The dynamic control module comprises a voltage monitoring module and a slope calculation module. The voltage monitoring module determines whether to adopt the dynamic mode according to the sampling result Vo. The so-called dynamic mode refers to that when the voltage of a load changes greatly, and a maximum voltage Vomax and a minimum voltage Vomin are set here, when Vo is greater than Vomax or Vo is less than Vomin, it is deemed that the voltage changes greatly, and it is necessary to make the output voltage be restored to a stable voltage rapidly by inputting large power or small power; and when the output voltage is less than the minimum voltage Vomin, a constant-frequency light-to-heavy load mode (LTH) in the dynamic mode is introduced to enable the output to be rapidly raised to the reference voltage Vref by inputting large power and then jump out of the mode; when the output voltage is greater than the maximum voltage Vomax, a constant-frequency heavy-to-light load mode (HTL) in the dynamic mode is introduced to enable the output to be rapidly dropped to the reference voltage Vref by inputting small power and then jump out of the mode; on the contrary, if the output voltage changes suddenly, but does not change greatly, the dynamic mode is not needed, and loop control is realized through normal PI control method and mode control, which is called normal working mode. A mode result (mode_F) outputted by the voltage monitoring module is inputted to the mode control module and the slope calculation module, if the voltage monitoring module determines that the system enters the dynamic mode, and if the system enters the normal working mode, output latch of the slope calculation module is controlled to be unchanged. The slope calculation module calculates the rising slope of Vo when the voltage monitoring module outputs the LTH mode, and calculates the descending slope of Vo when the voltage monitoring module outputs the HTL mode; when the normal working mode is adopted, the slope is not calculated, and the output keeps unchanged. The result Kslope of the slope calculation module is inputted to the mode control module.