Buck bootstrap using behavioral voltage source control and Constant-OnTime-CLK

[dmbeliun]

Hello,
I’m trying to build a simple constant on-time (COT) control for a buck converter.

When i use normal pulse source(pulse 0 5 100n 1n 1n 100n 1000n) everything seems to work as intended and i get my conversion ~1/10.

I’ve encountered a problem when I feed the Constant-OnTime-CLK output as behavioral Voltage source control input. It seems that the MOSFET is not controlled at all and is always open. Even through the Vg-Vsw is controlled in the same way as in pulse source.

The only difference, that I could find is that the Constant-OnTime-CLK output gets high at the start-up, even though CLK and OnTime inputs are enabled only after 100-110nS.

After the startup graph is fully similar to the pulse generator, in my understanding it still should control the MOSFET correctly.
Buck.qsch (11.8 KB)

[KSKelvin]

Let me review what I can do with this custom symbol. As a short-term solution, use this to ensure a 0V gate at t=0s (i.e., a DC operating point solution where the MOSFET is OFF).

[KSKelvin]

I upload the custom symbol (force initial condition of Q to Vlow), you can download latest version from
https://github.com/KSKelvin-Github/

Qspice/Symbols-KSKelvin/power electronics/gate controllers
/Gating-OnTime-ExtCLK.qsym

Here is verification with your simulation setup.
Buck-KSK.qsch (12.1 KB)