Patent ID: 8564216
Filing Date: 2013-10-22
Classification: H05B

Abstract:
1. An electronic ballast comprising: an inverter; an inverter driver circuit effective to provide drive signals to the inverter to cause the inverter to generate an inverter output voltage at an inverter output; a resonant tank circuit coupled to the inverter output; first and second lamp connection nodes; a DC-blocking capacitor coupled between the resonant tank circuit and the first lamp connection node; a grounding circuit comprising a ground fault capacitor and a first resistor coupled in parallel between the second lamp connection node and ground, the grounding circuit effective to drain the second lamp connection node to ground; a lamp voltage detection circuit coupled between the first lamp connection node and ground and effective to measure an output voltage across the first and second lamp connection nodes from a signal at the first lamp connection node; a controller having a controller input terminal coupled to the lamp voltage detection circuit and effective to disable the inverter based on a received signal from the lamp voltage detection circuit being greater than a first predetermined threshold value or less than a second predetermined threshold value; and the lamp voltage detection circuit comprising a voltage divider circuit further comprising second and third resistors coupled in series between the first lamp connection node and ground, the controller input terminal coupled to a node between the second and third resistors.