Multi-running-mode fresh air fan and control method of multi-running-mode fresh air fan

The invention relates to a multi-running-mode fresh air fan and a control method of the multi-running-mode fresh air fan. The multi-running-mode fresh air fan comprises a machine case provided with a filtering mechanism, a sensing mechanism, a draught fan and a sterilization mechanism. The sensing mechanism is connected with a control mechanism. An indoor air inlet pipe is arranged at the bottom of the machine case, an outdoor air inlet pipe is arranged at the position, on one side of the indoor air inlet pipe, of the lateral portion of the machine case, a half ball valve connected with a stepping motor is arranged between the indoor air inlet pipe and the outdoor air inlet pipe, and the stepping motor is connected with the control mechanism. The filtering mechanism, the draught fan and the sterilization mechanism are sequentially arranged above the indoor air inlet pipe and the outdoor air inlet pipe. An air outlet is formed in the upper portion of the machine case. According to the multi-running-mode fresh