I am using LT8316 as a controller for a 600V to 12V buck converter in my system.
Basically I am just copying the design of DC2781 including the schematics and components selection, and just modify the layout according to my application.
My schematics and layout are shown below.
However, when I give input voltage (I use 25 V for initial test), there is no output voltage. But when I turn-off the input source, there will be a pulse of 12V last for a short moment.
And it is the same case for the gate signal of the MOSFET, when power on, no signal; at the instant of turning-off, Vgs appear for a short time period.
I feel like the circuit is only enabled when input has a falling edge somewhat, so the remained energy in input cap is released through the converter.
I tried the same input voltage 25V and same load 0.5W with the commercial demo board DC2781A, and everything works well.
So may I ask what can go wrong with my design, is there any suggestions?
I really appreciate your time and help.