Title of Invention	"AN IMPROVED LAMP"
Abstract	An improved lamp for flashing, blinking, illuminating or static mode using a cluster of LED's characterized by a shunt of low carrying current capacity is connected across each LED, each of said LED is connected in series parallel circuit to prevent failure of cluster of LED, a current regulator is provided for each series cluster, each of said LED has a thermal control for heat sinking to provide higher light output and improve temperature performance of LED's.

Title of Invention

"AN IMPROVED LAMP"

Abstract

An improved lamp for flashing, blinking, illuminating or static mode using a cluster of LED's characterized by a shunt of low carrying current capacity is connected across each LED, each of said LED is connected in series parallel circuit to prevent failure of cluster of LED, a current regulator is provided for each series cluster, each of said LED has a thermal control for heat sinking to provide higher light output and improve temperature performance of LED's.

Full Text	This invention relates to an improved lamp for flashing, blinking, illuminating or static mode using a cluster of LED's (Light emitting diodes) described in our earlier Patent No. 170654. BACKGROUND In our earlier patent no. 170654 lamps using cluster of LED's suffer from part or complete failure, due to open circuit failure of one LED in series path. LED's have to be used in series for optimum use of the power source. Further, lamps having cluster of LED's in series parallel circuit, partial failure of the cluster leads to deshaping of the radiating area. Further, performance of lamp is derated with temperature rise requiring reduction in drive leading to lower light output. It is the object of this invention to obviate the above drawbacks by providing- (i) a shunt of low carrying current capacity across each LED connected in series or series parallel circuit, and (ii) a thermal control means provided on the LED lead on the copper side of PCB for heat sinking to provide higher light output and improve temperature performance of LED's. To achieve the said objective, this invention provides an improved lamp for flashing, blinking, illumination or static mode using a cluster of LED's as claimed in our earlier Patent No. 170654 and is characterized in that (i) a shunt of low carrying current capacity is connected across each LED, (ii) each of said LED is connected in series parallel circuit to prevent failure of cluster of LED, (iii) a current regulator of any conventional type is provided for each series cluster, (iv) each of said LED has a thermal control for heat sinking to provide higher light output and improve temperature performance of LEDs. The invention will now be described with reference to the accompanying drawing, which is shown by way of examples. Fig. 1 shows series parallel arrangement of LED showing shunt circuit on each LED of series cluster. Fig. 2 (a), (b), (c) shows current regulators for series cluster with shunts across each LED. Fig. 3 shows the thermal control means provided on one or both of the leads of LED's for heat sinking on a substantially flat single or multisided display. Fig. 4 shows current regulator with over voltage trip circuit to ensure failure on the safe side. Referring to Figs (1) & (2), items (1), (2) & (3) show the LED's connected in series parallel to form cluster of LED's. The shunts S11,S12, S13, & S21, S22 S23 etc. are connected across each LED to prevent failure of the series cluster leading to deshaping of the radiating area and reduction of light output. In a cluster with series arrangement of LED's if any LED is to fail as open circuit then the entire cluster would fail (stop glowing). However by adding a shunt circuit/resistance (S11, S12, S13, S21, S22 & S23) across the Led, latter's open circuit failure does not lead to circuit failure as the shunt allows the current to pass. Shunt resistances (S11, S12, S13, S21, S22 & S23) can be designed to carry nominally less current when LED is in operation, say as an example LED operates at 2.2 volts & 20 mA then the shunt resistance may be kept at 270 ohms putting an additional load of 8.14 mA app. and making total circuit current to be 28.14 mA. When the LED is to fail, this would carry the higher circuit current of 28.14 mA and drop higher voltage 7.5 volts, leading to additional voltage requirement. Shunts can be suitably designed on the basis of additional voltage available. Since LED is a current driven device, a current regulator (CR) is provided within operating range of LED to maintain its normal life. It is desirable to provide separate current regulator for each series cluster as in figure, so that failure of current regulator in one cluster does not have any effect on the other clusters. A standby current regulator is also provided in the each circuit so that if the first current regulator fails, the standby current regulator will start functioning with manual or automatic switching as shown in Fig. 2c. The LED's light output is proportional to the drive current. The latter is derated with increase in ambient temperature. Conventionally, LED's are mounted PCB and the PCB copper area is increased to reduce the temperature effect. However, this does not provide adequate thermal mass, this is further reduced when LED's are placed in close proximity for higher luminous stearance. In figure 3, the LED's connected on PCB are shown and a thermal control means is provided on one of the LED lead for heat sinking to provide higher drive/light output and improve temperature performance of LED's. The temperature rise should be within the operating range of LED for the required light output and current drive. The thermal control means can be a metal mass (Ml & M2) soldered on one of the LED lead shown as an example in figure 3 or any other thermally conductive mass connected to LED lead. The thermal control means developed in this invention is metal mass soldered on one of the LED lead on the copper side of the PCB. Such increase in thermal mass increases the overdriving range of the LED's for higher light output. In other words lesser no. of LED's can be used in a cluster for getting the same light output, there by reducing the overall cost. The metal parts to both the legs of the LED's. In may not always be practical to attach such metal parts to both the legs of the LED's. In such cases it is recommended to connect it to the leg of the LED, which has lower thermal resistance to the LED chip. Normally, anode (otherwise cathode) is connected via. ductile wire whose contact/conductor life is affected by temperature variations over reducing at a higher rate for a wider range. Increase in thermal mass dampens such effects and thus improves the life of LED. Many applications require only occasional use of the lamp. With increase of thermal mass substantial overdrive is possible. Light output is proportional to the drive current, in such cases leading to higher light output at lower cost. INTERLEAVING OF LEDs Lamps using cluster of LEDs are often configured into series parallel arrangement as shown in fig. 1 & 2 to generate the desired light output with series LED voltage/current to match the operating range of the source. However, failure of the series cluster due to disconnection from the source or otherwise leads to deshaping of the radiating area. Interleaving of LEDs of different circuit clusters, with equitable placement, reduces the deshaping. We claim: 1. An improved lamp for flashing, blinking, illuminating or static mode using a cluster of LED's characterized by: i) a shunt of low carrying current capacity is connected across each LED, each of said LED is connected in series parallel circuit to prevent failure of cluster of LED, ii) a current regulator of any conventional type is provided for each series cluster, iii) each of said LED has a thermal control means for heat sinking to provide higher light output and improve temperature performance of LED's. 2. An improved lamp as claimed in claim 1 wherein thermal control means is a metal mass connected to the LED. 3. An improved lamp as claimed in claim 2 wherein the said metal mass is a copper area on the printed circuit board on which LED's are fitted. 4. An improved lamp as claimed in claim 2 wherein the said metal mass is long legs of LED's extending on the solder side of the PCB. 5. An improved lamp as claimed in claim 2 wherein the said metal mass is heat sink of metal connected to the LED 6. An improved lamp as claimed in claim 2 wherein the said metal mass is long legs of LED's in combination with the heat sink of the metal connected to the LEDs. 7. An improved lamp as claimed in claim 2 wherein the said metal mass is copper area in combination with long legs of LEDs connected to the LEDs. 8. An improved lamp as claimed in claim 1 wherein a standby current regulator is provided for each series circuit so that if one current regulator fails, the standby current regulator starts functioning for the LED's cluster in the circuit. 9. An improved lamp as claimed in claim 1 wherein the shunt carries preferably upto 40% of the LED current 10. An improved lamp for flashing, blinking, illuminating or static mode using a cluster of LED's substantially as herein described with reference to the accompanying drawings.

Full Text

This invention relates to an improved lamp for flashing, blinking, illuminating or static mode using a cluster of LED's (Light emitting diodes) described in our earlier Patent No. 170654.
BACKGROUND
In our earlier patent no. 170654 lamps using cluster of LED's suffer from part or complete failure, due to open circuit failure of one LED in series path. LED's have to be used in series for optimum use of the power source.
Further, lamps having cluster of LED's in series parallel circuit, partial failure of the cluster leads to deshaping of the radiating area.
Further, performance of lamp is derated with temperature rise requiring reduction in drive leading to lower light output.
It is the object of this invention to obviate the above drawbacks by providing-
(i) a shunt of low carrying current capacity across each LED connected in series or series parallel circuit, and
(ii) a thermal control means provided on the LED lead on the copper side of PCB for heat sinking to provide higher light output and improve temperature performance of LED's.
To achieve the said objective, this invention provides an improved lamp for flashing, blinking, illumination or static mode using a cluster of LED's as claimed in our earlier Patent No. 170654 and is characterized in that
(i) a shunt of low carrying current capacity is connected across each LED,
(ii) each of said LED is connected in series parallel circuit to prevent failure of cluster of LED,
(iii) a current regulator of any conventional type is provided for each series cluster,
(iv) each of said LED has a thermal control for heat sinking to provide higher light output and improve temperature performance of LEDs.

The invention will now be described with reference to the accompanying drawing, which is shown by way of examples.
Fig. 1 shows series parallel arrangement of LED showing shunt circuit on each LED of series cluster.
Fig. 2 (a), (b), (c) shows current regulators for series cluster with shunts across each LED.
Fig. 3 shows the thermal control means provided on one or both of the leads of LED's for heat sinking on a substantially flat single or multisided display.
Fig. 4 shows current regulator with over voltage trip circuit to ensure failure on the safe side.
Referring to Figs (1) & (2), items (1), (2) & (3) show the LED's connected in series parallel to form cluster of LED's. The shunts S11,S12, S13, & S21, S22 S23 etc. are connected across each LED to prevent failure of the series cluster leading to deshaping of the radiating area and reduction of light output.
In a cluster with series arrangement of LED's if any LED is to fail as open circuit then the entire cluster would fail (stop glowing). However by adding a shunt circuit/resistance (S11, S12, S13, S21, S22 & S23) across the Led, latter's open circuit failure does not lead to circuit failure as the shunt allows the current to pass.
Shunt resistances (S11, S12, S13, S21, S22 & S23) can be designed to carry nominally less current when LED is in operation, say as an example LED operates at 2.2 volts & 20 mA then the shunt resistance may be kept at 270 ohms putting an additional load of 8.14 mA app. and making total circuit current to be 28.14 mA. When the LED is to fail, this would carry the higher circuit current of 28.14 mA and drop higher voltage 7.5 volts, leading to additional voltage requirement. Shunts can be suitably designed on the basis of additional voltage available.
Since LED is a current driven device, a current regulator (CR) is provided within operating range of LED to maintain its normal life. It is desirable to provide separate current regulator for each series cluster as in figure, so that failure of current regulator in one cluster does not have any effect on the other clusters. A standby current regulator is also provided in the each circuit so that if the first current regulator fails, the standby current regulator will start functioning with manual or automatic switching as shown in Fig. 2c.

The LED's light output is proportional to the drive current. The latter is derated with increase in ambient temperature.
Conventionally, LED's are mounted PCB and the PCB copper area is increased to reduce the temperature effect. However, this does not provide adequate thermal mass, this is further reduced when LED's are placed in close proximity for higher luminous stearance. In figure 3, the LED's connected on PCB are shown and a thermal control means is provided on one of the LED lead for heat sinking to provide higher drive/light output and improve temperature performance of LED's. The temperature rise should be within the operating range of LED for the required light output and current drive. The thermal control means can be a metal mass (Ml & M2) soldered on one of the LED lead shown as an example in figure 3 or any other thermally conductive mass connected to LED lead.
The thermal control means developed in this invention is metal mass soldered on one of the LED lead on the copper side of the PCB. Such increase in thermal mass increases the overdriving range of the LED's for higher light output. In other words lesser no. of LED's can be used in a cluster for getting the same light output, there by reducing the overall cost. The metal parts to both the legs of the LED's. In may not always be practical to attach such metal parts to both the legs of the LED's. In such cases it is recommended to connect it to the leg of the LED, which has lower thermal resistance to the LED chip.
Normally, anode (otherwise cathode) is connected via. ductile wire whose contact/conductor life is affected by temperature variations over reducing at a higher rate for a wider range. Increase in thermal mass dampens such effects and thus improves the life of LED.
Many applications require only occasional use of the lamp. With increase of thermal mass substantial overdrive is possible. Light output is proportional to the drive current, in such cases leading to higher light output at lower cost.
INTERLEAVING OF LEDs
Lamps using cluster of LEDs are often configured into series parallel arrangement as shown in fig. 1 & 2 to generate the desired light output with series LED voltage/current to match the operating range of the source.
However, failure of the series cluster due to disconnection from the source or otherwise leads to deshaping of the radiating area. Interleaving of LEDs of different circuit clusters, with equitable placement, reduces the deshaping.

We claim:
1. An improved lamp for flashing, blinking, illuminating or static mode using
a cluster of LED's characterized by:
i) a shunt of low carrying current capacity is connected across each LED, each of said LED is connected in series parallel circuit to prevent failure of cluster of LED,
ii) a current regulator of any conventional type is provided for each series cluster,
iii) each of said LED has a thermal control means for heat sinking to provide higher light output and improve temperature performance of LED's.
2. An improved lamp as claimed in claim 1 wherein thermal control means
is a metal mass connected to the LED.
3. An improved lamp as claimed in claim 2 wherein the said metal mass is a
copper area on the printed circuit board on which LED's are fitted.
4. An improved lamp as claimed in claim 2 wherein the said metal mass is
long legs of LED's extending on the solder side of the PCB.
5. An improved lamp as claimed in claim 2 wherein the said metal mass is
heat sink of metal connected to the LED
6. An improved lamp as claimed in claim 2 wherein the said metal mass is
long legs of LED's in combination with the heat sink of the metal
connected to the LEDs.
7. An improved lamp as claimed in claim 2 wherein the said metal mass is
copper area in combination with long legs of LEDs connected to the LEDs.
8. An improved lamp as claimed in claim 1 wherein a standby current
regulator is provided for each series circuit so that if one current regulator
fails, the standby current regulator starts functioning for the LED's cluster
in the circuit.

9. An improved lamp as claimed in claim 1 wherein the shunt carries
preferably upto 40% of the LED current
10. An improved lamp for flashing, blinking, illuminating or static mode using
a cluster of LED's substantially as herein described with reference to the
accompanying drawings.

Documents:

224-del-1997-abstract.pdf

224-del-1997-claims.pdf

224-del-1997-correspondence-others.pdf

224-del-1997-correspondence-po.pdf

224-del-1997-description (complete).pdf

224-del-1997-drawings.pdf

224-del-1997-form-1.pdf

224-del-1997-form-19.pdf

224-del-1997-form-2.pdf

224-del-1997-form-3.pdf

224-del-1997-form-61.pdf

224-del-1997-gpa.pdf

224-del-1997-pa.pdf

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Patent Number

232969

Indian Patent Application Number

224/DEL/1997

PG Journal Number

13/2009

Publication Date

27-Mar-2009

Grant Date

24-Mar-2009

Date of Filing

29-Jan-1997

Name of Patentee

SANARTI INTERNATIONAL.

Applicant Address

S-158 , GREATER KAILASH, NEW DELHI - 110 048,

Inventors:

#	Inventor's Name	Inventor's Address
1	SANJEEV KHOSLA	S-158 , GREATER KAILASH, NEW DELHI - 110 048,

PCT International Classification Number

H05B 3/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA