Low cost AC switch for electroluminescent lamps

Details Low cost AC switch for electroluminescent lamps Low cost AC switch for electroluminescent lamps

1993-06-01

1994-09-13

Pascal, Robert J.

Electric lamp and discharge devices: systems

Plural power supplies

Plural cathode and/or anode load device

3151693, 315324, 315209R, H05B 3700

Patent

active

053471989

ABSTRACT:
DC bias does not accumulate on an EL lamp connected in series with a switch circuit including, in one embodiment, two, asymmetric, parallel current paths, one current path for each half cycle of the AC. The first current path includes a first diode for preventing DC bias on the lamp, the first diode is in series with a first transistor between a first terminal and a second terminal. The second current path includes a second diode in series with the base-collector junction of a second transistor between the first terminal and the second terminal. The base of the first transistor is connected to the emitter of the second transistor and to a control terminal. The first transistor and the second transistor are opposite conductivity types. The second current path takes advantage of the fact that the current through an electroluminescent lamp is small and uses the control terminal as a source of current for the lamp. In another embodiment, a large capacitor in series with the electroluminescent lamp prevents DC bias from accumulating on the EL lamp.

REFERENCES:
patent: 3813575 (1974-05-01), Webb
patent: 3908150 (1975-09-01), Webb
patent: 5095248 (1992-03-01), Sato
patent: 5172032 (1992-12-01), Alessio

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