AbstractThis paper presents a 75W single-stage power supply unit for LED lighting. The proposed power supply designed using flyback converter topology that is controlled by the critical conduction mode control. The secondary side of main transformer is directly connected to LED strings. By a constant current feedback circuit, this flyback converter directly regulates LED current. Although the proposed circuit doesn’t need input current-sensing and input voltage feed-forward, it can achieve high power factor for wide input range. A prototype experimental set-up has been built and tested. Through this experiment with a prototype set-up, the validity of the proposed circuit is verified.
1. Introduction
In recent years, LED technology has been grown rapidly and it is considered as a most strong candidate for the next generation lighting source due to high energy efficiency, long life time and its positive environmental attributes. Moreover, LED technology controls the color, shape, illumination pattern as well as light itself [1]. In the case of indoor or street LED lighting application, a power supply unit(PSU) that converts AC input voltage to DC output voltage is necessary and various topologies have being considered [2-4]. The PSUs for low power LED lighting are normally single-stage converter types but two stage converters are common for a high power LED lighting applications due to their power limitation. In this paper a single-stage PSU for high power LED lighting is presented. As the power converter circuit, flyback converter topology is applied because it doesn’t need an inductive output filter, the main transformer works as an inductive filter itself and the input and output stages can be isolated [5, 6]. The proposed circuit used a critical conduction mode (CRM) PFC controller and the input voltage and switching current are not needed, the only output voltage feed-back is necessary. Through an experiment with a prototype 75W single stage flyback converter, the feasibility of the proposed single stage PSU, control scheme and feedback methods are examined and discussed in this paper.
2. Single Stage Flyback Converter for LED
2.1 Fundamental analysis
Figure 1 shows the circuit diagram of a flyback AC-DC converter. Both CV(constant voltage) and CC(constant current) feedback circuit are needed to prevent overload condition as well as over voltage conditions. In LED lighting, the output is always full load condition and the forward voltage drop of LED will be decreased in accordance with the increasing junction temperature of LED. Therefore the output should be controlled by CC mode in the normal state while CV mode only acts as over voltage protection.
Fig. 1. Circuit diagram of a flyback AC-DC converter
A voltage mode CRM PFC controller, FAN7530 is used as a control IC and the internal block diagram is shown in Figure 2. In the control circuit, the switching signal is generated by comparing the output of the error amplifier with the internal ramp signal. Consequently, the input voltage and current are unnecessary. The turn-on time of switch is fixed while the turn-off time is varied during the steady state. Therefore, the switching frequency inevitably varies in accordance with the input voltage variation as shown in Figure 3.
Fig. 2. Block diagram of FAN7530
Fig. 3. Switching frequency variation
Figure 4 illustrates the theoretical waveforms of the primary side switch current, the secondary side diode current and gating signal. MOSFET, Q turns on and FRD, Do turns off under zero-current condition while Q turns off and Do turns on under the hard switching condition.
Fig. 4. Theoretical waveforms
In flyback converter, the transformer will be easily saturated because the transformer is only utilized within 1st quadrant. Moreover if it works under the critical conduction mode, the peak current is much higher than that of the continuous conduction mode. Therefore the air-gap should be inserted to prevent the saturation of the transformer. When a flyback converter is applied to the single stage AC-DC converter, the proper turn ratio, N2/N1, is very important because the maximum voltage rating of MOSFET and FRD strongly relates with the turn ratio of transformer. There is a trade off relationship between the drain to source voltage rating, Vdss, of MOSFET and the reverse voltage rating, VR of FRD according to the turn ratio of the transformer. The larger turn ratio requires the higher DC reverse voltage, VR of FRD while the drain-source voltage, Vdss, of MOSFET is decreased. In contrast, the lower turn ratio causes the higher voltage stress of MOSFET while VR of FRD is decreased.
Figure 5 shows the trade-off relationship between Vdss, of MOSFET and VR of FRD. From Po=ηVinIin, the maximum input current, Iin(max) = Po/ηVin. If the switching frequency, fs is much higher than the AC line frequency, fac, the input current can be assumed to be constant during a switching period.
Fig. 5. VDS and VR in accordance with turn ratio
In order to define the magnetizing inductance of transformer, the longest period has to be defined. The longest switching period occurs at the peak point of the input current when the minimum input voltage is applied. The maximum input current and the switching peak current is defined as follow;
Where, respectively.The transformer primary side voltage, VT is defined as follow;Therefore, the magnetizing inductance is obtained as follow;The voltage stress of MOSFET is
Table 1. Electrical parametersParameters ValueOutput Power 75WInput Voltage Range 85-265VOutput Voltage 45VLimited output voltage 50VTurn ratio (N2/N1) 17/44Magnetizing inductance 297uHMinimum switching frequency, fs_min@ Vin_min 50kHzEfficiency, η 85 %
where Vsn is the maximum capacitor voltage of the snubber circuit, Vf (N1Vo/N2) is the flyback voltage and VLr is the ringing voltage at the leakage inductance of the transformer respectively. Normally VLr is estimated as 1.5 times of the flyback voltage. The maximum reverse voltage and the forward peak current of FRD arerespectively.
2.2 Snubber circuit design
In flyback converter, the resonant between Lleak and Coss occurs an excessively high voltage surge which causes the damage of MOSFET during the turn-off instant. This voltage surge has to be suppressed and the snubber circuit is therefore necessary to prevent MOSFET failures as shown in Figure 6.The clamping voltage by snubber is Fig. 6. Snubber circuit designThe maximum power dissipation of the snubber circuit is determined by and, the maximum power dissipation isWhere, vc=Vf +Vsn. Therefore, the resistance, Rsn is determined byThe maximum ripple voltage of snubber circuit is obtained as follow; The larger snubber capacitor results the lower voltage ripple, but the power dissipation will be increased. Consequently, selecting the proper value is important. In general, it is reasonable to determine that the snubber voltage is 1.5 times of the flyback voltage and the ripple voltage is 50V.
3. Experimental Results
To verify the validity of the proposed circuit, a prototype 75W experimental set-up has been built and tested.
The photograph of experimental set-up is shown in Figure 7. The electrical parameters are listed in Table 1. Figure 8 shows the experimental waveforms of VGS, VDS and Id at 110Vac input and at 220 Vac input respectively, which shows the switching current waveforms follow the sharp of the input voltage well. Figure 9 shows the input voltage and current at 110 Vac input and 220 Vac input conditions. The power factors at 110 Vac and 220 Vac condition are measured as 0.997 and 0.955 respectively.
Fig. 7. Photograph of 75W prototype experimental set-up
Table 1. Electrical parameters
Parameters ValueOutput Power 75WInput Voltage Range 85-265VOutput Voltage 45VLimited output voltage 50VTurn ratio (N2/N1) 17/44Magnetizing inductance 297uHMinimum switching frequency, fs_min@ Vin_min 50kHzEfficiency, η 85 %
Fig. 8. Experimental waveforms of VGS, VDS and Id
Fig. 9. Experimental waveforms of input voltage and current
To suppress the surge voltage of MOSFET caused by the resonant between Lleak and Coss, RCD snubber circuit is necessary. The snubber voltage is estimated as 1.5 times of the flyback voltage and the ripple voltage is estimates as 50V. The snubber resistor and capacitor are determined by following equations;
From the result, 3 × 2W 71kΩ resistors, 4.7nF/1kV capacitor and UF4005(UFRD) are finally chosen for the snubber circuit. Figure 10 shows the waveforms of the drain-source voltage and current when the AC input voltage is 265V, the maximum voltage. The voltage ripple is measured as 54V and the maximum voltage stress is 720V, which shows the actual results are approximately in accord with the calculation. However, the maximum voltage is 720V, 800V rating MOSFET is consequently needed for wide input voltage range. Figure 11 shows the waveforms of the output voltage and current for load variation. The output voltage ripple at 100%, 75%, 50% and 25% load condition is 1.76V, 1.37V, 0.94V and 0.49V respectively. The maximum ripple at 100% load condition is 3.67% of the normal output DC voltage and the 120Hz current ripple is observed. However, since the output current is continuous and the ripple frequency, 120Hz is sufficiently high, the flicker phenomenon is invisible to human eyes. The efficiency characteristics according to the load variation for the input voltages, 110 Vac, and 220 Vac conditions are plotted in Figure 12. The maximum efficiency is measured as 85.17% at the middle load condition in the case of 110Vac input and 85.95% at full-load condition in case of 220Vac input respectively. Figure 13 shows a CV and CC mode feedback circuit applied to the prototype single stage flyback converter experimental set-up for LED lighting. Since the forward voltage drop of LED decreases as the junction temperature increases, LED strings have to be driven by the constant current mode. Figure 14 shows the V-I characteristics of the prototype experimental set-up. From the result, it is clearly verified that the output is driven well by the constant current control for whole input voltage condition.
Fig. 10. Drain-source voltage and switching current at 265Vac input condition
Fig. 11. Output voltage and current for load variation
Fig. 12. Efficiency comparison
Fig. 13. Constant current and constant voltage feedback circuit
Fig. 14. Output V-I characteristic
4. Conclusion
In this paper, a single stage flyback converter for the high power LED lighting applications is presented and its operation principal was analyzed. Even though the circuit has simple structure, it can achieve high power factor, over 0.95, for whole input voltage condition. To verify the validity of the single stage flyback converter for LED lighting, an experimental set-up was built. As a result, the maximum power factor is 99.7% and the maximum efficiency is 85.95% respectively.
Wednesday, May 19, 2010
Cree Partnership to Bring LED Lights to New Habitat for Humanity Homes
Cree, Inc. and Habitat for Humanity International announce a three-year, $1.5 million pledge to provide high-efficiency Cree LED downlights for the kitchens in all new Habitat homes built in the United States.
The Cree LED kitchen lighting packages can help reduce energy costs for Habitat homeowners, as kitchens generally see some of the highest lighting energy usage in a home, according to ENERGY STAR®.
More than 1,500 Habitat for Humanity affiliates across the U.S. will have access to the lighting package, which features Cree’s newest LED downlight, the CR6™ downlight. The CR6 downlight is designed to last 50,000 hours, which is more than 22 years if the lights are used six hours a day.
These LED downlights exceed ENERGY STAR criteria, consuming 85-percent less energy than an incandescent and 55-percent less energy than a compact fluorescent.
Jonathan Reckford, the CEO of Habitat for Humanity International, noted that Cree is partnering with Habitat affiliates to provide lighting products that enable more energy-efficient homes. Products and materials that reduce energy costs make homes even more affordable for Habitat partner families and also help to protect the environment. This is going to make a huge impact in helping the company develop sustainable communities.
The Cree LED kitchen lighting packages can help reduce energy costs for Habitat homeowners, as kitchens generally see some of the highest lighting energy usage in a home, according to ENERGY STAR®.
More than 1,500 Habitat for Humanity affiliates across the U.S. will have access to the lighting package, which features Cree’s newest LED downlight, the CR6™ downlight. The CR6 downlight is designed to last 50,000 hours, which is more than 22 years if the lights are used six hours a day.
These LED downlights exceed ENERGY STAR criteria, consuming 85-percent less energy than an incandescent and 55-percent less energy than a compact fluorescent.
Jonathan Reckford, the CEO of Habitat for Humanity International, noted that Cree is partnering with Habitat affiliates to provide lighting products that enable more energy-efficient homes. Products and materials that reduce energy costs make homes even more affordable for Habitat partner families and also help to protect the environment. This is going to make a huge impact in helping the company develop sustainable communities.
LED Market Explosion Will be Hampered by Materials Shortage
Fast-growing market for high-brightness LEDs in LCD TVs will be restricted by a shortage of key semiconductor materials in the second half of 2010, according to a report.
The paper points out that demand has soared with the rapid penetration of LED backlighting modules in LCD TVs. This has also lead to a soaring demand for capital equipment, especially metal-organic chemical vapor deposition (MOCVD) reactors used to make gallium nitride (GaN) LEDs.
The similar trend is now evident in the supply of consumables, specifically the metal-organic material trimethylgallium(TMG) and sapphire wafers. The demand for TMG already exceeds the available supply, therefore manufacturers need to absorb a 20% price increase in the near term.
The paper also predicts that a shortage of sapphire wafers, upon which most blue and white LEDs are produced, is also likely in the second half of 2010. And Taiwan LED manufacturers in particular need to adjust to the new reality of the supply chain. Historically, they have bargained for the price of these key materials.
However, the balance of power in the LED industry has changed, with competitors backed by huge corporations, such as Samsung and LG, much better positioned to absorb higher material costs and to guarantee their supply in a constrained market.
Capacity expansions already in progress should relieve these constraints by mid-2011. Until then, the average selling price of high-brightness LEDs based on gallium nitride should hold up well, according to the predict.
The paper points out that demand has soared with the rapid penetration of LED backlighting modules in LCD TVs. This has also lead to a soaring demand for capital equipment, especially metal-organic chemical vapor deposition (MOCVD) reactors used to make gallium nitride (GaN) LEDs.
The similar trend is now evident in the supply of consumables, specifically the metal-organic material trimethylgallium(TMG) and sapphire wafers. The demand for TMG already exceeds the available supply, therefore manufacturers need to absorb a 20% price increase in the near term.
The paper also predicts that a shortage of sapphire wafers, upon which most blue and white LEDs are produced, is also likely in the second half of 2010. And Taiwan LED manufacturers in particular need to adjust to the new reality of the supply chain. Historically, they have bargained for the price of these key materials.
However, the balance of power in the LED industry has changed, with competitors backed by huge corporations, such as Samsung and LG, much better positioned to absorb higher material costs and to guarantee their supply in a constrained market.
Capacity expansions already in progress should relieve these constraints by mid-2011. Until then, the average selling price of high-brightness LEDs based on gallium nitride should hold up well, according to the predict.
Applied Materials to Enter MOCVD Market Soon
According to a report, Applied Materials plans to enter MOCVD market as a new MOCVD equipment supplier as the company responds to soaring demand from consumers and OEMs for LED backlit TVs.
Applied Materials may in fact be looking to produce an HPVE and MOCVD combined system. The company was awarded $3.9 million from the DOE through the American Recovery and Reinvestment Act to reduce the costs of LED manufacturing by improving manufacturing equipment and processes. A portion of this money, some estimate $2.4 million, will go towards producing a more cost effective MOCVD system for producing LED, and the final manufacturing is likely to be done in Singapore or Taiwan.
Applied Materials may in fact be looking to produce an HPVE and MOCVD combined system. The company was awarded $3.9 million from the DOE through the American Recovery and Reinvestment Act to reduce the costs of LED manufacturing by improving manufacturing equipment and processes. A portion of this money, some estimate $2.4 million, will go towards producing a more cost effective MOCVD system for producing LED, and the final manufacturing is likely to be done in Singapore or Taiwan.
Cleveland City Council Delays Vote on Contract with Chinese LED Fixture Maker
It’s reported that Cleveland, Ohio's mayor, Frank Jackson, announced to delay vote on LED fixture contract with Sunpu-Opto Semiconductor Ltd.
Sunpu-Opto Semiconductor Ltd., a chinese LED fixture maker, is said to be a Cleveland's exclusive supplier of LED streetlights, traffic lights, and fluorescent tube replacements for nearly $10 million. In exchange the company agreed to relocate its North American headquarters to Cleveland, bringing 350 jobs. The City Council had to vote on the deal before the plan was approved. The Cleveland city council voted to delay the vote.
Many of members of the city council expressed concerns that the contract would not be given to a U.S.-based company. At the city council meeting, some competitors noted that the lighting contract does not include competitive bidding, which is illegal under the current city charter.
Sunpu-Opto Semiconductor Ltd., a chinese LED fixture maker, is said to be a Cleveland's exclusive supplier of LED streetlights, traffic lights, and fluorescent tube replacements for nearly $10 million. In exchange the company agreed to relocate its North American headquarters to Cleveland, bringing 350 jobs. The City Council had to vote on the deal before the plan was approved. The Cleveland city council voted to delay the vote.
Many of members of the city council expressed concerns that the contract would not be given to a U.S.-based company. At the city council meeting, some competitors noted that the lighting contract does not include competitive bidding, which is illegal under the current city charter.
Lithonia Lighting enters LED Lighting Market with introduction of RTLED
Lithonia Lighting, an Acuity Brands company based in Atlanta, Georgia USA, has introduced the new product RTLED and announced that Lithonia Jumps into LED lighting market.
RTLED is a volumetric recessed luminaire that delivers ambient white light throughout an entire space. RTLED boasts 50,000 hours of light without having to replace lamps or ballasts, thereby reducing downtime.
Lithonia says that the luminaire adjusts itself to eliminate the waste of over lighting. Also, the RTLED tracks its own operating hours and provides a visual indicator when the luminaire has reached the end of its service life.
RTLED is a volumetric recessed luminaire that delivers ambient white light throughout an entire space. RTLED boasts 50,000 hours of light without having to replace lamps or ballasts, thereby reducing downtime.
Lithonia says that the luminaire adjusts itself to eliminate the waste of over lighting. Also, the RTLED tracks its own operating hours and provides a visual indicator when the luminaire has reached the end of its service life.
W. C. Heraeus introduces its Stamped Circuit Board technology
Thermal Management for IC/PCB/LED Lower cost heat removal Heraeus has entered the stage front-on with its Stamped Circuit Board technology – a fully comprehensive concept for thermal management.
Basically, it means that heat can be drawn away from beneath the chip far more quickly, reliably and cheaply. A series of tests at the Fraunhofer IZM confirm that the technology contains an enormous amount of potential. Stamped Circuit Board (SCB) technology combines structured layers of metal and plastic for use in substrate assemblies, e. g. of LEDs.
Similar to printed circuit boards, this layering may consist of fiberglass-reinforced epoxy resin and copper – however, the separate structuring of the two materials opens the way for totally new design concepts.
During the manufacturing process both the plastic and the metal are initially treated on separate reels and structured according to the specific requirements involved.
At the next stage, the materials undergo lamination after which they are left perfectly aligned to each other. Advantages of SCB technology Light flux, efficiency and durability of LEDs depend very much on the junction temperature of the actual LED itself. A rising component temperature has a negative effect on the service life and efficiency of the product, and therefore an intelligent form of thermal management is a matter of extreme importance. Acting as chip carrier, SCB technology makes a key contribution favouring the electrical and thermal properties.
In addition, the use of many different metals respectively alloys takes on a central role in regard to heat dissipation. SCB is fully based on a reel-to-reel concept (R2R) concept. This offers great possibilities to automate the production, which in turn leads to low manufacturing costs. Furthermore, in view of the large variety of materials and geometric variants new solutions arise with respect to thermal management.
User value:
a) Production process "reel-to-reel": high productivity due to level of automation, and subsequent low costs
b) Versatile stamping technology: the materials can be inflected and stamped and the resulting shape stabilizes the substrate and fixates the lenses. Stamped cooling ribs can also be produced, and contacting can be done at varying levels (= reduction of frame size).
c) Open choice of many different materials and thicknesses: in line with the application the most cost-optmized material can be selected.
d) Simpler operation: thanks to the R2R concept the manufacturing process is much easier to handle for the operator (as opposed to standard technologies).
e) Quicker separation: after being stamped, only very thin ribs of the material maintain the structures, and thus the parts can be readily separated/divided. Success confirmed by tests The Hanau materials and substrate expert does in fact possess enough in-house know-how to cover the entire spectrum of AVT production, but feedback from an independent outside source was sought to demonstrate just what can be achieved with SCB technology.
The Fraunhofer Institute IZM was invited to participate. The main topic of exploration was the heat transfer behavior of LED systems based on simultaneous stamping/laminating technology (SCB) in comparison to conventional technologies. The experts considered 3 substrate solutions for the HB module assembly: Printed Circuit Board, injected molding composite (over-molded stamped parts), and Stamped Circuit Board.
Following thermal analysis the substrates were scrutinized with close attention being paid to amongst other things, the structure, the overall materials, and the Thermal Interface Materials (TIM).
Additionally, factors influencing thermal management were examined, placing special emphasis on:
1. the LED chip itself (structure, dimensions, binning)
2. the LED chip mounting (type of connection: conductive adhesive, soldering, silver-sintering etc.)
3. the printed circuit board connection (dimensions)
4. the substrate (technology, materials and dimensions). In the final instance it was shown that SCB technology has a wealth of potential in regard to thermal management when compared to conventional technology.
Conclusion
The sophisticated thermal management provided by SCB technology leads to an increase in service life and efficiency. Moreover, tangible manufacturing characteristics are also in the main focus of this technology. The reel-to-reel process raises the degree of automation and increases productivity, thereby reducing costs. Because structuring is done separately it enables an optimization of material and design and an exploitation of the individual positive properties of each and every material! It all depends on whether it is more important to influence the overall thermal capacity (short-term applications) or influence the thermal spread (long-term applications). Through the sum of the positive properties the module retains a "cool head", costs sink and the light yield increases.
About W. C. Heraeus
W. C. Heraeus GmbH is part of the precious metals and technology group of Heraeus, processing worldwide the precious metals gold, silver, platinum, and other platinum group metals and special metals such as rhenium, tantalum, niobium and beryllium, to produce industrial products for the automotive, semiconductor, electronics, glass, chemical and petrochemical as well as medical industries. A global network of more than 30 companies includes production facilities for all phases of precious metal production and refining.
W. C. Heraeus holds a leading international position in industrial precious metal trading. The Precious Metals and Technology Group Heraeus headquartered in Hanau/Germany has been family-owned for over 155 years. Precious metals, sensors, dental and medical products, quartz glass and speciality lighting sources are the focus of our activities. Heraeus generated 3 billion Euros in product revenue and 13 billion Euros in trading revenue with more than 13.000 employees in over 110 subsidiaries. As a result Heraeus holds a truly leading position in all of its international key markets.
Basically, it means that heat can be drawn away from beneath the chip far more quickly, reliably and cheaply. A series of tests at the Fraunhofer IZM confirm that the technology contains an enormous amount of potential. Stamped Circuit Board (SCB) technology combines structured layers of metal and plastic for use in substrate assemblies, e. g. of LEDs.
Similar to printed circuit boards, this layering may consist of fiberglass-reinforced epoxy resin and copper – however, the separate structuring of the two materials opens the way for totally new design concepts.
During the manufacturing process both the plastic and the metal are initially treated on separate reels and structured according to the specific requirements involved.
At the next stage, the materials undergo lamination after which they are left perfectly aligned to each other. Advantages of SCB technology Light flux, efficiency and durability of LEDs depend very much on the junction temperature of the actual LED itself. A rising component temperature has a negative effect on the service life and efficiency of the product, and therefore an intelligent form of thermal management is a matter of extreme importance. Acting as chip carrier, SCB technology makes a key contribution favouring the electrical and thermal properties.
In addition, the use of many different metals respectively alloys takes on a central role in regard to heat dissipation. SCB is fully based on a reel-to-reel concept (R2R) concept. This offers great possibilities to automate the production, which in turn leads to low manufacturing costs. Furthermore, in view of the large variety of materials and geometric variants new solutions arise with respect to thermal management.
User value:
a) Production process "reel-to-reel": high productivity due to level of automation, and subsequent low costs
b) Versatile stamping technology: the materials can be inflected and stamped and the resulting shape stabilizes the substrate and fixates the lenses. Stamped cooling ribs can also be produced, and contacting can be done at varying levels (= reduction of frame size).
c) Open choice of many different materials and thicknesses: in line with the application the most cost-optmized material can be selected.
d) Simpler operation: thanks to the R2R concept the manufacturing process is much easier to handle for the operator (as opposed to standard technologies).
e) Quicker separation: after being stamped, only very thin ribs of the material maintain the structures, and thus the parts can be readily separated/divided. Success confirmed by tests The Hanau materials and substrate expert does in fact possess enough in-house know-how to cover the entire spectrum of AVT production, but feedback from an independent outside source was sought to demonstrate just what can be achieved with SCB technology.
The Fraunhofer Institute IZM was invited to participate. The main topic of exploration was the heat transfer behavior of LED systems based on simultaneous stamping/laminating technology (SCB) in comparison to conventional technologies. The experts considered 3 substrate solutions for the HB module assembly: Printed Circuit Board, injected molding composite (over-molded stamped parts), and Stamped Circuit Board.
Following thermal analysis the substrates were scrutinized with close attention being paid to amongst other things, the structure, the overall materials, and the Thermal Interface Materials (TIM).
Additionally, factors influencing thermal management were examined, placing special emphasis on:
1. the LED chip itself (structure, dimensions, binning)
2. the LED chip mounting (type of connection: conductive adhesive, soldering, silver-sintering etc.)
3. the printed circuit board connection (dimensions)
4. the substrate (technology, materials and dimensions). In the final instance it was shown that SCB technology has a wealth of potential in regard to thermal management when compared to conventional technology.
Conclusion
The sophisticated thermal management provided by SCB technology leads to an increase in service life and efficiency. Moreover, tangible manufacturing characteristics are also in the main focus of this technology. The reel-to-reel process raises the degree of automation and increases productivity, thereby reducing costs. Because structuring is done separately it enables an optimization of material and design and an exploitation of the individual positive properties of each and every material! It all depends on whether it is more important to influence the overall thermal capacity (short-term applications) or influence the thermal spread (long-term applications). Through the sum of the positive properties the module retains a "cool head", costs sink and the light yield increases.
About W. C. Heraeus
W. C. Heraeus GmbH is part of the precious metals and technology group of Heraeus, processing worldwide the precious metals gold, silver, platinum, and other platinum group metals and special metals such as rhenium, tantalum, niobium and beryllium, to produce industrial products for the automotive, semiconductor, electronics, glass, chemical and petrochemical as well as medical industries. A global network of more than 30 companies includes production facilities for all phases of precious metal production and refining.
W. C. Heraeus holds a leading international position in industrial precious metal trading. The Precious Metals and Technology Group Heraeus headquartered in Hanau/Germany has been family-owned for over 155 years. Precious metals, sensors, dental and medical products, quartz glass and speciality lighting sources are the focus of our activities. Heraeus generated 3 billion Euros in product revenue and 13 billion Euros in trading revenue with more than 13.000 employees in over 110 subsidiaries. As a result Heraeus holds a truly leading position in all of its international key markets.
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