US-12625168-B2 - Current measurement device and current measurement method

Abstract

An object is to separately measure the DC and AC components included in a measurement target current. The current measurement device includes a core, a coil, an element, an AC measurement circuit, a low-pass filter, a current adjustment circuit, and a DC measurement circuit. The core allows magnetic flux to flow therethrough due to the measurement target current. The element generates a feedback voltage, based on the magnetic flux flowing along the core. The AC measurement circuit measures the AC component of the measurement target current, based on the feedback voltage. The current adjustment circuit allows a feedback current to flow through the coil, counteracting the DC component of the core magnetic flux, based on the feedback voltage from which the AC component has been removed by the low-pass filter. The DC measurement circuit measures the DC component of the measurement target current, based on the feedback current.

Inventors

• Yusuke Shindo

Assignees

• HONDA MOTOR CO., LTD.

Dates

Publication Date

20260512

Application Date

20240223

Priority Date

20230331

Claims (5)

1. 1 . A current measurement device that measures a measurement target current that is a current flowing through a measurement target, the device comprising: a core through which magnetic flux flows due to the measurement target current; a coil externally fitted around the core and not electrically connected to the measurement target; an element that generates a feedback voltage, based on core magnetic flux that is a magnetic flux flowing along the core; an AC measurement circuit that measures an AC component of the measurement target current, based on the feedback voltage; a low-pass filter that removes an AC component equal to or above a predetermined frequency from the feedback voltage, a current adjustment circuit that allows a feedback current to flow through the coil, based on the feedback voltage, from which the AC component has been removed, to counteract a DC component of the core magnetic flux; and a DC measurement circuit that measures a DC component of the measurement target current, based on the feedback current.
2. 2 . The current measurement device according to claim 1 , wherein the AC measurement circuit includes an operational amplifier that amplifies the feedback voltage generated by the element, and the AC measurement circuit measures an AC component of the measurement target current, based on the feedback voltage amplified.
3. 3 . The current measurement device according to claim 1 , further comprising: a preliminary low-pass filter that removes an AC component equal to or above a preliminary frequency that is higher than the predetermined frequency from the feedback voltage, before the low-pass filter removes an AC component equal to or above the predetermined frequency from the feedback voltage, and the AC measurement circuit measures an AC component of the measurement target current, based on the feedback voltage from which the AC component equal to or above the preliminary frequency has been removed.
4. 4 . A current measurement method of measuring a measurement target current by using: a core through which magnetic flux flows due to the measurement target current that is a current flowing through a measurement target; a coil externally fitted around the core and not electrically connected to the measurement target; and an element that generates a feedback voltage, based on core magnetic flux that is a magnetic flux flowing along the core; the method comprising the steps of: measuring an AC component of the measurement target current, based on the feedback voltage; removing an AC component equal to or above a predetermined frequency from the feedback voltage using a low-pass filter; allowing a feedback current to flow through the coil, based on the feedback voltage, from which the AC component has been removed, to counteract a DC component of the core magnetic flux; and measuring a DC component of the measurement target current, based on the feedback current.
5. 5 . A current measurement device that measures a measurement target current that is a current flowing through a measurement target, the device comprising: a core through which magnetic flux flows due to the measurement target current; a coil externally fitted around the core; an element that generates a feedback voltage, based on core magnetic flux that is a magnetic flux flowing along the core; an AC measurement circuit that measures an AC component of the measurement target current, based on the feedback voltage; a low-pass filter that removes an AC component equal to or above a predetermined frequency from the feedback voltage, a current adjustment circuit that allows a feedback current to flow through the coil, based on the feedback voltage, from which the AC component has been removed, to counteract a DC component of the core magnetic flux; and a DC measurement circuit that measures a DC component of the measurement target current, based on the feedback current, the device further comprising: a preliminary low-pass filter that removes an AC component equal to or above a preliminary frequency that is higher than the predetermined frequency from the feedback voltage, before the low-pass filter removes an AC component equal to or above the predetermined frequency from the feedback voltage, and the AC measurement circuit measures an AC component of the measurement target current, based on the feedback voltage from which the AC component equal to or above the preliminary frequency has been removed.

Description

This application is based on and claims the benefit of priority from Japanese Patent Application No. 2023-058223, filed on 31 Mar. 2023, the content of which is incorporated herein by reference. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a current measurement device that measures a measurement target current flowing through a measurement target. Related Art Some current measurement devices include a core, a Hall element, a current adjustment circuit, a coil, and a current measurement circuit. The core allows magnetic flux to flow therethrough due to the measurement target current. The coil is externally fitted around the core. The Hall element generates a feedback voltage, based on the core magnetic flux, which is the magnetic flux flowing along the core. The current adjustment circuit allows a feedback current to flow through the coil, counteracting the core magnetic flux, based on the feedback voltage. The current measurement circuit measures the measurement target current, based on the feedback current. Patent Document 1: Japanese Utility Model Unexamined Application, Publication No. Hei 5-81730 SUMMARY OF THE INVENTION With such a current measurement device, the core magnetic flux can be counteracted with the feedback current. Therefore, even when the core cross-sectional area is smaller compared to those used in magnetic-proportional current measurement devices, the core magnetic flux can be sufficiently suppressed, thus the heat generation inside the core and the magnetic saturation can be sufficiently suppressed. However, the inventors have identified potential problems as follows. Namely, when generating a feedback current based on the feedback voltage, a response delay occurs in the current adjustment circuit. Consequently, when the frequency of the AC component included in the measurement target current is high, a significant phase delay occurs in the AC component of the feedback current relative to the AC component of the measurement target current. This characteristic may lead to adverse effects. Specifically, in the most extreme case, if this phase delay becomes half the wavelength of the AC component of the measurement target current, it could amplify, rather than counteract, the AC component of the core magnetic flux with the AC component of the feedback current. Moreover, when the measurement target current includes both DC and AC components, the feedback current also includes DC and AC components. Therefore, such current measurement circuits for measuring the measurement target current, based on the feedback current, cannot separately measure the DC and AC components included in the measurement target current. The present invention has been made in view of the above circumstances with objects to suppress the adverse effects due to the phase delay in the AC component of the feedback current relative to the AC component of the measurement target current, as well as to separately measure the DC and AC components included in the measurement target current. The inventors have made the present invention by finding that the objects can be achieved by measuring the AC component of the measurement target current, based on the feedback voltage, then removing the AC component from the feedback voltage, and measuring the DC component of the measurement target current, based on the feedback current. The present invention is the current measurement device described below in (1) to (3) and the current measurement method described below in (4). (1) A current measurement device that measures a measurement target current that is a current flowing through a measurement target, in which the device includes: a core through which magnetic flux flows due to the measurement target current;a coil externally fitted around the core;an element that generates a feedback voltage, based on core magnetic flux that is a magnetic flux flowing along the core;an AC measurement circuit that measures an AC component of the measurement target current, based on the feedback voltage;a low-pass filter that removes an AC component equal to or above a predetermined frequency from the feedback voltage, a current adjustment circuit that allows a feedback current to flow through the coil, based on the feedback voltage from which the AC component has been removed, to counteract a DC component of the core magnetic flux; anda DC measurement circuit that measures a DC component of the measurement target current, based on the feedback current. With this configuration, the low-pass filter removes the AC component from the feedback voltage. The current adjustment circuit allows the feedback current to flow through the coil, based on the feedback voltage from which the AC component has been removed. Therefore, the feedback current does not include any AC component for counteracting the AC component of the core magnetic flux. Thus, a phase delay in the AC component of the feedback current relative to the