A light pipe system

Abstract

A light pipe system 100 for monitoring the temperature of at least one object comprises: a light pipe member (or light guide) 102, having an optically transparent body 104 adapted to transmit electromagnetic radiation between an input end portion 106 and an output end portion 108. At least one opaque input surface member 110 is adapted to absorb a thermal energy received from an object, such as an electronic component, and emit a resultant electromagnetic radiation of a first electromagnetic frequency range e.g. infrared (IR) into the at least one input end portion 106 of the optically transparent body 104. The input surface member 110 may be a surface coating, layer, sheet, film, deposit or film operably coupled to the input end portion and / or the object. The light pipe system may comprise a contact member (112, Fig. 4) such as a fluid configured to operably couple the light pipe member with the object.

Description

Technical Field of Invention The invention relates generally to thermal management in electronics and, in particular, to temperature monitoring of electric components, such as, for example, power electronics, IC’s or semiconductor devices. Even more particularly, the present invention relates to light pipes or light pipe systems utilised for monitoring temperature via photosensors. Moreover, the present invention relates to monitoring devices comprising a light pipe(s) or light pipe system(s) as well as, a housing for encapsulating the object to be monitored. Background Thermal management is one of the key aspects in power electronics, so that electronic components, such as, for example, semiconductor devices (e.g. SiC, IGBT, MOSFET etc.) can operate at optimal conditions to improve overall performance and longevity, as well as efficiency. It is generally known that electronic devices generate heat as a byproduct and if any excess heat is not managed effectively, temperature in these devices will rise leading to early degradation, or beyond, and into thermal run-away and potential catastrophic failure. On the other hand, it is often desirable to operate electronic components in a specific temperature range (e.g. close to the limit) in order to optimise performance characteristics. Consequently, in fields such as, for example, automotive power electronics and aerospace, the electronic components and devices are typically actively cooled utilising pumps and heatsinks. Furthermore, the temperature of the electronic components is monitored to ensure that the devices are working at optimum capacity. However, measuring and monitoring the temperature of electronic components can be difficult, especially when the devices work at high voltages (e.g. in power electronics for traction or generation for power grids). Typical temperature sensors predominantly work at low voltages and are not permitted to get too close to the electronic components (e.g. semiconductor), because the low voltage conductor (i.e. temperature sensor), when placed in a high voltage area, often experiences electrical noise and provides a failure path for catastrophic short circuits. Other issues that may arise when incorporating temperature sensors are caused by the lack of space on the usually tightly packaged PCB (Printed Circuit Board). Moreover, common methods for measuring or monitoring the temperature of electronic components, such as the ones used in power electronics, require electrical isolation of the temperature sensing elements from the high voltage. Consequently, the placement of temperature sensors is typically associated with gaps in the thermal path, reducing the responsiveness to the relatively fast temperature changes (i.e. thermal transients) and significantly limiting the accuracy and resolution of the measurement. However, this can lead to substantial degradation and damage of critical components. One of those critical components might be a IGBT (Insulated-Gate Bipolar Transistor), which is one of the components often used in power electronics. In IGBT’s the correct operating temperature is critical for its function. In Figure 1 a typical temperature measurement setup is illustrated for an IGBT 10 provided on a substrate 12. The sub-optimal placement of the thermistor 14 clearly substantiates the problems mentioned above. In particular, not only is the thermistor 14 located at a distance from the IGBT, but it also requires insulation from the other components, thus, resulting in a thermal gap. So, instead of detecting temperatures changes from the IGBT 10 directly, the thermistor has to first heat up itself before it can detect any temperatures changes in the environment. Consequently, any temperature change is detected somewhat delayed potentially leading to overheating and failure of the IGBT 10. In a typical case several IGBT (or MOSFETs or diodes) may be used in parallel, in this case, each device may be subtly different from the next, or may experience slightly unbalanced load, or insufficient cooling. In this situation, fast thermal transients may be used to understand, monitor and balance the load. The absence of the ability to monitor fast changes allows for degradation of the device experiencing the harsh conditions, thus limiting the life of the device. Therefore, an accurate and suitably responsive temperature measurement is essential, particularly in thermal management of power electronics. Some of the issues mentioned above may be resolved by using non-contact temperature measurement systems, such as, for example, Infrared (IR) thermometers, as well as light guides or light pipes. Here, a light pipe simply conveys the IR radiation away from the region of interest, meaning high voltage regions can be respected. Also, because light pipes can take any form or shape, the temperature sensor may be placed at any convenient location and still provide near instant readout of the IR emissions. Furthermore, the so-called IR light pipes can be used to monitor the temperature of multiple components individually or simultaneously. In addition, when power electronics are packaged, one of the final steps is to coat any device in a thick insulating material. This may be a hard moulded or poured material or a soft gel-like coating. In both cases the coatings are designed to enter small openings. However, this can be problematic for direct optical couplings. Though, as mentioned earlier, utilising a suitably shaped IR light pipe would resolve this issue as it does not require intimate physical contact with the component (e.g. semiconductor). Thus, a non-contact IR temperature sensor coupled with a suitable light pipe provides an ideal temperature monitoring system for multiple semiconductor dies integrated in a high-power semiconductor module. However, when using non-contact light sensors, such as IR sensors, emissivity consistency is challenging, and the electromagnetic radiation “captured” by the light pipe may not be an accurate representation of the object’s temperature. Other known non-contact temperature measurements may include the use of electroluminescence emitted from specific semiconductor devices. For example, it is known that the temperature may be determined from the temperature-dependent changes in the spectrum of the light emission from SiC (Silicon Carbide) dies. The emitted light may be received by a fibre-optic and lead through to a sensor. However, this approach requires the input surface of the fibre-optic to be positioned at a precise location of the die (e.g. SiC MOSFET) and glued to the die light output using an optical glue so that the emitted light can enter the light pipe. Therefore, currently available non-contact temperature monitoring systems are either not accurate enough to provide reliable results, for example, when used arbitrarily in a sealed power electronics setting, or require precise positioning and interfacing (e.g. optical glue) to capture a particular spectrum of an electromagnetic emission (e.g. from electroluminescence), making the available systems neither flexibly applicable nor suitably accurate for fast temperature transients in a high voltage environment. Accordingly, it is an object of the present invention to provide an improved system for determining and monitoring a temperature of an object that is compatible to high voltage environment, easily integrable, adaptable, accurate, as well as, cost effective. Furthermore, it is an object of the invention to provide a temperature monitoring device and a protective housing for at least a part of said device that is cost effective and easily integrable. Summary of the Invention Aspects of the invention are set out in the independent claim(s). Dependent claims describe the optional features. According to a first aspect of the invention, there is provides a light pipe system for monitoring the temperature of at least one object, comprising: a light pipe member, having an optically transparent body with at least one input end portion and an output end portion, adapted to transmit electromagnetic radiation between said input end portion and said output end portion, at least one opaque input surface member, adapted to absorb a thermal energy received from the at least one object and emit a resultant electromagnetic radiation of a first electromagnetic frequency range into said at least one input end portion of said optically transparent body. Such a light pipe system provides the advantage of improved flexibility when incorporating the light pipe into the device, i.e. allowing for arbitrary placement within the proximity of the object of interest. In particular, the input surface member of the light pipe system is adapted to absorb thermal energy of a region of interest (ROI) and emit a predetermined electromagnetic radiation (EMR) spectrum (e.g. IR), thus, providing for a controlled emissivity. Since the emissivity of the input surface member is known, the accuracy of the temperature deduced from the emitted EMR is significantly improved. Furthermore, the input surface member of the light pipe system may be particularly “tuned” into absorbing the thermal energy of the ROI (e.g. a top surface of the electronic component) so that sudden changes of temperature of the object are “transferred” almost instantly to the input surface member. Therefore, rapid temperature changes of the object can be detected easily through the light pipe system. In addition, the light pipe system of the present invention provides the advantage that the light pipe member “facing” the electrical component is an electrical insulator and potential interferences or detrimental effects from the “high-voltage” environment are negligible. Therefore, the light pipe member of the light pipe system may be placed in suitable regions of the device that were not accessible for IR detection previously. Furthermore, the “flexible” positioning of the light pipe member within the device allows for a more simplistic setup without the need for expensive connectors or additional components, thus, significantly reducing the “footprint” of the temperature monitoring system on the PCB (Printed Circuit Board) “real estate” and the overall costs of manufacture. Advantageously, said at least one opaque input surface member is any one of a surface coating, -layer, -sheet, -film, -deposit and -tape operably coupled to said input end portion and / or the at least one object. Advantageously, said at least one opaque input surface member is joined with said input end portion. Alternatively, said at least one opaque input surface member is joined with the object. Advantageously, said at least one input end portion and / or said at least one opaque input surface member are / is spaced apart from the at least one object. Advantageously, said at least one opaque surface input member has an emissivity between 50% and 100%. Preferably, said at least one opaque surface input member has an emissivity greater than 50%. Even more preferably, said at least one opaque surface input member has an emissivity greater than 75%. Yet even more preferably, said at least one opaque surface input member has an emissivity greater than 90%. Yet even more preferably, said at least one opaque surface input member has an emissivity greater than 95%. Advantageously, said first predetermined electromagnetic frequency range is the infrared (IR) spectrum. Preferably, said first predetermined electromagnetic frequency range is between 300 GHz and 400 THz. The use of the infrared spectrum is favourable, because common optical sensors and suitable light pipes or light guides are “tuned” to this frequency range and are therefore readily available reducing the overall complexity and manufacturing costs. Advantageously, said at least one opaque input surface member is adapted to only absorb thermal energy of a predetermined frequency spectrum. This provides the advantage of minimizing “noise” that could affect the accuracy of the temperature measurement. Also, the material transmission spectrum of the input surface member may be adapted to filter out unwanted emissions. Advantageously, said light pipe further comprises a contact member configured to operably couple said light pipe member with the object. Preferably, said contact member is adapted to transfer said thermal energy. Even more preferably, said contact member is a fluid, such as water or oil, and / or a curable fluid, such as a resin or a glue. The use of a fluid or curable fluid contact member (i.e. an interface) allows for an optimized interface between the light pipe member and the object of interest, i.e. the properties of the contact member may maximise the energy received at the input end portion of the light pipe member. Also, using a glue or resin can provide a fixed connection that is robust against displacement due to e.g. vibrations. Advantageously, said body is a solid monolith made of a transparent material such as a transparent polymer or a glass. Therefore, the body is robust and can be manufactured very cost effectively. Advantageously, an outer surface of said body comprises a reflective- or mirror-coating, or has undergone a reflection-enhancing surface treatment, so as to improve internal reflection of said resultant electromagnetic radiation of said first electromagnetic frequency range. Advantageously, said body is formed in any suitable shape configured to optically transmit said resultant electromagnetic radiation of said first electromagnetic frequency range from said input end portion to said output end portion. The option of creating light pipe members of various form, such as a flush cylindrical body, a flush cuboid body, stepped cylindrical body having a slender shaft section and wider foot section formed like a collar, a stepped tilted cylindrical body having the slender shaft section inclined with respect to the vertical direction, a parallelepiped body or a (vi)bent cylindrical body, allows for a significantly increased flexibility when fitting the light pipe body into the device, i.e. the body can be shaped in any suitable form, allowing allow tortuous paths for guiding the electromagnetic radiation from the ROI to the optical sensor. Advantageously, said light pipe further comprises an optical device provided at said output end portion of said optically transparent body. Preferably, said optical device comprises any one of a spherical lens, an aspherical lens, a Fresnel lens surface, and a lens stack. This provides the advantage of optimizing the output direction of the EMR guided through the body and out of the output end portion. Advantageously, said at least one object is an electronic component including any one of a semiconductor component, electric conductor, integrated circuit, high voltage switch, high voltage connector, high current connector and an electric motor. According to another aspect of the invention, there is provided a temperature monitoring device for at least one object, comprising: at least one said light pipe system according to the first aspect of the invention, and at least one optical sensor, operably coupled between the light pipe system and a processing unit, configured to receive an electromagnetic radiation output from said light pipe system. Such a temperature monitoring system can include a plurality of light pipe systems configured to monitor the temperatures of multiple regions of interest (e.g. different components). The various members of the light pipe system, i.e. input surface member, input end portion, contact member and output end portion, can be “tuned in” to optimize the light pipe system for a specific use. According to yet another aspect of the invention, there is provided a housing for encapsulating at least one object, comprising at least one said light pipe system according to the first aspect of the invention, and configured to operably position said at least one light pipe system for monitoring the temperature of an object. Advantageously, said housing further comprises at least one aperture configured to operably and retainingly receive at least a body of said light pipe system. Such a housing provides the advantage that, for example, electrical components can be arranged on a PCB at fixed positions for an optimised footprint, while providing easy access to one or more desired components for temperature monitoring via one or more light pipe members suitably couped within the housing and configured to transmit an EMR from the input end portion to the output end portion (outside of the housing). This allows for a compact and robust arrangement, with an easy access for monitoring the temperature using optical sensors outside the housing. Brief Description of Drawings Example embodiment(s) of the invention are illustrated in the accompanying drawings, in which: Figure 1 shows a known example set up for measuring the temperature of an IGBT incorporated on a housed PCB; Figure 2 is a simplified illustration of an example embodiment of the light pipe system of the present invention with the input surface member incorporated at the input end portion of the light pipe body; Figure 3 illustrates an example application of the light pipe system arranged so as to monitor a plurality of objects (electronic components) on a PCB (a) an overall view of the arrangement and (b) a close-up view of one light pipe system operably placed to receive the thermal energy from an electric component; Figure 4 shows examples of different embodiments of the light pipe system of the present invention (a) a light pipe member with the input surface member provided at the input end portion and spaced apart from the object, (b) a light pipe member with the input surface member provided at the input end portion and spaced apart from the object and a fluid or cured fluid provided therebetween, (c) a light pipe member with the input surface member provided at the object (e.g. a coating or tape on the housing of the electrical component) and the light pipe member spaced apart from the object, and (d) a light pipe member with the input surface member provided at the object (e.g. a coating or tape on the housing of the electrical component) and the light pipe member spaced apart from the object and a fluid or cured fluid provided therebetween; Figure 5 shows (a) a perspective example illustrations of tortuous shaped light pipe body, as well as partial views of the output end portion of the light pipe member with different optical devices, such as (b) including a curved exit surface (lens), (c) including a Fresnel lens exit surface, and (d) including a shrouded exit (i.e. opaque barrier to crosstalk); Figure 6 (a) shows a perspective illustration of a cluster of electronic components and operably arranged light pipes of various shapes; Figure 7 is a schematic illustration of the light pipe system when used for monitoring the temperature of semiconductors, (a) monitoring a single electric component via a single light pipe system and photosensor (IR) arranged at a safe distance from the electric component (e.g. semiconductor) and (b) monitoring a plurality of electric components via a light pipe array with multiple input end portions and multi-pixel photosensors arranged at a safe distance from the electric component (e.g. semiconductor); Figure 8 is an illustration of a housing for electric components (e.g. on a PCB) including a plurality of light pipe systems, (a) in a perspective top view and (b) in a transparent perspective top view, and Figure 9 shows a graph of the emitted energy vs. wavelength [pm] for different temperature curves. Description The described example embodiment(s) relates to a light pipe system, and in particular, a temperature monitoring device for electronic components, such as, used in housed power electronics used for vehicles, as well as a housing for encapsulating power electronics (such as used in the automobile industry) including one or more light pipe systems for monitoring the temperature of one or more electronic components. Certain terminology is used in the following description for convenience only and is not limiting. The words ‘right’, ‘left’, ‘lower’, ‘upper’, ‘front’, ‘rear’, ‘upward’, ‘down’, ‘downward’, ‘above’, ‘below’ designate directions in the drawings to which reference is made and are with respect to the described component when assembled and mounted (e.g. in situ). The terms ‘inner’, ‘inwardly' and ‘outer’, ‘outwardly’ refer to directions toward and away from a designated centreline or a geometric centre of an element being described (e.g. central axis), the particular meaning being readily apparent from the context of the description. Further, as used herein, the terms ‘connected', ‘attached’, ‘coupled’, ‘mounted’ are intended to include direct connections between two members without any other members interposed therebetween, as well as indirect connections between members in which one or more other members are interposed therebetween. The terminology includes the words specifically mentioned above, derivatives thereof, and words of similar import. The terms ‘light pipe’ and ‘light pipe’ are used interchangeably, also, the term ‘input surface member’ is understood to include any one of a surface coating, a surface paint, a surface with a predetermined emissivity due to specific material properties, a surface layer or surface sheet, a surface film, a surface deposit, or a surface tape. Further, unless otherwise specified, the use of ordinal adjectives, such as, ‘first’, ‘second’, ‘third’ etc. merely indicate that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner. Through the description and claims of this specification, the terms ‘comprise’ and ‘contain’, and variations thereof, are interpreted to mean ‘including but not limited to’, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality, as well as, singularity, unless the context requires otherwise. Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract or drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. Although the example described is aimed to housed and encapsulated power electronics devices used in the automobile industry, it is understood by the person skilled in the art that the invention is equally applicable to monitor the temperature of other components or in other fields (e.g. aerospace etc.). An example embodiment of the light pipe system 100 is now described with reference to Figure 2. In this particular embodiment, the light pipe system 100 comprises a light pipe member 102 (may also be referred to as light guide) that is made from a material adapted to optically transmit electromagnetic radiation (EMR) of a predetermined frequency spectrum. In this particular example, the EMR is in the infrared spectrum (IR) and may simply be called IR radiation. Depending on the frequency, photons or electrons travel on different wavelengths trough the light pipe. The light pipe member 102 comprises a light pipe body 104 having an input end portion 106 and an output end portion 108 and being configured to convey (transmit) the IR radiation by inner reflection from the input end portion 106 to the output end portion 108. The light pipe body 104 may be made from a solid monolith made of a transparent material such as a transparent polymer or a glass. In order to optimize optical transmission through the body 104, the outer surface of the body 104 may be provided with a reflective or mirror-coating. Alternatively, the body 104 may undergo a reflection-enhancing surface treatment so as to improve the internal reflection of the IR radiation travelling through the body 104. The body 104 may have any shape or design suitable to transmit IR radiation from the input end portion 106 to the output end portion 108. Therefore, the light pipe system 100 can be customised to its application and environment so as to reach previously inaccessible areas of a housed power electronics device. The light pipe system 100 comprises an input surface member 110 that is adapted to absorb thermal energy from a targeted region of interest (e.g. a top surface of a semiconductor device such as an IGBT integrated on a PCB) and emit IR relation into the input end portion 106 to be transmitted to the output end portion 108 of the light pipe body 104. At the output end portion 108 the IR radiation is received by a photosensor (not shown) where this converted into a temperature. Figure 3 shows the light pipe system 100 in use with multiple electronic components 112 (i.e. the objects of interest) arranged on a substrate 144 and / or PCB 140. Here, the light pipe system is simply positioned over or near (or in contact with) the electrical component 112 so that the input surface member 110 can receive and absorb the thermal energy produced in the electric component 112 and emit a corresponding IR radiation into the body 104 for transmission to the photosensor (not shown). As is shown in Figure 3(a) and 3(b), the light pipe system 100 may be positioned spaced apart from the targeted component 112 or in direct contact with the targeted component 112. The light pipe system 100 may be provided in different embodiments to suit different setups for monitoring the temperature of electronic components 112. These variants of the light pipe system 100 may be categorised into embodiments (a) to (d) as shown in Figure 4. In particular, the light pipe system 100 may be provided with the input surface member 110 coupled to the input surface portion 106 of the light pipe body 104 (see Figure 4(a) and (b)). In another embodiment, the input surface member 110 is spaced apart from the input end portion 106 of the light pipe body 104 and coupled with the object or electrical component 112 (see Figure 4 (c) and (d)). For example, a suitable coating or tape or layer, adapted to absorb the thermal energy of the component 112 and emit a corresponding IR radiation, may be attached to or incorporated with the input end portion 106 of the body 104. In use, the light pipe system 100 is simply positioned over the object 112 to absorb the thermal energy of the target area. Additionally, and as illustrated in Figure 4(b), a contact member in the form of a fluid 116 or curable fluid may be used between the light pipe member 102 and the object 112 as interface and / or fixation. In particular, a fluid 116, such as, water or oil may be used to optically and / or thermally couple the lightpipe system 100 to the object 112 thus, providing an improved interface between the object 112 and the light pipe system. Alternatively, a curable fluid 116, such as a resin or a glue, may be used to simultaneously fixate the light pipe system with the object 112. In an alternative embodiment, as shown in Figures 4 (c) and (d), the input surface member 110 may be provided separate from the light pipe body 104. In particular, the input surface member 110, such as, but not limited to a coating, paint, tape, layer etc., may be coupled with or be an integral part of a target surface of the object 112. For example, a tape or coating is attached to the top surface of an electrical component 112 (e.g. a top surface of the components housing), or the housing of the component 112 itself is utilised as a suitable input surface member 110, i.e. it has suitable properties to absorb the thermal energy generated by the electrical component 112 and then emit an IR radiation that can be received through the input end portion 106 of the light pipe member 102. Additionally and as illustrated in Figure 4 (d), a contact member in the form of a fluid 116 or curable fluid 116 may be used between the light pipe body 104 (i.e. the input end portion 106) and the input surface member 110 provided at the object 112 as interface and / or fixation. In particular, the fluid 116, such as, water or oil may be used to optically and / or thermally couple the input end portion 106 of the light pipe body 104 to the input surface member 110 of the object 112, thus, providing an improved interface between the object 112 and the light pipe system 100. Alternatively, the fluid may be a curable fluid 116, such as a resin or a glue, and may be used to simultaneously fixate the light pipe system with the object 112. Any one of the embodiments shown in Figures 4(a) to (d) provides for a controlled emissivity of the input into the light pipe member 102, allowing for a much improved accuracy of temperature measurements of an object arbitrarily positioned in a non-contact arrangement or in a contacting arrangement via a fluid member 116. Further, in the example embodiment, the input surface member 110 may be formed of a surface coating with thickness of roughly 500 pm, though, within the surface structure the thickness may vary due to manufacturing tolerances. The various surface structures can be customised for a specific application in such a way that the optimum transmission of the thermal energy is achieved. The target object 112 may have a known emissivity, so that the evaluation device can be “tuned” to the IR radiation received from the output end portion 108. Also, the input surface member 110 may be adapted to enhance the performance of the light pipe system 100 by “shaping” the IR radiation emitted into the light pipe body 104. This may be achieved by an input surface member 110 adapted to only absorb thermal energy of a predetermined frequency band. Also, the input surface member 110 may be adapted to filter or supress unwanted noise and thus improve the quality of the IR radiation emitted into the light pipe member 102. Depending on the application, a filter with a bandpass, lowpass or high-pass characteristic may be used. Figure 5 illustrates various output end portions 108 of the light pipe member 102 configured to optimise the optical interface between the light pipe output 108 and the photosensor used to determine the temperature from the IR radiation received from the input surface member 110. The output end portion 108 may comprise any one of a spherical or aspherical lens 120, a Fresnel lens 122 or a crosstalk barrier 124 in the form of an opaque pipe partially sheathing the output end portion 108 and extending beyond the light pipe body 104 so as to form a shrouded exit (see Figure 5(d)), which allows the use of multiple light pipe members 102, simultaneously. Figure 6 illustrates different shapes the light pipe body 104 in use. In particular, a differently shaped light pipe body 104 is used for each one of a plurality of electrical components 112 arranged in a unit. The different shapes include a flush cylindrical body 126 extending vertically relative to the component 112, a flush cuboid body 128 extending vertically relative to the component 112, a stepped cylindrical body 130 extending vertically relative to the component 112 and comprising a slender shaft section and wider foot section formed like a collar 132, a stepped cylindrical body 134 inclined away from a foot section, a stepped parallelepiped body 136, where the shaft section inclines away from a cuboid foot section, and a curved cylindrical body 138 extending away from the component 112. Figure 7(a) illustrates an example arrangement of the light pipe system 100 when used in a typical power electronics device including a semiconductor 112 provided on a substrate 144 and covered or encapsulated with a suitable housing 114. A photosensor 142 (e.g. incorporated on a PCB 140) is suitably positioned at the light pipe output end portion 108 so as to receive the emitted IR radiation. The lightpipe member 102 may simply be passed through an aperture of the housing 114, or may be integrated with the encapsulating housing 114 at predetermined positions, so that IR radiation is transmitted from the component 112 inside the housing 114 to the sensor 142 outside the housing 114 via the output end portion 108. Figure 7(b) shows a variation of the light pipe system 100 with multiple input end portions 106, each one suitably positioned for a different component 112. This arrangement allows for simultaneous monitoring of multiple components 112, e.g. by using a multipixel sensor 148. The multipixel sensor 148 is configured to detect more than one stream of radiation. Using the fact that radiation coupled in from different areas of a light pipe 102 do not interfere with each other. Referring now to Figures 8(a) and (b), a housing 114 with integrated light pipe system(s) 100 is provided for a typical power electronics set up, e.g. a housing 114 for a PCB including various components 112 that require temperature monitoring. Especially in the automotive industry, circuitry and other electronic systems must be protected from environmental factors to avoid damage, therefore, suitable housings are used to protectively and sealingly encapsulate the components 112. However, the sealing nature of these housings makes it difficult to monitor the temperature of the encapsulated components. In an embodiment of the present invention, a housing 114 is provided with one or more integrated light pipe system(s) 100. The apertures for the output end portion 108 of the light pipe member 102 can be provided at any suitable location of the housing 114, because the light pipe bodies 104 can be suitably shaped so as to reach a predetermined target region of one or more components 112. During use, a suitable embodiment of the light pipe system 100 is simply positioned in the vicinity of the target object 112, either at a predetermined distance form the component 112 or coupled via a fluid member 116. Alternatively, a housing 114 with integrated light pipe system(s) 100 is used to cover the target object(s). An optical sensor 142 coupled to a suitable processing unit 142 is positioned so as to receive the IR radiation through the output end portion 108 of the light pipe member 102. When operating the electronic components 112, thermal energy is generated which is absorbed by the input surface member 110, either through conduction or radiation. The absorbed energy causes the input surface member 110 to emit IR radiation which is coupled into the light pipe body 104 and transmitted to the output end portion 108, where it is received by the photosensor 142. The target objects 112 may be a semiconductor component as used in power electronics, especially in the automotive or aerospace industry, or any other electronic component like an electric conductor, integrated circuit, high voltage switch, high voltage connector, high current connector or electric motor. The contact member 116 may enhance the transmission performance of the electromagnetic radiation into the light pipe body 104 by bundling the rays. An example of a suitable frequency range 150 is shown in Figure 9, which is the infrared (IR) spectrum (i.e. frequencies between 300 GHz and 400 THz). However, any other suitable frequency range may be used to determine the temperature of an object 112. It will be appreciated by persons skilled in the art that the above embodiment(s) have been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departing from the scope of the invention as defined by the appended claims. Various modifications to the detailed designs as described above are possible, for example, variations may exist in shape, size, arrangement, assembly or the like. Reference numbers: 10 IGBT 12 IGBT substrate 14 Thermistor 16 Housing 100 Light pipe system 102 Light pipe member 104 Light pipe body 106 Input end portion 108 Output end portion 110 Input surface member 112 Object 114 Housing 116 Contact member 118 Tortuous cylindrical body 120 spherical lens structure 122 Frensel-lens structure 124 crosstalk barrier 126 cylindrical body 128 cuboid body 130 stepped cylindrical body 132 collar 134 stepped tilted cylindrical body 136 stepped parallelepiped body 140 control PCB 142 optical sensor (I R sensor) 144 Substrate 146 Array 148 Multipixel sensor 150 Wavelength range

Claims

1. A light pipe system for monitoring the temperature of at least one object, comprising:a light pipe member, having an optically transparent body with at least one input end portion and an output end portion, adapted to transmit electromagnetic radiation between said input end portion and said output end portion,at least one opaque input surface member, adapted to absorb a thermal energy received from the at least one object and emit a resultant electromagnetic radiation of a first electromagnetic frequency range into said at least one input end portion of said optically transparent body.

2. A light pipe system according to claim 1, wherein said at least one opaque input surface member is any one of a surface coating, -layer, -sheet, -film, -deposit and -tape operably coupled to said input end portion and / or the at least one object.

3. A light pipe system according to claim 2, wherein said at least one opaque input surface member is joined with said input end portion.

4. A light pipe system according to claim 2, wherein said at least one opaque input surface member is joined with the at least one object.

5. A light pipe system according to any one of the preceding claims, wherein said at least one input end portion and / or said at least one opaque input surface member are / is spaced apart from the at least one object.

6. A light pipe system according to any one of the preceding claims, wherein said at least one opaque surface input surface member has an emissivity between 50% and 100%.

7. A light pipe system according to claim 6, wherein said at least one opaque surface input member has an emissivity greater than 50%.

8. A light pipe system according to claim 7, wherein said at least one opaque surface input member has an emissivity greater than 75%.

9. A light pipe system according to claim 8, wherein said at least one opaque surface input member has an emissivity greater than 90%.

10. A light pipe system according to claim 9, wherein said at least one opaque surface input member has an emissivity greater than 95%.

11. A light pipe system according to any one of the preceding claims, wherein said first predetermined electromagnetic frequency range is the infrared (IR) spectrum.

12. A light pipe system according to claim 11, wherein said first predetermined electromagnetic frequency range is between 300 GHz and 400 THz.

13. A light pipe system according to any one of the preceding claims, wherein said at least one opaque input surface member is adapted to only absorb thermal energy of a predetermined frequency spectrum.

14. A light pipe system according to any one of the preceding claims, further comprising a contact member configured to operably couple said light pipe member with the object.

15. A light pipe system according to claim 14, wherein said contact member is adapted to transfer said thermal energy.

16. Alight pipe system according to any one of claims 14 and 15, wherein said contact member is a fluid, such as water or oil, and / or a curable fluid, such as a resin or a glue.

17. A light pipe system according to any one of the preceding claims, wherein said body is a solid monolith made of a transparent material, such as a transparent polymer or a glass.

18. A light pipe system according to any one of the preceding claims, wherein said body comprises a plurality of input end portions, each one configured to correspond to a respective one of the at least one object.

19. A light pipe system according to any one of the preceding claims, wherein an outer surface of said body comprises a reflective- or mirror coating, or has undergone a reflection-enhancing surface treatment, so as to improve internal reflection of said resultant electromagnetic radiation of said first electromagnetic frequency range.

20. A light pipe system according to any one of the preceding claims, wherein said body is formed in any suitable shape configured to optically transmit said resultant electromagnetic radiation of said first electromagnetic frequency range from said input end portion to said output end portion.

21. A light pipe system according to any one of the preceding claims, further comprising an optical device provided at said output end portion of said optically transparent body.

22. A light pipe system according to claim 21, wherein said optical device comprises any one of a spherical lens, an aspherical lens, a Fresnel lens surface and a lens stack.

23. A light pipe system according to any one of the preceding claims, wherein the at least one object is an electronic component including any one of a semiconductor component, electric conductor, integrated circuit, high-voltage switch, high voltage connector, high-current connector and an electric motor.

24. A temperature monitoring device for at least one object, comprising:at least one light pipe system according any one of the preceding claims, andat least one optical sensor, operably coupled between said light pipe system and a processing unit, configured to receive an electromagnetic radiation output from said light pipe system.

25. A housing for encapsulating at least one object, comprising at least one light pipe system according to any one of the claims 1 to 23 and configured to operably position said at least one light pipe system for monitoring the temperature of the object.

26. A housing according to claim 25, further comprising at least one aperture configured to operably and sealingly retainingly receive at least a body of said light pipe system.

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