The charging and discharging speed of the capacitor determines the speed of turning on and off the MOS tube. Vgs first charges Cgs, and with the rise of Vgs, the MOS tube enters the variable resistance region from the cut-off region. After entering the variable resistance region, the Ids current increases, but the Vds voltage does not change. With the continuous increase of Vgs, the MOS tube enters the Miller platform area. In the Miller platform area, Vgs remains unchanged, the charge is charged to Cgd, the Ids remains unchanged, and the Vds continues to decrease. In the later stage of the Miller platform, the Vds of the MOS tube is very small, and the MOS enters a saturated conduction period. In order to ensure that the transition between the states of the MOS tube is linear and predictable, the external capacitor C2 is connected in parallel with Cgd. If the external capacitor C2 is much larger than the internal gate-drain capacitance Cgd of the MOS tube, it will reduce the internal nonlinear gate-drain capacitance of the MOS tube. The role of Cgd in the transition between states can also achieve the purpose of increasing the Miller plateau time and slowing down the speed of voltage drop. The external capacitor C2 is used as an integrator to precisely control the switching characteristics of the MOS tube. The inrush current can be precisely controlled by controlling the drain voltage linearity.