Why does the brightness of fluorescent lights decrease in winter?
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I recently thought of a question: why does the brightness of fluorescent lights seem lower in winter compared to now?
The principle of light emission in fluorescent lamps is that when mercury vapor conducts electricity between the electrodes at both ends of the tube, it emits invisible ultraviolet light, which in turn stimulates the phosphor coating on the inner wall of the tube to emit light. The efficiency with which mercury vapor converts to ultraviolet light when it conducts electricity is proportional to the pressure of the mercury vapor, and the pressure inside the tube is in turn directly proportional to the temperature of the surrounding environment. The lamp is designed assuming an ambient temperature of 25 degrees Celsius; in winter, due to the lower temperatures, the pressure inside the lamp becomes lower than the designed value, resulting in a reduced luminous efficiency. The degree of reduction is proportional to the decrease in temperature; when the surrounding temperature is too low, the lamp tube cannot even be ignited.
GoodLuck is great; I really hope there will be more posts aimed at spreading knowledge, as well as more involvement in management. I hadn’t really paid attention to whether the fluorescent light tube was bright or dim; when it became dim, I called an electrician to replace it. I never thought of this reason – after turning on the air conditioner, it should have become brighter.
Under the influence of high voltage at both ends of the lamp tube, electrons accelerate as they move between the poles of the light. As these electrons move, they collide with the argon molecules inside the tube, causing them to ionize rapidly. Argon ionization generates heat, and this heat causes mercury to vaporize; subsequently, the mercury vapor is also ionized, emitting intense ultraviolet light. Under ultraviolet excitation, the phosphor inside the tube wall emits nearly white visible light. Therefore, an increase in ambient temperature facilitates the vaporization of mercury; it is common to see droplets of liquid mercury inside fluorescent lights in winter, and this phenomenon occurs because low ambient temperatures cause the supersaturated mercury vapor contained within the fluorescent tubes to turn into liquid mercury droplets. Additionally, the main reason why fluorescent lamps have difficulty starting in winter is not the ambient temperature, but rather an issue with the lamp’s ballast. The pulse voltage generated by the ballast is only 400–500V at low levels, and can reach up to 1000V at high levels. Sometimes, inferior ballasts are still functional in summer, but in winter, due to insufficient high voltage generation, they are unable to enable the fluorescent lamps to start shining promptly.
Why is the voltage at the ballast input for fluorescent lamps 220V, while the voltage at the ballast output is only a few dozen volts? What is the reason?