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LMZ31503: Power supply with linear transformer and LMZ31503

Leonardo Maya
Prodigy 50 points
Part Number: LMZ31503

Hello everyone.

Im in proccess to develop a source using a linear transformer and LMZ31503. 

The blocks are:

-> AC uiversal input > Transformer > Diode bridge > Smooth > LMZ31503 > 5v output

Are there any problem with this design ?

It will be possible to do ?

What can I do to provide an universal input with the same output ?

Thankyou! 

  • 0
    TI__Guru**** 191445 points
    Well, one thing is the input voltage range of LMZ31503 is 4.5 to 14.5 V. You will have to ensure that the rectified and filtered output of you transformer is within that range under all line conditions.
  • 0 in reply to JohnTucker
    Prodigy 50 points
    Mm okay, and could LMZ31503 has a dinamic output after rectification? Like an input in the range of 5V and 14V, where any voltage input to the LMZ31503(5v to 14v) provides the same output ? It is possible to do that with LMZ31503?
  • 0 in reply to Leonardo Maya
    TI__Guru**** 191445 points

    LMz31503 will regulate to the same output voltage as the input is varied.  This specification is called "line regulation".  For LM31503 it is specified as 0.1%.  One other thing you need to know.  You will need some headroom above 5 V on your input for 5 V output.  The minimum input is not specified.  I would probably design for a minimum input voltage of 5.5 or 6 V.

  • 0 in reply to JohnTucker
    Prodigy 50 points
    Thankyou!
    Yes the minimal input in the design for the LMZ will be 7V to meet 5v output. There are any issue to make a power source in that way ?
  • 0 in reply to Leonardo Maya
    TI__Intellectual 1155 points
    Hi Leonardo,

    in principle your concept will work. Just make also sure that your input can deliver enough current for "worst case" condition, meaning 7Vin and 5Vout. Calculated Duty cycle therefore is 71%. Let's assume an efficiency of 75% from AC source all the way down to 5V output of your application. The LMZ31503 is capable to deliver 3A.
    Minimum input current capability: Iin > (3A*0.71)/0.75 = 2.85A

    Have success with your design and don't hesitate to contact us again in case there are still questions left.

    Best regards,
    Michael