40W fluorescent lamp electronic ballast circuit

The figure shows that input from the varistor overvoltage protection role. VDi - VD4 rectifier, L1, C2, q filtering. R, c9 and VD6 composition oscillation starting circuit, the transformer T and H, V and other components transformer coupling high-frequency
40W fluorescent lamp electronic ballast circuit - schematic

oscillation circuit. Choke Island, C4 and C7 etc. LC series resonant circuit. Among them, the island is the series resonant inductor, but it is also chokes. PTC thermistor element preheating the lamp cathodes. RN, RI2, vdG, Ru, vs code composed of the protective circuit and the like. L. Can increase the rectifier diode conduction angle of the rectifier bridge input terminal of AC current tends to be continuous, power factor increased to 055 by the close 08. After the power is turned on, the entire flow filter output DC voltage of H {c9 start capacitor is charged through the resistor R4. When the voltage across the c9 reached about when 32V, diac vIX avalanche conduction, switching power supply base for the pole tube injection current, K is turned on first. By coupling Ts,, V2 turns conducting, high-frequency high voltage is applied across the lamp output. The capacity of the island above the C4 capacity, and by the TPTC thermistor resistance at room temperature only 200n left and right, so after power flows through the filament current is not 0, only by PTC and G. Filament current flowing through the PTC to raise its temperature, resistance increases. After about 1 second, reaches the Curie point temperature, the resistance value of 10M n above, filament preheat current through C4, immediately aroused k, C4 and other series circuit of a resonance in the start capacitor C4 high voltage is generated across the lamp start ignite. Once the win lamp burning, the island only play a limiting role. The protective circuit is: Once the lamp and the lamp can not start aging, etc., between L2 and the filament is bound to appear high EMF, the Rt., R12 partial pressure, sufficient to zener diode VDg breakdown. SCR vs Having obtained the trigger voltage is turned on, so that V3 from off jump into saturated conduction state, the collector potential is only about 0.2V, forcing Vz off, the oscillation circuit stop Jt oscillation, the realization of ballast protection function. Only troubleshooting, reconnect the power to light the lamp.

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