Cat-ear power supply having a latch reset circuit

A load control device for controlling an amount of power delivered to an electrical load from an AC power source, the load control device comprising:

• a controllably conductive device adapted to be coupled in series electrical connection between the source and the load, the controllably conductive device having a control input for controlling the controllably conductive device between a non-conductive state and a conductive state;
• a controller operatively coupled to the control input of the controllably conductive device for controlling the semiconductor switch between the non-conductive state and the conductive state;
• a cat-ear power supply for generating a DC voltage, the power supply comprising a controllably conductive switching circuit for selectively charging an energy storage capacitor to produce the DC voltage, the controllably conductive switching circuit operable to be conductive to charge the energy storage capacitor near the beginning of a half-cycle of the AC power source, the power supply further comprising a latch circuit for controlling the controllably conductive switching circuit to be non-conductive in response to the magnitude of the DC voltage, and a switch voltage monitor circuit for controlling the controllably conductive switching circuit to become non-conductive and also resetting the latch circuit when the magnitude of a switch voltage across the controllably conductive switching circuit exceeds a predetermined switch voltage threshold;
• wherein the controllably conductive switching circuit is operable to become conductive to charge the energy storage capacitor near the end of the half-cycle when the magnitude of the switch voltage drops below the predetermined switch voltage threshold.

A power supply for a load control device for controlling the amount of power delivered to an electrical load from an AC power source, the load control device operable to receive an AC line voltage of the AC power source, the power supply operable to generate a DC voltage, the power supply comprising:

• an energy storage capacitor;
• a controllably conductive switching circuit coupled in series electrical connection with the energy storage capacitor for selectively charging the energy storage capacitor to produce the DC voltage, the controllably conductive switching circuit operable to become conductive to charge the energy storage capacitor near the beginning of a half-cycle of the AC power source;
• a latch circuit coupled to the controllably conductive switching circuit, wherein the latch circuit controls the controllably conductive switching circuit to become non-conductive in response to the magnitude of the DC voltage;
• and
• a switch voltage monitor circuit coupled to the controllably conductive switching circuit, such that the switch voltage monitor circuit maintains the controllably conductive switching circuit non-conductive when the magnitude of the AC line voltage exceeds a predetermined line voltage threshold;
• characterized in that the switch voltage monitor circuit is further coupled to the latch circuit such that the latch circuit is reset when the magnitude of the AC line voltage exceeds the predetermined line voltage threshold, and the controllably conductive switching circuit is operable to become conductive to charge the energy storage capacitor near the end of the half-cycle when the magnitude of the AC line voltage drops below the predetermined line voltage threshold.