Shown on this slide is an example of applying an abnormal, steady overvoltage to a power line of devices. The left side shows a case where a steady overvoltage comes into a power line that uses a middle power diode of 1 W or 2 W for protection. An overvoltage is clamped at the zener voltage of the Zener diode, a steady large current flowing into the diode. After a while, a fuse located at the entry of a power line will melt to protect the load from overvoltage, and the device will be stopped safely. The right side shows a case where a steady overvoltage comes into a power line that uses a middle power diode of 200 mW for protection. The overvoltage is clamped at the zener voltage of the Zener diode, a steady large current flowing into the diode. After a while, the Zener diode will be damaged due to a large current, resulting in applying an overvoltage to the load. In this case, the device will be in unsafe state and might be damaged or occasionally smoke or ignite. For steady overvoltage, a middle-class Zener diode of 1 W or 2 W is required because the voltage has extremely high electric energy.