Hello, I have made a power supply using LM3150, it is a redesign of an existing unit that works fine.
The problem with the new design is that it seems that the output current is severely limited, the design was made for 7V and 8A and the limit of the unit is actually around 1A.
I have used Webench with the parameters below (the nominal input voltage is actually 12V. The only changes compared to the Webench BOM were:
- the inductor - I have used IHLP6767GZER100M01 instead of the XAL1010-103MEB (that was the initial choice in Webench) - but the IHLP6767GZER100M01 was also recommended as alternative by Webenc
- the output capacitor is 180uF instead of 120uF (16SVP180M) - but it is the same series and with similar ESR
The output looks clean at 7V for a low current but if I test it with a simple power resistor to get a mere 1.25A output current the voltage drops severely and the output looks like a sawtooth between 0V and 7V with a frequency around 200Hz. If I use two resitors (2.5A) the frequency gets to 400Hz.
I am assuming the chip goes into current limit protection ?
The old unit was designed for 5.5V output at 10A and it worked fine, but it used other MOSFETS and inductor and the values of the components were slightly different.
I would be grateful for any help to get this solved, I have checked the components and values and assembly and it all seems OK. And as mentioned the previous version is running OK.
Thanks,
Mihai