[Source: "High-tech LED - Technology and Applications" August issue Luo Hongji] In the early days of LED lighting, the AC high-voltage mains power was converted into a low-voltage power source to drive the LED light source. The circuit principle basically uses the current limiting resistor R to limit the strong inrush current flowing through the LED light source to protect the LED light source from safely emitting light. Obviously, this technology is to replace the power efficiency for the safety of the LED light source. The smaller the resistance of the current limiting resistor R is, the worse the safety is. The greater the resistance of R, the greater the safety. LED lighting brings the disadvantages of high cost, many faults, low power consumption efficiency, and dead lights. The drive power has been improved and modified many times, but the shortcomings still exist.
I have done a lot of data collection, analysis and testing on LED lighting and in-depth analysis by electronic circuit theory to find out the mechanism of LED string light source driven by AC high voltage power supply, adopting the commonly used method of “avoiding its edge”. The Chinese patent name is LED power-on lighting circuit, the application number is 201010193525.3, which is a zero-crossing power switch. When the instantaneous value of the AC high-voltage mains power supply is zero (also known as zero-crossing), the AC high-voltage power supply and the LED string are connected. The instantaneous value of the AC high-voltage mains power supply, which is added to the LED light source at the moment of turning on, is the zero-crossing voltage. The zero-crossing voltage of the different brands of zero-crossing power switches is different, but they are all within 0~25 volts. The LED string light source will be damaged. After the LED string light source is turned on, all the LEDs enter the response state within 1 microsecond, and the LED string light source has the "mass power" to jointly undertake the high voltage safety power-on illumination.
The composition of the LED illumination lamp (referred to as the patented lamp) of the invention patent is: AC high-voltage mains power supply u1 (220V 50HZ), rectifier bridge, zero-crossing power switch, LED string light source, current limiting circuit five parts. (Refer to Figure 1) The rectifier bridge converts u1 to 100 positive half-cycles of pulsating DC voltage per second. The traditional technology sacrifices the power efficiency for the safety of the LED light source. The AC high-voltage power supply uses a zero-crossing power switch, which does not damage the LED string. The light source, together with the "mass power", bears the high-voltage safe passage of light.
U2, you can choose to buy a few micro-products with one dollar; the zero-crossing power switch can use a small zero-crossing power switch integrated block, or you can use a small semiconductor voltage control integrated block and a three-pole switch. These small and fine components are widely used. The international brand name can be used for a long time for decades. The entire zero-crossing power switch component costs about three yuan, and its volume is smaller than one-fourth of the mobile phone battery; the LED string light source is the illuminant. According to the requirements of the Ming Dynasty, select the appropriate power and quantity of LEDs in a reasonable series and parallel connection; the current limiting circuit can be selected with a simple PTC current limiting, or the power limiting current limiting mode can be used to achieve current limiting by increasing or decreasing the number of LEDs. Constant current circuit can also be selected, which method should be selected according to lighting requirements.
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For more information, please refer to: "High-tech LED - Technology and Applications" August issue 
