Transformer winding

[golam]

For Areza,
I am talking about square wave inverter. For square wave, rms value and peak value is same. So no need to convert to 310 volts. Since sg3535 is having adjustment capability through feedback from the output, no need for worrying for load variation.
For modified sine wave to run inductive load, one require to add dead time in between two phases for creating difference between rms and peak value and in this case(for modified sine wave) you require to convert 310v dc to 220v ac. And of course for sine wave inverter, you require to convert 12v dc (or any value dc) to 310 or more volt dc and then convert that high volt dc to 220 v sine wave ac through full bridge circuit without any transformer.
For using square wave ips for inductive load, one requires to use both resistive and inductive load. Then there will not be any problem.

 

[golam]

For Tahmid,
I tried with transformer for full bridge and faced lot of problem as the gate driving signals through transformer is not as efficient as gate driving dedicated ics. You can try but if you ask me, I will advocate to use dedicated gate driving ics.

 

[luka]

hi luka , i m looking for a trafo gate driver which can work 0-100% duty cycle, like driving a class d amp for music , can u help me with this, thanks in advance

I think it can't be done, even with IR you would have to have better, by that I diffrent supply then normaly, to have 100% D.C.
Well trafo won't work this way anyway, since trafos can't transfer DC from primary to secondary (100% D.C.)

 

[cerrem]

For that type of core you want to stay under 300mT for your max Flux density...when operating bewteen 100kHz to 200kHz range...
Also...with Forward converter make sure to use a reset winding or a resonant reset....this way you must start at origin for each cycle...

CHris

 

[luka]

Luka, is it not easier, less troublesome and more convenient to use dedicated gate driver ICs instead of using transformer for gate driving.
ICs have in-built system of making floating ground for high side MOSFET driving. But if we use transformer, should we use three separate transformers or three separate windings for ensuring floating ground for high side MOSFET driving.
It is easier to use ICs like IR2110 instead of the troublesome transformer. Is that not true?

I agree, with IC is way more simple. With trafo(you would have only one), you have primary that is somehow driven by SG or what you are using, and 4 secondarys, each for one fet, but I would go here with NPN transistors, like Mje 13009, which Eva says that are very good, are very cheap and small, they will have less dissipation then high voltage fets, probably because of their Rsd(on), which is higher as component is cheaper, you sure won't pay 10€ or in other words a lot of money for single fet to have low ON resistance...

 

[luka]

I have got the information from Tauscher Co. of Germany which produce good quality cores. I have collected some of their etd/ecr cores from China and used for my inverters. I used them for making 250 watt capacity ips. Those information from Tauscher Co. may be for continuous duty and for using 2/4 hours for ips, I think more wattage can be produced as duty cycle is less.
I tried to make 600 watt with those core with 80 KHZ but it becomes very hot and I am reverted back to 250/300 wattage.
For safe use over 500 watt, one require to use ETD-44 core- according to the Company.

Everybody said that I won't be able to get power that I wanted from my ETD44, even when Eva show, after that I did too, that you can get more from core then it was writen on internet. I NOT saying that that company gives wrong info, but you just have to try for yourself

From Eva: At 36Khz, 2KW from two E42/21/20

And this is not way bigger core then what you have, I think...

 

[luka]

For Tahmid,
I tried with transformer for full bridge and faced lot of problem as the gate driving signals through transformer is not as efficient as gate driving dedicated ics. You can try but if you ask me, I will advocate to use dedicated gate driving ics.

You used fets, like I said use NPN, every PC psu works this way and it is great

 

[Tahmid]

Posted by Luka



I agree, with IC is way more simple. With trafo(you would have only one), you have primary that is somehow driven by SG or what you are using, and 4 secondarys, each for one fet, but I would go here with NPN transistors, like Mje 13009, which Eva says that are very good, are very cheap and small, they will have less dissipation then high voltage fets, probably because of their Rsd(on), which is higher as component is cheaper, you sure won't pay 10€ or in other words a lot of money for single fet to have low ON resistance...

Why MJE13009 NPN transistor rather than MOSFET?
While using MJE13009, we must give a base current of 1Amp to be able to get an output of 5A. But while using MOSFET, for getting same output we require to provide only a few milliamps to the gate. So, it is easier to make electronic circuits with MOSFETs, rather than NPN transistors because 1A base current is hell lot of current for an electronic circuit. Instead of using current-mode transistor, it is preferable to use voltage-mode MOSFET, I think.

Moreover, we are getting ready-made totem pole gate drivers inside the SG3525, which costs US$0.5 only in Bangladesh. MOSFET is also very cheap here, only US$0.5-1.5, depending on power capability.

 

[luka]

Hi

Is it a problem for trafo to make 1A for Ib? it is way harder to have 12v for gate voltage then make 1A fot base, no problem with noise, to low voltage, oscilations and when current stops, colector/emitor current stops... If you would use MJE I think you should use trafo, or it will be harder to drive. And 1A is really nothing, coz 1A at say 1v of BE voltage is nothing... Fet needts at turn on more, say 12v^2/22R(gate resistor)= 6.5w... even if only at the beginning...it is not hard...you should try if you arent time limited too much, you can always go back to IR...+ it would be something fresh to see usage of gate trafo in designs on this forum. And because you have full bridge, where is best to use it, since you have so many fets, floating points...

You still will use SGs output, to drive trado directly... fets are cheap...which ones will you use/how much will they cost you if you do use them?

PS: only 0.5$ for SG? damn don't do this, I will buy them from there

 

[golam]

For luka,

Yes, NPN Transistors can be used but think about Base current. In an electronics circuit, if you get your required output with providing mA instead of providing some A current, which is preferable? I consider Mosfets. If anyone prefer Transistors, he can find out ESBT from ST Microelectronics, where he can utilize that Transistor with the same mA of current like Mosfets applying to the gate/base of ESBT(Emitter Switched Bipolar Transistor).

 

[golam]

ESBT does not require gate driver. It is like all other normal transistors.

 

[areza]

for 50hz dc-ac inverter , there are cheap solution , no need to use those expensive ir2110 driver cost more then all 4 mosfet used in full bridge , and will explode with the mosfet on the event of a failure,

ir2110 is good (price to performance) for say >20khz hard switching application , and has limited gate driving current,

 

[luka]

Hi

All is relative, I don't mind 1A for base current. This is no down fall, what will you gain by using fets that as you say need only mA. Is it hard to creat 1A with trafo? trafos are way better when it comes to error, they don't explode or anything. Don't get me wrong I used IR too, it is just simple to understand and it works great, not much components around it. But with 50Hz freq., which is low for IR, you would need big C for upper gate drive.

To be short: what Areza said!
PS: you could make your own driver, like UCD has, it is IR but with discrete components

 

[areza]

hi luka, i m agreed with u , i want to use trafo for both 50hz and 20khz , with variable duty cycle(say 0-100% again), is there any way to do it with trafo, thanks

 

[luka]

Hi

No, not for 100% for sure, if you put DC on primary trafo will in xx time have 0v on secondary, while it should have voltage.... so if you need 100% D.C., let say almost all the time on, very little off, trafos are not good. Why do you need 0 and 100%?
I mean do you really need from 0 to 100? or would be 5 to 95 ok?

 

[areza]

hi luka, i want to build a class d amp with trafor for music , is there any way useing trafo , or some thing else like opto may be, i was looking all over the class d forum without any luck, but i m sure there is some way,

 

[Alexsch]

On MOS vs BJT

In 2008 using a MJE13009 BJT instead of MOS is like giving up a BMW750 for a horse drawn cart. Even the very cost sensitive lamp ballast circuits are moving to MOS. Decent base drive of the BJT at >30KHz are a difficult circuit to design and it needs some tweaking to get it right. On MOS: give it 10V gate pulse, and add some 5ohm de-Qing resistor.

 

[luka]

hi luka, i want to build a class d amp with trafor for music , is there any way useing trafo , or some thing else like opto may be, i was looking all over the class d forum without any luck, but i m sure there is some way,

Well I am not sure, if you would have low freq. for say sub amp, you may be able to use it, but for amp I would and I did use IR, it is just more simple, trafos are best in supply. And you don't need 0-100% duty cycle, you can use only 25-75%, and because of this use higher bus voltage so D.C. has to change less then with lower bus voltage to produce same output voltage

 

[luka]

Hi Alexsch

Why would you not compare them? I mena most can't get brand new fets, they aren't cheamp,... + people use what is proven to work great. Why would you force fets in say full bridge supply if you can get better performance with damn old components like MJE.

All I am saying fets are getting better, but shops still sell only 10 or more years old fets, coz they *work*...hell I would want new fets, but hell if they don't buy them, I can't, and I live in EU not say in africa in middle of nowhere and probably they get more stuff then I can

 

[Alexsch]

FET vs BJT

You may use Digikey or Mouser. Use VISA or similar vay of payment. Relative to hobby electronics shops they may end up even cheaper. I am not against BJT as a device, and willingly go for "quasi-bjt" (IGBT) if reason exist. They are very difficult to drive, those BJT's. Thats the real reason. And in order to have fast switching times you need baker-clamps or some very fancy BASE-Drive circuit. And baker-clamps increase conduction losses. On the other hand if you stick to even the old cheap IRF840 with Half-Bridge or Full-Bridge configuration, you may, by clever design do 1-1.5kW SMPS. Provided, you know what are you doing of course . I really don't know your situation. In Israel we can have IRF840 easily, i personally like the 20N50 types from Infineon/IR/ST. Yes, those are 20A 0.22ohm 500V units. (Except i do not value those "8.5A" or "20A" statements. Its all dependent on your heat removal abilities.)