The invention discloses a drive circuit for controlling electric energy of a light source, a method and a system. The drive circuit comprises a power convertor which is respectively connected with a power supply and a light source and a dimming controller connected with the power convertor; the power convertor receives the electric energy from the power supply and supplies an electric energy after adjustment for the light source; the power convertor includes a control switch in serial connection with the light source; the dimming controller monitors the power switch between the power supply and the drive circuit and receives the dimming request signal and the dimming stop signal; the dimming request signal indicates the first group of actions of the power switch and the dimming stop signal indicates the second group of actions of the power switch. If receiving the dimming request signal, the dimming controller controls the control switch to continuously adjust the electric energy which is output from the power convertor after adjustment; and if receiving the dimming stop signal, the dimming controller stops the electric energy which is output from the power convertor after adjustment.