End-of-life protection circuit and method for high intensity discharge lamp ballast

An apparatus that powers a lamp and detects an end of life (EOL) condition of the lamp, comprising:

• a ballast that applies a voltage to the lamp to cause the lamp to start emitting light;
• a measurer that measures a value representing the voltage applied to the lamp at a predetermined timing after an expiration of a mask-off period;
• and
• a calculator that performs a rectification calculation to determine whether the lamp exhibits a rectification behavior indicating said EOL condition.

A method for detecting an end of life (EOL) condition of a lamp, comprising:

• supplying a voltage to the lamp to cause the lamp to emit light;
• obtaining a number of rectification measurements during a predefined measurement window timing after an expiration of a mask-off period;
• determining whether a certain percentage of said number of rectification measurements during the predefined measurement window exceeds a set rectification threshold;
• and
• removing the voltage to the lamp when the number of rectification measurements during the predefined measurement window that exceeds the set rectification threshold is at least equal to the certain percentage.