Thyristor Semiconductor Products Page 85 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1010 120 V ac Line Input Lamp 15 W - 20 W Charging Network 5 F 400 V 0.047 F 50 V 220 k D-30A MT1 G MT2 Q401E4 Ballast 14 W - 22 W 1N4004 47 k Figure AN1010.2 120 V ac Triac/DIAC Circuit Figure AN1010.3 illustrates a circuit using a SIDAC (a simpler Thyristor) phase control network to ignite a 120 V ac capacitor is charged and added to the peak line voltage, developing greater than 200 V peak or 400 V peak to peak. Since the SIDAC is a voltage breakover (V BO ) activated device with no gate, a charging network is essential in this circuit to charge the capacitor above the peak of the line in order to break over (turn on) the SIDAC with a V BO of 220 V to 250 V. As the SIDAC turns on each half cycle, the filaments are pre-heated and in less than 1.5 seconds the lamp is lit. Once the lamp is lit, the voltage across it clamps to approximately 60 V peak (for a 15 W to 20 W lamp), and the SIDAC ceases to function until the lamp is required to be ignited again. 120 V ac Line Input Lamp 15 W - 20W K2400E SIDAC Charging Network 5 F 400 V Ballast 14 W - 22W 1N4004 47 k Figure AN1010.3 120 V ac SIDAC Circuit The circuits illustrated in Figure AN1010.2 and Figure AN1010.3 use 15 W to 20 W lamps. The same basic circuits can be applied to higher wattage lamps. However, with higher wattage lamps the voltage developed to fire (light) the lamp will need to be somewhat higher. For instance, a 40 W lamp is critical on line input voltage to ignite, and after it is lit the voltage across the lamp will clamp to approximately 130 V peak. For a given type of lamp, the current must be limited to constant current regardless of the wattage of the lamp. Thyristors for Ignition of Fluorescent Lamps (continued)

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