ANNEXUREI
COMPLETE SPECIFICATION
TITLE:
Solar Rechargeable LED Lantern

3) BACKGROUND AND OBJECTS OF THE INVENTION:
The vast rural population of India still depends on kerosene lamps for meeting their illumination needs because of the limitations of the power infrastructure in the country. These lamps, apart from being potential fire hazards, also cause eye discomfort to the users on one hand and environmental pollution on the other. Utilisation of non-conventional and renewable energy has been on the agenda of the Nation for a long time and solar energy has been a preferred choice for a country like India for obvious reasons. There have been attempts to make use of solar lamps deploying Compact Fluorescent Lights (CFLs). However, they met with limited success because of the inherent weaknesses in the CFLs and their frequent failures. The emergence of Light Emitting Diodes as highly efficient and reliable sources of illumination has opened up tremendous options in lighting solutions for both rural and urban environments.
The deployment of LEDs as light sources in conjunction with a renewable energy
source like sun light will provide sustainable and effective solutions for not only
meeting the illumination needs of the rural population but also the residents of urban
areas - in these days of frequent power cuts.
For MIC Electronics Limited
Narayana Patadugu Vice President (Operations)

4) PRIOR ART: PATENTS AND DESIGNS:
Portable light sources have found their use in many work environments, particularly in remote areas. Batteries provided energy to the light sources but with an inherent limitation - limited life of battery and replacement as and when needed, especially in remote places. Stocking extra batteries has bearing on cost, space and weight.
Solar power has been explored to recharge batteries. However the charging of the battery directly from solar power would degrade the life of the battery. Battery life is also affected if deep discharge is allowed.
The patent on Solar Rechargeable Lantern of William John Greenhoe (Sep 2001) described the advantages of solar rechargeable system but the light source considered was an incandescent bulb with a very low efficiency.
The patent proposals on Solar Rechargeable Lantern of May (Pervaiz Lodhie ef al) and June 2006 (William John Greenhoe) are essentially refinements proposed to deploy LEDs as new light sources with their inherent operational advantages.
The patent application for Solar based LED Lamp device of Sept 2006 of BHEL Kolkatta by R.K. Bhogra and others employed pulsed DC Driver for providing power to illuminate the LEDs with less current.
Also attempted in the prior art are a method to protect the battery from deep
discharge or overcharge; a method to monitor and display the charge status as
'normal' or 'low battery"; and a facility to select a High or Low illumination as desired
when the lantem is switched ON.

5) SHORTCOMINGS OBSERVED IN PRIOR ART:
Solar Rechargeable Lanterns ideally cater to the indoor or outdoor lighting requirements in remote areas. However, the following shortcomings have been noticed in the above published designs:
1. The light intensity desired is selectable between two distinct levels - high and low. A continuous variation is not available.
2. The present scheme of layout and alignment of LEDs produces regions of shadow between regions of light and hence does not produce uniform intensity in the physical space of 360 degrees around the lantern.
3. Glare element persists with associated discomfort on eye / vision.
4. The principle employed in connecting and driving LEDs is not efficient as forward voltage of LED varies with temperature and all LEDs may not be driven at same current.
5. Efficiency of the driver is less, as this does not take care of battery voltage variation.
6. DC pulsed driving has its internal problems like inability to control peak current and the limitation of number of LEDs in a string etc.
There is a need to build a Solar Rechargeable LED Lantern overcoming these limitations and with a well-laid out structure of the LED light source, which distributes light with uniform intensity in all 360 degrees around with a greater eye comfort, also allowing a digitally controlled variation in illumination level as required. It is also necessary to couple the light source with a highly efficient driver.
For MIC Electronics Limited Vice President (Operation«>

6) SUMMARY OF THE INVENTION
A Solar Rechargeable LED Lantern is disclosed having a White - LED assembly as the lighting source. A mono or multicrystalline / amorphous / thin film Solar Photo Voltaic module converts solar energy to electricity, which charges a rechargeable battery through a charging circuit. The charging circuit has protections against deep discharge and overcharging of the battery.
The specially designed architecture of LEDs in a vertical orientation generates the desired light intensity with uniform spread all around.
The custom built holographic diffuser with more than 90% efficiency eliminates the glare and provides the eyes a comfortable vision.
A digitally controlled dimming feature helps decreasing the output intensity to any desired level thereby effecting saving in energy.
The electronics ensures charge control and charge status indication as well as efficient perfomnance of the light source.

7) BRIEF DESCRIPTION OF THE DRAWINGS:
The diagrammatic representations of the Solar Rechargeable LED Lantern
included are as under:
Fig. 1 Lantern Housing
Fig. 2 LED Assembly
Fig. 3 Block Schematic
There are three units integrated in the mechanical housing - First is the light source and the optical system, second the solar-based charger and LED driver electronics and third, rechargeable power source (a battery). The SPV panel is mounted externally at an optimum angle facing the Sun.

8) DESCRIPTION OF A PREFERRED EMBODIMENT AND METHOD:
With the help of Figs 1-3, the Solar Rechargeable LED Lantern of the present invention is illustrated. The Lantern includes a housing that comprises of a bottom portion and an upper portion.
The bottom portion 7 accommodates the rechargeable power source - a battery; the electronic circuitry to control the charge levels of the battery, to drive the light source and to control the illumination level of the light source; a push button switch 5 to powder on and off the lantern and also to digitally control the illumination level of the lantern; a display system of 1 LED to indicate the 'normal charging' status of the battery, another display of 4 LEDs to indicate the capacity or charge level of the battery and a flat base 8 that enables a stable positioning of the lantern on a table top.
The upper portion 3 includes the light source, which is a set of four (square) or three (triangular) vertically mounted strips of PCBs fixed to a base plate 6; each PCB containing LEDs arranged in a column. The optical system including the holographic diffuser is then enclosed in a transparent polycarbonate shell 4, which disperses the light in all the 360 degrees around. A cap 2 at the top covers the housing. The lantern can be held by a handle 1, which can also be used as a hook to hang the lantern at a height, if desired.
The LED assembly and the surrounding construction of the diffuser 17 are shown in Fig 2. Two configurations are shown, one in the square fomi 12 and the other in the triangular shape 13. LEDs 14 are mounted in a vertical fashion with light emitting out side with angles of 100 degrees 15 and 140 degrees 16 for the square and the triangular assemblies respectively covering 360 degrees horizontally.
A socket 9 is provided to connect the solar power cable from SPV module to the lantern, which is connected to the charger circuit.
The present charge level of the battery at any point of time is displayed by means of a 4 - LED assembly 10 indicating 100%, 75%, 50% and 25% by the glow of the respective LEDs.
A DC power socket 11 is provided for connecting an extra load like a transistor radio or any other gadget.

9) OPERATION OF THE SYSTEM AND ELECTRONICS:
The functioning of tlie system is outlined in tlie block diagram in Fig.3.
Solar Panel 18 converts the incident sunlight into electrical energy, which is fed to the battery charger 19 for charging the re-chargeable power source, i.e. battery 20.
Battery provides power to drive the Light source i.e. LED 22 through a high efficiency constant current switching mode regulator 21. The constant current driving is essentially necessary to generate uniform light intensity from all LEDs. All LEDs are connected in series operating at a lesser current. This reduces losses and gives higher efficiency. This method allows unifomi current drive to all LEDs irrespective of forward voltage variations. Switched mode power supply consumes same power irrespective of the voltage variations of the battery.
The battery charger 19 has protection from over charge with the help of a cut-off circuit 23. The status of the charge level in the battery is indicated through a four LED assembly unit each LED glowing when the charge levels are maintained at 100%, 75%, 50% and 25% of the desired level respectively. When the charge level is 25%, this situation is an alarm situation and the corresponding LED indicates 'battery low'). One more LED is used to indicate normal charging of the battery. Also provided is a facility 25 to connect an additional external load of any household DC appliance with a limited current of 50mA.
The Switching mode regulator is controlled by an on off / dimming control switch 27, which enables the light system to be switched on or off. A dimming control feature is also provided for reducing the intensity to any desired level enabling the lantern to serve as either a reading lamp or a night lamp. This feature is also included in the on/off control 27. Whenever the battery reaches below a threshold charge level the LED drive circuit is disabled through a cut off circuit 26 to avoid deep discharge of the battery.
This invention thus offers an improved Solar Re-Chargeable LED Lantern where in LEDs are used as light source with two alternative LED arrangements namely square type or triangular type LED constructions, which provide equally efficient light sources with uniform light illumination with eye comfort and longer life expectancy.

10) CLAIMS:
We Claim:
1. A Solar Rechargeable LED Lantern that includes:
i) A housing
ii) A LED Light source
iii) A re-chargeable power source
iv) A solar power source
v) A control electronics
vi) An optical system
vii) Appropriate Controllers and indicators
viii) A charge level indicator for the battery and
ix) A provision in the form of a Socket for connecting a DC utility.
2. The solar lantern in claim 1 wherein the housing is similar to traditional kerosene lamps used in the Indian households.
3. The solar lantern in claim 1 wherein the LED Light source with suitable arrangement of LEDs for uniform illumination.
4. The solar lantern in claim 1 wherein the rechargeable power source is a battery or a capacitor or any similar power storage device.
5. The solar lantern in claim 1 wherein the solar power source like crystalline / amorphous / thin film photovoltaic module or similar device that converts solar energy into electrical energy.
6. The solar lantern in claim 1 wherein the control electronics for limiting the charge and discharge levels of the rechargeable power source, to drive the light source with permissible levels of current for safe driving using high efficiency switching mode techniques and improved methods of connecting LEDs, to control the illumination levels of the lantern as desired and to simultaneously optimize the utilization of the battery.
7. The solar lantern in claim 1 wherein the optical system for minimizing the glare and eye discomfort.
8. The solar lantern in claim 1 wherein the controllers regulate the usage of the lantern and the indicators display the health status of the rechargeable power source. The user interface enables the control of illmination level to the desired levels including the usage of the lantern as a night lamp.

9. The solar lantern in claim 1 wherein the charge level indicator is an assembly of 4 LEDs Indicating charge levels of 100%, 75%, 50% and 25% through each LED respectively.
10. The solar lantern in claim 1 wherein the socket provides for connecting one external normal household DC powered utility like a transistor radio.