Electronic circuits to extend battery life time

A low-current battery operated apparatus with a first voltage boosting circuit for operation with depleted batteries and a second circuit for operating with non-depleted batteries, and a circuit selector switch for selectively connecting a low-current component such as an LED with the first circuit or the second circuit.

BACKGROUND OF THE INVENTION

1. Field of the Invention (Technical Field)

Embodiments of the present invention relate a circuit that boosts battery voltage for low current draw devices, particularly for flashlights.

2. Description of Related Art

Over a billion people in third world countries do not have access to household electricity, resulting in a reliance on devices powered by expensive batteries. Given the average third world wage of a few dollars a day, 20-30% is spent on energy sources like batteries, creating a desperate need for improving battery lifetime. Batteries that, at a glance, are considered to be “dead” are discarded even though they still have remaining energy

Embodiments of the present invention solve this problem by incorporating a “Joule Thief” circuit (which boosts battery voltage) into low current draw devices, such flashlights, cell phones, laptops, tablets, radios, battery operated toys, mp3 players, two way radios, wireless electronics like keyboards and mice, game controllers, cars, remote controllers for TV's, stereos, etc., to utilize remaining energy in batteries that are otherwise considered “dead” when used in these devices, thus extending battery life. For instance, conventional light-emitting-diodes (LED) flashlights, such as those commercially sold in department stores and on the Internet, most often require anywhere from one to six AAA, AA, C, or D size batteries for proper function, and comprise of one or more LEDs lights that provide illumination when the flashlight is turned on. A common flashlight provides useful illumination from the battery source until the batteries become discharged to a point that the amount of illumination is no longer useful and the batteries are either replaced or recharged. There is a need for devices that can utilize the energy that remains in the batteries.

Embodiments of the invention use a simple and inexpensive circuit, which can be incorporated into low current draw devices, allowing the remaining energy in a “dead” battery to be used. This type of circuit takes a low voltage source (“dead” batteries), steps it up to a higher voltage using a toroid as an inductor (similar in function to a step up transformer) and then rapidly discharges a voltage pulse to the component of the device needing power, doing this several hundred to several hundred thousand times a second by using the transistor as a fast switch. While the circuit is turning on and off very rapidly, it appears as if the device is continually on. By stepping up the voltage from a “dead” battery, the user can drain the last amount of energy from it and use it to power the device. This is energy which would otherwise be wasted. Embodiments of the invention for optimized Joule Thief circuit designs cost pennies to retrofit in current devices when produced in bulk, paying for themselves in the first set of batteries. In one embodiment, a voltage sensing circuit is added that automatically senses when the battery source voltage drops below a useful value, and automatically engages a voltage increasing electronic circuit. Embodiments of the invention do not only significantly reduce energy costs for people in third world countries, they reduce battery landfill pollution through the extension of battery life.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the invention comprise a battery operated flashlight comprising a light emitting component, one or more batteries, a first circuit for operation of the light emitting component with non-depleted batteries, a second circuit for operation of the light emitting component with depleted batteries, the second circuit comprising a transistor, the transistor comprising a base, a collector, and an emitter, the second circuit comprising a first wire and a second wire, the first and the second wires wrapped around a ferrite core, a resistor connecting the first wire and the second wire in series with one another, the first wire connecting the base of the transistor to the resistor, the second wire connecting the collector of the transistor to the resistor, and a circuit selector switch for selectively connecting the light emitting component with the first circuit or the second circuit. In one embodiment, in the battery operated flashlight, the second wire wraps around the ferrite core between 1 and 15 times. In one embodiment, the second wire wraps around the ferrite between 2 and 10 times. In one embodiment, the second wire wraps around the ferrite between 3 and 7 times. In one embodiment, the light emitting component comprises one or more light emitting diodes. In one embodiment, the transistor is an NPN 2N2222 transistor. In one embodiment, the resistor has a resistance of about 1 kΩ. In one embodiment, the ferrite core comprises a toroid shape. In one embodiment, the ferrite core comprises an inductance of about 100 microhenries or higher. In one embodiment, the circuit selector switch comprises a third circuit which automatically senses voltage of batteries and selectively switches between said first or said second circuit based on a predetermined voltage. In one embodiment, the third circuit comprises a solid state relay. In one embodiment, the solid state relay comprises an LCC120 chip.

Embodiments of the present invention further comprise an electrical circuit comprising: an electrical load, one or more batteries, a first circuit for operation of the load with non-depleted batteries, a second circuit for operation of the load with depleted batteries, the second circuit comprising a transistor, the transistor comprising a base, a collector, and an emitter; the second circuit comprising a first wire and a second wire, the first and the second wires wrapped around a ferrite core, a resistor connecting the first wire and the second wire in series with one another, the first wire connecting the base of the transistor to the resistor, the second wire connecting the collector of the transistor to the resistor; and a circuit selector switch for selectively connecting the load with the first circuit or the second circuit. In one embodiment the circuit selector switch comprises a third circuit which automatically senses voltage of batteries and selectively switches between the first or the second circuit based on a predetermined voltage. In one embodiment, the third circuit comprises a solid state relay. In one embodiment, the solid state relay comprises an LCC120 chip. In one embodiment, the second wire wraps around the ferrite between 3 and 7 times. In one embodiment, the ferrite core comprises a toroid shape. In one embodiment, the ferrite core comprises an inductance of about 100 microhenries or higher. In one embodiment, the resistor has a resistance of about 1 kΩ.

DETAILED DESCRIPTION OF THE INVENTION

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention. However, upon studying this application, it will be understood by one of ordinary skill in the art that the embodiments may be practiced without these specific details. For instance, well known operation or techniques may not be shown in detail. Technical and scientific terms used in this description have the same meaning as commonly understood to one or ordinary skill in the art to which this subject matter belongs.

As used throughout this application, the term “non-depleted batteries” is intended to include one or more batteries which contain sufficient energy to power a desired component without use of a voltage-increasing circuit. As used throughout this application the term “depleted batteries” is intended to include one or more batteries which do not contain sufficient energy to power a desired component unless a voltage-increasing circuit, such as those of the embodiments of the present invention are used.

Referring now to the figures, and more particularly toFIG. 1, in one embodiment, electronic circuit10comprises component12, which preferably is a component of a low current draw device, the performance of which is not affected by very rapid pulsing of power, for example, an LED of any number, type, color or configuration of light source that provides illumination. Preferably, electronic circuit10also comprises bipolar junction transistor14and battery source16. In a preferred embodiment, electronic circuit10further comprises ferrite toroid18with wire wrapped around it, resistor20, and switch22. Although ferrite toroid18is preferably used, other shapes of ferrite cores can also be used

In one embodiment, when switch22is turned on, voltage increasing electronic circuit10is activated and the voltage from battery source16is increased. If battery source16includes weak or “dead” batteries, battery source16can still be used to power component12as a result of the building up of a magnetic field in ferrite toroid18. Preferably, when ferrite toroid18becomes saturated with energy, bipolar junction transistor14is used as a fast switch, shutting off and collapsing the magnetic field, which results in an increased voltage that will momentarily power component12. This entire event may occur at rates greater than a hundred kilohertz. If, for example, component12is an LED light source, it will blink on and off at a rate so fast, that it cannot be detected by the human eye. Thus, to a user of a flashlight operating with this circuit, it would appear as if the device is performing normally.

Referring now toFIG. 2, there is shown a close-up diagram of ferrite toroid18with two different wires wrapped around it. Wire24is shown with dash marks to distinguish it from wire26, which is shown as a plain black wire. The ends of the wires24and26are joined and they parallel each other as they wrap around ferrite toroid18so that they can oppose one another in terms of conventional current flow, which allows the magnetic field in ferrite toroid18to build up and then quickly collapse, generating enough voltage to power component12, even if the voltage of battery source16is too low to power component12under normal conditions. Preferably wires24and26wind around ferrite toroid18between approximately 1 and approximately 15 times; more preferably between approximately 2 and approximately 10 times; and most preferably, between approximately 3 and approximately 7 times.

Preferably, resistor20is disposed between ferrite toroid18and bipolar junction transistor14. In a preferred embodiment, resistor20is preferably about one thousand ohms and switch22is preferably a single pole double throw switch disposed in a suitable location, for example, between battery source16and ferrite toroid18.

Referring now toFIG. 3, there is shown a close-up view of bipolar junction transistor14, which preferably comprises collector28, shown on the left, base30, shown in the middle, and emitter32, shown on the right. In a preferred embodiment, collector28, base30, and emitter32are preferably connected as shown inFIGS. 1 and 3for electronic circuit10to perform effectively.

Preferably the components in a given device are of a certain type or range of types in order for an embodiment of voltage increasing electronic circuit to work. For instance, in an LED light source, its voltage requirements must be matched to the battery source (e.g., three volts is common). Furthermore, a bipolar junction transistor must be able to handle the voltage and switching requirements of the voltage increasing electronic circuit. A typical transistor that works well is, for example, the NPN 2N2222. Furthermore, a ferrite toroid should have sufficient inductance (e.g., about 100 microhenries or higher) to generate a strong enough magnetic field. As is with most electronic circuits, component values can be changed within a certain range and still work. The values stated here are such that the voltage increasing electronic circuit can be built and will work, but optimizing the circuit to maximize battery life will result in different values for different loads and in different applications.

Referring toFIG. 4, in one embodiment, electronic circuit10is disposed in area21of a flashlight comprising batteries17in housing23, and on/off switch25. Electronic circuit10(FIG. 10) is very inexpensive and can easily be produced for just a few pennies in large quantities.

Because electronic circuit10has resistance, which consumes battery energy, it is preferably not engaged in the device until the batteries appear to be dead. In one embodiment, a voltage sensing circuit is added that automatically senses when the battery source voltage drops below a useful value, and automatically engages a voltage increasing electronic circuit, such as electronic circuit10. In one embodiment, the additional circuit also turns off the device when the voltage from the voltage increasing electronic circuit10is no longer enough to power a given component, for example component12. Some example include, but are not limited to, (1) a microcontroller that can be programmed to turn on a particular circuit at a certain voltage; (2) a silicon controlled rectifier (SCR) configuration of transistors to act as a sort of solid state relay to allow current through one path at high voltage, and then current through another path at the lower voltage; (3) a low voltage relay switch that runs a device such as a flashlight normally at high voltage or trigger and run only the Joule Thief at lower voltage; (4) a comparator chip used with several resistors and diodes to switch circuit paths based on of the voltage; or (5) a simple battery-tester-circuit set up that powers either the LED normally or the Joule Thief depending on the voltage of the battery, etc.

FIG. 9is a schematic of circuit100, which is capable of integrating diverse switches such as, but not limited to, those in examples (1) through (5) above. Circuit100preferably comprises voltage boosting circuit102, which is connected to a single pole double throw switch104(of any type and/or controlled by any device) to power a low-power component, for example LED106. Preferably, voltage boosting circuit102comprises resistor103, inductor105, and bipolar junction transistor107, and all these elements are coupled as shown. In operation, the combined circuits receive one positive input108and one negative input109by connecting them to positive and negative terminals or a battery respectively. Preferably, switch104is adjusted to have one circuit path closed at a time based on the positive input with reference to the negative input. If, for example, the positive input voltage is above the chosen level, normally-open circuit path110becomes closed, allowing LED106or other low power electronic device to be powered by a voltage source (not shown), and not by voltage boosting circuit102. If, for example, the positive input voltage is below a given chosen level, normally-closed circuit path113is then completed allowing LED106or other electronic device to be powered by use of voltage boosting circuit102and not through normally-open circuit path110. The chosen voltage level that switch104is to toggle at is set to be the voltage at which normally-open circuit path110will be closed based on the design of the switch.

Referring to the wire diagram ofFIG. 10, in one embodiment, a single pole double throw switch is created through, for example, circuit200, which preferably comprises voltage boosting circuit202, and is preferably further configured to include additional resistor201and LCC120 chip205, which is a solid state relay. Together, circuits200and202can be connected to one or more batteries209in order to power, for example, LED208, or another low power electronic device. Preferably, voltage boosting circuit202comprises resistor203, inductor204, and bipolar junction transistor207, and all these elements are coupled as shown.

LCC120 chip205requires about 10 mA for normally-open path206to be completed (the path that runs the LED directly off of battery209). The switching voltage level is set by the resistance connected to pin2of LCC120 chip205. With a higher resistance the switch will only connects normally-open path206when the voltage is higher, and likewise if the resistance is lower the chip will connect the normally-open path206at a lower voltage. Thus, based on the desired switching voltage level, a corresponding resistance value may be selected to set LCC120 chip205to toggle around that voltage. Circuit200will then power LED208(or other electronic device) directly by the input voltages if the voltage is above a given chosen voltage, and if the input voltage drops below the chosen voltage LCC120 chip205will toggle and power LED208(or other electronic device) only with voltage boosting circuit202.

Referring toFIG. 11(a schematic diagram of the switch and voltage boosting circuit), in one embodiment, single pole double throw solid-state relay303is provided in circuit300, which is preferably connected to voltage boosting circuit307, and is preferably further configured to include additional resistor302, and one or more batteries301to power LED310, or another low power electronic device. Preferably, voltage boosting circuit307comprises resistor306, inductor308, and bipolar junction transistor309, with all these elements being coupled as shown.

Preferably, solid state relay303may be of any type and is designed to activate the normally-open path304or normally-closed path305at the desired voltages. The switching voltage level is set by the resistor302connected to solid-state relay303. With a higher resistance, the solid-state relay303will only connect the normally-open path304when the voltage is higher, and likewise if the resistance is lower the solid-state relay303will connect the normally-open path304at a lower voltage. Thus, based on the desired switching voltage level a corresponding resistance value may be selected to set solid-state relay303to toggle around that voltage. Circuit300will then power LED310(or other electronic device) directly by the input voltage of battery301if the voltage is above a given chosen voltage, and if the input voltage drops below the chosen voltage, solid-state relay303will toggle and power LED310(or other electronic device) only with voltage boosting circuit307.

INDUSTRIAL APPLICABILITY

A battery-operated LED flashlight was built incorporating the electronic circuit ofFIG. 1. Referring to Table 1 below, experiments were conducted to find the ideal number of windings around the toroid of an electronic circuit according to embodiments of the invention to maximize battery efficiency in the flashlight. This was done by testing from 1 to 15 windings and recording the Lux produced for optimum (low voltage, low current) operation. These experiments showed that five windings provided the best balance of intensity produced versus energy used.

TABLE 1All tests at 1 in and 1.7 VLux produced:1winding0.02windings~30.03windings1453.24windings1128.45windings773.86windings614.97windings145.38windings346.79windings357.810windings488.211windings106.412windings325.913windings437.614windings210.115windings208.5

Referring to Table 2 below, further experiments were conducted to identify the optimum resistance of the resistor in the electronic circuit. The electronic circuit was connected to a pair of AA batteries with voltage limited by a precision potentiometer. Resistances from 100 ohms to 2.2 kΩ were tested. The voltage needed to produce 50 lux with each resister in the circuit was then recorded and the results were recorded to find the best resistance for the circuit (a balance of current draw and reliable operating range). These experiments showed that while resistors between 100 ohms and 2.2 kΩ worked well with the electronic circuit, a resistance of about 1 kΩ balances the ability to run at low voltages and not drain the remaining current too rapidly.

In addition, Experiments were conducted to collect data of voltage decay versus illumination decay utilizing two new AA batteries in a regular flashlight. The voltage and illumination were measured using a Vernier Lab Quest data logger with a calibrated illumination sensor and voltage probe to measure the light output by the LED and the voltage across the positive and negative input of the LED. The graphs inFIGS. 5 and 6show the time versus lux and time versus voltage of the regular flashlight respectively.

Additional experiments demonstrated that an electronic circuit embodiment of the present invention requires a minimum of 1.2 volts to produce 50 lux in the LED flashlight, and that the total time of usable light provided to be about 67 hours, using this minimum voltage level. SeeFIG. 7.

Additional experiments were conducted to determine additional battery life for the flashlight containing an embodiment of an optimized electronic circuit. This was done using the Vernier Lab Quest to measure voltage and illumination of the flashlight under low voltage (“dead” battery) conditions. This involved testing the flashlight comprising the embodiment of the electronic circuit from the starting voltage when the normal flashlight is too weak, to the point at which the optimized electronic circuit can no longer produce 50 lux using the “dead” batteries. These experiments showed that the extra battery life the embodiment of electronic circuit provided was approximately 16%, or 11 hours. SeeFIG. 8.

The preceding example can be repeated with similar success by substituting the generically or specifically described components and/or operating parameters of this invention for those used in the preceding examples. Note that in the specification and claims, “about” or “approximately” means within twenty percent (20%) of the numerical amount cited.