FIELD OF INVENTION:
The invention generally relates to a cost effective solution for using green
power for lighting purpose of a building, where grid power exists and vice versa.
It particularly relates to a modular lighting system with provisions of adding
need based Solar Photo Voltaic (SPV) power for lighting purpose of a
building/establishment at desired location only, through introduction of LED lamp
based lighting. It also provides a solution for SPV based system where grid power is
not available, but is likely to be available in future which would render the DC
operated LED lamps redundant. The invented system together with invented dual
voltage LED lamps offers a versatile & flexible solution towards interchangeability of
grid power & green power in a user friendly manner.
BACKGROUND;
1. Compact Fluorescent Lamps are fast replacing incandescent lamps for saving
power & cutting cost of energy. With the price of LED lamps coming down there are
definite indication that CFL will be replaced by LED lamps in near future because:
• LED lamps have long life - approximately 50,000 hrs as compared to
5000 hrs for CFL.
• A 10 watt LED lamp gives light (in lumens) approximately equal to the
light given by 22 watt CFL, thus saving approx. 54% power.
• LED lamps are much more shock and vibration resistant than their CFL
counterparts.
• During operation, LED lamps don't attract bugs as compared to CFL.
• LED lamps are dimmable while CFLs are generally not.
LED lamps working on AC mains (230V, 50Hz) or on a battery (10V-15V) are readily
available. However, the usage is totally ad hoc and is lacking system approach as
discussed hereunder.
Generally 230V, 50Hz Mains operated LED lamps are available in the market; each
lamp having its own SMPS. There is no intensity control or battery back up provided.
A common UPS for the entire installation, delivering 230V, 50Hz AC, if already
installed, is used as emergency back up.
In case of SPV based systems, there are two types available in the market. One type
of system uses an individual SPV panel for charging the individual battery and the
battery in turn lighting the CFL or LED lamp ( as in solar lanterns-Fig. 1). This system
is used for emergency power especially in places where electric supply is intermittent
or unreliable. As is evident, solar power is wasted in this type of system because the
battery if fully charged can no longer be charged any further; this will normally
happen if the lantern is used only intermittently.
As there is also a main power conversion stage rated for two times the power in this
system (the main controller is to be designed for twice the rated power as explained
earlier), it is less efficient. Generally intensity control for the lamps is absent.
Moreover, as the battery is accommodated inside the lamp, this system is not good for
general lighting.
The other type of system is depicted in Fig.2 wherein a PV panel charges a common
battery which in turn supplies power to all the lamps through individual controllers.
The drawbacks of prior art systems as per Fig.2 are similar to the solar lantern system
described above. This system is meant for remote areas where grid power is not
available. The lamps are suitable for working with DC voltage only. Hence they
become redundant when grid power becomes available in that area.
To conserve power, usage of LED lamps with SPV or even with AC mains is an
attractive proposition. In future cost of SPV panels as well as that of LEDs is likely to
come down drastically due to economies of scale and invention of new materials and
processes. Moreover, various incentives those are likely to be offered like encashment
of carbon credits (promoted by the U.N) will encourage usage of green power even
when normal grid power is available. In fact, recent reports suggest that LED is the
only technology that currently meets the Energy Star specification for light strings.
As mentioned earlier, presently LED based lighting products are used on ad hoc basis,
which is clear from the following scenarios existing today:

• AC Mains operated LED lamps
AC Mains operated LED lamps are presently used in buildings having grid
power (reliable as well as intermittent like in villages). For such buildings, add
on SPV is possible but a battery powered inverter is to be provided for whole
building or else total wiring has to be changed or duplicated for introducing
SPV/Battery backed up LED lamps only at few locations, which is not practical.
Generally, customers will prefer to add SPV in a phased manner as they will not
want to spend too much in the beginning itself and is likely to install SPV only
for those lights where it is essential and pays back fast.
• SPV based DC operated LED lamps
SPV based DC operated LED lamps are used in remote places where grid power
is not available and SPV finds its rightful place. But if and when grid power
comes, the costly DC operated LED lamps will become redundant much before
their end of normal operational life (life expectancy: 50,000 hrs). With a new
dual voltage LED lamp that has been invented, the invented solution takes care
that these lamps do not become redundant.
It is also seen that due to the doubly rated Switch Mode Power Supply (SMPS) based
charger for battery charging - as it has to handle the power of LED lamps through
battery only, present day SPV based systems waste a lot of energy. It is claimed that
if a system is designed as per this invention, the rating of the battery charging SMPS
can be reduced to almost half thus reducing over all losses. It is also claimed that the
system's modular design with a desired sectionalized battery charging and back up will
enable introduction of SPV in the existing buildings at the desired locations without
major modifications in the existing wiring.
The various attractive features of this system will no doubt be an added incentive to
people in creating green lighted houses/offices all over the world.

OBJECT OF THE INVENTION:
1. One of the major object of the invention is to devise an LED based
efficient lighting system which can work on grid power or SPV power or
with both in an integrated manner. The customer should be able to add
SPV at the desired sections only in the existing AC mains operated
building in a phased manner without resorting to major changes in the
existing wiring. Similarly, the existing or newly installed SPV based
system should be designed to work without wasting the costly LED
lamps, when grid power becomes available at the installation site in
future.
2. Another object of the invention is to use a dimmable dual supply LED
lamp so that it can work in all the conditions specified above. The
design and features of this lamp are covered under a different IPR.
3. Still another object of the invention is known to utilize SPV power to the
maximum possible extent.
4. Yet another object of the invention is Conservation of power through
intensity control and automatic diversion of saved power to the battery
of the same module or to other modules in case battery is fully charged.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Fig.l Solar lantern with Individual SPV Panel charging Individual battery in
turn lighting CFL or LED lamp.
Fig.2 PV panel charging a common battery which is turn supplies power to all
lamp through Individual Controller.
Fig.3 Depicts the invented system.
Fig.4 Battery supplies power through Schottky diode connected across
MOSFET to reduce power loss in diode of the MOSFET.

DESCRIPTION:
The invention will now be described in an exemplary embodiment as depicted in the
accompanying drawing. There can however be other embodiments of the same
invention, all of which are deemed covered by this description.
Fig.3 depicts the invented system - wherein a module (17/18) is designed
considering a tiny part of a building as a unit. There can be number of modules of
different ratings in the same building. There are basically four elements in a module:
1) Battery Charging SMPS (02)
2) LED Source SMPS (03)
3) DC Common Source (optional) (12)
4) Dual Supply LED Lamp (01)
The SPV can be provided in the beginning itself or can be added later on.
There can be a common SPV as depicted or each module can have its own SPV
(15/16). However, having a common SPV is more advantageous.
In case the SPV is not yet installed, the dual supply LED lamps will get primary power
(GP) (230V, 50HZ, A.C) from the Mains. If grid power is not available for prolonged
periods, AC power can be fed from a DG set.
If SPV is installed already, the grid power can also be connected later on (when
available) to the dual supply lamp so that when there is no sun and the battery is in a
fully discharged condition, automatic transfer to grid power takes place and the lamp
continues to work.
A brief description of the systems as depicted in Fig.3 is given below:
The SPV panels (15/16) are connected to the system through the Schottky diodes D1,
D2,... DN. This takes care of the inherent imbalance among the panels PV1, PV2,...
PVN (w.r.t. power supply capability) and doesn't allow any power backflow from one
panel to another. The diodes D5 and D7 (8) prevent any modules common battery
from feeding power to another module/another battery; it can supply power to only
the lamps connected to the corresponding module. It is evident from the figure that
two stage power conversion is absent in this system; battery charging and supply to
the lamps are in parallel paths. If needed, the DC Common Source (SMPS) (12) can
be activated depending on the battery voltage.

The Dual Voltage LED Lamps Lamp 1, Lamp 2... Lamp n (01) each has their source
terminals connected to the LED Source SMPS as well as a suitable AC source. If the
output voltage from the LED Sourced SMPS falls below a set value the lamps
automatically changeover to the AC supply. They revert back to the SMPS output
when it rises above the set value.
Salient features of the system:-
1. Total summed up power of a module is calculated considering the
illumination required and battery capacity is calculated based on back up
time required for dusk/night hours.
2. There is a common battery (11) for each module - with a charger having
temperature compensated maximum power point tracking feature to enable
maximum utilization of PV power.
3. Each lamp of a module gets connected to the PV panel/SMPS via the
controller that also has a maximum power point tracking (MPPT) feature.
Moreover, it is ensured that the LEDs in a particular module can not draw
power from the battery of other modules and can draw power from the
battery corresponding to its own module only when battery mode gets
selected. The circuit is configured in such a way that the LED lamp(s) will
have priority of tapping solar power over the battery.
4. The system will change over automatically to battery mode in case
sufficient sun light is not there. Battery mode can be forced manually also.
5. The LED lamps can also be run without switching on the AC power to the
lamps to minimize the losses in the AC Switch Mode supply inside the lamp.
As AC should be switched on before the battery voltage falls below desired
limits following indications have been provided:
(a) Indication of battery voltage greater than 12.5V (settable)
(b) Indication of battery voltage greater than 10.2V (settable)
(c) An audible alarm using a buzzer if battery voltage falls below 10.5V
(settable) to draw attention for-switching on AC.

6. The circuit is so designed that even in battery mode in cloudy season
residual power from PV is tapped as far as possible to light up the LEDs and
is not allowed to go waste.
7. Intensity of the LED lamps can be individually controlled, enabling the
customer to divert the remaining power to its battery or to other
lamps/other batteries.
8. Statistically, there is a low probability of full loading of all the modules at the
same point of time. Hence the circuit has been so designed that in PV
mode the unused power gets diverted to other modules automatically,
making the overall system more efficient. Thus having a common SPV
source will enable such diversion of unused power which won't be possible
if each module had its own SPV installed.
Special features of the Battery Charger SMPS
Calculation of ratings of the controller components is based on the number of LED
lamps to be connected to that particular module and the back up time period and the
amount of statistical average usage of all the modules taken together. Amp-hr
capacity of the battery is also decided based on these factors. Either one or a number
of modules can be connected to a PV panel, each having identical or different ratings
depending on the requirement.
The switch mode controller for battery charging has the following special features:
1. Temperature compensated MPPT feature with priority of LED lamps over
battery.
2. Because of the Schottky diodes D5 and D7 (08) (see Fig.3), a battery
assigned to a particular module can not feed power to other modules.
However it can feed power to all the LED lamps connected to that
module through the corresponding LED Source SMPS. Thus each module
has its own battery back up.
3. Each LED lamp in a module has priority over its common battery in
tapping solar power.

4. Temperature dependent boost charging - of the battery to ensure its
optimum charging.
5. In excess power conditions, which can occur with the MPPT feature,
boost charge current limit becomes effective to protect both the battery
and the controller. .
6. The battery can be changed online (in-situ) after manually selecting the
charge control POT position corresponding to zero charging current.
Special features of the LED Source SMPS
The system described here is for a 12V battery system and PV panel having
maximum power point tracking voltage around 16V (depending on the specifications
of the PV module). However this invention is applicable for other battery voltages
also, only component ratings need to be changed. The underlying principles of
operation remain the same as described in this invention, irrespective of the battery
voltage.
In PV mode, the controller changes the LED lamp intensity based on the maximum
power point tracking (MPPT) feature. Hence intensity of all the lamps connected to
the common LED Source SMPS (03) may change simultaneously. Output voltage of
the SMPS is not allowed to go beyond a set limit in case excess power is available;
LED lamps can not draw more than their rated power. When there is no sun, battery
mode gets automatically selected, thus maintaining constant output voltage. If
battery discharges to an extent that it is no longer possible to maintain constant
output voltage, the dual AC source connected to the LED lamp takes over
automatically, stopping further discharge of the battery.
The LED Source SMPS is current limited to avoid burn out in case more than specified
number of lamps is connected to it. The terminal voltage of LED lamps is maintained
constant at 11.3V (settable) according to the particular LED lamp design, till the rated
load current limit is exceeded.
Both the battery charging SMPS (02) and LED Source SMPS (03) are housed in a
common enclosure. The control console provided in the front has the following
controls:
1. Latch type pushbutton or ON/OFF switch for forced Battery mode
selection.
2. Latch type pushbutton or ON/OFF switch for forced Common DC Source
selection.
3. A low power LED indicator for source voltage more than 10.2V-which
gives ambient lighting also so that console can be located in dark.
4. Additional low power LED indicator for source voltage of more than
12.5V.
5. LED indicator for system on battery.
6. Potentiometer to commonly control the lamp(s) intensity. Thus the user
can brighten/darken the room by operating the common intensity
control pot. This is over and above the intensity control provided on
each of the dual supply LED lamp(s). However, in the rare case of the
user trying to dim all the lamps simultaneously, the user has to
disconnect the AC source from the lamp(s) before operating the
common intensity controller. This will prevent unnecessary switchover to
AC when O/P voltage of the SNIPS goes down due to varying of the pot.
Special feature of the Common DC Source (Optional)
The Common DC Source (12) can be provided either from the Mains (or DG set)
driven SMPS, or Wind Generator Dynamo or external battery (e.g. the automobile
battery with engine running).
The Mains driven SMPS is designed to output a voltage equal to the MPPT voltage of
SPV, i.e. approx. 16V for a 12V system. The SMPS is designed to maintain constant
output voltage irrespective of input supply fluctuations. The SMPS is designed to
accept input from a DG set also. If PV output is not sufficient, the system will
switchover to battery mode automatically Moreover, if the battery voltage has
dropped below 10.8V to 10.5V (settable), the SMPS will switch on automatically. It
will switch off only when the battery has been fully charged even if solar power
becomes sufficient again.
In case the optional DC source is not provided, when the battery voltage falls below a
level such that it is not possible to maintain a constant output voltage of the LED
Source SMPS, the lamp starts drawing power from the AC source automatically.
Special features of the Dual Supply LED Lamp
The Dual Supply LED Lamp is designed to work either on the DC output of the LED
Source SMPS or an AC source. The AC source can either be the Mains or a DG set.
The controller in the LED lamp ensures automatic transfer to the AC source in case
input voltage from the LED Source SMPS falls below a set value. It reverts back
automatically once the DC source voltage rises again above the set value. Intensity of
the lamp can be varied by using a POT.
WE CLAIM:
1. A modular lighting system with provision for automatic switch over from grid
power (A.C) to solar photovoltaic power (SPV) and vice versa, said system
comprising of:
A plurality of modules for lighting LED lamps (01) from grid power (GP) or solar
photovoltaic power (SPV) and said modules comprising of a switched mode
power supply (SMPS) (02) for charging a battery exclusively assigned for the
module and another SMPS (03) for powering LED lamp of the said module; a
battery backup (11), characterized in that the modules can work with A.C.
Source or SPV source or battery mode or common D.C source if available, in an
integrated manner automatically selecting the required mode according to
available ground condition, having further provision for priority order of selection
for tapping solar power over the battery back up.
2. A modular system as claimed in claim 1, wherein the system can be deployed at
a desired location in existing building which has grid power without major
modifications in the existing wiring of this building with provision for addition of
SPV in future.
3. A modular system as claimed in claim 1, wherein the system can be initially
powered from SPV with a battery as back up and can also function with AC
whenever available.
4. A modular system as claimed in claim 1, wherein each of the said module has
provision for connecting a common external DC Source (12) which is required to
take care of prolonged poor sunlight conditions and non-availability of AC power;
the source being an SMPS fed from a DG Set or a Wind Generator such that the
output of the SMPS corresponds to the MPPT voltage of SPV so that even the
residual SPV power can be tapped under those conditions.
5. A modular system as claimed in claim 1, wherein automatic changeover takes
place from SPV mode to battery mode when sunlight is insufficient, and if the
battery is in a condition of deep discharge, the system automatically switches
over to an external common D.C. source, (if existing) or if A.C power is
connected to the LED lamp(s), deep discharge of the battery will be avoided as
the lamp will start drawing power from the AC Mains when the battery fails to
maintain the set output terminal voltage due to discharge.
6. A modular system as claimed in claim 1, wherein the SMPS (02) is deployed for
temperature compensated charging of the battery; the rating of the SMPS (02) is
reduced by half thereby reducing the overall losses due to the provision of a
parallel path for powering LED lamps through SMPS (03) directly from the PV
source.
7. A modular system as claimed in claim 1 wherein SMPS (02 & 03) have
temperature compensated maximum power point tracking (MPPT) feature with
priority to LED lamps over battery charging and the system is so designed (by
using Schottky diodes D5 and D7) (08) that the battery assigned to a particular
module cannot feed power to other modules; in excess power conditions the
current limit in SMPS (02) becomes effective to protect the battery (11) and the
SMPS (02) and in SMPS (03) to protect the SMPS (03) itself.
8. A modular system as claimed in claim 1, wherein each of the said module has a
separate SMPS (03) for powering the LED lamps; the said SMPS maintains a
constant output voltage which is not allowed to go beyond a predefined limit; in
case the output of the said SMPS falls below a set value, the dual voltage lamps
start drawing power from the AC source automatically; this feature ensures that
the power continues to be drawn from SPV instead of the AC Mains as far as
possible.
9. A modular system as claimed in claim 1 wherein the modules (17/18) are
capable of running individually for different power ratings and different battery
backup and are capable of being run from individual SPV sources (15 & 16)
which may or may not be connected with each other; in case of the SPV sources
being connected with each other, if one of the modules is not fully loaded the
excess power becomes available for other modules due to OFF condition of the
lamp(s) or intensity control; the saved power is diverted to the module's battery
or to other modules automatically, ensuring optimum utilization of solar power.
10. In battery mode the battery supplies power through the Schottky diode (13)
connected across the MOSFET (14) to reduce the power loss in the diode of the
MOSFET.
11. A modular system as claimed in claim 1 wherein the LED lamps (01) are of dual
voltage type, which can run on AC power or SPV power with priority for
utilization of SPV power over AC power.
12. The modular system as claimed in claims 1,8 and 9 wherein the said LED lamps
in a particular module have a common intensity control arrangement through a
SNIPS (03), which is in addition to the intensity control provided on each of the
dual voltage LED lamp and in the said modular system the LED lamp(s) will glow
with reduced intensity when SPV power is inadequate and if the AC power is not
connected and if the insolation continues to reduce further the battery mode
gets selected automatically, with provision that the LED lamps will continue to
glow with their rated intensity till the battery voltage is adequate.
13. The modular system as claimed in claim 1 wherein the said LED lamps can also
be run without switching on the AC power to the lamps to minimize the losses in
the AC Switch Mode supply inside the lamp; as AC should be switched on before
the battery voltage falls below desired limits following indications have been
provided:
(a) indication of battery voltage greater than 12.5V (settable)
(b) indication of battery voltage greater than 10.2V (settable)
(c) An audible alarm using a buzzer if battery voltage falls below 10.5V
(settable) to draw attention for switching on AC.
14. A modular system as claimed in claim 1, wherein the battery (11) can be
removed and also can be introduced if required in-situ by making the battery
charging current zero.
15. A modular system as claimed in claim 1 and 11, wherein the LED lamps (01) can
also work without the battery (11) and AC (GP) during day time.

This invention provides a cost effective solution for introducing LED lamp based modular lighting system in installation having grid power with provision to switch over to Solar Photovoltaic (SPV) power and vice versa. The system can be installed without major modifications in the existing wiring at desired locations only. The invented system together with the invented dual voltage LED lamps shall obviate the need for replacing single voltage LED lamps when both grid and SPV power are available.
The modular feature ensure a battery backed up module of required capacity which can work in conjunction with similar module(s) of same or different capacity sharing power from the common SPV panels so that the SPV power can be utilized optimally, while the battery back up remains confined to the particular module only. All LED lamps connected in a module are fed from a common controller which can tap power from SPV, battery, external DC source (if available) or Ac Mains according to the available ground conditions with further provision for priority of tapping solar power over AC Mains.