A device and method for measuring broadband characteristics of common mode inductors under DC bias

Abstract

The present invention relates to a device and method for measuring broadband characteristics of common-mode inductance under direct current bias. The measuring device comprises a direct current power supply, an inductor, a first direct current blocking capacitor, a second direct current blocking capacitor, a common-mode inductor to be measured and an impedance measuring device. The positive terminal of the direct current power supply is connected to one end of the inductor, and the other end of the inductor is divided into two paths, one of which is connected to the first connection end of the first winding of the common-mode inductor to be measured, and the other is connected to the first connection end of the impedance measuring device via the first direct current blocking capacitor; the negative terminal of the direct current power supply is divided into two paths, one of which is connected to the first connection end of the second winding of the common-mode inductor to be measured, and the other is connected to the first connection end of the impedance measuring device via the second direct current blocking capacitor; the second connection end of the first winding and the second connection end of the second winding are short-circuited and connected to the second connection end of the impedance measuring device. The measuring device and method are conducive to improving the accuracy and safety of measurement.

Description

Technical Field

[0001] The invention belongs to the field of electrical equipment, and in particular relates to a device and method for measuring broadband characteristics of common-mode inductance under direct current bias. Background Art

[0002] Common-mode inductors are commonly used filter components in electrical equipment to suppress electromagnetic interference in circuits. Impedance characteristics are an important basis for evaluating their electromagnetic interference suppression capabilities. Accurate and reasonable impedance characteristic measurements are important guarantees for common-mode inductor performance evaluation, parameter design, and circuit modeling. Traditional common-mode inductor impedance characteristic measurements are static measurements that are divorced from actual working conditions and do not apply bias current. Common-mode inductors are subject to DC bias current when the circuit is working. The presence of DC bias will change the relative magnetic permeability of the common-mode inductor and affect the impedance characteristics. Therefore, the impedance characteristic measurement results without bias cannot accurately reflect the noise suppression capability of the common-mode inductor in the actual circuit.

[0003] The prior art discloses a biased single-ended measurement method, such as Figure 1 As shown, this method uses a DC power supply to provide a DC bias current, and uses an impedance measurement device to measure the impedance of the common-mode inductor with a bias current. Due to the asymmetry of the circuit, the impedance measurement result will include the impedance of the bias power supply and the inductor, affecting the accuracy of the measurement result. At the same time, an ideal DC power supply is difficult to obtain, and the DC output of the test often contains a certain AC component. The existence of the DC blocking capacitor can only isolate the DC voltage but has no way to isolate the AC voltage, so there will be a certain AC voltage on the measurement port, which will interfere with the accuracy of the impedance measurement device and even further cause damage to the measuring instrument. Due to the poor symmetry of the measurement circuit, the biased single-ended measurement will make the AC voltage on the measurement port larger. Summary of the invention

[0004] The object of the present invention is to provide a device and method for measuring broadband characteristics of common-mode inductance under direct current bias, which are conducive to improving the accuracy and safety of measurement.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a device for measuring the broadband characteristics of common-mode inductance under DC bias, comprising a DC power supply, an inductor, a first DC blocking capacitor, a second DC blocking capacitor, a common-mode inductor to be measured and an impedance measuring device, wherein the positive terminal of the DC power supply is connected to one end of the inductor, and the other end of the inductor is divided into two paths, one of which is connected to the first connection end of the first winding of the common-mode inductor to be measured, and the other is connected to the first connection end of the impedance measuring device via the first DC blocking capacitor; the negative terminal of the DC power supply is divided into two paths, one of which is connected to the first connection end of the second winding of the common-mode inductor to be measured, and the other is connected to the first connection end of the impedance measuring device via the second DC blocking capacitor; the second connection end of the first winding and the second connection end of the second winding are short-circuited and connected to the second connection end of the impedance measuring device.

[0006] Furthermore, the first DC blocking capacitor and the second DC blocking capacitor are used to isolate the DC flow on the measurement port, the first DC blocking capacitor and the second DC blocking capacitor have the same impedance characteristics within the measurement frequency band, and the impedance of the DC blocking capacitor is much smaller than the impedance of the common mode inductor to be measured within the test frequency band.

[0007] Furthermore, the first DC blocking capacitor, the second DC blocking capacitor and the common mode inductor form a balanced bridge for removing the impedance error introduced by the DC power supply and the inductor, and reducing the AC voltage of the measurement port caused by the imperfect DC power supply.

[0008] Furthermore, the DC power supply is a voltage source or a current source.

[0009] Furthermore, the inductor is used to increase the impedance of the bias loop and reduce the AC ripple caused by an imperfect DC power supply.

[0010] Furthermore, the measuring device is equipped with an oscilloscope, which is used to connect to the measurement port before accessing the impedance measuring device, and to trigger the measurement port voltage once to determine whether the measurement state is safe for the impedance measuring device.

[0011] The present invention also provides a method for measuring the broadband characteristics of common-mode inductance under DC bias, comprising the following steps:

[0012] 1) Connect a DC power supply to the inductor and the common-mode inductor to be measured, and make sure that the circuit works normally under bias. After making sure that the circuit works normally, disconnect the power supply;

[0013] 2) Connect the first DC blocking capacitor and the second DC blocking capacitor to the circuit;

[0014] 3) Connect the impedance measurement device to the measurement port, measure the broadband characteristics of the common-mode inductor to be measured when the DC power supply is open, and measure the broadband characteristics of the common-mode inductor to be measured when the DC power supply is turned on but there is no output, and compare the two results to see if they are within the allowable error range;

[0015] 4) Connect the measurement port to an oscilloscope, turn on the DC power supply to bias the circuit, use the oscilloscope for a single trigger, check the AC voltage at the measurement port, and evaluate whether it is safe to use the impedance measurement device for measurement;

[0016] 5) After determining that the trigger AC voltage at the measurement port meets the measurement safety standard, remove the oscilloscope from the measurement circuit;

[0017] 6) Connect the impedance measurement device to the measurement port and measure the broadband characteristics under the common mode inductor bias state.

[0018] Compared with the prior art, the present invention has the following beneficial effects: compared with single-ended measurement under bias, the measurement circuit of the device and method is more symmetrical, and two capacitors and a common-mode inductor form a balanced bridge, which can remove the errors caused by the DC power supply and the inductor impedance, making the measurement result more accurate. In addition, since the measurement circuit is more symmetrical, the AC voltage on the measurement port is smaller, the interference to the internal measurement circuit of the impedance device is smaller, thereby improving the accuracy of the measurement, and the damage to the impedance measurement device is also smaller, and it is less likely to damage the measurement device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of a biased single-ended measurement device in the prior art.

[0020] Figure 2 Schematic diagram of a measuring device according to an embodiment of the present invention.

[0021] Figure 3 It is a circuit connection diagram of the first step in the measurement method of an embodiment of the present invention.

[0022] Figure 4 It is a circuit connection diagram of the second step in the measuring method of an embodiment of the present invention.

[0023] Figure 5 It is a circuit connection diagram of the third step in the measuring method of an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0027] like Figure 2 As shown, this embodiment provides a device for measuring the broadband characteristics of common-mode inductance under DC bias, including a DC power supply, an inductor, a first DC blocking capacitor, a second DC blocking capacitor, a common-mode inductor to be measured and an impedance measuring device, wherein the positive terminal of the DC power supply is connected to one end of the inductor, and the other end of the inductor is divided into two paths, one path is connected to the first connection end of the first winding of the common-mode inductor to be measured, and the other path is connected to the first connection end of the impedance measuring device via the first DC blocking capacitor; the negative terminal of the DC power supply is divided into two paths, one path is connected to the first connection end of the second winding of the common-mode inductor to be measured, and the other path is connected to the first connection end of the impedance measuring device via the second DC blocking capacitor; the second connection end of the first winding and the second connection end of the second winding are short-circuited and connected to the second connection end of the impedance measuring device.

[0028] Wherein, the DC power supply provides a DC current bias for the common-mode inductor to be measured. The inductor has a certain inductance to suppress AC ripple and possible disturbances in the measurement circuit. The first DC blocking capacitor and the second DC blocking capacitor isolate the DC flow on the measurement port. The first DC blocking capacitor and the second DC blocking capacitor have the same impedance characteristics within the measurement frequency band, and the impedance of the DC blocking capacitor is much smaller than the impedance of the common-mode inductor to be measured within the test frequency band. Wherein, the impedance of the DC blocking capacitor is much smaller than the impedance of the common-mode inductor to be measured, which means that the capacitor impedance is more than two orders of magnitude smaller than the impedance of the common-mode inductor to be measured.

[0029] The first DC blocking capacitor, the second DC blocking capacitor and the common mode inductor form a balanced bridge for removing the impedance error introduced by the DC power supply and the inductor, and reducing the AC voltage of the measurement port caused by the imperfect DC power supply.

[0030] The DC power source used in the measurement device can be a voltage source or a current source.

[0031] The inductor is used to increase the impedance of the bias loop and reduce the AC ripple caused by the non-ideal DC power supply.

[0032] In this embodiment, the measuring device is equipped with an oscilloscope (including a probe), which is used to determine whether the impedance measurement is safe for the impedance measuring device under the measurement environment. The oscilloscope is connected to the measurement port before being connected to the impedance measuring device to check whether the voltage at the measurement port is safe.

[0033] This embodiment also provides a method for measuring the broadband characteristics of common-mode inductance under DC bias based on the above-mentioned measuring device, comprising the following steps:

[0034] 1) If Figure 3 As shown, connect a DC power supply to the inductor and the common-mode inductor to be measured to confirm that the circuit works normally under bias conditions. After confirming that the circuit works normally, disconnect the power supply.

[0035] 2) If Figure 4 As shown, the first DC blocking capacitor and the second DC blocking capacitor are connected to the circuit.

[0036] 3) If Figure 2 As shown, connect the impedance measurement device to the measurement port, measure the broadband characteristics of the common-mode inductor to be measured when the DC power supply is open, and measure the broadband characteristics of the common-mode inductor to be measured when the DC power supply is turned on but there is no output, and compare whether the two results are within the allowable error range;

[0037] 4) If Figure 5 As shown, disconnect the measuring device from the port and connect it to an oscilloscope. Turn on the DC power supply to apply a DC bias to the circuit. Use the oscilloscope to single-trigger and measure the AC voltage of the port to determine whether it is safe to use the impedance measuring device on the port.

[0038] 5) After determining that the trigger AC voltage at the measurement port meets the measurement safety standard, remove the oscilloscope from the measurement circuit.

[0039] 6) If Figure 2 As shown, the impedance measurement device is connected to the measurement port to measure the broadband characteristics under the common mode inductor bias state.

[0040] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A device for measuring broadband characteristics of common-mode inductance under DC bias, characterized in that: It comprises a direct current power supply, an inductor, a first direct current blocking capacitor, a second direct current blocking capacitor, a common mode inductor to be measured and an impedance measuring device, wherein the positive terminal of the direct current power supply is connected to one end of the inductor, and the other end of the inductor is divided into two paths, one of which is connected to the first connection end of the first winding of the common mode inductor to be measured, and the other is connected to the first connection end of the impedance measuring device via the first direct current blocking capacitor; the negative terminal of the direct current power supply is divided into two paths, one of which is connected to the first connection end of the second winding of the common mode inductor to be measured, and the other is connected to the first connection end of the impedance measuring device via the second direct current blocking capacitor; the second connection end of the first winding and the second connection end of the second winding are short-circuited and connected to the second connection end of the impedance measuring device; The first DC blocking capacitor and the second DC blocking capacitor are used to isolate the DC flow on the measuring port, the first DC blocking capacitor and the second DC blocking capacitor have the same impedance characteristics within the measuring frequency band, and the impedance of the DC blocking capacitor is much smaller than the impedance of the common mode inductor to be measured within the testing frequency band; The first DC blocking capacitor, the second DC blocking capacitor and the inductor form a balanced bridge for removing the impedance error introduced by the DC power supply and the inductor, and reducing the AC voltage at the measurement port caused by an imperfect DC power supply.

2. The device for measuring broadband characteristics of common mode inductance under DC bias according to claim 1, characterized in that: The DC power source is a voltage source or a current source.

3. The device for measuring broadband characteristics of common mode inductance under DC bias according to claim 1, characterized in that: The inductor is used to increase the impedance of the bias loop and reduce the AC ripple caused by the non-ideal DC power supply.

4. The device for measuring broadband characteristics of common mode inductance under DC bias according to claim 1, characterized in that: The measuring device is equipped with an oscilloscope, which is used to connect the measuring port before accessing the impedance measuring device, and to trigger the measuring port voltage once to determine whether the measuring state is safe for the impedance measuring device.

5. A method for measuring the broadband characteristics of common mode inductance under DC bias based on the measuring device according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) Connect a DC power supply to the inductor and the common-mode inductor to be measured, and make sure that the circuit works normally under bias. After making sure that the circuit works normally, disconnect the power supply; 2) Connect the first DC blocking capacitor and the second DC blocking capacitor to the circuit; 3) Connect the impedance measurement device to the measurement port, measure the broadband characteristics of the common-mode inductor to be measured when the DC power supply is open, and measure the broadband characteristics of the common-mode inductor to be measured when the DC power supply is turned on but there is no output, and compare the two results to see if they are within the allowable error range; 4) Connect the measurement port to an oscilloscope, turn on the DC power supply to bias the circuit, use the oscilloscope for a single trigger, check the AC voltage at the measurement port, and evaluate whether it is safe to use the impedance measurement device for measurement; 5) After determining that the trigger AC voltage at the measurement port meets the measurement safety standard, remove the oscilloscope from the measurement circuit; 6) Connect the impedance measurement device to the measurement port and measure the broadband characteristics under the common mode inductor bias state.

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