Patent ID: 8274240
Filing Date: 2012-09-25
Classification: H05B

Abstract:
1. A two-wire switching circuit for controlling the power delivered from an AC power source to an electrical load, the switching circuit comprising: a mechanical air-gap switch adapted to be coupled in series electrical connection between the AC power source and the electrical load; a turn-on delay circuit adapted to be coupled in series electrical connection with the mechanical air-gap switch when the mechanical switch is in a first switch position, the turn-on delay circuit operable to conduct a control current through the mechanical air-gap switch when the mechanical switch is in the first switch position; a controllably conductive device having a control input and coupled in parallel electrical connection with the turn-on delay circuit, the controllably conductive device adapted to be coupled in series electrical connection between the AC power source and the electrical load when the mechanical switch is in the first switch position, the controllably conductive device operable to change from a non-conductive state to a conductive state in response to the turn-on delay circuit after a first predetermined time from when the mechanical air-gap switch changes to the first switch position; and a latching circuit coupled to the turn-on delay circuit and the control input of the controllably conductive device, the latching circuit responsive to the turn-on delay circuit to control the controllably conductive device to the conductive state after the first predetermined time from when the mechanical air-gap switch changes to the first switch position, such that the controllably conductive device stays latched in the conductive state; wherein the mechanical air-gap switch and the controllably conductive device are operable to conduct a load current from the AC power source to the electrical load when the mechanical air-gap switch is in the first switch position.