CN115856701A - Linear power supply noise testing device, system and method - Google Patents
Linear power supply noise testing device, system and method Download PDFInfo
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- CN115856701A CN115856701A CN202211658258.1A CN202211658258A CN115856701A CN 115856701 A CN115856701 A CN 115856701A CN 202211658258 A CN202211658258 A CN 202211658258A CN 115856701 A CN115856701 A CN 115856701A
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Abstract
The embodiment of the invention provides a linear power supply noise testing device, a system and a method, and relates to the technical field of electronic measurement. The device comprises an alternating current coupling module, a power amplification module, a filtering module and a power supply module, wherein the alternating current coupling module is used for carrying out alternating current coupling on an original noise signal output by a tested linear power supply and outputting an alternating current noise signal, the power amplification module is used for amplifying the alternating current noise signal and outputting the amplified noise signal, and the filtering module is used for carrying out filtering processing on the amplified noise signal and outputting the filtered noise signal so that a testing instrument can test the filtered noise signal. The noise signal is amplified and filtered by designing the power amplification module and the filtering module, so that the noise signal can meet the requirement of a test instrument on the minimum measuring range, irrelevant noise is shielded, and the accurate measurement of the noise of the linear power supply is realized. The whole testing device is low in cost, convenient to use and simple to operate, and can meet the requirement of daily testing of research and development personnel.
Description
Technical Field
The invention relates to the technical field of electronic measurement, in particular to a linear power supply noise testing device, system and method.
Background
Linear power Supplies (LDOs) are commonly used power supplies in electronic products that convert different voltage inputs into a stable voltage output through a feedback loop. Noise of the linear power supply is an important parameter for measuring the quality of the linear power supply, and therefore, it is very important to perform noise test on the linear power supply.
In the prior art, because the noise of a linear power supply is very small, generally only 1uVrms and about 6uV peak-to-peak values, and the minimum range of a common test instrument is far greater than 6uV, the noise of the linear power supply cannot be directly tested, a high-end frequency spectrograph with very small noise floor is required to be used for testing, and the equipment is very expensive and difficult to obtain, and cannot meet the daily test use of research and development personnel.
Disclosure of Invention
The invention aims to provide a linear power supply noise test device, a system and a method, which aim to solve the technical problems of high cost and inconvenient use in the conventional linear power supply noise test.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:
in a first aspect, the invention provides a linear power supply noise testing device, which comprises an alternating current coupling module, a power amplification module, a filtering module and a power supply module, wherein the alternating current coupling module, the power amplification module and the filtering module are sequentially electrically connected, and the power supply module is electrically connected with the alternating current coupling module, the power amplification module and the filtering module; the alternating current coupling module is also electrically connected with a tested linear power supply, and the filtering module is also electrically connected with a testing instrument;
the alternating current coupling module is used for performing alternating current coupling on an original noise signal output by the tested linear power supply and outputting an alternating current noise signal;
the power amplification module is used for amplifying the alternating current noise signal and outputting the amplified noise signal;
the filtering module is used for filtering the amplified noise signal and outputting the filtered noise signal so that the test instrument can test the filtered noise signal conveniently.
In an alternative embodiment, the ac coupling module includes a plurality of coupling capacitors, and the plurality of coupling capacitors are connected in parallel;
one end of each coupling capacitor is electrically connected with the linear power supply to be tested, and the other end of each coupling capacitor is electrically connected with the power amplification module.
In an optional implementation manner, the ac coupling module further includes a pull-down resistor, one end of the pull-down resistor is electrically connected to the other end of each coupling capacitor, and the other end of the pull-down resistor is grounded.
In an alternative embodiment, the power amplification module comprises a plurality of proportional amplification circuits and a summing amplification circuit, and the plurality of proportional amplification circuits are connected in parallel;
one end of each proportional amplifying circuit is electrically connected with the alternating current coupling module, the other end of each proportional amplifying circuit is electrically connected with one end of the addition amplifying circuit, and the other end of the addition amplifying circuit is electrically connected with the filtering module;
the proportional amplifying circuit is used for amplifying the alternating current noise signal output by the alternating current coupling module by a preset multiple and outputting the noise signal amplified by the preset multiple;
the addition amplifying circuit is used for adding the noise signals which are output by the proportional amplifying circuits and amplified by preset times to obtain the amplified noise signals.
In an optional embodiment, each of the proportional amplifying circuits includes a first operational amplifier, a first capacitor, a first resistor, and a second resistor, a first input terminal of the first operational amplifier is electrically connected to the ac coupling module, and an output terminal of the first operational amplifier is electrically connected to one end of the summing amplifying circuit;
the first resistor is electrically connected between the second input end and the output end of the first operational amplifier, and the first capacitor is connected with the first resistor in parallel; one end of the second resistor is electrically connected with the second input end of the first operational amplifier, and the other end of the second resistor is grounded.
In an optional embodiment, the summing and amplifying circuit includes a second operational amplifier, a third resistor, and a plurality of fourth resistors, and a plurality of the proportional amplifying circuits are in one-to-one correspondence with the plurality of fourth resistors;
the first input end of the second operational amplifier is grounded, and the output end of the second operational amplifier is electrically connected with the filtering module; the third resistor is electrically connected between the second input end and the output end of the second operational amplifier, one end of the fourth resistor is electrically connected with the second input end of the second operational amplifier, and the other end of the fourth resistor is electrically connected with the corresponding proportional amplifying circuit.
In an optional embodiment, the filtering module includes a high-pass filtering circuit and a low-pass filtering circuit, one end of the high-pass filtering circuit is electrically connected to the power amplifying module, and the other end of the high-pass filtering circuit is electrically connected to one end of the low-pass filtering circuit; the other end of the low-pass filter circuit is electrically connected with the test instrument;
the high-pass filter circuit is used for filtering low-frequency components in the amplified noise signals;
the low-pass filter circuit is used for filtering high-frequency components in the amplified noise signals.
In an optional embodiment, the high-pass filter circuit includes a third operational amplifier, a second capacitor, a third capacitor, a fifth resistor, and a sixth resistor, and the second capacitor and the third capacitor are connected in series between the power amplification module and the first input terminal of the third operational amplifier;
one end of the fifth resistor is electrically connected with the first input end of the third operational amplifier, and the other end of the fifth resistor is grounded; one end of the sixth resistor is electrically connected between the second capacitor and the third capacitor, and the other end of the sixth resistor is electrically connected with the output end of the third operational amplifier; and the second input end and the output end of the third operational amplifier are electrically connected, and the output end of the third operational amplifier is also electrically connected with one end of the low-pass filter circuit.
In an alternative embodiment, the low pass filter circuit comprises a plurality of low pass filters connected in series between the high pass filter circuit and the test instrument;
each low-pass filter comprises a fourth operational amplifier, a fourth capacitor, a fifth capacitor, a seventh resistor and an eighth resistor, one end of the seventh resistor is electrically connected with the other end of the high-pass filter circuit or the output end of the fourth operational amplifier of the adjacent previous low-pass filter, the other end of the seventh resistor is electrically connected with one end of the eighth resistor, and the other end of the eighth resistor is electrically connected with the first input end of the fourth operational amplifier;
one end of the fourth capacitor is electrically connected with the first input end of the fourth operational amplifier, and the other end of the fourth capacitor is grounded; one end of the fifth capacitor is electrically connected between the seventh resistor and the eighth resistor, and the other end of the fifth capacitor is electrically connected with the output end of the fourth operational amplifier; and the second input end and the output end of the fourth operational amplifier are electrically connected, and the output end of the fourth operational amplifier is also electrically connected with one end of a seventh resistor of an adjacent subsequent low-pass filter or the test instrument.
In an optional embodiment, the linear power supply noise testing device further includes a shielding shell, and the ac coupling module, the power amplification module, the filtering module, the power supply module and the measured linear power supply are all accommodated in the shielding shell; the shielding shell is used for shielding electromagnetic wave signals.
In an alternative embodiment, the shielding shell comprises a first shielding shell and a second shielding shell, the second shielding shell is accommodated in the first shielding shell, and the first shielding shell and the second shielding shell are connected through a connecting piece; the alternating current coupling module, the power amplification module, the filtering module, the power supply module and the tested linear power supply are all accommodated in the second shielding shell; the connecting piece is made of non-ferromagnetic material; the first shielding shell and the second shielding shell are made of different metal materials.
In an alternative embodiment, the first shielding shell is made of aluminum material, and the thickness of the first shielding shell is 0.3mm; the second shielding shell is made of a nickel alloy material, and the thickness of the second shielding shell is 0.5mm.
In an optional embodiment, the ac coupling module and the power amplification module, the power amplification module and the filtering module, and the filtering module and the test instrument are connected through a BNC interface; wherein the BNC interface between the filter module and the test instrument is disposed on the shielding case.
In an alternative embodiment, the power supply module uses a lithium ion battery.
In a second aspect, the present invention provides a linear power supply noise test system, which includes a linear power supply to be tested, a test instrument, and the linear power supply noise test apparatus according to any one of the foregoing embodiments.
In an optional embodiment, the positive electrode and the negative electrode of the power supply input end of the tested linear power supply are in short circuit.
In a third aspect, the present invention provides a linear power supply noise test method applied to the linear power supply noise test apparatus described in any one of the foregoing embodiments, the method including:
the alternating current coupling module carries out alternating current coupling on an original noise signal output by the tested linear power supply and outputs an alternating current noise signal;
the power amplification module is used for amplifying the alternating current noise signal and outputting the amplified noise signal;
the filtering module is used for filtering the amplified noise signal and outputting a filtered noise signal, so that the test instrument tests the filtered noise signal.
In the device, the system and the method for testing the noise of the linear power supply provided by the embodiment of the invention, the device for testing the noise of the linear power supply comprises an alternating current coupling module, a power amplification module, a filtering module and a power supply module, wherein the alternating current coupling module, the power amplification module and the filtering module are sequentially and electrically connected, and the power supply module is electrically connected with the alternating current coupling module, the power amplification module and the filtering module; the alternating current coupling module is also electrically connected with the tested linear power supply, and the filtering module is also electrically connected with the testing instrument; the alternating current coupling module is used for carrying out alternating current coupling on an original noise signal output by the tested linear power supply and outputting an alternating current noise signal; the power amplification module is used for amplifying the alternating-current noise signal and outputting the amplified noise signal; the filtering module is used for filtering the amplified noise signal and outputting the filtered noise signal so that a test instrument can test the filtered noise signal. The noise testing device for the linear power supply amplifies and filters the noise signal by designing the power amplification module and the filtering module, so that the noise signal can meet the requirement of the testing instrument on the minimum measuring range, and irrelevant noise is shielded, thereby realizing accurate measurement of the noise of the linear power supply. The whole testing device is low in cost, convenient to use and simple to operate, and can meet the requirement of daily testing of research and development personnel.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic diagram of a linear power supply noise test system according to an embodiment of the present invention;
fig. 2 is a schematic functional block diagram of a linear power supply noise testing apparatus according to an embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of an AC coupling module;
FIG. 4 is a schematic diagram of another circuit structure of the AC coupling module;
FIG. 5 is a schematic diagram of a circuit configuration of a power amplification module;
FIG. 6 is a schematic diagram of the circuit structure of the proportional amplifier circuit and the summing amplifier circuit;
FIG. 7 is a schematic diagram of the circuit components of the filter module;
FIG. 8 is a schematic circuit diagram of a high-pass filter circuit and a low-pass filter circuit;
fig. 9 is a schematic structural diagram of a linear power supply noise testing apparatus according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of a linear power supply noise testing apparatus according to an embodiment of the present invention;
fig. 11 is a schematic flow chart of a linear power supply noise testing method according to an embodiment of the present invention.
Icon: 10-linear power supply noise test system; 100-linear power supply under test; 200-a linear power supply noise test device; 300-a test instrument; 210-an ac coupling module; 220-a power amplification module; 230-a filtering module; 240-power supply module; 250-a shielding shell; 211-coupling capacitance; 212-pull-down resistor; 221-a proportional amplifying circuit; 222-an addition amplification circuit; 231-a high-pass filter circuit; 232-low pass filter circuit; 2321-low pass filter; 251-a first shield shell; 252-a second shielding shell; 253-a connector; OP 1-first operational amplifier; OP 2-second operational amplifier; OP 3-third operational amplifier; OP 4-fourth operational amplifier; r1-a first resistor; r2-a second resistor; r3-a third resistor; r4-a fourth resistor; r5-a fifth resistor; r6-sixth resistor; r7-seventh resistor; r8-eighth resistance; c1-a first capacitor; c2-a second capacitor; c3-third capacitance; c4-fourth capacitance; c5-fifth capacitance.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the 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.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. indicate an orientation or a positional relationship based on that shown in the drawings or that the product of the present invention is used as it is, this is only for convenience of description and simplification of the description, and it does not indicate or imply that the device or the element referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention.
Furthermore, the appearances of the terms "first," "second," and the like, if any, are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
It should be noted that the features of the embodiments of the present invention may be combined with each other without conflict.
In the existing linear power supply noise test scheme, because the noise of a linear power supply is very small, generally only 1uVrms and about 6uV peak-to-peak value, and the minimum range of a common test instrument (such as an oscilloscope) is generally 1mV and much larger than 6uV, the noise of the linear power supply cannot be directly tested, a high-end frequency spectrograph with very small bottom noise needs to be used for testing, and the equipment is very expensive and difficult to obtain, and cannot meet the daily test use of research and development personnel.
Based on this, the embodiment of the invention provides a linear power supply noise testing device, a system and a method, which design a simple linear power supply noise testing device, and utilize a power amplification module and a filtering module in the linear power supply noise testing device to amplify and filter a noise signal, so that the noise signal meets the minimum range requirement of a testing instrument, and irrelevant noise is shielded, thereby realizing accurate measurement of linear power supply noise. The whole testing device is low in cost, convenient to use and simple to operate, and can meet the requirement of daily testing of research and development personnel.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Fig. 1 is a schematic diagram of a linear power supply noise test system 10 according to an embodiment of the present invention. The linear power supply noise test system 10 includes a linear power supply 100 to be tested, a linear power supply noise test device 200, and a test instrument 300, wherein the linear power supply 100 to be tested is electrically connected to the linear power supply noise test device 200, and the linear power supply noise test device 200 is electrically connected to the test instrument 300.
In this embodiment, the linear power supply 100 under test is configured to output an original noise signal, and the linear power supply noise test apparatus 200 is configured to amplify and filter the original noise signal, so that the noise signal meets the minimum measurement range requirement of the test instrument 300, and finally, the amplified and filtered noise signal is tested by the test instrument 300.
The positive electrode and the negative electrode of the power input end of the tested linear power supply 100 are in short circuit, and input is not needed, so that the original noise signal output by the tested linear power supply 100 is the noise signal of the power chip, and the noise of the power chip is only tested. The test instrument 300 may be an oscilloscope or the like, but the embodiment is not limited thereto.
Fig. 2 is a functional block diagram of a linear power supply noise testing apparatus 200 according to an embodiment of the present invention. The linear power supply noise testing device 200 comprises an alternating current coupling module 210, a power amplification module 220, a filtering module 230 and a power supply module 240, wherein the alternating current coupling module 210, the power amplification module 220 and the filtering module 230 are sequentially electrically connected, and the power supply module 240 is electrically connected with the alternating current coupling module 210, the power amplification module 220 and the filtering module 230; the ac coupling module 210 is further electrically connected to the tested linear power supply 100, and the filtering module 230 is further electrically connected to the testing apparatus 300.
The ac coupling module 210 is configured to perform ac coupling on an original noise signal output by the measured linear power supply 100, and output an ac noise signal; the power amplification module 220 is configured to amplify the ac noise signal and output the amplified noise signal; the filtering module 230 is configured to filter the amplified noise signal and output a filtered noise signal, so that the test instrument 300 performs a test on the filtered noise signal.
In this embodiment, the linear power noise is an ac signal, and ac coupling is performed before the linear power noise is input to the power amplification module 220 to isolate an unnecessary dc signal, so that the original noise signal output by the measured linear power 100 needs to be input to the ac coupling module 210 for ac coupling first to filter a dc component in the original noise signal, so as to obtain an ac noise signal. The power amplification module 220 amplifies the ac noise signal, so that the noise of the linear power supply 100 to be tested can be increased to meet the requirement of the minimum measurement range (measurement accuracy) of the test instrument 300; the filtering module 230 is used to filter the amplified noise signal, so as to shield other noise signals unrelated to the noise of the linear power supply 100 under test, and thus the test instrument 300 can more accurately measure the noise of the linear power supply 100 under test.
Therefore, the noise testing device for the linear power supply provided by the embodiment of the invention can enable the noise signal to meet the minimum range requirement of a testing instrument and shield irrelevant noise by designing the power amplification module and the filtering module to amplify and filter the noise signal, thereby realizing accurate measurement of the noise of the linear power supply. The whole testing device is low in cost, convenient to use and simple to operate, and can meet the requirement of daily testing of research and development personnel.
Alternatively, the power supply module 240 may adopt a lithium ion battery.
In the present embodiment, the lithium ion battery with less noise is used to supply power to each module in the linear power supply noise test apparatus 200, considering that the switching noise of the power supply is coupled into the circuit of the linear power supply noise test apparatus 200 due to the power supply. In one implementation, power module 240 may be in the form of a battery box, for example, four lithium ion batteries are placed in the battery box, and are connected in parallel, one group providing positive power to each module and one group providing negative power to each module.
Optionally, the ac coupling module 210 and the power amplification module 220, the power amplification module 220 and the filtering module 230, and the filtering module 230 and the test instrument 300 may be connected through a BNC (Bayonet Nut Connector). By using the BNC interface as the input/output interface to be connected with an external test instrument, on one hand, the impedance matching requirement can be met, and the signal reflection is prevented, and on the other hand, the loop area of a probe of the test instrument can be reduced, and the noise of loop coupling is reduced.
Optionally, in order to ensure the accuracy of noise measurement, in the actual design of the ac coupling module 210, a thin film capacitor with low noise needs to be used, but considering that a thin film capacitor with a large capacitance value has a large volume and is not easy to integrate, the same effect can be achieved by connecting a plurality of small capacitors in parallel in this embodiment.
Referring to fig. 3, the ac coupling module 210 includes a plurality of coupling capacitors 211, and the coupling capacitors 211 are connected in parallel; one end of each coupling capacitor 211 is electrically connected to the measured linear power supply 100, and the other end of each coupling capacitor 211 is electrically connected to the power amplification module 220.
In this embodiment, the specific number of the coupling capacitors 211 and the capacitance parameter can be set according to actual requirements. For example, 10 coupling capacitors 211 of 47uF may be connected in parallel in the ac coupling module 210 to implement ac coupling on the original noise signal output by the measured linear power supply 100.
Optionally, referring to fig. 4, the ac coupling module 210 may further include a pull-down resistor 212, one end of the pull-down resistor 212 is electrically connected to the other end of each coupling capacitor 211, and the other end of the pull-down resistor 212 is grounded.
In this embodiment, the resistance of the pull-down resistor 212 may be set according to actual needs, and may be, for example, 100 ohms. By adding the pull-down resistor 212 in the ac coupling module 210, the coupling capacitor 211 and the pull-down resistor 212 can form a high-pass filter, and the ac coupling module 210 can also perform a filtering function while isolating a dc signal.
Optionally, referring to fig. 5, the power amplifying module 220 includes a plurality of scaling circuits 221 and an adding and amplifying circuit 222, wherein the scaling circuits 221 are connected in parallel; one end of each of the proportional amplifying circuits 221 is electrically connected to the ac coupling module 210, the other end of each of the proportional amplifying circuits 221 is electrically connected to one end of the addition amplifying circuit 222, and the other end of the addition amplifying circuit 222 is electrically connected to the filter module 230.
The proportional amplifying circuit 221 is configured to amplify the ac noise signal output by the ac coupling module 210 by a preset multiple, and output a noise signal amplified by the preset multiple; the adding and amplifying circuit 222 is configured to add the noise signals amplified by the preset times and output by each of the proportional amplifying circuits to obtain an amplified noise signal.
For example, if 4 parallel proportional amplifying circuits 221 are provided, and the amplification factor of each proportional amplifying circuit 221 is 5000 times, the addition amplifying circuit 222 adds the 5000-times amplified noise signals output by the proportional amplifying circuits 221, and the obtained amplified noise signal is amplified by 2 ten thousand times relative to the original noise signal, so that the minimum measurement accuracy requirement of the oscilloscope can be met.
Next, specific circuit configurations of the proportional amplifier circuit 221 and the addition amplifier circuit 222 will be described. Referring to fig. 6, each of the proportional amplifying circuits 221 includes a first operational amplifier OP1, a first capacitor C1, a first resistor R1, and a second resistor R2, a first input end of the first operational amplifier OP1 is electrically connected to the ac coupling module 210, and an output end of the first operational amplifier OP1 is electrically connected to one end of the summing amplifying circuit 222; the first resistor R1 is electrically connected between the second input end and the output end of the first operational amplifier OP1, and the first capacitor C1 is connected with the first resistor R1 in parallel; one end of the second resistor R2 is electrically connected to the second input terminal of the first operational amplifier OP1, and the other end of the second resistor R2 is grounded.
In this embodiment, the first operational amplifier OP1 includes a non-inverting input terminal and an inverting input terminal, and when the first input terminal is the non-inverting input terminal, the second input terminal is the inverting input terminal; similarly, when the first input terminal is an inverting input terminal, the second input terminal is a non-inverting input terminal. The first input terminal of the first operational amplifier OP1 may be electrically connected to another terminal of each coupling capacitor 211 in the ac coupling module 210.
The first capacitor C1 is used to reduce the bandwidth of the first operational amplifier OP1, and reduce the noise of the irrelevant frequency band except the noise of the tested linear power supply 100.
Since the plurality of proportional amplifying circuits 221 are connected in parallel, 2 identical proportional amplifying circuits 221 are connected in parallel, the RMS noise of the operational amplifier can be reduced by 2 times, and the operational amplifier noise is reduced to 1/2 of that of a single operational amplifier by connecting 4 identical proportional amplifying circuits 221 in parallel. The operational amplifier noise is reduced by the way that the plurality of proportional amplifying circuits 221 are connected in parallel, and the operational amplifier noise can be effectively prevented from being superposed on the noise signal of the tested linear power supply 100, so that the accuracy of the noise test is improved.
Referring to fig. 6, the summing amplifier 222 includes a second operational amplifier OP2, a third resistor R3 and a plurality of fourth resistors R4, and the plurality of proportional amplifying circuits 221 are in one-to-one correspondence with the plurality of fourth resistors R4; the first input end of the second operational amplifier OP2 is grounded, and the output end of the second operational amplifier OP2 is electrically connected with the filtering module 230; the third resistor R3 is electrically connected between the second input terminal and the output terminal of the second operational amplifier OP2, one end of the fourth resistor R4 is electrically connected to the second input terminal of the second operational amplifier OP2, and the other end of the fourth resistor R4 is electrically connected to the corresponding proportional amplifier circuit 221.
In the present embodiment, similar to the first operational amplifier OP1, the second operational amplifier OP2 also includes a non-inverting input terminal and an inverting input terminal, and when the first input terminal is the non-inverting input terminal, the second input terminal is the inverting input terminal; similarly, when the first input terminal is an inverting input terminal, the second input terminal is a non-inverting input terminal. The other end of the fourth resistor R4 may be electrically connected to the output end of the first operational amplifier OP1 in the corresponding proportional amplifying circuit 221.
Optionally, referring to fig. 7, the filtering module 230 includes a high-pass filtering circuit 231 and a low-pass filtering circuit 232, one end of the high-pass filtering circuit 231 is electrically connected to the power amplifying module 220, and the other end of the high-pass filtering circuit 231 is electrically connected to one end of the low-pass filtering circuit 232; the other end of the low pass filter circuit 232 is electrically connected to the test instrument 300.
The high-pass filter circuit 231 is configured to filter out a low-frequency component in the amplified noise signal; the low-pass filter circuit 232 is used to filter out high-frequency components in the amplified noise signal.
In this embodiment, the low-frequency interference can be removed by setting the high-pass filter circuit 231 to filter the low-frequency component in the amplified noise signal; the high frequency interference can be removed by providing a low pass filter circuit 232 to filter out the high frequency components in the amplified noise signal. In this way, other noise signals unrelated to the noise of the linear power supply 100 under test can be shielded, so that the test instrument 300 can more accurately measure the noise of the linear power supply 100 under test.
Next, specific circuit configurations of the high-pass filter circuit 231 and the low-pass filter circuit 232 will be described. Referring to fig. 8, the high-pass filter circuit 231 includes a third operational amplifier OP3, a second capacitor C2, a third capacitor C3, a fifth resistor R5 and a sixth resistor R6, wherein the second capacitor C2 and the third capacitor C3 are connected in series between the power amplification module 220 and the first input terminal of the third operational amplifier OP 3; one end of the fifth resistor R5 is electrically connected to the first input end of the third operational amplifier OP3, and the other end of the fifth resistor R5 is grounded; one end of the sixth resistor R6 is electrically connected between the second capacitor C2 and the third capacitor C3, and the other end of the sixth resistor R6 is electrically connected to the output end of the third operational amplifier OP 3; the second input end and the output end of the third operational amplifier OP3 are electrically connected, and the output end of the third operational amplifier OP3 is further electrically connected to one end of the low-pass filter circuit 232.
In this embodiment, the third operational amplifier OP3 comprises a non-inverting input terminal and an inverting input terminal, and for the third operational amplifier OP3, when the first input terminal is the non-inverting input terminal, the second input terminal is the inverting input terminal; when the first input terminal is an inverting input terminal, the second input terminal is a non-inverting input terminal.
The second capacitor C2 and the third capacitor C3 may be specifically connected in series between the output end of the second operational amplifier OP2 and the first input end of the third operational amplifier OP3 in the power amplification module 220.
Referring to fig. 8, the low pass filter circuit 232 includes a plurality of low pass filters 2321, and the plurality of low pass filters 2321 are connected in series between the high pass filter circuit 231 and the testing apparatus 300. Each of the low pass filters 2321 includes a fourth operational amplifier OP4, a fourth capacitor C4, a fifth capacitor C5, a seventh resistor R7 and an eighth resistor R8, one end of the seventh resistor R7 is electrically connected to the other end of the high pass filter circuit 231 or the output end of the fourth operational amplifier OP4 of the adjacent previous low pass filter 2321, the other end of the seventh resistor R7 is electrically connected to one end of the eighth resistor R8, and the other end of the eighth resistor R8 is electrically connected to the first input end of the fourth operational amplifier OP 4.
One end of the fourth capacitor C4 is electrically connected to the first input end of the fourth operational amplifier OP4, and the other end of the fourth capacitor C4 is grounded; one end of a fifth capacitor C5 is electrically connected between the seventh resistor R7 and the eighth resistor R8, and the other end of the fifth capacitor C5 is electrically connected to the output end of the fourth operational amplifier OP 4; the second input terminal and the output terminal of the fourth operational amplifier OP4 are electrically connected, and the output terminal of the fourth operational amplifier OP4 is further electrically connected to one terminal of the seventh resistor R7 of the next adjacent low-pass filter 2321 or the testing apparatus 300.
In this embodiment, the fourth operational amplifier OP4 includes a non-inverting input terminal and an inverting input terminal, and when the first input terminal is the non-inverting input terminal, the second input terminal is the inverting input terminal; when the first input terminal is an inverting input terminal, the second input terminal is a non-inverting input terminal.
Among the plurality of low-pass filters 2321 connected in series between the high-pass filter circuit 231 and the testing instrument 300, the seventh resistor R7 and the eighth resistor R8 of the first low-pass filter 2321 are connected in series between the output end of the third operational amplifier OP3 in the high-pass filter circuit 231 and the first input end of the fourth operational amplifier OP4 of the current low-pass filter 2321; the seventh resistor R7 and the eighth resistor R8 in the remaining low-pass filters 2321 are connected in series between the output end of the fourth operational amplifier OP4 of the previous adjacent low-pass filter 2321 and the first input end of the fourth operational amplifier OP4 of the current low-pass filter 2321. Moreover, the output terminal of the fourth operational amplifier OP4 in the last low-pass filter 2321 is electrically connected to the testing apparatus 300, and the output terminal of the fourth operational amplifier OP4 in the remaining low-pass filters 2321 is electrically connected to one terminal of the seventh resistor R7 of the next low-pass filter 2321.
It should be noted that, each low-pass filter 2321 in the low-pass filter circuit 232 has the same circuit structure, and in practical applications, the resistance-capacitance parameters in each low-pass filter 2321 may be different. That is, each low-pass filter 2321 is composed of an operational amplifier and a corresponding peripheral circuit (two capacitors and two resistors), but the capacitance parameters of each capacitor (C4, C5) and the resistance parameters of each resistor (R7, R8) in different low-pass filters 2321 may be different, and the specific value may be obtained according to the transfer function when the circuit is designed.
In this embodiment, since the noise of the linear power supply is generally distributed between 10Hz and 100KHz, a 2-order 10Hz high-pass filter can be implemented by the third operational amplifier OP3 and its peripheral circuit to filter low-frequency components below 10 Hz; the high-order low-pass filter of 100kHz can be implemented by the plurality of fourth operational amplifiers OP4 and the peripheral circuits thereof (for example, a 100kHz 4-order low-pass filter can be formed by using 2 fourth operational amplifiers OP4 and the peripheral circuits thereof, and the higher the order, the better the filtering effect is), so as to filter out high-frequency components above 100kHz, effectively shield other noise signals unrelated to the noise of the linear power supply 100 to be tested, and enable the test instrument 300 to more accurately measure the noise of the linear power supply 100 to be tested.
In practical application, considering that environmental noise can affect the test result when a small-noise test is performed, the test is preferably performed in a darkroom, and the electromagnetic environment of a common laboratory is complex, so that electromagnetic shielding needs to be performed on the tested equipment and the testing device.
Based on this, referring to fig. 9, the linear power supply noise test apparatus 200 provided in the embodiment of the present invention further includes a shielding housing 250, wherein the ac coupling module 210, the power amplification module 220, the filtering module 230, the power supply module 240 and the tested linear power supply 100 are all accommodated in the shielding housing 250; the shield case 250 serves to shield an electromagnetic wave signal.
The tested linear power supply 100 may be placed in the shielding case 250 and connected to the ac coupling module 210 when a noise test is required. The BNC interface between the filter module 230 and the test instrument 300 may be disposed on the shielded enclosure 250.
In this embodiment, through designing a shield shell, each module in with testing arrangement and the equal holding of measured linear power supply are inside shield shell, can all play the effect of absorption, reflection and offsetting the energy to the interference electromagnetic wave that comes from outside and inside electromagnetic wave, so can effectively weaken the interference of electromagnetic wave signal to the noise test, make the research and development personnel can carry out the test of LDO noise under ordinary test environment, and the precision is high, and is with low costs, the operation of being convenient for.
In practical application, when the frequency of the interference electromagnetic wave is low, a material with high magnetic permeability is adopted, so that magnetic lines of force are limited in the shielding body and prevented from being diffused to a shielding space, and the larger the thickness is, the smaller the magnetic resistance is, and the better the magnetic field shielding effect is. When the frequency of the interference electromagnetic field is higher, the eddy current generated in the high-conductivity metal material is utilized to form the counteraction effect on the electromagnetic wave, so that the shielding effect is achieved. Due to the high frequency skin effect, eddy currents only flow in a thin layer on the surface of the shielding shell, and therefore the thickness of the shielding body does not have to be too large. Therefore, in order to shield high frequency and low frequency interference simultaneously, different metal materials can be used to form the multilayer shield.
In this embodiment, the shielding case 250 can be designed by using a nested structure of two material cases, which can have good shielding effect for both high frequency and low frequency electromagnetic fields. Referring to fig. 10, the shielding shell 250 includes a first shielding shell 251 and a second shielding shell 252, the second shielding shell 252 is accommodated in the first shielding shell 251, and the first shielding shell 251 and the second shielding shell 252 are connected by a connecting member 253; the ac coupling module 210, the power amplification module 220, the filtering module 230, the power supply module 240 and the measured linear power supply 100 are all accommodated in the second shielding case 252; the connecting piece 253 adopts non-ferromagnetic material; the first shield shell 251 and the second shield shell 252 use different metal materials.
The BNC interface between the filter module 230 and the test instrument 300 may be disposed on the first shielding shell 251 of the shielding shell 250.
In this embodiment, the first shielding case 251 is an outer case, and a diamagnetic material with strong reflection capability, such as copper, aluminum, etc., can be used; the second shielding case 252 is an inner case, and a material with high magnetic permeability, such as nickel alloy, may be used.
In one example, the first shielding case 251 may employ an aluminum material, and the thickness of the first shielding case 251 is 0.3mm; the second shield case 252 may be made of a nickel alloy material, and the thickness of the second shield case 252 is 0.5mm.
In this embodiment, the connecting member 253 may be made of a non-ferromagnetic material such as copper or aluminum, and the connecting member 253 connects the first shielding case 251 and the second shielding case 252, so that a good grounding effect can be ensured. For example, the connector 253 may be a copper pillar, and the first shield shell 251 and the second shield shell 252 are connected by soldering the copper pillar to the first shield shell 251 and the second shield shell 252. The number of copper columns and the specific positions of the welding are determined according to actual conditions, and this embodiment is not limited to this.
It can be seen that the shielding housing 250 is designed by using a nested structure of two outer shells made of 0.3mm aluminum, an inner shell made of 0.5mm nickel alloy, and a copper column connection between the inner shell and the outer shell, so that high-frequency and low-frequency interference can be simultaneously shielded.
Based on the linear power supply noise test device 200, the embodiment of the invention also provides a linear power supply noise test method, which can be applied to the linear power supply noise test device 200. It should be noted that, the basic principle and the generated technical effect of the linear power noise testing method provided by the embodiment of the present invention are the same as those of the above embodiment, and for brief description, no part of this embodiment is mentioned, and corresponding contents in the above embodiment may be referred to. Referring to fig. 11, the method for testing linear power noise includes:
and step S101, performing alternating current coupling on an original noise signal output by the tested linear power supply by the alternating current coupling module, and outputting an alternating current noise signal.
And step S102, the power amplification module amplifies the alternating current noise signal and outputs the amplified noise signal.
And step S103, the filtering module carries out filtering processing on the amplified noise signal and outputs the filtered noise signal so that a test instrument can test the filtered noise signal conveniently.
Therefore, according to the linear power supply noise testing method provided by the embodiment of the invention, the original noise signal output by the tested linear power supply is subjected to alternating current coupling through the alternating current coupling module, and the direct current component in the original noise signal is filtered to obtain the alternating current noise signal; the power amplification module is used for amplifying the alternating-current noise signal, so that the noise of the tested linear power supply can be improved to meet the minimum range requirement of a testing instrument; the amplified noise signal is filtered by the filtering module, so that other noise signals irrelevant to the noise of the tested linear power supply can be shielded, and the noise of the tested linear power supply can be more accurately measured by the testing instrument. The whole testing device is low in cost, convenient to use and simple to operate, and can meet the requirement of daily testing of research and development personnel.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (17)
1. The linear power supply noise testing device is characterized by comprising an alternating current coupling module, a power amplification module, a filtering module and a power supply module, wherein the alternating current coupling module, the power amplification module and the filtering module are sequentially and electrically connected, and the power supply module is electrically connected with the alternating current coupling module, the power amplification module and the filtering module; the alternating current coupling module is also electrically connected with a tested linear power supply, and the filtering module is also electrically connected with a testing instrument;
the alternating current coupling module is used for performing alternating current coupling on an original noise signal output by the tested linear power supply and outputting an alternating current noise signal;
the power amplification module is used for amplifying the alternating current noise signal and outputting the amplified noise signal;
the filtering module is used for filtering the amplified noise signal and outputting the filtered noise signal so that the test instrument can test the filtered noise signal conveniently.
2. The linear power supply noise test device according to claim 1, wherein the ac coupling module comprises a plurality of coupling capacitors, and the plurality of coupling capacitors are connected in parallel;
one end of each coupling capacitor is electrically connected with the tested linear power supply, and the other end of each coupling capacitor is electrically connected with the power amplification module.
3. The linear power supply noise test device according to claim 2, wherein the ac coupling module further includes a pull-down resistor, one end of the pull-down resistor is electrically connected to the other end of each coupling capacitor, and the other end of the pull-down resistor is grounded.
4. The linear power supply noise test device according to claim 1, wherein the power amplification module comprises a plurality of proportional amplification circuits and a summing amplification circuit, and the plurality of proportional amplification circuits are connected in parallel;
one end of each proportional amplifying circuit is electrically connected with the alternating current coupling module, the other end of each proportional amplifying circuit is electrically connected with one end of the addition amplifying circuit, and the other end of the addition amplifying circuit is electrically connected with the filtering module;
the proportional amplifying circuit is used for amplifying the alternating current noise signal output by the alternating current coupling module by a preset multiple and outputting the noise signal amplified by the preset multiple;
the addition amplifying circuit is used for adding the noise signals which are output by the proportional amplifying circuits and amplified by preset times to obtain the amplified noise signals.
5. The linear power supply noise test device according to claim 4, wherein each of the proportional amplifying circuits comprises a first operational amplifier, a first capacitor, a first resistor and a second resistor, a first input terminal of the first operational amplifier is electrically connected to the ac coupling module, and an output terminal of the first operational amplifier is electrically connected to one terminal of the summing amplifying circuit;
the first resistor is electrically connected between the second input end and the output end of the first operational amplifier, and the first capacitor is connected with the first resistor in parallel; one end of the second resistor is electrically connected with the second input end of the first operational amplifier, and the other end of the second resistor is grounded.
6. The linear power supply noise test device according to claim 4, wherein the summing amplification circuit comprises a second operational amplifier, a third resistor and a plurality of fourth resistors, and the plurality of proportional amplification circuits are in one-to-one correspondence with the plurality of fourth resistors;
the first input end of the second operational amplifier is grounded, and the output end of the second operational amplifier is electrically connected with the filtering module; the third resistor is electrically connected between the second input end and the output end of the second operational amplifier, one end of the fourth resistor is electrically connected with the second input end of the second operational amplifier, and the other end of the fourth resistor is electrically connected with the corresponding proportional amplifying circuit.
7. The linear power supply noise testing device according to claim 1, wherein the filtering module comprises a high-pass filtering circuit and a low-pass filtering circuit, one end of the high-pass filtering circuit is electrically connected with the power amplifying module, and the other end of the high-pass filtering circuit is electrically connected with one end of the low-pass filtering circuit; the other end of the low-pass filter circuit is electrically connected with the test instrument;
the high-pass filter circuit is used for filtering low-frequency components in the amplified noise signals;
the low-pass filter circuit is used for filtering high-frequency components in the amplified noise signals.
8. The linear power supply noise test device of claim 7, wherein the high-pass filter circuit comprises a third operational amplifier, a second capacitor, a third capacitor, a fifth resistor and a sixth resistor, and the second capacitor and the third capacitor are connected in series between the power amplification module and the first input terminal of the third operational amplifier;
one end of the fifth resistor is electrically connected with the first input end of the third operational amplifier, and the other end of the fifth resistor is grounded; one end of the sixth resistor is electrically connected between the second capacitor and the third capacitor, and the other end of the sixth resistor is electrically connected with the output end of the third operational amplifier; and the second input end and the output end of the third operational amplifier are electrically connected, and the output end of the third operational amplifier is also electrically connected with one end of the low-pass filter circuit.
9. The linear power supply noise test apparatus of claim 7, wherein the low pass filter circuit comprises a plurality of low pass filters, the plurality of low pass filters being connected in series between the high pass filter circuit and the test instrument;
each low-pass filter comprises a fourth operational amplifier, a fourth capacitor, a fifth capacitor, a seventh resistor and an eighth resistor, one end of the seventh resistor is electrically connected with the other end of the high-pass filter circuit or the output end of the fourth operational amplifier of the adjacent previous low-pass filter, the other end of the seventh resistor is electrically connected with one end of the eighth resistor, and the other end of the eighth resistor is electrically connected with the first input end of the fourth operational amplifier;
one end of the fourth capacitor is electrically connected with the first input end of the fourth operational amplifier, and the other end of the fourth capacitor is grounded; one end of the fifth capacitor is electrically connected between the seventh resistor and the eighth resistor, and the other end of the fifth capacitor is electrically connected with the output end of the fourth operational amplifier; and the second input end and the output end of the fourth operational amplifier are electrically connected, and the output end of the fourth operational amplifier is also electrically connected with one end of a seventh resistor of an adjacent subsequent low-pass filter or the test instrument.
10. The linear power supply noise testing device according to claim 1, further comprising a shielding shell, wherein the ac coupling module, the power amplification module, the filtering module, the power supply module and the tested linear power supply are all accommodated in the shielding shell; the shielding shell is used for shielding electromagnetic wave signals.
11. The linear power supply noise testing device of claim 10, wherein the shielding shell comprises a first shielding shell and a second shielding shell, the second shielding shell is accommodated in the first shielding shell, and the first shielding shell and the second shielding shell are connected through a connecting piece; the alternating current coupling module, the power amplification module, the filtering module, the power supply module and the tested linear power supply are all accommodated in the second shielding shell; the connecting piece is made of non-ferromagnetic material; the first shielding shell and the second shielding shell are made of different metal materials.
12. The linear power supply noise test device according to claim 11, wherein the first shielding case is made of an aluminum material, and a thickness of the first shielding case is 0.3mm; the second shielding shell is made of a nickel alloy material, and the thickness of the second shielding shell is 0.5mm.
13. The linear power supply noise testing apparatus of claim 10, wherein the ac coupling module and the power amplification module, the power amplification module and the filtering module, and the filtering module and the testing instrument are connected through bayonet nut connectors BNC interfaces; wherein the BNC interface between the filter module and the test instrument is disposed on the shielding case.
14. The linear power supply noise testing device of any one of claims 1 to 13, wherein the power supply module employs a lithium ion battery.
15. A linear power supply noise test system comprising a linear power supply under test, a test instrument, and the linear power supply noise test apparatus of any one of claims 1 to 14.
16. The linear power supply noise test system of claim 15, wherein the positive and negative electrodes of the power supply input end of the tested linear power supply are short-circuited.
17. A linear power supply noise test method applied to the linear power supply noise test apparatus according to any one of claims 1 to 14, the method comprising:
the alternating current coupling module carries out alternating current coupling on an original noise signal output by the tested linear power supply and outputs an alternating current noise signal;
the power amplification module is used for amplifying the alternating current noise signal and outputting the amplified noise signal;
and the filtering module is used for filtering the amplified noise signal and outputting the filtered noise signal so that the test instrument can test the filtered noise signal conveniently.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118169436A (en) * | 2024-05-14 | 2024-06-11 | 南京星问科技有限公司 | Method and device for low noise test of equipment to be tested based on LDO test circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118169436A (en) * | 2024-05-14 | 2024-06-11 | 南京星问科技有限公司 | Method and device for low noise test of equipment to be tested based on LDO test circuit |
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