The invention discloses a multi-resonant-cavity LLC
resonant converter, which comprises a primary side switching network, a main
resonant cavity RC1, auxiliary resonant cavities RC2 and RC3, auxiliaryresonant cavity switched-in switched-out switching tubes S5 and S6, a corresponding rectifying circuit FR1 when the main
resonant cavity RC1 works, and a corresponding rectifying circuit FR2 when theauxiliary resonant cavities RC2 and RC3 work. According to the invention, the circuit can be in different working
modes, i.e., a high-
voltage output working mode, a medium-
voltage output working modeand a low-
voltage output working mode, by switching the resonant cavities in which the circuit actually works, and the
gain ranges in the three working
modes are continuous, so that the circuit obtains a wide output
gain; and meanwhile, under the three working
modes, the circuit can achieve the required output
gain in a rated working frequency range by adopting a
frequency conversion control mode, so that
soft switching of the switching tubes in a full output gain range is ensured, relatively large
ring current is avoided, and relatively high working efficiency of the circuit in the full output gain range is ensured.