阅读说明：本技术 基于频域的改善电源噪声的方法 (Method for improving power supply noise based on frequency domain ) 是由 郑夏威 张利强 熊伟 裘水军 裴敏 梁接明 于 2019-10-16 设计创作，主要内容包括：本发明公开了基于频域的改善电源噪声的方法,包括以下步骤：确定板极电源网络上电源噪声超标的芯片；设置示波器的采样率和存储深度；保存噪声测试波形为数据格式；对数据格式的波形文件进行离散傅里叶变换,得到电压噪声的频谱分布；提取PCB电源网络的S参数文件,得到频域阻抗曲线；计算电源网络的电流噪声频谱分布；根据电压噪声频谱分布曲线和电流噪声频谱分布曲线,找到频谱分布的峰频点；确定对应滤波效果最佳的电容容值；在EDA软件界面下增加或替换最佳的电容容值。本发明通过分析电压噪声和电流噪声的频谱分布,能精准的确定所需增加或替换的滤波电容的容值,同时通过仿真手段能快速高效的确定电容数量和最佳位置。(The invention discloses a method for improving power supply noise based on a frequency domain, which comprises the following steps: determining a chip with power supply noise exceeding the standard on a plate power supply network; setting the sampling rate and the storage depth of the oscilloscope; saving the noise test waveform as a data format; performing discrete Fourier transform on the waveform file in the data format to obtain the frequency spectrum distribution of voltage noise; extracting an S parameter file of a PCB power supply network to obtain a frequency domain impedance curve; calculating the current noise frequency spectrum distribution of the power supply network; finding out the peak frequency points of the frequency spectrum distribution according to the voltage noise frequency spectrum distribution curve and the current noise frequency spectrum distribution curve; determining a capacitance value of the capacitor with the optimal corresponding filtering effect; the optimal capacitance value of the capacitor is added or replaced under the EDA software interface. The invention can accurately determine the capacitance value of the filter capacitor to be added or replaced by analyzing the frequency spectrum distribution of the voltage noise and the current noise, and can quickly and efficiently determine the capacitance quantity and the optimal position by a simulation means.)

1. The method for improving the power supply noise based on the frequency domain is characterized by comprising the following steps:

s10, determining a chip with power supply noise exceeding standard on the plate power supply network;

s20, setting the sampling rate and the storage depth of the oscilloscope;

s30, saving the noise test waveform as a data format;

s40, performing discrete Fourier transform on the waveform file in the data format to obtain the frequency spectrum distribution of the voltage noise;

s50, extracting an S parameter file of the PCB power supply network by using EDA software to obtain a frequency domain impedance curve;

s60, calculating the current noise spectrum distribution of the power supply network by using the frequency domain formula i (f) ═ (u (f))/(z (f));

s70, finding the peak frequency points of the frequency spectrum distribution according to the voltage noise frequency spectrum distribution curve and the current noise frequency spectrum distribution curve;

s80, determining a capacitance value with the best corresponding filtering effect according to the found frequency spectrum peak frequency points;

s90, adding or replacing the optimal capacitance value of the capacitor under the EDA software interface, and extracting the corresponding plate S parameter;

s100, performing inverse Fourier transform on the power supply current noise frequency spectrum obtained in the S60 to obtain a time domain current noise file;

s110, building a simulation link in the ADS of the EDA software, and simulating to obtain the time domain voltage noise with the capacitance added or replaced;

and S120, obtaining an optimal improvement scheme through simulation, welding the optimal improvement scheme on a PCB to perform actual measurement verification, and finishing the improvement of the power supply noise after the verification is qualified.

2. The method for improving power noise based on frequency domain according to claim 1, wherein the chip for determining the power noise exceeding the standard on the plate power network is a chip for determining the exceeding standard by testing the power noise between the power supply and the ground pin of each load chip with an oscilloscope, and comparing the power noise with the requirements of a chip manual.

3. The method for improving power supply noise based on frequency domain according to claim 1, wherein the oscilloscope is set with a sampling rate, which is denoted as X, and a value equal to or higher than the maximum frequency of the power supply noise, and the sampling rate is set in S/S, that is, one point is sampled per second.

4. The method for improving power supply noise based on frequency domain according to claim 3, wherein the storage depth of the oscilloscope is set, the storage depth is recorded as L, the number of sampling points stored when the waveform is stored for the oscilloscope is represented by S, L > -X/Y, and Y is the lowest frequency of the power supply noise spectrum.

5. The frequency domain based method of improving power supply noise according to claim 1, wherein the EDA software comprises POWERSI or OPI.

6. The method for improving power noise based on frequency domain according to claim 1, wherein the determining the corresponding relationship of capacitance capacity value with best filtering effect according to the found frequency spectrum peak frequency point comprises that the energy peaks of current noise spectrum and voltage noise spectrum are at 30KHz, 60KHz, 95KHz, 140KHz and 1MHz, the best filtering capacitance capacity value with noise corresponding to 30KHz-140KHz is 220uF, and the best filtering capacitance capacity value with noise corresponding to 1MHz is 10 uF.

Technical Field

The invention belongs to the field of electronic circuits, and particularly relates to a method for improving power supply noise based on a frequency domain.

Background

In the practical application of a PCB (Printed Circuit Board), the voltage of a power supply is not constant, and voltage fluctuation, called power supply noise, is generated due to factors such as the Circuit design of the PCB, the current change of a load chip, and the like. The power supply noise is reduced by connecting capacitors in parallel to the board level power supply network, which is called power supply filtering.

Aiming at the problem that the power supply noise on the PCB exceeds the standard, the conventional solution has two methods, one method is to try to weld (increase or replace) different capacitance values and different quantities of capacitors at different positions of the PCB and actually measure whether the power supply noise is improved or not until the power supply noise meets the requirement; and the other is to record the capacitance value and position of the newly added or replaced capacitor, and fall to the ground in a schematic diagram and a PCB design file when the version is changed. The capacitors with different capacitance values are only effective to the noise of a specific frequency band, and the effective frequency band can change along with different placement positions, so that the capacitance values, the number and the positions of the capacitors need to be traversed in the conventional method, pertinence is lacked, and the workload is huge; the effectiveness depends mainly on the experience of engineers and is not reproducible.

Disclosure of Invention

In view of the above technical problems, the present invention provides a method for improving power supply noise based on frequency domain, comprising the steps of:

s10, determining a chip with power supply noise exceeding standard on the plate power supply network;

s20, setting the sampling rate and the storage depth of the oscilloscope;

s30, saving the noise test waveform as a data format;

s40, performing discrete Fourier transform on the waveform file in the data format to obtain the frequency spectrum distribution of the voltage noise;

s50, extracting an S parameter file of the PCB power supply network by using EDA software to obtain a frequency domain impedance curve;

s60, calculating the current noise spectrum distribution of the power supply network by using the frequency domain formula i (f) ═ (u (f))/(z (f));

s70, finding the peak frequency points of the frequency spectrum distribution according to the voltage noise frequency spectrum distribution curve and the current noise frequency spectrum distribution curve;

s80, determining a capacitance value with the best corresponding filtering effect according to the found frequency spectrum peak frequency points;

s90, adding or replacing the optimal capacitance value of the capacitor under the EDA software interface, and extracting the corresponding plate S parameter;

s100, performing inverse Fourier transform on the power supply current noise frequency spectrum obtained in the S60 to obtain a time domain current noise file;

s110, building a simulation link in the ADS of the EDA software, and simulating to obtain the time domain voltage noise with the increased active replacement capacitance;

and S120, obtaining an optimal improvement scheme through simulation, welding the optimal improvement scheme on a PCB to perform actual measurement verification, and finishing the improvement of the power supply noise after the verification is qualified.

Preferably, the chip for determining that the power supply noise on the plate power supply network exceeds the standard is a chip for determining that the power supply noise between each load chip power supply and a ground pin is tested by using an oscilloscope, and the comparison is carried out with the requirements of a chip manual.

Preferably, the sampling rate of the oscilloscope is set, the sampling rate is recorded as X, the value is set to be greater than or equal to the maximum frequency of the power supply noise, and the unit of the sampling rate is S/S, namely one point is sampled per second.

Preferably, the storage depth of the oscilloscope is set, the storage depth is recorded as L, the number of sampling points stored when the oscilloscope stores waveforms is represented by S, L > -X/Y, where Y is the lowest frequency of the power supply noise spectrum.

Preferably, the EDA software comprises POWERSI or OPI.

Preferably, the determining of the corresponding relationship of the capacitance value corresponding to the best filtering effect according to the found frequency points of the frequency spectrum peaks includes that the energy peaks of the current noise spectrum and the voltage noise spectrum are at 30KHz, 60KHz, 95KHz, 140KHz and 1MHz, the best filtering capacitance value corresponding to the noise of 30KHz to 140KHz is 220uF, and the best filtering capacitance value corresponding to the noise of 1MHz is 10 uF.

The invention has the following beneficial effects: the power supply noise improvement mode which needs to be subjectively judged by manpower and experience in the prior art is abandoned, the capacitance value of the filter capacitor which needs to be added or replaced can be accurately determined, and meanwhile, the number and the optimal position of the capacitor can be rapidly and efficiently determined by a simulation means.

Drawings

FIG. 1 is a flowchart illustrating steps of a method for improving power noise based on frequency domain according to an embodiment of the present invention;

FIG. 2 is a diagram of an equivalent circuit of a plate power supply network of a method for improving power supply noise based on frequency domain according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a waveform file of a data format in the method S30 for improving power supply noise based on frequency domain according to an embodiment of the present invention;

FIG. 4 is a graph of the voltage noise spectrum of the method for improving power supply noise based on frequency domain S40 according to an embodiment of the present invention;

FIG. 5 is a frequency domain impedance plot of a PCB power network in a method S50 for improving power noise based on frequency domain according to an embodiment of the present invention;

fig. 6 is a schematic diagram illustrating a power network current noise spectrum distribution in the method S60 for improving power noise based on frequency domain according to an embodiment of the present invention;

fig. 7 is a schematic diagram of peak frequency points of the frequency spectrum distribution of the voltage noise and the current noise in the method S70 for improving power supply noise based on the frequency domain according to the embodiment of the present invention;

fig. 8 is a schematic diagram illustrating comparison between before and after optimization of a simulation link in the method S110 for improving power supply noise based on frequency domain according to the embodiment of the present invention;

fig. 9 is a diagram of voltage noise comparison waveforms before and after optimization of the method for improving power supply noise based on frequency domain according to the embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.