LED will continue to emit heat, and shade has become smaller and smaller. Brightness and power consumption rising, but was closely aligned with the LED (front and rear lights) was not equipped with the appropriate cooling fan. Therefore, reliability and performance is bound . to be affected If the LED junction temperature exceeds a critical problem arises: LED lights dimmed If the temperature continues high, LED lamp life will be shortened, then premature retirement The average life expectancy of LED lights on the car has thousands of hours.. , early retirement will bring additional manufacturer warranty costs.
Excellent thermal management depends on good thermal design. As shown in Figure 1, LED elements are designed in the first part of the process. Element using thermal analysis software designers and test equipment for the material and structure of the element analyzed, ensure that the heat generated on the junction can be easily comes out through the LED element layer. Subsystem designers will LED elements arranged in an array, and add radiators and other cooling devices, and then analyze the product again. They may adjust the spacing between the LED elements, or add additional cooling devices to ensure that the LED does not exceed the critical temperature. The final step is usually a mechanical design engineer with mechanical computer-aided design system to complete, the designer will line up of LED lights into the shade (such as car headlights) years, while the use of advanced computational fluid dynamics (CFD) software for thermal analysis.
So where is the problem? Over the years the industry has been using excellent CFD thermal analysis software. FloTHERM other products fast, precise and very easy to use, and requires no external experts, engineers within the company will be able to complete the analysis. But the problem is that the accuracy of the results of software, depending on the input components model accuracy. If the component model input is not accurate, regardless of how perfect the process of analysis, the results will only mislead the software designer.
But the key is a typical LED data sheets provided by suppliers, will only be a single thermal resistance of its total power consumption (such as maximum forward current and voltage), and the "knot" and some reference points (such as welding points) between and how the package without the heat and dissipate information layers, the layers are not able to be used to define the thermal resistance and heat capacity of the path / obstacles description.
In this way there will be any problems? Typically, thermal management experts estimate the internal structure of the package, and creates a thermal model to describe the thermal resistance and heat capacity of each layer and the circumstances of each structure. This model is a few percentage points as long as the deviation occurs, it will result in inaccurate analysis, but does not verify or determine the quality of the thermal model of such a method.
So fundamentally speaking, we still have gaps in the designed cooling systems. In all aspects of product development (components, subsystems, and the entire system), the thermal analysis must not be less, but only under favorable circumstances component thermal model, it is possible to obtain good thermal analysis results. Without knowledge of the internal structure of the package components, we can not define or verify the accuracy of the model, and component suppliers usually do not divulge intellectual property in this area.
The solution is simplified by defining and validating components of a thermal model shown in Figure 2, the establishment of a "bridge" between the hardware test / measurement and thermal analysis. Existing hardware element is capable of measuring the parameters of a heat dissipation characteristics. With sophisticated software, these measurements can be converted to the simplified thermal resistance and heat capacity network, we can read the simplified network model of the thermal analysis software.
For example, Mentor 's T3Ster hardware components coupled to the test, you can measure the transient junction temperature changes, either heating or cooling elements, can be accurate to 0.01 degrees Celsius. In the heat dissipated to the surrounding environment from the end of the process, can be collected in one minute to transient changes over ten thousand data points to describe the junction temperature, and transient characteristics of the junction temperature, says the components of each layer thermal resistance and heat capacity situation. With these data, using the analysis software automatically generates LED simplified thermal model. An accurate and efficient model was born.
france led street lighting factory in the design, can use this technique to measure the thermal performance, and optimize it, and then again for our customers measure and create a thermal model. Subsystem and system developers can use it to verify the thermal model obtained from the vendor or supplier does not provide in the case of the model to create a model yourself. The reliability of electronic equipment design margin is very small, design responsibility usually falls upon vendors wife, warranty and recycling issues will directly affect their profit and loss, so they need to confirm their own product design hundred percent no problem.
In the thermal resistance -. Heat capacity chart, the blue line represents just produced LED, other lines denote used 500 hours, 2000 hours and 3000 hours of LED Seen by the horizontal direction, a layer of high thermal resistance used to represent the line of LED, which shows that the position of the case material separation occurs, the thermal conductivity of air is much smaller than the original material. This type of fault diagnostic tests can be used for LED and IC package.
The second application is in the production process. In the production of LED, glue thickness and other parameters is not fixed, so it can serve as an important test instrument production line of a ring. First sampling, testing and then quickly make comparison with standard devices quickly able to find deviations in the production process, and thus give correct. ROI The test equipment is very impressive. So, now france led street lighting factory and original equipment manufacturers responsible for subsystem and system development, you can use a precise components to complete the design , application and failure analysis (Figure 4) of the product.
Figure 5 shows the auto industry 's supply chain, we see that the supply chain in addition to automotive original equipment manufacturers, as well as secondary and primary suppliers. Have good thermal design thermal analysis, one and two suppliers designers need to have this capability . This thermal physical analysis by accurate and timely test to heat the measuring element, subsystems and systems to support and verify. Automotive original equipment manufacturer can prove is that they are buying products with high reliability and low power
consumption performance.
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