| 摘要 |
1,208,936. Automatic current control. SYLVANIA ELECTRIC PRODUCTS Inc. July 3, 1968 [July 3, 1967], No.31730/68. Heading G3R. [Also in Division H2] A fluorescent lamp regulating arrangement comprises an electric circuit for applying periodic ionizing pulses to the lamp thereby to support an arc discharge in the lamp, the circuit being responsive to a control voltage dependent on the lamp current as sensed by a transformer. As shown, series connected fluorescent lamps L1, L are supplied from A.C. source terminals A, C by way of the primary winding T3 of a current sensing transformer and an auto-transformer T1, T2 associated with a pulse-producing circuit constituted by a triac V1, a diac D1 and capacitors C1, C2, C3. The secondary winding T4 of the sensing transformer is connected over a resistor R1 to the input terminals A, C to produce a reference flux in the transformer core, and the interaction of this flux with the current-dependent flux due to winding T3 produces a control voltage in a tertiary winding T5; this voltage is applied to the pulse-producing circuit in series with capacitor C2 thereby to control its rate of charging and to cause a phase shift of the ionizing pulse in the direction required to correct a deviation of lamp current away from normal. Thus, if the lamp current increases the arrangement is such that the control voltage induced in tertiary T5 decreases, the voltage available to charge capacitor C2 increases and capacitor C2 reaches the breakdown voltage of diac D1 earlier thereby triggering triac V1 and causing the primary storage capacitor C1 to discharge earlier in the cycle, whereby the phase of the ionizing pulse is advanced to limit conduction in the lamps and the pulse amplitude is reduced because capacitor C1 has charged to a lower voltage, further limiting ionization and lamp current. The sensing transformer may be associated with a photo-resistor or thermistor responsive to lamp current, or with alow pass filter to attenuate non-linear distortions in the lamp current sensed by the transformer.
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