Electrical transmission or interconnection systems – Personnel safety or limit control features – Interlock
Patent
1991-06-17
1993-08-24
Ng, Jin F.
Electrical transmission or interconnection systems
Personnel safety or limit control features
Interlock
307354, 307647, H03K 5153, H03K 1713
Patent
active
052392090
ABSTRACT:
A zero crossing detection circuit produces an output signal which changes state to indicate the occurrence of a positive-going zero crossing of an AC input signal. The circuit includes first and second input terminals, a current sensitive switch such as an opto-isolator, first and second current regulators, and a voltage limiter. The first current regulator is connected in series with the current sensitive switch, and the voltage limiter is connected in parallel with the first current regulator and the current sensitive switch. The second current regulator is connected between the first input terminal and the parallel combination of the voltage limiter and the first current regulator and the current sensitive switch. The first current regulator limits current through the current sensitive switch to a first current limit level, and the second current regulator limits current flowing between the first and second input terminals to a second current limit level which is greater than the first current level. The zero crossing detection circuit offers the ability to sense zero crossings of AC input signals having a wide range of AC voltages.
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JA 0223218 Sep. 90 "Zero Cross Detection Circuit for AC Power Source" Kazuhiko Masamoto.
SU 1396259 May 88 "AC Voltage Zero crossing pulse shaper-has second lead of third resistor connected to base of the first transistor".
Barte William B.
Griswold Gary L.
Kirn Walter N.
Minnesota Mining and Manufacturing Company
Ng Jin F.
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