China manufacturer of magnetic ballasts for metal halide flood lights & hps flood lights

Energy-saving electronic ballast and the preheat start circuit

(1) The necessity of energy saving ballast:

● fluorescent electric light source is a cathode preheat start;

● High pressure cold start, easy to damage the filament (sputtering), cathode wall early black and shorten lamp life;

● Preheat start, can reduce the start-up voltage (300 to 400V);

(2) The ideal start-up procedures and requirements:

● Start lamp voltage (<glow discharge voltage), give the filament preheating (preheating current, voltage should not be too large, the cathode in order to avoid damage from overheating), more than 0.4 seconds;

Cathode of thermionic emission temperature (1000k <tc <1160k), to light rapid high voltage, the lamp rapid start (the many start), by the glow discharge into the arc discharge;

● arc discharge should be cut off after the preheating current to maintain the thermal electron emission cathode depend on the temperature of the hot spots;

● multi-lamp drive, and strive to match the start capacitor and the start-up current balance;

(3) Preheat start circuit --- the energy saving ballast should meet the requirements of the open circuit voltage, preheat current warm-up time:

● PTC thermistor (Figure 3-10) - For 40W:

- Resistance 80 ~ 3000Ω, the Curie point of 60 ° C ~ 120 ° C;

- Below the Curie point, the low resistance conduction preheating the cathode; was high resistance above the Curie point, automatically cut off the circuit, the LC resonance, start the lamp lit;

Power is larger, should select a low resistance and large size; warm-up for a long time, should choose Curie point, size the-PTC selection