i made a 280W adjustable output LLC desing referencing RDR189.
The problem is the resistor R42 (10R) which is connected to VCCHB pin, burns in some circuits. Sometimes D8 also burns. What may be the reason?
i used 5000pF input capacitance LLC Mosfets so changed 10R (R56. R58 )driver resistor to 1R and Fmax resistor to R52=19K in order to adjust sufficient dead time. R53=19K and R51=22K in my design.
When R42 burns once, the LLC side never works again and shuts down even i changed R42 and also D8 with new one. i control all the components, they seems to be ok. i also see the LLC GATEH and GATEL signals on scope under test conditions ( power up PLC with external 12VDC and power 2.2V to FBP ( pin23). But when apply AC power it burns again.
1R MOSFET driver resistor may be the reason? isn't it enough for clamp for negative voltage spike? Because i know these resistors and D17 D18 diodes works for clamping the amplitude of the negative gate-source voltage.
What is your opinion about it? What is possible solution. What other components may be blow out?
Thanks for your help.