Plecto
Full Member level 5
Hi. I'm using a LTC3780EG Buck-Boost regulator as a part of a MCU-controlled battery charging circuit. The circuit is apparently working fine with a steady output voltage, but it's efficiency is only around 75% and the duty cycle to the fets is swinging between 36 and 46% with a frequency of about 20khz. Right now I'm testing with an input voltage of 9V, output voltage of 13V and a resistive load of 33.3Ohm. The gate signal on Q1 does not look healthy either (image below). The components are on a 6-layer board with a solid ground plane. The controller along with all passive components are very close together on one side, with inductor and fets on the other. All traces are very short. What is causing this type of oscillation and what can I do?
Vg of Q40:
Vg of Q1:
Schematic:
Vg of Q40:
Vg of Q1:
Schematic: