The present invention discloses a resonance circuit for use in an H-bridge DC-DC converter, the resonance circuit comprising: an H-bridge converter, capable of converting unstable DC power into stable DC power; a first resonance circuit, disposed on a buck side of the H-bridge converter for reducing the turn-off loss of a first active switching element; and a second resonance circuit, disposed on a boost side of the H-bridge converter for reducing the turn-on loss of a second active switching element. The H-bridge converter comprises: a first active switching element and a second active switching element; a coupled inductor with dual windings capable of storing energy; and a first passive switching element and a second passive switching element. The first resonance circuit comprises: a first inductor, a second inductor, a first auxiliary inductor, a first passive switching element, a second passive switching element and a first auxiliary capacitor, wherein the second inductor comprises a primary winding and an auxiliary winding. The second resonance circuit comprises: a second auxiliary inductor, a third active switching element, a first auxiliary inductor, a first passive switching element, a fourth passive switching element, a third capacitor, a fourth capacitor and a second auxiliary capacitor.