JP2014055876A - Current detection and measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a current detection and measurement device for measuring charge/discharge characteristics of a battery, a capacitor, or the like to be stably operated with low loss by an inexpensive configuration.SOLUTION: A current detection and measurement device has a plurality kinds of current measuring resistances connected between a tester and a measurement object like a battery or a capacitor and detects or measures a current flowing in the measurement object by voltages at both ends of the current measuring resistances. A field effect transistor which, in a turned-on state, shorts a circuit between both ends of the current measuring resistances connected between a test measurement power supply part and the measurement object and a forward polarity diode in a direction opposite to a forward direction of a parasitic diode of the field effect transistor are connected in parallel, and an abnormal voltage rise is suppressed by respective forward voltages of the diode and the parasitic diode of the field effect transistor.

Description

  The present invention relates to a current detection and measurement apparatus that stably detects or measures a charging current or a discharging current for an object to be measured such as a battery or a capacitor with low loss.

  Various devices that use batteries, capacitors, and the like of various configurations as DC power sources are known. Therefore, it is necessary to measure charge / discharge characteristics in advance using batteries, capacitors, and the like that are used as DC power sources as objects to be measured. . Various means have already been proposed and put to practical use as means for measuring such charge / discharge characteristics. Generally, a means for connecting a resistor in series, measuring the voltage across the resistor corresponding to the magnitude of the current flowing through the object to be measured through the resistor, and obtaining the current according to the relationship with the resistance value However, when a current range to be detected or measured is wide, a means for switching a plurality of resistors having different resistance values to correspond to the range of detection or measurement is applied.

  FIG. 5 shows a main part applied as a conventional battery charge / discharge characteristic test apparatus, in which 21 is a test measurement power supply unit, 22 is a battery under test, 23 is a test measurement unit, 24 is a test control unit, Q01 is a field effect transistor, and R01 and R02 are current measurement resistors. The resistance values of the resistors R01 and R02 are, for example, R01> R02, the voltage at both ends of the resistor R01 is measured by the test measurement unit 23 at the time of small current measurement, and at both ends of the resistor R02 at the time of large current measurement. The voltage is measured by the test measurement unit 23. At the time of this large current measurement, the voltage across the resistor R01 having a large resistance value for small current measurement becomes high. Therefore, under the control of the test measurement unit 23, the transistor Q01 is turned on and the resistor R01 is short-circuited. As a result, it is possible to avoid high voltage input when measuring a large current input to the test measurement unit 23.

  FIG. 6 shows a main part applied as a test apparatus for other charge / discharge characteristics in the conventional example, 31 is a test and measurement power supply unit, 32 is a battery under test, 33 is a test and measurement unit, 34 is a test control unit, 35 is a switching control unit, R31 and R32 are current measuring resistors, Q31 and Q32 are field effect transistors constituting the changeover switch SW31, and Q33 and Q34 are field effect transistors constituting the changeover switch SW32. When the field control transistor is controlled by the switching control unit 35 so that one switching switch SW31 (field effect transistors Q31, Q32) is turned on and the other switching switch SW32 (field effect transistors Q33, Q34) is turned off, A current flows through the battery under test 32 via R31, and the voltage across the resistor R31 is input to the test measurement unit 33, whereby the current flowing through the battery under test 32 can be measured and one of the switches is switched. When the switch SW31 (field effect transistors Q31, Q32) is turned off and the other changeover switch SW32 (field effect transistors Q33, Q34) is turned on, the current flowing through the battery under test 32 passes through the resistor R32. The voltage across the resistor R32 is input to the test measurement unit 33. And it makes it possible to measure the current flowing through the tested battery 32.

  Also, the voltage across the resistor R01 is compared with the reference voltage by comparing the voltage across the resistor R01, which has a configuration similar to the configuration shown in FIG. 5 and has a resistance value of R01> R02. When the reference voltage is exceeded, it indicates that a current exceeding the set current value has flowed. In that case, by the control configuration that turns on the field effect transistor Q01 connected in parallel with the resistor R01 having a high resistance value, A means has been proposed in which the current flowing through the resistor R01 is bypassed by a field-effect transistor controlled to be in an on state, and an increase in voltage generated across the resistor R01 having a high resistance value is automatically suppressed (for example, Patent Documents). 1).

JP 2009-150762 A

  A battery and a capacitor are required to be able to perform a wide range of tests on charge characteristics and discharge characteristics. In this case, the current direction during the charge characteristic test is opposite to the current direction during the discharge characteristic test, and it is necessary to be able to measure the current flowing in either direction. Further, it is desired to have a configuration capable of measuring various types of batteries and capacitors. In addition, since there are many types of charge / discharge capacities of batteries and capacitors, it is required to expand the test measurement range, and ensuring safety is also important. For example, in the configuration shown in FIG. 5 of the conventional example, the field effect transistor Q01 for bypassing the resistor R01 is turned off at the start of the test, and at that time, the battery under test 22 and the test measurement power supply unit 21 are disconnected. When an inrush current flows between them, the voltage at both ends of the high-resistance resistor R01 becomes an abnormally high voltage and there is a high possibility of causing a failure, and the high-resistance resistor R01 burns out. There was also a problem that increased the possibility of doing so. In the configuration shown in FIG. 6 of the conventional example, two field effect transistors are provided for each parasitic diode in order to configure a switch circuit for switching between the charging direction and the discharging current direction. It is necessary to connect in series so that the polarities of the two are opposite to each other.

  An object of the present invention is to solve the problems of the conventional example described above, and to enable a charge / discharge characteristic test with a relatively simple configuration and an inexpensive configuration.

  The current detection and measurement apparatus of the present invention connects a plurality of types of current measurement resistors between the test apparatus and the object to be measured, and detects the current flowing through the object to be measured by the voltages at both ends of the current measurement resistor. A current detection measuring device for measuring, a field effect transistor for short-circuiting both ends of the current measuring resistor connected between the test device and the object to be measured in an ON state, and the field effect transistor It has a configuration in which a diode having a polarity in the forward direction opposite to the forward direction of the parasitic diode is connected in parallel.

  In addition, the field effect transistor for short-circuiting both ends of each of the resistances other than the minimum value among the plurality of types of current measurement resistors, and the forward direction of the parasitic diode of the field effect transistor It has a configuration in which a diode having a reverse polarity in the forward direction is connected in parallel.

  In the configuration in which the charging current or discharging current of the battery or capacitor of the object to be measured is measured by the voltage across the current measuring resistor, the small current measuring resistor is compared to the large current measuring resistor. The resistance value is large. Therefore, even when the same current flows, the voltage at both ends of the small current measuring resistor becomes high. As a configuration for avoiding such voltage rise and switching the current measurement range, a field effect transistor and a diode having a forward polarity opposite to the forward direction of the parasitic diode are connected in parallel. With a relatively simple configuration, it is possible to switch the measurement current range and suppress an abnormal voltage rise at both ends of the measurement resistor.

It is explanatory drawing of Example 1 of this invention. It is principal part explanatory drawing of the switch part of Example 1 of this invention. It is operation | movement explanatory drawing by the switching of Example 1 of this invention. It is explanatory drawing of Example 2 of this invention. It is explanatory drawing of a prior art example. It is explanatory drawing of a prior art example.

  The current detection and measurement apparatus of the present invention connects a plurality of types of current measurement resistors between the test apparatus and the object to be measured, and detects the current flowing through the object to be measured by the voltages at both ends of the current measurement resistor. A current detection measuring device for measuring, a field effect transistor for short-circuiting both ends of the current measuring resistor connected between the test device and the object to be measured in an ON state, and the field effect transistor It has a configuration in which a diode having a polarity in the forward direction opposite to the forward direction of the parasitic diode is connected in parallel.

  Also, a field effect transistor for short-circuiting both ends of each of the resistances other than the minimum value among the plurality of types of current measurement resistors, and the forward and reverse directions of the parasitic diode of the field effect transistor The forward polarity diode is connected in parallel.

  FIG. 1 is an explanatory diagram of Embodiment 1 of the present invention, in which 1 is a measurement power source unit, 2 is a battery under test, 3 is a measurement control unit, 4 is a measurement detection unit, 5 and 6 are switching units, and R1 and R2 Is a current measuring resistor, Q1 is a field effect transistor, D1 is a diode, D2 is a parasitic diode of the field effect transistor, and is connected so that the forward polarity of the diode D1 is opposite to that of the parasitic diode D2 of the field effect transistor Q1 To do. The switching unit 6 connected in parallel with the current measuring resistor R2 has the same configuration as that of the switching unit 5, but a field effect transistor, a diode, and the like are not shown. The battery under test 2 can be a capacitor under test for charging / discharging. Hereinafter, a case where a battery is used as a device under test for a charge / discharge test will be described. Although the measurement power supply unit 1 is not shown in its internal configuration, the measurement power supply unit 1 includes a control configuration for performing charge control and discharge control on a battery 2 or a capacitor as a known device to be tested. Note that if the battery under test 2 is a device under test, the measurement power supply unit 1, the measurement control unit 3, and the measurement detection unit 4 are persons corresponding to the test apparatus.

  The current measurement resistors R1 and R2 connected between the measurement power supply unit 1 and the battery under test 2 have, for example, a resistance value relationship of R1> R2, and the resistor R1 is used for measuring a small current and the resistor R2 is used for measuring a large current. For use. Therefore, when measuring a small current, the measurement control unit 3 controls the field effect transistor Q1 of one switching unit 5 to be off and the field effect transistor (not shown) of the other switching unit 6 to be on, The voltage Vr1 at both ends of the current measuring resistor R1 is added to the measurement control unit 3, and the current flowing through the battery under test 2 can be obtained by calculating Vr1 / R1. When measuring a large current, the measurement control unit 3 controls the field effect transistor Q1 of the switching unit 5 to be turned on and the field effect transistor not shown in the other switching unit 6 to be turned off. By adding the voltage Vr2 across R2 to the measurement control unit 3 and calculating Vr2 / R2, the current flowing through the battery under test 2 can be obtained.

  The currents flowing through the current measuring resistors R1 and R2 are reversed in direction during the charge test and the discharge test for the battery under test 2. In the connection state of the illustrated field effect transistor Q1, during the discharge test, Even when the field effect transistor Q1 is controlled to be in the OFF state, the forward direction is applied to the parasitic diode D2, and the voltage across the resistor R1 can be suppressed by the parasitic diode D2. Similarly, also in the switching unit 6, the voltage across the resistor R2 can suppress an abnormal voltage rise by a diode (not shown) and a parasitic diode of a field effect transistor. For example, when a high voltage is suddenly applied to the battery under test 2 from the measurement power supply unit 1, a large current flows through the current measurement resistors R1 and R2 before the field effect transistor Q1 is turned on. It will be in a state of burning. However, as described above, the diode D1 and the parasitic diode of the field effect transistor Q1 cause the voltage across the resistors R1 and R2 to be suppressed by the forward voltage of the diode regardless of the direction of current flow. The burnout of the current measuring resistors R1 and R2 can be avoided.

  FIG. 2A shows the main configuration of the switching unit 5 described above. The switching unit including the field effect transistor Q1, its parasitic diode D2, and the additionally connected diode D1 has been conventionally shown in FIG. As shown in FIG. 2B, the two field effect transistors Q01 and Q02 (the field effect transistors Q31 and Q32 or the field effect transistors Q33 and Q34 in FIG. 6) are replaced with the forward polarities of the respective parasitic diodes. If the circuit is not connected in the opposite direction, it cannot function sufficiently as a changeover switch for a circuit in which the current direction is reversed. However, in the present invention, FIG. As shown in the figure, it is possible to configure with one field effect transistor Q1 and one diode D1, and it is possible to reduce the size and cost.

  FIG. 3 shows voltages V1 to V3 when three current measuring resistors R1 to R3 having different resistance values are connected in series, and a forward voltage Vf between a parasitic diode of a field effect transistor and a diode connected in parallel. The resistance values of the current measurement resistors R1 to R3 indicate a relationship of R1> R2> R3, and accordingly, the current measurement resistors R1, R2 when the same current flows. , R3 have a relationship of V1> V2> V3. However, as shown in FIG. 1 and FIG. 2A, when the forward voltage of each of the resistors R1 to R3 is Vf by the field effect transistor Q1, its parasitic diode D2, and the diode D1, respectively. It is possible to suppress the voltage at both ends as indicated by Vf. Therefore, it is possible to prevent burning due to an inrush current or the like without using the resistors R1 to R3 for high power. In addition, the voltage at the time of the measurement of the flowing electric current measures current as a voltage below the above-mentioned forward voltage Vf.

  FIG. 4 is an explanatory diagram of Embodiment 2 of the present invention, in which R10 to R12 are current measurement resistors, 11 is a measurement power supply unit, 12 is a battery under test, 13 is a measurement control unit, and R10 to R12 are for current measurement. Resistors, Q11 and Q12 are field effect transistors, D11 and D12 are diodes, A11 and A12 are operational amplifiers, and Vr11 and Vr12 are reference voltages. Although the parasitic diodes of the field effect transistors Q11 and Q12 are not shown, the forward direction is opposite to that of the parallel-connected diodes D11 and D12. The resistor R10 is a resistor for measuring a large current with a minimum resistance value, and shows a case where the resistor R10 has a low resistance value that does not become an abnormal voltage even if it exceeds the normal current measurement range. Therefore, the field effect transistor for short-circuiting both ends of the resistor R10 is omitted. However, like the other resistors R11 and R12, the field effect transistor and the diode are connected in parallel. You can also. Also, current measurement resistors R10 to R12 are connected in series between the measurement power source 11 and the battery 12 to be tested, and the current measurement resistor R10 having the smallest resistance value is used for measuring a large current. In the control, as described above, the case of a low resistance value that does not cause an abnormal voltage is shown, and the resistances R11 and R12 at both ends of the current measurement resistor are in a relation of R10 <R11 <R12. Since the voltage may rise abnormally when a large current flows, the diodes D11 and D12 and the field effect transistors Q11 and Q12 for suppressing the voltage are connected, and the operational amplifiers A11 and A12 are connected to the resistor R11. , R12 are detected to exceed the reference voltages Vr11, Vr12, the field effect transistors Q11, Q12 are turned on, and the information is measured and controlled. Input to 13.

  In the second embodiment, the diodes D11 and D12 having opposite polarities to the parasitic diodes are connected in parallel with the field effect transistors Q11 and Q12, and the voltages at both ends of the resistors R11 and R12 are parasitic. Since the forward voltages of the diodes and the diodes D11 and D12 are suppressed, it is possible to avoid the occurrence of abnormal voltage and to avoid the burning of the resistance for current measurement. Cost can be reduced.

DESCRIPTION OF SYMBOLS 1 Measurement power supply part 2 Battery under test 3 Measurement control part 4 Measurement detection part 5,6 Switching part R1, R2 Current measurement resistance D1 Diode D2 Parasitic diode Q1 Field effect transistor

Claims (2)

A current detection and measurement device that connects a plurality of types of current measurement resistors between a test device and a device under test, and detects or measures a bidirectional current flowing through the device under test using a voltage across the current measurement resistor. In
A field effect transistor that short-circuits both ends of the current measuring resistor connected between the test apparatus and the device under test in an ON state;
A current detection and measurement apparatus comprising: a diode having a polarity in the forward direction opposite to the forward direction of the parasitic diode of the field effect transistor.   A field effect transistor for short-circuiting both ends of each of the resistances other than the minimum resistance among the plurality of types of current measurement resistors, and the forward direction of the parasitic diode of the field effect transistor is opposite The current detection and measurement device according to claim 1, comprising a configuration in which a diode having a forward polarity in a direction is connected in parallel.

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