Electricity: electrical systems and devices – Safety and protection of systems and devices – Voltage regulator protective circuits
Patent
1994-07-11
1996-07-02
Pellinen, A. D.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Voltage regulator protective circuits
307 43, 323251, 363 65, H02H 704
Patent
active
055328946
ABSTRACT:
A power supply is provided for a presentation system having a light source which allows for overdriving of the light source, but protects against transient surges on the input line when overdriving the light source. The power supply includes an input line connected to the external ac source, two output lines, and a relay selectively connecting the input line to one of the two output lines. The relay is indirectly controlled by a voltage sense circuit which converts the ac source voltage to a dc output voltage. The dc output voltage is examined to determine whether the input line is in a low- or high-voltage state, the high-voltage state corresponding to a surge on the line. The output lines are coupled to the load line (leading to the light source) in such a manner that the ac voltage source, when applied to the first output line, will produce a lower voltage at the lamp than that produced when the ac voltage source is applied to the second output line, thus overdriving the lamp when the relay connects the input line to the second output line. As long as the input line is not surging, i.e., while it is in the low-voltage state, the relay connects the input line to the second output line to allow for overdriving. When a surge is detected, the relay switches the input line to the first output line. The voltage sense circuit includes a hysteresis component which automatically adjusts the predetermined threshold to prevent constant switching of the voltage sense circuit output when there are only minor deviations in the voltage near the threshold.
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Griswold Gary L.
Kirn Walter N.
Minnesota Mining and Manufacturing Company
Musgrove Jack V.
Pellinen A. D.
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