JPH02306169A - Dc current detector - Google Patents

Abstract

PURPOSE:To enhance the detection accuracy of a small current region by connecting an output resistor for expanding the detection level of the small current region to a usual output resistor in series and short-circuiting and opening the same corresponding to the magnitude of a current to be detected. CONSTITUTION:In a current detection part, by driving the output winding wound around the iron core magnetically coupled with a primary conductor to which a current to be detected flows by an AC power supply, the detection voltage corresponding to the current to be detected flows to the feedback winding 7 wound around the same iron core. The first and second output resistors 8, 9 are connected to said winding 7 in series and the output voltage at the connec tion point of both of them is compared with reference voltage EREF by a compa rator 10 and, when the output voltage becomes larger than the reference voltage, an output signal 11 is generated and a switch circuit 12 is turned ON to short- circuit the resistor 9. The output voltage E01 exclusive to the small current region between both terminals of the resistors 8, 9 is high in level to enhance detection resolving power. Therefore, the effect of foreign noise and the offset voltage of a signal processing system is prevented and the detection accuracy in the small current region is enhanced.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a DC current detection device that detects excitation current of a particle accelerator or the like with high precision.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional DC current detection device disclosed in, for example, Japanese Patent Application Laid-Open No. 55-60860. A direct current to be detected (2) is passed through the primary conductors that are magnetically coupled and connected in series. 3 is an output winding wound around each iron core 1 and connected in series; 4 and 5 are current detection units provided for each of the two output windings 3; 6
is a power amplifier that amplifies the voltage e, +e2 which is the algebraic sum of the detected voltage eI+e2 of the current detection unit 4.5, and 7 is a power amplifier for each iron core 1.
8 is an output resistor connected between the feedback winding VA 7 and ground to obtain an output voltage E0. In the current detection section 4.5, 41.51 is an AC power supply, 42, 43, 52.53 are rectifying diodes, 44.
45, 54.55 are negative current blocking resistors, 46.47, 5
6.57 is a bypass diode for passing the maximum current, and 48.58 is a detection resistor for obtaining a detection voltage eI+eZ. Next, the operation will be explained. With the detected current 11 flowing through the primary conductor 2, each output winding 3 is driven by the AC power source 41°51 of the current detection section 4.5, so that the detected current is applied to each detection resistor 48°58. I, and a current according to the excitation current of the iron core 1 flows, and a detected voltage el+82 is obtained. This detection voltage e, and e2
The voltage of the algebraic sum e, +82 is applied to the power amplifier 6 and power amplified. Figure 4 (a), (b),
(c) is the detected current I, the detected voltage “I+”2 and e
, +ez is shown. The output current of the power amplifier 6 flows into the feedback winding 7 with a polarity opposite to that of the detected current 1 flowing through the primary conductor 2. The current of this feedback winding vA7 is the detected current 11 of the primary conductor 2.
It stops at the number of amperes depending on the number of turns and remains stable. Therefore, the output voltage E0 across the output resistor 8 connected to this current circuit is proportional to the detected current (2). The relationship between the detected current 11 and the output voltage E0 has linearity as shown in FIG. From the above explanation, it can be seen that the value of the output resistor 8 can be increased to increase the detection accuracy. Figure 6 is for explaining this, and shows the current output from the power amplifier 6.
, passes through the feedback winding 7 and the output resistor 8, but since this current is determined by the detected current I, theoretically, if the output resistor 8 is increased, the output voltage E0 will also be increased,
The characteristics are shown in characteristics 21 and 22 in FIG. In the same figure,
Characteristic 21 shows the case where the output resistance 8 is small, and characteristic 22 shows the case where the output resistance 8 is large. However, with conventional DC current detection devices, such an operation is actually impossible. This is because when the output resistance 8 in FIG. 7 has a high characteristic 22, when a certain current 11 is exceeded,
The output of the power amplifier 6 undergoes a saturation phenomenon. This depends on the characteristics of the power amplifier 6 itself, but also on the magnitude of the power supply voltage used for the power amplifier 6. Therefore, the input current (
Even though the current to be detected (r,) is flowing, the power amplifier 6 is saturated and no feedback current can be passed. Therefore, the region of the negative slope portion 20 of the characteristic shown in FIG. 4(c) Since the input current 11 enters the current and becomes a positive feedback signal, even if the input current 11 becomes small, its output no longer becomes small, and the characteristics shown in FIG. 5 can no longer be obtained.

[Problem to be solved by the invention]

Since the conventional DC current detection device is configured as described above, it is not possible to increase the detection accuracy in the small current region, and even if an attempt is made to increase the saturation voltage of the power amplifier 6 as a countermeasure, it is necessary to increase the power supply voltage. Furthermore, since the power supply voltage is determined by the rating of the power amplifier 6, there are problems in that it cannot be easily changed. The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a DC current detection device that can improve detection accuracy in a small current region.

[Means to solve the problem]

The DC current detection device according to the present invention newly connects a separate output resistor in series with the conventional output resistor, and when the detection voltage of the conventional output resistor exceeds a predetermined value, the newly connected output The resistor is short-circuited.

[Effect]

Since the outputs at both ends of the two output resistors in this invention have a large resistance value, in the small current region, the signal is of a higher level compared to the conventional one, and the detection resolution is increased. It is less susceptible to the effects of system offset voltage, etc., and can improve detection accuracy.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows the output resistance circuit portion of the DC current detection device according to the present invention, and 6, 7.8 correspond to the same reference numerals in FIG. Further, other parts not shown have the same configuration as in FIG. 3. In FIG. 1, 9 is the second output resistor connected in series between the first output resistor 8 and the feedback winding 7, and EO is the first output resistor 8.
and the output voltage exclusively for the normal current region taken out from the connection point of the second output resistor 8.9, Eot is the output voltage taken out from the connection point of the feedback winding 7 and the second
The output voltage exclusively for the small current region taken out from the connection point with the output resistor 9 is the current of the feedback winding 7. 10 is an output voltage E generated by the first output resistor 8. A comparator detects that the level of 1 has reached a preset reference voltage E□, 11 is the output signal of the comparator 10, 12 is operated by the output signal 11, and short-circuits the second output resistor 9. It is a switch circuit. Next, the operation will be explained. In FIG. 2, the horizontal axis indicates the detected current 1. The vertical axis represents the output voltage E of the DC current detection device according to the present invention. , and E02. In FIGS. 1 and 2, the output voltage E is dedicated to the small current region. Since 2 is the voltage across the output resistors 8 and 9, its level is large, and the detection resolution is greatly improved compared to the conventional one. On the other hand, due to constraints on the output voltage level of the power amplifier 6, the comparator 10 sets the voltage across the first output resistor 8 (normal level output voltage E0
1) is monitored and its value is a preset threshold value E II
When EF is exceeded, the output signal 11 is immediately generated, the switch circuit 12 is turned on, and the second output resistor 9 is short-circuited. As described above, after the comparator 10 operates, the normal output voltage EOI continues to maintain the normal level regardless of the operation of the switch circuit 12. On the other hand, the output voltage E for small current area
. 2 is suppressed to a level higher than the output voltage EOI by the voltage drop Δe of the switch circuit 12, so the load on the power amplifier 6 is extremely small, and it operates in the same way as a conventional detection device. . Also, the output voltage E of this device. IIEOZ is always configured to be able to output to the outside, so in the external circuit ■1≦I
The output signal can be switched and used at any point within the IIEF range. In Figure 2 - for example 1
．． =1. The output voltage E o + + E at the point
The output signal characteristics when switching oz are shown in dashed line 13.
It is shown in Note that in the above embodiment, the output voltage is E. In the above example, the output voltages EIII and Eoz are output independently of each other and the output voltages EIII and Eoz are selected and switched in an external circuit.
) and outputs a signal indicating whether the output voltage after switching is the enlarged level or the normal level to the outside, the same effect as in the above embodiment can be obtained.

【Effect of the invention】

As described above, according to the present invention, an output resistor for expanding the detection level in a small current region is connected in series with a normal output resistor,
In addition, the latter output resistor is configured to be automatically short-circuited or opened depending on the magnitude of the current to be detected, so it is possible to expand the detection level in the small current region, improve detection accuracy, and improve other The effect is that the same accuracy as the conventional method can be obtained without saturation even in this area.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing the output resistance circuit portion of a DC current detection device according to an embodiment of the present invention, and FIG.
Output signal characteristic diagram, FIG. 3 is a configuration diagram showing a conventional DC current detection device, FIG. 4 is a characteristic diagram for explaining the operation of the device, FIG. 5 is an input-output signal characteristic diagram of the device, FIG. 6 is a configuration diagram showing the main parts of the device, and FIG. 7 is a characteristic diagram for explaining the operation of the device. ■ is the iron core, 2 is the first ring body, 3 is the output winding, 4゜5 is the current detection section, 41.51 is the AC power supply, 7 is the feedback winding, 8 is the first output resistor, 9 is the second output resistance, 10 is the comparator, 1
1 is an output signal, 12 is a switch circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 1 3. Figure 3, Figure 5

Claims (1)

[Claims] By driving a primary conductor through which the current to be detected flows, an iron core magnetically coupled to the primary conductor, an output winding wound around the iron core, and the output winding with an AC power source, A current detection section configured to obtain a detected voltage according to the detected current, a feedback winding through which a current according to the detected voltage flows and is wound around the iron core, and connected in series to the feedback winding. a comparator that compares an output voltage obtained at a connection point between the first and second output resistors and a reference voltage; and a comparator that is controlled by an output signal of the comparator. and a switch circuit that short-circuits the second output resistor.