Shunt-based bidirectional current sampling circuit and detection method for aircraft power distribution line

Abstract

This invention relates to a bidirectional current sampling circuit and detection method for aviation power distribution lines based on a shunt, comprising a current detection circuit based on a shunt and a floating ground reference circuit with an external reference voltage. The 2.5V output terminal, Floal_Ref signal output terminal, and U_shunt+ output terminal of the floating ground reference circuit are connected to the corresponding input ports of the current detection circuit. This invention addresses aviation 270V high-voltage DC lines by proposing a shunt-based floating ground reference method for sampling feeder DC current, which significantly reduces the limitations imposed by the conditioning circuit on the common-mode input voltage. It can detect bidirectional current on the feeder and can be applied to small-signal, high common-mode voltage conditioning applications. It features simple structure, high sampling accuracy, high reliability, and strong anti-interference capability, facilitating integration with product structures and enabling modularization and miniaturization of the product.

Description

Technical Field

[0001] This invention belongs to the field of aviation electrical control and testing, and relates to a bidirectional current sampling circuit and testing method for aviation power distribution lines based on a shunt. Background Technology

[0002] With the development of aircraft power supply technology, high-precision, reliable, and safe signal detection plays an increasingly important role in system control and protection. In 270V high-voltage DC power supply systems, the traditional method for detecting feeder current is the current sampling method based on Hall effect sensors. Hall effect sensors have advantages such as high measurement accuracy, good linearity, and high reliability. They can achieve isolated current measurement, preventing the influence of high voltage on downstream circuits and ensuring safe current detection. However, Hall effect sensors are active devices and cannot work independently, and they are relatively expensive. The current sampling method based on shunts has the advantages of low cost, simple structure, stable and reliable operation, immunity to external electromagnetic interference, no need for an external power supply, and ease of use. However, in the field of aviation 270V high-voltage DC power supply, shunts are rarely used. How to extract a weak voltage signal of tens of millivolts from the 270V high voltage to achieve high-precision current detection has become a technical challenge. Summary of the Invention

[0003] Technical problems to be solved

[0004] To overcome the shortcomings of existing technologies, this invention proposes a bidirectional current sampling circuit and detection method for aviation power distribution lines based on a shunt, which facilitates current detection and improves current sampling accuracy, reliability, and anti-interference capability, enabling modularization, integration, and miniaturization of power distribution products. This invention can withstand surge overvoltages in the power supply system, has high current sampling accuracy, and facilitates overcurrent and short-circuit protection for power distribution products, ensuring their safe operation.

[0005] Technical solution

[0006] A bidirectional current sampling circuit for aviation power distribution lines based on a shunt, characterized by comprising a current detection circuit based on a shunt and a floating ground reference circuit with an external reference voltage, wherein the 2.5V output terminal, Floal_Ref signal output terminal, and U_shunt+ output terminal of the floating ground reference circuit are connected to the corresponding input ports of the current detection circuit; the current detection circuit based on the shunt includes a shunt resistor R1, differential low-pass filter circuits R3, R4, and C6, a current monitoring chip U1, a P-MOS transistor Q1, resistors R7, R6, R8, and R9, an operational amplifier U3A, and low-pass filter circuits R10 and C10; the shunt resistor R1 is connected in series between the U_shunt+ and U_shunt- terminals, and the U_shunt- terminal is connected to the VIN- port of the current monitoring chip U1 through resistor R3; U_shunt+... The nt+ terminal is connected to the VIN+ port of chip U1 via resistor R4, and to the V+ port of chip U1 via resistor R2. The VREF port of chip U1 is connected to the 2.5V output of the floating ground reference circuit. The OUT port is connected to the source of P-MOS transistor Q1 via resistor R6. The drain of Q1 is grounded via resistor R7 and connected to the positive input terminal of operational amplifier U3A via resistor R8. The negative input terminal of U3A is connected to the output terminal of U3A via parallel resistor R9 and capacitor C12. The output terminal of U3A is output to the AD sampling signal of the DSP via low-pass filter circuit R10 and C10. The Floal_Ref signal input terminal is connected to the GND port of chip U1, and to the ROS port and the gate of P-MOS transistor Q1 via resistor R5. A filter capacitor C6 is provided between the VIN+ and VIN- ports of chip U1.

[0007] The floating ground reference circuit includes a buck converter chip U4, feedback regulation circuits R14, R11 and Q2, voltage divider resistors R12 and R15, and a Zener diode U2. The VDD port of the converter chip U4 is connected to +5V, the HVIN port outputs the U_shunt+ signal through resistor R12, and the DRAIN port is connected to the Floal_Ref signal output through inductor L1. Resistor R15 is connected in series with the negative terminal of Zener diode U2 and then in parallel to the U_shunt+ and Floal_Ref signal terminals. The negative terminal of Zener diode U2 is the 2.5V terminal of the floating ground reference circuit. Resistor R14 is connected in parallel with the collector and base of Q2 to the U_shunt+ and Floal_Ref signal terminals. The emitter of Q2 is connected to the FB port of the converter chip U4 and grounded through resistor R11, forming the feedback regulation circuit of the converter chip U4.

[0008] The VREF port of the chip U1 is connected to the Floal_Ref signal input terminal through two parallel capacitors C7 and C8.

[0009] Two sets of parallel filter capacitors are provided on both ends of the resistor R2. Among them, capacitors C2 and C3 are connected in parallel between the U_shunt+ terminal and the Floal_Ref signal, and capacitors C4 and C5 are connected in parallel between the V+ port of chip U1 and the Floal_Ref signal terminal.

[0010] A filter capacitor C1 is provided between the U_shunt+ terminal and the R1 resistor and ground.

[0011] The operational amplifier U3A has a C9 filter capacitor connected to ground at its positive input terminal and a C11 filter capacitor connected to ground at its power supply terminal.

[0012] The converter chip U4 has a D1 diode at its DRAIN port and U_shunt+ port.

[0013] A resistor R13 is provided between the U_shunt+ terminal and the Floal_Ref signal.

[0014] The VDD port of the converter chip U4 is equipped with a C13 filter capacitor to ground.

[0015] A method for detecting bidirectional current in a 270V high-voltage feeder using the aforementioned shunt-based bidirectional current sampling circuit for aviation power distribution lines, characterized in that: The feeder current is: ,in, The voltage across shunt R1 is given, and the feed current is: .

[0016] Beneficial effects

[0017] This invention proposes a bidirectional current sampling circuit and detection method for aviation power distribution lines based on a shunt, including a current detection circuit based on a shunt and a floating ground reference circuit with an external reference voltage. The 2.5V output terminal, Floal_Ref signal output terminal, and U_shunt+ output terminal of the floating ground reference circuit are connected to the corresponding input ports of the current detection circuit. This invention targets aviation 270V high-voltage DC lines, proposing a method for sampling feeder DC current using a floating ground reference based on a shunt, which can significantly reduce the limitation of the conditioning circuit on the common-mode input voltage. It can also detect bidirectional current on the feeder and can be applied to small-signal, high common-mode voltage conditioning applications. It has advantages such as simple structure, high sampling accuracy, high reliability, and strong anti-interference capability, facilitating integration with product structures and enabling modularization and miniaturization of the product. Attached Figure Description

[0018] Figure 1 This is a current detection circuit based on a shunt.

[0019] Figure 2To generate a floating ground reference 30V lower than the 270V feed line voltage using the U4 (UCC28880DR) step-down BUK converter chip. Detailed Implementation

[0020] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0021] The principle of the proposed bidirectional DC current detection scheme for 270V high-voltage feeders based on shunts is as follows: Figure 1 , Figure 2 .

[0022] Figure 1 This is a current sensing circuit based on a shunt. Figure 2 A floating ground reference 30V lower than the 270V feed line voltage is generated by a U4 (UCC28880DR) step-down BUK converter chip; the 2.5V output terminal, Floal_Ref signal output terminal, and U_shunt+ output terminal of the floating ground reference circuit are connected to the corresponding input ports of the current detection circuit.

[0023] The shunt-based current detection circuit includes a shunt resistor R1 (0.25). ), differential low-pass filter circuit R3 (22 ), R4 (22) C6 (0.01) and C6 (0.01) ), current monitoring chip U1, P-MOS transistor Q1, resistor R7 (16 R6 (4.99) ), R8 (0 ) and R9 (16 ), operational amplifier U3A, low-pass filter circuit R10 (38.3) ) and C10 (0.1 The shunt resistor R1 is connected in series between the U_shunt+ and U_shunt- terminals. The U_shunt- terminal is connected to the VIN- port of the current monitoring chip U1 through resistor R3; the U_shunt+ terminal is connected to the VIN+ port of the chip U1 through resistor R4, and through R2 (10 The resistor connects to the V+ port of chip U1; the VREF port of chip U1 is connected to the 2.5V output of the floating ground reference circuit; the OUT port is connected to the source of P-MOS transistor Q1 through resistor R6; the drain of Q1 is grounded through resistor R7 and connected to the positive input terminal of operational amplifier U3A through resistor R8; the negative input terminal of U3A is connected through parallel resistor R9 and capacitor C12 (100... The output of U3A is connected to the low-pass filter circuit R10 and C10, and the output of U3A is output to the AD sampling signal of the DSP. The Floal_Ref signal input is connected to the GND port of chip U1 and connected to R5 (24.3) through the low-pass filter circuit R10 and C10. The ROS port is connected to the gate of the P-MOS transistor Q1; a C6 (0.01) is provided between the VIN+ and VIN- ports of the chip U1. ) Filter capacitor;

[0024] The VREF port of the chip U1 is connected via two parallel capacitors C7 (0.1). ) and C8 (1 Connect it to the Floal_Ref signal input terminal.

[0025] Two sets of parallel filter capacitors are respectively provided on both ends of the resistor R2, wherein capacitor C2 (10) is connected in parallel between the U_shunt+ terminal and the Floal_Ref signal. ) and C3 (10 ), A capacitor C4 (1) is connected in parallel between the V+ port and the Floal_Ref signal terminal of chip U1. C5 (0.1) and C5 (0.1) ).

[0026] A capacitor C1 (0.033) is connected to ground between the U_shunt+ terminal and resistor R1. ) Filter capacitor.

[0027] The positive input terminal of the operational amplifier U3A is connected to ground via C9 (100). ) Filter capacitor, power supply has C11 (0.1) to ground. ) Filter capacitor.

[0028] The floating ground reference circuit includes a buck converter chip U4 and a feedback regulation circuit R14 (1.47). ), R11 (51) ) and Q2, voltage divider resistor R12 (0 ) and R15 (200 And Zener diode U2; the VDD port of converter chip U4 is connected to +5V, the HVIN port outputs the U_shunt+ signal through resistor R12, and the DRAIN port is connected to the Floal_Ref signal output through inductor L1; resistor R15 is connected in series with the negative terminal of Zener diode U2 and then in parallel to the U_shunt+ and Floal_Ref signal terminals. The negative terminal of Zener diode U2 is the 2.5V terminal of the floating ground reference circuit; R14 (1.47 The resistor is connected in parallel to the U_shunt+ signal terminal and the Floal_Ref signal terminal through the collector and base of Q2. The emitter of Q2 is connected to the FB port of the converter chip U4 and grounded through the resistor R11 to form the feedback regulation circuit of the converter chip U4.

[0029] The converter chip U4 has a D1 diode at its DRAIN port and U_shunt+ port.

[0030] R13 (402) is provided between the U_shunt+ terminal and the Floal_Ref signal. )resistance.

[0031] The VDD port of the converter chip U4 is connected to ground via C13 (0.1). ) Filter capacitor.

[0032] Working principle: Figure 1 The shunt-based current detection circuit generates a weak voltage of tens of millivolts after the 270V feeder current passes through shunt R1. This voltage is then filtered by a differential low-pass filter circuit composed of R1, R4, and C6 to remove noise from the differential input voltage before entering a sampling circuit composed of a U1 (INA170) current monitoring chip. This chip is a single-supply chip that converts differential input voltage into current output and can detect the bidirectional current of the feeder through a reference voltage input pin. The output current of the U1 chip flows through a Q1 P-MOS transistor to resistor R7, converting it into a voltage signal. The drain and source of the Q1 P-MOS transistor can withstand a negative voltage of 450V and prevents high voltages from passing through subsequent circuits. The voltage signal across resistor R7 is then filtered by a non-inverting follower buffer circuit composed of a U3A operational amplifier to improve the signal's driving capability. After being filtered by a low-pass filter circuit composed of R10 and C10, it can be directly sent to the DSP's AD sampling port for easy current monitoring by the microprocessor.

[0033] Since the line voltage is 270V, while the INA170 common-mode input voltage range is (2.7~60)V, direct use will damage the chip. To improve the common-mode input voltage range and facilitate the detection of the 270V feeder current, this invention designs a floating ground reference circuit, such as... Figure 2 As shown. The GND reference pin can be floated to a high potential as a floating ground reference for the sampling circuit, ensuring that the common-mode input voltage range of the chip is (2.7~60)V.

[0034] Figure 2A U4 (UCC28880DR) buck converter chip generates a floating ground reference 30V lower than the 270V feed line voltage. When the feed line voltage changes, the U4 chip, through a feedback regulation circuit composed of R14, R11, and Q2, consistently outputs a floating ground reference approximately 30V lower than the 270V feed line voltage. Simultaneously, a U2 high-precision voltage reference chip generates a reference voltage 2.5V higher than the floating ground reference, which serves as the external reference voltage input for the U1 current monitoring chip.

[0035] Combination Figure 1 The calculation principle for detecting bidirectional current in a 270V high-voltage feeder is as follows:

[0036] Output voltage for:

[0037] in, The voltage across the shunt is the output voltage. This is the voltage across capacitor C10;

[0038] The feed current is:

[0039] according to Figure 1 and Figure 2 The formula for calculating the feeder current is:

[0040]

[0041] in, This is the resistance value of the shunt.

Claims

1. A bidirectional current sampling circuit for aviation power distribution lines based on a shunt, characterized in that... The floating ground reference circuit includes a shunt-based current detection circuit and an external reference voltage, wherein a 2.5V terminal of the floating ground reference circuit, a Float_Ref signal terminal and a U_shunt+ terminal are connected with corresponding input terminals of the current detection circuit; the shunt-based current detection circuit includes a shunt resistor R1, a differential low-pass filter circuit, a current monitoring chip U1, a P-MOS transistor Q1, resistors R7, R6, R8 and R9, an operational amplifier U3A and a low-pass filter circuit; the low-pass filter circuit includes a resistor R10 and a capacitor C10; the differential low-pass filter circuit includes resistors R3, R4 and a filter capacitor C6; the shunt resistor R1 is connected in series between the U_shunt+ terminal and a U_shunt- terminal, the U_shunt- terminal is connected with a VIN- terminal of the current monitoring chip U1 through a resistor R3; the U_shunt+ terminal is connected with a VIN+ terminal of the chip U1 through a resistor R4 and connected with a V+ terminal of the chip U1 through a resistor R2; a VREF terminal of the chip U1 is connected with the 2.5V terminal of the floating ground reference circuit, an OUT terminal of the chip U1 is connected with a source electrode of the P-MOS transistor Q1 through a resistor R6, a drain electrode of the Q1 is connected with the ground through a resistor R7 and connected with an input positive terminal of the operational amplifier U3A through a resistor R8; an input negative terminal of the U3A is connected with an output terminal of the U3A through a parallel resistor R9 and a capacitor C12, the output terminal of the U3A is output to an AD sampling signal of a DSP through the low-pass filter circuit; the Float_Ref signal terminal is connected with a GND terminal of the chip U1, the Float_Ref signal terminal is connected with a ROS terminal through a resistor R5, and the Float_Ref signal terminal is also connected with a gate electrode of the P-MOS transistor Q1; a filter capacitor C6 is arranged between the VIN+ terminal and the VIN- terminal of the chip U1; The floating ground reference circuit includes a step-down BUK conversion chip U4, a feedback adjustment circuit, a voltage divider resistor R12 and a voltage divider resistor R15 and a stabilizing tube U2; the feedback adjustment circuit includes a resistor R14, a resistor R11 and a transistor Q2; a VDD terminal of the conversion chip U4 is connected with +5V, an HVIN terminal is connected with the U_shunt+ signal terminal through the voltage divider resistor R12, a DRAIN terminal is connected with the Float_Ref signal terminal through an inductor L1; the voltage divider resistor R15 is connected with a negative terminal of the stabilizing tube U2, a positive terminal of the stabilizing tube U2 is connected with the Float_Ref signal terminal, the voltage divider resistor R15 is connected with the U_shunt+ signal terminal at the other end, and the negative terminal of the stabilizing tube U2 is the 2.5V terminal of the floating ground reference circuit; one end of the resistor R14 is connected with the U_shunt+ signal terminal, the other end is connected with the Float_Ref signal terminal through a collector electrode and a base electrode of the Q2, and the emitter electrode of the Q2 is connected with an FB terminal of the conversion chip U4 and grounded through the resistor R11 to form the feedback adjustment circuit of the conversion chip U4.

2. The shunt-based bi-directional current sampling circuit for an aircraft power distribution line of claim 1, wherein: The VREF terminal of the chip U1 is connected with the Float_Ref signal terminal through two parallel capacitors C7 and C8.

3. The shunt-based bi-directional current sampling circuit for an aircraft power distribution line of claim 1, wherein: Two groups of parallel filter capacitors are respectively arranged at two ends of the resistor R2, wherein the capacitor C2 and the capacitor C3 are connected in parallel between the U_shunt+ end and the Float_Ref signal end, and the V+ port of the chip U1 is connected in parallel with the capacitor C4 and the capacitor C5.

4. The shunt-based bi-directional current sampling circuit for an aircraft power distribution line of claim 1, wherein: The filter capacitor C1 is arranged between the U_shunt+ end and the shunt resistor R1 and the ground.

5. The shunt-based bi-directional current sampling circuit for an aircraft power distribution line of claim 1, wherein: The filter capacitor C9 is arranged between the input positive end of the operational amplifier U3A and the ground, and the filter capacitor C11 is arranged between the power supply and the ground.

6. The shunt-based bi-directional current sampling circuit for an aircraft power distribution line of claim 1, wherein: The diode D1 is arranged between the DRAIN port of the conversion chip U4 and the U_shunt+ end.

7. The shunt-based bi-directional current sampling circuit for an aircraft power distribution line of claim 1, wherein: The resistor R13 is arranged between the U_shunt+ end and the Float_Ref signal end.

8. The shunt-based bi-directional current sampling circuit for an aircraft power distribution line of claim 1, wherein: The filter capacitor C13 is arranged between the VDD port of the conversion chip U4 and the ground.

9. A method for detecting the bidirectional current of 270V high-voltage feeder lines by using the bidirectional current sampling circuit of the shunt-based aviation power distribution line according to any one of claims 1-8, characterized in that: Output voltage , the feeder current is: wherein, is the voltage across the shunt resistor R1, the feeder current is: .

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