Direct-voltage power pack

Details Direct-voltage power pack Direct-voltage power pack

1999-04-15

2001-06-26

Ballato, Josie (Department: 2836)

Electrical transmission or interconnection systems

Plural supply circuits or sources

Substitute or emergency source

C361S088000

Reexamination Certificate

active

06252312

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a circuit configuration for a direct-voltage power pack of electronically controlled switchgear, as well as to a method for reading in input signals of electronic switchgear.
BACKGROUND INFORMATION
The publication “
Markt
&
Technik—Design
&
Elektronik
” [Market and Technology—Design and Electronics], issue 26, dated Dec. 22, 1987, describes voltage-monitoring integrated circuits (ICs) for microprocessor systems. The described microprocessors are used to secure volatile data in the event of a voltage failure, in that the system is set to recognize a drop below a defined threshold voltage before it occurs, thus leaving enough time to secure the data in a non-volatile memory.
Further, it is known in the case of conventional programmable control systems, particularly in the case of small control systems, to supply the control system via a separate, external, direct-voltage power pack. The supply voltage provided by this external power pack is switched, within the control system to be supplied, to an internal circuit configuration which assures protection against reverse voltage on the one hand, and on the other hand, assures a backup supply of supply voltage for the internal power supply during short-duration failures of the external supply voltage. Small control systems of this kind are generally used for smaller control tasks, which must be implemented at the lowest cost possible. For this reason, usually one and the same external power pack is used for the external voltage supply and for driving the signal inputs of the control system. The external voltage supply is switched internally, within the control system to be supplied, to a circuit configuration of an internal power pack. This circuit configuration has at least one backup capacitor for the backup supply of supply voltage, so that voltage failures of the external power pack of short duration (of the order of magnitude of approx. 10-15 ms) can be bridged by the backup capacitor, thus allowing the control system to continue functioning unaffected. Only in response to longer voltage failures, during which the internal backup voltage also collapses, is the arithmetic-logic unit of the control system switched into a defined initial state by a “power-fail” signal (PFI). The disadvantage of this, however, is that the short-duration external voltage failures, which also occur at the signal inputs of the control system, can result in misinformation in an application program to be processed.
SUMMARY OF THE INVENTION
An object of the present invention is to produce a circuit configuration for a direct-voltage power pack which assures that the signal inputs of an electronically controlled switching device, as described at the outset, are read in faultlessly. It is further intended to provide a method for faultlessly reading in the signal inputs of such switchgear.
The present invention provides a circuit configuration for a direct-voltage power pack of an electronically controlled switching device (
2
), particularly of a small programmable control system, externally supplied with direct voltage, having an arithmetic-logic unit (&mgr;c), signal inputs (
4
) and signal outputs (
6
), the external voltage supply of the switching device also being used as the voltage source for connection to the signal inputs (
4
), and the circuit configuration having a backup voltage supplier (
20
) for the backup supply of the supply voltage (U
ext
). The circuit configuration is characterized by a detector (
22
) for detecting the input voltage which is not backed up and for generating an additional signal (DC-Low) as a function of the presence of the detected input voltage, the signal inputs (
4
) being read in by the arithmetic-logic unit (&mgr;C) as a function of the state of the generated signal (DC-Low).
Advantageously, the detector (
22
) may be designed as a comparator. The circuit configuration may be used in a programmable control system, the control system having a display screen (
14
) and an operating unit (
8
). The arithmetic-logic unit (C), the display screen (
14
), the operating unit (
8
), the signal inputs (
4
) and the signal outputs (
6
) may be accommodated in a shared housing, and switching functions may be programmable by the user via a menu-driven user interface on the display screen (
14
).
The present invention also provides a method for reading in input signals in switchgear, particularly in a small programmable control system, which are externally supplied with direct voltage and have an arithmetic-logic unit (&mgr;c), signal inputs (
4
) and signal outputs (
6
), the external voltage supply of the switching device also being used as the voltage source for the connection to the signal inputs (
4
), and the circuit configuration having a detector (
20
) for the backup supply of the supply voltage (U
ext
). The method is characterized in that a binary monitoring signal (DC-Low) is generated by a comparator (
22
) as a function of the presence of the supply voltage which is not backed up, and the arithmetic-logic unit (&mgr;c) queries this monitoring signal (DC-Low) at least at the beginning of each program cycle, and the signal inputs (
4
) are read into the switching device as a function of the state of the monitoring signal (DC-Low).
Advantageously, the signal inputs (
4
) are capable of not being read in, in the event the supply voltage (U
ext
) is not present.
Important components of the circuit configuration of the present invention are a reverse voltage protection diode and a backup capacitor, the internal supply voltage being tapped off as backup voltage downstream of this circuit configuration, and, according to the present invention, the external voltage which is not backed up being tapped off upstream of this circuit configuration. In this context, the detector, particularly a comparator for comparing the external voltage to a fixed threshold value, is used to monitor the external voltage for failures of short duration which are not recognized by detecting the backup internal supply voltage. If a failure of the external supply voltage is detected, the arithmetic-logic unit of the switching device will prevent the signal inputs from being read in. Thus, misinformation due to short-duration failures of the external supply voltage is advantageously avoided.


REFERENCES:
patent: 4399538 (1983-08-01), Cholakian et al.
patent: 4728808 (1988-03-01), Bet-Esh et al.
patent: 4827149 (1989-05-01), Yabe
patent: 5081444 (1992-01-01), Nicholson et al.
patent: 5118962 (1992-06-01), Ishii et al.
patent: 5357395 (1994-10-01), Bissell et al.
patent: 5428252 (1995-06-01), Walker et al.
patent: 5691870 (1997-11-01), Gebara
patent: 5805091 (1998-09-01), Sherry et al.
patent: 0 049 462 (1982-04-01), None
patent: 05035614 (1993-02-01), None
Market and Technology-Design and Electronics, Issue 26, Dec. 22, 1987, pp. 6-13 mentioned in specification. Schematics Considered (Document in German).

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