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Isolation circuit having Hall element and oscilloscope of isolation circuit

A Hall element and isolation circuit technology, applied in instruments, measuring electrical variables, digital variables/waveform display, etc., can solve problems such as raising high frequency, uneven frequency response, complex low frequency path circuit, etc., and achieve high DC accuracy , high voltage isolation, and simple circuit form

Inactive Publication Date: 2014-06-25
RIGOL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0012] 1. Since the secondary side of the transformer uses two windings, as the positive and negative poles of the output differential signal, it is difficult to ensure the same phase of the positive and negative poles, which increases the difficulty of transformer winding
[0013] 2. The linear optocoupler is used as the isolation of the low-frequency path. The delay of the low-frequency path causes the frequency response to be uneven. Circuits 48, 52, 50, and 54 are used to compensate. Because the capacitors are discrete, it is difficult to ensure that the positive and negative poles of the differential signal are completely unanimous
[0024] 2. The delay compensation circuit 103 or 22, 24, 29, 30 mentioned in the patent cannot actually solve the amplitude-frequency sag at the overlapping frequency of the low-frequency and high-frequency paths
Because the capacitors 24 and 30 play a low-pass role in the amplifier circuit shown, they can only make the high frequency of the low frequency path lower than the low frequency, but cannot properly increase the high frequency.
Circuit 103 is actually an RC low-pass circuit, which also cannot properly enhance high frequencies.
[0025] 3. Since the provided delay compensation circuit does not work, the output amplitude-frequency response of the linear isolation circuit is not flat
[0026] 4. The low-frequency path circuit is complex
[0027] To sum up, the main disadvantage of the existing technology is that the bandwidth of the linear isolation circuit that can be realized is low, and the isolation oscilloscope with a larger bandwidth cannot be realized.
Moreover, the frequency response depression problem caused by the linear optocoupler circuit

Method used

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  • Isolation circuit having Hall element and oscilloscope of isolation circuit
  • Isolation circuit having Hall element and oscilloscope of isolation circuit
  • Isolation circuit having Hall element and oscilloscope of isolation circuit

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0104] Figure 10 It is a schematic diagram of the structure of this embodiment. This embodiment is applicable to the application of single-ended signal input and single-ended signal output.

[0105] As shown in the figure, the buffer circuit is specifically a follower circuit composed of an operational amplifier. The buffer circuit U1 meets the bandwidth index of the linear isolation circuit design and needs to amplify the input current to be able to drive the primary winding of the transformer.

[0106] The buffer and the second amplifier can be any high-speed amplifier, as long as it can meet the maximum bandwidth and maximum voltage amplitude required by the design. Of course, choosing a larger bandwidth, low noise, and low distortion amplifier can help realize the design bandwidth requirements. For example, AD8038 and AD8012 of ADI Company.

[0107] In this implementation, the transformer adopts a common transformer winding method, that is, the primary winding and the ...

Embodiment 2

[0112] Figure 11 It is a schematic diagram of the structure of this embodiment.

[0113] The difference between this embodiment and Embodiment 1 is that the transformer is wound in a different way.

[0114] For the transformer in this embodiment, in order to achieve a bandwidth as large as possible, the minimum operating frequency needs to be extended to less than 10 kHz, and the maximum operating frequency should be greater than the designed bandwidth. Moreover, the withstand voltage between the primary line combination and the secondary line group must meet the design expectations. In this embodiment, the transformer winding method adopts the transmission line transformer method, which can achieve better frequency response. Other forms of transformers can also be implemented, but the frequency response is slightly worse.

[0115] The best choice for transformer magnetism is high permeability soft ferrite magnetic ring, such as the R10K series of Beijing Qixing Flying Ele...

Embodiment 3

[0119] Figure 12 It is a schematic structural diagram of this embodiment, which is applied when the input signal is a differential input.

[0120] The difference between this embodiment and Embodiment 1 is that the buffer circuit is a circuit composed of a fully differential amplifier.

[0121] As shown in the figure, the differential signal input is Vin_P and Vin_N, the fully differential amplifier input feedback resistor R1=R2=R3=R4, and the amplifier differential output is used to drive both ends of the primary winding.

[0122] The fully differential operational amplifier needs to meet the bandwidth requirements of the linear isolation circuit design. In this implementation, LMH6554 from TI or ADA4937 from Analog Devices is preferred, and the input and feedback resistors are 300Ω.

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PUM

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Abstract

The invention provides an isolation circuit having a Hall element and can be applied to measuring equipment, e.g., an oscilloscope. The isolation circuit comprises a transformer, the Hall element, a constant current source, a first amplifier and a second amplifier, wherein an input signal is isolated through the transformer, a magnetic core of the transformer is provided with a notch, the notch is provided with the Hall element, the input signal is converted by the transformer into a high-frequency output signal, the Hall element induces magnetic flux of the magnetic core of the transformer to generate a low-frequency feedback signal, and the high-frequency output signal and the low-frequency feedback signal are processed through the second amplifier to generate signals after isolation. As the Hall element and a primary winding are not directly connected physically, the voltage isolation can be determined by the primary winding and a secondary winding of the transformer, the realized isolation is much higher than the isolation in the prior art, and thereby band width of the isolation circuit is greatly expanded.

Description

technical field [0001] The invention relates to electronic measuring equipment, in particular to an isolation circuit with a Hall element and an oscilloscope thereof. Background technique [0002] The isolation circuit can transmit the electrical signal on the input side to the output side, but the input side and the output side are electrically isolated, or insulated, and there is only a small capacitance between the input side and the output side. The isolation circuit can improve the common mode rejection ratio during measurement, reduce interference, improve signal quality, and can also isolate dangerous voltages to protect equipment and personal safety. When multi-channel oscilloscopes measure at the same time, channel isolation can also measure multiple signals with different common-mode voltages to prevent short-circuit accidents caused by common ground between channels. [0003] From the frequency response of the processed signal and the isolation circuit, the isola...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R13/00
Inventor 史慧王悦王铁军李维森
Owner RIGOL
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