Surge suppressor arranged for suppressing surges, driver comprising surge suppressor and method for operating surge suppressor

Abstract

A surge suppressor comprises a metal oxide varistor, MOV, connected to a current conducting track and arranged for suppressing surges present on the current conducting track, a temperature dependent component thermally coupled to the current conducting track, wherein an electrical parameter of the temperature dependent component depends on temperature, a control device arranged for providing a quantitative measure of the lifetime of the MOV based on fluctuations of the electrical parameter over time.

Description

BACKGROUND

[0001] Circuits can suffer from surges. Generally, surges are transient waves of current, voltage or power in a circuit. They can alternatively be referred to as transients or spikes. A common source of surges is equipment that is turned on and off. According to a general rule of thumb, the larger the electrical load being turned on and off, the larger the surge will be. Modern lighting equipment based on light emitting diodes, LEDs, can also generate surges in a circuit, as they are typically controlled by simple on / off control and thus control the current, and hence the light output. Another fundamental cause of surges is a lighting strike. A lighting strike can cause a power surge, i.e. a large amount of energy flowing into the circuit.

[0002] While such surges can be unavoidable and short-lived, they can disrupt the normal operation of components within the circuit. To prevent electrical components from such sudden surges, surge suppressors can be employed. Metal oxide varistors, MOVs, are an example of such surge suppressors. MOVs are able to suppress surges by providing a shunt path to excess voltage or current, thereby directing the surge away from the electrical component(s) to be protected.

[0003] When MOVs are used for surge protection, the current through the MOV corresponds to the amplitude of the surge. It is known that MOVs can handle a limited number of surges. Over time, due to wear and tear of the MOV, the protection function will become smaller and eventually the component can fail. It is therefore desirable to be able to perform maintenance of a circuit with a surge suppressor before the equipment or surge suppressor fails. SUMMARY

[0004] It would be advantageous to implement an improved surge suppressor comprising an improved metal oxide varistor, MOV. Further, it would be advantageous to implement a driver comprising such a surge suppressor and a corresponding method.

[0005] In a first aspect of the present disclosure, a surge suppressor is presented, the surge suppressor comprising: a metal oxide varistor, MOV, connected to a current conducting track and arranged for suppressing surges present on the current conducting track; a temperature dependent component thermally coupled to the current conducting track, wherein an electrical parameter of the temperature dependent component depends on temperature; and a control device arranged for providing a quantitative measure of the lifetime of the MOV based on fluctuations of the electrical parameter over time.

[0006] A metal oxide varistor, MOV, is an example of a surge suppressor. A MOV is able to suppress surges by providing a shunt path to excess voltage or current, thereby directing the surge away from the electrical components to be protected. By way of example, other surge suppressors can be used that are able to suppress surges in a similar manner. The present invention according to the present disclosure is particularly useful when the surge suppressor employed has a limited lifetime, i.e. is able to withstand a limited number of surges or surges of limited amplitude.

[0007] The temperature dependent component is arranged to give an indication of the occurrence of a surge. This can be done by a relation between the amplitude of the current and the temperature of the current carrying track. A surge of higher amplitude will result in a higher temperature of the current carrying track. The temperature dependent component can directly read the temperature of the current carrying track, or alternatively can be arranged to change a parameter of the component, such as the resistance, inductance or capacitance. The temperature can then be monitored indirectly by monitoring the parameter of the component.

[0008] The control means can for example be a microcontroller or similar device able to receive an input value such as from the temperature dependent component and provide an output instruction to an output component, which can or can not be part of the surge suppressor. The output can for example be an indication that the surge suppressor needs to be replaced. Alternatively, the output can be a count of the number of surges. The control means can also be an integrator designed to integrate the amplitude of the surges over a period of time. The amplitude of the surge can be obtained by relating the output from the temperature dependent component to the amplitude of the surge using a predefined correlation.

[0009] The present invention proposes a surge counter based on a temperature dependent component. The current carrying track of a MOV will heat up due to a surge and this temperature is sensed by a temperature dependent component as proposed in the figure.

[0010] When the number of surges and their intensity can be counted, this information can be used to initiate preventive maintenance of the driver. Such preventive maintenance will increase the uptime of the public lighting system.

[0011] An important aspect of the present invention is the temperature sensor that measures the track temperature. The delta track temperature corresponds to the peak current in the track. The track temperature can be sensed by mounting a temperature sensitive SMD component on top of the track. This sensitive element can be a NTC or PTC or any other thermally sensitive SMD component.

[0012] A less preferred solution involves the use of a current transformer to measure the current intensity, but the cost and size of such a transformer will increase both the cost and size of the driver.

[0013] According to an embodiment, the surge suppressor can be arranged for providing a predetermined threshold, wherein the control device is arranged for providing the quantitative measure of the lifetime of the MOV based on a comparison of the fluctuations of the electrical parameter over time with the provided predetermined threshold.

[0014] In a detailed example thereof, the control device comprises a memory having a predetermined threshold stored thereon, wherein a value of the electrical parameter exceeding the predetermined threshold indicates the presence of a surge on the current conducting track. One advantage of this embodiment is that a possible failure of the surge suppressor can be indicated based on the amplitude of the surge alone, regardless of the number of surges that have already been suppressed by the surge suppressor.

[0015] In an alternative example, the predetermined threshold can be provided by a voltage divider used by the surge suppressor. The voltage divider can consist of two resistors connected in series, wherein an input voltage (e.g. a stable supply voltage) is applied across the resistor pair and then the predetermined threshold can be considered as a voltage reference between the resistor pair.

[0016] According to an exemplary embodiment, the control device is arranged for counting the number of times the electrical parameter exceeds the predetermined threshold, thereby providing the quantitative measure of the lifetime. Periodically replacing the surge suppressor is often recommended, regardless of the actual amplitude of the surges that have been suppressed. This can ensure that valuable electrical equipment can continue to work efficiently. By counting the number of surges experienced, preventive maintenance can be effectively performed. By doing so, the user can eliminate the need for premature replacement of the MOV and at the same time ensure that the MOV can still function well.

[0017] In an embodiment, the temperature dependent component is a temperature sensitive surface mounted device, SMD. Implementing the temperature dependent component as an SMD can be advantageous. Doing so has the effect of utilizing less space on the circuit, thereby allowing a compact implementation, and at the same time, the SMD is in direct contact with the current carrying track, thereby allowing it to effectively monitor the temperature.

[0018] According to an embodiment, the temperature dependent component has a negative temperature coefficient. A negative temperature coefficient, NTC, refers to a material that experiences a decrease in electrical resistance when the temperature of the material increases. Such a material can show a relatively fast decrease with temperature, i.e. a low coefficient. The lower the coefficient, the larger the decrease in resistance for a given increase in temperature. The skilled person understands that a negative temperature coefficient can also be associated with other electrical parameters, such as inductance or capacitance, for example.

[0019] The NTC can be connected to an (analog) input of a microprocessor. The microprocessor is responsible for the processing of the data.

[0020] According to one embodiment, the control device is arranged for counting the number of times said electrical parameter drops below said predetermined threshold. This embodiment can be implemented together with the embodiment when the temperature dependent component has a negative temperature coefficient. A surge will cause an increase in temperature of the current carrying track. When the temperature increases, the value of the electrical parameter associated with the temperature dependent component will decrease. When the parameter drops below a predetermined threshold, the device in cooperation with the control device can confirm the occurrence of a surge. Such an embodiment allows fluctuations in the current within the normal operating range and eliminates the possibility of false alarms.

[0021] In an exemplary embodiment, the temperature dependent component has a positive temperature coefficient. A positive temperature coefficient, PTC, refers to a material that experiences an increase in resistance when the temperature of the material increases. Such materials show a relatively fast increase with temperature, i.e. a high coefficient. The higher the coefficient, the larger the increase in resistance for a given increase in temperature. The skilled person understands that a positive temperature coefficient can also be associated with other electrical parameters such as inductance or capacitance, for example.

[0022] According to one embodiment, the control device is arranged for counting the number of times said electrical parameter increases above said predetermined threshold. This embodiment can be implemented together with the embodiment when the temperature dependent component has a positive temperature coefficient. A surge will cause an increase in temperature of the current carrying track. When the temperature increases, the value of the electrical parameter associated with the temperature dependent component will also increase. When the parameter increases above a predetermined threshold, the device in cooperation with the control device can confirm the occurrence of a surge. Such an embodiment allows fluctuations in the current within the normal operating range and eliminates the possibility of false alarms.

[0023] In one embodiment, the current conducting track is a printed circuit board, PCB, track, and wherein said temperature dependent component is a surface mounted device, SMD, mounted on top of said PCB track. The device according to the present disclosure can be implemented on a PCB, thereby limiting the overall size of the device. This has the advantage that the device according to the present disclosure can easily and in a compact manner be integrated with other devices.

[0024] According to one embodiment, the control device comprises a processor for providing said quantitative measure of said lifetime of said MOV. It is an advantage that a quantitative measure, i.e. the number of counted surges or the total amplitude of measured surges, can be indicated to the user. When a quantitative measure is provided to the user, an effective maintenance of the surge suppressor can be deployed.

[0025] In an exemplary embodiment, the temperature dependent component, wherein the resistance value of said temperature dependent component depends on temperature. As mentioned earlier in the present disclosure, NTC or PTC materials often associate resistance with temperature. However, this is not limiting. A simple modification can allow other electrical parameters to vary with temperature.

[0026] In a second aspect of the present disclosure, a driver arranged to receive electrical power and to provide output electrical power to an electrical load is presented, the driver comprising a surge suppressor according to any of the preceding embodiments, wherein the surge suppressor is arranged to suppress surges to the electrical load.

[0027] It is noted that the limitations and advantages associated with the first aspect of the present disclosure are also associated with the second aspect of the present disclosure. Further, it is envisaged that the surge suppressor can be integrated in an existing component, such as a driver arranged to drive an electrical load, e.g. a driver for a light emitting diode, LED, based lighting device.

[0028] In a third aspect of the present disclosure, a method of operating a surge suppressor according to any of the embodiments in the first aspect is presented, the method comprising the steps of: suppressing, by a metal oxide varistor, MOV, connected to the current conducting track, an electrical surge, providing, by the temperature dependent component, the electrical parameter of the temperature dependent component to the control device, providing, by the control device, the quantitative measure of the lifetime of the MOV based on fluctuations of the electrical parameter over time.

[0029] In a fourth aspect of the present disclosure, a method of operating a driver according to claim 13 is presented, wherein the method comprises the step of counting, by the control device, the number of surges experienced by the surge suppressor.

[0030] These and other aspects of the application will become apparent from the embodiments described below and as illustrated in the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A device according to one embodiment of the present disclosure is shown.

[0032] Figure 2 A device according to one embodiment of the present disclosure is shown.

[0033] Figure 3 A surge suppressor according to the present disclosure is shown.

[0034] Figure 4 A method according to the present disclosure is shown. DETAILED DESCRIPTION

[0035] Figure 1 A device according to one embodiment of the present disclosure is shown. Embodiment 1 shows a temperature dependent component 4 mounted on a printed circuit board, PCB, 2. The temperature sensitive component 4 is in thermal contact with a current carrying track 3.

[0036] In embodiment 10, Figure 2 These components are shown in another configuration.

[0037] Figure 3 A surge suppressor 20 according to the present disclosure is shown. The surge suppressor 20 comprises a metal oxide varistor MOV 22 connected to a current carrying track 21 and arranged for suppressing surges present on said current carrying track 21. The surge suppressor further comprises a temperature dependent component 23 thermally coupled to the current carrying track 21, wherein an electrical parameter of said temperature dependent component depends on temperature.

[0038] The surge suppressor 20 further comprises a control device 24 arranged for providing a quantitative measure of the lifetime of said MOV based on fluctuations of said electrical parameter over time. The control device is in communication with the temperature dependent component in order to determine / count the number of surges on the current carrying track 21. Furthermore, the surge suppressor can comprise an indicating device (not shown) or other device connected to an external display device (not shown) which can be arranged to give an indication of the number of surges that have occurred on the current carrying track 21.

[0039] Figure 4 A method 30 according to the present disclosure is shown. The method 30 comprises the steps of:

[0040] - providing 32, by said temperature dependent component, said electrical parameter of said temperature dependent component to said control device;

[0041] - providing 33, by said control device, said quantitative measure of said lifetime of said MOV based on fluctuations of said electrical parameter over time.

[0042] Within the scope of the present disclosure, the term metal oxide varistor MOV has been used to refer to a particular type of surge suppressor. The skilled person understands that the teachings of the present disclosure can equally apply with appropriate modifications to other types of surge suppressors for suppressing surges in household appliances.

[0043] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single processor or other unit can fulfill the functions of several items recited in the claims.

[0044] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program can be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state storage medium supplied together with or as part of other hardware, but can also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. A surge suppressor, comprising: - Current conduction track; - A metal oxide rheostat (MOV) is connected to the current conduction rail and is arranged to suppress surges present on the current conduction rail; - A temperature-dependent component thermally coupled to the current conduction track, wherein the electrical parameters of the temperature-dependent component depend on the temperature of the current conduction track; - A control device is arranged to provide a quantitative measurement of the lifespan of the MOV based on the fluctuations of the electrical parameters over time.

2. The surge suppressor of claim 1, wherein the surge suppressor is arranged to provide a predetermined threshold, wherein the control device is arranged to provide a quantitative measurement of the lifetime of the MOV based on a comparison of the fluctuation of the electrical parameters over time with the provided predetermined threshold.

3. The surge suppressor of claim 2, wherein the control device is arranged to count the number of times the electrical parameter exceeds the predetermined threshold, thereby providing the quantitative measurement of the lifetime.

4. The surge suppressor according to any one of the preceding claims, wherein the temperature-dependent component is a thermal surface mount device (SMD).

5. The surge suppressor according to any one of claims 1-3, wherein the temperature-dependent component has a negative temperature coefficient.

6. The surge suppressor of claim 3, wherein the temperature-dependent component has a negative temperature coefficient, and wherein the control device is arranged to count the number of times the electrical parameter drops below the predetermined threshold.

7. The surge suppressor according to any one of claims 1-3, wherein the temperature-dependent component has a positive temperature coefficient.

8. The surge suppressor of claim 3, wherein the temperature-dependent component has a positive temperature coefficient, and wherein the control device is arranged to count the number of times the electrical parameter increases to exceed the predetermined threshold.

9. The surge suppressor according to any one of claims 1-3, 6 and 8, wherein the current conduction track is a printed circuit board (PCB) track, and wherein the temperature-dependent component is a surface mount device (SMD) mounted on top of the PCB track.

10. The surge suppressor according to any one of claims 1-3, 6 and 8, wherein the control device includes a processor for providing the quantitative measurement of the lifetime of the MOV.

11. The surge suppressor according to any one of claims 1-3, 6 and 8, wherein the resistance value of the temperature-dependent component depends on the temperature.

12. A driver arranged to receive electrical power and provide output electrical power to an electrical load, the driver comprising a surge suppressor according to any one of claims 1-11, wherein the surge suppressor is arranged to suppress surges to the electrical load.

13. A method of operating a surge suppressor according to any one of claims 1-11, the method comprising the steps of: - Surge waves are suppressed by a metal oxide rheostat (MOV) connected to the current conduction track; - The temperature-related component provides the electrical parameters of the temperature-related component to the control device; The control device provides a quantitative measurement of the lifespan of the MOV based on the fluctuations of the electrical parameters over time.

14. The method of claim 13, wherein the method comprises the following steps: The control device counts the number of surges experienced by the surge suppressor.

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