Loop resistance testing device and method based on AD chip

Abstract

The application relates to a loop resistance testing device and method based on an AD chip, and belongs to the technical field of testing. When a bridge wire in one path appears a disconnection fault, the overall path resistance value changes little, that is, the voltage change is small, and the problem of easy missed judgment or misjudgment is solved. The device comprises: a power supply circuit, the output end of which is connected with an AD acquisition circuit and a constant current source circuit and supplies power; a switch MOSFET is connected between the control power supply circuit and the constant current source circuit; the AD acquisition circuit is used for collecting loop voltage values and loop current values in a four-wire measurement circuit mode and providing the values to a switch control circuit and a resistor to be measured; the constant current source circuit is connected with the switch control circuit, generates a measurement current not greater than 10 mA, and provides the measurement current to the switch control circuit; and the switch control circuit is connected with the AD acquisition circuit and controls different relay switches to determine the loop resistance of a test security mechanism or the loop resistance of a pyrotechnic product. The loop resistance value is measured, and the problem of misfiring output during the loop resistance test of the pyrotechnic product can be effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of signal testing technology, and in particular to a loop resistance testing device and method based on an AD chip. Background Technology

[0002] During flight, launch vehicles use pyrotechnic ignition to achieve stage separation and fairing separation. Pyrotechnics are single-use devices, and a typical failure mode is an open circuit in the pyrotechnic bridge wire. To ensure the reliability of rocket flight, the resistance of the pyrotechnic bridge wire needs to be checked before launch to determine if an open circuit fault exists. (Pyrotechnics, also known as ignition devices, are devices containing gunpowder or explosives that, upon external stimulation, ignite or explode to ignite the gunpowder, detonate explosives, or perform mechanical work. They are single-use components and devices. Pyrotechnics include percussion caps, primers, ignition tubes, delay devices, detonators, detonating cords, fuses, and detonating cords.)

[0003] Traditional detection methods typically use an equivalent pyrotechnic device to simulate resistance. A small constant current source is connected to the downstream end of a timing relay as an excitation, generating voltage across the cable and the bridge wires of the pyrotechnic device. By repeatedly measuring this voltage value, a fault can be determined. The reference thresholds used to determine normal and fault conditions are traditionally fixed in the detection board in the form of circuitry or software. These are difficult to adjust, have poor adaptability to different ignition circuits or different batches of products, and pose safety hazards due to excessive energization cycles and prolonged cumulative time. Furthermore, pyrotechnic devices often use multiple bridge wires connected in parallel. When one bridge wire experiences an open circuit fault, the overall path resistance changes only slightly, resulting in a small voltage change and making it easy to miss or misdiagnose faults. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a loop resistance testing device and method based on an AD chip to solve the problem that when one of the bridge wires has an open circuit fault, the overall path resistance changes little, and therefore the voltage changes little, making it easy to miss or misjudge.

[0005] On one hand, embodiments of the present invention provide a loop resistance testing device based on an AD chip, comprising: a power supply circuit, the output of which is connected to an AD acquisition circuit and a constant current source circuit and supplies power to the AD acquisition circuit and the constant current source circuit; a switching MOSFET connected between the power supply circuit and the constant current source circuit; the AD acquisition circuit, used to acquire loop voltage and loop current values ​​in a four-wire measurement circuit mode and provide the loop voltage and loop current values ​​to a switch control circuit and the resistor under test, respectively; the constant current source circuit, connected to the switch control circuit, used to generate a measurement current of no more than 10mA and provide the measurement current to the switch control circuit; and the switch control circuit, connected to the AD acquisition circuit, used to control different relay switches to determine the loop resistance of a security mechanism or a pyrotechnic device.

[0006] The beneficial effects of the above technical solution are as follows: The design of the four-wire measurement mechanism, relay switch isolation test path and power distribution path can not only measure the circuit resistance value more accurately, but also effectively prevent accidental explosion output during the circuit resistance test of pyrotechnic products, improve the product testing capability, and thus improve the reliability of product operation.

[0007] Based on further improvements to the above-mentioned device, the four-wire measurement circuit is used to measure the voltage across the resistor under test and the current flowing through the resistor under test. The voltage of the resistor under test is measured by a voltmeter connected to the leads across the resistor under test, and the ratio of the measured voltage to the measured current is used by a processor as the circuit resistance of the security mechanism or the circuit resistance of the pyrotechnic device.

[0008] Based on a further improvement of the above-mentioned device, the power supply circuit includes a first power supply circuit, wherein the first power supply circuit is used to convert a first power supply voltage into a second power supply voltage, wherein the second power supply voltage is provided to the constant current source circuit after being isolated by a first ferrite bead; a fuse is connected between the first power supply circuit and the constant current source circuit.

[0009] Based on a further improvement of the above-mentioned device, the power supply circuit includes a second power supply circuit, wherein the second power supply circuit is used to convert the first power supply voltage into a third power supply voltage, the third power supply voltage being isolated by a second ferrite bead to power the digital terminal of the AD acquisition circuit, and the third power supply voltage being isolated by a third ferrite bead to power the analog terminal of the AD acquisition circuit.

[0010] Based on a further improvement of the above device, the power supply circuit includes a power conversion chip, comprising an input voltage pin, an enable pin, a noise reduction / soft-start pin, an output pin, a feedback pin, and a ground terminal. The input voltage pin and the enable pin are used to receive a first power supply voltage; the noise reduction / soft-start pin is grounded via a first capacitor; the output pin is used to output a converted second or third power supply voltage; the feedback pin is connected to the output pin via a second capacitor and is connected to the first end of a first resistor and a second resistor connected in series. The second end of the first resistor is connected to the output pin, and the second end of the second resistor is connected to the ground terminal.

[0011] Based on further improvements to the above-mentioned device, the AD acquisition circuit includes an AD acquisition chip, a reference power supply chip, and a magnetic isolation chip. The AD acquisition chip has a 24-bit SPI interface and acquires the loop current and loop voltage values ​​differentially. The AD acquisition chip receives the loop voltage value via nodes TEST_U1 and TEST_U2, and receives the loop current value via the voltage across a third resistor connected to node TEST_U2, and outputs the digital loop voltage and loop current values ​​in a serial, time-division multiplexing manner. The reference power supply chip generates a reference voltage and provides it to the reference voltage pin of the AD acquisition chip. The magnetic isolation chip isolates the digital loop voltage and loop current values ​​from the AD acquisition chip and provides the isolated digital loop voltage and loop current values ​​to the processor. When the chip select signal is valid, an inverter enables the output channel of the acquired data, allowing the acquired data to be provided to the processor via the 24-bit SPI interface.

[0012] Based on further improvements to the above-mentioned device, the AD acquisition chip includes analog input pins, digital output pins, a positive reference voltage pin, and a negative reference voltage pin. The analog input pins include two loop voltage input pins and two loop current input pins. The reference power supply chip includes a power input pin, a ground pin, and a reference voltage output pin. The two loop voltage input pins are connected to nodes TEST_U1 and TEST_U2 respectively via a fourth resistor and a fifth resistor. A first isolation capacitor is connected between the two loop voltage input pins, and they are grounded via a first filter capacitor and a second filter capacitor, respectively. The two loop current input pins are connected to the first and second terminals of a third resistor via a sixth resistor and a seventh resistor. The two loop current input pins are connected to a second isolation capacitor and grounded via a third filter capacitor and a fourth filter capacitor, respectively. The power input pin receives the second power supply voltage and is grounded via a third isolation capacitor. The reference voltage output pin is grounded via a fourth isolation capacitor and connected to the positive reference voltage pin of the AD acquisition chip. The positive reference voltage pin is connected to the negative reference voltage pin via a fifth isolation capacitor.

[0013] Based on further improvements to the above-mentioned device, the switch control circuit includes a first electromagnetic relay, a third electromagnetic relay, a fourth electromagnetic relay, a control terminal DJ1_relay, a control terminal TEST_R-, a control terminal FDR_relay, a node TEST_U1, and a node TEST_U2. When measuring the resistance of the security mechanism circuit, the control terminals DJ1_relay and TEST_R- are configured to low level to control the first electromagnetic relay K1 and the fourth electromagnetic relay K4 to connect to the security mechanism circuit, and the voltage of the security mechanism circuit between nodes TEST_U1 and TEST_U2 is measured. When measuring the resistance of the pyrotechnic circuit, the control terminals FDR_relay and TEST_R- are configured to low level to control the third electromagnetic relay K3 and the fourth electromagnetic relay K4 to connect to the pyrotechnic circuit, and the voltage of the pyrotechnic circuit between nodes TEST_U1 and TEST_U2 is measured.

[0014] On the other hand, embodiments of the present invention provide a loop resistance testing method based on an AD chip, comprising: when the processor receives a start test command, controlling the switching MOSFET at the front end of the constant current source circuit to turn on, so as to supply power to the AD acquisition circuit and the constant current source circuit through the power supply circuit; acquiring the loop voltage value and the loop current value through the AD acquisition circuit in a four-wire measurement circuit mode and providing the loop voltage value and the loop current value to the switch control circuit and the resistor under test respectively; generating a measurement current of no more than 10mA through the constant current source circuit and providing the measurement current to the switch control circuit; and controlling different relay switches through the switch control circuit to determine the loop resistance of the security mechanism or the loop resistance of the pyrotechnic device.

[0015] Based on a further improvement of the above method, the voltage across the resistor under test and the current flowing through the resistor under test are measured by the four-wire measurement circuit. The voltage of the resistor under test is measured by a voltmeter connected to the leads across the resistor under test, and the ratio of the measured voltage to the measured current is used as the circuit resistance of the security mechanism or the circuit resistance of the pyrotechnic device by the processor.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0017] 1. When measuring the resistance of pyrotechnic devices using a four-wire measurement scheme, in order to minimize the impact of the circuit resistance on the measurement, it is necessary to measure the voltage and current values ​​across the resistor being measured separately. This method has high measurement accuracy and strong adaptability.

[0018] 2. The selected AD acquisition method is differential acquisition with built-in gain, and the measurement range is 0Ω~99Ω. It is suitable for small resistance values ​​of bridge wires in pyrotechnics and security institutions, with strong anti-interference ability and high accuracy.

[0019] 3. The precision constant current source is designed with a switching MOSFET at the front end, so that the test circuit is not energized when the circuit resistance is not being measured, thereby eliminating the influence of the test circuit on the power distribution path and reducing the power consumption of the product.

[0020] 4. The test circuit uses an electromagnetic relay. When the relay is disconnected, the test circuit is physically isolated from the power distribution channel, ensuring that the power distribution function is not affected by the circuit resistance test, thereby providing product reliability and safety.

[0021] 5. The precision constant current source is designed as a 10mA constant current source, which can control the current of the test circuit to not exceed 10mA, effectively preventing accidental detonation during the resistance test of the pyrotechnic circuit.

[0022] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0023] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0024] Figure 1 This is a circuit framework structure topology diagram of an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a loop resistance testing device based on an AD chip according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram illustrating the principle of a four-wire resistance measurement according to an embodiment of the present invention;

[0027] Figure 4 This is a circuit diagram of a power supply circuit according to an embodiment of the present invention;

[0028] Figure 5 This is a circuit diagram of the second power supply circuit according to an embodiment of the present invention;

[0029] Figure 6 This is a schematic diagram of the constant current source circuit according to an embodiment of the present invention;

[0030] Figure 7 This is a schematic diagram of the AD acquisition circuit according to an embodiment of the present invention;

[0031] Figure 8 This is a schematic diagram of the switch control circuit according to an embodiment of the present invention;

[0032] Figure 9 This is a flowchart of a loop resistance testing method based on an AD chip according to an embodiment of the present invention. Detailed Implementation

[0033] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0034] refer to Figure 1 and Figure 2A specific embodiment of the present invention discloses a loop resistance testing device based on an AD chip, comprising: a power supply circuit 101, the output of which is connected to an AD acquisition circuit 102 and a constant current source circuit 103 and supplies power to the AD acquisition circuit and the constant current source circuit; a switching MOSFET 104 connected between the power supply circuit 101 and the constant current source circuit 103; an AD acquisition circuit 102 for acquiring loop voltage and loop current values ​​in a four-wire measurement circuit mode and providing the loop voltage and loop current values ​​to a switch control circuit and the resistor under test, respectively; a constant current source circuit 103 connected to a switch control circuit 105 for generating a measurement current of no more than 10mA and providing the measurement current to the switch control circuit 105; and a switch control circuit 105 connected to the AD acquisition circuit 102 for controlling different relay switches to determine the loop resistance of a security mechanism or a pyrotechnic device.

[0035] Compared with the prior art, the loop resistance testing device based on AD chip provided in this embodiment adopts a four-wire measurement mechanism, a relay switch isolation test path, and a power distribution path design, which can not only measure the loop resistance value more accurately, but also effectively prevent accidental detonation output during the loop resistance test of pyrotechnic products, improve product testing capabilities, and thus improve the reliability of product operation.

[0036] The following text will refer to Figures 1 to 8 The loop resistance testing device based on an AD chip according to an embodiment of the present invention will be described in detail. The loop resistance testing device based on an AD chip includes a power supply circuit 101, an AD acquisition circuit 102, a constant current source circuit 103, a switching MOSFET 104, and a switching control circuit 105.

[0037] refer to Figure 4 and Figure 5 The output terminal of the power supply circuit 101 is connected to the AD acquisition circuit 102 and the constant current source circuit 103 and supplies power to the AD acquisition circuit and the constant current source circuit.

[0038] The power supply circuit 101 includes a first power supply circuit and a second power supply circuit. The first power supply circuit converts a first power supply voltage (e.g., 12V) to a second power supply voltage (e.g., 11V), wherein the second power supply voltage is isolated by a first ferrite bead FB2 and then provides a second power supply voltage to the constant current source circuit; a fuse is connected between the first power supply circuit and the constant current source circuit. The second power supply circuit converts the first power supply voltage (e.g., 12V) to a third power supply voltage (e.g., 5V), wherein the third power supply voltage is isolated by a second ferrite bead FB6 and then provides power to the digital terminal (i.e., FRD_D5V1) of the AD acquisition circuit, and is isolated by a third ferrite bead FB7 and then provides power to the analog terminal (i.e., AVCC5V1) of the AD acquisition circuit.

[0039] refer to Figure 4 and Figure 5 The first power supply circuit includes a first power conversion chip U28, and the second power supply circuit includes a second power conversion chip U33. The connection structure of the first power conversion chip U28 and the second power conversion chip U33 includes an input voltage (IN) pin, an enable (EN) pin, a noise reduction / soft-start (NR / SS) pin, an output (OUT) pin, a feedback (FB) pin, and a ground terminal (GND). The connection structure of the first power conversion chip U28 and the second power conversion chip U33 has both identical and different parts.

[0040] refer to Figure 4 In the first power conversion chip, the input voltage IN pin and the enable EN pin are used to receive the first power supply voltage AVCC12V, which is grounded via parallel capacitors C65 and C66, and also via Zener diode D38. The noise reduction / soft-start NR / SS pin is grounded via the first capacitor C72. The output OUT pin is used to output the converted second power supply voltage AVCC11V1. The feedback FB pin is connected to the output OUT pin via the second capacitor C60, and is connected to the first terminals of the first resistor R123 and the second resistor R127 connected in series. The second terminal of the first resistor R123 is connected to the output pin, and the second terminal of the second resistor R127 is connected to ground. The output OUT pin is grounded via capacitors C69 and C67.

[0041] refer to Figure 5 In the second power conversion chip U33, the input voltage IN pin and the enable EN pin are used to receive the first power supply voltage AVCC12V, which is grounded via parallel capacitors C84 and C85. The noise reduction / soft-start NR / SS pin is grounded via the first capacitor C97. The output OUT pin is used to output the converted second power supply voltage VCC5V1. The feedback FB pin is connected to the output OUT pin via capacitor C83, and is also connected to the first terminal of the first resistor R153 and the second resistor R155 connected in series. The second terminal of the first resistor R153 is connected to the output OUT pin, and the second terminal of the second resistor R155 is connected to ground. The output OUT pin is grounded via parallel capacitors C88 and C86.

[0042] The third power supply voltage VCC5V1, after being isolated by the second ferrite bead FB6, supplies power to the digital terminal of the AD acquisition circuit (i.e., FRD_D5V1). Capacitor R150 is connected between the second ferrite bead FB6 and the digital terminal FRD_D5V1. The digital terminal FRD_D5V1 is grounded via parallel capacitors C89, C90, C91, and C92.

[0043] The third power supply voltage VCC5V1, isolated by the third ferrite bead FB7, supplies power to the analog terminal of the AD acquisition circuit (i.e., AVCC5V1). Capacitor R151 is connected between the third ferrite bead FB7 and the analog terminal AVCC5V1. The analog terminal AVCC5V1 is grounded via parallel capacitors C93, C94, and C95.

[0044] The switching MOSFET 104 is connected between the power supply circuit 101 and the constant current source circuit 103. Specifically, the switching MOSFET 104 is connected between the fuse F1 and the constant current source circuit 103.

[0045] The AD acquisition circuit 102 is used to acquire loop voltage and loop current values ​​in a four-wire measurement circuit mode and provide the loop voltage and loop current values ​​to the switch control circuit and the resistor under test, respectively.

[0046] refer to Figure 3 The four-wire measurement circuit is used to measure the voltage across the resistor under test and the current flowing through the resistor under test. Specifically, the voltage of the resistor under test is measured by a voltmeter connected to the leads across the resistor under test, and the ratio of the measured voltage to the measured current is used by a processor as the circuit resistance of the security mechanism or the circuit resistance of the pyrotechnic device.

[0047] refer to Figure 7 The AD acquisition circuit 102 includes an AD acquisition chip U34, a reference power supply chip U38, and a magnetic isolation chip U40. The AD acquisition chip U34 has a 24-bit SPI interface, which acquires loop current and loop voltage values ​​differentially. Specifically, the AIN7 and AIN8 channels of the AD acquisition chip U34 receive loop voltage values ​​via nodes TEST_U1 and TEST_U2, while the AIN5 and AIN6 channels receive loop current values ​​via the voltage across a third resistor R143 connected to node TEST_U2. The DOUT / RD channels of the AD acquisition chip U34 output the loop voltage and loop current values ​​in digital form serially in a time-division multiplexing manner. The reference power supply chip U38 generates a reference voltage and provides it to the REFIN1+ pin of the AD acquisition chip.

[0048] The magnetic isolation chip U40 isolates the digital loop voltage and loop current values ​​from the AD acquisition chip and provides the isolated digital loop voltage and loop current values ​​to the processor. When the chip select signal CS is valid, the inverter U39 enables the output channel of the acquired data, so that the acquired data is provided to the processor via the 24-bit SPI MI interface.

[0049] The AD acquisition chip 102 includes analog input pins, digital output pins, a positive reference voltage REFIN1+ pin, and a negative reference voltage REFIN1- pin. The analog input pins include two loop voltage input pins AIN7 and AIN8 and two loop current input pins AIN5 and AIN6. The reference power supply chip includes a power input pin Vin, a ground pin GND, and a reference voltage output pin Vout. The two loop voltage input pins AIN7 and AIN8 are connected to nodes TEST_U1 and TEST_U2 respectively via a fourth resistor R154 and a fifth resistor R156. The two loop voltage input pins AIN7 and AIN8 are connected to a first isolation capacitor C98 and grounded via a first filter capacitor C96 and a second filter capacitor C100 respectively. The two loop current input pins AIN5 and AIN6 are decomposed and connected to the first and second terminals of the third resistor R143 via the sixth resistor R138 and the seventh resistor R144. The two loop current input pins AIN5 and AIN6 are connected to the second isolation capacitor C81 and grounded via the third filter capacitor C80 and the fourth filter capacitor C82, respectively.

[0050] The power input Vin pin receives the second power supply voltage AVCC11V1 and is grounded via the third isolation capacitors C104 and C105; the reference voltage output Vout pin is grounded via the fourth isolation capacitor C107 and connected to the positive reference voltage REFIN1+ pin of the AD acquisition chip.

[0051] The positive reference voltage REFIN1+ pin is connected to the negative reference voltage REFIN1- pin via the fifth isolation capacitor C87.

[0052] The constant current source circuit 103 is connected to the switch control circuit 105 and is used to generate a measurement current of no more than 10mA and provide the measurement current to the switch control circuit 105.

[0053] refer to Figure 8The switch control circuit 105 is connected to the AD acquisition circuit 102 and is used to control different relay switches to determine the circuit resistance of the security mechanism or the circuit resistance of the pyrotechnic device. The switch control circuit 105 includes a first electromagnetic relay K1, a third electromagnetic relay K3, and a fourth electromagnetic relay K4, a control terminal DJ1_relay, a control terminal TEST_R-, a control terminal FDR_relay, a node TEST_U1, and a node TEST_U2. When measuring the resistance of the security mechanism circuit, the control terminals DJ1_relay and TEST_R- are configured to low level to control the first electromagnetic relay K1 and the fourth electromagnetic relay K4 to connect to the security mechanism circuit, and the voltage of the security mechanism circuit between nodes TEST_U1 and TEST_U2 is measured. When measuring the resistance of the pyrotechnic circuit, the control terminals FDR_relay and TEST_R- are configured to low level to control the third electromagnetic relay K3 and the fourth electromagnetic relay K4 to connect to the pyrotechnic circuit, and the voltage of the pyrotechnic circuit between nodes TEST_U1 and TEST_U2 is measured.

[0054] refer to Figure 9 A specific embodiment of the present invention discloses a loop resistance testing method based on an AD chip, comprising: in step S901, supplying power to the AD acquisition circuit and the constant current source circuit through a power supply circuit; in step S902, acquiring the loop voltage value and the loop current value through the AD acquisition circuit in a four-wire measurement circuit mode and providing the loop voltage value and the loop current value to the switch control circuit and the resistor under test, respectively; in step S903, generating a measurement current of no more than 10mA through the constant current source circuit and providing the measurement current to the switch control circuit; and in step S904, controlling different relay switches through the switch control circuit to determine the loop resistance of the security mechanism or the loop resistance of the pyrotechnic device.

[0055] The voltage across the resistor under test and the current flowing through the resistor under test are measured by a four-wire measurement circuit. The voltage of the resistor under test is measured by a voltmeter connected to the leads across the resistor under test. The ratio of the measured voltage to the measured current is used by a processor as the circuit resistance of the security mechanism or the circuit resistance of the pyrotechnic device.

[0056] The following text will refer to Figures 1 to 8 The loop resistance testing device based on the AD chip according to the present invention will be described in detail.

[0057] The high-precision loop resistance test circuit based on a 24-bit AD chip includes a power supply circuit, an AD acquisition circuit, a constant current source circuit, and a switch control circuit. The power supply circuit supplies power to both the constant current source circuit and the AD acquisition circuit; the AD acquisition circuit acquires the loop voltage and current in a four-wire system; the constant current source circuit provides a measurement current of no more than 10mA to the measurement path; the switch control circuit switches different relay switches to test the loop resistance values ​​of different security mechanisms and pyrotechnic devices, as well as to physically isolate the test path from the power distribution path.

[0058] The high-precision loop resistance test circuit based on a 24-bit AD chip describes the following resistance test process: After receiving the start test command, the processor controls the switching MOSFET at the front end of the constant current source circuit to turn on, and the constant current source circuit outputs a current of 10mA. Then, the electromagnetic relays for the security mechanism path and the electromagnetic relays for the pyrotechnic path are turned on sequentially at a frequency of 1 second to measure the loop resistance of the security mechanism path and the resistance of the pyrotechnic path in sequence. Finally, the voltage value (converted to loop current) and the loop voltage value collected by the ADC are sent to the processor for analysis to obtain the loop resistance value.

[0059] The AD acquisition circuit uses a 24-bit ADC chip with built-in gain and precision resistors with an accuracy of 1%, which enables the resistance acquisition accuracy to reach ±0.1Ω.

[0060] The safety and reliability design ensures that the power distribution function is not affected by the circuit resistance test by physically isolating the test circuit from the power distribution channel when the relay is disconnected. The constant current source mode is adopted, and the circuit resistance test current is no more than 10mA, which effectively prevents accidental detonation during the circuit resistance test of pyrotechnics. At the same time, a self-resetting fuse is designed as another barrier to prevent dangerous overcurrent faults caused by damage to the constant current source circuit.

[0061] like Figure 1 and 2 As shown, the present invention includes a power supply circuit 1, a 50mA resettable fuse, a test circuit to start the MOSFET switch, a power supply circuit 2, an AD acquisition circuit, and a switch control circuit.

[0062] like Figure 1 and Figure 2 As shown, this invention uses a MOSFET switch to control the start-up circuit resistance test process. When the processor receives the start test command sent by the upper level, it controls the MOSFET to turn on, the subsequent constant current source is powered on, and the test process begins.

[0063] like Figure 3As shown, to achieve the high-precision internal resistance measurement required by the task, a four-wire low-current resistance measurement scheme is necessary. When a small current flows through the entire test circuit, a voltage drop will occur across all loop resistors, Uad > Ubc. To minimize the impact of loop resistors R1 and R2 on the measurement, the power supply current loop and the measurement loop must be separated as much as possible. The four-wire resistance measurement principle meets this requirement. During normal operation, by simultaneously detecting the current in the constant current source test circuit and the terminal voltage across the resistor Rx measured using the four-wire system, the required resistance value of the pyrotechnic device can be obtained by dividing the obtained voltage by the current within the processing unit.

[0064] like Figure 4 As shown, power supply circuit 1 uses a TPS7A4901 power conversion chip U28 to convert 12V voltage to 11V voltage, which is then isolated by a ferrite bead FB2 to power the constant current source circuit. A 50mA resettable fuse F1 is connected after the ferrite bead FB2 to limit the test circuit current to within 50mA, preventing dangerous overcurrent faults caused by damage to the downstream constant current source circuit.

[0065] like Figure 5 As shown, power supply circuit 2 uses a TPS7A4901 power conversion chip U33 to convert 12V voltage to 5V voltage to power the AD acquisition circuit. The output voltage VCC5V1 is isolated by ferrite bead FB6 to output FRD_D5V1 to power the digital terminal of the ADC chip, and isolated by ferrite bead FB7 to output AVCC5V1 to power the analog terminal of the ADC chip, effectively enhancing the anti-interference characteristics of the AD acquisition circuit.

[0066] like Figure 6 As shown, the constant current source circuit consists of a reference voltage source chip REF191ES and a precision resistor. The voltage source U29 outputs a voltage of 2.048V±2mV. After connecting a 205Ω precision resistor R126, the resulting constant current source current is approximately 2.048 / 205≈10mA, which can provide a measurement current of no more than 10mA for the measurement path to prevent accidental ignition of pyrotechnic devices.

[0067] like Figure 7As shown, the AD acquisition circuit consists of an AD acquisition chip AD7193 (U34), a reference power supply chip (U38), a 10Ω precision resistor (R143), a magnetic isolation chip ADUM1401CRWZ (U40), and peripheral circuits for the above chips. U34 is a 24-bit SPI interface Σ-Δ ADC with built-in gain, with a gain set to 16 times. It acquires the current and voltage values ​​of the loop in a differential manner. The voltage between network labels TEST_U1 and TEST_U2 is the loop voltage value, and the voltage across R143 divided by 10 is the loop current value. The data DOUT acquired by U34 is isolated by U40 and then sent to the processor for parsing and processing. The DOUT signal is controlled by the chip select signal CS of U34 when it is sent to the processor. When the chip select signal of U34 is valid (i.e., when the ADC FDR CS chip select signal of U34 is valid, the processor provides the SPI CLK 0 and SPI MO signals), the output channel of DOUT is enabled through inverter U39, and then the acquired data is sent to the processor. U38 is a 4.096V voltage reference chip that provides a stable reference voltage for U34 to meet measurement accuracy requirements.

[0068] like Figure 8 As shown, the switch control circuit consists of electromagnetic relays K1, K3, and K4. When measuring the resistance of the security mechanism circuit (e.g., the security mechanism circuit resistance is 0–100 ohms, preferably 100 ohms), the control terminals DJ1_relay and TEST_R- must be configured to low level. When K1 and K4 are turned on, the voltage between TEST_U1 and TEST_U2 is the security mechanism circuit voltage. When measuring the resistance of the pyrotechnic circuit (e.g., the pyrotechnic circuit resistance is 0–10 ohms, preferably 10 ohms), the control terminals FDR_relay and TEST_R- must be configured to low level. When K3 and K4 are turned on, the voltage between TEST_U1 and TEST_U2 is the pyrotechnic circuit voltage. The circuit resistance test circuit achieves different circuit resistance values ​​by switching the above electromagnetic relay switches.

[0069] Those skilled in the art will understand that all or part of the processes of the methods described in the above embodiments can be implemented by a computer program instructing related hardware, and the program can be stored in a computer-readable storage medium. The computer-readable storage medium may be a disk, optical disk, read-only memory, or random access memory, etc.

[0070] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A loop resistance testing device based on an AD chip, characterized in that, include: A power supply circuit, the output of which is connected to the AD acquisition circuit and the constant current source circuit and supplies power to the AD acquisition circuit and the constant current source circuit; A switching MOSFET is connected between the power supply circuit and the constant current source circuit; The AD acquisition circuit is used to acquire the loop voltage value and the loop current value in a four-wire measurement circuit mode and provide the loop voltage value and the loop current value to the switch control circuit and the resistor under test, respectively. The constant current source circuit is connected to the switch control circuit and is used to generate a measurement current of no more than 10mA and provide the measurement current to the switch control circuit. as well as The switch control circuit, connected to the AD acquisition circuit, is used to control different relay switches to determine the circuit resistance of the security mechanism or the pyrotechnic device. The use of a four-wire measurement circuit and the isolation of the test path and power distribution path by the relay switches not only measures the circuit resistance value but also effectively prevents accidental detonation during pyrotechnic device circuit resistance testing. The switch control circuit includes a first electromagnetic relay, a third electromagnetic relay, a fourth electromagnetic relay, a control terminal DJ1_relay, a control terminal TEST_R-, a control terminal FDR_relay, a node TEST_U1, and a node TEST_U2. Specifically, when measuring the resistance of the security mechanism circuit, the control terminals DJ1_relay and TEST_R- are configured to low level to control the first electromagnetic relay K1 and the fourth electromagnetic relay K4 to connect with the security mechanism circuit, and the voltage of the security mechanism circuit between nodes TEST_U1 and TEST_U2 is measured; when measuring the resistance of the pyrotechnic circuit, the control terminals FDR_relay and TEST_R- are configured to low level to control the third electromagnetic relay K3 and the fourth electromagnetic relay K4 to connect with the pyrotechnic circuit, and the voltage of the pyrotechnic circuit between nodes TEST_U1 and TEST_U2 is measured.

2. The loop resistance testing device based on an AD chip according to claim 1, characterized in that, The four-wire measurement circuit is used to measure the voltage across the resistor under test and the current flowing through the resistor under test. The voltage of the resistor under test is measured by a voltmeter connected to the leads across the resistor under test, and the ratio of the measured voltage to the measured current is used by a processor as the circuit resistance of the security mechanism or the circuit resistance of the pyrotechnic device.

3. The loop resistance testing device based on an AD chip according to claim 2, characterized in that, The power supply circuit includes a first power supply circuit, wherein... The first power supply circuit is used to convert the first power supply voltage into a second power supply voltage, wherein the second power supply voltage is provided to the constant current source circuit after being isolated by the first ferrite bead; the fuse is connected between the first power supply circuit and the constant current source circuit.

4. The loop resistance testing device based on an AD chip according to claim 3, characterized in that, The power supply circuit includes a second power supply circuit, wherein... The second power supply circuit is used to convert the first power supply voltage into a third power supply voltage. The third power supply voltage is isolated by the second ferrite bead and then used to power the digital terminal of the AD acquisition circuit, and the third power supply voltage is isolated by the third ferrite bead and then used to power the analog terminal of the AD acquisition circuit.

5. The loop resistance testing device based on an AD chip according to claim 3, characterized in that, The power supply circuit includes a power conversion chip, comprising an input voltage pin, an enable pin, a noise reduction / soft-start pin, an output pin, a feedback pin, and a ground terminal. The input voltage pin and the enable pin are used to receive the first power supply voltage; The noise reduction / soft start pin is grounded via the first capacitor; The output pin is used to output the converted second or third power supply voltage; The feedback pin is connected to the output pin via a second capacitor, and is connected to the first end of a first resistor and a second resistor connected in series. The second end of the first resistor is connected to the output pin, and the second end of the second resistor is connected to the ground terminal.

6. The loop resistance testing device based on an AD chip according to claim 5, characterized in that, The AD acquisition circuit includes an AD acquisition chip, a reference power supply chip, and a magnetic isolation chip, wherein... The AD acquisition chip has a 24-bit SPI interface to acquire the loop current value and the loop voltage value in a differential manner. The AD acquisition chip receives the loop voltage value via nodes TEST_U1 and TEST_U2, receives the loop current value via the voltage across the third resistor connected to node TEST_U2, and outputs the loop voltage value and loop current value in digital form in a serial manner in a time-division multiplexing manner. The reference power chip is used to generate a reference voltage and provide the reference voltage to the reference voltage pin of the AD acquisition chip; The magnetic isolation chip is used to isolate the digital loop voltage and loop current values ​​from the AD acquisition chip, and to provide the isolated digital loop voltage and loop current values ​​to the processor. When the chip select signal is valid, the output channel of the acquired data is enabled by an inverter, so that the acquired data is provided to the processor via the 24-bit SPI interface.

7. The loop resistance testing device based on an AD chip according to claim 6, characterized in that, The AD acquisition chip includes analog input pins, digital output pins, a positive reference voltage pin, and a negative reference voltage pin. The analog input pins include two loop voltage input pins and two loop current input pins. The reference power supply chip includes a power input pin, a ground pin, and a reference voltage output pin; wherein... The two loop voltage input pins are connected to nodes TEST_U1 and TEST_U2 respectively via the fourth resistor and the fifth resistor. The two loop voltage input pins are connected to the first isolation capacitor and grounded via the first filter capacitor and the second filter capacitor respectively. The two loop current input pins are connected to the first and second ends of the third resistor via the sixth and seventh resistors, respectively. The two loop current input pins are connected to the second isolation capacitor and grounded via the third and fourth filter capacitors, respectively. The power input pin receives the second power supply voltage and is grounded via the third isolation capacitor; the reference voltage output pin is grounded via the fourth isolation capacitor and connected to the positive reference voltage pin of the AD acquisition chip. The positive reference voltage pin is connected to the negative reference voltage pin via a fifth isolation capacitor.

8. A method for testing loop resistance based on an AD chip, characterized in that, include: When the processor receives the start test command, it controls the switching MOSFET at the front end of the constant current source circuit to turn on, so as to supply power to the AD acquisition circuit and the constant current source circuit through the power supply circuit. The AD acquisition circuit acquires the loop voltage and loop current values ​​in a four-wire measurement circuit manner and provides the loop voltage and loop current values ​​to the switch control circuit and the resistor under test, respectively. The constant current source circuit generates a measurement current of no more than 10mA and provides the measurement current to the switch control circuit. as well as The switch control circuit controls different relay switches to determine the resistance of the security mechanism circuit or the pyrotechnic circuit. The use of a four-wire measurement circuit, along with the relay switches isolating the test path and the power distribution path, not only measures the resistance value of the security mechanism circuit but also prevents accidental detonation during the pyrotechnic circuit resistance test. The switch control circuit includes a first electromagnetic relay, a third electromagnetic relay, a fourth electromagnetic relay, a control terminal DJ1_relay, a control terminal TEST_R-, a control terminal FDR_relay, a node TEST_U1, and a node TEST_U2. Specifically, when measuring the resistance of the security mechanism circuit, the control terminals DJ1_relay and TEST_R- are configured to low level to control the first electromagnetic relay K1 and the fourth electromagnetic relay K4 to connect with the security mechanism circuit, and the voltage of the security mechanism circuit between nodes TEST_U1 and TEST_U2 is measured; when measuring the resistance of the pyrotechnic circuit, the control terminals FDR_relay and TEST_R- are configured to low level to control the third electromagnetic relay K3 and the fourth electromagnetic relay K4 to connect with the pyrotechnic circuit, and the voltage of the pyrotechnic circuit between nodes TEST_U1 and TEST_U2 is measured.

9. The loop resistance testing method based on an AD chip according to claim 8, characterized in that, The circuit measures the loop voltage across the resistor under test and the loop current flowing through the resistor under test using the four-wire measurement circuit. The voltage of the resistor under test is measured by a voltmeter connected to the leads across the resistor under test, and the ratio of the measured voltage to the measured current is used by a processor as the loop resistance of the security mechanism or the loop resistance of the pyrotechnic device.

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