The working principle of fluorescent lamp is briefly described.

Fluorescent lamp, or fluorescent lamp, tube, cathode fluorescent lamp and tube, is a kind of lighting device and belongs to arc lamp. The traditional fluorescent lamp, that is, low-pressure mercury lamp, uses the principle that low-pressure mercury vapor releases ultraviolet rays after being electrified to make the phosphor emit visible light, so it belongs to low-voltage arc discharge light source.

The cathode fluorescent lamp is filled with low-pressure argon or argon-neon mixed gas and mercury vapor, while the inner surface of the glass cathode fluorescent lamp is coated with a layer of fluorescent powder coating, and filament coils made of tungsten are arranged at both ends of the lamp tube (this tungsten filament coil will be coated with "electronic powder", and its components are composed of alkaline earth metal compounds such as strontium and barium).

When the power supply is turned on, the current first heats up through the filament, releasing electrons (the electrons here are released by electronic powder), which will turn the gas in the tube into plasma and increase the current in the tube. When the voltage between two groups of filaments exceeds a certain value, the lamp tube begins to discharge.

Mercury vapor emits ultraviolet rays with wavelengths of 253.7nm and 185nm, and the fluorescent powder coating on the inner surface of cathode fluorescent lamp absorbs ultraviolet rays and emits visible light with longer wavelength. The color of the emitted light is controlled by the proportion of phosphorus components, and the glass tube can prevent harmful ultraviolet rays and other harmful substances such as mercury from leaking out.

There is a positive feedback relationship between the discharge current and the on-resistance of cathode fluorescent lamp: when more current flows into cathode fluorescent lamp, more gas is ionized, and the on-resistance in the tube decreases continuously, so more current will flow into cathode fluorescent lamp.

If the cathode fluorescent lamp is directly connected to a fixed voltage power supply, the cathode fluorescent lamp will burn out quickly due to the rising current. Therefore, an auxiliary circuit is needed to control the current entering the cathode fluorescent lamp at a fixed level. This current control circuit is usually called ballast.

The traditional ballast is actually an inductor. When the on-resistance drops to a very low level, the fixed inductance and copper consumption of the ballast make the on-current close to a constant value and start stable operation.

Traditional ballasts need to be equipped with a small component called up converter (commonly known as "bubble jumping") to make the pressure difference between filaments reach the level that cathode fluorescent lamps can discharge. The latest electronic ballasts don't need an upconverter, because the work of the starter is already included in the ballast.

Extended data:

The luminous efficiency of fluorescent lamps is very high, as high as 104 lumens/watt. When you need high ambient illumination, you can choose this efficient light source.

Fluorescent lamps have high lumen maintenance rate and small light attenuation. Assuming that the life accumulation of fluorescent lamps has reached 8000 hours, some fluorescent lamps with good quality can still maintain more than 90% luminous flux output; Even if the quality is poor, it can reach 80% luminous flux output. Incandescent lamps and halogen lamps can't do this.

Fluorescent lamps generally have four common whites: warm white (3000k), white (3500k), cold white (4000k) and sunlight (6500k). These different color temperatures depend on phosphors with different colors on the tube wall. Fluorescent lamps have a long service life, up to 12000 hours. Fluorescent lamps are generally inexpensive and are substitutes that can be bought everywhere.

Due to its luminous principle, fluorescent lamps must have a certain length of pipe diameter. Therefore, the lamp body is relatively large, and the design of the lamp is difficult. Generally, it can only be used for basic lighting, not as a accent lighting.

The display index of fluorescent lamps is good or bad, and its color rendering is based on the types of phosphors. If the phosphor in the lamp is five primary colors, the display index can reach 90+ (but the price is more expensive).

Fluorescent lamps can be dimmed, but the control technology is much more complicated than incandescent lamps and requires special driving appliances. Stroboscopic This is the fatal point of fluorescent lamps-stroboscopic. Of course, all gas discharge lamps have stroboscopic phenomenon, which is caused by the periodic change of current.

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