JPS61221919A - Load current controller - Google Patents

Abstract

PURPOSE:To suppress both the overshoot and undershoot of a load current by flowing the current sent from a current impressing circuit to a capacitor for integration for charge and discharge when the set current value is changed. CONSTITUTION:The proportion, integration, addition and deviation detecting elements are obtained by operational amplifiers 11, 12, 13 and 14, respectively. Both an FET 2 and a control circuit 3 are actuated by the control signal which is applied only when the current set value is changed. Thus a current ic which is decided by the output proportional to the deviation between the set current value (i*) given via the amplifier 14 and the actual current value (i), a resistance R4, etc., is applied to an integration capacitor C. Thus the unnecessary charge and discharge is avoided. As a result, the output waveform of a current control ler ACR becomes gentle at and after a prescribed time point. Then the current value (i) has a satisfactory waveform which is free from the overshoot.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a load current control device, and particularly to a load current control device that can control overshoot or undershoot of a load current when changing its current setting as much as possible. L 91 +l
＋ jL 虌辷膳l餉え蜲 + 1 横平 ← Mm 'II 閱黛-一 啼 ko j-The control device that swings has extremely large inductance, such as a superconducting magnet coil, and there is almost no resistance. When controlling a load like f
! It is convenient to use rK.

[Conventional technology]

Fig. 3 is a schematic diagram showing an example of a general load power supply system, and Fig. 4 is a characteristic diagram showing the relationship among the current setting value, actual value, and current regulator output to explain the operation of Fig. 6. . In FIG. 5, 6 is a power converter, 7 is a load, 8 is a current detector, 9 is a power converter control device consisting of a current regulator (CR) 91, a firing angle regulator 92, and the like.

That is, the current regulator (A, CR) 91 consists of at least a proportional element (P element) and an integral element (I element),
A PI adjustment calculation is performed on the actual current value i obtained through the current detector 8 so that it becomes equal to the set value 1, and a predetermined operation output is output, and the firing angle regulator 92 performs power conversion based on this operation output. The ignition control is performed on the load 7, thereby causing a conflict between the load 7 and the load 7.
When changing the load current set value l, the integral element is not used and the deviation (ji) between the set value and the actual value i is
) is within a value, it is common to make use of the integral element. Note that this is done in order to eliminate offset errors.

Therefore, for example, if the temporal change in the current setting value is
If it is expressed as shown in figure (a), the output of the current regulator changes as shown in figure (b), and as a result, the current (actual value) flowing through the load becomes as shown in figure () and ).

[Problem that the invention seeks to solve]

In other words, when changing settings, it is desirable to take advantage of the integral characteristic when the deviation between the set value and the actual value is as small as possible. However, it is difficult to take advantage of the integral characteristic with optimal timing due to the drift of the arithmetic circuit that creates this deviation and the comparator circuit that detects this deviation. For this reason, the capacitor of the integral element is forced to perform extra charging and discharging, and when this charging and discharging is reset, the load current has an overshoot as shown in Figure 4 (c) K. This results in shoot SU. The effect of this is noticeable, for example, when controlling a load with a large inductance such as a superconducting magnet coil, and its large time constant and hysteresis characteristics make it impossible to control the desired current, resulting in a drop in performance. occurs.

[Means for solving problems]

A current application circuit that applies a predetermined current to the integral element only when the current setting value is changed, and a control circuit that similarly causes the integral element to perform an integral operation only when the current setting value is changed are provided.

[Effect]

When changing the current setting value, the current from the current applying circuit should be passed to the integrating capacitor for charging and discharging.
By eliminating excess charging and discharging, try to suppress undershoot as much as possible before shooting.

〔Example〕

Fig. 1 is a circuit diagram showing an embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
Current setting value to explain the operation in the figure.

FIG. 3 is a characteristic diagram showing the relationship between an actual value and a current regulator output. In FIG. 1, reference numerals 11, 12, 13, and 14 are operational amplifiers. The operational amplifier 11 functions as a proportional element, the operational amplifier 12 functions as an integral element, the operational amplifier 13 functions as an addition element, and the operational amplifier 14 functions as an integral element.
The deviation detection elements are respectively formed by. Also, 2
is a field effect transistor (FET), 3 is a control circuit, R
e R1-R4 are resistors, and C is an integrating capacitor.

The FET 2 and the control circuit 3 are operated by a control signal given only when a set value is changed. Due to the operation of FET 2, current i is determined by the output proportional to the deviation between the current setting value given via operational amplifier 14 and the actual value, resistor R4, etc. is applied to the integrating capacitor C, the capacitor C is charged and discharged depending on the magnitude and direction of this current i0, and unnecessary charging and discharging is avoided. At this time,
Although the integration operation by the amplifier 12 is enabled, the integration operation is performed slowly due to the above-described charging and discharging. As a result, the output waveform of the current regulator (ACR) becomes gradual after time t1 as shown in Figure 2 (B), and therefore the actual current value has a good waveform without overshoot, as shown in Figure 2 (C). becomes. Incidentally, time t1 is the time when the above control signal is given, and FIG. 2(a) is a characteristic diagram showing the change over time of the current setting value. Although overshoot has been mainly explained above, it goes without saying that the same applies to undershoot.

〔Effect of the invention〕

According to this invention, since the capacitor of the integral element is charged and discharged according to the input amount (a function of the deviation between the set value and the actual value), excessive charging and discharging is avoided, resulting in overshoot of the load current. Undershoot can be minimized in the front. Therefore, a large inductor such as a superconducting magnet coil is also made to have 1 value and 1 value.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
A characteristic diagram showing the relationship between current setting value, actual value, and current regulator output to explain the operation of the figure. Figure 3 is a configuration diagram showing an example of a general load control system. FIG. 2 is a characteristic diagram showing the relationship between a current setting value, an actual value, and a current regulator output to explain the operation of the controller. Symbol explanation 11.12, 13.14... operational amplifier (op amp), 2... field effect transistor (FE)
T), 3... Control circuit, 6... Power converter, 7... Load, 8... Current detector, 9...・Power converter control device, 91...
...Current regulator (ACFL), 92...Ignition angle regulator, R2R1-R4...Resistance, C...
... capacitor agent patent attorney Akio Namiki agent patent attorney Kiyoshi Matsuzaki NI! l Kasumi 21!1 1, Ginkaku

Claims (1)

[Claims] In a load current control device that uses a proportional and integral element to feedback-control the current to flow through a load supplied via a power converter, the integral element has a proportional current that is proportional to the deviation between the current setting value and the actual value. A current application circuit that applies current and a control circuit that disables the integral operation of the integral element before enabling it are provided, and when changing the load current setting value, the control circuit enables the integral operation and also disables the integral operation of the integral element. A load current control device that controls the amount of input current by flowing the proportional current.