Abstract: A power supply has a transient load and a transformer with a primary side and a secondary side. The secondary side of the transformer includes multiple output voltage terminals. One of the output voltage terminals is coupled to the primary side to form a feedback configuration. The output voltage terminal coupled to the primary side is further coupled to the transient load. When the output voltage terminal outputs a voltage, the transient load consumes power only within a period of time and then stops consuming the power.

Abstract: A heat exchanging device is detachably mounted on a container or a cover. The cover is mounted on the container, thereby forming a closed space between the cover and the container. The heat exchanging device containing a temperature regulating medium is mounted in the closed space between the cover and the container. Thus, the heat exchanging device can be replaced easily and conveniently when being inoperative without having to move the food, thereby facilitating the user using the heat exchanging device, and thereby achieving the sanitary purpose.

Abstract: A heat exchanging device is detachably mounted on a container or a cover. The cover is mounted on the container, thereby forming a closed space between the cover and the container. The heat exchanging device containing a temperature regulating medium is mounted in the closed space between the cover and the container. Thus, the heat exchanging device can be replaced easily and conveniently when being inoperative without having to move the food, thereby facilitating the user using the heat exchanging device, and thereby achieving the sanitary purpose.