DC to DC converter using push pull topology

DC to DC converter using push pull topology: DC to dc converters have vast applications now a days in switch mode power supplies , AC motor drivers, DC motor drivers and inverters. The objective of this project is to convert 12 volt DC into 311 volt DC which is a peak of 220 AC voltage. push pull topology is used because of its high power handling capability than buck, boost and buck-boost converter. I have already explained pulse width modulation and use of SG3525 IC. Beacuse I have used SG3525 as a PWM controller IC in this DC to DC converter. Other components used in this project are ferrite core tranformer, rectification circuit and feed back circuit.

If you don’t know how to use voltage mode PWM controller IC SG3525.I recommend you to go through following article first before reading this article further: SG3525 Pulse width modulation controller IC

Push pull converter is like a buck converter but it has two drive winding isolation transformer.I will explain it later how to make high frequency transformer. It can be used as step up or step down purpose depending on the turns ratio of high frequency transformer. Push pull topology require smaller filter than other dc to dc converter typologies. Multiple outputs can be produced by winding high frequency transformer according to application.you just have to increase number of output winding with respect to proper relation of turns ration with primary turns of high frequency transformer.

High frequency transformer

High frequency transformer of push pull dc to dc converter can handle more power than forward converter. Because push pull converter operate in two quadrants of B-H curve. On the other hand forward converter operate only in one quadrant of B-H curve. If you don’t know about  B-H curve , I recommend you to study B-H curve from any power electronics book.

High frequency winded transformer are usually not available in market. Ferrite cores area available in market. you have to wind them according to your specification. For example in our project we want to convert 12 volt DC into 311 volt DC. We can calculate turn ration for ferrite core by using input and output voltage. There is a proper relationship exist to calculate turn ratio for ferrite core transformer. There ara many ferrite core shapes available according to their power handling capability. For example we are designing 200 watt dc to dc converter. ETD39 core will work fine in this range of power. if you want to study more about ferrite core selection according to its power handling capabiliy, I suggest you to study ” Practical switching power supply design by Marty Brown ” chapter number six.

We can easily calculate primary and secondary turn by using following formula:

                                         N (primary) = (Vin * 10^8) / ( 4 * f * Bmax * Ac )

  •  Vin is a input voltage that is voltage which we want to step up in our case
  • f is a switching frequency of dc to dc converter.In our project switching frequency is 49kHZ. I will discuss it in detail later.
  • Bmax is maximum flux density. It depends on the core you are using. You can check its value limit from data sheet of core you are using. Bmax value should be with in a limit. Very high value cause a core to saturate and too low value will not utilize core properly. After reading from various books and sites, maximum authors suggest to use it value between 1500-1600 gauss.
  • Ac is cross sectional area of core you are using in your project.you can get its value from core data sheet.In this project we are using ETD39 hence Ac value given in its data sheet is 1.25 cm^2.

Hence by using above formula and values one can easily calculate Primary turns. Secondary turns can be easily calculated by using turns ratio formula of transformer that is :

                                            turn ratio = primary voltage / secondary voltage

                                             turn ratio = primary turns  /   secondary turns

By using primary and secondary voltage we can calculate turn ratio. By using turn ratio and primary turn we can easily calculate secondary turns. But in push pull topology high frequency transformer, There are two primary winding so primary turns will remain same for both primary winding.For example we have calculated 3 primary turns. Then total primary turn will be 3 turns + 3 turns for each primary. Figure below shows push pull transformer:

High frequency push pull transformer
High frequency push pull transformer

Components list

List of components:
Integrated Circuits,"U1",UC3525,
Rectifier diode,"BR1",UF4007,
Ferrite core transformer

Circuit Diagram of Push pull DC to DC converter


sg3525 circuit diagram
sg3525 circuit diagram



push pull dc to dc converter complete circuit diagram
push pull dc to dc converter complete circuit diagram

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Diagram above shows the circuit diagram of DC to DC converter using push pull topology.I have used IRF3205 MOSFET. you can increase number of MOSFETS in parallel according to power of your DC-DC converter. I have already explained all other things related to this circuit.If you still have any issue feel free to comment on this post. If you need complete circuit diagram and simulation of this project comment on this post with your email address.

Best wishes for your project 🙂

46 thoughts on “DC to DC converter using push pull topology”

  1. Great Work Bilak,
    I am very interested in your design, I am looking to implement something similar. Can you please provide more details on the winding of the trasnformer in terms of AWG used and winding method. Can you also comment on the core imbalance inherent in the design of push-pull topology.

    Once again great work, and thanks for sharing. Something I believe in greatly.

    Regards Peter.

  2. Bilal………..can you tell me the gauge of wire which you used in your project in (chopper) and what’s voltage across the primary of chopper at that time and finally, how can i calculate the Bmax? reply

  3. Salam bilal,
    I just loved reading ur blog it was really helpfull .. i tried constructing the push pull topology u shown in schematic . everything was going fine till i struck when i placed tranformer in proteus .. its showing transient error .. can u plz help me debuging this? it will be kind of you. thanku keep posting such blog 🙂

  4. Salam bilal,
    I just loved reading ur blog it was really helpfull .. i tried constructing the push pull topology u shown in schematic . everything was going fine till i struck when i placed tranformer in proteus .. its showing transient error .. can u plz help me debuging this? it will be kind of you. thanku keep posting such blog 🙂 ..thanks in advance

  5. Hi Bilal,
    Great works going here. Thank You.
    Here is my doubt.
    People usually say no to have a common ground (I mean H bridge isolated from the push pull part)
    But here in this circuit it seems to me like it’s a common ground. I would like to know if there is any serious issues that you are facing?

  6. Nice to go through your blog and got good understanding of DC -DC converter & transformer winding details.

    Can you please send the circuit diagram and simulation of the project.

  7. Hi Bilal

    i have asked this question of you more than two weeks ago and have had no response. Please help me.

    I am needing to make a 1200 – 1500W sine wave inverter and have studied your articles in this regard in the finest detail. I wish to use an Arduino uno to achieve this using all your advice which is much appreciated.

    My problem that I have lies in the core selection for the DC-DC conversion for this power conversion. My dilemma lies in what is probably a lack of understanding of your circuit. I am aware of the voltage feedback you are using with the IC to alter the PWM in order to stabilise the output voltage under varying loads and input voltage variances. What concerns me is how you prevent ” Flux walking” or transformer core saturation, as a result of any probable dc bias. I have tried all sources for a solution that I can understand however they all seem a little out of my grasp with my limited experience, the most interesting reading being found here http://powerelectronics.com/power-electronics-systems/special-dcac-inverter-avoids-transformer-core-saturation

    Any light that you could shed on this problem will be most appreciated.

    Kind regards



  8. Hi bilal,
    I have seen your explanation about the sg3525 inverter. these modules are for sail now on ebay and i would like to know how I can put two of these modules in parallel. and connect them to a post sine wave board of 1Kw. I see that you can sync the chips using the Sync (pin3) input but I do not know what the exact criteria is. I hope it is possible to sync one chip to the other by available signals but am not sure. An other possibility is to connect the bridge rectifiers together and that is. Can you help me with this regards Oscar Goos (wogoos@gmx.com)

  9. hi bilal
    in my project we use dc to dc converter which convert 24 v to 360 v and 500 w what should i do if i use your circuit.

  10. good work malik.
    I have two questions on ferrite core transformers

    1. suppose I want to use a 500W ferrite core transformer, how do I know the part number? and is there a single 1000W ferrite core? if there is, how do I know it’s secification.

    2. how do I know the specifications (ie power rating, permeability, etc) of a ferrite core that nothing was written on?


  11. Hey Bilal can you send me the complete project of pure sine wave inverter as i am 3rd year student and having a lot of difficulties.
    Thank you

  12. Notice you are not using an inductor (choke) between the output of the full wave bridge rectifier and the output capacitor. Have you found this not necessary or even undesirable? Thanks!

  13. i have first time visited in your blog , and it was a nice blog for me, but i need different design.
    can you please tall me how to make adjustable duty cycle and frequency using SG3525. needed pulse voltage 3 to 10vdc

  14. Hi Bilal

    Thanx , it’s hard to decide what topology to follow with the components you got in hand. I got the DC to DC converter which I would like to use in the inverter I want to make. But I want to use the ir2110 H-Bridge drivers as well with an P16f877 to do the SPWM to drive the ir2110 drivers. Any insight on this ?
    thanx in advance,

  15. Transformer used in proteus is, centre tapped on secondary side , you have shown it using it in primary side. Proteus give many errors regarding this. please help.


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