With the development of social civilization, low-carbon energy saving has penetrated all aspects of our lives, and the LED light source has been vigorously promoted due to energy efficiency, good energy saving effect and good dimming. So how does indoor LED lighting DC power distribution? How does the voltage level choose? Let’s take a look at it in detail!
1, LED lamp structure
LED refers to a light-emitting diode, a P-N junction semiconductor diode that can emit visible or infrared radiation. Decision by the LEDPN junction, the LED lighting requires a low voltage DC drive, and therefore, each luminaire sets a constant current power drive module, combined with the luminaire to form an integrated product, and can directly access the main 220V AC power supply. LED lamp constant current drive module circuit is shown in Figure 1.
Problems with this structure of LED lamps:
1) Harmonic pollution: Each LED lamp is harmonically pollution source, the more quantities, the more harmonics, and it will lead to excessive neutral line currents. In the lighting design, it is usually selected according to the calculation current, so it will bring a deviation.
2) LED lamp life shortage: LED light source is in general, the life can reach 25,000 ~ 50000h, but its power drive module is often affected by the capacitance in constituent elements, the life is difficult to break through 20000h, the life of the LED light is much greater than its drive module The life of the power drive module has become a short board that restricts the life of the LED luminaire.
2, technical pathway
LED luminaires require DC power supply, and whether to use DC system to supply power to all LED lamps directly in low-voltage distribution screen, which is available in low-voltage distribution screen. The author is based on the DC power distribution and voltage level of indoor LED lighting system and its voltage level.
In the original variable distribution chamber, the transformer is increased, the rectifier is powered, the rectifier is powered, and the LED is powered by direct current, and the DC is powered to the LED luminaire (as shown in Figure 2), so that the LED luminaire can save the rectifier device. Only the DC / DC device and constant current diode are retained, which greatly reduces the cost of LED lamps, and extends the life of LED lamps.
3. Power supply voltage selection
Considering the current to the human body effect and voltage drop factors, the power supply voltage level of the LED illumination is preselected with the common voltage level 110V, and the feasibility of the 110V voltage level is verified from two aspects.
1) Current to the human body effect
Figure 3 is GB / T13870.1-2008 / IEC / TS60479-1:
2005 “Current to human and livestock Effects Part 1: Universal part” in the DC current effect through the human body. When the current through the human body exceeds the right area of the CL curve in the figure, there is a possibility of a pathological effect, such as the heartbeat, breathing stop, and the damage of burns or other cells. The probability of ventricular fibrillation also increases with the amplitude and time of current.
GB / T16895.21-2011 “Low-voltage electrical device” No. 4-41: Safety protection electric shock protection “stipulates: When the system is grounded, the DC contact voltage of more than 120V is dangerous to the human body.
The IEC standard will cause the DC expected contact voltage limit of ventricular fibrillation to take 120V. Therefore, the DC 110V voltage level is selected, and the current is in line with the safety of the human body effect.
2) Voltage drop calibration
4, economic analysis
After the technical solution shown in Figure 2, the cost reduction and decrease in the project is as follows:
1) Save costs: LED lamps save the drive (the author understands that the driver accounts for about 50% of the lamps of the lamps), the LED lamp life is extended (the replacement rate is greatly reduced), and the photovoltaic power generation is convenient (low-end operating costs).
2) Increase costs: the low voltage distribution screen feed line increase the transformer, rectification equipment. At this stage, because of the many aspects of manufacturing standards, DC equipment is still very limited, so this program is in the LED lamps, and the longer buildings (such as large commercial complexes) in the LED lamps (such as large commercial complexes). The more obvious.
Sun Fujie, Male, Tongyuan Design Group Co., Ltd., senior engineer.
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