如何选择LED电源

LED power supply is a kind of power supply, also known as LED driver, which provides the power required for LED lighting.

Due to the characteristics of LED beads, led beads can only be driven by DC power. Therefore, an integrated circuit is required between the mains (mains is AC power) and the led to convert AC power into DC power. This integrated circuit is the LED control drive (commonly known as LED power supply, or LED driver).

Function of power supply:

1. AC to DC;

2. The current and voltage range required for the supply of lamps;

3. Provide circuit safety protection for lamps and lanterns;

4. Electromagnetic compatibility processing and filtering processing;

5. Other intelligent control, etc.

How to choose the appropriate LED power supply according to customer needs?

1)、 Consider input voltage

When selecting power supply for LED products, the input voltage of different regions and countries is different:

1. 100V: 2 countries (Japan and North Korea);

2. 110-130v: about 30 countries (Taiwan, China, the United States, Canada and Panama)

Malaysia, Cuba, Lebanon, Mexico, etc.);

3. 220-230v: about 120 countries (Britain, Germany, France, China, Singapore, Hong Kong (200V), Italy, Spain, Greece, Austria, Netherlands, Philippines, Thailand, Norway, Singapore, India, New Zealand, Australia, etc.)

Indoor power supply:

LED counter lighting and indoor LED advertising signs & lighting can choose ordinary indoor power supply

Warm tip: it is recommended not to use the power supply with fan in a quiet environment. The internal circuit of the wall is complicated, and the low-frequency radiation is strong. The mobile phone shooting can intuitively flash. The EMC power supply is preferred and the grounding is well done.

Rain proof power supply:

The LED lighting project is basically outdoor. Generally, the three protection measures (rain proof, dust-proof and moisture-proof) are selected.

Warm tip: select the power supply of different protection processes according to the actual needs. Measures for delaying environmental impact: three prevention process,

Glue filling process (measures to completely isolate the environmental impact).

2)、 Consider the working environment of power supply

Outdoor power supply: it is recommended to use rain proof power supply or waterproof power supply with glue filling process in coastal areas and severely corrosive environment.

Waterproof power supply: the power supply of some lighting projects needs to be immersed in water, so the power supply with special glue filling process must be selected to prevent rain from entering the power supply and causing power failure.

3)、 Power conversion efficiency

Power: power refers to the amount of work done by an object in unit time.

P = w/t = UI

Common power terms in LED field:

1. Input power (whole lamp power): input power = power output / conversion efficiency;

2. Output power: output power = power supply output voltage x output current;

3. Short circuit power: the power measured by the input power meter after the output end is directly short circuited, and the general manifestation is jumping state (burping);

4. No load power: the power when the output load is not connected (LED lamp is not connected) (although the output load is not connected, it is caused by the loss of electronic components when connected to the power supply).

Startup time (startup time): the time difference between the input of mains power and the lighting of LED lamps. ERP requirements < 0.5s@220Vac , DLC requires < 1s@100V 。

DLC certification: it is the performance certification standard of commercial lighting products in North America.

Temperature drift: the phenomenon of output current change caused by the temperature change around the power supply. Example: comparison table of output load and temperature of Mean Well ELG-240.

Efficiency (conversion efficiency): the ratio of output power to input power (reflecting the energy conversion capacity of the equipment). Origin of efficiency:

During the process of AC input to DC output of power supply, there will be a part of electric energy loss due to circuit operation (the lost electric energy is released in the form of heat). The less the loss, the higher the conversion efficiency of the power supply, the smaller the heating capacity of the power supply, and the more energy-saving the lamp; On the contrary, the lower the conversion efficiency, the greater the heat generation and the worse the energy conservation.

The input power is 100W and the output power is 90W. The conversion efficiency of this power supply is 90W / 100W = 90%.

Power factor: ratio of active power to apparent power in AC circuit (PF = active power / apparent power).

Active power: the power actually consumed (the power tested by the electric parameter meter is active power).

Apparent power: the product of the effective value of voltage and the effective value of current in a sinusoidal AC circuit.

Power factor is a factor to measure the efficiency of electrical equipment. The low power factor indicates that the reactive power of the circuit is large, the utilization rate of the equipment is low, and the power supply loss of the line is increased.

For example, a 20W lamp with PF value of 0.5 needs 40W power provided by the power grid to work normally, and the extra 20W power loss will not be displayed on the household watt hour meter and will not play a practical role, which increases the power supply loss of the line.

American energy star and European ERP and other energy efficiency certification have mandatory requirements on power factor. The PF value of energy star is required to be greater than 0.9 within the rated input voltage range. The European ERP requirements are as follows:

Why do end customers and governments care about power factor (PF)?

Low pf drive power will reduce the load capacity of the transmission line; On the contrary, the higher the power utilization rate per unit wire diameter of high PF drive power supply products. With the arrival of the energy crisis era, the government will control the power factor characteristics of electronic products.

Impact on LED lamps?

1. High PF driving power supply is adopted to reduce the resource occupation of reactive current on the power grid;

2. High PF drive power supply is adopted to meet the energy efficiency requirements of the global high-end market.

What is harmonic?

The distortion of voltage and current waveforms is caused by the use of inductive components in the LED driving power supply, so any component different from the power frequency can be called harmonic.

The harmonic of LED power supply is mainly caused by current distortion. The distorted waveform will be transmitted to the power grid again and cannot be used by the electrical equipment. If the harmonic quantity exceeds a certain limit, it will cause various electrical equipment to work abnormally and increase the power consumption of the power transmission line.

Harmonic hazard

Other electrical equipment in the same power grid will be interfered (direct interference and mutual interference) and generate faults (noise and flashing light), and the "neutral line" current of the power grid will be overloaded, affecting the transmission capacity.

4)、 Complete power protection function

With the continuous improvement of the national awareness of safety, it is doomed that safety is no trivial matter. All potential safety hazards are major problems. If the power supply has no protection function, there are serious safety risks.

The power supply is the LED energy provider, and the LED system has no immunity to the voltage and current provided by the power supply. In case of overvoltage, overcurrent and short-circuit abnormality, the power supply must have overvoltage protection, overcurrent protection, short-circuit protection and other functions, so that the power supply is in the protection state (cut-off power supply or burping mode), and prevent the LED from burning out or serious safety problems such as fire. This will also more effectively protect the LED system.

Short circuit protection: it is designed to prevent the output end of the power supply from being damaged due to short circuit during operation, and also to prevent transistors from breakdown due to excessive short circuit power.

Overvoltage protection: when the load voltage of the lamp exceeds the maximum output voltage of the power supply, the IC judges that the operation is abnormal and the output burps. When the power supply voltage returns to the normal range, the protector will automatically switch on.

Open circuit protection: the protection designed to prevent the open circuit voltage from being too high (high open circuit voltage, easy to be electrocuted, high open circuit voltage, and power output capacitor withstand voltage exceeding the standard).

Stroboscopic: refers to the fluctuation of the electric light source and luminous flux at a certain frequency. The fringe distribution can often be found by pointing the mobile phone at the light source, which is caused by stroboscopic.

Some degree of stroboscopic will not attract attention, and there is no physical discomfort.

Human eyes are not sensitive to flicker above 60Hz. The power frequency of the output terminal of LED constant current power supply is generally 100Hz or above. When photographing with CCD photosensitive imaging (mobile phone, camera), water ripples will appear due to different sampling frequencies. However, it is related to the preset frequency, photosensitive element and shutter speed of mobile phones and cameras, so this test method is not necessarily accurate, but a simple test method.

5)、 How to consider the price?

Do not blindly pursue high prices and do not excessively choose low prices.

The higher the price, the better. This is a wrong choice. If the LED has a life of 50000 hours and the power supply of 100000 hours is selected to match it, this is excess quality and waste of quality.

Of course, we should not blindly choose products with low prices. The low prices determine the source of power supply parts, disassembled parts, parts with hidden quality problems, etc., which will seriously affect the reliability and stability of power supply, and even have greater safety risks.