Hybrid light source

A method of illuminating a light source to produce a total light intensity throughout a dimming range from a low-end intensity to a high-end intensity, the method comprising the steps of:

• illuminating a high-efficiency lamp to produce a percentage of the total light intensity;
• illuminating a low-efficiency lamp to produce a percentage of the total light intensity;
• mounting the high-efficiency lamp and the low-efficiency lamp to a common support;
• individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that the total light intensity of the hybrid light source ranges throughout the dimming range;
• controlling the high-efficiency lamp and the low-efficiency lamp near the high-end intensity, such that first percentage of the total light intensity produced by the high-efficiency lamp is greater than the second percentage of the total light intensity produced by the low-efficiency lamp when the total light intensity is near the high-end intensity;
• decreasing the first percentage of the total light intensity produced by the high-efficiency lamp as the total light intensity decreases;
• increasing the second percentage of the total light intensity produced by the low-efficiency lamp as the total light intensity decreases;
• turning off the high-efficiency lamp when the total light intensity is below a transition intensity;
• and
• controlling the low-efficiency lamp such that the low-efficiency lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below the transition intensity.

A hybrid light source adapted to receive power from an AC power source, the hybrid light source comprising:

• first and second input terminals adapted to be operatively coupled to the AC power source;
• a high-efficiency light source circuit having a high-efficiency lamp, the high-efficiency light source circuit drawing current from the AC power source through the input terminals for powering the high-efficiency lamp;
• a low-efficiency light source circuit having a low-efficiency lamp, the low-efficiency light source circuit drawing current from the AC power source through the input terminals for powering the low-efficiency lamp;
• and
• a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit to individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that a total light output of the hybrid light source ranges from a minimum total intensity to a maximum total intensity;
• wherein the hybrid light source is characterized by a low impedance between the first and second input terminals throughout the length of each half-cycle of the AC power source and wherein the low impedance between the first and second input terminals has an average magnitude of approximately 1.44 kΩ or less throughout the length of each half-cycle.

A dimmable hybrid light source adapted to receive a phase-controlled voltage, the hybrid light source comprising:

• two input terminals adapted to receive the phase-controlled voltage;
• a full-wave rectifier circuit coupled between the input terminals and generating a rectified voltage at output terminals;
• a high-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a high-efficiency lamp;
• a low-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a low-efficiency lamp, the low-efficiency light source circuit comprising a semiconductor switch coupled in series electrical connection with the low-efficiency lamp, the series combination of the semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit;
• a zero-crossing detect circuit operatively coupled between the input terminals for detecting when the magnitude of the phase-controlled voltage becomes greater than a predetermined zero-crossing threshold voltage each half-cycle of the phase-controlled voltage;
• and
• a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit for individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the zero-crossing detect circuit, such that a total light output of the hybrid light source ranges from a minimum total intensity to a maximum total intensity, the control circuit operable to turn off the high-efficiency lamp when the total light intensity is below a transition intensity, such that the low-efficiency lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below the transition intensity, the control circuit operable to control the amount of power delivered to the low-efficiency lamp to be greater than a minimum power level when the total light intensity is above the transition intensity;
• wherein the control circuit controls the amount of power delivered to the low-efficiency lamp to the minimum power level when the total light intensity of the hybrid light source is at the maximum intensity.

A dimmable hybrid light source adapted to receive a phase-controlled voltage, the hybrid light source comprising:

• two input terminals adapted to receive the phase-controlled voltage;
• a full-wave rectifier circuit coupled between the input terminals and generating a rectified voltage at output terminals;
• a high-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a high-efficiency lamp;
• a low-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a low-efficiency lamp, the low-efficiency light source circuit comprising a semiconductor switch coupled in series electrical connection with the low-efficiency lamp, the series combination of the semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit;
• a zero-crossing detect circuit operatively coupled between the input terminals for detecting when the magnitude of the phase-controlled voltage is approximately zero volts;
• and
• a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit for individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the zero-crossing detect circuit;
• wherein the semiconductor switch is rendered conductive when the phase-controlled voltage across the hybrid light source is approximately zero volts.

A dimmable hybrid lamp comprising:

• a high-efficiency dimmable lamp;
• a low-efficiency dimmable lamp;
• and
• a common control circuit coupled to each of said dimmable lamps and operable to simultaneously vary said dimmable lamps from their respective minimum intensities to maximum intensities to control a total light intensity of said hybrid lamp from a low-end intensity to a high-end intensity across a dimming range;
• wherein only said low-efficiency lamp is turned on when said total light intensity is less than a transition intensity, and said high-efficiency lamp is only turned on when said total light intensity is above said transition intensity, whereby said low-efficiency lamp turns on before said high-efficiency lamp turns on as said hybrid lamp is dimmed from said low-end intensity to said high-end intensity.

A process of dimming a hybrid lamp comprising the steps of:

• positioning a low-efficiency lamp in close proximity to a high-efficiency lamp;
• continuously varying a high-efficiency gas discharge lamp from a first minimum intensity to a first maximum intensity;
• varying said low-efficiency lamp from a second minimum intensity to a second maximum intensity which is lower said first minimum intensity of said high-efficiency lamp;
• and
• simultaneous controlling both of said lamps to control a light output of said hybrid lamp from a low-end intensity to a high-end intensity, such that said light output of said hybrid lamp has a red color shift as said hybrid lamp is dimmed toward said low-end intensity.