A detection circuit for measuring high-frequency inductance copper loss

Abstract

The application relates to the technical field of electric power metering, and discloses a detection circuit for measuring high-frequency inductance copper loss, which comprises an actual inductance physical model composed of an effective inductance L1, an equivalent series resistance R2, an equivalent interlayer parasitic capacitance C2 and a resistance R3 corresponding to equivalent inductance magnetic core loss; a low-pass filter composed of a resistance R4 and a capacitance C3 is connected in parallel across the actual inductance physical model and is used for extracting the direct-current voltage drop of the effective inductance L1; the effective inductance L1 is also connected in series with a shunt; the direct-current voltage drop is sequentially sent to a DSP through a follower M3, a second amplifier M2 and a second first-order low-pass filter; meanwhile, the shunt sends the current of the effective inductance L1 obtained through a first amplifier M1 and a first first-order low-pass filter to the DSP; and the DSP measures the inductance copper loss value according to the sampled signals, so that the precise measurement of the high-frequency inductance copper loss is realized. The circuit has the advantages of simple structure, high measurement precision and suitability for high-frequency inductance loss detection.

Description

Technical Field

[0001] This application relates to the field of power metering technology, and in particular to a detection circuit for measuring copper loss in high-frequency inductors. Background Technology

[0002] Currently, methods for measuring inductor loss mainly include calorimetry, impedance analysis, AC power measurement, DC power measurement, and damped oscillation. While calorimetry and impedance analysis can provide some loss information, they are typically only applicable under specific conditions and cannot fully reflect the inductor's performance in real-world operating environments. For example, impedance analysis can only test the equivalent series resistance (ESR) of an inductor at a specific frequency; however, because ESR is frequency-dependent, the accuracy of this method is limited across multiple frequency ranges. More importantly, the excitation source used in impedance analyzers is generally a sine wave, while in practical applications, inductors are often subjected to more complex excitation signals, such as square waves or pulse waveforms. The rich harmonic components contained in these waveforms often cannot be effectively captured by sine wave excitation methods.

[0003] Furthermore, while existing measurement methods such as the DC power method can account for DC losses, they neglect the influence of AC losses. AC losses are closely related to factors such as the skin effect and proximity effect, which are particularly significant under high-frequency signals. Therefore, a single DC loss test cannot comprehensively evaluate the overall performance of an inductor.

[0004] To address the aforementioned issues, the AC power measurement method, which directly measures the instantaneous voltage and current of an inductor and calculates its losses over a period, has been proposed as a relatively accurate measurement method. This method can accurately reflect the loss characteristics of an inductor in practical applications under real-world conditions. However, the AC power measurement method requires high-bandwidth equipment, which increases its cost. Furthermore, when bandwidth is insufficient, the phase difference between voltage and current can affect measurement accuracy, leading to increased errors. Utility Model Content

[0005] This application aims to address these problems in the prior art by proposing a detection circuit for measuring high-frequency inductor copper loss, which can simultaneously consider both DC and AC losses, and has a high measurement accuracy and low cost inductor loss measurement method.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] This application proposes a detection circuit for measuring the copper loss of a high-frequency inductor, the detection circuit comprising:

[0008] The physical model of the actual inductor consists of the effective inductance L1, the equivalent series resistance R2, the equivalent interlayer parasitic capacitance C2, and the resistance R3 corresponding to the equivalent inductor core loss.

[0009] A low-pass filter consisting of resistor R4 and capacitor C3 is connected in parallel across the actual inductor physical model to extract the DC voltage drop of the effective inductor L1.

[0010] The effective inductance L1 is also connected in series with a shunt;

[0011] The DC voltage drop is sequentially sent to the DSP via follower M3, second amplifier M2, and second first-order low-pass filter; at the same time, the shunt sends the current of the effective inductor L1 obtained by the shunt through first amplifier M1 and first first-order low-pass filter to the DSP.

[0012] The DSP measures the copper loss value of the inductor based on the sampled signal.

[0013] Preferably, the detection circuit further includes:

[0014] The non-inverting input terminal of the first amplifier M1 is connected to one side of the shunt via resistor R13;

[0015] The inverting input terminal of the first amplifier M1 is connected to the other side of the shunt via resistor R8;

[0016] The output of the first amplifier M1 is connected to the DSP through a first-order low-pass filter.

[0017] The non-inverting input terminal of the second amplifier M2 is grounded;

[0018] The inverting input of the second amplifier M2 is connected to one side of the follower M3 through resistor R5;

[0019] The output of the second amplifier M2 is connected to the DSP through a second first-order low-pass filter.

[0020] A resistor R9 and a capacitor C6 are connected in parallel between the inverting input terminal and the output terminal of the first amplifier M1;

[0021] A resistor R6 and a capacitor C4 are connected in parallel between the inverting input and output terminals of the second amplifier M2.

[0022] The inverting input and output terminals of the follower M3 are connected to the resistor R5;

[0023] The non-inverting input terminal of the follower M3 is connected to one end of the isolation capacitor C3.

[0024] The first-order low-pass filter includes a resistor R10 and a capacitor C7;

[0025] The second first-order low-pass filter includes resistor R7 and capacitor C5.

[0026] The resistor R2 is the equivalent internal resistance of the inductor, and is set to 100mΩ;

[0027] The shunt is a resistor R11 with an internal resistance of 1mΩ.

[0028] The amplification factor of the first amplifier M1 is 100.

[0029] The amplification factor of the second amplifier M2 is 1.

[0030] The bandwidth of the first-order low-pass filter and the second-order low-pass filter is one-tenth of the switching frequency.

[0031] Compared with the prior art, this application has the following advantages:

[0032] This application describes a detection circuit for measuring the copper loss of high-frequency inductors. It fully considers the eddy current effect at high frequencies, which plays a crucial role in the copper loss of high-frequency inductors, and its equivalent resistance is much greater than the DC resistance. By introducing an isolation capacitor C3 and a filter circuit into the detection circuit, the measurement results more closely reflect the actual copper loss of the inductor in practical applications, and can more accurately reflect the copper loss of the inductor during operation, especially in high-frequency signal environments. Simultaneously, it employs a simple and efficient circuit structure, including a shunt, operational amplifier, low-pass filter, and DSP processing unit. This results in low circuit cost and ease of implementation. Compared to traditional high-bandwidth, complex measurement equipment, this circuit can achieve high-precision inductor copper loss measurement at a low cost, demonstrating excellent practicality.

[0033] This application also effectively reduces measurement errors caused by signal noise or bandwidth limitations by employing multi-stage filtering and amplification designs, combined with precise calculations by DSP. The inductor's current and voltage signals undergo dual sampling processing, further improving the accuracy of inductor copper loss measurement and enabling accurate calculation of the inductor's actual losses under different operating conditions. By adjusting the BUCK topology, the interference of common-mode voltage on the circuit is reduced, resulting in a more adaptable and stable circuit that can be widely used in practical electronic devices. Attached Figure Description

[0034] Figure 1 This is a detection circuit diagram used to measure the copper loss of a high-frequency inductor in the embodiment.

[0035] Figure 2 The circuit diagram shown in the embodiment is for detection.

[0036] Figure 3 The figure shows the simulation results of psim in the example. Detailed Implementation

[0037] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0038] Reference Figure 1-2 This application proposes a detection circuit for measuring the copper loss of a high-frequency inductor. The key to this application is that, under actual operating conditions, the actual voltage drop of the winding conductor is separated by a low-pass filter, and then the load effect is isolated by a follower M3. The low-pass filter removes ripple and sends the result to the DSP for ADC conversion and calculation to obtain the copper loss.

[0039] Specifically, the detection circuit includes:

[0040] The physical model of the actual inductor consists of the effective inductance L1, the equivalent series resistance R2, the equivalent interlayer parasitic capacitance C2, and the resistance R3 corresponding to the equivalent inductor core loss.

[0041] A low-pass filter consisting of resistor R4 and capacitor C3 is connected in parallel across the actual inductor physical model to extract the DC voltage drop of the effective inductor L1.

[0042] The effective inductance L1 is also connected in series with a shunt;

[0043] The DC voltage drop is sequentially sent to the DSP via follower M3, second amplifier M2, and second first-order low-pass filter; at the same time, the shunt sends the current of the effective inductor L1 obtained by the shunt through first amplifier M1 and first first-order low-pass filter to the DSP.

[0044] The DSP measures the copper loss value of the inductor based on the sampled signal.

[0045] The low-pass filter is used to filter out noise and unnecessary frequency components above the required frequency, ensuring the purity of the signal.

[0046] The inductor under test is connected in parallel with the isolation capacitor C3; the isolation capacitor C3 is connected in parallel with the filter circuit, thereby effectively isolating the equivalent resistance voltage drop portion of the inductor. The purpose is to isolate the copper loss of the inductor (i.e., the loss generated by the equivalent resistance of the inductor) through the capacitor C3, thereby avoiding its interference with subsequent measurement circuits and ensuring the accuracy of signal measurement.

[0047] Unlike traditional BUCK circuits, this topology uses a common positive terminal. The purpose is to place the inductor on the negative terminal, resulting in a low common-mode voltage of the op-amp, allowing the capacitor voltage to be sampled using a standard op-amp.

[0048] In this process, the equivalent resistance voltage drop of the inductor under test is isolated across the isolation capacitor C3. The isolation capacitor C3 passes through the follower M3, the second amplifier M2, and the second first-order low-pass filter in sequence, and inputs the sampling signal to the ADC interface of the DSP. At the same time, the shunt passes the sampled inductor current through the first amplifier M1 and the first first-order low-pass filter, and inputs the sampling signal to the ADC interface of the DSP. The copper loss value of the inductor is measured based on the two sampling signals.

[0049] Preferably, the detection circuit further includes:

[0050] The inductor under test is also connected in parallel with capacitor C2 and resistor R3 to optimize the frequency response of the inductor and suppress high-frequency noise.

[0051] The inductor under test is also connected in series with a resistor R2 to adjust the equivalent resistance of the inductor and further improve the measurement accuracy.

[0052] Preferably, the detection circuit further includes:

[0053] The non-inverting input of the first amplifier M1 is connected to one side of the shunt via resistor R13 to ensure accurate input of the current signal.

[0054] The inverting input terminal of the first amplifier M1 is connected to the other side of the shunt via resistor R8 to amplify the differential input signal and further improve the amplification accuracy of the current signal.

[0055] The output of the first amplifier M1 is connected to the DSP through a first-order low-pass filter, which is used to transmit the amplified signal to the DSP for subsequent digital processing.

[0056] The non-inverting input terminal of the second amplifier M2 is grounded, which ensures that the input signal of the second amplifier M2 is at a reference potential, thus ensuring stability during the amplification process.

[0057] The inverting input of the second amplifier M2 is connected to one side of the follower M3 through resistor R5, so that the signal from the follower M3 can be accurately transmitted to the second amplifier M2 for further amplification.

[0058] The output of the second amplifier M2 is connected to the DSP through a second first-order low-pass filter, so that the amplified signal is input to the DSP for subsequent digital signal processing and analysis.

[0059] A resistor R9 and a capacitor C6 are connected in parallel between the inverting input and output terminals of the first amplifier M1 to form a compensation network, thereby improving the frequency response of the amplifier and reducing signal distortion and noise interference.

[0060] A resistor R6 and a capacitor C4 are connected in parallel between the inverting input and output of the second amplifier M2 to form a compensation network, which optimizes the stability and frequency response of the signal amplification and further improves the circuit performance.

[0061] The inverting input and output terminals of the follower M3 are connected to the resistor R5. Through this connection, the follower M3 can correctly receive and follow the changes in the input signal, thereby ensuring the stability and accurate transmission of the signal.

[0062] The non-inverting input terminal of the follower M3 is connected to one end of the isolation capacitor C3. The isolation capacitor C3 is used to isolate the equivalent resistance voltage drop signal of the inductor and transmit it to the follower M3 to ensure accurate signal acquisition.

[0063] The first-order low-pass filter includes a resistor R10 and a capacitor C7;

[0064] The second first-order low-pass filter includes resistor R7 and capacitor C5.

[0065] The resistor R2 is the equivalent internal resistance of the inductor, set to 100mΩ, which can accurately simulate the internal resistance characteristics of the inductor, thereby improving the accuracy of copper loss measurement.

[0066] The shunt is a resistor R11 with an internal resistance of 1mΩ. By setting a small internal resistance of the shunt, the accuracy of current sampling is ensured, while the influence of internal resistance on the measurement results is reduced.

[0067] The first amplifier M1 has a gain of 100, which can effectively amplify the current signal obtained from the shunt, ensuring high signal gain and accurate processing.

[0068] The second amplifier M2 has a gain of 1, which is used to ensure that the function of the second amplifier M2 is only signal transmission and does not perform excessive amplification, thereby achieving accurate signal amplification and stable output.

[0069] The bandwidth of both the first and second first-order low-pass filters is one-tenth of the switching frequency. This effectively filters out high-frequency noise and unwanted high-frequency signals while retaining the useful components of the signal. This design allows the circuit to focus on the desired signal frequency range, avoiding the influence of high-frequency interference on the measurement results. The first-order low-pass filter, in particular, has a simple implementation and good filtering effect, providing a stable frequency response. Especially in systems with high switching frequencies, it ensures clear transmission of low-frequency signals and removes high-frequency noise.

[0070] Preferably, when designing a BUCK inductor, the maximum inductor current ripple rate under full load should not exceed 0.8. The current ripple rate r is the ratio of the change in current over one cycle to the average inductor current. That is:

[0071] For a BUCK circuit, the average inductor current is equal to the output current Io, i.e., Il = Io.

[0072] The effective value of the inductor current can be derived as follows:

[0073]

[0074] Let the ratio of the effective value to the average value of the inductor current be k.

[0075]

[0076] Since r is no greater than 0.8, then k is no greater than 1.025.

[0077] Therefore, it can be concluded that within the conventional design range, the effective value and average value of the inductor current are almost equal in numerical value, with an error not exceeding (1.025-1)% = 2.5%. This error is acceptable for the calculation of copper losses. Therefore, using the average value instead of the effective value simplifies the design and improves the circuit's anti-interference capability.

[0078] like Figure 2 As shown, R2 is the equivalent internal resistance of the inductor, 100mΩ, and C3 is a DC blocking capacitor. R11 is a shunt with an internal resistance of 1mΩ, and its amplifier gain is 100. The amplifier gain after capacitor C3 is 1. The DSP's calculation of the equivalent internal resistance in this example is:

[0079]

[0080] The DSP's calculation results for copper loss are as follows:

[0081] W loss =10V1·V2

[0082] Furthermore, such as Figure 3 As shown, a psim simulation was performed. Based on the calculation results above, V2 / 10V1 = 1.749 / (10*1.730) = 101.1mΩ, which has a very small error compared to 100mΩ. Therefore, this method can effectively calculate the equivalent resistance of the inductor with very small error.

[0083] As can be seen, this application is based on actual working conditions and fully considers the eddy current effect (the equivalent resistance of the eddy current effect is much greater than the DC resistance at high frequencies), making the results closer to the true values ​​and providing a reliable basis for the heat sink design of the topology.

[0084] Furthermore, this application boasts low cost and high practicality. By adjusting the BUCK topology, the common-mode voltage of the op-amp is significantly reduced. A simple circuit consisting of shunts, resistors, capacitors, operational amplifiers, and a DSP can accurately calculate the equivalent internal resistance of the inductor during operation, and further calculate the copper losses. Replacing the RMS value with the average value greatly simplifies the design. Placing the inductor at the negative terminal reduces the op-amp's common-mode voltage, placing less emphasis on the op-amp's performance. In this case, the BUCK output voltage is 300V; if the inductor were placed at the positive terminal, the op-amp's common-mode voltage would be 300V, rendering a standard op-amp inoperable.

[0085] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in this application, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

Claims

1. A detection circuit for measuring copper loss in high-frequency inductors, characterized in that, The detection circuit includes: The physical model of the actual inductor consists of the effective inductance L1, the equivalent series resistance R2, the equivalent interlayer parasitic capacitance C2, and the resistance R3 corresponding to the equivalent inductor core loss. A low-pass filter consisting of resistor R4 and capacitor C3 is connected in parallel across the actual inductor physical model to extract the DC voltage drop of the effective inductor L1. The effective inductance L1 is also connected in series with a shunt; The DC voltage drop is sequentially sent to the DSP via follower M3, second amplifier M2, and second first-order low-pass filter; at the same time, the shunt sends the current of the effective inductor L1 obtained by the shunt through first amplifier M1 and first first-order low-pass filter to the DSP. The DSP measures the copper loss value of the inductor based on the sampled signal.

2. The detection circuit for measuring high-frequency inductor copper loss according to claim 1, characterized in that, Also includes: The non-inverting input terminal of the first amplifier M1 is connected to one side of the shunt via resistor R13; The inverting input terminal of the first amplifier M1 is connected to the other side of the shunt via resistor R8; The output of the first amplifier M1 is connected to the DSP through a first-order low-pass filter.

3. A detection circuit for measuring high-frequency inductor copper loss according to claim 2, characterized in that, Also includes: The non-inverting input of the second amplifier M2 is grounded; The inverting input of the second amplifier M2 is connected to one side of the follower M3 through resistor R5; The output of the second amplifier M2 is connected to the DSP through a second first-order low-pass filter.

4. A detection circuit for measuring high-frequency inductor copper loss according to claim 3, characterized in that, Also includes: A resistor R9 and a capacitor C6 are connected in parallel between the inverting input terminal and the output terminal of the first amplifier M1; A resistor R6 and a capacitor C4 are connected in parallel between the inverting input and output terminals of the second amplifier M2.

5. A detection circuit for measuring high-frequency inductor copper loss according to claim 4, characterized in that, Also includes: The inverting input and output terminals of the follower M3 are connected to the resistor R5; The non-inverting input terminal of the follower M3 is connected to one end of the isolation capacitor C3.

6. A detection circuit for measuring high-frequency inductor copper loss according to claim 5, characterized in that, Also includes: The first-order low-pass filter includes a resistor R10 and a capacitor C7; The second first-order low-pass filter includes resistor R7 and capacitor C5.

7. A detection circuit for measuring high-frequency inductor copper loss according to claim 6, characterized in that, Also includes: The resistor R2 is the equivalent internal resistance of the inductor, and is set to 100mΩ; The shunt is a resistor R11 with an internal resistance of 1mΩ.

8. A detection circuit for measuring high-frequency inductor copper loss according to claim 7, characterized in that, Also includes: The amplification factor of the first amplifier M1 is 100. The amplification factor of the second amplifier M2 is 1.

9. A detection circuit for measuring high-frequency inductor copper loss according to claim 8, characterized in that, Also includes: The bandwidth of the first-order low-pass filter and the second-order low-pass filter is one-tenth of the switching frequency.

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