FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
PROVISIONAL SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
Method and Circuitry for Dimming of LED Streetlights
APPLICANTS
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli,
Mumbai 400 030, Maharashtra, India, an Indian Company
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to method and circuitry for dimming of street lights. Particularly, the present invention relates to a circuit and method for generating dimming control voltage from a power supply line for dimming lights. The invention relates to a method of generating dimming control voltage derived from amplitude of power supply line. It also discloses an efficient and low cost circuit which can be used for 230 V AC as well as 115V AC power supply line voltages.
BACKGROUND OF THE INVENTION
There are several light sources which have been used in electric street lights. Based on the light source, the main types of street lights are Incandescent, Fluorescent, Low Pressure Sodium, High Intensity Discharge (HID), Induction and Light Emitting Diode (LED) lamps. For some applications of street lights dimming is done to save energy with the help of external systems during late night or during no traffic situations. In such applications sometimes dimmable electronic ballast or dimmers are used instead of conventional magnetic type of ballasts, which are housed inside the street lights for dimming the lamps.
There exist dimming and automation systems for street lights with HID, FTL lamps operating with conventional magnetic ballast; which will dim lams by controlling voltage fed to them. For LED and Induction lamps typically electronic ballast are used for normal operation and may have option for dimming with the aid of external 1-10V control voltage etc. Typically in existing practice, most dimmable electronic drivers operate on universal voltage range i.e. 100 to 260 V AC. In such cases conventional voltage bases dimming won't work and some provision is required to generate the control single (1-10V) to do

dimming. One general approach could be to have additional cable to carry 1-10V signal from control panel to each street light. Most of the times the cables are buried underground for protection as shown in the Fig. 1.
US 20120062128 discloses a power supply to an LED-based street or area light is operated to provide a dimming control signal, which is in turn processed by a circuit to produce 0-10 V DC, pulse width modulated (PWM) signals, or any other suitable signal that can variably control LEDs within the light. The on/off power interruptions could be provided, for example, from a photoelectric control, a timer circuit, or a pre-programmed or manually controlled timer/contactor. The signal to the on/off device could also or instead be initiated by an RF or power line carrier signal to cause the power interruptions.
US 6356027 discloses a 0-10V dimming interface protection circuit generating an indication that line voltage is applied across first and second leads of the dimming interface controlling light output by a lamp, includes a first device for limiting current serially connected between a line voltage source and the first lead of the dimming interface, a second device connected across the first and second leads for detecting application of line voltage to the dimming interface and for generating a control signal, and a third device for switching, operated in response to the control signal, for causing an increase in resistance of the first device to thereby limit current to the dimmer interface and limit light output by the lamp. According to one aspect of the invention, the protection circuit also includes a fourth device for preventing spurious operation of the second device.

Figure 1 shows an existing system of automatic dimming LED street lights. The existing system has street lights (102), a panel (108), a power supply line (104) and a dimming control signal (106). The street lights (102) are connected with power supply line (230V AC) and also dimming control signal (1-10V DC). The power supply line or cable (104) is placed below the ground level (110). The power supply line (104) and the dimming control signal (106) are connected to the panel (108). The panel (108) comprises automation systems, which generate 1-10V DC dimming control signal (106). The purpose of the automation system is to turn on/off the lights automatically. When there is no traffic, the automation system automatically dims the lights. In this arrangement, there is a need of one separate additional cable carrying 1-10V DC dimming control signal (106). Maintaining the additional cable for controlling dimming of lights is expensive, in retrofit cases this will be tedious job to lay down as additional cable.
One approach is to dim the LED streetlights is that a controller is kept in each street lights and communicates with the data center for ON-OFF and dimming signals. Other approach is to dim using control signals communicated with wires, wherein all the street lights are fitted with dimmable drivers and the dimming control signal is communicated using wires to the street lights.
The disadvantages of the existing practice is that dimming the streetlights is expensive due to the wireless communication node and then maintenance of the wireless system considering the obstacles and operation during rains and thunder storm. Further, an additional control cable needs to be laid is expensive and fault in the control cable leads to the entire system failure.

Thus, there has been persistent need to overcome the problems of the existing technology.
SUMMARY OF THE INVENTION
The present invention also provides a circuit for generating dimming control voltage from a power supply line for dimming lights, said circuit comprising: a connector one operatively connected to a power supply line so as to receive a power supply voltage from said power supply line, wherein one end of said connector one is serially connected to one end of a zener diode so as to allow said power supply voltage when said power supply voltage is equal or more than a threshold voltage; wherein other end of said zener diode is serially connected to one end of a stepdown transformer so as to reduce said power supply voltage to proportional dimming voltage; wherein other end of said stepdown transformer is serially connected to one end of a rectifier so as to convert said dimming voltage to an equivalent DC dimming voltage; wherein other end of said rectifier is serially connected to one end of a shunt regulator so as to limit said DC dimming voltage to a predetermined DC dimming voltage; wherein other end of said shunt regulator is serially connected to one end of a connector two so as to receive said predetermined DC dimming voltage; wherein other end of said connector two is operatively connected to one end of a dimmable electronic driver so as to receive said predetermined DC dimming voltage; wherein other end of said dimmable electronic driver is operatively connected to at least one lamp.
The present invention also provides a method for generating dimming control voltage from a power supply line for dimming lights, said process comprising: receiving a power supply voltage from a power supply line by a connector one; allowing said power supply voltage to a stepdown tranformer by using at least one zener diode when said power

supply voltage is equal and/or more than a threshold voltage; generating a dimming voltage proportional to said power supply voltage by reducing said power supply voltage using said stepdown transformer; converting said dimming voltage to an equivalent DC dimming voltage by a rectifier; limiting said DC dimming voltage to a predetermined DC dimming voltage by a shunt regulator, when said DC dimming voltage is more than said predetermined DC dimming voltage ; and providing said predetermined DC dimming voltage to a connector two.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and advantages of the various embodiments of the invention, and the manner of attending them, will become apparent and better understood by reference to the accompanying drawings, wherein:
Fig. 1 illustrates a schematic diagram of an existing system of automatic dimming LED
street lights;
Fig. 2 illustrates a schematic diagram for generating dimming control voltage from a
power supply line for dimming lights; and
Fig. 3 illustrates a circuit diagram for generating dimming control voltage from a power
supply line for dimming lights. The circuit is power through sensing power supply line
only; no special power supply is required for functioning of the circuit.
DETAILED DESCRIPTION OF THE ACCOMAPANYING DRAWINGS
Figure 2 shows a schematic diagram for generating dimming control voltage from a power supply line for dimming lights. It comprises a power supply line (202), a dimming

module (204), a connector one Jl, a connector two J2, 1-10V DC dimming control voltage (206). a dimmable electronic driver (208) and at least one lamp (210). One end of the connector one Jl is operatively connected to a power supply line (202). The other end of the connector one Jl is connected to the dimming module (204). One end of the connector two J2 is connected to the dimming module (204). The other end of the connector two J2 carries a 1-10V DC dimming control voltage (206), which is used as an input to a dimmable electronic driver (208). The dimmable electronic dimmer is kept in the street light (210) to control dimming of the light.
Figure 3 shows a circuit for generating dimming control voltage from a power supply line for dimming lights. One end of the connector one J 3 is connected to the power supply line of the street light (which is not shown in the figure 3) so as to sense the power through Jl from the power supply line. The other end of the connector one Jl (302) is serially connected to one end of a zener diode (304) so as to allow said power supply voltage when said power supply voltage is equal or more than a threshold voltage i.e. 160V AC. The bi-directional zener diodes Dl and D2 (304) are used to block supply voltage till the threshold voltage is reached. The other end of said zener diode is serially connected to a stepdown transformer T (306) so as to reduce said power supply voltage to proportional dimming voltage. The stepdown transformer (306) provides stepping down of the high power line voltage to suitable proportional lower dimming voltage. The other end of said stepdown transformer (306) is serially connected to one end of a rectifier D3 (308) so as to convert said dimming voltage to an equivalent DC dimming voltage. The other end of said rectifier is serially connected to one end of a shunt regulator (R1-D4) (310) so as to limit said DC dimming voltage to a predetermined DC dimming voltage i.e. 10V DC. The

operation of conversion of input power supply voltage to dimming output voltage is
shown in table.
Table:

Power supply input voltage Dimming output voltage
< 160V AC OVDC
> 160V AC to < 230V AC MOV DC
> 230V AC 10VDC
The table shows that if the input power supply voltage is less than 160V AC, then the output dimming voltage is OVDC. If the input power supply voltage is between 160V AC and 230V AC, then the corresponding output dimming voltage is 1-10V DC. If the input power supply voltage is greater than 230V AC, then the output dimming voltage is 10V DC.
The other end of said shunt regulator (310) is serially connected to one end of a connector two J2 so as to receive said predetermined DC dimming voltage i.e. 10V DC. The circuit further comprises a capacitor CI, which is serially connected between said zener diode (304) and said stepdown transformer (306) so as to reduce noises on power supply line. The circuit also comprises an R-C filter, which is serially connected between said rectifier and said shunt regulator so as to reduce ripples on DC dimming voltage.
According to one aspect of the invention there is provided a process for generating dimming control voltage from a power supply line for dimming lights. The process comprises that sensing a power supply voltage from a power supply line by a connector one J1 (302), allowing the power supply voltage to a stepdown tranformer (306) by using

at least one zener diode (304) when said power supply voltage is equal and/or more than a threshold voltage i.e. 160 V AC, generating a dimming voltage proportional to said power supply voltage by reducing said power supply voltage using said stepdown transformer (306), converting said dimming voltage to an equivalent DC dimming voltage by a rectifier (308), limiting said DC dimming voltage to a predetermined DC dimming voltage i.e. 10V DC by a shunt regulator (310) when said DC dimming voltage is more than said predetermined DC dimming voltage, and then providing said predetermined DC dimming voltage to a connector two J2. The process further provides that reducing noises on power supply line by means of a capacitor and also reducing ripples on DC dimming voltage by means of an R-C filter.
Thus, the method and circuitry described by the invention saves extra dimming cable cost, improves reliability of the circuit and no additional power supply is required for functioning; working power supply is derived from the sensing line voltage only.
Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiment, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the invention as defined.

We claim:
1. A circuit for generating dimming control voltage from a power supply line for
dimming lights, said circuit comprising:
a connector one operatively connected to a power supply line so as to receive a power supply voltage from said power supply line, wherein one end of said connector one is serially connected to one end of a zener diode so as to allow said power supply voltage when said power supply voltage is equal or more than a threshold voltage; wherein other end of said zener diode is serially connected to one end of a stepdown transformer so as to reduce said power supply voltage to proportional dimming voltage; wherein other end of said stepdown transformer is serially connected to one end of a rectifier so as to convert said dimming voltage to an equivalent DC dimming voltage: wherein other end of said rectifier is serially connected to one end of a shunt regulator so as to limit said DC dimming voltage to a predetermined DC dimming voltage; wherein other end of said shunt regulator is serially connected to one end of a connector two so as to receive said predetermined DC dimming voltage; wherein other end of said connector two is operatively connected to one end of a dimmable electronic driver so as to receive said predetermined DC dimming voltage; wherein other end of said dimmable electronic driver is operatively connected to at least one lamp.
2. The circuit as claimed in claim 1, comprising a capacitor is serially connected between
said zener diode and said stepdown transformer so as to reduce noises on power
supply line.

3. The circuit as claimed in claim 1, comprising an R-C filter is serially connected between said rectifier and said shunt regulator so as to reduce ripples on DC dimming voltage.
4. The circuit as claimed in claim 1, wherein said threshold voltage is 160V AC.
5. The circuit as claimed in claim 1, wherein said predetermined DC dimming voltage is 10VDC.
6. The circuit as claimed in claim 1, wherein generating the dimming voltage IV to 10V DC is proportional to the power supply voltage 160V to 230V AC.
7. The circuit as claimed in claim 1, wherein said zener diode is a bi-directional zener diode.
8. The circuit as claimed in claim 1, wherein said lamp is a high intensity discharge lamp or light emitting diode lamp or Induction or FTL (Fluorescent Tube Light) or CFL or a halogen lamp.
9. A method for generating dimming control voltage from a power supply line for dimming lights, said process comprising:
receiving a power supply voltage from a power supply line by a connector one; allowing said power supply voltage to a step-down transformer by using at least one zener diode when said power supply voltage is equal and/or more than a threshold voltage;

generating a dimming voltage proportional to said power supply voltage by reducing
said power supply voltage using said step-down transformer;
converting said dimming voltage to an equivalent DC dimming voltage by a rectifier;
limiting said DC dimming voltage to a predetermined DC dimming voltage by a shunt
regulator, when said DC dimming voltage is more than said predetermined DC
dimming voltage; and
providing said predetermined DC dimming voltage to a connector two.
10. The method as claimed in claim 9, comprising reducing noises on power supply line by means of a capacitor.
11. The method as claimed in claim 9, comprising reducing ripples on DC dimming voltage by means of an R-C filter.
12. The method as claimed in claim 9, wherein said threshold voltage is 160V AC.
13. The method as claimed in claim 9, wherein said predetermined DC dimming voltage is 10VDC.
14. The process as claimed in claim 9, wherein generating the dimming voltage IV to 10V DC is proportional to the power supply voltage 160V to 230V AC.