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Old 31st May 2007, 09:50 PM   #1
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Default High And Low Side Phototransistor Opto Mosfet Driver

Why in every PC SMPS there are classic FERRITE drivers instead opto drivers for high side mosfet?

for example 4N25 can drive bipolar transistor that drives high side mosfet

that circuit part has separated power supply from separated secundary , separated from 12SG power supply

OPTOS are FAST, no need fore ferrite core calculation, can operate the same at all ALL frequencies.. etc etc
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Old 31st May 2007, 10:39 PM   #2
Eva is offline Eva  Spain
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Standard optocouplers like 4N25 are very slow and suffer from unpredictable rise and fall times ranging from 1uS to 10uS. Furthermore, they are vulnerable to false triggering due to common-mode transients. Fast logic optocouplers like 6N137 still exhibit the common-mode vulnerability. Transformers are much more suitable for gate or base drive.

Also, most PC power supplies use bipolar transistors and "proportional drive" which is only easy to implement with transformers.
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Old 1st June 2007, 12:51 PM   #3
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Quote:
Originally posted by Eva
Standard optocouplers like 4N25 are very slow and suffer from unpredictable rise and fall times ranging from 1uS to 10uS. Furthermore, they are vulnerable to false triggering due to common-mode transients. Fast logic optocouplers like 6N137 still exhibit the common-mode vulnerability. Transformers are much more suitable for gate or base drive.

Also, most PC power supplies use bipolar transistors and "proportional drive" which is only easy to implement with transformers.

Do I have to rewound PC power supply mosfet driving ferrite core?: I each PC SMPS there is mosfet not bipolar?!

Quote:
common-mode vulnerability
What do you refer to ?
What are the main reasons why driving core is better than FAST 6N137
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