JPS6028962Y2 - control circuit - Google Patents

Description

[Detailed description of the invention] The present invention constructs a jump amplification circuit by providing a positive feedback circuit and a first-order lag negative feedback circuit in a DC amplifier, and calculates proportional characteristics based on the output of the jump amplification circuit. The present invention relates to a control circuit capable of correcting steady-state deviation by changing the output characteristics of the control circuit in a control circuit using a time-proportional operation circuit in which the control point is set within the proportional band.

Conventional control circuits using time-proportional operation circuits include a DC amplifier with a positive feedback circuit and a negative feedback circuit with a first-order lag to form a jump amplifier, and use the output to control transistors, etc., for example. It drives the control relay.

FIG. 1 shows a circuit diagram of an embodiment of a control circuit using such a time proportional operation circuit.

In the figure, DC amplifier A is provided with a positive feedback circuit consisting of resistors R4 and R5, a negative feedback circuit consisting of resistors R1, R2, R3, and capacitor C, and further receives a detection signal from the controlled object and a target value as inputs. The input voltage Vin based on
The output of the transistor Tr is controlled via a resistor to drive the control relay Ry.

Then, the steady-state deviation caused by the control result is determined by variable resistor VR1.
We are trying to fix it.

Consider a case where the conventional control circuit shown in FIG. 1 does not have a power supply circuit for correcting the steady-state deviation.

In that case, the output characteristic curve of the power supply circuit, that is, the transistor T
The time ratio in which the control relay Ry operates under the control of r is generally expressed by the following equation by setting each resistance value in the relationship of resistance R<R6, R<R2.

That is, V-VR zn(t+-L-!"・") TON EP +Vi
n R5ξ1=ToN+ToFFtn(l+,-)+
tn(1+VP-■NVP-VN R4 EP+vln R5EN-■1n RJ°---(1) 5.

However, Vp, VN: Vp is the saturated output voltage of DC amplifier A
■, the relationship, E, = (''-1)■2 R2+R3R5 E・=calyx-left)■・R5R2+R3 The output characteristic curve ξ1 shown in equation (1) has the input voltage Vin on the horizontal axis and the output on the vertical axis. It is indicated by ξ1 in the graph shown in FIG. 2 in which the characteristics are scaled.

That is, in equation (1), when Vin=-Ep, the output characteristic ξ□=1.0, as the input voltage Vin increases, the output characteristic curve ξ1 decreases, and when Vin=[''>,
ξ1=0.5, furthermore, when Vm=EN, ξ1=0
becomes.

However, in such a control circuit, the input voltage Vin
(-E in Figure 2)
The width of the interval from p to EN) can be changed by changing the values of the circuit constants, but the width of the center point of the proportional band (Vin=
! At the point ), the output characteristic curve ξ□ cannot take a value other than 0.5.

Therefore, when a control point is provided at the center point of the proportional band, good control results cannot be obtained in a controlled object where the output amount varies at the control point.

For example, consider the case of temperature control by heater control based on FIG.

Figure 3 shows the temperature on the horizontal axis and the output characteristic ξ on the vertical axis.The output characteristic curve as shown in Figure 2 is plotted near the control point where the temperature is set (proportional band in the figure). A proportional action is performed.

In addition, in the figure, Wl, W2. W3 is the saturation temperature curve for each heater with a heater capacity of Wl9, W29, and w3. For example, when using a heater capacity of W□, the temperature rises above O, and the temperature is controlled to the control point shown in the figure. Since the output characteristic is good at the P□ point, that is, 0.5, it can be controlled by an output characteristic curve such as ξ1 shown in FIG.

However, when the heater capacity becomes W2 or W3, if you try to perform control using the output characteristic curve ξ1, the control will be performed at points P'1 and P'', respectively, and the control point will be This results in steady deviations of −ΔX and 10Δy, respectively.

In the conventional control circuit, in order to eliminate this steady-state deviation, the power supply EB is connected in parallel with the input voltage Vin as shown in Fig. 1.
1. A power supply section consisting of a variable resistor VR□ and a resistor R7 is provided,
It is configured to correct the steady-state deviation caused by the control result by moving the input voltage to the DC amplifier A in parallel using the variable resistor VR1.

However, in this case, a separate power supply section is required, and stability of the power supply is required, and control at the edge of the output characteristic due to the degree of parallel movement poses a problem in controllability close to on/off operation.

It is an object of the present invention to provide a control circuit that can eliminate the drawbacks of the conventional control circuit and at the same time correct the steady-state deviation.

According to the present invention, this purpose is distantly related as follows.

That is, two series circuits consisting of a resistor and a diode are connected in parallel so that the diodes have opposite polarities, and the parallel circuit is inserted between a DC amplifier and a negative feedback circuit.
Moreover, each resistance in the two series circuits is configured by a resistance between one terminal of the variable resistor and the variable tap, and a resistance between the other terminal of the variable resistor and the variable tap. By changing the position of the variable tap of the resistor, the charging/discharging time constant of the capacitor in the negative feedback circuit is changed, so that the output characteristics can be changed and the steady-state deviation can be corrected without using another power source.

Next, the present invention will be explained in detail based on the embodiment shown in the drawings.

FIG. 4 shows a circuit diagram of an embodiment of a control circuit according to the present invention.

In the figure, a conventional negative feedback circuit consisting of resistors R1, R2, R3° and a capacitor C has diodes D1. D2 variable resistance V
It is connected to the output terminal of the DC amplifier via R2.

The other configurations are the same as in FIG. 1.

That is, in the embodiment shown in the figure, the resistance of the two circuits for charging and discharging is obtained from the variable tap of the variable resistor VR2 connected to the negative feedback circuit, so that the charging and discharging of the capacitor C in the negative feedback circuit is controlled. This allows the time constants to be changed in relation to each other.

If the resistance value between both terminals of the variable resistor VR2 is R, and the resistance value between the terminal connected to the diode D1 and the variable tap is expressed as X, then the output characteristic according to the present invention is the resistance value X.
The value changes as follows.

That is, the output characteristic ξ is in the same form as equation (1), and is expressed as ■P-VN
R4 TPtn(1+ ・-) EptV, n R5 VP-VN R4V, -V, R4°-------<
2) TPtn(1+ ・-)+Tt(1+
・-)EP+■1nR5nnEN-vinR5.

Further, depending on the value of the resistance value X, the time constant of charging and discharging is as follows.

When X = 7, charging time constant = discharging time constant Depending on the value of constant resistance value
) The values of TP, TN, and Ept EN in the equation are as follows.

1 When X=7, R2 (R3+-→ Tp='l'N=□・C R2+ Cfl 3 +-) EP=(R"1"R2+R3+!3-ru" (4) EN knee (RIR4 R2+R3+dan- "°" When X>dan, x<dan 2 'rp= R2 (R3+X) R2+Island+X)°C TN=R2(R3+R-X), c R2(R3+R-X) 1R4 E・=(2゜+ (Ra+ When Vin='-'\, the output characteristic ξ=0.5, resulting in a curve similar to ξ1 shown in FIG.

Of course, when Vin=-EP, ξ=1. o, Vin=EN
When ξ=0.

Consider the case when X>H, that is, when the charging time constant is made larger than the discharging time constant, and the case when X>H, that is, when the charging time constant is made smaller than the discharging time constant.

In equation (2), EN EP TP If Vin-□, then ξ=.

2 T2+TN Comparing the sizes of TP and TN shown in equation (3), the following equation is obtained.

That is, TP-TN= R2''<2X-R) (R2+ R3+ XXR2+ R3+ R-X)
"""(6')

In equation (6), everything other than (2X-R) is positive, so (2
The positive or negative value of TP-TN is determined by the value of X-R).

Therefore, when X>day, TP TN>0, so V
When in=n■, ξ>0.5.

Also, when X<%, TP-TN<0, so Vin
When ='-''≧, ξ<0.5.

Therefore, if the output characteristic ξ when 2X>- is denoted by ξ3 and the output characteristic ξ when X<'' is denoted by ξ2, the output characteristic curve ξ2.
ξ3 is drawn as a curve in the area as indicated by B and C in FIG.

However, in Fig. 2, the value of -EP?EN when X''%, X>%-X<%, is the value determined by equations (4) and (5), so naturally they are different values, but the In Figure 2, the graph is simply drawn as -EP and EN which are common.

As described above, according to the present invention, it is possible to obtain a predetermined curve as shown in FIG. 2 by changing the resistance value X using the variable tap of the variable resistor VR2.

In FIG. 2, the output characteristic curve ξ2. ξ3 changes depending on the value of X.

When the present invention is applied to the case of temperature control using the heater control described above, in addition to the output characteristic curve ξ1, for example, an output characteristic curve indicated by ξ2 or ξ3 can be obtained as shown in FIG.

Therefore, the heater capacity is W2. For a heater like W3, the output characteristic curve ξ2. By obtaining the output characteristics as shown in ξ3, it is possible to control the heater at 42 points or 13 points at the control point, and it is possible to control the temperature at the control point without steady deviation, making it possible to use other power sources. It is possible to correct the steady state error without using

In the embodiment of the present invention, the variable tap is connected to the negative feedback circuit, but it goes without saying that the variable tap may be connected to the output terminal of a DC amplifier, and the resistance of one circuit may be a fixed resistance. Figure 4 shows that it is possible to correct the steady-state deviation by making only one of the charging and discharging time constants variable by making the resistance of the other circuit variable. This can be easily understood from the description of the embodiments of the present invention.

However, if we compare the case where only one of the charging and discharging time constants is variable and the case where the charging and discharging time constants are variable in relation to each other as shown in Figure 4, we find that the charging and discharging time constants are variable relative to each other. A related variable is better for obtaining good control results, as the width of the proportional band does not change much compared to equation (5), and a large steady-state error correction effect can be obtained by slightly changing the resistance value. Are suitable.

[Brief Description of the Drawings] Figure 1 is a conventional control circuit, Figure 2 is the output characteristic curve of the present invention and the conventional control circuit, and Figure 3 is the principle of temperature control using the present invention and the conventional control circuit. 4 shows a circuit diagram of a control circuit according to the present invention. A...DC amplifier, VRl, VR2...
・Variable resistor, R1-R7...Resistance, C...
...Capacitor, Tr...Transistor, V
in...Input voltage, EB...Power supply, R
y...Control relay, Dl, D2...Diode.

Claims (1)

[Scope of utility model registration request] A DC amplifier is provided with a positive feedback circuit and a negative feedback circuit with a first-order lag to form a jump amplifier circuit, and a control point that controls an operating terminal having a proportional characteristic based on the output of the jump amplifier circuit. In a time proportional operation circuit set within the proportional band, two series circuits consisting of a resistor and a diode are connected in parallel so that the diodes have opposite polarities, and the parallel circuit is connected to the DC amplifier and the negative polarity. the resistance between one terminal of the variable resistor and the variable tap, and the resistance between the other terminal of the variable resistor and the variable tap. A control circuit characterized by being constructed using a resistor.