Fastest simulation method for variable frequency regulator

QSPICE
1

Hi,

I want to simulate a resonant DCDC converter (LLC) which uses frequency modulation as a way to regulate the output voltage.

I have a module in C which calculates the desired switching frequency fsw. Can you propose implementation methods for the variable frequency?

I have seen an approach using the C block where the simulation time variable is used but I wonder whether there’s a lighter implementation, maybe one that does not use the time variable.

TSW = 1 / fsw; //Switching period
t_var = t/TSW - floor(t/TSW); //this is a sawtooth with frequency = fsw
if ((t_var) < 0.5) output = 1
else output = 0;

The if part can be easily substituted by a behavioral voltage source although I don’t know what is lighter for the simulation.

Before, I was using a pulse voltage source and the simulation got more than 10 times slower.

After some optimization the code got as simple as:
product = t * fsw_ref;
VM = product - (int)product;
and this VM is the sawtooth which I compare externally with bv, but still is excessively slow.

Thanks and regards

2

Hi, mosfet.

There are lots of ways to unintentionally make QSpice simulate slowly. You might want to post the *.qsch & *.cpp.

–robert

3

Hi,

I think there might have been something else in the simulation, which I inadvertently solved.

Anyway, for generating a variable frequency squarewave the logic that worked best for me was:

product = t * fsw_ref;
VM = product - (int)product;

and the generated sawtooth is compared against a fixed threhsold, 0.5 for me for a 50% duty cycle, with a bv element.

Regards