Claims:WE CLAIM:

1. A low clamping, high voltage surge protectiondevice (100) comprising:
a circuit (70) for achieving common mode protection;
a circuit (80) for clamping of the ringing waveform; and
a circuit (90) for eliminating false triggersfor the critical surge arresting components.

2. The low clamping, high voltage surge protectiondevice (100) as claimed in claim 1, wherein the common mode protection circuit (70) comprising of Metal Oxide Varistor MOV1 (10) connected between Line-Neutral and a MOV2(20) connected between Line-Earth.

3. The low clamping, high voltage surge protectiondevice as claimed in claim 1, wherein the circuit (80) for clamping of the ringing waveform comprises an impedance Z1 (30) connected in series to Line reducing the current and series impedance Z1 (30) alongwith MOV3(40) that follows acting together forreducing the clamping voltage to very low amplitude.

4. The low clamping, high voltage surge protectiondevice as claimed in claim 1,wherein circuit (90) for achieving common mode protection further comprises an impedance Z2 (60) is connected in parallel with a Gas Discharge Tube GDT (50) to circumvent the false triggers of said GDT (50).
, Description:FIELD OF INVENTION:
[001] The present invention relates to the field of surge protection devices. The present invention more particularly relates to low clamping, high voltage surge protection device for LED lights and lighting control devices.
BACKGROUND AND PRIOR ART:
[002] A LED (Light Emitting Diode) luminaire broadly comprises of Electronic Ballast (also referred as LED Driver), LED chips, MCPCB (Metal Cladded Printed Circuit Board) and, thermally Conductive Metal housing (generally referred as casing). From the data gained over past 10 years, majority of the failure of the luminary happens due to damage of electronic components within the LED driver by the high voltage surge energy which exceeds the capacity of the components.
[003] Generally, the LEDs in the LED lights are reliable and mostly the LED drivers fail for various reasons in which the voltage surge impact is the most common reason. Users of the LED lamps end up replacing the whole lamp as majority of the time getting replacement drivers becomes tough and replacement cost with a trained technician becomes high.
[004] The addition of Surge Protection Devices (SPD) in the current path between the power source and the lighting equipmentprovides a clamping voltage (Vc) which potentially reduces the risk on the Electronics Driver. However, in most of the cases it has been noticed that the clamping voltage is much higher than the operating voltage of Electronics driver thus causing damage to LED driver or the Device.
[005] For example, a LED luminary or Lighting Control device with 4kV integrated surge protection when connected with a 20kV external SPD – Can the system be called as a 20kV protected system? The answer is ‘NO’ in most cases.
[006] A conventional SPD which qualifies IEC 61643-11 will be capable of clamping 8/20uS surge level to its claimed surge voltage level of 1.2kV to 1.5kV. Unfortunately, the clamped voltage will not follow the 8/20uS waveform; but will continue to ring for very long period of time.
[007] The same voltage enters the Luminaire and the inbuilt protection (4kV) will fail to act as the front-end circuit of all drivers will be able to handle only 8/20uS strikes. This sustained high voltage is well above the limits of the electronics components like bridge rectifiers, switching MOSFETs, clamping diodes etc. All these components will all be exposed to a level much higher than the absolute maximum ratings of the components for certain microseconds to few milliseconds resulting in the catastrophic failures occur in the components and the circuit fails permanently.
[008] The mode of connection for providing differential mode Surge protection that is being widely used is as shown in Figure 1.
[009] US Publication No. 20110299203 discloses a hybrid surge protection device (SPD) having a clamping voltage that is controlled by precisely limiting the overshoot voltage of a gas discharge tube (GDT) in a hybrid suppression network including a main surge suppression varistor (VR1) connected in series with the GDT. A clamping control circuit in parallel with the network includes a voltage limiting device (VR2) in parallel with the GDT for preventing voltage overshoot by the GDT above a limiting voltage responsive to an occurrence on the protected line of a surge combination wave. The clamping control circuit also includes a capacitor (C1) connected in parallel with the VR1 providing a bypass path for electrical current and voltage potential to the GDT. Biasing resistors R1 and R2 can be connected in parallel to C1 and VR2, respectively, to distribute the voltage between the clamping control circuit and the network.
[0010] US Publication No. 20120250205 discloses a surge protective device that includes a comparator to determine when a line voltage of a line is above a threshold. The device may include a switch to couple a clamping device to the line voltage when the comparator determines the line voltage is above a threshold, wherein the clamping device shunts current from the line. The switch may include a silicon-controlled rectifier (SCR) or a thyristor and the clamping device may include a selenium surge suppression device.

[0011] US Publication No. 20160353545 discloses a photocontroller with surge protecting function including a photocontroller unit, a surge protection unit, and an photocontroller base. On the basis of an existing photocontroller unit and an existing photocontroller base, the surge protection unit is integrated inside the photocontroller unit or the surge protection unit can be connected in a plug-in manner. The surge protection unit is connected in parallel to a power supply phase line terminal and a neutral line terminal of the photocontroller unit. A ground line terminal of the surge protection unit is connected, by means of as ground connector, to the conductive part disposed on the photocontroller base. The conductive piece is grounded.
[0012] US Publication No. 20160329701 discloses a surge protector having a hot line, a load line, a neutral line, and a ground line, the surge protector. The surge protector has a fuse coupled between the hot line and the load line to protect loads from current surges. A differential mode protection circuit is coupled between the load line and the neutral line to protect loads from differential mode transient voltage surges. A common mode protection circuit is coupled to the load line, the neutral line and the ground line to protect loads from common mode transient voltage surges.
[0013] US Publication No. 20160204600 discloses an overvoltage protection apparatus that includes a first connection for coupling to an N line, and at least one voltage-limiting element which is designed to block the current through the voltage-limiting element up to a predefinable threshold value of the voltage dropped across the voltage-limiting element and to conduct the current above this threshold value. The overvoltage protection apparatus may further include a second connection for coupling to a metal housing of an electrical apparatus, at least one capacitor, and at least one first non-reactive resistor. The at least one capacitor, the at least one first non-reactive resistor and the at least one voltage-limiting element are connected in series between the first connection and the second connection.
[0014] US Publication No. 20160050724 discloses an AC direct driver lighting system including a surge protection circuit and a current limiting circuit. The AC direct driver lighting system includes an LED load, a rectifier, and an LED driver configured to receive rectified AC voltage from an AC power source and drive the LED load. The AC direct driver lighting system further includes a surge protection circuit and a current limiting circuit disposed between the AC power source and the LED load. The surge protection circuit and the current limiting circuit suppress excessive current flowing through the AC direct driver lighting system.
[0015] US Publication No. 20030086225 discloses an improved surge suppressor which combines a ground fault circuit interrupter with overvoltage protection for AC power lines. The surge suppressor includes a switchable device for disconnecting power from the ground fault circuit interrupter in the event the AC neutral is lost.
[0016] Indian Publication No. 4538/CHE/2013 relates to an electronic protector cum surge guard. The surge guard comprising: a set of circuit arrangement to set the over voltage and the under voltage level as per load requirement, a voltage sensing circuit to sense the voltage levels from power supply to the Load coupled, and a voltage comparator to compare the set voltage level and sensed voltage in proportional levels, wherein the voltage comparator triggers and switches off the relay to control/avoid over and under voltage limits of supply to the Load.
[0017] For getting low clamping voltage, a 320V MOV (Metal Oxide Varistor) is usually used, but drawback using a low voltage rated MOV (such as 320V) is that the MOV gets damaged during occasional “Loss of Neutral” fault (Because during such fault upto 440V AC (RMS) might appear between Line and Neutral).
[0018] The clamping voltage is directly proportional to the max operating voltage of the SPD. The currently available SPDs in the market which has lower clamping voltages are all having very low operating voltage. In the field one common issue is the entry of 440V, this voltage which comes across the differential inputs is good enough to damage the low rated components. Hence majority of the specifications in LED space is mandating 440V sustenance as a minimal requirement.
[0019] The common solution followed for preventing the MOV from damage during loss of neutral fault is to use a 440V rated MOV. However, even this approach has a serious drawback i.e. clamping voltage of the MOV will be very high (over 1000V) during application of Surge.Such a huge clamping voltage does not provide ample protection to the circuit (especially when the switching device used is less than 1000V).
[0020] The present invention aims to overcome both the drawbacks as discussed above.
[0021] Thus, the present invention provides alow clamping, high voltage surge protection device for LED lights and lighting control devices.

OBJECTS OF THE INVENTION:
[0022] The principal objective of the present invention is to provide alow clamping, high voltage surge protection device for LED lights and lighting control devices.
[0023] Another object of the present invention is to provide lower clamping voltage and absorb high surge energy which is more than the 8/20µs duration.
[0024] Yet another object of the present invention is to provide protection of LED drivers from surge levels of 8/20µs.
[0025] Still another object of the present invention is to provide protection of LED drivers from sustained high voltage condition which occurs as a ringing waveform that follows the 8/20µs pulse.
[0026] Another object of the present invention is provide a low clamping high voltage SPD to withstand 440V AC while still providing lowest possible ‘V Clamp’ of less than 800V during ringing portion of the pulse.
[0027] Another object of the present invention is to provide false triggering detection circuit to determine the right surge instance and avoid the triggering of critical components due to leakage in MOV’s.

SUMMARY OF THE INVENTION:
[0028] In accordance with the said objectives, the present invention provides alow clamping, high voltage surge protection device for LED lights and lighting control devices. The device according to the present invention consists of metal-oxide varistor (MOVs), series and parallel impedances and Gas Discharge Tube (GDT).Said MOVsare connected between Line-Neutral and Line-Earth instead of Neural-Earth as present in the prior arts.A series impedance (Z1) is introduced to Line to reduce the current and said impedance (Z1) and MOV3 that follows, act together to reduce the clamping voltage to very low amplitude. Since the series connected MOV3 can generate false triggers for the Gas Discharge Tube a technique is used to circumvent the same. This is achieved by having parallel impedance (Z2) across the Gas Discharge tube.

BRIEF DESCRIPTION OF THE DRAWINGS
[0029] It is to be noted, however, that the appended drawings illustrate only typical embodiments of the present subject matter and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system or methods in accordance with embodiments of the present subject matter are now described, by way of example, and with reference to the accompanying figures, in which:
[0030] Figure 1discloses a mode of connection for providing differential mode Surge protection being used in prior art;
[0031] Figure 2 discloses circuit connection of the surge protection device according to the present invention.
[0032] The figures depict embodiments of the present subject matter for the purposes of illustration only. A person skilled in the art will easily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.
DETAIL DESCRIPTION OF THE INVENTION
[0033] The present invention will be described in detail below with reference to an embodiment as shown in the drawing.
[0034] Surge Protection being one of the critical protective mechanisms used in all Surge Protection Devices (SPD), none of them are capable to provide the desired level (A voltage below or matching the Input Components of the Power Supply/LED Driver, usually in the range of 600V to 800V) of clamping voltage required to safe guard the LED drivers. The front-end rectification portions followed by switching components are all capable of handling voltage levels between 800 to 1000V. However, when the SPD is used at the front-end of the driver, it clamps high surge voltage levels to a range of 1.2kV to 1.5kV only.This causes the failure of critical components in the driver and lead to major failures.Most cases, drivers don't get failed during 8/20µs pulse. The failure occurs when the ringing voltage (A waveform which continues to sustain after the 8uS pulse shoot-up, ideally a controlled surge will have 8uS raise time and 20uS fall time – ringing will take it to even more than 100uS) sustains at the line for over 100µs. The clamping provided in the LED Guard is capable to clamp the ringing waveform also. The most conventional way of common mode protection is by having one MOV each between Line-Earth and Neutral-Earth.
[0035] Referring to the figure 2, a surge protection device (100) is provided to achieve common mode protection and clamping of the ringing waveform. The MOV from Neutral-Earth as used in prior art is eliminated and with the help of MOV between Line-Neutral,MOV1 (10),and Line-Earth, MOV2 (20),the same level of protection is achieved.
[0036] The ringing which occurs followed by the surge needs a proper clamping circuit to arrest it. However due to very high voltage the clamping components can fail with in short time. Hence, a series impedanceZ1 (30) connected to Line is introduced to reduce the current and said impedance Z1 (30)and another MOV3 (40) that follows act together to reduce the clamping voltage to very low amplitude. Since the series connected said MOV3(30) can generate false triggers for the Gas Discharge Tube, GDT (50), another impedance Z2 (60) is connected in parallel with said GDT (50).
[0037] The surge protection device according to the present invention is tested for 440V withstand for over 24hourswhich commonly occurs due to Neutral line disconnection still providing lowest possible ‘V Clamp’ of less than 800V during ringing portion of the pulse. Common Mode protection is achieved with single MOV which in conventional SPDs are being achieved using two MOVs, one between Line and Earth and another between Neutral and Earth.
[0038] Implementation of “Z Protection Circuit” safeguards critical protection components of the device by lowering its current and/or reducing the voltage across it after surge subsides.
[0039] It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should be appreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present subject matter. It should also be appreciated by those skilled in the art that by devising various assembly that, although not explicitly described or shown herein, embody the principles of the present subject matter and are included within its spirit and scope. Furthermore, all examples recited herein are principally intended expressly to be for pedagogical purposes to aid the reader in understanding the principles of the present subject matter and the concepts contributed by the inventor(s) to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. The novel features which are believed to be characteristic of the present subject matter, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures.
[0040] These and other advantages of the present subject matter would be described in greater detail with reference to the following figures. It should be noted that the description merely illustrates the principles of the present subject matter. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present subject matter and are included within its scope.
[0041] It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a single component or step, or the functions or structures of one-step or component may be split among plural steps or components. The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of the various structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries are possible. In addition, while a feature of the present invention may have been described in the context of only one of the illustrated embodiments, such feature may be combined with one or more other features of other embodiments, for any given application. It will also be appreciated from the above that the fabrication of the unique structures herein and the operation thereof also constitute methods in accordance with the present invention. The present invention also encompasses intermediate and end products resulting from the practice of the methods herein. The use of “comprising” or “including” also contemplates embodiments that “consist essentially of” or “consist of” the recited feature.
[0042] Although embodiments for the present subject matter have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features and methods are disclosed as embodiments for the present subject matter. Numerous modifications and adaptations of the system/component of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the scope of the present subject matter.