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Old 03-01-2014, 05:33 PM   #1
Ashroyer05
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Default Psu Transformer operation?

I uploaded a picture of what seems to be a pretty "simple power supply." I removed the transformer just to experiment as the board is completely fried. Where the secondary windings of the transformer go I put in a red oval. The transistor which I think controls it is in a red circle. The anode of the transistor (http://html.alldatasheet.com/html-pd.../2/TL431C.html) is connected the secondaries. My biggest misunderstanding here with this and other power supplies is why are all the secondary pins common to ground? Is it only until the transistor turns on and "re-routes" the voltage? And could someone give me a run down of how this supply goes from standy-by to full operation? Thank you in Advance. I have been studying for hours.
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Old 03-01-2014, 07:44 PM   #2
SM-Piyes90
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Default Re: Psu Transformer operation?

Am currently analysing a similar PSU , and trying to fix it just for learning purpose .

That transistor is a shunt regulator and along with an opto-isolator it is part of the feedback circuit used to control the secondary output voltage/current stability .

The upper transformer i guess is the inverter transformer ( i guess this is belonging to a PC flat screen ? )

Good luck with it .
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Old 03-01-2014, 08:27 PM   #3
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Default Re: Psu Transformer operation?

What is the make and model of this power supply? I cannot read all the info on the board. This power supply has PFC Voltage booster with multiple outputs so the common ground of the secondary side are tied together to form common ground.
Hers is the example circuit closes to what you have, you can see how the 431 and how the grounds in the secondary side are used and connected in the circuit.
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File Type: pdf Power supply philips_37MF321D_TPE1.0U-LA.pdf (1.82 MB, 31 views)
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Old 03-02-2014, 06:42 AM   #4
Ashroyer05
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Default Re: Psu Transformer operation?

715T2190 is the board.
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Old 03-02-2014, 03:21 PM   #5
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Default Re: Psu Transformer operation?

Well, did you at least look at the schematic and see how the secondary side of the grounds are connected?
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