NTC Thermistor of Thinking

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????? Ripple / Noise ????
Outline
?. RIPPLE/NOISE ???
?. RIPPLE/NOISE ??
?. RIPPLE NOISE ???????.
?. RIPPLE NOISE ??????
?. RIPPLE NOISE ????
Prepared By AD Yuan May. 16th 2003
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?. RIPPLE/NOISE ???
1. Ripple ???,???????????(????) ??
2. Noise ?????????(??).
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?. RIPPLE/NOISE ??
1. Switching ripple/noise
?Forward converter????,????
(1) C??Switching ripple , ????? A???(or
Mosfet) ????( fs ).
gtgt????,Switching ripple ?????
5mv20mv??,????? AET?
20MHz ??????Switching ripple.
( 2 ) D ??Switching noise , ???????,?????????15MHz
18MHz
????.
gtgtSpec?????Ripple/noise ?,????
??? 0.1uF Cap. ?????Switching
Noise .
gtgt????, ??ATE?????????????,?????Ripple/noise ??
???.
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2 . Line Ripple
Line Ripple ?????????Ripple .????
gtgt??Line Ripple???
????.
? Boost Converter ????
gtgt????Full load ? , Boost Converter
????????Bulk????,????Line Ripple ?Bulk???, ?Line
Ripple ?????DC???,
?ATE????????.
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3 . Oscillation Ripple
?? Line Frequency ?Switching frequency
??,???Oscillation .??
gtgt????,Oscillation ???????? ,???????????
Vp-p???Limit ?.
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?. RIPPLE NOISE ???????.
1.????Switching ripple/noise ???????? ?? ,???
????????? .
2. Line Ripple ??????????,???????? ?2? .
3. Oscillation Ripple ?????????? , ??????.
4. Fan??????,?????????
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?. RIPPLE NOISE ??????
gtgt ??ATE Ripple/Noise??,????????Ripple/Noise
????
?????????????.
?????? , ?CHECK
1. ATE ???????????????.
2 . ??????????????????.
????????? , ????????? ?
1.
??Switching Ripple ?? , ?CHECK
No
No
A.????ESR?????? ?
B.???????????
C.?????????????
Yes
Yes
Yes
? ESR???????
?????????
?????
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2.
??Switching Noise, ?CHECK
?????????Snubber circuit ???? ?
?Q ?????? ? Check Vgs ? Vds ?? .
Yes
Yes
?Q?G??D????.
????????Snubber circuit .
3.
??Oscillation ?? Ripple , ?Check
Yes
Yes
????????? ??ESR ????? .
?????? (??????)
4 .??? Fan ??, ??? Fan ,Check Ripple/noise ?????
Yes --- ??FAN ???????????.
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5 .
??Line Ripple ??, ?Check
12V Output Spec200mv max
(1) ???????????? , ?Check PWM IC Isense ??? .
(2) ???EMI ???? ,??Y Cap.?? ???Q???.
(3) ??????Bulk Cap. ?? ,????? ?
(4) ????????? , ?????? .
( 5)????????????? ?
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?. RIPPLE NOISE ????
PS-6251-9C 5Voutput RippleNoise Defect Analysis
1.????
?ATE ?????5V ????? 50mv65mv(spec50mV).
Input 180Vac264Vac/4763Hz
????
Load 5V/25A,3.3V/3A,12V/8A,-12V/0.4A,5VS/3A.
2. ????
(1).?????????????????(53mv ).???.
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(2).???????,?????,??????AC?????2?(94HZ),???
AC???????NOISE ??---53mV.
(3).??????
1)?1PCS????PASS???,??Vpp??30mV
2)??????EMI ?????Transformer????,????????
??NGGood sample????????.
3).??YCAP C104,C105????????????,?????.?????
????,?53mV??? 24mV,????? .
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4).??OK????C104,C105????.
5).?C104,C105 ?????,?Ripple/noise?27.6mv???.??? .
3.???? .
(1).???? ?????????ATE????5V Vpp ?45mV(max) .
(2).Long term ?C104C105 ?????.
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????????
???????????!!!
Thinking
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