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STD TPS61022 Boost Converter
License: Public Domain
Mode: Editors' pick
This project is a boost converter for single cell li-ion input to 5V 3A output.
Following test showing the ripple voltage is under +-20mV with 3V input to 5V/2A output.
What's special about this project is that it comes with some protection for the internal MOSFET of TPS61022. Why? Because I have some destroied TPS61022 that have the lower-side MOSFET shorted. This happens even if I followed the reference layout in the datasheet. And I've found that others have encountered the silimar issue.
TPS61022: Self Destructing
[FAQ] TPS61022: How to avoid TPS61022 working abnormally or IC failure?
I have the same issue when I connect the input of the boost converter to the bench power supply with the output current limit not sufficient to the required output load of the boost converter. After I encounter this issue, I found this paragraph in the datasheet:
I suspect that when the input is unstable enoung(Bench power supply fast switching between CC/CV mode), the IC operation might not able to turn-on high-side MOSFET correctly. While under heavy load, the inductor current might cause voltage spike on the drain of lower-side MOSFET. That leads to destroied lower-side MOSFET. (Just a guess, please correct me if I'm wrong)
In this design, I've added two protection.
First, add a schottky diode between SW pin and VOUT pin of the TPS61022 IC. So that in the case that the upper-side MOSFET can not turn-on in-time, the diode would provide a alternative path for the energy to go to the load. Effectly clamp down the voltage of the drain on the lower-side MOSFET. Since the interagted high-side have low Rds-on resistance (18mOhm), in normal operation there won't be enough voltage difference between SW-VOUT for the current to pass though the schotty diode. So that it won't effect the efficiency on normal operation.
Second, I'm using (abusing) the well-known single-cell battery protection IC (DW01 or FS312F-G) to be an UVLO detection IC. Since the TPS61022 EN pin does not have integrated voltage compartor or hysteresis function, and it'll need lots of components(Vref,Compartor,Resisters,MOSFETs) to build such logic manually. By using bettery protection IC, we can simply take the Over-Discharch MOSFET drive output to be used as NOT-UVLO indicator, and feed it into the TPS61022's EN pin. Hopefully that it'll provide extra protection when the input voltage is unstable. The down-side is that we'll loss the 0.5V input operation feature of this boost IC. I've leave a place for connecting EN pin directly to VIN with a 0ohm resister if the UVLO design is not desired.
After these two protection, I've tested with bench power supply tuning down the current limit case. Seeing that the bench power supply switing between CC/CV mode. But the IC stays alive with this design.
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