A driving circuit comprises a transformer, a first capacitor and a first controller. The transformer includes a primary winding and a secondary winding. The secondary winding is located in a secondary side and configured to generate a power. The first capacitor is connected in series to the primary winding, wherein the first capacitor and the transformer are configured to form a resonance unit. The first controller is configured to obtain a feedback current from the secondary side, and change a working frequency of the resonance unit based on the feedback current so as to change the power.
