DE3337280A1 - Data protection device - Google Patents

Abstract

The invention relates to a data protection device for protecting data in electronic circuits, particularly microprocessors, by detecting and early signalling of mains failure or mains undervoltage in the area of the power supply. The drop in the mains voltage is detected via an output A of the switched-mode power supply which is connected to a controlled system which represents a function of the input and output voltage. Signalling to the electronic circuit (2) is effected by a flip-flop (3) which is in series with a comparator circuit (4) and is driven by its output. For this purpose, the output (A) of the switched-mode power supply (1) is connected via a voltage divider to the non-inverting input of the comparator circuit (4) whilst the inverting input is connected to a reference point B which is set to the corresponding voltage level by a resistor (10) and a Zener diode (14). An undervoltage monitor (7) is used for detecting the operating range during the running-up of the supply voltage and switches the flip-flop back into its initial state. A battery (5) is used as additional time buffer and increases the safety of the circuit. <IMAGE>

Description

ELEKTRIZSTÄTS GMBH

Hein-Moellar-Stroße 7-11

5300BONN1 _{Βοηη> the 7th 10} . ₃₃

-2- 010-27 / PE

Data protection facility

The invention relates to a data protection facility for securing data in electronic circuits, in particular Microprocessor systems, through detection and early signaling of power failure or undervoltage in the area the power supply.

Such data protection measures are intended to protect against data loss in electronic circuits when the supply voltage is on as a result of a power failure or undervoltage, falls below a defined working range. The insufficient supply voltage can lead to an uncontrollable display as a result of data loss System status and thus cause malfunctions, e.g. in programmable logic controllers.

To protect such controls against this interference are already Circuits known as level-dependent monitoring circuit or as a direct mains voltage half-wave monitoring circuit work, In the magazine electronics (issue 5, 23, and 25 ^ 1932) circuits of this type are described, which to serve to indicate this error failure in the event of a voltage drop or power failure to signal the data memory and to this the command to To give data backup. The signal must reach the memory chip in good time so that it has the opportunity, all of them important data in a non-volatile memory area transfer. In the case of the known circuits, the requirement is relatively low circuit expenditure for a period of approximately ! G - 20 ms realized.

The invention is based on the object with little expense create a reliable circuit capable of to signal a power failure or undervoltage to the data memory up to 200 ms earlier.

■ - CX) PY * "-

8onn, October 7th, 19-3- 010-27 / PE

This object is achieved according to the invention in that the detection of the mains failure or the drop in the mains voltage below a set level is carried out by querying a controlled system in the switched-mode power supply which is a function of the input and output voltage Y, and that the signal for 3atensicnerung is given to the electronic circuit by a flip-flop, which is in series with a comparator circuit and is controlled by the output. To control the comparator circuit, the controlled system is fed from the switch via output A and a voltage divider to a non-inverting input of the comparator circuit, while the inverting input is connected to a reference point which is set by a resistor j.-generally a Zeneraiode to the corresponding voltage level enrolled: is. At the output of the switch, an undervoltage monitoring is used to reliably detect the working area while the supply voltage is running up. Once a set level has been reached, the flip-flop is switched to its initial state.

Such protective devices are necessary in order to camouflage certain data in complex systems in the event of a power failure or when the mains voltage drops below a predetermined level, to secure and protect them. In addition, to secure the status of the system so that the program can be continued after Wi ezecKenr the voltage or a defined status is set depending on the request. In order for the electronic circuit to be able to react safely, an early and safe notification of a voltage drop below the total level or a total power failure is required.

Generic power supplies that contain a switched-mode power supply, have a controlled system that is a function of inputs and Represents the output voltage of the switched-mode power supply. The supply voltage drops below the working range, the level in the power supply will first reach the limit value and above the

Bonn, October 7, 1983 -4- 010-27 / ΡΕ

Signal output A, which is connected to the controlled system of the switched-mode power supply. The output voltage U _M is kept in the working area for a short time by the energy storage of the power supply. During this time, the power failure must be signaled to the electronic circuit in order to cause it to assume a safe status. An embodiment is explained in more detail annana the drawing, which shows a simplified circuit diagram of the data protection device according to the invention.

The electronic circuit 2, for example from a Microprocessor system can consist of the switching network tail 1 with one on the? Eael U., one naes eel I th supply voltage fed. The switched-mode power supply has an output A, which is on a controlled system dss switched-mode power supply 1, the represents a function between input and output voltage. This output A of the power supply 1 is via one from the Resistors 11, 12 and 13 formed voltage divider to the non-inverting input of the comparator circuit 4 out. The inverting input of the comparator circuit 4 is applied a reference point £ whose voltage level is set by the resistor 10 and the Zener diode 14. Resistance 15 serves to stabilize aes switchover of the comparator circuit -i.

The comparator circuit 4 compares the voltage that is supplied via the voltage divider to the non-inverting input with the a: n reference point S. As soon as the voltage level falls below the set limit value, the parameter switch switches. device 4 and triggers the flip-flop 3 in series. Its output ^ J acts on input C of the electronic circuit device-2 and signals the impending voltage drop. In an advantageous embodiment, this signal occurs up to 200 ms earlier than the voltage drop is noticeable in the electronic circuit.

COPY

Bonn, October 7th, 193 -5-010-27 / PE.

So that when starting up after the return of the supply voltage j the permissible work area is reliably recognized is one Undervoltage monitoring 7 and a backup battery 5 are provided. The battery 5 acts as a time buffer and is used to safely switch the electronic circuit both when it falls off and when it falls off when the supply voltage returns.

COPY

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Claims (4)

Sunday, October 7th, 1983 -1- 010-27 / PE Claims M). Data protection device for securing data in electronic circuits, especially microprocessor systems, through detection and early signaling of power failure or Mains undervoltage in the area of the power supply, as a result characterized in that the detection of the power failure or if the mains voltage drops below a set ' Level by querying a controlled system in the switched-mode power supply (1) which is a function of input and output voltage is, takes place, and that the signal for data backup to the Electronic circuit (2) is given by a flip-flop (3), which is in series with a comparator circuit (4) and from whose output is controlled.,.,. ; - 2. Data protection device according to claim 1, characterized in that the controlled system of the switched-mode power supply (1) is guided via the output IAj and a voltage divider (6) for control to the nicnt inverting input of the comparator circuit (4). 3. Data protection device according to claims 1 and 2, thereby characterized in that the inverting input the comparator circuit (4) is at a reference point (B), which is set to the appropriate voltage level by a resistor (10) and a Zener diode (4). 4. Data protection device according to claims 1 to 3, d a d u r c h characterized in that an undervoltage monitoring (7) at the output of the switched-mode power supply (1) for safe Detection of the working area while the supply voltage is running up is used, and after reaching the set ■ level the flip-flop (3) flips to its initial state. COPY