Multi-channel differential analog quantity signal acquisition circuit

Abstract

The invention relates to a multichannel differential analog quantity signal acquisition circuit, which comprises a single-ended signal to differential signal circuit, a filter circuit, a two-stage multichannel electronic gating switch circuit, a high-speed operational amplifier follower circuit, a differential operational amplifier conditioning circuit and an ADC (Analog to Digital Converter) acquisition conversion circuit which are connected in sequence, the single-ended signal-to-differential signal circuit is used for converting an externally input single-ended signal into an isolated differential signal; the filter circuit is used for filtering clutters; the two-stage multi-channel electronic gating switch circuit is formed by carrying out two-stage cascade connection on a plurality of electronic gating switches and is used for switching channels of different external signals; the high-speed operational amplifier follower circuit is used for improving the loading capacity of the signal; the differential operational amplifier conditioning circuit is used for conditioning the signal into an input range of the ADC acquisition conversion circuit through an external feedback loop; the ADC acquisition conversion circuit is used for converting analog signals into digital signals. The analog quantity acquisition function is high in precision, fast in speed and strong in anti-interference capability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of signal processing, and provides a signal acquisition circuit, in particular a multi-channel differential analog signal acquisition circuit. BACKGROUND

[0002] Analog signal acquisition circuit is a commonly used interface acquisition circuit in airborne computer system. In order to monitor the changes of analog signals such as external vibration sensor, temperature sensor, impact sensor, attitude control system, track control system and power voltage of airborne system, a multi-channel analog signal acquisition circuit is usually used to convert these analog signals into digital signals, and then transmit and process them on the bus.

[0003] In order to make the collected multi-channel analog signals have stronger anti-interference ability, support higher transmission rate, and ensure the accuracy and reliability of the signals, the external signals are usually converted into isolated differential signals first, and then switched by multi-channel electronic gating switch cascade mode circuit, and sent to ADC analog signal acquisition circuit for acquisition and processing after signal conditioning by operational amplifier conditioning circuit.

[0004] Airborne computer system generally requires analog signal acquisition function to have high precision and fast rate, and the types and numbers of analog signals to be collected are also many. At present, the analog signal acquisition signals of airborne computer system are mostly single-channel analog signal acquisition type. This mode has relatively weak anti-interference ability, and its precision and transmission rate will affect the stability and reliability of the whole airborne system operation, and the data transmission and acquisition rate is low in the process of processing a large amount of analog signal acquisition.

[0005] It can be seen that in a short acquisition time, the transmission rate of multi-channel differential analog signal acquisition and the conversion rate of AD chip acquisition are required to be higher. SUMMARY

[0006] To address the aforementioned technical problems, this invention proposes a multi-channel differential analog signal acquisition circuit, comprising a single-ended signal to differential signal conversion circuit, a filtering circuit, a two-stage multi-channel electronic gating switch circuit, a high-speed operational amplifier follower circuit, a differential operational amplifier conditioning circuit, and an ADC acquisition and conversion circuit connected in sequence. The single-ended signal to differential signal conversion circuit converts externally input single-ended signals into isolated differential signals; the filtering circuit filters out noise and removes high-frequency interference signals; the two-stage multi-channel electronic gating switch circuit consists of multiple cascaded electronic gating switches for switching between channels of different external signals; the high-speed operational amplifier follower circuit uses an operational amplifier to improve the signal's load-carrying capacity; the differential operational amplifier conditioning circuit conditions the signal to the input range of the ADC acquisition and conversion circuit through an external feedback loop; and the ADC acquisition and conversion circuit converts analog signals into digital signals.

[0007] Furthermore, the single-ended signal to differential signal circuit uses an ISO224 enhanced isolation amplifier and is used in conjunction with an isolated power supply.

[0008] Furthermore, the single-ended signal to differential circuit is set on the signal conditioning board and then connected to the signal acquisition board through an external interface connector.

[0009] Furthermore, the filter circuit adopts an RC first-order low-pass filter circuit, based on the cutoff frequency. Calculate and select RC parameters.

[0010] Furthermore, both stages of the multi-channel electronic gating switch circuit use the MUX507 analog multiplexer. The two gating signals of the first-stage electronic switch are connected to the input of the second-stage electronic switch, and the other channels of the second-stage electronic switch are input with external differential analog signals.

[0011] Furthermore, the differential operational amplifier conditioning circuit uses the ADA4932 differential amplifier.

[0012] Furthermore, the ADC acquisition and conversion circuit stores the digital signal in RAM.

[0013] This invention is applicable to circuit designs with multiple analog input acquisition channels; the multi-channel differential analog acquisition circuit has an acquisition error range of less than 30mV, strong anti-interference ability, high-speed transmission, and ensures the accuracy and reliability of the signal; moreover, the circuit is stable and reliable, the selected components are inexpensive and have low power consumption, which meets the current design requirements of low power consumption and low cost of products. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the principle of the present invention;

[0015] Figure 2This is a block diagram of a two-stage multi-channel electronic switch selection circuit. Detailed Implementation

[0016] To better understand the purpose, technical solution, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings. However, this invention can be implemented in many different ways as defined and covered by the claims. The accompanying drawings, which constitute a part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] This invention proposes a multi-channel differential analog signal acquisition circuit, comprising the following circuits connected in sequence: a single-ended signal to differential signal conversion circuit, a filtering circuit, a two-stage multi-channel electronic gating switch circuit, a high-speed operational amplifier follower circuit, a differential operational amplifier conditioning circuit, and an ADC acquisition and conversion circuit. Figure 1 As shown. The following is a detailed description of each circuit.

[0018] Part 1: Single-ended signal to differential signal circuit. An ISO224 enhanced isolation amplifier circuit is used to convert an externally input single-ended signal into an isolated differential signal.

[0019] The ISO224 is a precision isolation amplifier whose output and input circuitry are separated by a highly EMI-resistant isolation barrier, providing enhanced electrical isolation up to 5kVRMS, extremely long lifespan, and low power dissipation. When used in conjunction with an isolated power supply, this device can isolate components in a system operating at different common-mode voltage levels and prevent damage to lower-voltage components. The ISO224 circuitry can convert an external ±12V single-ended input signal into a ±4V differential output signal, offering enhanced noise immunity.

[0020] Part Two: Filtering Circuit. Typically, the single-ended to differential signal converter from Part One is located on the signal conditioning board, and then input to the signal acquisition board via an external interface connector. The input analog signal may contain or be interspersed with various interferences. A first-order RC low-pass filter circuit is used to filter out noise, eliminating high-frequency interference signals. The RC parameters can be selected based on its cutoff frequency. Calculate and select.

[0021] Part Three: Two-stage multi-channel electronic selection switch circuit. Both stages use MUX507 analog multiplexers, each providing 8 differential electronic selection channels.

[0022] The MUX507 offers faster switching times and lower on- and off-current leakage, allowing the multiplexer to switch signals transmitted from high input impedance sources with minimal error. To increase the number of input signals, a two-stage cascaded electronic switch design is employed. The block diagram of the two-stage multiplexer electronic switch selection circuit is shown below. Figure 2 As shown. The first-stage electronic switch uses two MUX507 chips, capable of inputting 16 differential signals. The two strobe signals of the first-stage electronic switch are then connected to the input terminals of the second-stage electronic switch. The remaining channels of the second-stage electronic switch can be used to input external differential analog signals. Figure 2 The connection method shown allows for the input of multiple differential analog signals.

[0023] A multi-channel electronic gating circuit can be composed of multiple electronic gating switches cascaded in two stages. The specific number used can be determined according to the actual number of signals. It is mainly used for channel acquisition and switching of different external signals.

[0024] Part Four: High-Speed ​​Operational Amplifier Follower Circuit. Utilizing the LTC6229 dual-channel, very high-speed, low-noise, rail-to-rail output, unity-gain stable operational amplifier, the follower circuit effectively improves the signal's load-carrying capacity.

[0025] Part 5: Differential Operational Amplifier Conditioning Circuit. The ADA4932 differential amplifier is used. This amplifier provides differential input and differential output amplification, with externally adjustable amplification factor, high speed, and single-supply voltage capability. Its internal common-mode feedback loop allows for adjustable output common-mode voltage. Based on the signal range acquired by the ADC, the signal can be conditioned through the external feedback loop of the operational amplifier to be within the ADC's input range for acquisition.

[0026] Part 6: ADC Acquisition and Conversion Circuit. The AD7961 chip is used. This chip is a 16-bit, 5MSPS, charge redistribution successive approximation low-power analog-to-digital converter. All conversion results can be obtained through a single LVDS self-clock or echo clock serial interface, making it a preferred solution for multiplexed channel applications.

[0027] The signal, conditioned by the differential operational amplifier, is input to the ADC chip for conversion. The AD7961 converts the differential voltage of the inverted analog input signals (IN+ and IN-) into digital output signals. IN+ and IN- require a REF / 2V common-mode voltage. The 16-bit conversion result is provided in MSB-first, two's complement format. Finally, the data from all channels is converted into digital signals and stored in the corresponding channel's RAM within the FPGA.

[0028] This invention converts single-ended input analog signals into differential analog signals using an isolation differential conversion circuit, thus increasing the signal's anti-interference performance. After filtering, the signal is sent to a high-precision analog multi-channel differential electronic switch circuit. By using a cascaded two-stage electronic switch, the number of input analog signals can be increased. The switching of the electronic switches is implemented by an FPGA. The output signal of the multi-channel switch is connected to a differential operational amplifier circuit for conditioning, and then sent to an AD conversion circuit. Finally, the data of all channels is converted into digital signals and stored in the RAM of the corresponding channels inside the FPGA.

[0029] To support higher signal transmission rates, the electronic switch uses the MUX507 analog multiplexer. This chip offers faster switching times and low on / off leakage current, allowing the multiplexer to convert signals from high input impedance sources with minimal error. Both the follower circuit operational amplifier LTC6229 and the differential conditioning circuit operational amplifier ADA4932 are high-speed, high-stability chips. The ADC is a 16-bit, 5MSPS, charge redistribution successive approximation low-power analog-to-digital converter chip, significantly improving the overall circuit performance.

[0030] This invention proposes a data acquisition circuit that converts single-ended analog signals into isolated differential analog signals. Multiple single-ended analog signals are input externally and converted into isolated differential analog signals through a differential output circuit. After filtering, these signals are connected to different high-precision analog multi-channel differential electronic switch circuits. The switching of the electronic switches is achieved by the programmable logic of the FPGA to select different channels. The output signals of the multi-channel switches are connected to a differential operational amplifier circuit for conditioning and then sent to an ADC acquisition and conversion circuit for acquisition. Finally, the data from all channels are converted into digital signals and stored in the RAM of the corresponding channels inside the FPGA.

[0031] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various changes or modifications within the scope of the claims, all of which should be included within the protection scope of the present invention.

Claims

1. A multi-channel differential analog signal acquisition circuit, characterized in that, The circuit comprises a single-ended signal to differential signal conversion circuit, a filtering circuit, a two-stage multi-channel electronic gating switch circuit, a high-speed operational amplifier follower circuit, a differential operational amplifier conditioning circuit, and an ADC acquisition and conversion circuit, connected in sequence. The single-ended signal to differential signal conversion circuit converts externally input single-ended signals into isolated differential signals. The filtering circuit filters out noise and removes high-frequency interference signals. The two-stage multi-channel electronic gating switch circuit consists of multiple cascaded electronic gating switches used to switch between channels of different external signals. The high-speed operational amplifier follower circuit uses an operational amplifier to improve the signal's load capacity. The differential operational amplifier conditioning circuit conditions the signal to the input range of the ADC acquisition and conversion circuit through an external feedback loop. The ADC acquisition and conversion circuit converts analog signals into digital signals.

2. The multi-channel differential analog signal acquisition circuit according to claim 1, characterized in that, The single-ended signal to differential signal circuit uses an ISO224 enhanced isolation amplifier and is used in conjunction with an isolated power supply.

3. The multi-channel differential analog signal acquisition circuit according to claim 1, characterized in that, The single-ended signal to differential circuit is set on the signal conditioning board and then connected to the signal acquisition board through an external interface connector.

4. The multi-channel differential analog signal acquisition circuit according to claim 1, characterized in that, The filter circuit uses a first-order RC low-pass filter circuit, based on the cutoff frequency. Calculate and select RC parameters.

5. The multi-channel differential analog signal acquisition circuit according to claim 1, characterized in that, Both the two-stage multi-channel electronic gating switch circuits use the MUX507 analog multiplexer. The two gating signals of the first-stage electronic switch are connected to the input of the second-stage electronic switch, and the other channels of the second-stage electronic switch are input with external differential analog signals.

6. The multi-channel differential analog signal acquisition circuit according to claim 1, characterized in that, The differential operational amplifier conditioning circuit uses the ADA4932 differential amplifier.

7. The multi-channel differential analog signal acquisition circuit according to claim 1, characterized in that, The ADC acquisition and conversion circuit stores digital signals in RAM.

Images