Abstract: A power conversion apparatus. An additional heat capacity apparatus thereof is connected to a heating body by means of a low-heat-resistance channel, and the heat capacity of the heating body is increased, so that a temperature rise rate of the heating body can be reduced when the temperature of the heating body rapidly rises due to large transient loss, thereby lowering the temperature of the heating body at the end of the short-time peak working condition, and ensuring the reliability of a device. Moreover, a high-performance switch tube or more switch tubes connected in parallel are not required to be used as in the prior art, so that the size and the weight of the system are reduced, and the costs are saved.