JPS61259177A - Apparatus for measuring load current - Google Patents

Abstract

PURPOSE:To measure a load current with high accuracy, by sending currents to load by a voltage supply source and a current supply source and detecting the time, when the current is made to flow to the load only from the current supply source, by the current direction detector connected between the voltage supply source and the load. CONSTITUTION:A current iR coming to the magnitude judge reference of a load current is set to a current source 14 and the output of a voltage comparator 15 is observed to make it possible to perform the magnitude judgement of the load current iL to the reference value iR regardless of the accuracy of the resistance values possessed by diodes 12, 13. Because said diodes 12, 13 have characteristics taking a low resistance value to a large current and a high resistance value to a small current, when load 16 is an active element and the current iL is pulsated between the large current and a minute current, pref. effect, such that the drop of applying voltage is suppressed small in the large current and voltage is generated in the minute current with good sensitivity, is brought about.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a load current measuring device that applies a voltage to a load and measures the load current at that time.

[Technical background of the invention and its problems]

An example of this type of conventional device is shown in FIG. In the figure, 1 is a voltage source, which applies voltage to a load 3 through a resistor 2.

The resistor 2 is a current detection resistor having a multiplication value R8, and the voltage e1 across the resistor 2 is given by the following formula.

e1 = Rg ' SL - River (1) 4 is a differential voltage measuring device whose input current can be ignored.If its gain is 1, the output voltage to ground e2 is the input differential voltage across the resistor 20. It is equal to the voltage and becomes 9 in the following equation.

e2=RB-re (2) 5 is a voltage comparator sb, which outputs logic signals of "l#" and ""0# according to the polarity of the difference between voltages e2 and 03.

Assume that the voltage e6 can be set to a voltage that satisfies the following equation.

e3=R, l-import...River...(3) and (
7) The subscript in equation (3) is the reference current value. At this time, it can be known from the output state of the voltage comparator 5 whether the load current iL is larger or smaller than the reference current iR.

However, in the case of the above device, it is a condition that equation (3) is expressed as fft, and therefore, there is a drawback that R5 of the current detection resistor 2 needs to be highly linear and highly stable.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a load current measuring device that can measure the current flowing to a load without using a highly accurate current detection resistor.

[Summary of the invention]

In order to achieve the above object, the present invention connects a current detection element between a voltage supply source and a current supply source, and provides a differential voltage detector that detects the voltage across the element, and connects the current detection element to the current supply source. The connection point of the source is the load connection end, and when the current flowing to the load is equal to the current flowing from the current supply source, the voltage across the current detection element is zero, and the current to the unequal electromotive current detection element Based on the direction of the current, it is determined whether the current value flowing through the load is larger or smaller than a certain value.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 11 is a voltage source p, which is a diode 12
Alternatively, a voltage is applied to the device under test (load) 16 through I3. z4 is a current source, which outputs a reference current (1) when determining the magnitude of the current flowing to the load 16. .13 and the polarity of 1 are detected to output logic signals S of ``1'' and ``0''.As the voltage comparator 15, one whose input current is negligibly small is used. Reference numeral 17 denotes a bino bus capacitor that suppresses voltage fluctuations due to high frequency current flowing to the load 16.

In FIG. 1, when a voltage is applied to the load 16 from the voltage source 11' through the diode 12 or 13, the current flowing to the load 16 is iL. On the other hand, the current source 14 receives a large amount of current flowing out. At this time, if the total current flowing to the diodes x2 and 13 connected in antiparallel is omitted, the following equation holds true. However, it is assumed that the input current to the voltage comparator I5 can be ignored.

z, = sL-s, ... river (4) Also, the voltage ett across the diode is 0 [v] when fg = O (A, ), and e14% when i, % 0 (A).
It is clear that OCv:+. and voltage e
4. It is also clear that the polarity of is determined by the polarity of the current is. The polarities of the voltages t and b are determined by the magnitude relationship between the currents iL and il from equation (4). The voltage comparator Z5 has a function of detecting the polarity of the input differential voltage, that is, "11", and outputting a logic signal S ("1" or 0').

Therefore, the state of the logic signal S is determined by the magnitude relationship between the current i and the current i.

As can be seen from the above explanation, by setting the current source 14 as a reference for determining the magnitude of the load current, and observing the output logic state of the voltage comparator 15, the diode 12.13
Regardless of the accuracy of the resistance value of the load current L, it is possible to determine the magnitude of the load current L with respect to the reference value A8. In addition, diodes 12 and 13 have low resistance values for large currents.
Since it has the characteristic of high resistance value for small current, the load I
In the case where 6 is an active element and the multicurrent iL is pulsating between a large current and a small current, the desirable effect of suppressing the applied voltage drop to a large current and generating a voltage sensitively to a small current can be achieved. It is something that brings.

Note that the present invention is not limited to the embodiments, and can be applied in various ways. 1. For example, as described above, the present device, which instantaneously has a small voltage drop against large currents and can measure minute currents quickly and accurately, can be widely applied as a current measuring device for active elements. Further, in the embodiment, an anti-parallel diode was used as the current detection element, but any resistor, transistor, or other element whose voltage polarity is reversed depending on the direction of current may be used.

〔Effect of the invention〕

As explained above, according to the present invention, since it is only necessary to know the direction of the current flowing through the current detection element, highly accurate current measurement is possible regardless of the resistance value accuracy of the current/voltage conversion element for detecting the current. be. Furthermore, since a diode or the like can be used as the current detection element, there is little voltage drop at large currents (unlike conventional systems that use ordinary resistors). This characteristic is useful, for example, when detecting a cell defect that can be detected with a normal funk test by measuring a static small current while suppressing the voltage drop caused by the instantaneous large current when each address of an IC memory is accessed. It is effective for

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional device. 11... Voltage source, 12.13... Diode (current detection element), 14... Current source, 15... Voltage comparator s 16... Negative W, 17... Bypass capacitor. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (2)

[Claims] (1) A current detection element is connected between a voltage supply source and a current supply source, a differential voltage detector is provided to detect the voltage across the element, and the connection point between the current detection element and the current supply source is connected to a load. When the current flowing through the load is equal to the current flowing from the current supply source, the voltage across the current sensing element becomes zero, and when they are not equal, the value of the current flowing through the load is determined from the direction of the current flowing to the current sensing element. A load current measuring device characterized by determining whether the load current is larger or smaller than a certain value. (2) The load current measuring device according to claim 1, wherein the current detection element is an antiparallel circuit of diodes.