Patent ID: 8487547

Claim:
A circuit, comprising: at least a first light emitting device coupled between a first power supply node and a first internal node; a current sense circuit; a disable circuit having a first disable path that couples the first internal node to a first power supply node in a passive mode; and a sense isolation circuit that, in the passive mode, electrically isolates the current sense circuit from current flowing through at least the first light emitting device, and in an operational mode couples the current sense circuit to the first internal node, wherein the at least one lighting device comprises light emitting diodes (LEDs), and wherein the LEDs are configured to be connected in series between the first power supply node and the first internal node so that the LEDs are reverse biased when a voltage difference between the power supply node and the first internal mode falls below a predetermined minimum difference, wherein when switching from an operational mode to the passive mode, the disable circuit couples the first internal node to the first power supply node after the sense isolation circuit isolates the current sense circuit from current flowing through at least the lighting device connection point; and when switching from the passive mode to the operational mode, the disable circuit isolates the first internal node from the first power supply node before the sense isolation circuit couples the current sense circuit to current flowing through at least the lighting device connection point.