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    suitable topology for a 15V 0.5A SMPS from 100 to 230V AC manis

    Hello guys,

    I need to design an SMPS for my project. The output is 15V 0.5A with input being 100 to 230V AC. What topology do you recommend will be suitable?

    The project is based on Altera's EPM3032 MAX CPLD and I am thinking of a power tree of 15V > 5V > 3.3V using Texas Instruments' LM1117 LDOs to obtain 5V from the 15V, and 3.3V from the 5V.
    Do you think it is a good idea?

    Also, is it okay to place the SMPS (and LDO's) and the EPM3032 circuits on the same PCB?

    Please guide me on the way to do it right.

    Thanks in advance.

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    Re: suitable topology for a 15V 0.5A SMPS from 100 to 230V AC manis

    For that power level and input voltage range, a flyback. I would check Power Integration's website:
    https://ac-dc.power.com/

    Now to reduce from 15vdc to 5vdc, you don't require a LDO....a plain, inexpensive and ubiquitous 7805 will do.
    But a far better way would be, as shown on Power Integration's page, a dual output flyback, 15 and 5 vdc.

    Now...to go from 5vdc to 3.3vdc, you require a LDO. Use the fixed output version of the LM1117, but there are many others available too.
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    Re: suitable topology for a 15V 0.5A SMPS from 100 to 230V AC manis

    yes a offline flyback is for you.
    Any current mode flyback would be good.
    How much power is drawn from the
    15v, 5v and 3v3 rails individually?

    You could even use the new powerint.com chip that has the feedbakc internally, its on/off control but youre only after 7.5w.

    It coudl be on the ame pcb yes, but what is power as asked above?...as that will determine the final answer to you


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    Re: suitable topology for a 15V 0.5A SMPS from 100 to 230V AC manis

    Thanks schmitt trigger and treez for the responses.

    For that power level and input voltage range, a flyback. I would check Power Integration's website:
    https://ac-dc.power.com/
    I looked up the website like you guided me but I couldn't find a flyback of about the same power (7.5W) output but I found one with 17W output with 18V, 0.67A and 5V, 1A output.

    The 18V is still suitable where I needed to use the 15V. However, I don't know whether it is okay to go for such a substantially higher output-power flyback.
    I have not use a flyback before and I have not read from anywhere what effect that might cause.

    Is it okay to go for the 17W output? What's your advice?

    ---------------------------------------------------------
    Quote Originally Posted by treez View Post
    yes a offline flyback is for you.
    Any current mode flyback would be good.
    How much power is drawn from the
    15v, 5v and 3v3 rails individually?

    You could even use the new powerint.com chip that has the feedbakc internally, its on/off control but youre only after 7.5w.

    It coudl be on the ame pcb yes, but what is power as asked above?...as that will determine the final answer to you

    Hello treez,

    I cannot determine the actual value that the system is going to draw from each power rail. I just estimated the power, having put certain factor into consideration.

    Nonetheless, I estimated that 2.5W (max) will be drawn from the 15V rail; 1.7W (max) will be drawn from the 5V rail; and the 3V3 rail is just to power the Altera's EPM3032 CPLD core (Vccint) and also the output buffers (Vccio). If there is a way of figuring out the power a system is expected to draw, please show me.

    Also, please, can you enlighten me on the effect of trying to draw lesser current from a current-mode flyback than that which it was designed for if there is any effect?



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    Re: suitable topology for a 15V 0.5A SMPS from 100 to 230V AC manis

    power integration have a software program, you just use that to type in your spec and it designs to exactly what you want.

    - - - Updated - - -

    i dont know what the regulation is on the 5v and the 3v3, but you might be best off just doing a 15v output flyback, and derive the 3v3 and 5v from downstream regulators......a cheap buck module for each...linea.com do them, so do ti.com etc etc.

    - - - Updated - - -

    here is a offline flyback (basic idea) for you in LTspice simulator which is free download.
    Just convert file to .asc and open it and hit running man icon.
    it gives 15v 0.6a output...from that you can derive the rest.
    It is in dcm over the whole mains range, and this gives you nice ease with stability.
    as you know , you need to add in the opto isolation etc etc



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    Re: suitable topology for a 15V 0.5A SMPS from 100 to 230V AC manis

    Thanks schmitt trigger and treez for the responses. They were very helpful and got me moving forward.

    How much power is drawn from the
    15v, 5v and 3v3 rails individually?
    I cannot determine the actual value that the system is going to draw from each power rail. I just estimated the power, having put certain factor into consideration.
    I realized I could measure the power consumption using a bench PSU.



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    Re: suitable topology for a 15V 0.5A SMPS from 100 to 230V AC manis

    Many modules exist that do this for you too:

    http://www.digikey.com/product-detai...266-ND/4488645



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