Analysis of LED packaging core technology (two)

Three, power supply technology

1 integrated light source substrate and aluminum substrate is not necessary to achieve 3750V withstand voltage

In the design of the LED system, the most common problem is how to choose the driving power, and in fact the LED failure or damage, driving power occupies a very high proportion, driving power supply reliability and life of LED lighting technology into short board.

LED lighting is a general electronic products must be through the country's corresponding safety standards, that is, LED lamp shell and human contact does not constitute a risk of electric shock. General LED driver design and non isolated isolation; non isolated power supply uses less components and has a high efficiency, but limited to the use of shell insulation products, such as LED lighting, LED and driver are integrated and sealed in plastic insulation, so that the final risk no electric shock. Isolated LED driver power supply with isolation transformer, which means that the high voltage and the secondary LED isolation, can be directly contact with the hand without shock. Compared with the non isolated power supply, the isolation power supply is large, the efficiency is low, and the cost is high.

Many people (including expert Professor) that LED light source (PIN) should be greater than the safety voltage to ground voltage (3750V) or aluminum and ceramic substrates must meet the safety requirements of radiator pressure, this is actually a misunderstanding, lack of power knowledge, experimental results show that the LED chip substrate by silver electrode on the solid seal ground (substrate) breakdown voltage is about 300V, LED chip substrate pressure is far less than the safety requirements, it must use the isolated power supply. Since the use of isolated power supply aluminum substrate is not necessary to achieve 3750V withstand voltage, there is no need to set aside the so-called creepage distance". As of the end user regardless of the non isolated power supply or power supply are isolated completely unnecessary requirements of aluminum substrate to 3750V insulation, because the input of non isolated power supply and load is potential, there is no need to demand more aluminum substrate by safety voltage, the higher the pressure of the aluminum substrate layer insulation is thicker, the higher the cost, the larger the thermal resistance. It has been proved by practice that most of the COB aluminum substrates are separated by thermoelectric packaging, which has been widely used in the market, which is proved to be practical and feasible.

2, the LED driver can solve this short board with liquid cooling technology

The LED can reach tens of thousands of hours, however, the current matching power supply can not meet the requirements. In the LED lighting products, failure is a common phenomenon, most because of power failure, because many LED lighting application power enclosed in a small space, ventilation and heat dissipation become the main technical bottlenecks, if not careful thermal design, driving circuit and LED power supply is easy because of high temperature degradation or permanent failure. LED driving circuit of LED life is not up to the requirements of the key element is the electrolytic capacitor, electrolytic capacitor manufacturing regulations currently most of the life of the electrolytic capacitor is generally 105 DEG C for /2000 hours, the service life is at a temperature of 105 DEG C under the condition of only 84 days, even reduced to 85 DEG C, the service life is only 332 day, less than a year! Far from being able to meet the requirements of the LED drive, why does the electrolytic capacitor have a temperature limited? The reason is that the electrolyte of electrolytic capacitor manufacturing process, need to "hydration" aluminum electrolytic capacitor in order to achieve very low ESR, the easiest way is to increase the moisture content of the electrolyte, the boiling point of water is about 100 degrees, high water content leads to the evaporation of the electrolyte "under high temperature and dry" failure. Capacitor manufacturers to curb the high moisture content of the electrolyte, the "hydration" reaction, power producers have also used glue sealing process to solve the capacitor failure, but still not completely.

In this paper, the driving power supply is immersed in the cooling chamber of the closed radiator. The pressure difference between the inside and outside of the electrolytic capacitor is very small, which not only reduces the explosion of the electrolytic capacitor, but also avoids the evaporation". Due to the removal of viscose, but also to avoid the adhesive stress on the components of the strain, not easy maintenance and other drawbacks. The sealing structure can improve the waterproof grade (up to IP68), which effectively prolongs the service life of the power supply.