In resonant inverters (and converters too) power flow can be controlled by the switch
network either by changing the frequency of the square wave voltage, or its duty cycle, or
both, or by special control schemes such as phase-shift control. In this context we will focus
on power flow control by frequency modulation, that is, by changing the frequency of the
square wave closer to or further from the tank circuit's resonant frequency while keeping its
duty cycle fixed.

Simplified Analysis and Design of Series resonant LLC Half-bridge Converters