JPS6145542Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interface control device in a data processing device, etc., and particularly relates to an improvement for preventing unnecessary electrical signals from being sent out when power is turned on or off.

Conventionally, this type of interface control device is
There is a drawback that unnecessary electrical signals may be output from the driver circuit to the outside by passing through an unstable region such as a logic circuit during a period when the power supply voltage is not established when the power is turned on or turned off. External equipment may cause fatal malfunctions due to the above-mentioned unnecessary signals. Some types of current-driven driver circuits are designed to avoid outputting unnecessary signals, but they are expensive. In general, it has been experimentally confirmed that voltage-driven driver circuits output unnecessary signals until the power supply to the logic circuit is established. In order to eliminate the above drawbacks, conventionally, the power supply for driver circuit operation is separated from the logic circuit power supply, and when the power is turned on, the power supply for operating the driver circuit is separated from the logic circuit power supply.
It has a time sequence in which the power to the logic circuit is first turned on, then the power to the driver circuit is turned on after a certain period of time, and when the power is turned off, the power to the driver circuit is turned off first, and then the power to the logic circuit is turned off. control methods have been used, but they are complicated to operate,
There is a risk of malfunction. Another method is to provide a relay that operates with the power supplied to the logic control circuit, and use the relay to connect or disconnect the output line or power line of the driver circuit. Since the recovery time is different, and the operating current and recovery current are also different, it is difficult to control stably, and there are many drawbacks such as the risk of generating erroneous signals due to chattering or the like.

The purpose of the present invention is to solve the above-mentioned conventional drawbacks,
To provide an interface control device with a simple circuit at low cost and capable of reliably preventing the sending of unnecessary signals.

The control device of the present invention includes a logic control circuit and a driver circuit, and outputs a signal corresponding to information input to the logic control circuit from the logic control circuit and transfers it to an external device via the driver circuit. The interface control device includes a driver power control circuit that turns on when the level of a power supply voltage applied to the logic control circuit is equal to or higher than a predetermined level, and power for operation of the driver circuit is supplied through the driver power control circuit. It is characterized by

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. That is, the terminal group 101 is connected to, for example, a common path of a data processing device such as an electronic computer, and the logic control circuit 103 performs a logical function such as adapting information input from the terminal group 101 to a signal to be outputted to the outside. and sends corresponding signals from the terminal group 102 to external equipment via the driver circuit 104. The power supply for operating the logic control circuit 103 is
DC power is supplied from the example data processing device via a common bus and is applied via a power supply terminal 105 . The above is the same as the conventional one, but in this embodiment, the driver power supply control circuit 106
monitoring the voltage level of the power supply terminal 105;
When the power is above a certain level, the power is supplied to the driver circuit 104. Further, when the voltage falls below a certain level, the power supply to the driver circuit 104 is stopped. Note that a receiver circuit for receiving electrical signals from an external device is not important to the present invention, so a description thereof will be omitted.

The driver power supply control circuit is configured as shown in FIG. 2, for example. That is, the power supply terminal 105 is connected to the base of the transistor TR ₁ through the constant voltage diode ZD ₁ and the resistor, and the emitter of the transistor TR ₁ is grounded. The constant voltage diode ZD ₁ is a diode that becomes conductive when the voltage of the power supply terminal 105 reaches, for example, 80% of the rated voltage. Therefore, the power supply terminal 105
When the voltage reaches 80% of the rated voltage, transistor TR ₁ turns on, lowering the base voltage of transistor TR ₂ connected to its collector and turning on transistor TR ₂ . Since the emitter of the transistor TR ₂ is connected to the power supply terminal 105 and the collector is connected to the terminal 202, when the transistor TR ₂ is turned on, the driver circuit 10
Power can be supplied to 4. The driver circuit 104 is connected to one end of the external device 204 from a terminal 202 through a resistor R, for example, and connects to one end of the external device 204.
The other end is connected via terminal A to the collector of transistor _TR3 . The emitter of the transistor TR ₃ is grounded, and the logic control circuit 10 is connected to the base.
3 output signal is input. The above external device 20
Reference numeral 4 is, for example, a photocoupler type interface connection device, and when a current is applied from the driver circuit 104, a light emitting diode emits light, which is converted into an electric signal by a photoelectric conversion element. Therefore,
When the transistor TR ₂ is on, the output signal of the logic control circuit 103 is transmitted to the driver circuit 104.
The signal is converted into a signal suitable for the external device 204 and outputted via the converter.

In this embodiment, the power supply terminal 105 has
When a voltage E as shown in FIG. 3a is applied,
Since the transistor TR ₂ of the driver power supply control circuit 106 is in an off state until the voltage E reaches 80% of the rated value, no unnecessary current is sent out from the driver circuit 104. Then, when the voltage E reaches 80% of the rating, the transistor TR ₂ is turned on and power is supplied to the driver circuit 102.
At this time, the voltage of the logic control circuit 103 is already 80% of the rating, and the logic control circuit 103 is operating normally, so the output signal controls the transistor TR ₃ and sends a normal signal to the external device. can be sent to. 3c shows the voltage of the driver power supply controlled by the driver power supply control circuit 106, and FIG. 3d shows the voltage of the driver power supply controlled by the driver power supply control circuit 106.
This is a time chart showing the current flowing at a point. Conventionally, the driver circuit 104 also has a current supply terminal 10.
5 to the logic control circuit 103, the unstable output of the logic control circuit during the period when the voltage of the logic control circuit is low causes the driver circuit to fail during the period T shown in FIG. There was a fear that unnecessary current would flow to point A of 104, causing the external equipment to malfunction. This was extremely inconvenient for external devices that were in online operation.

In this embodiment, since the voltage is supplied to the driver circuit 104 after the logic control circuit 103 has already reached a stable state with 80% of the rated voltage, no abnormal current will flow. Even when the power is turned off, the power to the driver circuit is turned off when the voltage drops to 80% of the rated voltage, so there is no problem similar to the above.

As described above, in the present invention, since the power supply voltage of the logic control circuit is configured to supply power to the driver circuit by detecting that the power supply voltage is above a certain value, the logic control circuit is This has the effect of completely preventing unnecessary signals from being sent to external equipment due to unstable output. Furthermore, the configuration is simple and can be provided at low cost. In particular, process input/output systems,
It is extremely effective when applied to systems where each signal has an important meaning, such as a sensor-based system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of the configuration of the main parts of the above embodiment, and FIG. 3 is a time chart showing voltages and currents of the main parts to explain the operation of the above embodiment and the conventional example. In the figure, 101, 102...terminal group, 10
3...Logic control circuit, 104...Driver circuit,
105... Power supply terminal, 106... Driver power control circuit, 202... Terminal, 204... External device, ZD ₁ ... Constant voltage diode, TR ₁ to TR ₃ ...
Transistor, R...resistance.

Claims (1)

[Claim for Utility Model Registration] In an interface control device comprising: a logic control circuit 103 that generates a signal to be transmitted corresponding to input information; and a driver circuit 104 that amplifies this signal and transfers it to an external device. , a driver power supply control circuit 106 is provided in the power supply path of the driver circuit, and the driver power supply control circuit supplies power to the driver circuit when the power supply voltage supplied to the logic control circuit is equal to or higher than a predetermined value. An interface control device characterized by: