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200W 85 to 250V Power supply design

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Junior Member level 2
Nov 1, 2001
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Hi, i need to know the best configuration to do a 200W with 85 to 250V input and 24V output power supply

I have try a push pull but with a TL494 control (cheap IC), need very high voltage Power mosfets but is a "simple" design (2 exciter signals are ground refered and no need isolated transformers)

With this configuration I need high capacity (2 or 3 nF) in clamping circuit to avoid high voltages

Is this a usual capacitor value ??? (i think should be 1nF or so...)

Bridge configuration (like PC power supply) is better but i need to isolate one transistor (with transformer, optocoupler... ).

Flyback maybe a good option but.... Is possible to handle this power ?

Where can I obtain commercial exciter transformers or supply transformers with multiple outputs to exciter circuits ?

I have try with a old PC power supply and all componets are ok but i can't
find this easily at the market

Power Fets are better than Transistors ?

Someone can help me... ????

What kind of IC control ?, Power transformer and all this...


Hi ,

I have no experience in designing powersupplys but i repair often PC-Monitors and there ar alot of CRT Monitors on the Market with real autoswitching ( 105 -240 Volt ) Powersupplys , most of them have an rating about 100 to 230 Watt .
The most PC-Powersupplys that i have seen are not autoswitching . they are fixt in input voltage .

My tip for you is try to get some Monitor shematics form some newer Models.
They use often UC 28xx , 38xx PWM IC's ore some Mitsubishi Chips

hope this helps in anny way .


200W 85 to 250V Power supply design

Thanks HARDCORE for your suggestion this is a good idea !!!

Are you shure of CRT Monitors with autoswitching and 100 to 230 Watt ??

I always thought that this kind of monitors never consume more than 50 or 60W

You know where can i find some scheme ???

Thanks again.... :)


yes on the bigger monitors 21" or so . Sony got 200 Watt PS but i dont have sony schematics . for other Manufactors i have to check on Monday at work .

I know for 100% that there is an DELL PC-PS for an P4 with over 300 Watt and autoswitching !! I workt on that one , an american Customer told me to change the PS from 110 to 220 but wen i have a look on it it was autoswitching !! nothing to change !!


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