Patent Application
20110248632
This invention relates to a multi-purpose light source which can be used in a range of different applications, including both medical and domestic.
1. Field of the Invention
Light sources in the form of torches utilising small Faraday generators are well known, in which an electromotive force is generated by moving a permanent magnet in a fixed coil to power Light Emitting Diodes (LEDs) or incandescent bulbs. Such devices are described in, for example, U.S. Pat. Nos. 4,114,305, 5,987,5714 and 6729744.
2. State of the Art
In many medical procedures, a bright light source is required for a short period of time, for example inspection of organs such as ears, eyes, nose and for carrying out procedures such as tracheal intubation using a laryngoscope. Conventional laryngoscopes have a light source which is provided by means of a handle containing batteries which operate an incandescent bulb such as tungsten filament bulb in the laryngoscope blade. International Patent Application No. PCT/GB2006/050148 describes a light source for use in medical procedures, which comprises a handle and a Faraday generator within the handle which powers a light emitting diode. Other instruments such as opthalmoscopes and otoscopes use a light source which shines directly into the eyes or ears when examining a patient are specifically designed for such a purpose and such instruments have a handle containing batteries which operate an incandescent bulb to provide the light required.
It is an object of the present invention to provide an improved portable light source including a Faraday generator, in which a user is given a warning that stored charge is running low and a constant delivery of current to the LED is ensured to maximise efficiency.
In accordance with the present invention, there is provided a control circuit for a device comprising a power storage device and an electricity generating means for intermittently supplying power to said storage device, said control circuit comprising a microcontroller being arranged to operate in either a sleep mode or an active mode when said device is switched on, wherein said microcontroller is arranged and configured intermittently to enter said active mode from said sleep mode, test the storage device voltage and provide an indication if said storage device voltage is determined to be less than a predetermined level, and subsequently return to said sleep mode.
In one exemplary embodiment, the device may comprise a portable light source comprising a handle and a light emitting diode, said power storage element being connected to said light emitting diode, wherein said electricity generating means is mounted in or on said handle for supplying power to said power storage element.
The electricity generating means may comprise a Faraday generator, or other generator such as kinetic, piezo, solar cell, turbine, etc. The power storage element may comprise, for example, a battery, capacitor or fuel cell.
Beneficially, the control circuit comprises a current limiter for limiting the current supplied from said power storage element such that it maintains a substantially constant voltage output from said power storage device until the power storage element is substantially fully exhausted.
In the case where the device is a portable light source, this may be a torch, light source for medical applications or procedures, an emergency beacon, etc. However, the potential range of applications includes devices such as wrist watches, mobile phones, handheld or desk top computers, etc and the present invention is not necessarily intended to be limited in this regard, indeed, the present invention may be suitable for any electronic device that requires a high efficiency power generator, storage device and regulated power supply.
Also in accordance with the present invention, there is provided a control circuit for a portable light source device comprising a handle, a light emitting diode, a power storage element connected to said light emitting diode, and an electricity generating means mounted in said handle for supplying power to said storage element, said light emitting diode being rated at a voltage close to the voltage of said storage element when it is substantially fully exhausted, said circuit further comprising a current limiter between said storage element and said light emitting diode for limiting the current supplied to said light emitting diode from said storage element such that said light emitting diode operates at a substantially constant brightness until the voltage of said storage element is substantially fully exhausted.
The invention extends to a portable light source device comprising a handle, a light emitting diode, a power storage element connected to said light emitting diode, an electricity generating means mounted in said handle for supplying power to said storage element, and a control circuit as defined above.
In one exemplary embodiment, a watchdog timeout function is provided which causes said microcontroller to periodically enter said active mode. Preferably, means for switching said device on is provided, wherein actuation of said means causes said microcontroller to power up, enter said active mode and test said storage device voltage. Preferably, the microcontroller is arranged and configured to provide an indication if said storage device voltage is determined to be above said predetermined level. The indication provided to indicate the voltage level of said storage device is preferably provided by causing said light emitting diode to flash off and then on again one or more times. In one exemplary embodiment, the indication for indicating that the voltage level of said storage device is below said predetermined level is provided by causing said light emitting diode to intermittently flash off and then on again repeatedly. In this case, the “off” period is initially very short, and the light source is “on” for the majority of the time, so that the user is given a visible warning of low voltage level, but is still able to use the device as an effective light source. As the voltage level continues to fall, the duration of the “off” period steadily increases and the duration of the “on” period decreases. Thus, in practice, the light flashes off just for a moment, then stays on for, say, 5 seconds, then flashes off just for a moment and so in, the reason being that when the “low” warning is being given, the device can still continue to be effectively used as a light source because it is on for the majority of any “flash” cycle of this low-battery warning mode. The indication for indicating that the voltage level of said storage device is above said predetermined level is provided by causing said light emitting diode to flash off and then on again a number of times (e.g. 5) in quick succession.
Preferably the light emitting diode is supplied directly by the battery via means for switching said device on and off.
The microcontroller may determine the voltage level of said storage device by means of signal received from a high resistance potential divider. The sink of the light emitting diode is preferably via the microcontroller so that it can be flashed off and on at intervals as required.
The Faraday generator beneficially supplies power to the storage device (e.g. battery) via a bridge rectification or similar rectification (AC to DC conversion) device.
These and other aspects of the present invention will be apparent from, and elucidated with reference to, the embodiments described herein.
Embodiments of the present invention will now be described by way of examples only and with reference to the accompanying drawings.
Thus, the present invention provides a portable light source which is powered by utilising a Faraday generator. A charge storage element, such as a battery or capacitor, stores the charge generated by the Faraday generator and supplies the stored power to an LED. A control circuit is provided to ensure the provision of substantially constant intensity light and provide an indication of the charge status of the charge storage element.
Referring to
Referring to
The bridge rectifier 5 acts as an AC/DC converter for the Faraday generator 2,3. The resulting current directly charges the battery 6. Referring additionally to
Referring back to
As shown, the LED 4 uses the unregulated supply so that it maximises the available voltage. A current regulator function provided by the microcontroller operation ensures that the unit is being run at the optimum current, so a slight variation in voltage as a result of the fact that the LED 4 uses the unregulated supply will not have a perceptible effect on the light output. Finally, the switched supply also feeds the low dropout voltage regulator 30. The reason for this is that the microcontroller 20 is arranged to use an internal reference in proportion to its supply voltage to determine battery health. Obviously, if the battery supply were to be used to feed the voltage regulator, then the A/D reference would move in proportion to it and therefore always give the same result.
The microcontroller software is illustrated in the form of a flow chart, as shown in
If the switch 17 is pressed again (116), the unit is switched off (118).
In summary, therefore, the microcontroller 20 is powered up in response to the on/off switch being pressed, performs a battery monitoring task and is then put in a sleep mode as soon as it has undertaken the battery monitoring task, in order to conserve power. It will come out of this sleep condition in response to a periodic watchdog wakeup event, check the battery health and then return to the sleep mode whilst the unit is powered on. The microcontroller 20 will also come out of this sleep condition if the on/off switch is pressed again. However, in this case, the intent must be to switch the unit off and the microcontroller facilitates this by clearing the reset registers, turning the LED off and then decoupling the power supply. A representative state diagram is given in
The choice of LED for an exemplary embodiment of the present invention is significant. In a preferred embodiment, if the battery is rated at just over 4 volts, then a particularly suitable LED would be rated at around 3.1 volts (whereas typical LEDs tend to be rated at around 4 volts). Such an LED exists which operates at a high brightness but relatively low voltage (compared with typical LEDs). The battery will be almost completely exhausted before its voltage drops below 3.1 volts (if it is rated at just over 4 volts) which, in practice, means that via a current limiter to protect the LED when the battery is fully charged, the LED can be operated continuously at full brightness until the battery is almost fully exhausted. This is a significant advantage relative to known portable light sources of this type, which tend to gradually dim over time. Thus, even when the warning flashes start to occur, indicating that the battery is starting to run low and the unit needs to be shaken to charge the battery up, the unit is still outputting light at substantially the full brightness of the LED.
It will be appreciated that the present invention is suitable for many different types of portable light source applications, including those suitable for medical procedures, more general torch applications. The ability to program the microcontroller as required also means that the invention could be used for flashing emergency beacon type devices as well. Other applications will be apparent to a person skilled in the art, and the invention is not necessarily intended to be limited in this regard.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0715332.3 | Aug 2007 | GB | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/GB08/02685 | 8/6/2008 | WO | 00 | 6/20/2011 |
