LED fluorescent light power knowledge

The power supply, also known as the drive, is a very important component in the lamp. The quality of the power supply directly affects the service life of the lamp. If the LED lamp is comparable to a person, then the LED light source lamp bulb is the body of the lamp tube, and the power supply is the heart of the lamp tube. Visible power is important, so the power supply is also known as the soul of the LED lamp industry.

First, the main requirements of LED drive power

1, on the double high, namely: high power factor (PF), high conversion efficiency. Products with PF = 0.9 or more have already exceeded the standards of power grids in the world, thereby reducing the pollution to the power grid. In products with high conversion efficiency, electrical energy is converted into light energy to the maximum extent and heat loss is reduced.

2. The power supply is differentiated according to the connection voltage: Wide-voltage power supply—The so-called wide voltage refers to the normal working voltage that can be adapted to most countries. In general, the wide voltage range is: 85-265VAC or 100-265VAC;

3, narrow voltage power supply: the so-called narrow voltage is actually relatively speaking, the narrow voltage range is mostly: 175-265V (also 185-265V), different power suppliers are different.

4, according to the input and output to distinguish: There are isolated power and non-isolated power points.

Simple Tip: Teach you the most earthy way to judge whether the LED driver is isolated or non-isolated power supply: The volume of the isolation is too large, and in use, the safety factor is the highest, on the contrary, the non-isolated volume is small. For cost reasons, the market for isolated products is not as broad as the non-isolated market.

Second, isolated power and non-isolated power

1. Non-isolated constant current power supply: Non-isolated means that there is a direct connection between the load end and the input end, so there is a danger of electric shock when touching the load. The most widely used at present is the non-isolated direct step-down power supply. That is to say, after the alternating current is rectified, the DC high voltage is obtained, and then the Buck and the constant current control of the non-isolated constant current source with the Buck circuit are simple and highly efficient.

2. Isolated constant current power supply: Isolated refers to isolation of the isolation transformer at the input and output terminals. This transformer may be of industrial frequency or high frequency. But it can isolate the input and output. Before and after isolation, the latter stage has no dangerous voltage to the earth, the output voltage can be equal to the input voltage or can include the range of the input voltage, it will not pose a threat to the human body, and the wide voltage performs well. Disadvantages of isolated power supply: Larger size, or smaller equivalent power.

Third, the basic principle of LED power supply

In general, LED driver power mainly through the following three steps:

1. Step-down: Step down the 220V (or 110V) power supply that is connected to the low-voltage AC.

2, rectification: After stepping down the low-voltage direct current through the LED (LED diode characteristics: one-way conductivity) into an unstable DC low voltage.

3, filtering: through the capacitor, the inductor after several filtering into a stable low-voltage DC.

4, to LED power supply.

Fourth, on the power of a few terms to explain

1. Power factor (PF): The power factor is the cosine of the voltage and current phase difference. Since the current and voltage are both oscillograms, one is a sine diagram and one is a cosine diagram. Since the two waveforms differ by 1/4 cycle (ie, 90 degrees), the PF value is formed. To increase the PF value, it is necessary to increase the PF value. A correction circuit is added to the power supply, so the power cost of a high PF value is relatively high. Without the PF correction circuit, the PF value is generally around 0.6, and the basic PF circuit can reach about 0.9 or even higher. When the PF value is low, it will pollute the power grid of the entire power supply system. When the PF value is low, the power generation efficiency of the power grid equipment becomes lower, so the country has a PF requirement for some power-consuming equipment. For 50W or less there is no clear requirement. The national requirement is that the PF value is greater than 0.6.

2. Conversion efficiency: Popular speaking is the ratio of output power to input power. For example, 10 W of electric power is consumed by a lamp, but only 8 W of electric power is used to emit light (also known as useful work). With 2 W of electrical power, heat is lost on the power device (also called: no work), then the power conversion efficiency of this lamp is 80%.