My circuit above as I checked also has around 150mA-160mA peak on start up. I had a current drop right after Rsc at around 8mA on Rd resistor.
Do you suspect that this could be a cycling issue within the IC because of the voltage drop on the output load? Perhaps the current I want is too low for it to properly load the inductor.
Nokia used this IC in their products but I'll assume they had higher currents for step-up and step-down with their products which made it suitable for their applications.
What boost converter do you recommend but not too expensive? Maybe a successor to the mc34063.
Hi,
Theoretically i think this should work, but yes there are practical aspects that come into play. The BH curve for inductors is like a stretched out lazy S, so yes the inductance can do down with extremely low current. It would be hard to believe here though with such a low current inductor and the current is not the same as the load current it can be higher when operating with some max and min.
What do you mean by "current drop"?
Try to describe the problem as well as you can.
It's not unusual for a new design to have a problem but usually there is a solution and the solution is found by making measurements and comparing those measurements to theory. I have the theory but you have to supply the measurements.
We could look for a spice model and do a few closer to real life simulations. I thought i tried this a few years back but ended up making my own model anyway. I'll see if i can dig it up.
LATER
Ok dug it up, tried it out, but first i had to modify it because i had it set up for buck. Now that it is boosting, i have trouble getting it to fail with anything but an input voltage that is too low.
This tells me that there is a chance that the battery and wiring can not deliver the current when needed, so the dynamics of the input supply cant meet the dynamics of the boost circuit. To possibly help this situation, you could try an electrolytic cap in parallel with the battery, right at the PC board. This may allow for a higher peak current reserve which could get it working. So measuring the input voltage with or without load with a DC volt meter is not good enough if it does show normal voltage but the circuit still doest work, it would have to be a scope, or just tack a 10uf cap in parallel.
This is just one thing to try though.