Noise immune power switch for automotive accessories

Details Noise immune power switch for automotive accessories Noise immune power switch for automotive accessories

1990-04-23

1991-12-17

Pellinen, A. D.

Electrical transmission or interconnection systems

Vehicle mounted systems

Automobile

307 101, 307116, 322 99, 322DIG6, H02H 718

Patent

active

050737210

ABSTRACT:
A noise immune electronic switch is connectible between a cigarette lighter socket of a vehicle and a plug-in accessory device. The electronic switch is turned on in response to the drop in B+ voltage at the lighter socket when the automobile starter is engaged for rapidly charging an integrating capacitor that is coupled to a comparator. The other comparator input is connected to a source of reference voltage. The output of the comparator, when switched, drives a transistor switch conductive to couple the B+ line between the cigarette lighter socket and an output connector. A filter passes alternator ripple voltage on the B+ line to an amplifier where the ripple is amplified and inverted. The negative half cycles of the ripple voltage charge the integrating capacitor to maintain the comparator output switched. A defeat diode is connected between the integrating capacitor and the output connector such that the capacitor cannot charge when the transistor switch is non-conductive and an accessory device is connected to the output connector. A turn-on transistor is coupled between the storage capacitor and the integrating capacitor and is turned on by the sharp drop in voltage on the B+ line when the automobile starter motor is engaged.

REFERENCES:
patent: 3492559 (1970-01-01), Harris
patent: 4209816 (1980-06-01), Hansen
patent: 4493001 (1985-01-01), Sheldrake
patent: 4733100 (1988-03-01), Nusairat et al.

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