FIG. 6 is a comparison between the working state fixed with full load and the working state determined by the slope Kup to the flyback circuit in FIG. 4 when jumping out of the LTH mode; and this is the embodiment of the present invention. It can be seen that when the load is switched from 700Ω to 7Ω, when the system output reaches 5V and jumps out of the LTH mode, adjustment is started in FIG. 6a by using the working state under full load; at this moment, the power input is greater than the load consumption, and the output voltage will rise, which introduces voltage oscillation; in FIG. 6b, when jumping out of the LTH mode, Kup is 6, and the corresponding load is around 7Ω; at this moment, the working state starts from 350 Ts/clk (57 kHz) and the primary peak current of 0.286 A of the PFM mode, which will not introduce voltage oscillation; at this moment, it can be deemed that the output voltage is already stable, the subsequent resonance voltage is eliminated, and the recovery time of the dynamic process is decreased.
