Referring to FIG. 3, when switching from a heavy load to a light load, it can be seen from the figure that the HTL mode is adopted when the output voltage is greater than Vomax. If PID adjustment is adopted, which is as shown in the thick dotted line, the voltage will rise still after the output voltage rises to Vomax, and the dynamic recovery time is also very long. When adopting the HTL mode, the HTL mode is immediately adopted when the output voltage is greater than Vomax. Because the power input of the mode is less than a standby power generally, the output voltage starts dropping immediately and will not rise any longer; before the output voltage drops to a stable value, this is the fast dynamic method; when the output voltage is the same as the stable voltage, the size of the output load can be obtained through the slope, so that the energy of the working mode jumping out of the HTL mode can be close to the power consumption of the load, to eliminate subsequent resonance introduced by unmatched energy, which is as shown in the full line; it be seen that after jumping out of the HTL mode, if the working state starts from the standby state, the input energy thereof is too small, which introduces voltage resonance, as shown in the fine dotted line.