LNK306 Buck Converter Design Help Needed
I've designed a buck converter with the LNK306 and am having some trouble with it. I used the PIXls Designer 8 software, the LNK306 datasheet, and Application Note AN-37 to help in the design.
My input is 115VAC, 400Hz, and my output is 28VDC, 250mA max. All I'm seeing right now is short blips on the output voltage, with the drain voltage seeing the correct DC voltage level (~162VDC). I have a 114ohm resistive load attached as well to mimic my real load.
I'm assuming the short blips I'm seeing are because the chip can't get out of auto-restart. I've tried multiple values of soft-start capacitors as recommended because of the higher output voltage. I'm not sure what else to try since the rest of the parts are as recommended in the sources I've read.
My PIXls Designer 8 file is attached. Any help would be appreciated.
Thanks,
Amanda
Comments
I've checked my circuit for these conditions, and don't see anything. I also decreased the load on the output with no change.
I've attached an oscilloscope plot of what I'm seeing and my schematic.
Channel 1 - Input voltage to the drain of the chip
Channel 2 - Current at the AC input to the circuit
Channel 3 - Output voltage of the circuit/Voltage across the load
Amanda
Can I get some feedback on this? (see above)
There are 3 reasons why this device can enter auto-restart
1) output is shorted
2) Feedback path is open (Cold solder joints, backward diode connection, incoprrect resistor values)
3) Too much output power.
For (3) try to see what happens at lighter load,