Electronic switch having an in-line power supply

摘要

A two-wire smart load control device, such as an electronic switch, for controlling the power delivered from a power source to an electrical load comprises a relay for conducting a load current through the load and an in-line power supply coupled in series with the relay for generating a supply voltage across a capacitor when the relay is conductive. The power supply controls when the capacitor charges asynchronously with respect to the frequency of the source. The capacitor conducts the load current for at least a portion of a line cycle of the source when the relay is conductive. The load control device also comprises a bidirectional semiconductor switch, which is controlled to minimize the inrush current conducted through the relay. The bidirectional semiconductor switch is rendered conductive in response to an over-current condition in the capacitor of the power supply, and the relay is rendered non-conductive in response to an over-temperature condition in the power supply.

主权项

1. A two-wire electronic switch for controlling the power delivered from an AC power source to an electrical load, the electronic switch comprising:
a latching relay adapted to be coupled in series electrical connection between the source and the load, the latching relay arranged to conduct a load current through the load when the relay is conductive; a controller configured to control the relay to be conductive and non-conductive to turn the load on and off, respectively; an output capacitor arranged to develop a DC supply voltage for powering the controller; and an in-line power supply coupled in series electrical connection with the relay, the in-line power supply further coupled to the output capacitor for generating the DC supply voltage across the output capacitor when the relay is conductive, the power supply configured to conduct the load current through the output capacitor for at least a portion of a line cycle of the AC power source when the relay is conductive; wherein the relay is rendered non-conductive in response to an over-temperature condition in the electronic switch.