When a 220V 50HZ AC power supply is applied to the switch-closed circuit, current flows through the ballast, and the lamp filament starter heats the filament (the starter is disconnected at the beginning, due to the application of an AC greater than 190V) The voltage causes the arc in the bubble in the starter to discharge, so that the electronic ballast related components are heated and deformed by the bimetal, and the two electrodes are brought together to form a passage for heating the filament), when the starter is two The electrodes are close together, because there is no arc discharge, the bimetal is cooled, and the two poles are separated. Because the magnetic ballast is inductive, when the circuit is suddenly interrupted, a pulse voltage of 600V-1500V will be generated at both ends of the lamp for about 1ms. The exact voltage value depends on the type of lamp. In the case of discharge, the voltage across the lamp immediately drops. At this time, the ballast limits the lamp current on the one hand, and the power supply voltage and the operating current of the lamp on the other hand. 55 is generated between. -65. The phase difference is such that the secondary starting voltage of the lamp is maintained, so that the lamp can work more stably.
Inductive ballast has a simple structure and long life. As the first kind of fluorescent lamp, the market share of the ballast is relatively large. However, due to its low power factor, low voltage starting performance and heavy energy consumption, The strobe and many other shortcomings, its market is slowly replaced by electronic ballasts, the energy loss of the inductance ballast: 40W (lamp power) + 10W (inductive ballast self-heating loss) is equal to the total power consumption of the whole set of lamps It is 50W.
2 The working principle of electronic ballast:
The electronic ballast is a converter that converts power frequency AC power into high frequency AC power. The basic working principle is:
The power frequency power supply becomes a DC power supply after a radio frequency interference (RFI) filter, full-wave rectification, and passive (or active) power factor corrector (PPFC or APFC). Through the DC/AC converter, the high-frequency AC power supply of 20K-100KHZ is output, and is applied to the LC series resonant circuit connected to the lamp to heat the filament, and a resonant high voltage is generated on the capacitor, which is applied to both ends of the lamp tube, but the lamp tube is made" The discharge "turns into" conduction state, and then enters the light-emitting state. At this time, the high-frequency inductor acts to limit the current increase, ensuring that the lamp tube obtains the lamp voltage and the lamp current required for normal operation, and in order to improve reliability, it is often added. Various protection circuits such as abnormal protection, surge voltage and current protection, temperature protection, etc.
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