After so many years of experience in contact with lamp manufacturers, it is often felt that lamp manufacturers do not want to buy good LED power supply, but do not know how to distinguish whether the purchased LED power supply is good or not, and they are also worried about whether they spend a high price on low-quality LED power supply. Therefore, as a lamp manufacturer, the most difficult feedback is to buy LED power supply, because the quality of power supply is difficult to detect. It has aged for 4 hours in its own factory, and some even aged for 24-72 hours, but these aging products often have 5% left-right or higher proportion of defects within 3-6 months of shipment. Often these bad situations make the lamp manufacturers miserable, do a customer and lose a customer.
What if the quality of LED power supply is good or bad? We can identify from the following points:
First, the driver chip – IC
The core of driving power supply is IC. The quality of IC directly affects the whole power supply. The driver IC of large manufacturers are purchased from Jingyuan and packaged by large packaging plants; The driving IC technology of small factories is to directly copy the driving design scheme of large factories and find a small packaging factory for packaging, which can not normally ensure the consistency and stability of the whole batch of ICs, resulting in the inexplicable failure of the driving power supply after being used for a period of time. Therefore, the IC on the LED power supply refuses to be polished, so that the lamp manufacturers can understand the IC scheme and calculate the driving cost, so as to purchase power products at a reasonable price.
The control chip can be regarded as the brain center of the power supply, and the transformer determines the power and temperature resistance. The transformer is responsible for completing the “AC magnetic energy DC”, and the energy overload will saturate and blow up the machine. The core of the transformer is the magnetic core and wire package.
The quality of magnetic core is the core of transformer, but like porcelain, it is very difficult to distinguish. The simple appearance identification is: the appearance is crisp, dense and bright, and the pores on the back are polished at the same time. At present, the magnetic core used by Shanghai Nuoyi is the open mold pc44 magnetic core to ensure the high efficiency of the power supply.
The wire package is made of copper wire winding. The quality of copper wire is the key to the service life of transformer. Copper clad aluminum wire of the same length is 1 / 4 of the price of pure copper wire. Due to cost pressure, transformer manufacturers will often be mixed with copper clad aluminum wire wrapped transformers. As a result, the transformer will burn out when the temperature rises, resulting in the failure of power supply and the whole lamp. Therefore, many lamps, especially lamps with built-in power supply, often explode within about 6 months of shipment. How to distinguish whether the copper wire is pure copper wire or copper-clad aluminum? Use a lighter to ignite it and burn it quickly, that is, copper-clad aluminum. It can also be identified by measuring the coil resistance.
Third, electrolytic capacitor and chip ceramic capacitor
The quality and service life requirements of the input electrolytic capacitor may be well known and we all attach great importance to it. However, we often ignore the quality requirements of the output capacitor. In fact, the life of the output capacitor has a great impact on the life of the power supply. The output terminal has a switching frequency of up to 60000 times per second, which leads to the increase of parasitic resistance heating of the capacitor and the generation of substances similar to scale. Finally, the electrolyte heats up and explodes. Recommended output electrolytic capacitor: LED special electrolytic capacitor is adopted, and the general model starts with L. At present, our output electrolytic capacitors are Aihua high-life electrolytic capacitors.
Ceramic capacitor: the material is divided into X7R, X5R and Y5V, while the actual capacity value of Y5V can only reach 1 / 10 of the actual capacity value, and the nominal capacity value only refers to working at 0V. Therefore, the small chip resistance and poor options will also lead to the price difference of cost and greatly shorten the service life of power supply.
Fourth, the circuit design and welding process of power products
Judging the advantages and disadvantages of design: regardless of the professional point of view, it can be distinguished by some intuitive methods, such as neat, generous and orderly component layout, bright, clean and straight solder joints. A good engineer will not make disorderly design. As for flying wires and manual components, there is a serious lack of technical force.
Welding process: manual welding and wave soldering process. As we all know, the wave soldering process quality of mechanized production must be better than manual welding. Distinguishing method: whether there is red glue on the back. (solder paste process + welding fixture can also realize wave soldering, but the fixture cost is high).
Solder joint testing instrument for patch: AOI. The equipment can detect the phenomena of false welding, false welding and missing welding in the process of chip placement.
At present, the flashing phenomenon of lamps and lanterns in use for a period of time is basically caused by the faulty welding of power supply or lamp beads. The false soldering test of this product is very difficult to pass the aging test, so we must rely on AOI to test the patch quality of the power supply.
Fifth, the batch testing of power products, aging rack and high-temperature aging room
No matter how well the materials and production process are controlled, the power products still need to be tested for aging. Because the incoming inspection of electronic components and transformers is difficult to control. Only through the aging of the whole batch of power supply and high-temperature sampling inspection of high-temperature room, can we detect the quality stability of this batch of power supply and whether there are potential safety hazards of materials.
Function of mass high-temperature sampling inspection: at present, the failure of power supply is between 1% and 1%, and such failure can only be found after thousands of high-temperature aging.
The high-temperature room can simulate the harsh environment of power supply. Batch problems can be found through sampling inspection under tightened conditions, such as unreasonable design, poor raw materials, failure in deduction lamps, high-voltage switch impact, etc.
Long term aging at normal temperature: random failures such as false welding, missing welding and collision are screened out, early failures of components are filtered out, and the failure rate of finished products is effectively reduced (from 1% to 1 / 1000).
Normal temperature aging consumes aging equipment and personnel. For factories with a daily output of 100000 power supplies, aging equipment covers an area of at least 500 square meters, more than 10000 aging bits, and realizes assembly line aging, which is rare in the industry.
Source: OFweek semiconductor lighting network