I am designing a small switch mode power supply using the TPS63060DSCT, based on the data sheet I will require a 1.5uH inductor. I have be told that the Q-factor must be considered in the inductor (and capacitor) selection. Is it the case where the higher the Q-factor the better? and what would be the minimum q-factor for this design?
*assuming the chosen indicator also meets Current requirements.
Electronic – Inductor Q-factor for switch mode
inductorswitch-mode-power-supply
Best Answer
The higher the inductor Q the better. However, there's no need to strive for very expensive values, 'good enough' is good enough.
Consider the Q limitation as a small resistor in series with the inductor. This will obviously cause losses, and the losses will be larger for low Q, that is big R. You will also have losses in the switches within the IC. Once your Q losses are lower than the IC losses, the efficiency of the overall system cannot be improved much, even with a perfect inductor. It would take a very poor Q indeed to stop the converter working.
Your TPS63060 data sheet should have enough information in it to estimate losses for your operating conditions, a reasonable estimate is good enough, there's no need for calculation to many decimal places. Once you have losses for switch and inductor, you then have a commercial decision. Do you use a cheap inductor with 50% of the total system loss, or an expensive one with only 10% of the system loss?