Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
1999-08-03
2001-06-12
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S297000, C315S20000A
Reexamination Certificate
active
06246184
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
BACKGROUND OF THE INVENTION
The present invention is related to the field of portable light sources, such as flashlights.
The light output from a typical incandescent lamp of the type used in portable light sources is very sensitive to the voltage applied to the lamp. It has been determined that light output intensity changes in proportion to the voltage raised to the power of 3.5. Additionally, the voltage supplied by a typical dry cell battery, such as an alkaline battery, diminishes steadily throughout its operating lifetime. Consequently, the light output from a flashlight tends to become quite dim relatively early in the operating lifetime of the batteries. At this point the user must choose whether to continue using the same batteries, suffering the reduced light output for a significant period of operating time, or to replace the batteries to obtain better light output. The latter option increases the cost of operating the flashlight.
There are several known techniques for addressing the general problem of improving flashlight performance and/or efficiency. U.S. Pat. Nos. 5,498,934 and 5,418,433 to Nilssen, for example, show flashlights in which a BOOST switch and associated circuitry are used to temporarily increase light output by up to 300%. This feature can be used to obtain a markedly increased light output for very brief periods, as may be required by a user. However, the technique does not address the problem of maintaining consistent high-quality light output as batteries age.
U.S. Pat. No. 4,949,014 to Gasvoda, U.S. Pat. No. 4,499,525 to Mallory and U.S. Pat. No. 4,326,161 to Kreinberg show-battery-powered lamps in which the lamp intensity is regulated to be substantially constant despite the diminishing of battery voltage over an operating lifetime. In all of these lamps, the nominal battery voltage is substantially greater than the voltage required to obtain the desired light intensity. The lamp intensity is regulated by varying the duty cycle of an electronic switch inserted in series between the batteries and the lamp. The slow response time of the lamp element is exploited to integrate the energy pulses. These devices require relatively high-voltage batteries, and the lifetime of the lamps may be reduced due to the direct application of high-amplitude rectangular ripple currents to the lamps.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, a light source is disclosed from which a substantially constant and full-intensity light output can be obtained despite the diminishing of battery voltage. A relatively small number of low-voltage cells can be used, enhancing portability. In one embodiment a standard flashlight can be retrofitted to obtain the enhanced performance associated with the invention.
The disclosed light source includes a lamp having a rated operating voltage, and one or more series-connected batteries collectively operative to provide electrical power to the lamp. The battery voltage generally diminishes during the operating lifetime of the batteries from an initial battery voltage substantially equal to the rated operating voltage of the lamp toward zero volts. A boost regulator circuit is coupled to transfer electrical power from the batteries to the lamp. The boost regulator circuit automatically maintains substantially the rated operating voltage to the lamp as the battery voltage diminishes, such that a major portion of the original battery energy is used in providing substantially constant and full output light intensity from the light source. Three different boost regulator circuits are disclosed, having different characteristics making them suitable for different customer requirements.
The light source includes a circuit assembly having the regulator circuit disposed on a planar circuit board. The circuit board is shaped to be disposed within the case of the light source between the lamp and one of the batteries. In one embodiment, the circuit board is in the shape of a disk, and is disposed within a cylindrical body of a light source. The circuit board includes electrical contacts on opposite planar surfaces to make electrical contact with the battery and the lamp. The circuit board also includes one or more common electrical contacts to be connected to a common connection in the light source between the batteries and the lamp. In one embodiment, the common electrical contact is a flexible contact extending from an edge of the circuit board to contact a common connection extending alongside the lamp and the adjacent battery.
Other aspects, features, and advantages of the present invention are disclosed in the detailed description that follows.
REFERENCES:
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patent: 4156166 (1979-05-01), Shapiro et al.
patent: 4228485 (1980-10-01), Hubbard et al.
patent: 4326161 (1982-04-01), Kreinberg
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patent: 4404624 (1983-09-01), Yamazaki
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patent: 4499525 (1985-02-01), Mallory
patent: 4887006 (1989-12-01), Kuratani
patent: 4972394 (1990-11-01), DiMarco
patent: 5144207 (1992-09-01), Brunson
patent: 5214353 (1993-05-01), Nilssen
patent: 5357411 (1994-10-01), Menke et al.
patent: 5418433 (1995-05-01), Nilssen
patent: 5430641 (1995-07-01), Kates
patent: 5498934 (1996-03-01), Nilssen
patent: 5530632 (1996-06-01), Shikano et al.
patent: 5684370 (1997-11-01), Watanabe
patent: 5839821 (1998-11-01), LeZotte
patent: 5859506 (1999-01-01), Lemke
patent: 5912552 (1999-06-01), Tateishi
Alemu Ephrem
Brady W. James
Swayze, Jr. W. Daniel
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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