Part Number:LM5021
Hello,
This is my first time designing an isolated power supply. I have the following specifications :
Vin : 38 to 57V
Vout : 24V 30W
Here is my schematic and captures of a few signals.
When no load on output (or a few mA), it goes to 24V. But when I put a load, even 100mA, it doesn't start and keep rebooting.
I've tried to simplify the design by strapping (R63, C119), remove (R61, C102, D5) and put 5k at R62 to force Vin (using internal zener for regulation), CSS tested with 10nF (current captures), 100nF, 1uF. Doesn't change a thing !
The LM5021 is working fine. But I really don't understand how it could do more than 100ns MOS ON time... It's obviously a BIG short circuit when the MOS is turned on...
Could you please help me to understand what's going on ?
Thank you for your time !
Michaël
MOS Gate
R86 voltage : Obviously it goes well over 0.5V and explains why the LM5021 stops the MOS conduction. Problem is, I really don't understand how it could be different...
COMP pin
And Vout. We can see that output voltage is rising fast, when the hiccup stops the process.