The inputs of the PID module are an error signal outputted by the error calculation module, the control signal PI_ctrl outputted by the mode control module and the V_PI0 assigned. In the dynamic mode, when the PID module is switched off by the control of PI_ctrl, the dynamic mode is switched to the first switch period of the normal working mode, an initial value V_PI0 is assigned to the calculation of the PID module firstly, then PID calculation is conducted, the supplementary calculation result V_PI is inputted to the mode control module and the PWM module, then PID calculation is conducted to each period of the normal working mode, and the supplementary result V_PI is inputted to the mode control module and the PWM module.

The PWM module selects whether to accept the switch period Ts_LTH or Ts_HTL and the duty ratio DLTH or DHTL (or current) information of the dynamic mode according to the control signal PI_ctrl outputted by the mode control module, or calculates to obtain the switch period and the duty ratio information during normal control through the supplementary result of the PID module or the mode signal mode_ctrl of the normal working mode given by the mode control module; after the period and the duty ratio (or peak current) information are obtained, the duty ratio waveform is outputted through a driving circuit to realize the loop control, so that the dynamic response of the switch power is improved through the dynamic control module when the load changes greatly; and then the output voltage of the switch power is sampled again, and the process above is repeated to conduct cycle control to switch on and off the power valve of the switch power, so as to make the system be more stable, thus obtaining higher dynamic response.