A recent experiment has a very interesting and strange phenomenon. I hope to discuss and communicate with you and analyze the causes of this phenomenon.
The test was carried out in the laboratory. The indoor environment, the power supply was 220V, 50Hz AC, the voltage was stable, the lamp was 400W LED lamp, and the measuring instrument was a common Fluke. The purpose of the test was to measure the starting characteristics of the LED lamp.
The test is very simple. After connecting the lamp and the power supply, connect the measuring instrument. After checking the wiring is correct, turn on the switch. After the lamp is energized, the sensor will light up instantly. The instrument records the startup process. The waveform is shown in Figure 1.
Figure 1 Startup process waveform
As can be seen from Figure 1, the startup process has the following characteristics:
1, the starting current is large
The startup process has a very large peak current with a maximum of 29A. For LED lamps with a rated current of only about 2A, the peak current is nearly 15 times, far exceeding expectations.
2, short start-up time
The start-up time is relatively short, from the start of the power supply until the current is stable for only about 1 second, and the maximum time is about 800 nanoseconds, very high.
3, negative peak
It can be seen from the figure that in addition to the positive peak, there is a negative peak in the startup process, and sometimes the negative peak is larger than the positive peak.
Figure 2 Large negative peak
4, peak uncertainty
Many experiments have found that there is uncertainty in the size of the peak. This is related to the fact that the power supply is AC, and the timing of the power on of the luminaire is random, resulting in different peak sizes.
Figure 3 Peaks are uncertain
Tests show that there is a large starting current at startup, up to 15 times; the starting time is short, only about 1 second, the peak value is around 800 ns; there is a reverse peak; the peak has uncertainty, and the peak currents of different tests are different. . After the article was launched, it caused the attention and comments of the majority of netizens, and the reasons for this were different. The author tries to explain and discuss with you.
Figure 4 LED lamp drive circuit diagram
Figure 4 is taken from the driving circuit diagram of an LED lamp. The power supply is AC 220V, and the capacitors C1 and R1 function as a step-down current limit. VD1~VD4 form a rectifier circuit, which turns the alternating current into direct current. The capacitor C2 is then filtered, and the DC voltage provides operating voltages for the LEDs VD5-VD8. It can be seen that when the LED lamp is energized, the capacitor C2 is charged first, which is the root cause of the peak current at startup. After C2 is charged, the current gradually stabilizes and reaches a steady state, and the current becomes the rated current. The charging time of C2 determines the time at which the peak current appears.
Therefore, when designing the LED lighting distribution system, the protective appliances should be matched.
Therefore, the filter capacitor in the LED drive circuit is responsible for generating a large startup current.
Lithium Battery Crv3,Lithium Battery Camera,Camera Lithium Battery,Lithium Photo Battery
Jiangmen Hongli Energy Co.ltd , https://www.honglienergy.com