JPH0213860B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a negation circuit that can fail-safely obtain negation information.

In general, in railway signals, information when a train enters a controlled section is processed using a closed circuit system, where the voltage is always on and there is no voltage due to the train entering or a circuit failure. The information when the train moves out of the control section is that there is no voltage at all times, but as the train moves out, it becomes energized.
In addition, it is processed using an open circuit system that eliminates the voltage even in the event of a circuit failure ("Railway Signal Handbook" published by the Signal Safety Association, December 1964, p. 1259).

However, in such a circuit, information on train entry and information on train departure must be processed in separate electrical circuits, the circuit system cannot be unified, and information on train entry cannot be processed when the train advances. This method has the disadvantage that it is a reactive measure that only discovers circuit failure when the desired output voltage is not present.

SUMMARY OF THE INVENTION An object of the present invention is to provide a negation circuit that can obtain negation information in a fail-safe manner, and can immediately check for failures in a circuit that processes input information in an open circuit manner. do.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings.

In Fig. 1, 1 is an input terminal for information A with truth values "1" and "0", and 2 is an alternating current that oscillates the information A at a peak value (amplitude) corresponding to the truth value "1" and "0". 3 is a window comparator having an asymmetric error characteristic such that the oscillation output becomes zero in the event of a failure; 4 is a capacitor for AC coupling the signal conversion circuit 2 and the window comparator 3;

The signal conversion circuit 2 outputs an AC signal B having a peak value higher than the level of the window of the window comparator 3 when the information A input to the terminal 1 is a high voltage, that is, the truth value is "1", and outputs an AC signal B having a peak value higher than the level of the window of the window comparator 3. When the truth value is "0", the circuit outputs an AC signal with a peak value of the level within the window, and in this example, the information A is output to the power terminal of an oscillator whose power input is a DC input signal by C-MOS. input. That is, in this example, the signal conversion circuit 2 includes two inverters 20 and 21, two resistors 22 and 23,
The inverter 21 is provided with a capacitor 24, and information A is input to the positive terminal of the inverter 21 as a power supply voltage.

In this signal conversion circuit 2, the oscillation frequency of the output signal is determined by the time constant of the resistor 22 and the capacitor 24, and the peak value (amplitude) changes depending on the power supply voltage, that is, the level of information A. Therefore, if the information A is a signal with truth values "0", "1", and "0" as shown in FIG. 2A, this signal conversion circuit 2 converts
As shown in , the peak value of the AC signal corresponding to the truth value "0" is within the voltage levels e ₁ and e ₂ of the window of the window comparator 3, but the peak value of the AC signal corresponding to the truth value "1" is It becomes higher than the window voltage level e ₁ , e ₂ . Further, the output of the signal conversion circuit 2 becomes a voltage below the window of the window comparator when the input information A is zero voltage or the signal conversion circuit 2 is out of order.

In this example, the window comparator 3 includes an oscillation circuit 25 using three transistors 31, 32, and 33, and rectifies and smoothes the pulse width of the output signal from this oscillation circuit 25, and generates a high level voltage when the pulse width is large. and a rectifying and smoothing circuit 26 that generates a low level voltage when the pulse width is small. Resistors 34, 35 of the oscillation circuit 25,
37, 40, 41 are transistors 31, 32,
33, and the battery 30 is a power source for the transistor 32. The base of each transistor is directly connected to the output of the previous transistor. That is, the output of the transistor 33 is supplied to the base of the transistor 31 via a resistor 36 with a division ratio of collector resistors 34 and 35, and the output of the transistor 31 is supplied to the base of the transistor 32 via the power supply 30 through resistors 38 and 39. The output of the transistor 32 is divided by resistors 40 and 41 and supplied to the base of the transistor 33.
When a specific input voltage is applied to the input terminal 27, the oscillation circuit 25 switches from the transistor 31 to the transistor 3.
A feedback oscillator is configured to which the output of each transistor is supplied in the order of 2→transistor 33→transistor 31.

The input voltage range in which this oscillation circuit 25 can oscillate is the voltage of the power supply 30 _{as V0} , the resistors 34, 35, 37,
The resistance values of 38 and 39 are respectively R ₃₄ , R ₃₅ , R ₃₆ , R ₃₇ ,
R ₃₈ , R ₃₉ , when the voltage level of the input signal is V ₁ , the feedback voltage is V ₂ , and the lower limit of the input voltage V ₁ during oscillation is e ₁ and the upper limit is e ₂ , approximately e ₁・R ₃₉ /(R ₃₇ +R ₃₈ +R ₃₉ )≒V ₀ ......(1) e ₂・R ₃₅ /(R ₃₄ +R ₃₅ )≒ ......(2) It is given by: Here, the space between e ₁ and e ₂ becomes the window of the window comparator.

When the input voltage V ₁ is lower than the lower limit e ₁ , transistors 32 and 33 are on and transistor 31 is turned on.
remains off, so it does not oscillate. input voltage
When V ₁ becomes larger than the lower limit e ₁ , transistor 3
Since transistors 2 and 33 are turned off, transistor 3
1 is turned on. When transistor 31 is turned on, transistors 32 and 33 are turned off, and transistor 31 is turned off. When the transistor 31 is turned off, the transistors 32 and 3
3 is turned on, the window comparator will continue to oscillate from then on. Furthermore, when the input voltage V ₁ exceeds the upper limit e ₂ , the transistor 3
Even if transistor 3 is turned on, transistor 31 is not turned off, so the oscillation circuit becomes unable to oscillate.

As is clear from conditional expressions (1) and (2), the lower limit e ₁ and upper limit e ₂ of the input voltage V ₁ at which the window comparator oscillates are the resistors 34, 35, 37, 3
The oscillation start voltage can be freely set by appropriately selecting these resistance values.

In this NOT circuit, when the information shown in FIG. 2A, in which the truth value "0" is a low level and the truth value "1" is a high level, is input to the signal conversion circuit 2, the signal conversion circuit 2 is activated as described above. Since the AC signal shown in FIG. 2B is output, the window comparator 3 adjusts the voltage V ₁ of the AC signal B to the levels e ₁ and e ₂ in FIG. 2B.
Since the signal oscillates only between 1 and 2, the oscillation circuit 25 outputs the signal shown in FIG. 2C. In this case, as is clear from FIG. 2, the pulse width of the output signal C of the oscillation circuit 25 is almost the same as the input signal when the truth value is "0", but when the truth value is "1", the pulse width is approximately the same as the input signal. The width is narrow only at the rise and fall of the signal,
Therefore, the output signal D averaged by the rectifying and smoothing circuit 26 is at a high level when the input information A has a truth value of "0" and is at a low level when the truth value is "1", as shown in FIG. 2D. .

That is, in this NOT circuit, when the information A is at a low level, the output signal D is at a high level, and when the information A is at a high level, the output signal D is at a low level.
In addition, if the oscillation circuit 25 fails, or if the signal conversion circuit 2 fails and the input voltage V ₁ of the window comparator becomes zero, the oscillation circuit 25
does not oscillate, the output signal D of the rectifying and smoothing circuit 26 drops to near zero level as shown by the broken line in FIG. become.

If the above-mentioned NOT circuit is used in a circuit that processes a sensor output signal in an open circuit manner, a failure in the circuit can be quickly detected.

In other words, the output of the sensor is the change in voltage V △V
It is generally detected as . for example,
The output of the loop sensor is the change in inductance △L
is extracted as a voltage change ΔV. In this case, if the detection level Vth (threshold level) is set as shown in Figure 3A, the output information by closed circuit type processing will be As shown in Figure B, the output voltage Vnc becomes a detection signal on the disappearing side. In addition, the output information by the open circuit type processing is as shown in FIG.
On the other hand, this is the detection signal on the side where the output voltage Vno is generated. On the other hand, a fail-safe sensor is designed in such a way that the voltage V in Figure 3A becomes zero if the sensor fails, so if the sensor fails, the output information of the closed circuit type will change even if there is a detection signal. The output signal of the open circuit type has an asymmetric error characteristic on the side where there is no detection signal. Therefore, in the open circuit type, failure of the sensor can be determined only when there is a change ΔV and no detection signal is generated, and cannot be determined at other times. However, now, with the output of the sensor shown in FIG. 3A, the windows e ₁ and e ₂ of the window comparator are
If the setting is made and the signal shown in FIG. 3 A is applied to terminal 1 shown in FIG. 1, the output of the rectifying and smoothing circuit 26 will change △
V produces an output corresponding to the detection signal Vno shown in FIG. 3C. In this case, if the sensor fails, the output of the rectifying and smoothing circuit 26 will become zero, making it possible to immediately determine the failure.

Note that when the information A is the output of a circuit that outputs the signal shown in FIG. 2B, such as a pulse-driven photo sensor for detecting an object, the signal conversion circuit 2 is not necessary. Furthermore, when the processing circuit next to the NOT circuit is a circuit that processes truth values "0" and "1" with a pulse width, a rectifying and smoothing circuit is not necessary.
Furthermore, in FIG. 2, the negative output of the truth value "1" may be only a signal corresponding to the rising edge of the alternating current signal or a signal corresponding to the falling edge of the alternating current signal.

As described above with reference to the embodiments, according to the present invention, the oscillation conditions of the window comparator oscillation circuit can be changed by using the signal conversion circuit that can oscillate with binary truth values of low level and high level. , create an AC signal within the window of the oscillation circuit when the truth value is at a low level, and create an AC signal higher than the upper limit voltage level of the window of the oscillation circuit when the truth value is at a high level; The oscillation circuit is caused to oscillate based on the AC signal from the signal conversion circuit, and when the pulse width of the AC signal from the oscillation circuit corresponding to the low-level truth value is large, the high level is generated through the rectification and smoothing circuit of the window comparator. On the other hand, the DC output of
Since it is configured to obtain a low level DC output when the pulse width of the AC signal from the oscillation circuit corresponding to the high level truth value is small, the truth value is lower than the lower limit voltage level of the window of the oscillation circuit of the window comparator. If the value is a failure signal, a negative logical relationship is established between this truth value and the above-mentioned low-level truth value, and between the same truth value and the above-mentioned high-level truth value.

In addition, if the oscillation circuit of the window comparator breaks down or the signal conversion circuit breaks down and the input voltage to the oscillation circuit becomes zero, the oscillation circuit will not oscillate and the output level from the rectifier and smoothing circuit will be at a high level. Since the DC output is lower than the low-level DC output corresponding to the truth value of This will be extremely useful in the field of railway signals, where fail-safe safety is desired.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the NOT circuit according to the present invention, FIG. 2 is a diagram explaining the operation, and FIG. 3 is a diagram explaining the operation and effect. A: truth value information, 2: signal conversion circuit, 3: window comparator, 25: oscillation circuit, 26: rectification and smoothing circuit.

Claims (1)

[Claims] 1. An oscillation circuit 25 that oscillates and outputs an alternating current signal when the input voltage is within the window between the lower limit voltage level e1 and the upper limit voltage level e2, and that has the characteristic of not producing an output due to its own failure, and the oscillation circuit 25. circuit 25
A window comparator 3 consisting of a rectifying and smoothing circuit 26 that rectifies and smoothes an alternating current signal from the window comparator 3;
It oscillates with two truth values of low level and high level, and when the truth value is low level, the AC signal within the window of the oscillation circuit 25 is generated, and when the truth value is high level, the oscillation circuit 25 and a signal conversion circuit 2 that outputs an AC signal higher than the upper limit voltage level e2 of the window to the oscillation circuit 25, and causes the oscillation circuit 25 to oscillate based on the AC signal from the signal conversion circuit 2. Therefore, when the pulse width of the AC signal from the oscillation circuit 25 corresponding to a low-level truth value is large, a high-level DC output is transmitted through the rectifying and smoothing circuit 26, and on the other hand, the same pulse width corresponding to a high-level truth value is output. A negative circuit characterized in that it is configured to obtain a low level DC output when the pulse width of the AC signal from the oscillation circuit 25 is small.