JPS6321870B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a disconnection detection circuit in a digital output circuit of a remote monitoring control device or the like. Generally, power output elements such as a contact relay, a power transistor with photocoupler insulation, a power transistor with transformer insulation, and a triac are used in the power output section of a digital output circuit. Conventionally, in order to check the operation of the power output element of these power output sections, if it is a relay, one contact of a multi-contact type relay is used, and the output from that contact is directly sent to the digital input circuit. The output signal was once received by a relay, and the output from the contact was used in the same way as above. However, in either case, one extra contact is added to check the operation of the power output element, or
This posed problems both economically and in terms of physical space because it required external relays and the same number of digital input circuits as outputs. The above is a method of checking by directly reading back the output signal, but as a method of checking without directly reading back the output signal, there is a method shown in FIG. 1. This is to read back the signal of the register that stores the output data and compare it with the data written to the register. In Figure 1, D ₀ - D ₃ are data buses, WP is a write signal line, RP is a read signal line, RG is a register, L ₀ - _{L 3} are register output lines, DR ₀ - _{DR 3} are drivers, and RY ₀ - RY ₃ is a power output element consisting of a relay, C ₀ to C ₃ are its contacts, G ₀ to _{G 3} are its gates,
Further, SK ₀ to SK ₃ are spark killers, and E is a power source. Data on data buses D ₀ -D ₃ are read into register RG by a write signal. register
Output lines L ₀ to _{L 3} of RG are connected to one input of gates G ₀ to G ₃ , respectively, and the other inputs of gates G ₀ to _{G 3} are commonly connected to read signal line RP. Therefore, by giving a read signal, the data written to register RG is transferred to data bus D ₀ ~
Can be read out on _D3 . Therefore, the data written to register RG and the gates G ₀ to _{G 3}
The operation of the register RG can be checked by comparing and collating the data read from the register RG via the register RG. However, this method merely checks the quality of the register and cannot confirm the operation of the power output element. By the way, when a relay is used as a power output element, the relay coil is more susceptible to the effects of on/off frequency and heat, and is more susceptible to disconnection than other parts or elements used in this type of output circuit. The probability of failure is high, and this is the same in the case of transformer insulation.On the other hand, in the case of insulation using photocouplers, there are problems such as a high probability of failure due to external noise. It has been desired to realize a method for checking the operation of an output element. Therefore, it is an object of the present invention to eliminate the above-mentioned drawbacks and to reliably detect disconnection of a power output element of a digital output circuit using a simple circuit and inexpensive and easily available parts. It is something to do. According to the present invention, the above object is to provide a register that stores digital data for driving a power output element, and a register that is provided corresponding to the output line of this register and that is turned on or off in accordance with the digital output from the register. For a digital output circuit formed by cascading a driver and a power output element provided corresponding to the driver and driven by the driver, the digital output circuit includes a resistor connected in parallel to each of the power output elements, and a power This can be achieved by providing a resistive voltage divider circuit connected in parallel to the drive power source of the output element so that disconnection of the power output element can be detected. Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing an embodiment of the digital output circuit according to the present invention. Compared to the conventional example shown in Fig. 1, the OR circuit RO,
Inverter INV ₀ ~ INV ₃ and resistor R ₃₀ ~ _{R 33} ,
The difference is that _R40 to _R43 , _R50 to _R53 , and _R70 to _R73 are provided. Here, R ₃₀ to R ₃₃ are connected to P ₀ to R 33 such that when the drivers DR ₀ to _{DR 3} are on, the inputs of the inverters INV ₀ to INV ₃ are at a high potential (hereinafter referred to as high level or H). P This is a resistor provided to increase the potential at _{the three} points. R ₇₀ to R ₇₃ are resistors connected in parallel with relays RY ₀ to RY ₃ , but the resistance value of this parallel circuit is almost the same value as when relays RY ₀ to RY ₃ are installed alone. In other words, each resistance value of R ₇₀ to R ₇₃ is R, and each resistance value of relays RY ₀ to _{RY 3} is
If RY, then R≫RY is set. When the relay coil is disconnected, the resistance value of the parallel circuit increases, and the input sides of the inverters INV ₀ to INV ₃ are set at low potential (hereinafter referred to as low level or L) at points P ₀ to _{P 3} . It is used to determine the potential. Further, R ₄₀ to R ₄₃ and R ₅₀ to _{R 53} are resistors for dividing the potential at _three points P ₀ to P to set the input potential of the inverters INV ₀ to INV ₃ to H or L. These resistors are relays RY ₀ to RY ₃ and resistor R ₇₀
~ When connected in series to the parallel circuit with R ₇₃ and relays RY ₀ ~ RY ₃ are not disconnected, P ₀
~P The potential at _three points is high, so the inverter
The input points of INV ₀ to INV ₃ are set to H, and the relay RY ₀
This is to lower the potential at the _three points P ₀ to P to become L when ~RY ₃ is disconnected. In addition, these resistances R ₄₀ to R ₄₃ and R ₅₀ to R ₅₃ are
Resistance by turning on and off drivers DR ₀ to DR ₃
The potential at the _three points P ₀ to P will fluctuate depending on whether they are connected in parallel with R ₃₀ to R ₃₃ or not.
In any case, the input potentials of the inverters INV ₀ to INV ₃ are appropriately selected so as not to exceed a specified level. The operation will be explained. (b) First, if one of drivers DR ₀ to DR ₃ is on (off), the corresponding relay
When RY ₀ to _{RY 3} are disconnected. In this case, the potential at any of the _three points P ₀ to P becomes extremely low compared to before the relay was disconnected.
The output of any of the inverters INV ₀ to INV ₃ is H.
Therefore, the AND circuit is activated by the read signal RP.
AND opens and an error notification is issued. In this case, the potential at _three points P ₀ to P is the driver
Since it does not change depending on whether DR ₀ to _{DR 3} are turned on or off, a relay disconnection accident can be detected regardless of whether the driver is turned on or off. This means that even if the driver malfunctions while the relay is disconnected, the disconnection of the relay can be reliably detected. (b) Next, if any of drivers DR ₀ to DR ₃ is on (off), the corresponding relay
When RY ₀ to RY ₃ are not disconnected. In this case, the potential at points P ₀ to P ₃ is at a high level, regardless of whether drivers DR ₀ to _{DR 3} are on or off, unless there is a disconnection in the relay.
The output sides of the inverters INV ₀ to INV ₃ do not become H, so even if the read signal RP is applied, the AND circuit AND is not established and no abnormality notification is performed. The above operations are summarized and shown in Table 1 below.

[Table] In Table 1, the status of each part is L, DR and
RY indicates the status of each part, such as the output line of the register, the driver, the relay coil, or a disconnection of the line, and the signal status INV indicates the output status of the inverter. Further, a logic 0 indicates a low level L, and a logic 1 indicates a high level H, and a signal state of H indicates that there is a disconnection in the relay coil or line. In Fig. 2, inverters INV ₀ to INV ₃ are used to detect the potentials at the _three points P ₀ to P, but any device may be used as long as it can reliably detect the potential level. Furthermore, if the outputs of the inverters are read out independently for each point without being combined using an OR circuit, it becomes possible to check each relay. In addition, we have explained that the power output element of the digital output circuit is composed of a relay.
The same applies to transformer-insulated types and those using photocouplers. As described above, according to the present invention, it is possible to easily and reliably detect the driver using inexpensive and easily available parts or elements, regardless of whether the driver is on or off or malfunctioning, so it has great practical effects. It is.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional example of a digital output circuit, and FIG. 2 is a diagram showing an embodiment of the digital output circuit according to the present invention. Symbol explanation, D ₀ ~ D ₃ ... Data bus, RG ... Register, DR ₀ - _{DR 3} ... Driver, RY ₀ - RY ₃
...Power output element consisting of a relay, INV ₀ ~
INV ₃ ...Inverter, OR...OR circuit, AND
...AND circuit, R ₃₀ ~ R ₃₃ , R ₄₀ ~ R ₄₃ , R ₅₀ ~
_R53 , _R70 to _R73 ...Resistance.

Claims (1)

[Claims] 1. A register that stores digital data for driving a power output element, a driver that is provided corresponding to the output line of the register and turns on or off according to the digital output from the register, and a driver that corresponds to the driver. A digital output circuit is configured by cascadingly connecting power output elements provided at the same time and driven by a driver. 1. A disconnection detection circuit for a digital output circuit, comprising a resistive voltage divider circuit and detecting disconnection of a power output element based on voltage dividing point potential.