Multi-mode portable lighting device
A lighting device with a light source powered by batteries connected in series utilizes a current-limited load switch which regulates current delivered to the light source from the batteries through use of a controller electrically coupled in series with a mechanical power switch so that when the mechanical power switch is opened, the controller is not powered by the batteries, the controller including an output for providing a control signal for controlling the opening and closing of the current-limited load switch, and current delivered to the light source by the current-limited load switch is set by a resistor connected to an ISET pin of the current-limited load switch.
1. A lighting device powered by a plurality of batteries connected in series, comprising:
a light source;
a current-limited load switch which regulates current delivered to the light source from the plurality of batteries; and
a controller electrically coupled in series with a mechanical power switch so that when the mechanical power switch is opened, the controller is not powered by the plurality of batteries, the controller including an output for providing a control signal for controlling the opening and closing of the current-limited load switch;
wherein current delivered to the light source by the current-limited load switch is set by a resistor connected to an ISET pin of the current-limited load switch.
2. The lighting device of claim 1 wherein the light source is comprised of at least one LED.
3. The lighting device of claim 2 wherein the current-limited load switch modulates DC current from the plurality of batteries to a pulsed current.
4. The lighting device of claim 3 wherein the resistor is selected based on a minimum output current desired to be output from the current-limited load switch delivered to the light source.
5. The lighting device of claim 4 wherein the controller is configured to control the output of the current-limited load switch using a pulse-width modulation (“PWM”) signal.
6. The lighting device of claim 5 wherein an average output current from the current-limited load switch is controlled to a desired level by adjusting the duty cycle of the PWM signal.
7. The lighting device of claim 6 wherein the duty cycle of the PWM is adjusted through use of a calibration procedure.
8. The lighting device of claim 7 wherein the calibration procedure is comprised of the steps of setting the duty cycle at an initial duty cycle value of 100% and then decrementing the initial duty cycle value during a functional test until an appropriate duty cycle is reached to produce the desired level.
9. The lighting device of claim 8 wherein the appropriate duty cycle is decreased by a preselected amount to achieve a desired power savings for a reduced power mode.