Common mode inductor magnetic core characteristic analysis circuit

Abstract

The invention discloses a common mode inductor magnetic core characteristic analysis circuit which comprises a data processing unit, a comparator U1, an inductor L1, a sampling resistor R1, a divider resistor R2 and a divider resistor R3. The inductor L1 is composed of a magnetic core to be measured and a coil, and the sampling resistor R1 is connected to the inductor L1 and used for sampling current flowing through the inductor L1; the reverse input end of the comparator U1 is connected between the sampling resistor R1 and the inductor L1 and used for monitoring current flowing through the inductor LI, and the positive input end of the comparator U1 is connected between the divider resistor R2 and the divider resistor R3. According to the invention, the characteristics of the magnetic core can be analyzed more comprehensively, the magnetic induction intensity of the magnetic core under different magnetic field intensities can be measured accurately, a complete hysteresis loop can be drawn, and the characteristics of the magnetic core can be known more comprehensively.

Description

Technical Field

[0002] The present invention relates to the technical field of electronic circuits, and more particularly to a circuit for analyzing the characteristics of a common-mode inductor core. Background Art

[0003] In the era of rapid development of today's electronic technology, the requirements for the performance and reliability of electronic devices are getting higher and higher. The problem of electromagnetic interference has become one of the key factors affecting the normal operation of electronic devices, and the AC filter plays a crucial role in solving the electromagnetic interference problem. With the development trend of miniaturization, integration and high frequency of electronic devices, the performance requirements for AC filters are also continuously improving. Among them, the common-mode inductor, as an important part of the AC filter, its core characteristics directly affect the filtering effect and stability of the filter. Therefore, the accurate measurement and analysis of the core characteristics of the common-mode inductor have become an important research direction in the electronic field.

[0004] In the prior art, generally, the common-mode inductor core on the AC filter is measured by using the bridge test method, and only the inductance curve of the inductor can be measured, and the data is not complete enough to comprehensively understand the characteristics of the core. This not only limits the optimal design of the common-mode inductor, but also affects the performance improvement of the AC filter. At the same time, the incomplete data will also lead to misjudgment of the core working state, increasing the design risk and cost. Summary of the Invention

[0005] A circuit for analyzing the characteristics of a common-mode inductor core provided by the present invention can at least solve one of the above technical problems.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A circuit for analyzing the characteristics of a common-mode inductor core includes a data processing unit, a comparator U1, an inductor L1, a sampling resistor R1, a voltage-dividing resistor R2, and a voltage-dividing resistor R3; The data processing unit is composed of an ADC and an MCU, and is used for collecting and organizing the voltage on the sampling resistor R1; The inductor L1 is composed of a core to be measured and a coil, and the sampling resistor R1 is connected to the inductor L1 for sampling the current flowing through the inductor L1; The reverse input terminal of the comparator U1 is connected between the sampling resistor R1 and the inductor L1 for monitoring the current flowing through the inductor LI, the forward input terminal of the comparator U1 is connected between the voltage-dividing resistor R2 and the voltage-dividing resistor R3, and both the voltage-dividing resistor R2 and the voltage-dividing resistor R3 are used for voltage-dividing and sampling the output voltage of the output terminal of the comparator U1, and sending the voltage-divided output voltage to the forward input terminal of the comparator U1 to compare with the voltage at the reverse input terminal of the comparator U1.

[0007] Furthermore, the comparator U1 has a current output capability, and the power supply of the comparator U1 is a dual-polarity power supply.

[0008] Furthermore, the output terminal of the comparator U1 is sequentially connected to the inductor L1 and the sampling resistor R1 for exciting the measured inductor L1.

[0009] Furthermore, the comparator U1 compares the output voltage after voltage division and the voltage at the inverting input terminal to determine whether the measured inductor L1 is in a saturated state. If the inductor L1 is in a saturated state, the comparator U1 is inverted to reverse the voltage polarity on the inductor L1, thereby demagnetizing the magnetic core to be measured in the inductor L1 and performing the next round of magnetization.

[0010] Furthermore, the voltage across the sampling resistor R1 is directly proportional to the current flowing through the inductor L1.

[0011] The beneficial effects of the present invention are as follows: The circuit structure provided by the present invention can achieve a more comprehensive analysis of the magnetic core characteristics, accurately measure the magnetic induction intensity of the magnetic core under different magnetic field strengths, thereby drawing a complete hysteresis loop, and can more comprehensively understand the characteristics of the magnetic core, such as saturation magnetic induction intensity, coercive force, etc. The complete hysteresis loop data provides more key information for the design of the common-mode inductor. Designers can more accurately select appropriate magnetic core materials and sizes according to these data, optimize the structure of the common-mode inductor, improve the filtering effect and stability of the AC filter. At the same time, it can also reduce the design risk and cost, and improve the reliability and market competitiveness of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application.

[0013] Figure 1 is a schematic diagram of the circuit structure for analyzing the magnetic core characteristics of the common-mode inductor according to an embodiment of the present invention.

[0014] Figure 2 is a schematic diagram of the circuit structure for analyzing the magnetic core characteristics of the common-mode inductor according to an embodiment of the present invention when the output voltage of the comparator is positive.

[0015] Figure 3 is a schematic diagram of the circuit structure for analyzing the magnetic core characteristics of the common-mode inductor according to an embodiment of the present invention when the output voltage of the comparator is negative.

[0016] Figure 4 is a simulation circuit diagram for analyzing the magnetic core characteristics of the common-mode inductor according to an embodiment of the present invention.

[0017] Figure 5 It is a simulation diagram of the current data of the inductor to be measured in the common-mode inductor core characteristic analysis simulation circuit of the embodiment of the present invention.

[0018] Figure 6 It is a relationship diagram between the magnetic field strength H and the magnetic induction intensity B of the core in the common-mode inductor core characteristic analysis simulation circuit of the embodiment of the present invention.

[0019] Figure 7 It is a structural block diagram of the computer device of the embodiment of the present invention. Specific embodiments

[0020] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] It should be noted that the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions conflicts or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0022] All the electronic components in the present invention are selected as standard components or modified components obtained through purchase in the prior art, such as ADC or MCU, etc. The model is not specifically limited, and the main consideration is the function implementation.

[0023] The common-mode inductor is also called a common-mode choke coil, which is a common-mode interference suppression device with a core made of ferrite or the like. It presents a large inductance to the common-mode signal and plays a suppression role, while presenting a small inductance to the differential-mode signal and having almost no influence. The common-mode inductor is usually used in the power filter of electronic devices to reduce electromagnetic interference.

[0024] The core is the core component of the common-mode inductor, generally made of magnetic materials such as ferrite and iron powder core. The role of the core is to enhance the magnetic field strength of the inductor and increase the inductance. Different types of cores have different characteristics such as magnetic permeability, saturation magnetic flux density, and loss.

[0025] See Figure 1 , the embodiment of the present invention provides a common-mode inductor core characteristic analysis circuit, including a data processing unit, a comparator U1, an inductor L1, a sampling resistor R1, a voltage-dividing resistor R2, and a voltage-dividing resistor R3; The data processing unit consists of an ADC and an MCU, and is used to collect and organize the voltage on the sampling resistor R1. The inductor L1 consists of a core under test and a coil. The sampling resistor R1 is connected to the inductor L1 and is used to sample the current flowing through the inductor L1. The inverting input terminal of the comparator U1 is connected between the sampling resistor R1 and the inductor L1, and is used to monitor the current flowing through the inductor LI. The non-inverting input terminal of the comparator U1 is connected between the voltage-dividing resistor R2 and the voltage-dividing resistor R3. Both the voltage-dividing resistor R2 and the voltage-dividing resistor R3 are used to divide and sample the output voltage of the output terminal of the comparator U1, and the divided output voltage is sent to the non-inverting input terminal of the comparator U1 to be compared with the voltage at the inverting input terminal of the comparator U1.

[0026] In this embodiment, the comparator U1 has a current output capability, and the power supply of the comparator U1 is a dual-polarity power supply.

[0027] In this embodiment, the output terminal of the comparator U1 is sequentially connected to the inductor L1 and the sampling resistor R1, and is used to excite the inductor L1 under test.

[0028] In this embodiment, the comparator U1 compares the divided output voltage and the voltage at the inverting input terminal to determine whether the inductor L1 under test is in a saturated state. If the inductor L1 is in a saturated state, the comparator U1 reverses to make the voltage polarity on the inductor L1 opposite, so as to demagnetize the core under test in the inductor L1 and perform the next round of magnetization.

[0029] In this embodiment, the voltage on the sampling resistor R1 is directly proportional to the current flowing through the inductor L1.

[0030] The operation of this common-mode inductor core characteristic analysis circuit is divided into two states. Assume that the supply voltage of the comparator U1 is ±5V: State 1, as Figure 2 shown, the output voltage of the comparator U1 is positive: The output voltage of the comparator U1 is 5V. The resistance values of the voltage-dividing resistors R2 and R3 are equal. Therefore, the voltage between the voltage-dividing resistor R2 and the voltage-dividing resistor R3 is 2.5V, that is, the voltage at the non-inverting input terminal of the comparator U1 is 2.5V. The output of the comparator U1 is simultaneously applied to the network formed by the series connection of the inductor L1 and the sampling resistor R1. At this time, the current in the inductor L1 begins to increase. Since the voltage across the sampling resistor R1 is positively correlated with the current flowing through the inductor L1, the voltage across the sampling resistor R1 also begins to increase. At the same time, the voltage across the sampling resistor R1 is collected by the inverting input terminal of the comparator U1. Therefore, the voltage at the inverting input terminal of the comparator U1 is: I L1 *R1. When the current flowing through the inductor L1 gradually increases and saturates, assuming the saturation current of the inductor L1 is I sat , adjust the resistance value of the sampling resistor R1 so that I sat *R1 > 2.5V. Then, at this time, the comparator U1 will reverse.

[0031] State 2: As Figure 3 shown, the output voltage of the comparator U1 is negative: The output voltage of the comparator U1 is -5V. The resistance values of the voltage-dividing resistors R2 and R3 are equal. Therefore, the voltage between the voltage-dividing resistor R2 and the voltage-dividing resistor R3 is -2.5V, that is, the voltage at the non-inverting input terminal of the comparator U1 is -2.5V. The output of the comparator U1 is simultaneously applied to the network formed by the series connection of the inductor L1 and the sampling resistor R1. At this time, the current in the inductor L1 first decreases and then increases. Since the voltage across the sampling resistor R1 is positively correlated with the current flowing through the inductor L1, the voltage across the sampling resistor R1 also first decreases and then increases. At the same time, the voltage across the sampling resistor R1 is collected by the inverting input terminal of the comparator U1. Therefore, the voltage at the inverting input terminal of the comparator U1 is: I L1 *R1. When the current flowing through the inductor L1 gradually increases and saturates, assuming the saturation current of the inductor L1 is I sat , adjust the resistance value of the sampling resistor R1 so that I sat *R1 < -2.5V. Then, at this time, the comparator U1 will reverse.

[0032] During the entire working process of the above circuit, the voltage across the sampling resistor R1 fully reflects the current in the inductor L1. The current in the inductor L1 in turn reflects the magnetic field intensity, thereby reflecting the characteristics of the magnetic core to be measured. Therefore, according to the change in the voltage across the sampling resistor R1, the corresponding hysteresis loop of the magnetic core to be measured can be plotted.

[0033] The abscissa of the hysteresis loop is the magnetic field strength H. According to Ampere's circuital law, the relationship between the current flowing through the inductor L1 and the magnetic field strength inside the magnetic core to be measured is as follows:

[0034] Among them, N is the number of turns of the coil on the inductor L1, which is a known condition, and the current I is the collected data. Therefore, the average magnetic field strength in the magnetic core of the inductor L1 to be measured can be calculated. ; According to Faraday's law of electromagnetic induction:

[0035] Among them, U is the voltage applied to the inductor L1, which is the output voltage of the comparator U1 minus the voltage on the sampling resistor R1. S is the cross-sectional area of the magnetic core to be measured, which is a known condition. Therefore, the magnetic induction intensity B can be calculated. In summary, the relationship between the magnetic field strength H and the magnetic induction intensity B can be obtained, that is, the hysteresis loop of the magnetic material can be obtained.

[0036] Next, the present invention will further explain this circuit in combination with a simulation case: The simulation circuit diagram is as Figure 4 shown. Among them, for the inductor L1 to be measured, the following parameters can be obtained through the above calculation method: Hc = 12, Bs = 0.51, Br =.117, A = 0.0004, N = 20, Lm = 0.05 Among them: Hc is the coercive force, which represents the ability of the material to resist demagnetization. The larger the value, the stronger the demagnetization resistance ability, and the unit is A / m (ampere per meter); Bs is the saturation magnetic induction intensity, which represents the maximum magnetic induction intensity that the material can reach under a strong magnetic field, and the unit is T (tesla); Br is the residual magnetic induction intensity, which represents the magnetic induction intensity retained in the material after removing the external magnetic field, and the unit is T (tesla); A is the cross-sectional area, which represents the effective cross-sectional area of the magnetic circuit or magnetic core, affects the magnetic flux, and the unit is m² (square meter); N is the number of turns, which represents the total number of turns of the coil winding and directly affects the magnetic field strength; Lm is the magnetic path length, which represents the average length of the closed path of the magnetic force line in the magnetic core, affects the magnetic resistance, and the unit is m (meter).

[0037] According to the above parameters, the hysteresis loop of the magnetic core of the inductor L1 to be measured is defined, and at the same time, the properties of the inductor L1 to be measured are defined; According to the current on the inductor L1 to be measured collected by this simulation circuit, as Figure 5As shown, the relationship between the magnetic field strength H and the magnetic induction intensity B is obtained by processing and calculating its data as Figure 6 As shown, it can be seen that the theoretical value and the calculated value are almost the same, which proves that this circuit method is practical and feasible.

[0038] See Figure 7 , the embodiment of the present invention further provides a computer device, including a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor implements the common-mode inductor core characteristic analysis circuit of the present invention.

[0039] It should be noted that those of ordinary skill in the art can understand that all or part of the steps implemented in the embodiments of the present invention can be fully or partially implemented by software, hardware, firmware, or any combination thereof. When implemented using hardware, it can be fully or partially implemented in the form of purchasing standard parts or modified parts. When implemented using software, it can be fully or partially implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that the computer can access or a data storage device such as a server or data center that includes one or more integrated available media. The available medium can be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium (for example, a solid-state drive Solid State Disk (SSD)), etc.

[0040] In summary, the key technical problem that this invention endeavors to solve is to obtain a complete magnetic core hysteresis loop. Prior to this, traditional methods often could only measure the inductance curve, and the data obtained had obvious deficiencies and was incomplete. The circuit structure provided by this invention can achieve a more comprehensive analysis of the magnetic core characteristics, accurately measure the magnetic induction intensity of the magnetic core under different magnetic field strengths, thereby draw a complete hysteresis loop, and can more comprehensively understand the characteristics of the magnetic core, such as saturation magnetic induction intensity, coercive force, etc. The complete hysteresis loop data provides more key information for the design of common mode inductors. Designers can more accurately select appropriate magnetic core materials and sizes based on this data, optimize the structure of common mode inductors, improve the filtering effect and stability of AC filters. At the same time, it can also reduce design risks and costs, and improve the reliability and market competitiveness of products.

[0041] It should be understood that the examples and embodiments described herein are only for illustration and are not intended to limit the present invention. Those skilled in the art can make various modifications or changes according to it. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A common mode inductor core characteristic analysis circuit, characterized in that: It includes a data processing unit, a comparator U1, an inductor L1, a sampling resistor R1, a voltage dividing resistor R2 and a voltage dividing resistor R3; The data processing unit is composed of an ADC and an MCU, and is used to collect and sort out the voltage on the sampling resistor R1; The inductor L1 is composed of a magnetic core to be measured and a coil, and the sampling resistor R1 is connected to the inductor L1 to sample the current flowing through the inductor L1; The reverse input terminal of the comparator U1 is connected between the sampling resistor R1 and the inductor L1 to monitor the current flowing through the inductor L1. The forward input terminal of the comparator U1 is connected between the voltage-dividing resistor R2 and the voltage-dividing resistor R3. The voltage-dividing resistor R2 and the voltage-dividing resistor R3 are both used to divide and sample the output voltage of the output terminal of the comparator U1, and input the divided output voltage to the forward input terminal of the comparator U1 to compare with the voltage at the reverse input terminal of the comparator U1.

2. The common mode inductor core characteristic analysis circuit according to claim 1, characterized in that: The comparator U1 has current output capability, and the comparator U1 is powered by positive and negative power supplies.

3. The common mode inductor core characteristic analysis circuit according to claim 1, characterized in that: The output end of the comparator U1 is connected to the inductor L1 and the sampling resistor R1 in sequence, so as to excite the inductor L1 to be measured.

4. The common mode inductor core characteristic analysis circuit according to claim 1, characterized in that: The comparator U1 compares the divided output voltage and the voltage at the reverse input terminal to determine whether the inductor L1 currently being measured is in a saturated state. If the inductor L1 is in a saturated state, the comparator U1 is reversed to make the voltage polarity on the inductor L1 opposite, thereby demagnetizing the magnetic core to be measured in the inductor L1 and performing the next round of magnetization.

5. The common mode inductor core characteristic analysis circuit according to claim 1, characterized in that: The voltage on the sampling resistor R1 is directly proportional to the current flowing through the inductor L1 .

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