Resonance circuit, charging control method and charger

The embodiment of the invention provides a resonance circuit, a charging control method and a charger. The circuit comprises a DC-DC primary side module and a DC-DC secondary side module. The DC-DC secondary side module comprises a first secondary side oscillation sub-module, a second secondary side oscillation sub-module and a second change-over switch sub-module; under the condition that the second change-over switch sub-module is switched on, the first secondary side oscillation sub-module and the second secondary side oscillation sub-module are in an enabled state, and the resonance circuit works in a PFM mode; and under the condition that the second change-over switch sub-module is disconnected, the second secondary side oscillation sub-module is in an enabled state, and the resonance circuit works in a PWM (Pulse-Width Modulation) mode. The second change-over switch sub-module is used for controlling the enabling of the first side oscillation sub-module, so that the switching of the resonance circuit be