A multifunction power conversion device for dynamical detection includes an input filter unit, a transformer, a switching transistor, a driving controller, a feedback unit and an output unit. Two sensing signals from the primary and auxiliary coils of the transformer form a current sensing zero detection signal. The digital control unit of the driving controller determines if a current flowing through a secondary coil of the transformer is reduced to zero due to discharging, and further finds valley of the current of the secondary coil. The switching transistor is turned on after a preset number of the valley and then turned off by a process of current sense. Therefore, the present invention greatly reduces switching loss, increases efficiency of power conversion, and particular, enhances flexibility of application to meet actual requirements by simply updating program executed by the digital control unit.