Power plug with leakage current protection function

A power plug comprising:

• neutral and phase conductor prongs;
• output neutral and phase wires;
• a changeover mechanism for making or breaking electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires;
• a shield line disposed around the output neutral and phase wires;
• and
• a leakage current and short circuit detection circuit electrically connected to the shield line and the changeover mechanism for generating a signal to cause the changeover mechanism to break the electrical connections between the neutral and phase conductor prongs and the output neutral and phase wires in response to detecting a leakage current or a short circuit condition on the shield line,
• wherein the leakage current and short circuit detection circuit includes a photo coupler IC and a silicon-controlled rectifier (SCR), an input of the photo coupler IC being electrically connected to the shield line and an output of the photo coupler IC being electrically connected to a gate of the SCR to control conductivity of the SCR, the SCR supplying a current to the changeover mechanism when the SCR is conductive.

A power supply device comprising:

• input neutral and phase conductors;
• output neutral and phase conductors;
• a changeover mechanism for making or breaking electrical connections between the input neutral and phase conductors and the output neutral and phase conductors;
• a shield line for sensing an abnormal condition;
• and
• a leakage current and short circuit detection circuit electrically connected to the shield line and the changeover mechanism for generating a signal to cause the changeover mechanism to break the electrical connections between the input neutral and phase conductors and the output neutral and phase conductors in response to detecting an abnormal condition on the shield line,
• wherein the leakage current and short circuit detection circuit includes a photo coupler IC and a silicon-controlled rectifier (SCR), an input of the photo coupler IC being electrically connected to the shield line and an output of the photo coupler IC being electrically connected to a gate of the SCR to control conductivity of the SCR, the SCR supplying a current to the changeover mechanism when the SCR is conductive.