Gas discharge lamp refers to the gas, metal vapors or several gases and metal vapors mixed discharge and light-emitting lamps, through the gas discharge will be converted to light of electrical energy. There are many types of gas discharge, with more glow discharge and arc discharge: glow discharge is generally used for neon lights and indicators; arc discharge can have a very strong light output, lighting sources are used arc discharge. Fluorescent lamps, high-pressure mercury lamps, sodium lamps and metal halide lamps are the most widely used discharge lamps for lighting. Gas discharge lamps in industry, agriculture, health care and scientific research in the field of extremely wide range of uses.
Second, what kinds of gas discharge lamps
1, high-intensity gas discharge lamps: due to the temperature of the tube wall and the establishment of light-emitting arcs, the light-emitting tube surface loading of more than 3W/cm2 discharge lamps. Such as high-pressure mercury lamps, high-pressure sodium lamps, metal halide lamps.
2, low-pressure discharge lamps: fluorescent lamps (low-pressure mercury lamps), low-pressure sodium lamps, induction lamps. One of the fluorescent lamps should be the most widely used, the largest amount of gas discharge light source. It has a simple structure, high luminous efficiency, soft light, long life and other advantages. The luminous efficiency of fluorescent lamps is 4-5 times that of incandescent lamps, and the life span is 3-8 times that of incandescent lamps, which is an energy efficient light source.
The types of gas discharge lamps are mainly the above two, then what are their characteristics?
Three, what are the characteristics of gas discharge bulbs
1, with high efficiency, they can be 25-30% of the input electrical energy into light output.
2, long life. The service life is up to 10,000 hours or more than 20,000 hours.
3, radiation spectrum is selective. By selecting the appropriate light-emitting substances, the radiation spectrum can be focused on the required wavelengths, but also can use several light-emitting substances at the same time, in order to obtain the best combination of spectra.
4, light output maintenance characteristics, in the end of life can still provide 60 ~ 80% of the initial light output.
Four, what is the working principle of the ballast of the gas discharge lamp
The work of the gas discharge lamp can not be separated from the gas discharge lamp auxiliary equipment, because it can not be connected to the circuit alone, it must be connected to the circuit with triggers, ballasts and other auxiliary appliances in order to start and stabilize the work. Ballast principle of operation are the following:
1, resistance ballast
Resistance ballast is dependent on the resistance of the voltage is proportional to the relationship between the current to regulate the lamp current, in the DC power supply of the HID light source circuit in the application of the resistor ballast, the circuit is simple, easy to install. When taking into account the efficiency of the circuit and the working stability of the lamp, there is VLAMP = 0.6Vn when η = 60%, it can be seen that the ballast resistor power consumption is very large, the circuit's working efficiency is very low.
Resistance ballast in the AC power supply has a small number of applications, such as self-ballasted high-pressure mercury lamps using tungsten filament as ballast parts, many high-frequency reference ballast is also made of resistance. The use of resistive ballasts in AC circuits affects the waveform of the lamp current, the luminous efficiency of the lamp decreases, and the stability of the circuit deteriorates, but the power factor of the circuit is relatively high.
2, capacitor ballast
Capacitors work in low-frequency AC circuits, the lamp voltage waveform approximates a square wave. Because the capacitor can not limit the instantaneous current, so it will produce a very high peak lamp current, which makes the lamp current waveform is seriously distorted, the electrode of the lamp has a very harmful effect, resulting in shortening the life of the lamp, and make the lamp light flash, so the capacitor ballast method is rarely used in low-frequency AC circuits.
3, inductive ballast
Inductive ballast is the use of inductors work on the principle of self-inductance, that is, it is through the inductor voltage proportional to the rate of change of the current time to regulate the lamp current. Because the lamp current lags the supply voltage by a certain phase (so also known as hysteresis ballast), the circuit's power factor is low, generally in the 0.5 or so. Inductive ballast is more sensitive to changes in supply voltage, and the ballast effect is less stable. Inductive ballast has the advantages of simple circuit, lower loss than resistive ballast, improved lamp current waveform and stable operation, etc. It is widely used in various types of gas discharge lamps.
In high-pressure discharge lamps, in order to obtain a higher ignition voltage, can be used leakage transformer as inductive ballast application. Magnetic leakage transformer belongs to the hysteresis type ballast, although the body is large and bulky, the noise is also large, but it can obtain higher than the supply voltage of the open-circuit voltage, used for the lamp voltage is higher than the supply voltage of gas discharge lamps (such as neon lamps, cold cathode lamps, ultraviolet lamps, etc.), can significantly improve the starting performance.
4, inductance, capacitance (LC) ballast
LC ballast has two forms, one is composed of inductance and capacitance in series ballast, usually designed to capacitive impedance than the inductive impedance, so that the circuit is generally capacitive. When the capacitive reactance is 2.76 times the inductive reactance, the circuit's constant current characteristics are most stable. The lamp current of this ballast circuit exceeds the phase of the supply voltage by a certain amount and belongs to the overrun type ballast.
LC ahead of the type of ballast power consumption is smaller, has a better current stabilization characteristics, the short-circuit characteristics of the lamp start-up is also good, and the lag type of inductive ballast with the application of the circuit can be better to improve the power factor. But because the lamp current over zero, the peak value of the power supply voltage and lamp voltage in the opposite direction, repeated ionization of the voltage is lower, resulting in repeated ignition ability is poor.
5, electronic ballast
Electronic ballast is a combination of electronic components into a new type of ballast, which is essentially a power converter, will be converted to AC frequency AC 20 ~ 100kHz AC voltage to start and light fluorescent lamps. The use of high-frequency AC electronic ballasts can improve the luminous efficiency of the lamp, avoid the noise of the industrial frequency, reduce the size and weight of the ballast, improve the power factor, and easy to realize intelligent control. In principle, it is applicable to all kinds of gas discharge lamps, but the application of fluorescent lamps, especially compact fluorescent lamps, is developing more rapidly.