1000w smps based on LUDO3232

Upik

Member
To change the frequency it seems I have to change the resistor larger than 20k. But I can not understand the value of DT resistor. Rightly i do not have ociloscope
 
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Silvio

Active member
Well the data sheet of the chip SG3524 will have all the information if you follow the graphs regarding the capacitor used for the wanted frequency and also the dead time resistor. These parameter will be close and only when you check with the scope you will know the true readings.
 

Upik

Member
I have found the problem, it turns out the frequency is less fitting with the trafo.saya replace the 20k to 33k. Do I need to change the gate resistor gate mr.silvio, ??
 

Silvio

Active member
I have found the problem, it turns out the frequency is less fitting with the trafo.saya replace the 20k to 33k. Do I need to change the gate resistor gate mr.silvio, ??

If you change frequency the snubber may have to be adjusted, The use of a snubber is there to filter out any spikes during switch off of the switching transistor. If you changed the frequency then it may be that a different value is needed to filter out any spikes. I do not know what frequency you are running your smps, Please remind me again and tell me if your smps is regulated or not.

The gate resistor if not using the same setup that is sg3525 and IR2110 driving IRFP460 then all remain the same however if using IGBT instead then it could be you need to change gate resistor.

I have a blog post here how to calculate the gate resistor and also how to calculate snubber value. You can follow the blog post and make your calculations. Be careful when selecting gate resistor and remember that the maximum current of the IR2110 (2A) is not exceeded, if you have more than one fet or IGBT then gate resistor value has to be changed

Ex if gate resistor need to be 10 ohms for one fet then if you use 2 fets then you use 20 ohms for each fet because when they are in parallel the driver will still see 10 ohms hence the maximum current will not be exceeded
 

Silvio

Active member
Hi mr.silvio, I have completed my project, but I have not tested it, there is a problem in my transformer, there is a ringing sound. Do I need to adjust snuber, or maybe protection card (OCP) I have not planted, ??https://drive.google.com/file/d/1opEscKsEdNXQebZP4UX9BRQylU53k8jJ/view?usp=drivesdk

The ringing is not a good sound also the voltage at the output is not stable. I do not know the core material and it could be that you do not have enough turns in primary. Are you using feedback? did you set the dead time correctly? Did you load the smps? Is the frequency correct? It is not easy to find answers without oscilloscope.
 

Silvio

Active member
I have checked the data sheets of both IRFP460 and also FGH60N60FD Regarding total gate charge and rise and fall times of the two transistors they are quite close and the gate resistor can be left at 10 ohms use also the reverse diode parallel with the gate resistor.

Please note that now due to frequency is lower than the previous smps there will be more time for switch off between pulses so smps should work with 10ohms gate resistor

Change the gate emitter resistor from 10K to 5.2K to help more not to have false switching. Regarding the dead time resistor leave it at 33ohms but you should have the 470K resistor also on the sg3525 between pin 1 and pin 9 this will make sure your dead time will not go below 1uS.

PS I saw the video and the output voltage was changing a lot. Was it while the transformer was ringing or you where loading smps?
Fit also over current protection before loading smps so that if something is not right you will save the IGBT and input rectifier.

Good luck

Regards Silvio
 

Upik

Member
.Yes mr.silvio ,, I myself do not understand why the output voltage changes from before when I turn on the first time with improper frequency, maybe the national power plant is going up, but I do not see it, because I do not measure it, I think I can not linger long time turn on my smp, i have not loaded it at all, i checked my pwm card again, and when i measure the return frequency from one pin ho / lo to ground it turns out they are working on 12.6khz, because before i measure both prob from ho to lo , not to ground in one of the prob. now the frequency is right with the trafo.ya roll i did not leave 470k Resistor on pin 1 to pin 9 sg3525. i have Soft start 47uf on pin 8 Sg3525.
 
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Silvio

Active member
@Upik

Put again the 470K resistor between pin 9 and pin 1 otherwise you will have a very short dead time with 33ohms resistor on discharge pin of sg3525. You do not have scope so make it safe.

For 20amps setting you could reduce between 2 or 3 turns from the current transformer and check again by loading the smps to maximum load and set the trimmer for the desired operation.

Soft start capacitor is good at 47uF that is the maximum you can put. The larger the capacitor the slower ths soft start.

To check frequency with meter you can put ONE probe on the transformer primary and see the frequency this should be 25Khz
 

Upik

Member
Well, I will try it, what about the load resistor on Primary Capacitor, ??? do i add it, ?? or can i ignore
 

Silvio

Active member
Yes you will add it you can go for 33K each if you want. These are there to bleed off the high voltage after switch off. It will surely shock you if you forget to discharge the input capacitor.

I posted a PDF file with some pictures of a commercial 3K smps for you to see.

View attachment 3k smps.pdf
 

Upik

Member
Hi mr.silvio ,, i already have igbt stock IRG4PSC71UD ,, what if i use that instead of fgh60n60,, seems i should remove the mur460 diode.
 

Silvio

Active member
Hi mr.silvio ,, i already have igbt stock IRG4PSC71UD ,, what if i use that instead of fgh60n60,, seems i should remove the mur460 diode.

Hi Upik, Looking at the data sheets it seems that the IGBTs are more or less the same in characteristics. What I did not find in FGH60N60 is the graph that shows the derating current versus frequency. In the data sheet of the IRG4PSC71UD the graph shows that at a switching frequency of 30Khz the collector current must not exceed 20 Amps. As it goes higher the lower the current capability.

You should also know that IGBTs do not like high switching frequencies and the higher it is the lower the current that they can handle.
A 3KW smps draws around 20amps but that will be only on peaks for a short time in an audio amplifier. IGBTs have a low forward voltage and dissipate less heat while switching. Mosfets on the other hand can handle faster switching frequencies.

Use the MUR460 diode as this will help the internal diode in the IGBT to dissipate less heat. Put it as close as possible to the IGBT on the pcb.

Lately I am helping a friend repairing professional amplifiers and from what I am seeing they have a lot of input capacitance and the rule of thumb that I told you about that you must have 1Uf per watt across 300v is all true. This seems to be more important than the output capacitance. One case for a 3K smps input capacitance has 3000uF across the 320v (10 capacitors of 1200uf X 200v) and 5000uf (5 X 1000uF X 100v) on each side of the double output of 85v (170v)

Cheers Silvio
 
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Upik

Member
Hi Upik, Looking at the data sheets it seems that the IGBTs are more or less the same in characteristics. What I did not find in FGH60N60 is the graph that shows the derating current versus frequency. In the data sheet of the IRG4PSC71UD the graph shows that at a switching frequency of 30Khz the collector current must not exceed 20 Amps. As it goes higher the lower the current capability.

You should also know that IGBTs do not like high switching frequencies and the higher it is the lower the current that they can handle.
A 3KW smps draws around 20amps but that will be only on peaks for a short time in an audio amplifier. IGBTs have a low forward voltage and dissipate less heat while switching. Mosfets on the other hand can handle faster switching frequencies.

Use the MUR460 diode as this will help the internal diode in the IGBT to dissipate less heat. Put it as close as possible to the IGBT on the pcb.

Lately I am helping a friend repairing professional amplifiers and from what I am seeing they have a lot of input capacitance and the rule of thumb that I told you about that you must have 1Uf per watt across 300v is all true. This seems to be more important than the output capacitance. One case for a 3K smps input capacitance has 3000uF across the 320v (10 capacitors of 1200uf X 200v) and 5000uf (5 X 1000uF X 100v) on each side of the double output of 85v (170v)

Cheers Silvio

Well, Thanks mr.silvio ,,, what about the gate resistor, ?? is it with the same value, ??Can I replace the 1n4148 diode with 1n5819, ???
 
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Silvio

Active member
Well, Thanks mr.silvio ,,, what about the gate resistor, ?? is it with the same value, ??Can I replace the 1n4148 diode with 1n5819, ???

The gate resistor is the same 10 ohms this is calculated according to the driver to limit current, IR2110 can handle 2 amps of drive power.
regarding the diode yes you can replace it with 1n5819.

Upload some pics when you can I want to see your project
 

Upik

Member
I want to Fix pcb, there are some paths that do not fit, then I just give jumper with copper wire, and also I can not install protection card, it is not enough space between pwm card. Below new pdf pcb, please check again mr .silvio
View attachment HB3000W V3.pdf
 
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