Electrical transmission or interconnection systems – Switching systems – Condition responsive
Patent
1995-01-24
1996-09-03
Shoop, Jr., William M.
Electrical transmission or interconnection systems
Switching systems
Condition responsive
327432, 323234, 323235, 32420714, 32420722, 422 62, 340620, H01H 3500
Patent
active
055526446
DESCRIPTION:
BRIEF SUMMARY
This invention relates to proximity switches or sensors, and in particular to a two wire AC power supply for proximity switch integrated circuits.
Accordingly, one aspect of the present invention provides a two wire AC power supply for a proximity switch integrated circuit, wherein at least some circuitry associated with the power supply is provided within the integrated circuit.
Preferably the two wire AC power supply comprises a bridge rectifier, an output of which i connected in parallel across a voltage regulator and also in parallel across a thyristor, an output of the regulator being connected in parallel to a diode connected in series to a storage capacitor, the cathode of the diode being connected to the storage capacitor, the output of the regulator further being connected to one input of a comparator, another input of the comparator being held at a constant reference voltage, an output of the comparator being connected to a first input of an AND gate, a second input of the AND gate being connected to an output from the proximity switch indicative of the switch state, an output of the AND gate being connected to a gate of the thyristor, and wherein further, the comparator and the AND gate are provided within the integrated circuit.
A current limiting circuit connected in parallel with a switch may be provided between the output of the voltage regulator and the anode of the diode, the current limiting circuit and the switch also being provided within the integrated circuit.
The integrated circuit may be implemented in bipolar transistor technology, or in any other suitable transistor technology.
Preferably, the comparator comprises a PNP differential pair Q1, Q2 powered via a further current source Q7, Q8, the first input of the comparator being connected to means for dividing down the input voltage QD1, R1, R2 and QD2, the divided down voltage being applied to the base of the transistor Q1 the second input being connected to further means for dividing down a regulated voltage V3V5 and for providing hysteresis R3, R4, R5, Q5, Q6 the regulated voltage being derived from the integrated circuit, the collectors of the differential pair Q1, Q2 being connected to a differential to single-ended converter Q3, Q4 an output from the comparator being developed at the collector of a further transistor Q6, the collector of which is connected to a current source Q9, and the base of which is connected to the further dividing down means.
Preferably, the constant current circuit comprises two NPN transistors QCC1, QCC2 connected in parallel, and further connected between their collectors and bases in parallel with a resistor R100UA, the emitters being connected to a parallel arrangement comprising a resistor R2500UA connected in parallel between the base to emitter junction of a further NPN transistor Q2500UA which is connected in series with a resistor RTHUR1, the collector of the further transistor Q2500UA being connected to the bases of the two NPN transistors QCC1 and QCC2.
Preferably, the switch connected in parallel with the constant current circuit comprises a resistor RSAT connected to the collector of a transistor QDARL having a resistor RODARL connected between its base and emitter, the emitter of the transistor QDARL being connected to the base of a transistor QSW, the transistor QSW having a resistor RQSW connected between its base and emitter, the emitter of transistor QSW further being connected to a parallel arrangement comprising a resistor R50MA and the base to emitter junction of another transistor Q50MA which is connected in series with a resistor RTHUR2, the collector of the other transistor Q50MA further being connected to the base of the transistor QDARL.
Preferably the base current to transistor QDARL is provided by a current mirror QM4, QM5, QM6, QM7, QM8, input current to the mirror being controlled by a signal derived from the proximity switch.
According to a second aspect of the present invention there is provided an integrated circuit for use in a two wire AC power supply for a proximity
REFERENCES:
patent: 4757341 (1988-07-01), Tanigawa
patent: 4803418 (1989-02-01), Ritchie
patent: 4924122 (1990-05-01), Harris
Bizley Arthur J.
Calder Douglas W.
Femal Michael J.
Golden Larry I.
Paladini Albert W.
Shoop Jr. William M.
Shrout Larry T.
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