A DC-DC converter, an on-board charger, and an electric vehicle are disclosed. The DC-DC converter includes: a first adjustment module, a resonance module, a second adjustment module, a current detection module, and a controller. The current detection module is configured to detect a current signal of the resonance module; and the controller is configured to control the first adjustment module and the second adjustment module to reduce an output power when the current signal is greater than a current threshold. By directly detecting the current signal of the resonance module, a high precision and a faster response are achieved.