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enter image description here

Hi, I have been constructing (transformer based) homemade inverters mostly using CD4047 as my drive circuit. Then one day while I was doing my research online, I came across an H-bridge system — one that I had never thought of. I was impressed with the fact that the system allows the use of a transformer without centre tap.

For a couple of days I have been trying out the circuit above which I downloaded from the web, but my problem is that the circuit seems to have been designed to be used with SG3525, and in my experience I have never constructed a drive using SG3525.

OK, I tried using CD4047 with the H-bridge system, and for like 1 minute it seemed to be working. But all over sudden, two MOSFETs blew off, one from the high side and one from the lower side.

So my question is, what should be done to the circuit to avoid MOSFETs blowing? Initially I wanted to design a 24V 6000W inverter charger; the MOSFETs I used were 4× IRF064.

Also, if you can try to advise me what to do if I wanted to add more MOSFETs in parallel and charge the batteries using the same MOSFETs and transformer, I will really appreciate it.

Below is my drive circuit using cd4047.

enter image description here

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  • \$\begingroup\$ Great sir,but is it possible for the h bridge system to work with cd4047 from your opinion? \$\endgroup\$
    – Shikhuyu
    Oct 4, 2019 at 15:02

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I am no expert on this type of inverter, but this answer comes from reading other articles and various YouTube videos. You need a dead period when all 4 mosfets are turned off briefly. Otherwise 2 transistors are partly on during the transition and effectively shorting the power supply. Have you set an adequate value for this with a resistor from Ct (pin 5) and the Discharge?

It is not clear from what I can find if there are not 2 different versions of the SG3525. Some diagrams seem to show that it has 4 outputs for driving the H-bridge directly, or maybe they are synching two separate ones together in order to get the 4 phase drive without overlaps. I'm not sure. See the diagram in this note

There is an article on the design here

and I presume you have the data sheets either here or here

I hope this helps somewhat.

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    \$\begingroup\$ This. The phenomena is called shoot-through. Do not try to minimize control inputs to the H-bridge by ganging MOSFETs gates together (unless you must) if you do not already know H-bridges very well which most people who are ganging them together do not. It is not simpler. It only looks simpler. \$\endgroup\$
    – DKNguyen
    Oct 3, 2019 at 14:48
  • \$\begingroup\$ Great point there sir,if can ask can the ganging of mosfet gates the reason why the mosfet blow? And if so does it mean I should provide each gate with independent control inputs? Iam not perfect with this please any diagram will be of help. \$\endgroup\$
    – Shikhuyu
    Oct 4, 2019 at 15:07

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