A fluorescent lamp (including energy-saving lamps) consists of a lamp holder, tube, socket, ballast, and wiring. The tube is a glass tube with two electrodes at each end connected to a tungsten filament, which only serves a heating function. Inside the tube is a thin layer of mercury vapor, which produces ultraviolet light and a small amount of blue light when current passes through it. The ultraviolet light excites the phosphor on the tube wall (modern fluorescent lamps mostly use tri-phosphor phosphors) to produce fluorescence. This light emission method has many advantages that incandescent lamps cannot match: high luminous efficiency and low power consumption.
The ballast is the heart of the fluorescent lamp, and it holds many secrets. Fluorescent lamps require a stable current to operate, which is controlled by the ballast. Traditional fluorescent lamp ballasts have two functions: during startup, the self-inductance of the ballast coil provides a momentary high voltage to break down the mercury vapor inside the tube; after startup, the ballast provides a stable operating current to ensure the tube operates normally without burning out. Electronic ballasts have complex structures. Besides ballasting, they also invert light to eliminate flicker and protect eyesight (this is what advertisements claim, but it's false).
The oldest fluorescent lamp ballasts were actually inductors, made of many turns of wire wound around an iron core. The ballast had an iron casing containing an inductor, with two wires passing through the casing connecting the coil ends. The gap between the casing and the inductor was filled with asphalt. This type of ballast had a fatal flaw: if used for too long, the inductor's temperature would rise, igniting the asphalt, which would then flow down the fluorescent lamp, potentially causing a fire. When using this type of ballast, the circuit connection should be as shown in the illustration at the end of this document.
This type of ballast has the following characteristics: it is relatively heavy, generates a lot of heat and is prone to causing a fire, and is noisy during operation. However, it has a very long lifespan, lasting over ten years, and the lamps using this ballast also have a longer lifespan and are less prone to damage.
Most fluorescent lamps nowadays use electronic ballasts. Electronic ballasts offer advantages such as small size, high efficiency, safe operation, flicker-free operation, fast start-up, energy saving, and material conservation, attracting a large number of consumers and capturing a significant market share.
Electronic ballasts are directly connected to the mains power supply. The circuit connects to a rectifier via a fuse (unofficial ballasts often lack fuses). (Note: A rectifier bridge differs from a ballast in structure and function; at least the pronunciations are different.) The rectifier converts alternating current (AC) into pulsed direct current (DC). This DC current is then filtered by a capacitor to remove ripple, eliminate flicker, and improve light quality. There are two connection methods for the filter capacitor: one uses a single 400V capacitor, and the other uses two 250V capacitors connected in series, with the middle one connected to the ballast's output terminal. The former has a lower power factor, approximately 0.6, while the latter has a higher power factor, reaching 0.95.
At this point, we must discuss the power factor. If a circuit contains only resistors, the current flowing through it will do work; this work is called active power. Many circuits operate under alternating current, and in addition to resistors, they also contain capacitors and coils. In this case, the current in the circuit is greater than the current used to do work, and the product of voltage and current is greater than the active power. The ratio of active power to the product of voltage and current is the power factor, denoted by λ. The power factor has no dimension, and its value is no greater than 1. The power factor reflects the utilization rate of current. There is a fundamental difference between power factor and efficiency. An appliance with a high power factor is not necessarily efficient, and vice versa. For example, incandescent lamps have a very high power factor, close to 1, but their luminous efficiency is very low, only 6%–15%. Fluorescent lamps, on the other hand, have a power factor of only 0.5, but their luminous efficiency is several times higher than that of incandescent lamps. LED bulbs have a pitifully low power factor of only 0.24, but their luminous efficiency is as high as 90%.
The core components of an electronic ballast are a switching transistor and a magnetic core coil. These components reduce the ballast's weight and increase its operating frequency. However, counterfeit ballasts often use these components to generate significant electromagnetic radiation, becoming a major source of pollution in homes. Except for products from a few reputable manufacturers, most electronic ballasts use inferior circuit boards and components to reduce production costs and lower prices, making them accessible to ordinary households. Some counterfeit ballasts use very thin wires instead of fuses at the AC input to further reduce costs, while others connect the AC wire directly to the rectifier. A malfunction in these cases results in a loud bang, a flash of light, a foul odor, power outages, and even fires, posing a complete safety hazard. Counterfeit electronic ballasts are easily damaged, and the accompanying light bulbs also have short lifespans, often burning down along with the ballast, creating a large amount of electronic waste and harming the environment. Furthermore, the discarded ballasts have very little value. Incinerating them releases toxic gases, severely polluting the environment.
In conclusion, electronic ballasts have unparalleled advantages over traditional ballasts. However, counterfeit electronic ballasts are inferior to traditional ballasts; they are not only inefficient and short-lived, but they also generate electromagnetic radiation, pollute the environment, affect health, and even cause fires.
