä¸²è¯,æ以輸å
¥é»å£å¿
é è¦å¤§æ¼
VLEDæLEDæææé»æµçæµå.å æ¤Keå³æ¯åé±ææ
çå°éè§.
(L1)
æµç¶é»æçå¹³åé»æµå°±çæ¼LEDçé»æµ,èé»æç
é»æµæ¯ä¸åä¸è§æ³¢å½¢,å
¶æ³¢å½¢å4æ示. é常å¨å
¨é»
å£AC輸å
¥çæç¨,åé±æçå·¥ä½é »çä¸è½è¨è¨å¤ªé«,
以å
å çºè¼¸å
¥é«å£èå½±é¿äº¤ææ失çé大,使æç
éä½,ä¸è¬æ建è°è¨å¨60KHzå
§.
www.samhop.com.tw
7
Rev. 1.1 @ 2013/03
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