[REQUEST]Isolated Power Supply for IGBT gate grivers

[zab]

     IGBT and Mosfet are used extensively in modern power supply converters.Different technique are used to drive them from gate drive transformers,optocoupler circuits having boost straps.and other drivers with separate supply of each one .My problem is this that I intent to use driver having separate power supply for each driver instead of bootstrap drivers like ir2110.
The simplest choice is 50 Hz transformer having separate loops for each supply. the problem with this is huge size and poor regulation.Then comes smps converters here the issue is availability of the components.and design.I saw many circuits of different capacity for this.

In ac motor drives three methods are used.

 1 A ferrite core transformer having four loops 1 for low side transistors and 3 for each high side transistors.
 2 Six ferrite core transformer are used for each driver but all are driven with single smps ic.
 3 Bootstrap drivers are used having single supply.

I want help in deciding which one should I select for best, considering high isolation, low cost, long life,durability and easy to maintain.
Please share your experience and knowledge.
An example may seen at http://scholar.lib.vt.edu/theses/available/etd-05172010-174530/unrestricted/Tan_Z_T_2010.pdf


 

[sam_des]

Hi,

I have successfully used options 1 & 3 quite a few times. Never used option 2, simply because of labor costs involved - getting 6 transformers is quite expensive compared to single one, even if it is more complex.

Regarding 1, I normally use single SMPS controller, single ferrite transformer with multiple secondaries. Only drawback is only 1 of the outputs are tightly regulated while others follow it.  Usually this is not an issue. If more tight regulation is required on these secondary outputs, you can simply add a linear regulator. Adjusting original output will reduce the dropout and dissipation in regulator.

Isolation and reliability is completely dependent on your ferrite transformer. Never had any issue once you get that right.

I don't know your power requirements, but have a look at SMPS controllers like Power Integrations(PI). They have everything inside one package, Power FET, Line Under/Overvoltage, Output Short detect, OverTemp detect. External components are few, a opto and TL431. Although Rdson of PI devices is high, Result is quite compact. Again ferrite transformer is the thing to work on. They also have designer software freely available.
There are other manufacturers like PI, but not as easily available and variety.

Hope this helps,
sam_des

[zab]

  Option 2 is used to better isolation for igbts used on higher voltages .It has less failure rate. Secondly damage is reduced to minimum when igbts are get damaged. For regulation the  input is regulated and a fixed duty cycle is provided.as all circuits are identical so is their voltages.

In option 1 when 4 loops run parallel high voltages have more chance of jump over with the passage of time.

My requirement is 2A per loop having +15V and -5V for each.I want drive 300A IGBT module

I am thinking of using uc 38xx for oscillation having variable frequency wide range of voltages .Looking for some practical example of circuit,and components placement as well.
I am still in dilemma what to go for.     

[Gallymimu]

we usually do #2 but it does cost a bit.

[zab]

we usually do #2 but it does cost a bit.

This is what I am presently working on too.Studing it Planing it how to make it easy and reliable .
Any detail of what you do how and why particularly this if possible.

[Tech_n]

We always preferred to use transformers for gate driving, because high side drivers were expensive or not obtainable at that time.
Using option 2 gives the best insulation, but for normal needs one drive transformer with good insulated secondaries is more than sufficient.
From the question i am now not exactly sure if you need only to drive the gates, or if you want to have isolated power and use gate driver circuits. This is also possible, but using a gate drive transformer is easier and needs no extra power circuit.

[zab]

@Tech_n
Can you share the details of the transformer drive circuitry if possible.
What I want is to drive IGBT having high current. The problem is what I learned that transformer does not support variable duty cycle and variable frequency. So the best option known to me is optocoupler with isolated supply.Optocoupler has fault protection circuitry as well. Negative voltages are applied to gate in OFF state to protect it from false triggering. Please share your information and experience about it.