# Switch mode power supply +-33V

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#### Analyzer

##### Full Member level 6
top250y transformer schematics

I need to build a switch mode power supply.My circuit requires +-33V 3A power.Can somebody advice me a schematic for me? I dont want to use big, heavy transformators.I'll place it in a small box (of course if it is possible).Thank you.

Analyzer

#### Cluricaun

smps top249 schematics

Hi

I do not have any schematics but have you tried the software switchers made simple by National. Check their homepage, you can also simulate direcrtly at their HP.

I will check if I have any schematics in the drawer

Good luck

#### solvarg

##### Full Member level 2
Analyzer said:
I need to build a switch mode power supply.My circuit requires +-33V 3A power.Can somebody advice me a schematic for me? I dont want to use big, heavy transformators.I'll place it in a small box (of course if it is possible).Thank you.

Analyzer
How mouch power is rquired?

#### gulson

##### ssssss
+33Vx3A and -33Vx3A so total 200W

HASHINA

### HASHINA

Points: 2

#### Analyzer

##### Full Member level 6
Yea admin is right! Average 200W

#### mrseven2

##### Junior Member level 1
Motorola used to have a good AN about SMPS's.... Can't find the link, tough.

#### shanren

hi,do you mearn this PDF?
i think maybe you are making a audio ampifier,the 3A current maybe a little small.
regards.

#### barrybear

##### Full Member level 4
I was wiundering if you would like to reasses your need for a swichmode power supply.

Sony made a amplifier about 12 years ago that was as you have requested swiched mode and quite lite in weight,yet boosting 60 watts per channel.

I bought one of these amps and it would not produce the rms quoted without distortion and lukly for me it went wrong just befor the quarentee ran out . the shop manager said that he wished he had not supplied any of these as they were all going wrong.

I think that switched mode power supplies are OK if they just site ther and provide ther constant rated power but when there asked to work hard and deliver high currents ( momenterily ) they have problems.

I would stick to a linear power supply you can fry eggs on them befor they give up and are far more reliable than switched mode. I hope I have not started an avalanch of replies about the prowes and cons of power supplies but thats my experiance.

Hope this helps

BarrybeaR

#### marie65

##### Super Member
A good and very simple SMPS can be built using the TOPSwitch IC from Power Integrations. I builded a laptop power supply 220V / 19V_3A, with TOP249 and it work great. Also the datasheet and application notes are excelent. The producer also have a free software pack for easy design of your supply

#### shanren

maybe it is easy to build a SMPS with TOPSWITCH,but a 200w SMPS only can select TOP249Y and TOP250Y,under 220V ac.it is not so good for a audio system.maybe a ring transformer with a lot of capacitor is a good choice.
best wishes.

#### ogurets

##### Newbie level 6
Hi,
i have built simple smps for amplifier 2 x tda7294 with international rectifier's ir2153 fluo lamp driver and 2 irf740 mosfets on heatsink from pc psu , simple overcurrent protection by means current transformer - small ferrite toroid, power transformer - ferrite core toroid 45x28x12mm, no pwm regulation. It sounds clear and loud enough for me. I think you can get from it, say, 300 w easily.
You can also build smps with pwm regulation IC for example tl494, sg3524(5) etc. If you need more amps - use more mosfets in parallel.
Look for application notes power IC manufacturers (https://www.irf.com/technical-info/anarchive.html - one of these)
Regards

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