Years ago I built a 12V in, 5V 3A out power supply using the=20
MC34063 driving an IRF9640 mosfet.
     No buffer circuit used, just a NPN to speed up gate cut off.
     Trying to find the circuit but no luck so far.

     Mark Jordan


On 31-Jan-17 00:48, IVP wrote:
>> NPN/PNP buffer... why do you need it
> I was going after harder gate drive. Looking closelier at the scope
> images I can see it's not the improvement hoped for
>
>> have you tried without it?
> Have now, keeping the 470R p/u for the MC34063 collectors. Vout
> has gone up to 3.27, from 2.29. Iin =3D 309mA, Iout =3D 526mA
>
> Looks like the FET drive is something to think about again
>
>> You said the circuit worked ok with a TIP41
> Yes, a TIP42, Vout did go up to 4.2
>
>> It's not like the NPN/PNP buffer would be inverting or significantly
>> changing the phase is it?
> I'd wondered about that this morning, and how or whether it affects
> the MC34063's duty cycle as it tries to maintain Vout. As Vout has
> gone up and the circuit resembles the d/s it may be that gate polarity
> is an issue. Or maybe it's just a better gate swing. I'll make up a non-
> inverting buffer and see what happens
>
>
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