Microcontroller based ignition in high frequency ceramic metal halide lamps
AssigneeOsram Sylvania Inc.
InventorAndrew Johnsen
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Abstract
A high frequency ballast for a metal halide lamp comprises a controller, a switch, and an oscillator. The controller selectively enables and disables the oscillator via the switch to ignite the lamp. The switch selectively tunes and detunes an inductor of the oscillator by altering an inductance of the inductor. When the inductor is tuned, the oscillator oscillates and provides power to the lamp. When the inductor is detuned, the oscillator does not oscillate and does not provide power to the lamp.
Claims20
A method of controlling an oscillator of a high frequency ballast driving a metal halide lamp comprising:
- receiving power from an alternating current (AC) power supply;
- converting the received power to direct current (DC) power wherein the DC power is provided to the controller of the ballast;
- initializing a controller of the ballast in response to receiving the DC power at the controller;
- tuning an inductor of the oscillator, wherein the oscillator generates AC power from the converted DC power and provides the generated AC power to the lamp when the inductor is tuned;
- monitoring a current of a power supply loop of the oscillator;
- and
- detuning the inductor of the oscillator when the monitored current is above a threshold, said voltage threshold indicating that the lamp has not ignited.
A high frequency metal halide lamp ballast for providing power to a metal halide lamp from an alternating current (AC) power source, said ballast comprising:
- a direct current (DC) converter for receiving AC power from the AC power source and providing DC power;
- an oscillator connected to the converter for receiving the DC power from the DC converter and connected to the lamp for providing a high frequency output to the lamp, said oscillator comprising an inductor circuit having an inductor;
- a switch connected to the inductor circuit having a first mode in which the inductor is tuned and the oscillator provides the high frequency output to the lamp and having a second mode in which the inductor is detuned and the oscillator does not provide the high frequency output to the lamp;
- and
- a controller for controlling the mode of the switch to selectively tune or detune the inductor of the oscillator.
A light source comprising:
- a metal halide lamp for providing light in response to receiving power;
- and
- a ballast for igniting the lamp and providing power to the lamp from an alternating current (AC) power source, said ballast comprising:
- a direct current (DC) converter for receiving AC power from the AC power source and converting the received AC power to DC power;
- an oscillator connected to the converter for receiving the DC power from the DC converter and connected to the lamp for providing a high frequency output to the lamp, said oscillator comprising an inductor circuit having an inductor;
- a switch connected to the inductor circuit having a first mode in which the inductor is tuned and the oscillator provides the high frequency output to the lamp and having a second mode in which the inductor is detuned and the oscillator does not provide the high frequency output to the lamp;
- and
- a controller for controlling the mode of the switch to selectively tune or detune the inductor of the oscillator.
Dependencies are inferred from the claim text.