Electricity: power supply or regulation systems – Input level responsive – Using a linearly acting final control device
Patent
1989-11-28
1992-12-29
Stephan, Steven L.
Electricity: power supply or regulation systems
Input level responsive
Using a linearly acting final control device
323902, 323276, 307311, G05F 156
Patent
active
051754878
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an output circuit, and more specifically, to an output circuit capable of being operated by a wide range of power supply voltages.
2. Description of the Related Prior Art
Various kinds of relays, solenoids and the like are coupled with an output circuit of a programmable controller (hereinafter, referred to as a PC), a numerical control apparatus (hereinafter, referred to as an NC) and the like, and load elements such as these relays, solenoids and the like have various electric specifications with coil voltages of DC 12 V, DC 24 V, DC 48 V, AC 100 V, AC 200 V and the like. To comply with load elements having such a wide variety of characteristics and specifications, the PC and NC are generally provided with output circuits having various characteristics and these output circuits are suitably combined and used in accordance with a combination of the loads.
As described above, although various kinds of output circuits are generally provided for the PC and NC in accordance with the kind of load, a great many kinds of output circuits are required because they are composed of combinations of DC, AC, load voltages and load currents.
Accordingly, the development of an output circuit which can be operated by a wide range of voltages is now underway, to enable a reduction of the number of the output circuits needed. For example, a circuit is available which can be operated by voltages from DC 12 V to DC 24 V or voltages from AC 100 V to AC 200 V and the like.
Note, since many loads composed of TTL's operated by a power supply voltage of DC 5 V are used, the realization of an output circuit which can be operated by voltages ranging from DC 5 V to DC 24 V or from DC 5 V to DC 48 V will greatly reduce the kinds of output circuit modules needed. Conventionally, however, it has been difficult to produce a low cost output circuit which can be operated by this range of voltages.
SUMMARY OF THE INVENTION
Taking the above into consideration, an object of the present invention is to provide an output circuit which can be operated by a wide range of power supply voltages.
To solve the above problem, in accordance with the present invention, there is provided an output circuit provided with a photo coupler for transmitting a control signal from a control circuit to an output side while being electrically isolated, a load driving transistor, and a power supply stabilizing circuit for supplying electric power for driving the load driving transistor from a load side power supply, wherein the output circuit is characterized in that the power supply stabilizing circuit includes a low voltage detection circuit and an input output short circuiting circuit and that the input output short circuiting circuit is made conductive to short-circuit the input and output of the power supply stabilizing circuit when the low voltage detection circuit detects that an input voltage to the power supply stabilizing circuit is lower than a predetermined voltage.
The input output short circuiting circuit may include a transistor bridging the power supply stabilizing circuit as a short-circuit switch element.
When the low voltage detection circuit detects that an input voltage to the power supply stabilizing circuit is lower than a predetermined voltage, the short-circuit switch element of the input output short circuiting circuit is made conductive. When a transistor is used as the short-circuit switch element, the input voltage can be effectively transmitted to the output side with a voltage drop restricted to a low level, since it has a relatively small collector-emitter saturated voltage.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of an embodiment of an output circuit according to the present invention; and
FIG. 2 is a circuit diagram of a power supply stabilizing circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows an output circuit of a PC and NC according to the present invention, wherein an output ON/OFF control signal f
REFERENCES:
patent: 3649906 (1972-03-01), Carpentier et al.
patent: 3754182 (1973-08-01), Morris et al.
patent: 4264830 (1981-04-01), Maurer et al.
patent: 4401936 (1983-08-01), van Opijnen
patent: 4535282 (1985-08-01), Nguyen
patent: 4660135 (1987-04-01), Lee
patent: 4792747 (1988-12-01), Schroeder
patent: 4967138 (1990-10-01), Obergfell et al.
patent: 5043587 (1991-08-01), Miki et al.
Davidson Ben
Fanuc Limited
Stephan Steven L.
LandOfFree
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