Safety control circuit for electric water heater

A safety control circuit for an electric water heater, said electric water heater comprising an electric heating element that is connected to an alternating current source via a switch;

• said safety control circuit comprising:
• a voltage detection circuit for detecting a voltage value of a voltage applied to said electric water heater;
• a current detection circuit for detecting a current value of a current supplied to said electric water heater;
• a load-resistance calculation unit for calculating a load-resistance reference value of said electric water heater based on said voltage value and said current value detected by said voltage detection circuit and said current detection circuit, respectively;
• and said load-resistance calculation unit keeping detection of load voltage value and current value of said electric water heater through said voltage detection circuit and said current detection circuit when said electric water heater is continuously supplied with power, and calculating dynamic load-resistance values of said electric water heater;
• and
• a central processing unit for determining whether there is water supplied to said electric water heater based on said load-resistance reference value and said dynamic load-resistance values of said electric water heater supplied by said load-resistance calculation unit;
• and said central processing unit driving said switch to turn off and thereby cut off power supply to said electric water heater when a difference between said load-resistance reference value and said dynamic load-resistance values being larger than a predefined value.