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SMPS Transformer Calculator

Flyback Transformer Design and Calculator Swagatam                  

SMPS Flyback Transformer Power Supply Design and Calculator

Each time the switching transistor is turned ON in a fly-back converter, the primary side winding of the transformer is energized, with no electrical energy is switched to the secondary side windings. The minute the transistor is switched off the electromagnetic field falls causing the electrical energy switched to the secondary windings. This sets itself apart from a forward converter topology, wherein electrical energy is switched across the secondary side windings each time the switching transistor is triggered. It is possible to explain the dissimilarity between the two main counterparts, according to the alignment of the dots on the secondary judged against the primary. For the fly-back converter, the dot's assignments are counteracted, and for the forward converter the dots are in line.

The calculator below computes the quantity of winding, the inductance value, in addition to the wire SWG or AWG for the assorted windings of a discontinuous mode SMPS fly-back converter.

Power Supply Specification:
Frequency, F: (KHz) T: (uS)
Diode Voltage Drop, Vd: (V)
Transistor Voltage Drop, Vtran: (V)
Efficiency: (%)
Max Transistor Voltage, VDSMAX: (V)
AL=L/N2: (uH/Turns^2)
Voltage Primary, Vin: (V)
Voltage Out 1, Vo1: (V) (Note that this must be positive, and feed back is derived from this winding)
Current Out 1, Io1 (A) P1: (W)
Optional Secondary Windings:
Voltage Out 2, Vo2: (V) 
Current Out 2, Io2: (A) P2: (W)
Voltage Out 3, Vo3: (V)
Current Out 3, Io3: (A) P3: (W)
Voltage Out 4, Vo4: (V)
Current Out 4, Io4: (A) P4: (W)
Transformer Result:
 Power In, Pin: (W)
Turns Ratio Primary to Secondary Winding 1, Nps1:
Charge Period, Tch: (uS)
Discharge Period, Tdis: (uS)
Dead Time Period, Tdt: (uS)
Primary Inductance, L: (uH)
Turns Primary, Np: (Turns)
Turns Secondary 1, Ns1: (Turns)
Turns Secondary 2, Ns2: (Turns)
Turns Secondary 3, Ns3: (Turns)
Turns Secondary 4, Ns4: (Turns)
Peak Primary Current, Ip: (A)
Primary RMS Current , Ipri(rms): (A)
Primary Wire Diameter, Dp: (mils)
Primary Wire Gauge, AWGp: AWG


Need Help? Please leave a comment, I'll get back soon with a reply!


  1. Please sir swagam help me with the sg3525 library for prosteus or nimultism please sir I need your help with it my email address is

    1. Hi Aminu, I don't use artificial simulators for designing circuits...I use my mind simulation so sorry I won't be able to suggest much.

    2. hello sir, i need ac to dc 12v smps circuit with transformer

    3. 12v, 1AMP SMPS circuit by using transistor, WITH FEED CONTROL

  2. Sir,
    In this 50℅ terminology I don't know .. can you give me any link from where I'll get terminology clear...

    1. Sinu, sorry I did not get your question...??

    2. Sir, can you give me details of how flyback SMPS working .. above article you mentioned like charge period , discharge period and dead time period etc what are this terminology how to find all this.. can you give me email id as I have to send SMPS circuit which is not switching on..

    3. Sinu, you can get a detailed explanation in the below given post

      read the "Structure and principle" section

    4. Thanks sir.... Can you give me your email id .. I am having dead set.. problem is with SMPS ONLY.. please guide me .I will send the schematic diagram

    5. Sinu, sorry, an SMPS cannot be repaired just by referring to its schematic, that's not possible, you will have to take the help of an expert available in your area, or may be a TV repairing mechanic might be also able to solve it for you


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