Patent ID: 7505237

Claim:
A safety electrical outlet for preventing hazardous conditions at the outlet by preventing the delivery of AC power to the receptacle of the outlet when no load is attached to the receptacle or when a short circuit is attached to the receptacle, comprising: a plug receptacle configured to receive a plug of an appliance; an AC line input electrically connected to an AC power source; an AC to DC converter directly connected to the AC line input and outputting a low-voltage DC voltage; a low-voltage load detection circuit powered by the DC voltage and measuring an impedance of a load connected to the receptacle of the outlet at a time when no AC power is being supplied to the receptacle, the low-voltage load detection circuit providing a power-on switching signal comprising: a signal of no delivery of the AC power to the receptacle when the impedance of the load at the receptacle is higher than an upper reference impedance; a signal of no delivery of the AC power to the receptacle when the impedance of the load at the receptacle is lower than a lower reference impedance; and a signal of delivery of the AC power to the receptacle when the impedance of the load at the receptacle is higher than the lower reference impedance and lower than the higher reference impedance; a load current detection circuit measuring an AC current passing to the receptacle when AC power is being supplied to the receptacle, the load current detection circuit providing a power-off switching signal comprising: a signal of delivery of the AC power to the receptacle as long as the measured AC current exceeds a minimum reference current; and a signal of no delivery of the AC power to the receptacle when the measured AC current drops below the minimum reference current; and a switching circuit receiving the power-on switching signal from the low-voltage load detection circuit and the power-off switching signal from the load current detection circuit and driving a relay electrically connecting the receptacle to alternatively (i) the low-voltage load detection circuit and (ii) the AC line input, the switching circuit driving the relay circuit to: electrically disconnect the low-voltage load detection circuit from the receptacle and electrically connect the AC line input to the receptacle when the signal of delivery is received from the low-voltage load detection circuit; and electrically disconnect the AC line input from the receptacle and electrically connect the low-voltage load detection circuit to the receptacle when the signal of no delivery is received from the load current detection circuit.