# Input series inductor waveform for a full-bridge isolated converter

**URL:** <https://forum.plexim.com/t/input-series-inductor-waveform-for-a-full-bridge-isolated-converter/1081>\
**Category:** PLECS\
**Tags:** full-bridge-converter, inducor-current\
**Created:** [December 4, 2021, 2:06pm UTC](https://forum.plexim.com/t/input-series-inductor-waveform-for-a-full-bridge-isolated-converter/1081 "2021-12-04T14:06:41Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![Haochen\_Tao](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@Haochen\_Tao](https://forum.plexim.com/u/Haochen_Tao)\
**Post date:** [December 4, 2021, 2:06pm UTC](https://forum.plexim.com/t/input-series-inductor-waveform-for-a-full-bridge-isolated-converter/1081/1 "2021-12-04T14:06:41Z")

</div>

Hello!

I encountered the strange inductor current waveform (Lin in the picture attached) when calculating the input capacitor to ensure a certain input voltage ripple and would like to know what caused the waveform to be like this. I think it is probably related to the input capacitance value but I am sure I used the correct method of calculating it. If implemented correcly this should be a smooth sine waveform without different values of peaks.

Thank you.

 ![circuit.png](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/570dd1431ff83b2cc9daa780f59cbb9ff343a1d3.png)

 ![current.png](https://europe1.discourse-cdn.com/flex006/uploads/plecs/original/1X/784efcde24b017f317d49893d7f987c46335e5d4.png)

---

<div class="post-metadata">

**Author:** ![Bryan\_Lieblick](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/bryan_lieblick/32/10_2.png) [@Bryan\_Lieblick](https://forum.plexim.com/u/Bryan_Lieblick)\
**Post date:** [December 6, 2021, 3:05pm UTC](https://forum.plexim.com/t/input-series-inductor-waveform-for-a-full-bridge-isolated-converter/1081/2 "2021-12-06T15:05:10Z")

</div>

Hi Haochen, It would be helpful if you could post your model in addition to the screenshots so we can see more about the modulation scheme and circuit values. Regards,Bryan

---

<div class="post-metadata">

**Author:** ![Haochen\_Tao](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@Haochen\_Tao](https://forum.plexim.com/u/Haochen_Tao)\
**Post date:** [December 6, 2021, 3:50pm UTC](https://forum.plexim.com/t/input-series-inductor-waveform-for-a-full-bridge-isolated-converter/1081/3 "2021-12-06T15:50:54Z")

</div>

Thank you for your reply!

I am currently an undergraduate student and actually I am designing this converter when the problem occured, so I guess for the model, all I can provide is the document below summarizing all my parameters. If you need more information please let me know.

Haochen Tao

[circuit values.docx](https://forum.plexim.com/uploads/short-url/c06nsQyzMpqgzqLTrUUrM8sSHdc.docx) (13.7 KB)

---

<div class="post-metadata">

**Author:** ![Bryan\_Lieblick](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/bryan_lieblick/32/10_2.png) [@Bryan\_Lieblick](https://forum.plexim.com/u/Bryan_Lieblick)\
**Post date:** [December 8, 2021, 10:30am UTC](https://forum.plexim.com/t/input-series-inductor-waveform-for-a-full-bridge-isolated-converter/1081/4 "2021-12-08T10:30:44Z")

</div>

Haochen,

I went through the exercise of creating a phase-shifted full bridge converter with the parameters outlined in the document. I observed a clean sinusoidal waveform on the input current. Please see the attached model. Note the component parameters are defined in the Initialization tab of the Simulation + Simulation Parameters… drop-down menu.

In the future if you could post the PLECS model file (\*.plecs) you are working with it would be helpful. There likely is a small error in a circuit parameter or in the implementation that would be very difficult to detect without the exact simulation model.

Regards,

Bryan

[PSFB.plecs](https://forum.plexim.com/uploads/short-url/qNCfnI200si0i9Q8wFHiPxhWKVt.plecs) (24.9 KB)

---

<div class="post-metadata">

**Author:** ![Haochen\_Tao](https://avatars.discourse-cdn.com/v4/letter/h/ecc23a/32.png) [@Haochen\_Tao](https://forum.plexim.com/u/Haochen_Tao)\
**Post date:** [December 8, 2021, 6:08pm UTC](https://forum.plexim.com/t/input-series-inductor-waveform-for-a-full-bridge-isolated-converter/1081/5 "2021-12-08T18:08:40Z")

</div>

Thank you for your advice! It is indeed a good way to define and show the parameters. I will go and check what went wrong compared with your model.

Regards

Haochen Tao