Detailed explanation of the power supply design technology for LED filament lamps (picture and text)

　　LED filament lamp design and production technology became mature in 2013, and factories producing LED filament lamps sprang up like mushrooms after rain. LED filament manufacturing technology, LED filament application technology, glass bulb sealing and filling technology, and flicker-free power supply technology were all studied in depth and improved. Several incandescent lamp factories successfully transformed and upgraded, and traditional incandescent lamp factories took advantage of their irreplaceable advantages to enter the LED lighting industry.

　　Customers in Europe, North and South America, South Africa, Southeast Asia, and the Middle East have a warm response to LED filament lamps, and they are willing to pay a higher price for them. The current export price of a 3.6W A60 filament bulb has reached US$4.5, and its cost-effectiveness is much higher than other types of LED bulbs.

　　In December 2008, Japan's Ushio Lighting Company announced the successful development of a practical LED filament lamp, which uses 6 LED filaments in series, with each filament bound to 3 LED cores. Therefore, each bulb uses a total of 18 LED cores.

　　Chinese engineers have used their intelligence and wisdom to design LED filaments into high-voltage LED strings (HVLEDs). 26-30 LED cores are bound on a transparent substrate strip with a thickness of 1.2X0.5--1mm. High voltage (DC50-280V) and low current (10-40mA) are used to drive and light up. Therefore, LED filament lamps can emit the same brightness as low-voltage (DC3.2V) and high-current (200-700mA) LED bulbs with the same power, while the lamp body is only slightly warm, about 30-35 degrees Celsius.

　　At present, the main LED filament lamp products are 1.8--2.4W C35 candle bulbs and 3.6--10W A60 bulbs.

　　The main electrical performance of this solution is shown in Table 1. The power input voltage is AC180-264V, the output voltage is DC150V, the output current is 20mA (for a 4-filament bulb), and the efficiency is 91%. The bill of materials (BOM) of this solution is shown in Table 2. The total number of parts is only 13, which is a very economical and practical solution.

　　AC and DC voltage safety isolation

　　The current LED filament lamp integrates the LED driver power supply , isolation plastic bushing and metal lamp holder. Therefore, the isolation plastic bushing plays the role of AC and DC voltage safety isolation, and is also a necessary measure for the whole lamp to pass EMI and other certifications. The diameter of the PCB board of the switch constant current driver power supply is designed to be 18mm. The purpose of such a small design is to bury the power supply as a whole deep in the lamp holder of the bulb, and the lamp holder of the bulb is all metal. As we all know, all bulb lamp holders are directly connected to one end of the power grid when working, and are in an AC high voltage field; and the PCB board of the power supply has both AC high voltage points and DC high voltage points, so it is necessary to safely isolate the entire driver power supply from the metal body of the lamp holder. The isolation plastic bushing is a simple, effective and low-cost solution. At the same time, due to the height of the electrolytic capacitor, the entire power supply cannot be buried within the height of the lamp holder at present, and the isolation plastic bushing needs to be used to bury the entire power supply in space. Of course, an extended metal lamp holder can also be designed to cover the power supply, but the safe isolation of the power supply and the inner wall of the lamp holder is still required. The placement of the LED driver power supply, isolation plastic bushing and metal lamp holder is shown in the figure.

　　EMI Testing

　　LED lights exported to the European market need CE certification, and LED lights exported to the North American market need UL certification.