LLC converter calculator
Screen an LLC operating point before detailed simulation.
An LLC converter uses the resonant tank to shape current and enable soft switching over a useful operating range. Device loss depends on tank current, switching frequency, magnetizing current, dead time, and whether ZVS is actually maintained.
Resonant starting point
fr = 1 / (2π√(LrCr))
Zr = √(Lr/Cr)
Ln = Lm/Lr
These quantities describe the tank but do not by themselves guarantee the required gain range. Turns ratio, load quality factor, input range, output range, and the permitted switching-frequency span must be considered together.
ZVS is an operating condition
Primary MOSFET ZVS requires enough inductive current during dead time to charge and discharge the bridge-node capacitances. Light load, excessive magnetizing inductance, insufficient dead time, or nonlinear Coss energy can remove the margin.