Problem with DC/DC Boost converter circuit with MC34063A

I was trying to make a DC/DC boost converter with MC34063A. It is a good IC for the purpose but its not working well.
Having a lots of trouble.

Here is the PCB diagram:


And the circuit diagram is here:



The problems are:

* Its taking high current at startup, frequently MOSFETs blows away.
* If current is reduced from the supply and then controlling the current tuning current controlling VR, it genaretes 30-35V[unstable]. But whenever load is applied, it become short again.
* Genareting lots of heat in Fets and Inductors.

I tried with changing inductors by 47uH,100uH,120uH,220uH. Timing cap: 222,102,104,103. Diodes: UF5408,HER308,SR560. Fets: IRF3205, 75n75, IRFZ44N,

no improvement. All similar problem. :-(

Need help.

it will be a bit better in such type

Thanks man, I'm trying this one now... I'll update what happen....

it will be a bit better in such type

Click to expand...

Hopefully fixing the most obvious design flaws.

It's not so good to divide Vgate down with 100:150 ohm , I think.

Generally, a 20 A switching boost converter should deserve a little bit of a state-of-the-art switch mode controller. Why one of the cheapest available at the market that just barely performs the job?

No upgrade bro... having same problem as before... @ DeepOne


Can you suggest anything good @ FvM ?

possible to do more perfectly but it seems the deal is not in scheme

Thanks DeepOne, I'll try this circuit tomorrow and update the result.

I changed the MOSFET, and inserted IRF740B, now its generating HV(up to 623V I got). But Fet is becoming hot without any load. and with load, voltage drops. And Fets get extremely heated.

"and inserted IRF740B, now its generating HV(up to 623V I got)"

max D_S voltage for this FET is 400V, as we see in datasheet

hmm. That is why after few min it blows away....!!!! I've built another one. It is working well but generating too much heat.