Patent ID: 8247991

Claim:
A lighting delay circuit, comprising: a switch comprising a first terminal to be coupled to a hot lead of an alternating current (AC) power and a second terminal; a light; a commutating circuit comprising a first terminal connected to the second terminal of the switch via the light, a second terminal to be coupled to a neutral lead of the AC power, a third terminal, and a fourth terminal; a relay comprising a single-pole double-throw (SPDT) switch and a coil, the SPDT switch comprising a first contact coupled to the third terminal of the commutating circuit, a second contact, and a third contact connected to the fourth terminal of the commutating circuit through a first resistor and the coil in series, wherein the first contact is connected to the third contact in the presence of a current flowing through the coil, the first contact is connected to the second contact when there is no current flowing through the coil; a switching element comprising an anode connected to the second contact of the SPDT switch, a cathode connected to the fourth terminal of the commutating circuit, and a gate, wherein the switching element turns the light on when the first contact is connected to the second contact of the SPDT switch of the relay; a negative temperature coefficient thermistor comprising a first terminal connected to the second contact of the SPDT switch via a second resistor, and a second terminal; and an electronic switch comprising a first terminal, a second terminal, and a third terminal, wherein the first terminal of the electronic switch is connected to the second terminal of the thermistor, and connected to the cathode of the switching element via a third resistor; the second terminal of the electronic switch is connected to a node between the thermistor and the second resistor, and connected to the gate of the switching element; and the third terminal of the electronic switch is connected to a node between the coil and the first resistor; wherein the thermistor is arranged adjacent to the light to sense temperature around the light for turning off the electronic switch when the temperature exceeds a threshold value of the electronic switch, so as to make the first contact connect to the third contact of the relay to turn off the light.