JPS61101803A - Current addition circuit - Google Patents

Abstract

PURPOSE:To keep excellent performance even with detect of one series of controller by providing multiple amplifiers and current converters relating to a multiplex controller, providing a feedback resistor for amplifier output to each current converter and feeding back a load signal. CONSTITUTION:The 1st operating circuits 7(7A,7B,7C) operate a deviation signal between a real load signal and a load drive signal from multiple controllers 1(1A,1B,1C), give a correction signal thereto for output. The output is amplified by amplifiers 8(8A,8B,8C) and converted into a current signal by the current converters 3(3A,3B,3C) having feedback resistors 5(5A,5B,5C). Further intermediate selection circuits 9(9A,9jB,j9C) inputting the output of the amplifiers 8 and selecting an intermediate value are provided and operate the deviation between the amplifiers 8 and the circuits 9 respectively, and each deviation signal is outputted from the 2nd operation circuits 10(10A,10B,10C) as the correction signal to the circuit 7. Then one terminal of the load 4 is connected to the output of the converter 3 and the other terminal of the load is connected to the feedback resistors 5 of the converters 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a current adder circuit that drives a load with an intermediate value of multiplexed control device outputs.

[Technical Background of the Invention] In recent years, control devices used to control processes that require high reliability are often multiplexed for the purpose of improving the reliability of the control devices themselves. Multiplexed configuration includes common equipment and standby 4! & equipment, and use a standby device in the event of a failure of the regular equipment, or a method where multiple control devices are operated at all times and control is performed by selecting the most likely representative value from the outputs of those control devices. It is being In general, the former method requires a failure detection circuit to detect equipment failure, and switching from the regular equipment to the standby equipment is performed when a failure is detected by the failure detection circuit. High fault detection ability is required. However, it is impossible to detect all failures, and the higher the failure detection ability, the more complex the failure detection circuit becomes, and failures of the failure detection circuit itself become a problem.

On the other hand, the latter method requires at least three control devices to select the most likely representative value, and also requires a selection circuit to select the representative value. If the device is triplexed, an intermediate value selection circuit is usually used as the selection circuit. In this case, the intermediate value selection circuit selects the intermediate value of the outputs of the three control devices as a representative value and drives the load to be controlled, so even if one control device fails, control will continue normally. becomes possible. However, even with this method, since there is only one intermediate value selection circuit, if the intermediate value selection circuit fails, normal control can no longer be performed. In other words, no matter how many control devices are multiplexed,
The reliability of the selection circuit that selects the most likely representative value from among the outputs of each control device and narrows it down to one becomes a problem. For this reason, it is necessary to increase reliability by simplifying the selection circuit as much as possible and reducing the number of components, and a selection circuit commonly used for this purpose is a current addition circuit.

FIG. 3 is a diagram showing a configuration example of a conventional current adding circuit. The outputs S1 of the three control devices 1 (subscripts A, B, and C are added in the figure to distinguish them, and the same applies to the others) are input to the isolation amplifier 2, and the output S2 of the isolation amplifier 2 is converted into a current output S by the current converter 3, and each current output S, A, 33B, S1c is connected to one end of the load 4. The other end of the load 4 is connected to a feedback resistor 5 common to each current converter 3, and a terminal voltage S of the feedback resistor 5 is fed back to the current converter 3. Although the isolation amplifier 2 is not necessarily required, it is usually provided to electrically isolate the control device side and the load side and to operate the control device 1 stably against external noise and the like.

Next, a conventional configuration example shown in FIG. 3 will be explained. The operation of the isolation amplifier 2 and current converter 3 is expressed by the following equations (1) and (2).
) is shown by the formula.

52=s, (1
) Sa = Ka (5255) ・・
(2) Note that in the above equation (2), the symbol represents the gain of the current converter 3. Next, the current supplied to load 4 is 5
4, the following equation (3) is obtained.

54=S, A+S, B+S3C・-----C3) Furthermore, the terminal voltage S5 of the feedback resistor 5 is expressed by the following equation (4) when the feedback resistance value is Rf.

S, = RfS4...
...(4) 1. From equations (1) to (4), each control device output S, A, and S, the relationship between S, (and load current S4 is as shown in equation (5) below.

[Problems with the background art] However, in general, the characteristics of the current converter 3 are 1J characteristics as shown in Fig. 2, and the possible range of the current converter output S is 0 to 100 (%). In this case, (2) above
The linear range in which the formula holds is 100 for S, -S, and odor.
It's only (%) in /. Therefore, in order for the above equation (2) to hold true, it is necessary that the following hold true. If Is, -3,l deviates from the range of equation (6) below, 1 becomes very small as shown in FIG. When the conditions under which the above equation (6) holds are calculated using the above equations (2), (3), and (5), at least two of the following equations need to hold. Therefore, for example, if the control device 1c fails and the control device output S10 deviates from the range of equation (7) above, cζO will be obtained as described above.

Therefore, from equation (5) above.

, K AS A + K as a...
...(8) S4: Rf (K3A 10 3B) Then, the fluctuation rate for S4 (54-3,')/S is obtained from the above equations (5), (7), and (8), (S, -54' )/S, <”X 100/to 3 (%)
...(9). Generally, the gain of the current converter 3 is large, and if we assume that = 100, the load current S4 will only change by 0.3 (%) or less no matter how the control device output S1c malfunctions.
This means that sufficient choices have been made. It is also clear that the larger the value of , the better, in order to make a more complete selection.

However, as described above, the linear range of the current converter 3 becomes narrower as S3 is increased, and the total control device output S
Even in a normal state where 0 is the normal state, the outputs S3 of the two current converters 3 will become saturated due to slight variations in the outputs of each control device.

Now, a case will be described based on FIG. 5, assuming that the control device output 31B fails while the current converters 3A and 3c are saturated. If S and El fail in the decreasing direction at time t1 in FIG. 5, the current converter output 81B goes in the negative saturation direction, and naturally the load current S4 also decreases. As a result, S,
c S, , decreases, and the current converter output S, c, which had hitherto been negatively saturated, recovers, and finally l S1c -55
When 1<100/, (%) satisfies the Sarrell range, the load current S4 settles. However, since the current converter 3 generally has poor responsiveness in the saturation region compared to the linear region, there is a non-negligible time delay (△t in the figure) before the current converter 3 recovers to the linear state.
), and the current converter output S3C does not recover instantly. Therefore, the load current S4 remains fluctuating within Δ. For this reason, even a failure in one system of the control device I\I will cause the load current to fluctuate temporarily, causing the load current to fluctuate temporarily.In order to avoid this problem, the current exchanger gain K must be adjusted.

All current converters 3 may be set to a linear state within the normal variation range between the control device outputs S1. However, if 3 is made smaller, the above (7)
The selection characteristics will deteriorate due to the equation. Therefore, in the prior art, there are conflicting demands to reduce transient fluctuations in load current at the time of failure in the l series of control table vil and to improve steady-state selection characteristics, and it is necessary to satisfy both. I can't.

Furthermore, since the feedback resistor 5 is single-layered, and a failure of the feedback resistor causes a failure of the whole, the reliability of the whole is determined by the reliability of this feedback resistor, and the reliability of the whole is greater than the reliability of the feedback resistor. There were problems such as the inability to raise the

, invention, ), target] ゛' The present invention solves the problems of the prior art described above, achieves both reduction of load current fluctuation when one control device series fails and sufficient selection characteristics, and provides highly reliable current addition. The purpose is to provide circuits.

[Summary of the Invention] To this end, the present invention provides multiplexed amplifiers and current converters corresponding to the multiplexed control device, and each amplifier has a respective A signal obtained by adding the deviation between the amplifier output and the intermediate value of each amplifier output is input, while each multiplexed current converter is provided with a feedback resistor for each amplifier output and the load signal is fed back. It is characterized by what it did.

[Embodiment of the Invention] FIG. 1 shows the configuration of a current adding circuit according to an embodiment of the present invention. In FIG. 1, the same reference numerals as in FIG. 3 indicate the same or equivalent parts. The difference from Fig. 3 is that the first isolation amplifier 2
A first arithmetic circuit 7 is provided between the controller 1 and the controller 1 to calculate the deviation between the controller output S and the actual load signal S obtained by insulating the load current S by the insulating amplifier 6. The output of the circuit 7 is passed through the amplifier 8 to the first isolation amplifier 2.
An intermediate value selection circuit 9 is provided which inputs the output point Sll of each amplifier 8 and selects an intermediate value thereof, and calculates the deviation between the intermediate value selection circuit output S and the amplifier output S6 by a second arithmetic circuit. 10 and the output of the second arithmetic circuit 10 is added to the first arithmetic circuit 7 as a correction signal, and the feedback resistor 5 is provided for each current converter and multiplexed.

In addition, C0M1. C0M2 and the like indicate independent power supply commons.

Now, assuming that the gain of the amplifier 8 is KIl, the output from the control device output S to the first isolation amplifier output S2 is expressed by the following formula.

Sll”K11(St S,,+m1d(S8A+S
++B+5sC) -5s)"' (10) S2=S,
---・-(11) Here, m1d (SIIA, S8a, S, c) is each signal Sg
Represents the intermediate value of A + S* B + S Q'. The process from the first insulated amplifier output S2 to the current converter output S3 is similar to equation (2). However, each current converter 3 has an individual feedback resistor 5, and one end of the feedback resistor 5 is connected to the mutually independent common C0M4. What is fed back to 3 is the terminal voltage of the feedback resistor corresponding to the current value output by the self. Therefore, S, = RfS, ・・
・(12) becomes. On the other hand, the actual load signal detected by the second isolation amplifier 6 corresponds to the load current and is expressed by the following equation.

56=lIQS, ・・
...(13) S, :S, AIS, B+S, C--(
14) Here, RQ is the resistance value of the load 4.

First, from equations (2) and (12), 5' −...(15)8
・=[t. Although this indicates the input/output characteristics of the current converter 3, it is not included in (15), so even if K is a large value, the output S3 will not be saturated and the human power S,
It is linear with respect to On the other hand, (10) and (1
1) From formula 1, for example, S, A=mid(S28, S, s,
52c) If so, S,, A: 8A (S, A-56)
...(16) S, B: 51B-3G +S, A,
=s, a+KsAsIA−KsAS6− (17) S,
c=s, c-5, +S, A:S, C+, ASlA-K
gASF, -(18). Therefore (13), (14
), (1, 6), (17) and (18), S1A
, SiB, S, The relationship between c and S4 is as shown below.

,=S AI as B+ S c ・
...(19) 1(Q Here.Then, we investigated the degree of influence when the output S1c of the control device IC becomes abnormal.
19) If the value of load current S4 is 84' when 5ic=o in equation 19), then (54-3,')/S, <-X100/kg (%)
It can be seen that (21) is obtained. Therefore, if 3 is set to a large value, sufficient selection can be made as in the conventional configuration example. In addition, (17) and (18) above
According to equation (19), if 3 is large, then Therefore, lS, B-51Al and l51C-
3. If AI is a variation of the normal control device output S, then S, Bξ52 CξS2A, and the outputs S of each current converter are approximately the same value. Also, for this reason, saturation naturally does not occur.

In this way, even if the gain of amplifier 8 is set to a large value of 8, saturation does not occur anywhere on the circuit, and the circuit is always in the linear region.
Moreover, the current converter outputs S4 are all balanced. For this purpose, 1, for example, the control device output S1. Even if ^ becomes abnormal, as shown in Figure 2.

It will be instantly corrected by other series. Moreover, for this reason, the value of can also be made larger than in the conventional configuration example, providing better selection characteristics than in the prior art. I can do two things.

As described in "Effects of the Invention" (2), according to the present invention, it is possible to achieve both reduction in load current fluctuation when one control device series fails and sufficient selection characteristics.

Since the Sarashiko feedback resistor is also triplexed, one (I
I! A failure of the JL'5 resistor does not cause a failure of the entire system, and reliability can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a current adding circuit according to an embodiment of the present invention, FIG. 2 is a signal diagram showing the operation of the current adding circuit of FIG. 1, and FIG. 3 is a diagram showing the configuration of a conventional current adding circuit. 4 is an input/output characteristic diagram showing the operation of the current converter shown in FIG. 3, and FIG. 5 is a signal diagram showing the operation of the current adding circuit shown in FIG. 3. DESCRIPTION OF SYMBOLS 1... Control device, 2... First isolation amplifier, 3...
・Current converter, 4...Load, 5...Feedback resistor, 6...
...Second isolation amplifier, 7...First arithmetic circuit, 8.
...Amplifier, 9...Intermediate value selection circuit, 10...Second
calculation circuit. -\, Figure 1, 56 Figure 2 Figure 3 ll 55 ツ5

Claims (1)

[Claims] a multiplexed first calculation circuit that calculates a deviation signal between the load drive signal and the actual load signal from each of the multiplexed control devices, adds a correction signal to the deviation signal, and outputs the resultant signal; multiplexed amplifiers that amplify the output of one arithmetic circuit; multiplexed current converters each having its own feedback resistance and converting the output of each amplifier into a current signal;
a multiplexed intermediate value selection circuit that simultaneously inputs the outputs of each of the amplifiers and selects an intermediate value among them; and calculates the deviation between the output of each of the amplifiers and the output of the intermediate value selection circuit; A multiplexed second arithmetic circuit outputs a deviation signal as the correction signal to the first arithmetic circuit, one end of the load is connected to the output of each of the current converters, and the other end of the load is connected to the output of each of the current converters. A current adding circuit characterized in that it is connected to a feedback resistor of a current converter.