After so many years of experience in contact with lighting manufacturers, I often feel that lighting manufacturers do not want to buy a good LED power supply, but that they don’t know how to distinguish whether the purchased LED power supply is good or not, and they are more worried about whether to buy low-quality LED power supplies at a high price. . Therefore, as a lighting manufacturer, the most difficult thing to give feedback is to buy LED power supplies, because the quality of power supplies is difficult to detect. They have been aged for 4 hours in their own factories, and some even have been aged for 24-72 hours. However, these aged products are often in the market. Within 3-6 months of shipment, there will be about 5% or more defective products. Often these unfavorable situations cause the lighting manufacturers to suffer unspeakably, and lose a customer by being a customer.
So how to identify the quality of LED power supply? We can identify it from the following points:
**: Driver chip—IC
The core of the driving power supply is the IC, and the quality of the IC directly affects the entire power supply. The driver ICs of large manufacturers are purchased from crystal gardens and packaged by large packaging factories; while the driver IC technology of small manufacturers is directly copied from the driver design scheme of large manufacturers and found in small packaging factories for packaging, which cannot guarantee the entire batch of ICs. Consistency and stability, resulting in inexplicable failure of the drive power supply after a period of use. Therefore, the IC on the LED power supply refuses to be polished, so that lighting manufacturers can understand the IC solution and calculate the driving cost, so as to purchase power supply products at a reasonable price.
Second: Transformer
The control chip can be regarded as the brain center of the power supply, and the power and temperature resistance are determined by the transformer. The transformer is responsible for completing the “alternating current – magnetic energy – direct current”, and if the energy is overloaded, it will saturate the fryer. The core of the transformer is the magnetic core and wire package.
The quality of the magnetic core is the core of the transformer, but like porcelain, it is extremely difficult to distinguish. The simple appearance identification is as follows: the appearance is crisp, dense, and bright, and the one with polished pores on the back is the top grade. At present, the magnetic core used by Shanghai Nuoyi is the molded PC44 magnetic core to ensure the high efficiency of the power supply.
The wire package is made of copper wire winding, and the quality of the copper wire is the key to the life of the transformer. Copper-clad aluminum wires of the same length are 1/4 of the price of pure copper wires. Due to cost pressures, transformer manufacturers often mix transformers with copper-clad aluminum wires in them. As a result, when the temperature of the transformer rises, it will burn out and fail, resulting in the failure of the power supply and the whole lamp. Therefore, many lamps, especially lamps with built-in power supply, often appear to blow up after about 6 months of shipment. And how to distinguish whether the copper wire is pure copper wire or copper-clad aluminum? Use a lighter to ignite it, and quickly burn it to be copper-clad aluminum. It can also be identified by measuring the resistance of the coil.
Third: electrolytic capacitors and chip ceramic capacitors
The quality and life requirements of input electrolytic capacitors may be known to everyone, and everyone also attaches great importance to them. However, people 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 as high as 60,000 times per second, which causes the parasitic resistance of the capacitor to heat up, producing scale-like substances, and finally the electrolyte heats up and explodes. Recommended output electrolytic capacitor: Use LED-specific electrolytic capacitors, 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, and the actual capacitance of Y5V can only reach 1/10 of the actual value, and the nominal capacitance only refers to when it works at 0 volts. Therefore, the poor option of this tiny chip resistor will also lead to a price difference in cost and greatly shorten the life of the power supply.
Fourth: Circuit design and welding process of power supply products
Judgment of good or bad design: Regardless of the professional point of view, some intuitive methods can be used to distinguish, such as component layout is neat, generous, orderly, and solder joints are bright and straight. A good engineer doesn’t make haphazard designs. As for flying wires and manual component addition, it is a manifestation of a serious lack of technical strength.
Welding process: manual welding and wave soldering process, as we all know, the quality of mechanized wave soldering process is definitely better than manual soldering. Identification method: whether there is red glue on the back. (Solder paste process + soldering fixture can also achieve wave soldering, but the cost of the fixture is high).
SMD solder joint inspection equipment: AOI. This equipment can detect virtual soldering, false soldering, and missing soldering during the placement process.
At present, the flashing phenomenon of the lamps after using for a period of time is basically caused by the power supply or the weak welding of the lamp beads. And the detection of virtual soldering of this product is extremely difficult to pass the aging detection, so it is necessary to rely on AOI to detect the chip quality of the power supply.
Fifth: Batch testing of power supply products Aging rack and high temperature aging room
No matter how good the material and production process are, the power supply 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 entire batch of power supplies and the high-temperature sampling inspection in the high-temperature room, can the quality stability of this batch of power supplies and whether the materials have potential safety hazards be detected.
The role of large-scale high-temperature sampling inspection: At present, the failure of power supplies is between 1/1000 and 1 percent, and only thousands of high-temperature aging will find such failures.
The high-temperature room can simulate the harsh environment of power supply. Sampling inspections under stricter conditions can find batch problems, such as unreasonable design, poor raw materials, failures in deduced lamps, and high-voltage switch shocks.
Long-term aging at room temperature: Screen out random failures such as virtual soldering, missing soldering, and collisions, filter out early failures of components, and effectively reduce the failure rate of finished products (one percent to one thousandth).
Aging at room temperature consumes a lot of aging equipment and personnel. For a factory with a daily output of 100,000 power supplies, the aging equipment covers an area of at least 500 square meters, with more than 10,000 aging positions, and the aging of the assembly line is rare in the industry.