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1.5kw DC to DC Boost Converter Circuit

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on previous picture you can see the noise line running through the signals when voltage feedback is implemented
Click to expand...
May be. Control algorithm and gate signal generation wasn't yet described or addressed at all in this thread. How can we know if it's implemented appropriately?
 

The top signal is HO and Bottom is LO.
The input voltage to sg3525 and ir2113 ic are 12 volt.
I can't measure the vgs but clearly on the signals shown you can see the difference.
What do you mean by voltage offset?

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My circuit design is based on Tahmids circuits which he shows on his thread which I posted on the beginning of this thread..
Sg3525 driving 2x ir2113.
 

Hi,

For me it's difficult to find out what you mean.
* you still mix HO and V_gs of high side. These are not the same. .. as already explained in the application note and in the previous posts. If you mean HO, then please write HO.
* you write "input voltage" this can be logic signals or power supply. If you mean supply, then please write supply

I can't measure the vgs but clearly on the signals shown you can see the difference.
Click to expand...
We know the difference and we still explained it. The application notes do, too. So what else do you need? Exactly.

What do you mean by voltage offset?
Click to expand...
Where is the "zero volts line" for each channel in your scope picture?

Klaus
 

I got the circuit running very good up to 800 watt with great efficiency and no cross conduction after adjusting dead time on pin 5 and 7.

The problem I'm facing now is that my signal looks like it's switching on and off when I run light loads but when pulling bigger loads it works perfect. Can anyone maybe suggest where to look for the problem on the sg3525 on the video it looks like the signal is shutting down very quickly and it also sounds like it.https://youtu.be/ji8OqNnE-LM
 

It looks like the gate control is paused intentionally by the controller circuit. If so, it's a software rather than power electronics problem. Any voltage regulation implemented?

To ask the other way around, did you verify that the gate driver input signal is running continuously?
 

Yes, I'm using this circuit https://tahmidmc.blogspot.com/2013/01/using-sg3525-pwm-controller-explanation.html
Which are running the 2 ir2113 ic.
It regulates the volts fine when having larger loads than the signal is continuously.
Say I pull 600 watt than signal is continuous but if I pull 400 watt than signal does this, you can also see the soft start working when switch on. I've also tried adjusting values on the feedback but it's still the same.
 

Thanks, I didn't realize that it's a 3525 hardware pwm controller. I guess, instability occurs when the output current transits to discontinuous mode (DCM). Power stage gain is constant in CM but increasing inversely proportional to output current in DCM. There's no simple means to handle the gain variation with a voltage mode controller, except for reducing the controller gain a lot and possibly switching it depending on the load.

Do you understand how to analyze loop gain and how to dimension controller compensation?

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You can monitor CM to DCM transition by either measuring L1 current with a current probe, or more easily, watching the positive rectifier output terminal waveform.
 

Do you understand how to analyze loop gain and how to dimension controller compensation?

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You can monitor CM to DCM transition by either measuring L1 current with a current probe, or more easily, watching the positive rectifier output terminal waveform.[/QUOTE]

No I don't understand how to analyze loop gain

If you say positive rectifier terminal out, than I understand that this is the terminal also going to my feedback of the sg3525?
 

If you say positive rectifier terminal out, than I understand that this is the terminal also going to my feedback of the sg3525?
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No. I'm only talking about a way to analyze the operation mode. As said, there's no simple solution, except for reducing the controller gain.
 

FvM said:
No. I'm only talking about a way to analyze the operation mode. As said, there's no simple solution, except for reducing the controller gain.
Click to expand...

How would I go about reducing the gain, should I remove the 10nf cap from pin 9 to ground and apply it with a resistor to pin 2?
 
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Can anyone please shed some more light on this?
 

So I wanted to change my converter to a 24 volt from 12 volt after everything was working successfully.
The problem I have now is that when I load the 24 volt on to the circuit input , it raises the gate charge to high on HO and kills my mosfets. On 12volt it works fine as the the gate charge stays fixed.

How can I prevent this from happening on my 24 volt converter or can I use the ir2113 without the bootstrap circuit and drive HO directly from VB with a 15volt supply as regulator?
 

I have a 15,volt regulator on but it seems to raise the gate charge very high on HO past the diode drop voltage of VB. I don't know why it doesn't stay regulated, I thought that d1 was supposed to keep it regulated.

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Easy peasy said:
use a 15V reg to power the IR2113 ....
Click to expand...

I think I misunderstood you, I have a 15volt regulator feeding the Ir2113 , do you want me to add another one going to the
Bootstrap caps from high and low side mosfet?
 

Hi,

With 24V power voltage and a 15V regulator.
--> HO may go up to (24V + 15V =) 29V referenced to GND ... to get a V_gs at the upper Moseft of about 15V.
This is how a bootstrap circuit is meant to operate.

Klaus
 

KlausST said:
Hi,

With 24V power voltage and a 15V regulator.
--> HO may go up to (24V + 15V =) 29V referenced to GND ... to get a V_gs at the upper Moseft of about 15V.
This is how a bootstrap circuit is meant to operate.

Klaus
Click to expand...

Ok, but this is causing my mosfets to fail, So what do I do to prevent this?
Do I remove the bootstrap circuit and drive HO directly from 15volt regulator?

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Can someone please elaborate on this cause no one is giving me an actual solution to the problem?
 
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best to show your ckt ...

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at 24 volt you may be killing your fets with over current ...
 

Easy peasy said:
best to show your ckt ...

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at 24 volt you may be killing your fets with over current ...
Click to expand...

If you read the thread you will see that I'm using thamids H bridge circuit and that I'm using irfp7430 which overkill for 24 volt. These mosfets run easy with higher current on 12 volts.

I think I need to go bigger with my bootstrap capacitors so they don't get fully charged because they might be to small for 24 volt. I'm using 22uf so I might go to 68uf cause i think they get
Overcharged.
I hope there is someone that can confirm this?
 

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