Power Component And System With The Power Component

Abstract

A power component includes two electric terminals, a component housing, a main component at least partially surrounded by the component housing, connected with the two terminals, and configured to carry a power current flowing between the two electric terminals, and a sensor and emitter unit which is configured to measure a value of a physical quantity (T, V, ΔV) characterizing an operating state of the main component, and to emit an electromagnetic signal, in which the measured value of the physical quantity is encoded. The sensor and emitter unit includes an antenna for emitting the electromagnetic signal which is spaced apart from the main component and arranged in, on and/or at the component housing.

Claims

1. A power semiconductor comprising: two electric terminals; a component housing; a main component at least partially surrounded by the component housing, connected with the two terminals, and configured to carry a power current flowing between the two electric terminals; and a sensor and emitter unit configured to measure a value of a physical quantity characterizing an operating state of the main component, and to emit an electromagnetic signal, in which the measured value of the physical quantity is encoded, the sensor and emitter unit comprising an antenna for emitting the electromagnetic signal, the antenna being spaced apart from the main component and arranged in, on and/or at the component housing.

2. The power semiconductor device of claim 1, wherein a rated current of the main component is at least about 10 A, wherein the power semiconductor device is a high voltage component, wherein a rated voltage of the main component is at least about 600 V, wherein a rated power of the main component is at least about 2 kW, and/or wherein the power component is configured to control the power current and/or to break the power current.

3. The power semiconductor device of claim 1, wherein the power semiconductor device is a vertical power semiconductor device, and/or comprises a power semiconductor diode and/or a power semiconductor switch, in particular a power thyristor, a power MOSFET or a power IGBT, and/or wherein the power semiconductor device is one of a power semiconductor diode and a power semiconductor switch, in particular a power thyristor.

4. The power semiconductor device of claim 1, wherein the sensor and emitter unit comprises a low power transponder, wherein the sensor and emitter unit is configured to store several measured values of the physical quantity at least temporarily, wherein the sensor and emitter unit is configured to encode several measured values of the physical quantity into the electromagnetic signal, typically together with a respective measuring time, and/or wherein the sensor and emitter unit is configured to encode an identifier for the power component into the electromagnetic signal.

5. The power semiconductor device of claim 4, wherein the low power transponder is a Bluetooth transponder or an RFID-transponder, in particular an active RFID tag or a passive RFID tag.

6. The powers semiconductor device of of claim 1, wherein the sensor and emitter unit comprises a sensor unit and an emitter unit comprising the antenna, wherein the emitter unit is spaced apart from the sensor unit, wherein the sensor unit is configured to convert an analog input signal representing the physical quantity into a digital value, store the digital value, process the digital value and/or transfer the digital value and/or the processed digital value to the emitter unit, wherein the sensor and emitter unit is provided by one or more RFID-sensors, and/or wherein a rated power of the sensor and emitter unit is at most 5 W.

7. The power semiconductor device of claim 1, wherein the sensor and emitter unit comprises two sensors each of which is configured to measure a respective physical quantity characterizing the operating state of the main component, wherein the sensor and emitter unit is configured to measure different physical quantities each characterizing the operating state of the main component, and/or wherein the sensor and emitter unit is configured to measure a temperature of the main component, a voltage of at least one of the two electric terminals, and/or a voltage drop across the main component and/or the two terminals.

8. The power semiconductor device of claim 1, wherein the main component is at least substantially shaped as a cylinder, wherein at least one of the two electric terminals is at least substantially shaped as a cylinder, wherein the component housing is at least substantially shaped as a hollow cylinder, wherein the main component comprises a semiconductor body comprising a rectifying junction, wherein a diameter of the main component and/or the semiconductor body is at least two inch, typically in a range from two inch to 6 inch, and/or wherein the power semiconductor device comprises a press pack design or a press design.

9. The power semiconductor device of claim 8, wherein the sensor and emitter unit is configured to measure a temperature of the rectifying junction and/or a core temperature of the semiconductor body.

10. The power semiconductor device of claim 9, wherein the rectifying junction extends, in a cross-section, at least substantially through the semiconductor body, wherein the rectifying junction is functionally connected between the two electric terminals, wherein the rectifying junction is configured to carry a power current between the two electric terminals, and/or wherein the rectifying junction is a PN-junction formed between a p-type semiconductor region and an n-type semiconductor region of the semiconductor body. 11. The power semiconductor device of claim 10, wherein each of the p-type semiconductor region and the n-type semiconductor region is in ohmic contact with and/or at least substantially covered by one of the two electric terminals. 12. The power semiconductor device of claim 8, further comprising an integrated resistive structure arranged at or close to the rectifying junction, and/or an integrated resistive structure arranged at or close to a center of the semiconductor body.

13. (canceled)

14. (canceled)

15. The power semiconductor device of claim 1, wherein the component housing comprises a dielectric and/or a ceramic, wherein the component housing substantially encloses the main component, wherein the antenna is a substantially flat and/or a coil antenna, and/or wherein the antenna is arranged at an outer side of the component housing.

16. (canceled)

17. A power module, comprising at least two power components, the at least two power components being at least pairwise connected with each other, each of the at least two power components comprising: two electric terminals; a component housing; a main component at least, partially surrounded by the component housing, connected with the two terminals, and configured to carry a power current flowing between the two electric terminals; and a sensor and emitter unit configured to measure a value of a physical quantity characterizing an operating state of the main component, and to emit an electromagnetic signal, in which the measured value of the physical quantity is encoded, the sensor and emitter unit comprising an antenna for emitting the electromagnetic signal, the antenna being spaced apart from the main component and arranged in, on and/or at the component housing, at least one of the at least two power components being a power semiconductor device.

18. The power module of claim 17, wherein the power module is a part of or forms a power converter, in particular a power rectifier and/or comprises at least one of: two power semiconductor devices connected in parallel; the power semiconductor device and a power fuse connected in series a first submodule comprising a first power semiconductor device and a first power fuse connected in series; and a second submodule connected with the first submodule and comprising a second power semiconductor device and a second power fuse connected in series.

19. The power module of claim 18, wherein the component housing of the power fuse provides a fuse body, wherein the main component of the power fuse is at least substantially shaped as a cylinder, wherein the power fuse comprises a square body design, and/or wherein the electric terminals of the power fuse comprise as flush end design.

20. A system comprising: a power component, the power component being a power semiconductor device comprising: two electric terminals; a component housing; a main component at least partially surrounded by the component housing, connected with the two terminals, and configured to carry a power current flowing between the two electric terminals; and a sensor and emitter unit configured to measure a value of a physical quantity characterizing an operating state of the main component, and to emit an electromagnetic signal, in which the measured value of the physical quantity is encoded, the sensor and emitter unit comprising an antenna for emitting the electromagnetic signal, the antenna being spaced apart from the main component and arranged in, on and/or at the component housing; a receiving unit configured to receive the electromagnetic signal from the power component, and to decode the measured value of the physical quantity; and an evaluation unit connectable with the receiving unit, and configured to use the decoded measured value of the physical quantity for analyzing the operating state of the main component of the power component and/or an operating state of a power module comprising the cower component.

21. The system of claim 20, wherein the evaluation unit is configured to use the decoded measured value for estimating an aging status of the power component, and/or for determining at least one of a warning message, and a control parameter for the power component, wherein the evaluation unit comprises a network interface for connecting the evaluation unit to a data network, in particular a network interface which is configured to transceive digital signals and/or digital data between the evaluation unit and the data network, and/or wherein receiving unit comprises a network interface for connecting the receiving unit to the data network.

22. (canceled)

23. The system of claim 21, wherein the evaluation unit is configured to at least one of: use the decoded measured value for determining at least one of a current strength of the power current and a current distribution between two of the power components; determine a control parameter for at least one of the power components, in particular a control parameter referring to the current strength; influence the current distribution; decode measured values of different physical quantities of the power component; decode the measured value of a temperature, a voltage and/or a voltage drop of the power component; and determine a current temperature dependent property of the power component, in particular an electric resistance, an electric resistivity, an electric conductance, and/or an electric conductivity of the power component.

24.-34. (canceled)

35. The power module of claim 19, wherein the power fuse comprises a resistive structure arranged at or close to a center of the fuse body, in particular a center with respect to a longitudinal axis and/or a cylinder axis of the fuse body and/or the main component, and/or at or close to the main component, in particular at or close to a lateral surface of the main component

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The components in the figures are not necessarily to scale, instead emphasis being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts. In the drawings:

[0094] FIG. 1A illustrates a cross-section through a power component according to an embodiment;

[0095] FIG. 1B illustrates a view on a power component according to an embodiment;

[0096] FIG. 1C illustrates a view on a power component according to an embodiment;

[0097] FIG. 1D illustrates a cross-section through a power component according to an embodiment;

[0098] FIG. 1E illustrates a cross-section through a power component according to an embodiment;

[0099] FIG. 2A is a schematic diagram of a power module according to an embodiment;

[0100] FIG. 2B is a schematic diagram of a power module according to an embodiment;

[0101] FIG. 2C is a block diagram of a system according to an embodiment;

[0102] FIG. 2D is a flow chart of a method for monitoring a power component according to embodiments;

[0103] FIG. 2E is a flow chart of a method for manufacturing a power component according to embodiments;

[0104] FIG. 3A is a schematic diagram of a power module according to an embodiment;

[0105] FIG. 3B is a schematic diagram of a power module according to an embodiment; and

[0106] FIG. 3C is a flow chart of a method according to embodiments.

DETAILED DESCRIPTION

[0107] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. It is intended that the present disclosure includes such modifications and variations.

[0108] Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment applies to a corresponding part or aspect in another embodiment as well.

[0109] FIG. 1A shows a schematic cross-section through a power component 100. In the exemplary embodiment, power component 100 is a power fuse having an electrically conductive element 110 as main functional component which is laterally surrounded by a ceramic fuse body forming the component housing 120. Fuse body 120 may e.g. be shaped as a hollow cylinder. The electrically conductive element is in electric contact with two electric terminals 111, 112, and may carry a current between the terminals 111, 112 and break the current above a predetermined threshold current. A sensor and emitter unit 130 having an antenna 133 for emitting electromagnetic signals is arranged on and attached to an outer surface of fuse body 120. As indicated by a wiring 135, the sensor and emitter unit 130 may be connected with measuring tips arranged next to or even at the surface of the electrically conductive element 110. Note that any wiring in the drawings may correspond to a wire, a pair of wires or even more than two wires.

[0110] Accordingly, sensor and emitter unit 130 may measure core temperature values of the electrically conductive element 110 during device operation, and emit the core temperature values encoded into an electromagnetic signal via antenna 133 to a reader (not shown). For sake of clarity, further optional details of power fuse 100 such as a filler are also not shown in FIG. 1A.

[0111] This allows contactlessly transferring the measured temperature values and remote further processing to at least characterize the operating state of power component 100.

[0112] As indicated by the dashed wiring 135′, sensor and emitter unit 130 may alternatively or in addition measure temperature values of terminal 112 (or even both terminals) and emit the terminal temperature value(s) in encoded form with the electromagnetic signal.

[0113] The respective temperature values may be measured for a temperature range from about −40° C. to about 125° C. (for measuring core temperature) or from about −40° C. to about +85° C. (for measuring terminal temperature), and/or with an accuracy of at least 0.5° C.

[0114] FIG. 1B shows a schematic view of a section of a power component 100′. Power component 100′ is similar to power component 100 explained above with regard to FIG. 1A and may also be a power fuse. However, the sensor and emitter unit 130′ of power component 100′ is implemented as an RFID-temperature sensor. RFID-temperature sensor 130′ has a sensor unit 131 with an appropriate measuring circuitry, and an emitter unit 132 with a flat coiled antenna 133.

[0115] As shown in FIG. 1C illustrating a schematic view of a section of a power component 100″, the sensor unit 131 and the emitter unit 132 of RFID-sensor 130″ may be spaced apart from each other, but are functionally coupled with each other, typically via a wired connection.

[0116] FIG. 1D shows a schematic cross-section through a power component 200. Power component 200 is typically similar to the power components 100 to 100″ explained above with regard to FIGS. 1A to 1C and typically also a power fuse, in particular a respective semiconductor fuse. However, in the exemplary embodiment of FIG. 1D, the sensor and emitter unit 230 attached to fuse body (component housing) 220 is connected via respective wires 235 with both electrical terminals 211, 212.

[0117] The sensor and emitter unit 230 is typically configured to measure the voltages at the terminals 211, 212. Further, the sensor and emitter unit 230 may be configured to determine a voltage drop between the two terminals 211, 212.

[0118] As explained above, the sensor and emitter unit 230 may be implemented as a Bluetooth-sensor or an RFID-sensor, for example as an RFID voltage measuring sensor, in particular a respective battery free RFID tag in the exemplary embodiment.

[0119] More particular, the sensor and emitter unit 230 may be configured to measure the AC voltage drop across semiconductor fuse 200 and its main component (conductive element) 211, respectively, even under high power conditions/in high power applications, in particular in high power rectifier applications (see also FIGS. 2A, 2B).

[0120] The voltage measurement may e.g. be used to monitor current distribution (online) in those applications. Alternatively or in addition, information of the operational state of fuse 200 may be determined from the measured values.

[0121] The sensor and emitter unit 230 may be configured to measure AC voltage pulses across the fuse 200 and calculate respective RMS values that may be averaged. In this regard it is noted that the measuring voltage may not be a sinus waveshape, for example even pulsed DC voltage may be used, and can be distorted.

[0122] Further, the sensor and emitter unit 230 is typically protected in order not to create any arc when the (AC) fuse 200 is broken, and full voltage drop of e.g. 2 kV AC applies across fuse 200 and therefore the sensor and emitter unit 230. However, this typically depends on the specifications of the power semiconductor device to which semiconductor fuse 200 is to be connected in series.

[0123] For example, the sensor and emitter unit 230 may fulfil one or more or even all of the following specifications: [0124] Rated measuring voltage: 80 . . . 250 mV; [0125] Rated frequency: 50/60 Hz; [0126] Measurement mode: RMS, average optional; [0127] Measurement update cycle rate: ≤10 s; [0128] Isolation voltage input/output: 5 kV; [0129] Temperature measurement range: −40 . . . ≥125° C.; [0130] Type: RFID; [0131] Frequency range for communication with a reader: UHF; and [0132] Size: several square centimeters, typically less than 25 cm.sup.2.

[0133] The sensor and emitter unit 230 may be placed similarly to an auxiliary contact (not shown) on the fuse body 220.

[0134] Further, the circuitry of sensor and emitter unit 230 is typically enclosed by a non-conducting housing material. This is because it is typically used under high voltage (HV) conditions, for example in an HV electronic stack. Further the sensor and emitter unit 230 is typically used in an environment with a lot of metal (stainless steel, aluminum, copper) in the near.

[0135] Optionally, sensor and emitter unit 230 is further configured for temperature measurements as explained above with respect to FIGS. 1A-1C, in particular for measuring the terminal (connection) temperature.

[0136] FIG. 1E shows a schematic cross-section through a power component 300 implemented as a vertical power semiconductor device, more particular as a power semiconductor diode. This indicated by the dashed line representing a PN junction between a p-type semiconductor region and an n-type semiconductor region of the semiconductor body 310, each of which is in ohmic contact with one of the two power terminals 311, 312.

[0137] In the exemplary embodiment, semiconductor body 310 is laterally enclosed by a dielectric component housing 320 which may e.g. be substantially ring-shaped (when seen from above).

[0138] Further, a sensor and emitter unit 330 is arranged on and at a lateral outer side of housing 320.

[0139] As indicated by the wiring 335, the sensor and emitter unit 330 is typically functionally connected with the semiconductor body 310 and configured to measure a core temperature of semiconductor body 310, more particular a temperature at least close to the PN junction of power diode 300.

[0140] For this purpose, an integrated resistive structure arranged at or close to the rectifying junction and at or close to a center of the semiconductor body with respect to a central axis of semiconductor body 310 which is typically at least substantially perpendicular to the PN junction (cylinder axis).

[0141] Alternatively or in addition, the sensor and emitter unit 330 may be configured to measure the voltages at the power terminals 311, 312 and/or to determine a voltage drop between the power terminals 311, 312. These measurements may e.g. be used to directly measure current imbalances between power diodes connected in parallel.

[0142] Furthermore, the sensor and emitter unit may be configured to measure the temperature at different points in the semiconductor body. Accordingly, a temperature profile may be determined during device operation. In particular in embodiments referring to power MOSFETs and power IGBTs typically having a plurality of respective cells, temperature differences between the cells may provide information on current distribution between the cells and even on ageing.

[0143] In further embodiments, the sensor and emitter unit may alternatively or in addition be configured to measure values of one or more other physical quantities characterizing the operating state of the respective device.

[0144] The sensor and emitter unit 330 may also be at least partly arranged in component housing 320. For example, the sensor and emitter unit 330 may be cast into a casting compound used for encasing semiconductor body 310.

[0145] FIG. 2A shows a schematic diagram of a power module 500 formed by two power components 200, 300 connected in series, namely a power semiconductor diode 300 as explained above with regard to FIG. 1E and a corresponding semiconductor fuse 200 as explained above with regard to FIG. 1D.

[0146] For sake of clarity, the respective the sensor and emitting units which may be used to measure and contactlessly transmit values for the core temperature of power semiconductor diode 300 and the terminal temperatures and the voltage drop across the fuse 200, respectively, are not shown in FIG. 2A. These values may be used to monitor power module 500 or even several power modules during operation.

[0147] The latter is illustrated in FIG. 2B showing a schematic diagram of an exemplary 3-phase power rectifier 600 made of six power modules 501-506 each of which typically corresponds to a power module 500 as explained with regard to FIG. 2A, and FIG. 3A showing a schematic diagram of an exemplary power rectifier 550 made N power modules 501-50N (N being a whole positive number that may be larger than 3, 7 or even 15) each of which typically corresponds to a power module 500 as explained with regard to FIG. 2A. The illustrated power modules 501-506, 501-50N may be considered as respective submodules each comprising and/or being made of a power semiconductor device and a power fuse connected in series.

[0148] Based on the temperature measurements and voltage drop measurements of the power fuses 200, respective currents I.sub.1-I.sub.6 flowing through each of the six modules 501-506 (in FIG. 2A) and respective currents I.sub.1-I.sub.Nflowing through each of the N modules 501-50N (in FIG. 3A), respectively, may be determined with high accuracy as the voltage drops across each of the fuses 200 are measured and the resistance of each of the fuses 200 may corrected in accordance with the measured corresponding fuse temperature.

[0149] Additionally measuring the temperature of the power diodes 300 is not required for determining a current distribution within power rectifiers 550, 600, but may be used for long-term monitoring of the power devices, estimating ageing and/or scheduling maintenance or repair.

[0150] In other words, it may be sufficient if only the power diodes 200 are provided with respective sensor and emitter units.

[0151] In other embodiments, it may be sufficient to only provide the power semiconductor devices with the respective sensor and emitter units.

[0152] This is illustrated in FIG. 3B showing a schematic diagram of an exemplary power electronic device 570 made of M typically at least substantially identical power modules 300′ with M being a whole positive number larger than 1, 3, 7 or even 15. Each power module 300′ may corresponds to a power diode 300 as explained with regard to FIG. 1E. In this embodiment, power electronic device 570 may be a power rectifier. In embodiments referring to power electronic switching devices, each power module 300′ may e.g. be a power thyristor.

[0153] Based e.g. on temperature measurements using the sensor and emitter units of the power modules 300′, an imbalance of the temperatures of the power module 300′ may be determined. Based thereon and e.g. assuming at least substantially equal properties of the power modules 300′, an imbalance of the currents I.sub.1-I.sub.M flowing through the M modules 501-50M may be determined.

[0154] In some applications it may even be sufficient to provide one of the power modules with a respective sensor and emitter unit.

[0155] As illustrated in FIG. 2C a monitoring and/or control system 701 for the power component(s) 100-300 and the power module(s) 500-600 as explained above with regard to FIGS. 1A to 2B typically has a receiving unit 710 configured to receive the electromagnetic signals from the power component(s) 100-300, to decode the measured value(s) of the physical quantity(ies) T, V, ΔV, and an evaluation unit 720 connected with the receiving unit 710, and configured to the determine or even analyze the respective operating state(s) based on the decoded measured value(s) of the physical quantity(ies) T, V, ΔV.

[0156] Receiving unit 710 and evaluation unit 720 may be formed by one device or may be remote to each other and/or connected with each other via a data network.

[0157] Depending on the determined/analysed operating state of one or more of the power modules, evaluation unit 720 may e.g. raise a warning message, and/or determine a control parameter for the power component(s) and use the determined control parameter for operating the power module(s). The latter is illustrated in FIG. 2C by the dashed arrow.

[0158] The system 700 formed by monitoring and/or control system 701 and the power component(s) 100-300 and the power module(s) 500-600 may allow both controlling and long-term monitoring of the power component(s).

[0159] System 700 may perform the method 1000 illustrated in the flowchart of FIG. 2D.

[0160] In a first block 1100, a sensor and emitter unit of a power component, in particular a sensor and emitter unit of a power component as explained herein is used to measure a value of a physical quantity characterizing an operating state of the power component.

[0161] Thereafter, an electromagnetic signal in which the measured value of the physical quantity is encoded is emitted via an antenna of the sensor and emitter unit in a block 1200.

[0162] Typically, the electromagnetic signal is received, and the encoded value is decoded in a block 1300.

[0163] The blocks 1100 to 1300 may be performed several times, for example in regular intervals, and/or for several power components, typically in parallel.

[0164] The encoded value(s) is(are) typically used for determining and/or characterizing the operating state, determining a warning message, a maintenance recommendation and/or a control parameter for the power component(s).

[0165] FIG. 2E shows a flow chart of a method 2000 for manufacturing a power component, in particular a power component as explained herein.

[0166] In a block 2100, a main component configured to carry a power current, and a sensor and emitter unit are provided.

[0167] In a block 2200, the main component is provided with a dielectric component housing and the sensor and emitting unit. This is done such that an antenna of the sensor and emitting unit is attached with the component housing and spaced apart from the main component, and that the sensor and emitter unit can measure a value of a physical quantity which characterises an operating state of the main component and emit via the antenna an electromagnetic signal, in which the measured value of the physical quantity is encoded.

[0168] FIG. 3C shows a flow chart of a method 3000.

[0169] In a first block 3100, a power module as explained herein may be provided.

[0170] In a block 3200, a respective measured value of one or more physical quantities is/are received from one, typically from two or even all of the sensor and emitter units of the power components of the power module.

[0171] The measured value may in particular refer to a temperature of the respective main component, a voltage of at least one of the two respective electric terminals, or a voltage drop across the main component and the two terminals, respectively.

[0172] Thereafter, the received measured value(s) is/are further processed in a block 3300.

[0173] As indicated by the dashed arrow in FIG. 3C, blocks 3200, 3300 may be repeated (several times), for example periodically.

[0174] Further processing may include one or more of the following steps: [0175] determining a temperature distribution of the main components, [0176] monitoring the temperature distribution, [0177] determining a current flow through one or more of the main components, [0178] determining a current flow distribution between the main components, [0179] monitoring the current flow and/or the current flow distribution, and [0180] detecting an imbalance of the temperature distribution and/or the current flow distribution.

[0181] For example, the (provided) power module may be a power module 570 as explained above with respect to FIG. 3B, or a power module 550, 600 as explained above with respect to FIGS. 2B, 3A. In embodiment referring to power module 550, 600, the current flow and/or the current flow distribution may be determined taking into account a given electric resistance between the electric terminals of the power fuses, in particular a respective cold resistance of the power fuses.

[0182] Alternatively or in addition, further processing may include one or more of the following steps: [0183] estimating an ageing of the power module or of one or more power components thereof, [0184] scheduling a maintenance or a repair for the power module, [0185] determining at least one updated control parameter for operating the power module, and [0186] using the at least one updated control parameter for controlling the power module.

[0187] For example, a switching characteristics and/or a current strength of one or more controllable power components of the power module and the power electronic device, respectively, may be amended to better balance the current and/or the temperature distribution. This may increase the lifetime.

[0188] Estimating the ageing may be based on monitored peak loads and/or integrated loads of the power module and the power components thereof, respectively.

[0189] The monitored loads may refer thermal loads, current loads and combinations thereof.

[0190] Although various exemplary embodiments of the invention have been disclosed, it will be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the spirit and scope of the invention. It will be obvious to those reasonably skilled in the art that other components performing the same functions may be suitably substituted. It should be mentioned that features explained with reference to a specific figure may be combined with features of other figures, even in those cases in which this has not explicitly been mentioned.

[0191] Spatially relative terms such as “under”, “below”, “lower”, “over”, “upper” and the like are used for ease of description to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures. Further, terms such as “first”, “second”, and the like, are also used to describe various elements, regions, sections, etc. and are also not intended to be limiting. Like terms refer to like elements throughout the description.

[0192] As used herein, the terms “having”, “containing”, “including”, “comprising” and the like are open ended terms that indicate the presence of stated elements or features, but do not preclude additional elements or features. The articles “a”, “an” and “the” are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[0193] With the above range of variations and applications in mind, it should be understood that the present invention is not limited by the foregoing description, nor is it limited by the accompanying drawings. Instead, the present invention is limited only by the following claims and their legal equivalents.