MT3608 Boost Converter Voltage Is Less Than Input Always - Doesn't Work - DIY Fix
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- Опубліковано 1 жов 2024
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Simple algebra: R1 = (Vout/0.6 - 1)*R2 or 41.8k. Since you are probably using E24 (5%) values, the closest value is probably 43k, which will give you an output of 12,3V. HOWEVER: I see the problem, and it's a very dumb one as recommended by the MT3608 chip vendor's circuit diagram for his board. All you had to do was 1) make no changes, then 2) crank the pot "down" (whichever that direction that may be, CW or CCW). Start rotating the trim pot. I can't tell you which direction, or how many turns of the 10-turn pot will be needed, but it could be as many as 6-7 turns. Once you hit this spot, then the boost converter will start doing what a boost converter is supposed to do.
I tried all those types of suggestions before I even considered more drastic measures. NONE WORKED.
@@artbyrobot1 So you turned the pot CW by at least 10 full rotations, and if that didn't work, you tried turning it CCW more than 10 full rotations and that didn't work? I doubt it very much. Do you have a DMM? If so, probe the voltage on the FB pin for each of the 10-rotations cases. Tell me what voltage you measure. If this voltage is larger than 0.6V, as I know it will be, it tells the chip to shut off, which is what you are seeing :Vout = (Vin - Vdiode), which is what these simple boost circuits do when they are shut off. The fact that the circuit springs back to life after your hack (which I do not understand from your description) says that the chip is working perfectly fine. The designer of this demo board (whoever he is) has designed the feedback attenuator (pot + 2.2k resistor) in such a way that it is exceptionally easy to drive FB way above 0.6V, as high as (Vin-Vdiode), which will cause the boost to just sit there doing nothing.
And BTW: as a warning to others, the so-called "specs" chip as well as the Amazon ad for this demo board say that Vin can be as high as 24V. With the demo board as-is, any input voltage over 6V has the potential to fry the chip because the "ABS MAX" (Absolute Maximum) voltage for the FB pin is 6V, which this design will allow. Whoever designed the demo board placed a death wish on the MT3608 chip. No one should apply an input voltage higher than 6V to this demo board. In your case, you are safe powering it with a Li-Ion battery.
I just looked at a few of the comments in one Amazon ad for these boards. This is the topmost comment that backs up my point, to turn the adjustment pot a lot of turns first: "I bought these just needing one to convert an RC radio 4 AA to Lipo 3.7v. I soldered everything up and measured my output. It just had diode drop across it. After some research, I found that you have to turn the adjusting screw at lease 15 times (clockwise) before you can see deflection in voltage. They work great!"
@@demef758 I read comment sections on other videos and forums or w/e and attempted all the fixes recommended. What you are saying is commonly recommended. This is nothing new. IT DID NOT WORK. I tried it all. I had a whole pile of these boards and tried every single recommended fix. NOTHING WORKED.
@@artbyrobot1 DID YOU MEASURE THE VOLTAGE ON THE FB PIN? I design circuits like this for a living. I'm not blowing smoke.