As the fourth-generation light source, LED still has no way to completely replace the previous lamps. One of the biggest problems is heat dissipation. Increasing heat dissipation devices is also an important factor in the high cost of LEDs. Smart LED light are essentially LED lights, but an intelligent module is added to the basis of LED lights. The heat dissipation problem is also a major issue for smart LED light. Smart LED light are mostly used in personal homes and corporate offices. If the heat dissipation is not handled properly, it is easy to cause fires. There are already several heat dissipation methods, let’s discuss LED heating and heat dissipation.
Causes of heating of smart LED light
Although the current conversion of smart LED light energy to light energy is relatively good, it is far from the ideal goal. There is still a large amount of electrical energy that has not been converted into light energy. The photoelectric conversion rate of LED is 20~30%, and the remaining large amount of electrical energy is converted into Internal energy, more than 70% of the electrical energy becomes internal energy. Specifically, the following two factors are the main causes of heat generated by LEDs:
- The photoelectric effect is not high. When electrons pass through the PN junction, when the electrons and holes combine, the electrons cannot be converted into photons 100%. This phenomenon is called “current leakage”. The current leakage reduces the combination of carriers in the PN junction. The multiplication of the current leakage current and the voltage is the healing power of this piece, which is also the power of this piece of electrical energy to heat energy. Now the use of some new technologies has successfully solved the problem, and the conversion rate of the photoelectric effect of the smart LED has reached more than 90%.
- The photons produced by the photoelectric effect cannot be emitted to the outside. Since electrons are disordered, the direction of the photons generated is also disordered. Many photons do not pass through the protective cover, but are emitted in other directions, and are absorbed by the smart LED itself. Some photons are not passed through the protective cover. After being refracted, a part of it is absorbed, and the photons that are not emitted are converted into internal energy. This part is called external photoelectric conversion, the external photoelectric conversion is not high, only about 30% of the photons are emitted, and most of the other is converted into internal energy.
Thermal management
Thermal management is the most difficult, demanding, and costly design part of smart LED light. If adequate heat dissipation management is not carried out, it will cause catastrophic consequences such as lighting failure or fire. However, the heat dissipation management of LED lights is the most complex, demanding, and costly part of the entire design scheme. This article will discuss how to implement negative temperature coefficient (NTC) thermal management to fully improve the safety of LED design and significantly reduce power consumption.
In traditional incandescent light bulbs, the filament that is not in direct contact with anything is the only heat source. For LED lamps, the LED is the light source, and the heat dissipation of the LED is directly in contact with the LED bulb. This direct contact is caused by the connection between the LED and the driver circuit. In order to achieve heat dissipation, the heat must be released from the LED and driver circuit or be effectively managed. At the same time, this is also the basic prerequisite for the LED lamp to keep working for a long time.
In order to understand the importance of heat dissipation management, we might as well imagine such an application, instead of installing smart LED light on general lighting sockets such as wall lights or ceiling lights and using a wall switch to control the LED lights. Since the heat dissipation of most standard lamps such as wall lamps or ceiling lamps mainly relies on thermal convection or airflow, the heat dissipation effect of this application is not ideal for LED lamps.
If effective heat dissipation management is not carried out, it will bring catastrophic consequences such as frequent replacement of failed LED lights or building fires. Using the intelligent LED lamp control function to monitor the temperature of the LED lamp is a relatively simple heat dissipation management method. At the same time, because the LED lamp can reduce the power when the temperature rises, safety will also be greatly improved.
NTC Thermal Management
The basic principle of the NTC circuit is to improve the safety of the LED lamp and reduce the design complexity by monitoring the temperature of the LED lamp. When the temperature rises, the controller reduces the lumens and thereby keeps the LED within a safe level. In other words, when the temperature rises, the lumens are reduced, and vice versa, when the temperature falls, the lumens are increased.
We can detect the temperature change of the LED lamp by detecting the voltage on the NTC. The detected voltage is directly related to the temperature of the NTC, and the resistance of the NTC will decrease as the temperature of the NTC and its surrounding circuits increases. There are two basic methods of using NTC to determine temperature.
Method 1: Use NTC in the system to enforce a voltage divider circuit with a known voltage, and then measure the voltage on the NTC node. As the temperature of the NTC increases, the resistance decreases. A decrease in resistance will result in a change in the voltage divider ratio. The voltage of the NTC node will also decrease with increasing temperature.
Method 2: Force a known current through the NTC and measure the voltage on the NTC. As the temperature of the NTC increases, the resistance decreases. According to Ohm’s law, a decrease in resistance will change the voltage on the NTC node. If the resistance decreases while the current remains the same, the voltage on the NTC node will also decrease.
In terms of improving operation and improving safety, these two methods of monitoring the temperature of smart LED lights are simple and straightforward to implement.
LED cooling method
LED lamp heat dissipation is more troublesome, because LED is a sealed environment, and a single LED is small. The heat dissipation of the LED is related to its bottom material and the selected production process. Its heat dissipation mode is mainly to dissipate the heat generated by the LED chip into the air. Poor heat dissipation will affect the performance and life of the LED. A single LED generates very little heat, but the enclosed environment makes it difficult to dissipate heat, and the heat will accumulate. Moreover, the general LED has a long continuous working time, which makes the temperature of the LED chip very high. . There are many ways to transfer heat to the air. The basic principle is to transfer the heat generated by the chip to the aluminum substrate and then to the air. The heat dissipation of LED lights includes two parts: heat dissipation and heat conduction, and different places will use different shells for heat dissipation. The following are several heat dissipation methods commonly used in the market:
- Cooling fins
Heat conduction with heat dissipation fins is a common heat conduction method. Heat dissipation fins are mostly made of aluminum. Aluminum has good thermal conductivity and relatively low cost. The heat dissipation fins can not only conduct heat to the shell but also dissipate heat by themselves, which increases Quite a lot of heat dissipation area.
- Thermally conductive shell
The housing is made of materials with good heat conduction and heat dissipation to enhance the dissipation of heat. Some LED lamp housings are made of metal materials, and some are made of plastic filled with heat conduction materials. These are materials with good heat conduction and strong heat dissipation.
- Strengthen airflow
The airflow of the LED lamp accessory is very slow, which will cause the air temperature of the LED lamp accessory to be high, which will reduce the heat dissipation efficiency of the LED lamp, strengthen the airflow, and quickly spread the heat in the air to maintain the air temperature of the LED lamp accessory Appropriate, can improve the heat dissipation efficiency. The cost of enhancing airflow is relatively low, just add an electric fan outside.
- Electric fan shell
Adding an electric fan inside the shell can enhance the airflow, reduce the temperature inside the shell, and enhance the heat dissipation efficiency. Adding an electric fan in the casing is not suitable for outdoor, because rain or another humid environment will cause the electric fan to age and short-circuit. The replacement of electric fans is also a hassle.
- Heat pipe heat dissipation
Using a heat conduction tube, the heat of the LED wick is conducted to the aluminum substrate, and then to the shell. Many LED lamp wicks have a heat conduction tube device, which is a common and effective way.
- Shell radiation treatment
Coating the shell of the LED lamp with radiant material can transmit the heat generated by the LED in a radiant manner, reducing the temperature of the LED lamp.
Summary
The development of the heat dissipation technology of smart LED lights has greatly promoted the application of LED lights. Without these technological breakthroughs, the life and use of LEDs will be limited. At the same time, the use of such heat dissipation materials also increases the cost of LEDs. Cost and performance need to be considered comprehensively. The heat dissipation technology of LED lights needs further development, requiring higher efficiency and lower cost heat dissipation devices, otherwise LED lights Further development will be greatly restricted. At the same time, we should also note that in the process of converting electric energy into light energy, more than 70% of the electric energy of the LED lamp will be converted into heat and wasted. We should reduce heat production while strengthening heat dissipation, effectively reducing heat generation Is the best “heat dissipation”.
MOKOLight smart LED light uses the best materials and the best technology to produce excellent smart LED lights. When there is no breakthrough in technology, more ingenious heat dissipation design and better heat dissipation materials are the best way to dissipate heat.
