Circuitry for Portable Lighting Devices and Portable Rechargeable Electronic Devices

Abstract

A portable electronic device, such as a flashlight, with a circuit for reducing the initial surge of current that is sent through the lamp filament when a flashlight is turned on is provided. The circuit reduces the stresses placed on the lamp bulb when it is turned on, thereby extending the life expectancy of the lamp bulb. A flashlight with beacon mode that produces light according to a duty cycle of less than 11% is also disclosed.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 13 / 373,802, filed Jan. 20, 2010, which is a continuation of U.S. patent application Ser. No. 11 / 351,307, filed Feb. 8, 2006, which is a continuation-in-part of U.S. patent application Ser. No. 11 / 007,771, filed Dec. 7, 2004, now U.S. Pat. No. 7,579,782. The foregoing applications are incorporated by reference as if fully set forth herein.FIELD OF THE INVENTION[0002]The field of the present invention relates to portable electronic devices, including hand held portable lighting devices, such as flashlights, and their circuitry.BACKGROUND[0003]Various hand held or portable lighting devices, including flashlight designs, are known in the art. Flashlights typically include one or more dry cell batteries having positive and negative electrodes. In certain designs, the batteries are arranged in series in a battery compartment of a barrel or housing that can be used to hold th...

AI Technical Summary

Benefits of technology

The patent describes a portable rechargeable electronic device with external charging contacts and a short protection circuit. This circuit prevents power from flowing through the charging contacts when they are short-circuited, ensuring that the device can continue to operate while the contacts are short-circuited. The device can continue to operate even if there is a short across the charging contacts. Additionally, the patent describes a portable lighting device with a circuit for reducing the initial surge of current that is sent through the lamp when the device is turned on. This circuit helps to prolong the life of the lamp bulb. Furthermore, the patent discusses a power control circuit that adjusts the voltage signal sent to the power switch of the device, allowing for an increased amount of current to flow through the power switch over a set period of time when the flashlight is turned on. This circuit helps to control the power output of the device and improve its overall performance.

Problems solved by technology

One of the disadvantages of a mechanical switch is that they are prone to wear and tear as well as oxidation of the elements that physically make and break the circuit.

Mechanical switches also do not permit automated or regulated modes of activating and deactivating a flashlight.

Another disadvantage of traditional flashlights is that when they are switched on they instantly allow large amounts of current to flow from the batteries through the lamp filament, thereby stressing the filament.

This surge of current occurs because the resistance of the lamp's filament is very low when the filament is cold.

Although the current surge during this transient stage exceeds the bulb's design limits, the duration of the transient stage is short enough that bulbs generally survive the current surge.

Over time, however, this rush of current causes damage to the lamp by stressing the filament and ultimately failure of the lamp filament.

Indeed, it is generally during this transient stage that a lamp filament will ultimately fail.

Yet another disadvantage of traditional flashlights is that they are generally powered with alkaline or dry cell batteries.

Replacing batteries is an inconvenience and an additional expense to a flashlight user.

Furthermore, alkaline or dry cell batteries are heavy, thereby adding to the overall weight of the flashlight.

They are, however, relatively large and must be refilled with liquid electrolyte after being used for a period of time.

Due to their bulky size and weight, even heavier than alkaline / dry cell batteries, rechargeable lead-acid batteries are usually used with wall-mounted safety lighting fixtures, motorcycles, and automobiles, but are generally not considered suitable for use with portable lighting devices, such as flashlights.

However, these batteries have a disadvantage of causing heavy metal pollution.

However, a lithium-ion battery can explode if it is charged beyond its safe limits, or if its terminals are shorted together.

Further, over discharging a lithium-ion battery can permanently damage the lithium-ion cell.

Unfortunately, such a configuration requires the use of plugs, special inserts, alignment tabs or a complex cradle to recharge the batteries.

Obstructing access to the recharging contacts is not, however, a viable solution in the case of flashlights or other rechargeable devices where design requirements dictate that the charging contacts or rings be exposed.

Such inadvertent interruptions may be dangerous when a user is working in an unlit area, especially for law enforcement and emergency response personnel.

And, while a simple diode can be placed in the recharging circuit to prevent accidental short circuits from being created across the charging rings or contacts for other rechargeable battery chemistries, such as nickel-cadmium and nickel metal hydride, this solution is not viable for lithium-ion battery packs.

A simple diode cannot be used in these circumstances because the forward voltage drop of a diode varies greatly while charging lithium-ion batteries requires very tight control over the termination voltage.

In view of the foregoing, rechargeable lithium-ion battery technology has not been adopted for use in portable electronic devices with exposed charging contacts, such as rechargeable flashlights.

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