Could anyone please tell me where I am going wrong with this boost converter?

Question

I want to implement a boost converter using a MC34063A. I have made the circuit as it is mentioned for step-up operation in the MC34063A datasheet. The datasheet says it can take up to 40V input. But I can see that the IC is getting burnt as soon as my input voltage exceeds 12V. What could be the reason? Here is a schematic of the circuit I'm using:

A 170uH was not available, that's why I used 100uH instead. Instead of a 0.22 ohm resistor I used 0.5 ohm by paralleling two 1 ohm resistors. Due to the unavailability of a 1500pF capacitor I used 1000pF.

The Schottky diode 1N5819 was not available in Proteus, that's why I have drawn the circuit with a 1N4148, but I am actually using a 1N5819 as suggested in the datasheet. Are these differences affecting the performance of the circuit?

However,after reading a comment,below I have given the circuit using the original model or MC34063 in proteus.

Answer 1

I'm going to necro this thread, because I had a similar problem and it may be useful to anyone googling it.

My application did not have any current limiting hardware; this one should. But the possibility exists that the series inductor value is lower than expected, which would allow an unusual amount of current through the onboard switch.

To find out, you could use external switching transistors that can handle it, in a cascode configuration. Or, a gate driver IC and a Mosfet.

If the controller IC still burns out after that, you may have a bad batch of controllers. This happened to me recently, where the ICs I had ordered had been damaged at the warehouse.

Answer 2

That looks like no MC34063 that I know of. Your circuit diagram shows two opamps. The MC34063 has a drive transistor, an input comparator, and a timing circuit.

The built-in switch in the 34063 supports at most 1.5A of current, and will be pretty hot when running that much, btw.

Finally, your 'pin 8' at the top of the schematic doesn't even have a label. Where does that go? Who knows?

Draw a real schematic with the actual circuitry of the 34063, and you may get better help. At a minimum, a square with labels for the various pins (rather than just pin numbers) would be a good start.