PWM (Pulse Width Modulation) signal acquisition circuit, test equipment and test system

Abstract

The invention relates to the technical field of signal processing, in particular to a PWM signal acquisition circuit, test equipment and a test system. The circuit comprises a reference module, a comparator, a sampling module, a filtering module, a noise reduction module and an output module, wherein the reference module is used for providing reference voltage; the noise reduction module is used for carrying out noise reduction processing on the signal processing process of the comparator; the in-phase input end of the comparator is used for inputting a collected initial PWM signal; the output end of the comparator outputs an initial acquisition signal according to the magnitude relationship between the reference voltage and the initial PWM signal; the sampling module is used for negating the initial acquisition signal to obtain a sampling signal; the filtering module is used for filtering the sampling signal and inputting a negative feedback signal obtained after filtering to an inverted input end of the comparator; and the output module is used for negating the negative feedback signal to obtain a target acquisition signal and outputting the target acquisition signal. By adopting the scheme of the invention, the accuracy of signal acquisition can be improved.

Description

Technical Field

[0001] This application relates to the field of signal processing technology, and in particular to a PWM signal acquisition circuit, testing equipment and testing system. Background Technology

[0002] In automotive R&D, when using a HIL (Hardware-in-the-Loop) simulation test system to test PWM signal control in a vehicle, the NI chassis and its associated boards simulate a vehicle model, outputting various excitation signals. The ECU, as the core test object, receives these excitation signals from the NI chassis and, based on its internal control algorithms and logic, issues PWM signals. The PWM signals output by the ECU need to be stepped down and fed back to the NI chassis, serving as the feedback input to the vehicle model, thus forming a complete closed-loop test system.

[0003] When stepping down the voltage of a PWM signal, a preset voltage threshold is typically used to truncate the PWM signal. That is, the portion of the PWM signal above the voltage threshold is output as a high level, while the portion below the voltage threshold is output as a low level. However, in automotive applications, the operating conditions are complex and there is a lot of interference; the set voltage threshold may contain some interference, leading to inaccurate step-down acquisition of the PWM signal.

[0004] Therefore, in scenarios involving PWM signal control testing of automobiles, improving the accuracy of PWM signal step-down acquisition is an urgent problem to be solved. Summary of the Invention

[0005] Therefore, it is necessary to provide a PWM signal acquisition circuit, testing equipment, and testing system that improves the accuracy of PWM signal step-down acquisition in the scenario of PWM signal control testing of automobiles, addressing the aforementioned technical problems.

[0006] In a first aspect, this application provides a PWM signal acquisition circuit, the circuit including a reference module, a comparator, a sampling module, a filtering module, a noise reduction module, and an output module, wherein:

[0007] The reference module is connected to the inverting input of the comparator and is used to provide a reference voltage;

[0008] The noise reduction module is connected to the comparator and is used to perform noise reduction processing on the signal processing of the comparator.

[0009] The non-inverting input of the comparator is used to input the initial PWM signal to be acquired; the output of the comparator outputs the initial acquisition signal according to the relationship between the reference voltage and the initial PWM signal.

[0010] The sampling module is connected to the output of the comparator and is used to invert the initial acquisition signal to obtain the sampling signal;

[0011] The filtering module is connected to the sampling module and the inverting input of the comparator; the filtering module is used to filter the sampled signal and input the resulting negative feedback signal to the inverting input of the comparator.

[0012] The output module is connected to the sampling module and is used to invert the negative feedback signal to obtain the target acquisition signal and output it.

[0013] In one embodiment, the noise reduction module includes a noise reduction capacitor and a noise reduction resistor, wherein:

[0014] The noise-reducing capacitor is connected in series between the output terminal and the non-inverting input terminal of the comparator; the capacitance of the noise-reducing capacitor is in the pF range.

[0015] The first end of the noise reduction resistor is connected to the output of the comparator, and the second end is used to input the excitation voltage.

[0016] In one embodiment, the inverting input of the comparator is connected to a pull-down resistor.

[0017] In one embodiment, the filtering module includes a filter capacitor and two filter resistors connected in parallel with the filter capacitor.

[0018] In one embodiment, the reference module includes a voltage switching module, an amplifier, and a proportional adjustment module, wherein:

[0019] The voltage switching module is used to receive multiple threshold voltages and connect to the non-inverting input terminal of the amplifier; the voltage switching module is used to control the on / off connection between each threshold voltage and the non-inverting input terminal of the amplifier.

[0020] The output of the amplifier is connected to the inverting input of the comparator to amplify the threshold voltage and obtain the reference voltage input to the inverting input of the comparator.

[0021] The proportional adjustment module is connected to the output terminal and the inverting input terminal of the amplifier and is used to adjust the amplification ratio of the amplifier.

[0022] In one embodiment, the voltage switching module includes a plurality of switching switches; wherein,

[0023] Each of the threshold voltages is connected to the non-inverting input of the amplifier via the switching switch;

[0024] The threshold voltage includes at least one constant internal threshold voltage and at least one variable external threshold voltage.

[0025] In one embodiment, the proportional adjustment module includes a switch, a first resistor, and a second resistor, wherein:

[0026] The first resistor is connected between the output terminal of the amplifier and the inverting input terminal of the amplifier;

[0027] The first terminal of the switching switch is grounded, and the second terminal is connected in series with the second resistor between the second terminal and the inverting input terminal of the amplifier.

[0028] In one embodiment, the non-inverting input of the amplifier is connected to a pull-down resistor and a voltage-regulating capacitor.

[0029] Secondly, embodiments of this application provide a testing device, which includes a PWM signal acquisition circuit as described in any one of the first aspects above.

[0030] Thirdly, embodiments of this application provide a testing system, which includes an NI chassis and the acquisition device described in the second aspect above; wherein the acquisition device is used to acquire an initial PWM signal, process the initial acquired PWM signal to obtain a target PWM signal, and output the target PWM signal to the NI chassis.

[0031] The aforementioned PWM signal acquisition circuit, testing equipment, and testing system utilize a comparator. When the initial PWM signal voltage is greater than the reference voltage, the comparator outputs a high-level initial acquisition signal; when the initial PWM signal voltage is less than the reference voltage, the comparator outputs a low-level initial acquisition signal. When the comparator outputs a high-level initial acquisition signal, the voltage of the initial acquisition signal is determined by the comparator's operating voltage (supply voltage). Since the comparator's operating voltage is relatively small, when faced with an initial PWM signal with a large amplitude, the comparator processes the signal to convert it into a target acquisition signal with a smaller voltage amplitude, thus achieving step-down acquisition of the initial PWM signal.

[0032] During the buck acquisition process, on the one hand, a noise reduction module is connected to the comparator to reduce the noise generated during operation, thereby improving the signal-to-noise ratio of the initial acquisition signal output by the comparator and thus improving signal accuracy. On the other hand, a negative feedback signal obtained through the sampling and filtering modules is re-inputted to the inverting input of the comparator, thereby achieving negative feedback adjustment so that the initial acquisition signal output by the comparator can reduce the influence of interference signals. By using the noise reduction module to improve the signal-to-noise ratio and the filtering module to reduce the influence of interference signals, the accuracy of the signal during the buck acquisition of the PWM signal is improved. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the overall structure of the acquisition circuit in one embodiment;

[0035] Figure 2 This is a schematic diagram of the first part of the acquisition circuit in one embodiment;

[0036] Figure 3 This is a schematic diagram of the overall structure of a reference module in one embodiment;

[0037] Figure 4 This is a schematic diagram of the second part of the acquisition circuit in one embodiment. Detailed Implementation

[0038] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0040] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0041] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.

[0042] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.

[0043] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0044] In one exemplary embodiment, this application provides a PWM signal acquisition circuit, such as... Figure 1 As shown, the circuit specifically includes a reference module, a comparator, a sampling module, a filtering module, a noise reduction module, and an output module. The functions and connections of each module are described below.

[0045] The reference module is connected to the inverting input of the comparator and is used to provide a reference voltage;

[0046] The noise reduction module is connected to the comparator and is used to perform noise reduction processing on the signal processing of the comparator.

[0047] The non-inverting input of the comparator is used to input the initial PWM signal to be acquired; the output of the comparator outputs the initial acquisition signal according to the relationship between the reference voltage and the initial PWM signal.

[0048] In the embodiments of this application, the comparator compares the magnitude relationship between the voltage of the initial PWM signal and the reference voltage. When the voltage of the initial PWM signal is greater than the reference voltage, the comparator outputs a high-level initial acquisition signal; when the voltage of the initial PWM signal is less than the reference voltage, the comparator outputs a low-level initial acquisition signal.

[0049] When the comparator outputs a high-level initial acquisition signal, the voltage of the initial acquisition signal is determined by the comparator's operating voltage (supply voltage).

[0050] In high-frequency applications, high signal accuracy is required, and comparator noise directly affects the signal-to-noise ratio (SNR) of the initial acquired signal output by the comparator. Therefore, to improve the SNR of the initial acquired signal output by the comparator in high-frequency applications, this embodiment connects a noise reduction module to the comparator to reduce noise during operation, thereby improving the SNR of the initial acquired signal output by the comparator and thus enhancing signal accuracy.

[0051] The sampling module is connected to the output of the comparator and is used to invert the initial acquisition signal to obtain the sampling signal;

[0052] The filtering module is connected to the sampling module and the inverting input of the comparator; the filtering module is used to filter the sampled signal and input the resulting negative feedback signal to the inverting input of the comparator.

[0053] The output module is connected to the sampling module and is used to invert the negative feedback signal to obtain the target acquisition signal and output it.

[0054] In this embodiment, the sampling module inverts the initial acquisition signal output by the comparator to obtain a sampling signal. Further, the negative feedback signal is filtered by the filtering module to remove interference signals. The filtered negative feedback signal is then re-inputted to the inverting input of the comparator, thereby achieving negative feedback adjustment so that the initial acquisition signal output by the comparator can reduce the influence of interference signals. Furthermore, when performing feedback, the sampling module inverts the initial acquisition signal output by the comparator, and the output module further inverts the feedback signal generated by the sampling module, thereby obtaining a target acquisition signal with the same level as the initial acquisition signal output by the comparator. The target acquisition signal is then used as the final acquired signal output.

[0055] In the aforementioned PWM signal acquisition circuit, the comparator outputs a high-level initial acquisition signal when the initial PWM signal voltage is greater than the reference voltage, and a low-level initial acquisition signal when the initial PWM signal voltage is less than the reference voltage. When the comparator outputs a high-level initial acquisition signal, the voltage of the initial acquisition signal is determined by the comparator's operating voltage (supply voltage). Since the comparator's operating voltage is relatively small, when faced with an initial PWM signal with a large amplitude, the comparator processes the signal to convert it into a target acquisition signal with a smaller voltage amplitude, thus achieving step-down acquisition of the initial PWM signal.

[0056] During the buck acquisition process, on the one hand, a noise reduction module is connected to the comparator to reduce the noise generated during operation, thereby improving the signal-to-noise ratio of the initial acquisition signal output by the comparator and thus improving signal accuracy. On the other hand, a negative feedback signal obtained through the sampling and filtering modules is re-inputted to the inverting input of the comparator, thereby achieving negative feedback adjustment so that the initial acquisition signal output by the comparator can reduce the influence of interference signals. By using the noise reduction module to improve the signal-to-noise ratio and the filtering module to reduce the influence of interference signals, the accuracy of the signal during the buck acquisition of the PWM signal is improved.

[0057] Furthermore, in scenarios involving PWM signal control testing of automobiles, multiple PWM signals often require acquisition. Therefore, this application employs dual-channel components, enabling the integration of two PWM signal acquisition circuits onto a single board. The following section provides a detailed explanation of the structure of each module within a single PWM signal acquisition circuit and the connections between them.

[0058] In one embodiment, the comparator uses an integrated chip U0; in one example, the connection relationship of each terminal of the comparator is further illustrated using a comparator chip of model LM311DR2G.

[0059] Specifically, such as Figure 2 As shown, the non-inverting input (IN+) of comparator U0 is connected to a protection resistor R6 and a pull-up resistor R9. The first end of the pull-up resistor R9 is connected to the non-inverting input (IN+) of comparator U0, the second end of the pull-up resistor R9 is connected to the second end of the protection resistor R6, and the first end of the protection resistor R6 is connected to the initial PWM signal ECU0.

[0060] The VCC pin of comparator U0 is the power supply pin, connected to the operating voltage (+15V). To stabilize the operating voltage, a filter capacitor C7 is also connected to the VCC pin; the first terminal of capacitor C7 is connected to the VCC pin, and the second terminal is grounded. The VEE pin of the comparator is the negative power supply pin, used to connect to the -15V operating voltage; a filter capacitor is also connected to the VEE pin; the first terminal of filter capacitor C4 is connected to the VEE pin, and the second terminal of filter capacitor C4 is grounded. The GND pin of comparator U0 is grounded to provide a reference zero potential.

[0061] The Storbe pin of comparator U0 is the enable pin, and the Balance pin is the balance pin. Both the Storbe pin and the Balance pin are connected to a high-level operating voltage (+15V). Connecting the enable pin to a high level enables the comparator to work normally, so as to determine whether the initial acquisition signal of the output is high or low level according to the relationship between the reference voltage and the initial PWM signal. Connecting the balance pin to a high level is used to minimize the input offset voltage of the comparator. It can compensate for the offset between the output and the input by finely adjusting the current balance of the differential pair inside the comparator chip.

[0062] Furthermore, the IN+ pin of comparator U0 is a non-inverting input terminal, used to connect the acquired initial PWM signal; the IN- pin of comparator U0 is an inverting input terminal, used to connect the reference voltage.

[0063] In one embodiment, the noise reduction module includes a noise reduction capacitor C6, a noise reduction resistor R12, and a capacitor C8, wherein: the noise reduction capacitor C6 is connected in series between the output terminal (OUT) and the non-inverting input terminal (IN+) of the comparator U0; the capacitance of the noise reduction capacitor C6 is in the pF range, specifically 3.3pF; the first terminal of the noise reduction resistor R12 is connected to the output terminal (OUT) of the comparator U0, and the second terminal is used to input the excitation voltage (+5V); furthermore, the second terminal of the noise reduction resistor R12 is connected to the first terminal of the capacitor C8, and the second terminal of the capacitor C8 is grounded.

[0064] In one embodiment, the sampling module and the output module are implemented by an integrated chip U2; the integrated chip U2 integrates multiple inverters. The following uses the integrated chip U2, model number MC74ACT14DR2G, as an example to further illustrate the connection relationship between the integrated chip U2 and the comparator U0.

[0065] like Figure 2As shown, pins A1 and Y1 of integrated chip U2 are respectively a pair of input and output terminals of an inverter; that is, a signal input to pin A1 will output a signal with the opposite level at pin Y1. Similarly, pins A2 and Y2, A3 and Y3, and A4 and Y4 of integrated chip U2 are each a pair of input and output terminals of an inverter.

[0066] The A1 and Y1 pins of integrated chip U2 are equivalent to the sampling module; specifically, the A1 pin of integrated chip U2 is connected to the output (OUT) of comparator U0, and the Y1 pin of integrated chip U2 is connected to the filtering module.

[0067] In one embodiment, such as Figure 2 As shown, the filtering module includes a filter capacitor C5 and two filter resistors connected in parallel with the filter capacitor; wherein the two filter resistors are filter resistor R11 and resistor R10, respectively.

[0068] Specifically, the filter capacitor C5, filter resistor R10, and filter resistor R11 are connected in parallel; and after parallel connection, there are two common connection terminals, G1 and G2. Among them, the common connection terminal G2 serves as the input terminal of the filter module and is connected to the Y1 pin of the integrated chip U2. The common connection terminal G1 serves as the output terminal of the filter module and is connected to the inverting input terminal (IN-) of the comparator U0.

[0069] The initial acquisition signal output from the output terminal (OUT) of comparator U0 is input to pin A1 of integrated chip U2. Integrated chip U2 inverts the initial acquisition signal input from pin A1 and outputs an inverted sampling signal from pin Y1. This sampling signal is input to the filtering module via pin G2. The filtering module filters the sampling signal to obtain a negative feedback signal, which is output from the common connection terminal G1 of the filtering module and input to the inverting input terminal (IN-) of comparator U0 to achieve negative feedback.

[0070] The following further explains how the output module equivalent to the integrated chip U2 is implemented. For example... Figure 2 As shown, pin Y1 of integrated chip U2 is connected to pin A2, allowing the sampling signal output from pin Y1 to be input into the inverter equivalent to pins A2 and Y2. The output of pin Y2 then has a signal level opposite to the sampling signal input to pin A2. The target acquisition signal level is consistent with the initial acquisition signal level output from the output (OUT) of comparator U0. The signal output from pin Y2 of integrated chip U2 is the final target acquisition signal.

[0071] Furthermore, the output module is also connected to a protection resistor R13, wherein the first end of the protection resistor is connected to the Y2 pin of the integrated chip U2, and the second end of the protection resistor R13 is the output target acquisition signal.

[0072] In one embodiment, in order to broaden the amplitude range of the initial PWM signal that the PWM signal acquisition circuit can acquire, a reference module is required to provide a variable reference voltage. In another embodiment, the structure of the reference module is further described in detail.

[0073] like Figure 3 As shown, the reference module includes a voltage switching module, an amplifier, and a proportional adjustment module. The voltage switching module is used to receive multiple threshold voltages and connect them to the non-inverting input of the amplifier. The voltage switching module controls the switching between each threshold voltage and the non-inverting input of the amplifier. The output of the amplifier is connected to the inverting input of the comparator to amplify the threshold voltages, obtaining the reference voltage input to the inverting input of the comparator. The proportional adjustment module is connected to the output and inverting input of the amplifier to adjust the amplification ratio of the amplifier.

[0074] Specifically, the voltage switching module includes multiple switching switches for connecting multiple threshold voltages; each threshold voltage is connected to the non-inverting input of an amplifier via a switching switch. Furthermore, among the multiple threshold voltages connected to the voltage switching module, at least one is a constant internal threshold voltage and at least one is a variable external threshold voltage.

[0075] The voltage switching module can be implemented using a chip SW0 that integrates multiple switching switches. Taking the integrated chip SW0 with five parallel switching switches as an example, the connection relationship of the voltage switching module is further explained when the voltage switching module is connected to only one internal threshold voltage and one external threshold voltage.

[0076] like Figure 4 As shown, the integrated chip SW0 has five sets of pins: 1 and 10, 2 and 9, 3 and 8, 4 and 7, and 5 and 6. Two pins in each set act as the two ends of a switching switch. Specifically, pin 1 of the integrated chip SW0 is grounded, pin 10 is connected to the non-inverting input of comparator U0, pin 2 is connected to the external threshold voltage ref0, and pin 9 is connected to pin 10.

[0077] Furthermore, pin 4 of the integrated chip SW0 is connected to the internal threshold voltage (+5V), while pin 7 is connected to the non-inverting input of the amplifier; at the same time, pin 2 of the integrated chip SW0 is also connected to pin 3, and pin 8 is connected to pin 7.

[0078] like Figure 4 As shown, when pins 1 and 10 are on, and pins 4 and 7 are on, the voltage switching module outputs an internal threshold voltage to the non-inverting input of the amplifier. When pins 1 and 10 are on, and pins 3 and 8 are on, the voltage switching module outputs an external threshold voltage to the non-inverting input of the amplifier.

[0079] In one embodiment, the amplifier can be a single amplifier element or an integrated amplifier chip that integrates two isolated amplifiers. In one embodiment, this application uses an integrated amplifier chip U1 of model number AD823ARZ, wherein the two amplifiers integrated within the integrated amplifier chip U1 can each be connected to a PWM signal acquisition circuit.

[0080] like Figure 4 As shown, the V+ and V- pins of the integrated amplifier chip U1 are respectively input with operating voltages of +15V and -15V.

[0081] The IN1-, IN1+, and OUT1 pins of the integrated amplifier chip U1 are the inverting input, non-inverting input, and output of an internal amplifier, respectively. A protective resistor R3 is connected in series between the IN1+ pin of the integrated amplifier chip U1 and pin 6 of the integrated chip SW0 to limit the input current. A proportional adjustment module is connected between the IN1- and OUT1 pins of the integrated amplifier chip U1. Protective resistors R7 and R8 are connected in series between the output (OUT1) of the integrated amplifier chip U1 and the inverting input (IN-) of the comparator U0.

[0082] In one embodiment, the proportional adjustment module includes a switching switch, a first resistor, and a second resistor, wherein: the first resistor is connected between the output terminal of the amplifier and the inverting input terminal of the amplifier; the first terminal of the switching switch is grounded, and the second terminal is connected in series with the second resistor between the second terminal and the inverting input terminal of the amplifier.

[0083] Specifically, the switching switch in the proportional adjustment module can directly use pins 5 and 6 of the integrated chip SW0; pin 5 of the integrated chip SW0 is grounded, pin 6 is connected to the first end of the first resistor R2, and the second end of the first resistor R2 is connected to the inverting input terminal (IN1-) of the integrated amplifier chip U1; the first end of the second resistor R5 is connected to the inverting input terminal (IN1-) of the integrated amplifier chip U1, and the second end is connected to the output terminal (OUT1) of the integrated amplifier chip U1.

[0084] Specifically, when pins 5 and 6 are on, the amplifier amplifies the applied threshold voltage by 1.5 times; when pins 5 and 6 are off, the amplifier amplifies the applied threshold voltage by 0.5 times.

[0085] The reference module can provide two different threshold voltages and two different reference ratios, thus allowing the reference voltage output to comparator U0 to have multiple possibilities. This greatly improves the amplitude range of the initial PWM signal that the PWM signal acquisition circuit can acquire.

[0086] Furthermore, a protection resistor R1 is connected in series between pin 10 of the integrated chip SW0 and the first terminal of the protection resistor R6. Additionally, a pull-down resistor R4 and a voltage regulator capacitor C1 are connected to the non-inverting input terminal of the integrated amplifier chip U1. Figure 4 As shown, the first end of the pull-down resistor R4 is connected to the non-inverting input terminal (IN1+) of the integrated amplifier chip U1, and the second end is grounded (GND); the first end of the voltage regulator capacitor C1 is connected to the non-inverting input terminal (IN1+) of the integrated amplifier chip U1, and the second end is grounded (GND).

[0087] Furthermore, the non-inverting input terminal (IN1+) of the integrated amplifier chip U1 and the second terminal of the protection resistor R6 are both connected to a reference zero potential. This reference zero potential is achieved using one or two diodes; specifically, as shown... Figure 4 As shown, the cathodes of the two diodes connected in series are supplied with a +15V voltage, and the anodes are supplied with a -15V voltage. The end where the two diodes are connected provides the reference zero potential.

[0088] Furthermore, another amplifier integrated in the integrated amplifier chip U1 can be used as an amplifier in another PWM signal acquisition circuit; and other inverters of equivalent efficiency in the integrated chip U2 can be used as sampling and output modules in another PWM signal acquisition circuit; no example of another PWM sampling circuit is given here.

[0089] The PWM signal acquisition circuit provided in this embodiment can acquire an initial PWM signal with a frequency range of 0.03Hz to 100KHz and a duty cycle range of 0 to 100%; wherein the frequency error is <0.1% and the duty cycle error is <1%.

[0090] In one exemplary embodiment, this application provides a testing device; wherein the testing device includes a PWM signal acquisition circuit as described in any of the embodiments of the PWM signal acquisition circuit described above; specifically, the acquisition device includes a board, and at least two sets of components and integrated chips corresponding to the PWM signal acquisition circuits described above are connected and fixed on a carrier board. That is, a testing device includes at least one board, and at least two sets of PWM signal acquisition circuits are configured on the board.

[0091] In one exemplary embodiment, this application also provides a test system, which includes an NI chassis and a test device. The test device includes at least one board, and the board is configured with at least two PWM signal acquisition circuits as described in the above PWM signal acquisition circuit embodiment.

[0092] Specifically, the acquisition device is used to acquire an initial PWM signal, and after stepping down the initial acquired PWM signal to obtain a target PWM signal, the target PWM signal is output to the NI chassis.

[0093] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A PWM signal acquisition circuit, characterized in that, The circuit includes a reference module, a comparator, a sampling module, a filtering module, a noise reduction module, and an output module, wherein: The reference module is connected to the inverting input of the comparator and is used to provide a reference voltage; The noise reduction module is connected to the comparator and is used to perform noise reduction processing on the signal processing of the comparator. The non-inverting input of the comparator is used to input the initial PWM signal to be acquired; the output of the comparator outputs the initial acquisition signal according to the relationship between the reference voltage and the initial PWM signal. The sampling module is connected to the output of the comparator and is used to invert the initial acquisition signal to obtain the sampling signal; The filtering module is connected to the sampling module and the inverting input of the comparator; the filtering module is used to filter the sampled signal and input the resulting negative feedback signal to the inverting input of the comparator. The output module is connected to the sampling module and is used to invert the negative feedback signal to obtain the target acquisition signal and output it.

2. The circuit according to claim 1, characterized in that, The noise reduction module includes a noise reduction capacitor and a noise reduction resistor, wherein: The noise-reducing capacitor is connected in series between the output terminal and the non-inverting input terminal of the comparator; the capacitance of the noise-reducing capacitor is in the pF range. The first end of the noise reduction resistor is connected to the output of the comparator, and the second end is used to input the excitation voltage.

3. The circuit according to claim 1 or 2, characterized in that, The inverting input of the comparator is connected to a pull-down resistor.

4. The circuit according to claim 1, characterized in that, The filtering module includes a filtering capacitor and two filtering resistors connected in parallel with the filtering capacitor.

5. The circuit according to claim 1, characterized in that, The reference module includes a voltage switching module, an amplifier, and a proportional adjustment module, wherein: The voltage switching module is used to receive multiple threshold voltages and connect to the non-inverting input terminal of the amplifier; the voltage switching module is used to control the on / off connection between each threshold voltage and the non-inverting input terminal of the amplifier. The output of the amplifier is connected to the inverting input of the comparator to amplify the threshold voltage and obtain the reference voltage input to the inverting input of the comparator. The proportional adjustment module is connected to the output terminal and the inverting input terminal of the amplifier and is used to adjust the amplification ratio of the amplifier.

6. The circuit according to claim 5, characterized in that, The voltage switching module includes multiple switching switches; wherein, Each of the threshold voltages is connected to the non-inverting input of the amplifier via the switching switch; The threshold voltage includes at least one constant internal threshold voltage and at least one variable external threshold voltage.

7. The circuit according to claim 5, characterized in that, The proportional adjustment module includes a switch, a first resistor, and a second resistor, wherein: The first resistor is connected between the output terminal of the amplifier and the inverting input terminal of the amplifier; The first terminal of the switching switch is grounded, and the second terminal is connected in series with the second resistor between the second terminal and the inverting input terminal of the amplifier.

8. The circuit according to any one of claims 5-7, characterized in that, The non-inverting input of the amplifier is connected to a pull-down resistor and a voltage-regulating capacitor.

9. A testing device, characterized in that, The test equipment includes a PWM signal acquisition circuit as described in any one of claims 1-8.

10. A testing system, characterized in that, The test system includes an NI chassis and the acquisition device as described in claim 9; wherein the acquisition device is used to acquire an initial PWM signal, process the initial acquired PWM signal to obtain a target PWM signal, and output the target PWM signal to the NI chassis.

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