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badboy_6120
06-08-2018, 04:34 AM
Hey Guys

I'm working on a 800W Smps to drive my Amps in my car but I'd like to test it out fully before I use it in my car
So I'm looking for a power supply to simulate car voltage to test and use the audio system at home (13.5 to 14.7V @ about 80A)

Which solution do you guys recommend:

1- Wind a 50Hz transformer
2- Build a regulated SMPS

Silvio
06-08-2018, 05:34 AM
Use a car battery and a charger

badboy_6120
06-08-2018, 07:50 AM
Use a car battery and a charger

I have the car battery but about the charger, doesn't those only deliver about a couple of amps to charge the battery ?????
I talking about 30 to maybe 80A here the doen't need the battery to deliver much of the current

Maybe you mean different charger than what I have in mind.

I honestly tempted to buy a 90A car alternator and a 1ph ElectroMotor Rated at 4HP @ 3000RPM but the only problem I have is with the size of this things.

noonehere
06-08-2018, 08:10 AM
If its only short term then the small charger will be fine.. even a small lead acid battery will put out some serious amps short term

badboy_6120
06-08-2018, 08:52 AM
If its only short term then the small charger will be fine.. even a small lead acid battery will put out some serious amps short term

actually no as I said I may wanna use this at home so it should be something to dilever 60A for an hour or 2 without any problem
I can test the smps with the car battery that I have but without the altenator the voltage will drops and it will not be the case where I want this circuit to work(about 14V)
so i'm looking for some method to keep the voltage on the battery around 14v when I drawing that many current (basically like what an altenator in a car does)
I think a 50Hz transformer would be a good choice here but I don't know what output voltage and current my transformer should have? because after converting it to dc the level of voltage and current is different
does anyone know a good and valid reference to calculate the ratings of the transformer

Silvio
06-08-2018, 09:27 PM
I see if I understand well that you want a mains driven smps that can deliver 13v at 60 amps well that is a little less than 800w. If the load is going to continuous that is one thing but if the load is intermittent say 50% than that will be another.

You can build an smps with half bridge like the 1000w smps and use thick secondary so that it can deliver current. You also need high current output diodes which have to be fast switching. feedback perhaps as well. You can use copper sheet for your secondary winding. If it is going to be for audio purpose then a current density of 5 amps per mm˛ will be ok.

Taking some assumptions 60amps at 5amps per mm˛ = 60 / 5 = 12mm˛

ETD 49 bobbin is around 30mm long so a 0.2mm thick copper sheet will be 30X0.2 = 6mm˛ this is only half so you need to parallel 2 sheets together. One other option is to make a center tap winding and use 0.2 sheet for each winding then use a common anode diode on the output.

Regarding the size of an iron core transformer it should be the size of a microwave oven transformer more or less. The filtered secondary voltage will have to be larger so that it can be regulated to the desired output voltage. This will bring more complications to your setup and I think you should avoid it.

I hope that helps Silvio

kegs
06-11-2018, 10:04 PM
have you tried using a 2000va found in UPS

badboy_6120
06-12-2018, 06:35 PM
have you tried using a 2000va found in UPS

Actually as I haven't find the high speed & high current output diodes for the Smps in my area that my friend Silvio here suggested, I go for a powerful 2KW 50Hz transformer at it will be ready in a day or two
I also bought car battery and a 3 Farad cap to minimize its ripple and 4*100A diodes so can handle this much current
it cost about 300$ to gather this stuff but I think it will worth it

Silvio
06-12-2018, 07:08 PM
Hi bad boy, I think you made a good choice as that kind of setup is more robust and more forgiving. What I am aware of is the 3 farad capacitor. This can easily destroy you rectifier diodes during start up. The transformer itself will also give surge in the mains and may blow your fuse during switch on.

If you want an easy soft start to build you can find one in my blog posts. I made this for my isolation transformer which was around 1500w.

One other option is to connect the battery first before switching on the supply so that the battery will charge the capacitor instead.
Please also note that the battery itself will act as a capacitor and smoothing down the ripple.

I would include the soft start as this will help things to tame down a little bit at start up.

Regards Silvio

kegs
06-13-2018, 03:11 AM
Actually as I haven't find the high speed & high current output diodes for the Smps in my area that my friend Silvio here suggested, I go for a powerful 2KW 50Hz transformer at it will be ready in a day or two
I also bought car battery and a 3 Farad cap to minimize its ripple and 4*100A diodes so can handle this much current
it cost about 300$ to gather this stuff but I think it will worth it

For rectifier the best place is from a PC POWER supply as they are high speed and paralleling several is a good bargain

badboy_6120
06-13-2018, 02:17 PM
Hi bad boy, I think you made a good choice as that kind of setup is more robust and more forgiving. What I am aware of is the 3 farad capacitor. This can easily destroy you rectifier diodes during start up. The transformer itself will also give surge in the mains and may blow your fuse during switch on.

If you want an easy soft start to build you can find one in my blog posts. I made this for my isolation transformer which was around 1500w.

One other option is to connect the battery first before switching on the supply so that the battery will charge the capacitor instead.
Please also note that the battery itself will act as a capacitor and smoothing down the ripple.

I would include the soft start as this will help things to tame down a little bit at start up.

Regards Silvio

Thank you dear Silvio for your through explaination
The diodes I'm using are capable of withstanding 2000A surge current for an half cycle of 50Hz but always it's a good idea to have a protection board

Thanks again:w)

badboy_6120
06-13-2018, 02:22 PM
For rectifier the best place is from a PC POWER supply as they are high speed and paralleling several is a good bargain
that was the first place I look but those diodes can only withstand 30 to 40A current and I know that paralleling diodes is not a good idea unless they are exactly the same

badboy_6120
06-14-2018, 04:20 PM
I test my inverter with my car battery and here's the result :

Without load : 172V in output << 12.9V input
23W load : 152V in output << 12.9V input
65W load : 147V in output << 12.87V input
100W load : 145V in output << 12.75V input
230W load : 132V in output << 12.56V input
370W load : 118V in output << 12.38V input
450W load : 110V in output << 12.13V input


Here's my inverter's Schematic :
6705

inverter frequency : 30 KHZ
Transformer windings :
Primary : 2+2 turns of 300 strands of 0.25mm wires ))
Secondary : 12+12 turns (( 70 Strans of 0.22mm wires ))

Is there something wrong with the schematic??? why the voltage drops is so high ???
I even test it with higher input (15V) and at 600W the output voltage reach 136V
???

Silvio
06-14-2018, 08:42 PM
Quote

Is there something wrong with the schematic??? why the voltage drops is so high ???
I even test it with higher input (15V) and at 600W the output voltage reach 136V
???

Let us consider things a little bit
According to the windings we have 2 turns Pri 12 turns sec So the ration is 12 /2 =6 The ratio is 1:6 This means that for 12v input the output voltage is 6 times higher so 12v X 6 = 72

We have a double secondary so the output suppose to be 72 X 2 = 144v Now you have to consider that if the battery voltage is say 13v then the output be 13 X 6 = 78 78 X 2 = 156v
Taking all this strait forward as shown above will indicate a specified voltage which is not true in reality. As you can see from every 1 volt lost in the input you are loosing 12v on the double output winding.

This voltage drop is unavoidable because loses exist everywhere 1) in the winding itself 2) leakage inductance in the transformer 3) the switching transistors 4) the output diodes 5) The internal resistance of the battery, 6) the traces on the pcb and also the wiring from the battery to the inverter.

The first light load as you saw lost a lot of voltage and it seems that that extra voltage without load is due to some spikes that generated this voltage are stored in the output capacitor. This extra voltage is dumped very quickly when loading the smps due to that this extra voltage has a very short pulse and not strong to sustain any load.

To overcome this problem you need to compensate either from the input which is rather hard in a way as a lot of current is involved and traces must be kept short and wide as possible. You should also enhance them by putting a few 0.8mm bare copper wire and soldering them directly on the traces of the pcb to minimize resistance. I chose 0.8mm because of skin effect at 30 Khz.

The other option is to make another turn or two on the secondary to get a higher voltage and add feedback to your circuit. If you intend to add feedback you must also include an output inductor. This will store voltage during short pulse on light load. Be careful as this has to be tailored for the best compromise between low and high loads.

One last thing I like to mention if you are loading a continuous load things seem a bit harsh on the smps and the 3 farad capacitor will not work here. When loading with an amplifier this becomes a different story as the load is not continuous and now the 3 farad capacitor will come into play and will sustain the voltage much better as it will have time to charge up again between each interval of the varying load.
The output capacitor has the same effect as the input. If you try to measure the output voltage with a working amplifier you will note that the output does not change that much.

I hope this helps you understand much better

Regards Silvio

badboy_6120
06-15-2018, 09:39 AM
thank you dear Silvio

I increase each side of the secondary windings by 2 turns and the voltage drops seems to be normal now
but I have a problem now and that's when I connect 15V at the input and I get only 110V at output
and in this situation only three of the mosfets ( parallel) that are handling half of the cycle will get hot (under load) and the other side stay cool
I think it's a problem with 500 Pot that handle dead time as when I set it to different value it changes the hot and cool side

any idea?

Silvio
06-15-2018, 10:29 AM
thank you dear Silvio

I increase each side of the secondary windings by 2 turns and the voltage drops seems to be normal now
but I have a problem now and that's when I connect 15V at the input and I get only 110V at output
and in this situation only three of the mosfets ( parallel) that are handling half of the cycle will get hot (under load) and the other side stay cool
I think it's a problem with 500 Pot that handle dead time as when I set it to different value it changes the hot and cool side

any idea?

Look closely what is happening. Check the gate drive on the mosfets and see that enough voltage is arriving at the gates >10v.
If for any reason this voltage is lower than it can be the case that the mosfets are not getting fully switched on as they should and tend to heat up. Hook up the scope for this test.

It could also be that the primary winding is not symmetrical and is causing this problem. Snubbers must be fitted here across each pair. See the wave form across the primary and search for any spikes on the waveform. These may prolong the switch off of the fets or may be disturbing the wave form at the gates. The dead time can be set for 2uS and left as it is. This should be enough for the time being. The larger the dead time the more power is lost.

Regarding the 15v input it is a bit too much and it could be that the core will tend to saturate.
Are you hearing some kind of clicking or whistling noises during high power output at 15v input?
You can increase the frequency to overcome the saturation problem, try at 40Khz instead. The reason for this is that at a higher frequency less turns are needed for a given voltage. With the copper wire used in your setup skin effect is not an issue as this being only 0.25mm which can go to 100khz or more.

Regards Silvio

badboy_6120
06-15-2018, 07:23 PM
Look closely what is happening. Check the gate drive on the mosfets and see that enough voltage is arriving at the gates >10v.
If for any reason this voltage is lower than it can be the case that the mosfets are not getting fully switched on as they should and tend to heat up. Hook up the scope for this test.

It could also be that the primary winding is not symmetrical and is causing this problem. Snubbers must be fitted here across each pair. See the wave form across the primary and search for any spikes on the waveform. These may prolong the switch off of the fets or may be disturbing the wave form at the gates. The dead time can be set for 2uS and left as it is. This should be enough for the time being. The larger the dead time the more power is lost.

Regarding the 15v input it is a bit too much and it could be that the core will tend to saturate.
Are you hearing some kind of clicking or whistling noises during high power output at 15v input?
You can increase the frequency to overcome the saturation problem, try at 40Khz instead. The reason for this is that at a higher frequency less turns are needed for a given voltage. With the copper wire used in your setup skin effect is not an issue as this being only 0.25mm which can go to 100khz or more.

Regards Silvio

It turns out that the problem was from saturated transformer (as you mentioned) but I am getting 1500W without any problem with ETD59 in my half bridge smps with 1600 gauss
and as I calculated I'm running the smps with 1600W at 15V in input
(15*10^8)/(4*32000*2*3.68)

am I missing something here? because I can't get more that 800W from the transformer without going into saturation

kegs
06-15-2018, 07:29 PM
[QUOTE=Silvio;15221]Look closely what is happening. Check the gate drive on the mosfets and see that enough voltage is arriving at the gates >10v.
If for any reason this voltage is lower than it can be the case that the mosfets are not getting fully switched on as they should and tend to heat up. Hook up the scope for this test.

It could also be that the primary winding is not symmetrical and is causing this problem. Snubbers must be fitted here across each pair. See the wave form across the primary and search for any spikes on the waveform. These may prolong the switch off of the fets or may be disturbing the wave form at the gates. The dead time can be set for 2uS and left as it is. This should be enough for the time being. The larger the dead time the more power is lost.

Regarding the 15v input it is a bit too much and it could be that the core will tend to saturate.
Are you hearing some kind of clicking or whistling noises during high power output at 15v input?
You can increase the frequency to overcome the saturation problem, try at 40Khz instead. The reason for this is that at a higher frequency less turns are needed for a given voltage. With the copper wire used in your setup skin effect is not an issue as this being only 0.25mm which can go to 100khz or more.

Regards Silvio[/QUOT

The original diagram can be found @ http://sound.whsites.net/ Project 69

Silvio
06-16-2018, 05:54 AM
Hi bad boy well saturation will only occur if there is not sufficient number of turns,

What is keeping you to try the inverter at a higher frequency? Try that and see if there is the same effect.

If you have the same result I am afraid you have to add another turn to the primary winding

Silvio

Silvio
06-16-2018, 06:03 AM
@kegs

@ kegs The circuit you mention on the link sent is a low power smps for a preamp (project 69)
Link http://sound.whsites.net/project69.htm

badboy_6120
06-16-2018, 06:21 AM
Hi bad boy well saturation will only occur if there is not sufficient number of turns,

What is keeping you to try the inverter at a higher frequency? Try that and see if there is the same effect.

If you have the same result I am afraid you have to add another turn to the primary winding

Silvio

Hi

actually the project I'm working on is from here but with some modifications I made
http://sound.whsites.net/project89.htm

higher frequency means lower flux density and lower power in the output and also if I want to add more turns in primary then I have to lower frequency as well (to even below 20khz), am I right?
do you have any idea what I'm doing wrong here? do you have any powerful inverter that can withstand this much power (around 1Kw)

badboy_6120
06-16-2018, 06:28 AM
can I go lower than 20Khz in frequency ao that I could go with 4+4 turns in primary??
doesn't this effect amplifier or produce any noise on it

badboy_6120
06-16-2018, 12:47 PM
@dear Silvio
Doesn't saturation only ralated to flux density?
Does it mater to have more or less turns on primary as long as you keep flux density the same by changing the frequency??
I did as you suggested and increase the frequency and thus lower gauss on transformer and then the transformer saturation goes away but the voltage drop is higher and no matter what I did I couldn't get more than 500W from the smps

Silvio
06-16-2018, 08:04 PM
@badboy

Yes indeed the higher the flux density the better the magnetic field and the better output. Care must be taken not to exceed a certain limit as the magnetic field will collapse and the core will saturate.
I told you to raise the frequency so that to avoid saturation and as you noticed the magnetic field dropped also and less power was transferred.

I think you have a coupling issue here and it may be the case that 2 turns are not providing enough coupling with the other windings.
Another option for you is to make another turn or two in the primary so that you have better coupling. The flux density will decrease a bit but you can raise it again by creating a small gap between the cores. This will lessen the inductance again to the normal value for the frequency used.

It would be a good practice if you measure the inductance of the primary before dismantling the transformer so that you will know what is the value. By making a small spacer between the cores when the new winding is finished you can bring the same value or maybe a little higher than the present value with 2 turns. The small gap will also help the core to withstand more flux before saturation.
The secondary turns have to be adjusted according to the new primary turns so that you will have the same output voltage.

One last thing you should test before dismantling the transformer is to make a small gap (2 pieces of paper thick) on the three legs between the cores and run the smps at 40Khz and see what you get and see if it still saturate.

Regards Silvio

badboy_6120
06-19-2018, 07:20 AM
@badboy

Yes indeed the higher the flux density the better the magnetic field and the better output. Care must be taken not to exceed a certain limit as the magnetic field will collapse and the core will saturate.
I told you to raise the frequency so that to avoid saturation and as you noticed the magnetic field dropped also and less power was transferred.

I think you have a coupling issue here and it may be the case that 2 turns are not providing enough coupling with the other windings.
Another option for you is to make another turn or two in the primary so that you have better coupling. The flux density will decrease a bit but you can raise it again by creating a small gap between the cores. This will lessen the inductance again to the normal value for the frequency used.

It would be a good practice if you measure the inductance of the primary before dismantling the transformer so that you will know what is the value. By making a small spacer between the cores when the new winding is finished you can bring the same value or maybe a little higher than the present value with 2 turns. The small gap will also help the core to withstand more flux before saturation.
The secondary turns have to be adjusted according to the new primary turns so that you will have the same output voltage.

One last thing you should test before dismantling the transformer is to make a small gap (2 pieces of paper thick) on the three legs between the cores and run the smps at 40Khz and see what you get and see if it still saturate.

Regards Silvio

@Dear Silvio

So I place a gap in the core legs and it did help a bit but not a lot (I could get about 50W more in the output) and transformer still makes a click sound and voltage at output drops and mosfets at one sides of primary get really hot while the other side stays cool
I even increase the primary turns (4+4) and still the same result
Maybe it's my winding configuration????
I winded the 2 primaries winding clockwise and then the secondaries counter Clockwise
1---> 4 Turn of Primary
2---> 4 Turn of Primary
3---> 26 Turn of secondary
4---> 26 Turn of secondary

Silvio
06-19-2018, 08:19 AM
@badboy

Well getting 1KW at 12v is not so easy because there is a lot of current involved (80 amps) losses tend to rise drastically. Having doubled the primary turns you can increase the gap to 1mm that is you make a 0.5mm gap between the 3 legs and see how it goes.

You would have been better off if you started with 24volts at least there will be half the current involved. I never made an inverter this big and I am trying to help you the best I could.

What I have seen from commercial inverters is that they use several cores like 2 or 4 cores then the output will be in series to get the voltage needed. The load this way will be divided between the cores and the each will see half or quarter the current depending on the number of cores in the setup.

Winding configuration is like this:-

first secondary winding start at pin wind 26 turns then center tap then continue from center tap and wind another 26 turns and finish at the other pin.
put 3 layers mylar tape

Primary winding start at pin wind 4 turns and then center tap . second half of primary start from center tap continue wind the second half 4 turns the same direction of the first 4 turns and finish at other pin

It is important that you wind the same direction either clockwise or anti clockwise. Try to fit windings in a single layer to help for good coupling.

Can you post some scope shots of both channels during load?

Regards Silvio

badboy_6120
06-19-2018, 09:41 AM
@badboy

Well getting 1KW at 12v is not so easy because there is a lot of current involved (80 amps) losses tend to rise drastically. Having doubled the primary turns you can increase the gap to 1mm that is you make a 0.5mm gap between the 3 legs and see how it goes.

You would have been better off if you started with 24volts at least there will be half the current involved. I never made an inverter this big and I am trying to help you the best I could.

What I have seen from commercial inverters is that they use several cores like 2 or 4 cores then the output will be in series to get the voltage needed. The load this way will be divided between the cores and the each will see half or quarter the current depending on the number of cores in the setup.

Winding configuration is like this:-

first secondary winding start at pin wind 26 turns then center tap then continue from center tap and wind another 26 turns and finish at the other pin.
put 3 layers mylar tape

Primary winding start at pin wind 4 turns and then center tap . second half of primary start from center tap continue wind the second half 4 turns the same direction of the first 4 turns and finish at other pin

It is important that you wind the same direction either clockwise or anti clockwise. Try to fit windings in a single layer to help for good coupling.

Can you post some scope shots of both channels during load?

Regards Silvio


Here you go

This pictures are from the side of primary that the mosfets connected to it gets really hot with high load :
Without any load :
6707
With 37.5 Ohms load :
6708

The other side of primary that stays cool:
Without load:
6707
With 37.5 Ohms load :
6709

Silvio
06-19-2018, 06:20 PM
Here you go

This pictures are from the side of primary that the mosfets connected to it gets really hot with high load :
Without any load :
6707
With 37.5 Ohms load :
6708

The other side of primary that stays cool:
Without load:
6707
With 37.5 Ohms load :
6709

I want to know where are you putting your probe is it on the gate of the IGBT or the ptrimary winding?

The first picture shows a beautiful wave form the the custom sloping trailing edge of an IGBT switch. Is this the full output winding or the input?

The side that is getting hot shows a very disturbed wave form and that is causing the heating of the IGBTs.

Please post pics with the probes on the gates. The signal must be clean here otherwise you will never get a good waveform on the output.

As the topology you are using is push pull then you can switch the gate wires if you have not done a pcb yet.

As you can notice There is ringing at the disturbed wave form when the IGBT is fully switched on, You must use a suitable snubber to calm things down, The more load you draw the more ringing you will get. avoid long wires or traces to the gates and away as possible from high current paths. These are to be at 90 degrees to the current path where possible to eliminate coupling. A double sided pcb with a ground plane will isolate any stray inductances that may couple to the gate drive.

Check your dead time and set for at least 2uS this will give either transistors time to fully switch off before the next turn on. You can make it less after things will be stable. Try also a piece of screened cable to drive the gates to eliminate any stray coupling. Use a gate emitter resistor of 1k to eliminate any false trigger.

If all this will not help then it could be a case of symmetry in the input winding. Push pull is very specific and the primary has to be uniform and symmetrical as possible otherwise you will be in for surprises.

I will send you some pics later of a commercial inverter of 3kw???? (I doubt it) to see how they make the ferrite cores.

Please post pics of probe at the gates and also at primary winding. if possible use two probes at the same time so that I see both channels together. (one time at the gates and one time at the windings)

Regards Silvio

Silvio
06-19-2018, 07:33 PM
@Badboy

Here is a PDF file with some pics of a 3K inverter PS it never reached 3K

6711

badboy_6120
06-20-2018, 05:15 AM
I want to know where are you putting your probe is it on the gate of the IGBT or the ptrimary winding?

The first picture shows a beautiful wave form the the custom sloping trailing edge of an IGBT switch. Is this the full output winding or the input?

The side that is getting hot shows a very disturbed wave form and that is causing the heating of the IGBTs.

Please post pics with the probes on the gates. The signal must be clean here otherwise you will never get a good waveform on the output.

As the topology you are using is push pull then you can switch the gate wires if you have not done a pcb yet.

As you can notice There is ringing at the disturbed wave form when the IGBT is fully switched on, You must use a suitable snubber to calm things down, The more load you draw the more ringing you will get. avoid long wires or traces to the gates and away as possible from high current paths. These are to be at 90 degrees to the current path where possible to eliminate coupling. A double sided pcb with a ground plane will isolate any stray inductances that may couple to the gate drive.

Check your dead time and set for at least 2uS this will give either transistors time to fully switch off before the next turn on. You can make it less after things will be stable. Try also a piece of screened cable to drive the gates to eliminate any stray coupling. Use a gate emitter resistor of 1k to eliminate any false trigger.

If all this will not help then it could be a case of symmetry in the input winding. Push pull is very specific and the primary has to be uniform and symmetrical as possible otherwise you will be in for surprises.

I will send you some pics later of a commercial inverter of 3kw???? (I doubt it) to see how they make the ferrite cores.

Please post pics of probe at the gates and also at primary winding. if possible use two probes at the same time so that I see both channels together. (one time at the gates and one time at the windings)

Regards Silvio

@ Dear Silvio

Here's a video clip from the Gate of mosfets at the same time according to Negative :

https://youtu.be/na7jK3TaPWM

Here's some shots of the transformer primaries at the same time according to Positive :
both channel is on 0.5 Volt/Div and X10 on probe.
6712
6713

The same test with different Volt/Div for one of the primaries (the little one is the side that its mosfets gets hot):
6714
6715
The large Signal is on 2 Volt/Div and its probe on X10
The small Signal is on 0.5 Volt/Div and its probe on X10

badboy_6120
06-20-2018, 05:21 AM
Here's the PCB that I'm using for this project:

badboy_6120
06-20-2018, 06:51 AM
Sorry about the previous video, there was a ground issue in the measurements
here's the right one :


https://youtu.be/1-aT29eX7GA

Turn's out that the voltage pulses from one channel of the SG3525 is going low at high power (The one that drives those stone Cold mosfets)
So it's a drive issue, am I right???

Silvio
06-20-2018, 08:45 PM
@Badboy

What you did not post is with the probes at the gates with the inverter on load. If you have a disturbed gate drive on load you will not get a good wave shape on the output. A bad wave form will cause heating of the IGBT
The pcb is confusing and you have a lot of links which are not shown.
Why did you position the igbt across? How are you going to fit the heat sink? Or you going to fit a flat heat sink under the pcb?
I see gate resistors and traces parallel to the high current paths these will couple stay inductance and disturb the wave form.
I suggest you put the sg and signal circuit on a separate pin header to lift it off the pcb for less coupling to the high current paths

Regards Silvio

badboy_6120
06-20-2018, 09:01 PM
@Badboy

What you did not post is with the probes at the gates with the inverter on load. If you have a disturbed gate drive on load you will not get a good wave shape on the output. A bad wave form will cause heating of the IGBT
The pcb is confusing and you have a lot of links which are not shown.
Why did you position the igbt across? How are you going to fit the heat sink? Or you going to fit a flat heat sink under the pcb?
I see gate resistors and traces parallel to the high current paths these will couple stay inductance and disturb the wave form.
I suggest you put the sg and signal circuit on a separate pin header to lift it off the pcb for less coupling to the high current paths

Regards Silvio

the last video I uploaded was from the gates of mosfets at the same time
when I connect the load one side of primary's mosfets gate voltage drops and that is why it's stone cold and the other sides decrease a bit but that normal under load
why this happening??
buy turning the dead time trimmer clockwise or counter clockwise the mosfets that gets hot change position with mosfets on the other half of primary

I'm tempted to go with Full Bridge configuration instead of push pull
I think I can get more power out of a Full Bridge

Silvio
06-21-2018, 03:51 AM
the last video I uploaded was from the gates of mosfets at the same time
when I connect the load one side of primary's mosfets gate voltage drops and that is why it's stone cold and the other sides decrease a bit but that normal under load
why this happening??
buy turning the dead time trimmer clockwise or counter clockwise the mosfets that gets hot change position with mosfets on the other half of primary

I'm tempted to go with Full Bridge configuration instead of push pull
I think I can get more power out of a Full Bridge

The reason for all this has to be found. Start tracing the signal where is it stopping. if its from the IC then try to change it, decouple the supply rail as closely as possible to the IC pins, Make a separate pin header and change pcb.

I am surprised how you manage to get 500w with only one side working.

Full bridge will be the same as push pull as far as power is concerned with the only difference that you will only have one primary of 12v instead of two and duty cycle on the winding will double.

badboy_6120
06-21-2018, 05:16 AM
The reason for all this has to be found. Start tracing the signal where is it stopping. if its from the IC then try to change it, decouple the supply rail as closely as possible to the IC pins, Make a separate pin header and change pcb.

I am surprised how you manage to get 500w with only one side working.

Full bridge will be the same as push pull as far as power is concerned with the only difference that you will only have one primary of 12v instead of two and duty cycle on the winding will double.

the 500W is before the transformer saturation and is that situation all mosfets heat normal

Full brige does not suffer from staircase saturation and gives some forgiveness on how primary windings is winded

Silvio
06-21-2018, 10:50 AM
the 500W is before the transformer saturation and is that situation all mosfets heat normal

Full brige does not suffer from staircase saturation and gives some forgiveness on how primary windings is winded

What can I say? well you need 4 fets for full bridge and 4 gate drives more complicated as it seems. If you are willing then try it see what happens.

badboy_6120
07-04-2018, 08:23 PM
@Silvio

I manage to build a 1kw converter with full bridge topology
I need to know what is the lowest voltage I should design the converter for when car is running?
as I measure the voltage before in car idle condition the voltage was around 14.7v without any load
so how much drop should I expect from a 90A alternator under high load?

Silvio
07-04-2018, 10:09 PM
@Silvio

I manage to build a 1kw converter with full bridge topology
I need to know what is the lowest voltage I should design the converter for when car is running?
as I measure the voltage before in car idle condition the voltage was around 14.7v without any load
so how much drop should I expect from a 90A alternator under high load?

It all depend on a few things to be considered. The cable thickness and also how long it is. 70 amps load will impose a voltage drop in the cables for sure. Well off hand I think there will be around 1.5 to 2 volts drop with good thick cables. A large capacitor at the amplifier side will help out to give the current when needed to give that extra punch. I think the worst case should be 12v with the engine running around 1500 revs.

The full bridge version seems to work because now you are using only one winding and there is no symmetry problem, however the duty cycle and also the current in one winding is nearly double than that of a push pull configuration. The switching transistors have to be also double than that of a push pull topology as each side of the bridge now use two transistors in series.

Good luck

badboy_6120
07-05-2018, 05:55 AM
It all depend on a few things to be considered. The cable thickness and also how long it is. 70 amps load will impose a voltage drop in the cables for sure. Well off hand I think there will be around 1.5 to 2 volts drop with good thick cables. A large capacitor at the amplifier side will help out to give the current when needed to give that extra punch. I think the worst case should be 12v with the engine running around 1500 revs.

The full bridge version seems to work because now you are using only one winding and there is no symmetry problem, however the duty cycle and also the current in one winding is nearly double than that of a push pull configuration. The switching transistors have to be also double than that of a push pull topology as each side of the bridge now use two transistors in series.

Good luck

No i meant the voltage drop on alternator as we're drawing 70A from it
I know about the drops from alternator to the amp

Silvio
07-05-2018, 09:04 AM
@badboy

If the alternator is capable of delivering 90 amps then it should be strong enough to give the full voltage at 70A with adequate revs from the engine. The voltage regulator in the alternator will do this job.

badboy_6120
07-05-2018, 10:31 AM
@badboy

If the alternator is capable of delivering 90 amps then it should be strong enough to give the full voltage at 70A with adequate revs from the engine. The voltage regulator in the alternator will do this job.

thanks man

badboy_6120
09-05-2018, 05:25 AM
Hi again

I manage to build a full bridge inverter to drive my amplifier in the car
everything is good except mosfet's overheating under load
here's a picture of primary transformer without any output load :
*** Oscilloscope Volt/Div is on 2 (((Channel 2))) and the probe is set to X10


6784

and here's a picture of primary transformer with 500W load:
6785

Could those sparks be the cause of mosfets overheating ?????

Silvio
09-06-2018, 05:35 AM
@badboy

Mosfet current rating should be 3 times the operating current. EX, for 3 amp load max current of mosfet is 9 amp.

voltage spike will not help either, did you try to suppress it?

badboy_6120
09-06-2018, 07:45 AM
@badboy

Mosfet current rating should be 3 times the operating current. EX, for 3 amp load max current of mosfet is 9 amp.

voltage spike will not help either, did you try to suppress it?

I use two IRF1404 in parallel at each channel
at 500W in the output there should be around 40A in input going through the masfets!!!!

I used snubber as well to controll those sparks and I did eliminate them but the overheating is still there

Silvio
09-06-2018, 07:10 PM
I use two IRF1404 in parallel at each channel
at 500W in the output there should be around 40A in input going through the masfets!!!!

I used snubber as well to controll those sparks and I did eliminate them but the overheating is still there

Did you buy genuine transistors? Be careful as it happened to me. I bought IRF740 from aliexpress and also E-bay and they where fakes. They could not withstand the current and at only 1/3 the current they where getting very hot.

I Broke one of them in the vice and saw that the die was half the size than a genuine one.

Note A mosfet is made from a lot of small mosfets in parallel diffused on the same die. If the die is small then there is not the amount there should be hence the current rating will suffer.

I have a video on Youtube where I found a way to check them by measuring the internal capacitance. (The more capacitance the more fets there are on the chip)

Lastly IRF1404 can withstand 115 amps at a case temperature of 100 degrees Celsius. They are suppose to handle the load very easily.

Here is the link https://www.youtube.com/watch?v=gRRfb5YxvIA

Regards Silvio

badboy_6120
09-07-2018, 11:29 AM
Did you buy genuine transistors? Be careful as it happened to me. I bought IRF740 from aliexpress and also E-bay and they where fakes. They could not withstand the current and at only 1/3 the current they where getting very hot.

I Broke one of them in the vice and saw that the die was half the size than a genuine one.

Note A mosfet is made from a lot of small mosfets in parallel diffused on the same die. If the die is small then there is not the amount there should be hence the current rating will suffer.

I have a video on Youtube where I found a way to check them by measuring the internal capacitance. (The more capacitance the more fets there are on the chip)

Lastly IRF1404 can withstand 115 amps at a case temperature of 100 degrees Celsius. They are suppose to handle the load very easily.

Here is the link https://www.youtube.com/watch?v=gRRfb5YxvIA

Regards Silvio

as you said I checked the output capacitance of my mosfets and I get about 8.7 nf
I think they are good to go

Silvio
09-07-2018, 12:01 PM
as you said I checked the output capacitance of my mosfets and I get about 8.7 nf
I think they are good to go

You cannot tell exactly until you make some comparisons with a known genuine fet. The input capacitance tend to vary according to frequency and voltage of operation.

Do they get hot at a lower load say at 20A? Do not get fooled about the parameters as current is always limited in these fets especially if they are in TO220 package. The transistor leads themselves cannot carry more than 60 to 70 amps and they must be kept as short as possible. The traces at the pcb should be wide as possible to eliminate any heating.

If all seems good and wave form, frequency, flux density etc then it could be the fets themselves not capable for the load.

I would like you to check the voltage at the gates when operation on high load. See that it is not dropping in any way especially the high side gate. See also that you have adequate dead time.

Silvio

badboy_6120
09-07-2018, 04:10 PM
Thanks Dear Silvio for your helps

So it turned out that my multi meter was reading incorrectly (Broken) and the temp on the back metal part of mosfets never reach 50 degrees with a low value snubbers (I use another multi meter)
So now I need to know how exactly I can choose the best values for my snubbers????? (As I see experimentally higher the value of Capacitor in snubbers between Drain @ Source, Lower the amount of Sparks and therefore less heating on mosfets)

I manage to draw my Schematics and also took some pictures of my project:

6786

6787
6788
6789
6790
6791


Could you also look at the schematic and see if there is any problem with it??????
Thank you

badboy_6120
09-07-2018, 05:35 PM
I also use one 2.7 ohms resistor for every two mosfets parallel in every channel
should I use a higher resistor value or use a seperate resistor for each one of the 2 parallel mosfets??

Silvio
09-07-2018, 08:00 PM
Hi Badboy

The project looks quite fine but I think you can arrange a bit the layout of the PCB. I do not know if space is very important or not but I think fitting the trafo on the main pcb near the switching transistors will be better and have shorter leads. I think you can make the control circuit on a separate board and fitted with a pin header. You can also make more than one pin header. This will save you space and get also low profile.

I am glad you found the problem, 50 degrees is very normal operating temperature.

Regarding gate resistors I think using a separate resistor for each fet will be a better choice thus the gate charge will be more equal to each fet. Doing it this way you will need to use a 6 ohm resistor with each fet thus having them in parallel will bring the total resistance of 3 ohms which is seen by the IR2110

Some considerations for gate resistor and snubbers. I have a blog post here and shows step by step how to work out the gate resistor value according to the fets used and current handling of the fet driver (IR2110 in your case) This chip can deliver a maximum of 2amps of drive current so this must not be exceeded. Do not forget to double your values as now you have 2 parallel fets . You will also find how to calculate and adopt a simple resistive and capacitive snubber for the smps in the same blog post. Download the pdf in the post its all explained there.

Link http://www.diysmps.com/forums/entry.php?147-Calculation-of-snubber-components-and-driver-gate-resistors


regards Silvio

badboy_6120
09-08-2018, 12:23 PM
thank you for your tips

I used 2 seperate 6 ohms resistors for 2 parallel mosfets and this lower down the amount of sparks
I still need to use some snubbers
I will calculate the values using your PDF as soon as I can
Thanks again

badboy_6120
09-09-2018, 04:30 PM
@dear silvio

could you help me calculate the right gate resistor for mosfets
I don't know 2 things
first one what are the correct values for rise time and fall time of IR2110?
6792

second what happens when I use two mosfets in parallel? (should I double the calculated value)
I'll appriciate any help

badboy_6120
09-09-2018, 07:41 PM
should I take 150 or 35 as T on??

Silvio
09-10-2018, 07:43 AM
Hi badboy
I worked it out for you.
The total equivalent gate resistance should not exceed 4.7 ohms for IR2110 so in your case having 2 fets in parallel the resistor for each gate should be 10 ohms.

badboy_6120
09-10-2018, 05:01 PM
thanks a lot
if it's possible could you tell me how did you get 10 ohms from the formula?
I mean what values did you use from the datasheet

Silvio
09-10-2018, 10:00 PM
Hi badboy

The prorogation delay is the time for the IR2110 to react when given a pulse from the SG3525. we don't take that into consideration.

You will use the turn on rise and fall time instead using the typical value. In this case 25nS and 17nS

We also use the total gate charge of the fet used in this case take the average of 180nC (160nC-200nC)

I re-worked the math for you as I found a small mistake and re calculated all. I adjusted also for 2 parallel fets having around 0.9amps of current each so this brings a total of around 1.8 amps on the IR2110 at 13.5v. This voltage of 13.5v is more realistic considering some voltage drop in the wiring and connections etc. However at 14.7v this brings a maximum of 1.96amps to the IR2110.

The total switching time of t-on plus t-off plus fall time of IR2110 came to 440nS or 0.44mS which is very good. With a dead time of 1uS you will have more than 50% time until the next switching cycle. This will also give ample time for the core to discharge all its magnetic flux.

The gate resistor to each fet is to be 15 ohms so IR2110 will see a combined resistance of 7.5 ohms ( 13.5v / 7.5 ohms = 1.8 amps)

I cannot show my working as its such a pain in the a.......rs to write it all down. With the figures I gave you you can plug them in the formulas and you will arrive with the same answers.

Regards Silvio

badboy_6120
09-11-2018, 10:01 AM
thanks man
I get it now
I appriciate your helps

badboy_6120
09-14-2018, 01:19 PM
So I replace the gate resistors with 15 ohms resistors for each fets and now the fets reaches to 50 degrees at 600W load
now there's a problem with current transformer for protection board and it's getting really hot under load
I used a yellow toroidal core from pc power supply
should I use different core for this much current passing through it?

Silvio
09-14-2018, 07:50 PM
So I replace the gate resistors with 15 ohms resistors for each fets and now the fets reaches to 50 degrees at 600W load
now there's a problem with current transformer for protection board and it's getting really hot under load
I used a yellow toroidal core from pc power supply
should I use different core for this much current passing through it?

If you want to check that the gate resistors are good just check the voltage at the gate to source with the scope. If the voltage is above 10 volts than the gate resistors are good at that value. 50 degrees on the fets is not so much you can add fan to cool things up. You may be pulling around 60 amps from the battery at 600w at 80% efficiency. Are you pulling a continuous load? or with amplifier?

Regarding current trafo it may be the case that you have too much turns on the secondary of the current trafo. Make less turns and put a load resistor according to the tripping voltage wanted in your smps. It is not the current passing but the load on it with the secondary turns and load resistor.

badboy_6120
09-15-2018, 03:24 AM
If you want to check that the gate resistors are good just check the voltage at the gate to source with the scope. If the voltage is above 10 volts than the gate resistors are good at that value. 50 degrees on the fets is not so much you can add fan to cool things up. You may be pulling around 60 amps from the battery at 600w at 80% efficiency. Are you pulling a continuous load? or with amplifier?

Regarding current trafo it may be the case that you have too much turns on the secondary of the current trafo. Make less turns and put a load resistor according to the tripping voltage wanted in your smps. It is not the current passing but the load on it with the secondary turns and load resistor.

I will check the gate voltage of the fets as soon as I get home

about the current trafo
The core gets really hot (only when smps is under load) without any secondary winding on it ( just the primary winding of the ETD59 going through it)
I tested a few core that I have and the only core that didn't get warm was a green core but when I test this green core, the protection board kick in as soon as I release the high load from the output of the smps (when I connect a low resistance to smps output and hold it there, it dosen't triger the protection board but as soon as I release the load protection board react and cut the power)
I tried different secondary turns on current trafo but with same result
This only happened when I use the green core

thank you again for all your helps

Silvio
09-15-2018, 07:51 AM
I will check the gate voltage of the fets as soon as I get home

about the current trafo
The core gets really hot (only when smps is under load) without any secondary winding on it ( just the primary winding of the ETD59 going through it)
I tested a few core that I have and the only core that didn't get warm was a green core but when I test this green core, the protection board kick in as soon as I release the high load from the output of the smps (when I connect a low resistance to smps output and hold it there, it dosen't triger the protection board but as soon as I release the load protection board react and cut the power)
I tried different secondary turns on current trafo but with same result
This only happened when I use the green core

thank you again for all your helps

Current trafo

It could be the case due to the high current involved you can use a low value resistor (current shunt) instead or even a piece of wire to form a small loop or a small coil to get to the desired length. This all depends on the material used for the high current resistor.

A few suggestions for the material are:- Brass brazing rod, A piece of eurica wire from a thick heater filament, a piece of copper wire, piece of stainless steel wire, piece of steel wire etc.
These type of shunts that I am mentioning will bring the need to alter the protection circuitry as the voltage drop across the shunt is very small and I guess the circuit will have to be altered a little to adjust the reference voltage at the LM393.

One other option is to sense the output instead with a small resistor like 0.1 ohm and measure the voltage across instead. Here it would be easier as you only have DC to deal with and there will not be the need for a diode to rectify the voltage thus avoiding the the voltage drop in the diode itself. You have less current to deal with at the output.

Regarding the false trigger during the load release well this may be cured with a small capacitor across the load resistor (secondary coil) like 1uF or so. Use the minimum until you get rid of this false trigger as the capacitor will somehow delay the operation of overload. You can also try to change the small 330pf cap entering pin 2 of LM393 to 0.1uf.

Silvio

badboy_6120
09-20-2018, 06:59 AM
Current trafo

It could be the case due to the high current involved you can use a low value resistor (current shunt) instead or even a piece of wire to form a small loop or a small coil to get to the desired length. This all depends on the material used for the high current resistor.

A few suggestions for the material are:- Brass brazing rod, A piece of eurica wire from a thick heater filament, a piece of copper wire, piece of stainless steel wire, piece of steel wire etc.
These type of shunts that I am mentioning will bring the need to alter the protection circuitry as the voltage drop across the shunt is very small and I guess the circuit will have to be altered a little to adjust the reference voltage at the LM393.

One other option is to sense the output instead with a small resistor like 0.1 ohm and measure the voltage across instead. Here it would be easier as you only have DC to deal with and there will not be the need for a diode to rectify the voltage thus avoiding the the voltage drop in the diode itself. You have less current to deal with at the output.

Regarding the false trigger during the load release well this may be cured with a small capacitor across the load resistor (secondary coil) like 1uF or so. Use the minimum until you get rid of this false trigger as the capacitor will somehow delay the operation of overload. You can also try to change the small 330pf cap entering pin 2 of LM393 to 0.1uf.

Silvio

Fix the problem with just letting a quarter of primary winding going through the yellow current trafo
now the protection board working perfectly and there's now heating on current traso as well