I did some boost and buck circuit thingies with PICs a long time ago. These days there isn't much compelling reason to make your own DC-DC gizmo. Just get a suitable DC-DC board, boost boards in your current rating target range often have a 2-24V Vin, these are MT3608 or its clones. (But if you are really running at the 10W target, then get a 3A or better one, who knows if your board is a knockoff that can't handle 10W?)
Getting 5V/2A from a 1.2V AA (NiMH I assume) means that unless you have good components, going 4X boost at high currents is going to be quite inefficient. Especially the transistor -- that MT3608 has a 80mOhm FET versus maybe 0.4V across the transistor if well driven and the chip will beat your circuit anytime. Then your inductor has to be sized correctly, the saturation current has to be higher than the peak current (or there will be distortions like spikes >>5V etc that might kill the Pico), and that would be >8A, so more like 10A... okay, it's not going to be practical getting 10W from a 1.2V NiMH anyway, the Vbatt will be depressed (or dive down if it's a cheap NiMH) and your boost circuit will be forced to work harder, you will get a lot less capacity trying to drain the NiMH at 7C or more -- it will escalate quickly. Too many inefficiencies, so the project should be regarded more as a learning experience.
I do think playing with boost circuits is fun![:D]( "Very Happy")
, but try a low power target first. Once you look at high power options, usually it is far better to buy a DC-DC board.
Getting 5V/2A from a 1.2V AA (NiMH I assume) means that unless you have good components, going 4X boost at high currents is going to be quite inefficient. Especially the transistor -- that MT3608 has a 80mOhm FET versus maybe 0.4V across the transistor if well driven and the chip will beat your circuit anytime. Then your inductor has to be sized correctly, the saturation current has to be higher than the peak current (or there will be distortions like spikes >>5V etc that might kill the Pico), and that would be >8A, so more like 10A... okay, it's not going to be practical getting 10W from a 1.2V NiMH anyway, the Vbatt will be depressed (or dive down if it's a cheap NiMH) and your boost circuit will be forced to work harder, you will get a lot less capacity trying to drain the NiMH at 7C or more -- it will escalate quickly. Too many inefficiencies, so the project should be regarded more as a learning experience.
I do think playing with boost circuits is fun
, but try a low power target first. Once you look at high power options, usually it is far better to buy a DC-DC board.Statistics: Posted by katak255 — Tue Jan 21, 2025 2:00 am