Hi all,

Some of you know i've been working on this induction heater for quite a while and I got it working working some time ago, yay!

(Video if anyones interested..)

Now, it's been powered from my isolated transformer in the background, that can only supply about 3A, to get around that I was switching the circuit abit above resonance, to bring the current down.. I want to move away from doing that, but before I do, I want to make sure I have the correct heatsinks for my switches and diodes..

That's my circuit as it is right now.

So, im trying to find the power losses in the switches M1,M2 and the diodes D1,D2.

I've googled and googled on how to do this, and I understand 'where' my losses are, but I dont understand the math behind it, let me try explain where im comming from..

Since P = U*I, I have to know the voltage across the FET (Vds) at any given time and multiply with the current going through it, but there is a time component here that I dont understand how to work with, the switching losses are at 10%-90% Vds, so I need to somehow find the losses in the FET when it's switching from 10-90% (and the other way around) and then I think(?) multiply with the switching frequency, to get the power loss in seconds..

Then there's the conduction losses which im thinking would be Rds_on * current^2 * duty cycle*fsw..

The inverter is supplied by rectified mains, about 325Vdc where I am, the inverter has to supply about 13.79A, (lets round that up to 14A) to the RLC circuit, there's 165Vdc in the middle of the FET's, so about 2.28kW total.

Datasheets:

Mosfet: http://ixapps.ixys.com/Datasheet/DS100310B(IXFH-FT-FQ50N60P3).pdf

Diodes: http://www.onsemi.com/pub/Collateral/MUR1520-D.PDF

I hope it's clear what I want to do, if it's not, I apologize, I will be happy to try and clear it up.. I hope you guys can help me out, if any additional information is required I will be happy to try and provide it.

Some of you know i've been working on this induction heater for quite a while and I got it working working some time ago, yay!

(Video if anyones interested..)

Now, it's been powered from my isolated transformer in the background, that can only supply about 3A, to get around that I was switching the circuit abit above resonance, to bring the current down.. I want to move away from doing that, but before I do, I want to make sure I have the correct heatsinks for my switches and diodes..

That's my circuit as it is right now.

So, im trying to find the power losses in the switches M1,M2 and the diodes D1,D2.

I've googled and googled on how to do this, and I understand 'where' my losses are, but I dont understand the math behind it, let me try explain where im comming from..

Since P = U*I, I have to know the voltage across the FET (Vds) at any given time and multiply with the current going through it, but there is a time component here that I dont understand how to work with, the switching losses are at 10%-90% Vds, so I need to somehow find the losses in the FET when it's switching from 10-90% (and the other way around) and then I think(?) multiply with the switching frequency, to get the power loss in seconds..

Then there's the conduction losses which im thinking would be Rds_on * current^2 * duty cycle*fsw..

The inverter is supplied by rectified mains, about 325Vdc where I am, the inverter has to supply about 13.79A, (lets round that up to 14A) to the RLC circuit, there's 165Vdc in the middle of the FET's, so about 2.28kW total.

Datasheets:

Mosfet: http://ixapps.ixys.com/Datasheet/DS100310B(IXFH-FT-FQ50N60P3).pdf

Diodes: http://www.onsemi.com/pub/Collateral/MUR1520-D.PDF

I hope it's clear what I want to do, if it's not, I apologize, I will be happy to try and clear it up.. I hope you guys can help me out, if any additional information is required I will be happy to try and provide it.

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