DC current sensor circuit with arbitrary bias current output

Abstract

The present invention discloses a DC current sensor circuit with arbitrary bias current output, including a precision voltage stabilizing circuit, a magnetic sensitivity detection circuit, a voltage comparison and push-pull output circuit and a bias circuit connected in sequence, wherein: the precision voltage stabilizing circuit is used to convert the input voltage into the working voltage of the magnetic sensitivity detection circuit; the magnetic sensitivity detection circuit is used to detect the magnetic field strength in the open coil and generate a signal output to the voltage comparison and push-pull output circuit; the voltage comparison and push-pull output circuit is used to generate a zero-point bias current; the bias circuit is used to generate a bias current, and the bias current is superimposed with the zero-point bias current as the output of the DC current sensor. The present invention can detect DC current signals up to hundreds of amperes, solves the power consumption problem generated by the input current signal of hundreds of amperes, and isolates and outputs a current signal with a DC bias current that can be arbitrarily set and is linearly related to the detection current.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, and in particular to a direct current sensor circuit with arbitrary bias current output. Background Art

[0002] In recent years, Hall current sensor products have been widely used in military and civilian fields such as aviation, aerospace, communications, instrumentation, metallurgy and railways due to their good accuracy and linearity, high isolation between detection signals and output signals, high reliability, low power consumption, and easy maintenance and replacement. In many applications, the zero-point output of the Hall current sensor is required to be the reference 0mA or 4mA, that is, when the detection current is zero, the sensor output current is 0mA or 4mA; when the detection current is in the negative direction, the sensor output current is a current value less than the reference value (0mA or 4mA); when the detection current is in the positive direction, the sensor output current is a current value greater than the reference value (0mA or 4mA), and the detection current and output current change in a linear relationship. At present, the zero-point output current of conventional Hall current sensors on the market is mostly 0mA or 4mA, and there are no products with other reference value outputs. However, in applications, there is a real need for products with other reference current outputs, such as a 30mA reference, that is, when the detection current is zero, the sensor output current is 30mA; when the detection current is in the negative direction, the sensor output current is a current value less than 30mA; when the detection current is in the positive direction, the sensor output current is a current value greater than 30mA, and the detection current and output current change in a linear relationship. There is no sensor in the prior art that can output any bias current. Summary of the invention

[0003] The object of the present invention is to provide a DC current sensor circuit with arbitrary bias current output, which is used to solve the problem that the zero point output reference of the Hall current sensor in the prior art is 0mA or 4mA and cannot arbitrarily output bias current of other values.

[0004] The present invention solves the above problems through the following technical solutions:

[0005] A DC current sensor circuit with arbitrary bias current output includes a precision voltage stabilization circuit, a magnetic sensitivity detection circuit, a voltage comparison and push-pull output circuit and a bias circuit connected in sequence, wherein:

[0006] A precision voltage stabilizing circuit, used to convert the input voltage into the working voltage of the magnetic sensitive detection circuit;

[0007] The power supply of general sensors is not a precise voltage value (such as ±15V), but a voltage range (such as ±12V~±15V). The output voltage at zero magnetic flux in the magnetic detection circuit is the positive supply voltage and is half of the supply voltage. In order to ensure that the zero-point output of the magnetic detection circuit is stable when the supply voltage changes within the allowable range, it is necessary to provide the magnetic detection circuit with a precise supply voltage (such as +5V). Therefore, power supply stabilization is required.

[0008] A magnetic sensitive detection circuit is used to detect the magnetic field strength in the open coil and generate a signal to output to the voltage comparison and push-pull output circuit;

[0009] The magnetic detection circuit mainly includes a Hall chip. When the detected current is zero, there is zero magnetic flux in the open coil, and the zero-point output voltage of the Hall chip is the reference voltage. When the detected current passes through the open coil, the Hall chip in the open coil detects the change in magnetic flux of the magnetic ring, and outputs a voltage value proportional to the change in magnetic flux based on the zero-point output voltage, that is:

[0010] Vout1 = reference voltage + K*ΔV

[0011] Among them, Vout1 is the output voltage of the Hall chip, ΔV is the sensitivity of the Hall chip, that is, the voltage change caused by a unit magnetic flux change, and K is the amplification factor adjusted by the peripheral resistor.

[0012] The signal generated by the magnetic sensitive detection circuit is amplified in the voltage comparison and push-pull output circuit, and then drives the power tube in the push-pull circuit of the voltage comparison and push-pull output circuit to turn on, generating a compensation current. The compensation current generates magnetic induction intensity in the magnetic field. When the compensation current increases to a certain level, the compensation reaches a balance, that is, a zero-point bias current is generated.

[0013] The bias circuit is used to generate a bias current, and the bias current is superimposed with the zero-point bias current to serve as the output of the DC current sensor. By changing the bias current of the bias circuit, the output current of the DC current sensor can be changed to achieve any bias current output.

[0014] The bias circuit includes a primary bias current regulating resistor connected to the input voltage, the primary bias current regulating resistor is connected in series with an anti-reverse diode D2 and then connected to the first end of the primary winding of the transformer T1, and the second end of the primary winding of the transformer T1 is grounded; the first end of the secondary winding of the transformer T1 is connected to the output end of the voltage comparison and push-pull output circuit, and the second end of the secondary winding of the transformer T1 serves as the output end of the DC current sensor.

[0015] The voltage comparison and push-pull output circuit includes an operational amplifier, a power tube Q1 and a power tube Q2. The positive input terminal and the negative input terminal of the operational amplifier are respectively connected to the two output terminals of the magnetic sensitive detection circuit. The voltage input positive terminal of the operational amplifier is connected to the voltage VCC through an anti-reverse diode D1. The output terminal of the operational amplifier is connected to one end of the secondary winding of the transformer T1 through a resistor R11. The voltage input negative terminal of the operational amplifier is connected to the output terminal of the DC current sensor through an anti-reverse diode D3. The power tube Q1 and the power tube Q2 are push-pull connected. A resistor R12 is connected in series between the emitter of the power tube Q1 and the emitter of the power tube Q2. The collector of the power tube Q1 is connected to the voltage input positive terminal of the operational amplifier. The collector of the power tube Q2 is connected to the voltage input negative terminal of the operational amplifier after being connected in series with a resistor R13. The base of the power tube Q1 and the base of the power tube Q2 are connected to the node between the operational amplifier and the resistor R11. The operational amplifier adopts a dual-power supply rail-to-rail operational amplifier.

[0016] The power supply voltage of the operational amplifier is supplied after passing through the anti-reverse diode D1. The resistors R12 and R13 are push-pull output current regulating resistors, which ensure that the output currents of the power tubes Q1 and Q2 remain balanced and avoid damage to the power tubes due to excessive current.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0018] (1) The present invention can detect DC current signals up to hundreds of amperes, thereby solving the power consumption problem caused by input current signals of hundreds of amperes, and isolating and outputting a current signal with a DC bias current that can be arbitrarily set and is linearly related to the detection current.

[0019] (2) The circuit of the present invention is simple, low-cost and small in size. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a principle block diagram of the present invention;

[0021] Figure 2 It is the circuit principle diagram of the present invention;

[0022] Figure 3 This is a schematic diagram of the power dissipation of the SOT89 power tube;

[0023] Among them, 1-precision voltage stabilization circuit; 2-magnetic sensitive detection circuit; 3-voltage comparison and push-pull output circuit; 4-bias circuit; U1B-Hall chip; U3-precision voltage stabilization power supply chip; U2A-operational amplifier. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0025] Example:

[0026] Combined with Figure 1 As shown, a DC current sensor circuit with arbitrary bias current output includes a precision voltage stabilization circuit 1, a magnetic sensitivity detection circuit 2, a voltage comparison and push-pull output circuit 3 and a bias circuit 4 connected in sequence, wherein:

[0027] The precision voltage stabilization circuit 1 is used to convert the input voltage into the working voltage of the magnetic sensitive detection circuit 2; the power supply of the general sensor is not a precise voltage value (such as ±15V), but a voltage range (such as ±12V~±15V), and the output voltage of the magnetic sensitive detection circuit 2 at zero magnetic flux is the positive power supply voltage and is half of the power supply voltage. In order to ensure that the zero-point output of the magnetic sensitive detection circuit 2 is stable when the power supply voltage changes within the allowable range, it is necessary to provide the magnetic sensitive detection circuit 2 with a precise power supply voltage (such as +5V), therefore, power supply stabilization is required.

[0028] The magnetic sensitive detection circuit 2 is used to detect the magnetic field strength in the open coil and generate a signal output to the voltage comparison and push-pull output circuit 3; the magnetic sensitive detection circuit 2 mainly includes a Hall chip (HALL) U1B, the reference voltage of the Hall chip U1B is 2.5V, when the detected current is zero, there is zero magnetic flux in the open coil, the zero-point output power supply of the Hall chip U1B is 2.5V, when the detected current passes through the open coil, the Hall chip U1B in the open coil detects the change in magnetic flux of the magnetic ring, and will output a voltage value proportional to the change in magnetic flux on the basis of the zero-point output voltage, that is:

[0029] Vout1=2.5V+K*ΔV

[0030] Among them, Vout1 is the output voltage of the Hall chip U1B, ΔV is the sensitivity of the Hall chip, that is, the voltage change caused by a unit magnetic flux change, and K is the amplification factor adjusted by the peripheral resistor.

[0031] The signal generated by the magnetic sensitive detection circuit 2 is amplified in the voltage comparison and push-pull output circuit 3, and drives the power tube in the push-pull circuit of the voltage comparison and push-pull output circuit 3 to turn on, generating a compensation current. The compensation current generates a magnetic induction intensity in the magnetic field. When the compensation current increases to a certain level, the compensation reaches a balance, that is, a zero-point bias current is generated.

[0032] The bias circuit 4 is used to generate a bias current, which is superimposed with the zero-point bias current as the output of the DC current sensor. By changing the bias current of the bias circuit 4, the output current of the DC current sensor can be changed to achieve any bias current output.

[0033] Embodiment 2:

[0034] Based on Example 1, Figure 2 As shown, the input voltage VCC is converted into +5V voltage after being stabilized by the anti-reverse diode D1 and the precision voltage stabilizing circuit 1 to power the magnetic sensitive detection circuit 2. The precision voltage stabilizing circuit 1 is composed of the precision voltage stabilizing power supply chip U3 and the bypass capacitor C1 and the bypass capacitor C2, which are used to stabilize the input and output voltages of the chip. The magnetic sensitive detection circuit 2 includes the Hall chip U1B and the peripheral resistor. When the detected current passes through the open coil, the Hall chip U1B in the air gap of the open coil detects the change of the magnetic flux of the magnetic ring, and superimposes a voltage value proportional to the change of the magnetic flux on the basis of the zero-point output voltage. When the magnetic lines of force pass vertically through the front of the Hall chip U1B, the Hall chip U1B will output a positive change voltage, that is, ΔV>0; otherwise, it will output a negative voltage change, that is, ΔV<0. The Hall chip is a linear output magnetic sensitive chip with an adjustable temperature compensation function inside. The maximum output voltage is clamped at 93% of the supply voltage, and the minimum output voltage is 5% of the supply voltage. The function of the peripheral resistors (resistor R3, resistor R4, resistor R5, resistor R*1, resistor R*2 and resistor R*3) is to adjust the amplification factor.

[0035] The voltage comparison and push-pull output circuit 3 includes an operational amplifier U2A, a power tube Q1 and a power tube Q2. The positive input terminal and the negative input terminal of the operational amplifier U2A are respectively connected to the two output terminals of the magnetic sensitive detection circuit 2. The voltage input positive terminal of the operational amplifier U2A is connected to the input voltage VCC through an anti-reverse diode D1. The output terminal of the operational amplifier U2A is connected to one end of the secondary winding of the transformer T1 through a resistor R11. The voltage input negative terminal of the operational amplifier U2A is connected to the output terminal of the DC current sensor through an anti-reverse diode D3. The power tube Q1 and the power tube Q2 are push-pull connected. A resistor R12 is connected in series between the emitter of the power tube Q1 and the emitter of the power tube Q2. The collector of the power tube Q1 is connected to the voltage input positive terminal of the operational amplifier. The collector of the power tube Q2 is connected to the voltage input negative terminal of the operational amplifier after being connected in series with a resistor R13. The base of the power tube Q1 and the base of the power tube Q2 are connected to the node between the operational amplifier and the resistor R11. The operational amplifier U2A adopts a dual-power supply rail-to-rail operational amplifier. Resistors R12 and R13 are push-pull output current regulating resistors, which ensure that the output currents of power tubes Q1 and Q2 remain balanced and avoid damage to the power tubes due to excessive currents.

[0036] When the detected current I1 changes within the range of 0A to 200A, the open magnetic ring generates a magnetic induction intensity B1, and the Hall chip U1B outputs different voltages, causing the operational amplifier U2A to output a voltage close to the positive power supply or the negative power supply, and then turning on the power tube Q1 or the power tube Q2 in the subsequent push-pull output circuit, causing the secondary coil to generate a compensation current I2 and generate a compensation magnetic induction intensity B2 on the magnetic ring. When the compensation current increases to a certain level, the compensation reaches a balance, and I2 no longer increases. According to the total current law N1I1=N2I2, I2 is proportional to I1.

[0037] The following are examples of actual measurements:

[0038] Since the maximum operating temperature is 95°C, the power tube in the present invention uses a SOT89 transistor, and its dissipated power is as follows: Figure 3 When the ambient temperature is 95°C, the power dissipation is slightly greater than 0.2W. According to the circuit parameters, the power dissipation formula of the push-pull circuit can be listed as:

[0039] P=I OUT ×(14-I OUT ×R)

[0040] =-67I OUT 2 +14I OUT

[0041] Where 67 is the measured sensor output current I OUT The total resistance passed through, 14 is the measured voltage after the input voltage passes through the anti-reverse diode, all of which are estimates. The calculation can be obtained when I OUT When the current reaches 104mA, the power consumption is the largest, which is 0.73W, leaving ample room for improvement.

[0042] The bias circuit includes a primary bias current regulating resistor connected to the input voltage, the primary bias current regulating resistor is connected in series with an anti-reverse diode D2 and then connected to the first end of the primary winding of the transformer T1, and the second end of the primary winding of the transformer T1 is grounded; the first end of the secondary winding of the transformer T1 is connected to the output end of the voltage comparison and push-pull output circuit, and the second end of the secondary winding of the transformer T1 serves as the output end of the DC current sensor.

[0043] During normal operation, the DC supply voltage VCC in the range of ±12V to ±15V is converted into accurate +5V by the precision voltage regulator circuit 1 to power the magnetic detection circuit 2. The magnetic detection circuit 2 detects the magnetic field strength in the open coil, and generates a reference 0mA zero-point bias current Io1 after voltage comparison and amplification by the power tube of the push-pull output circuit 3. The +5V voltage simultaneously drives the power tube Q1 or the power tube Q2 to turn on, and then generates a bias current Io2 through the bias circuit 4. After the zero-point bias current Io1 and the bias current Io2 are superimposed, the output Iout of the DC linear Hall current sensor with arbitrary bias current output is finally realized.

[0044] Connect the bias circuit to the +5V power supply terminal and connect a diode D2 in series to prevent the current from flowing back into the voltage regulator chip and causing damage to the product when the primary current is reversed. Resistors R14, R15, and R16 are used to adjust the primary bias current. Assuming that the output current of the primary winding is I1 and the output current of the secondary winding is I2, according to the law of conservation of ampere-turn ratio, we have:

[0045] N1I1+N3I3=N2I2

[0046] Among them, N1 is the number of turns of the measured current, usually 1; I1 is the primary current; N3 is the number of turns of the primary winding; I3 is the primary bias current; N2 is the number of turns of the secondary winding; I2 is the secondary output current, that is, the bias current Io2, which is superimposed with the zero-point bias current Io1 as the sensor output.

[0047] It can be seen that the bias circuit can change the primary-to-secondary turns ratio of the coil as needed to obtain any required bias current output.

[0048] The DC200A DC Hall current sensor designed by the present invention linearly outputs a DC current of 30mA to 80mA after detection. The test results are shown in Table 1:

[0049]

[0050] Table 1 Test results of DC200A DC Hall current sensor

[0051] It can be seen from the results that the zero point deviation of the Hall current sensor is 0.05mA, the maximum deviation within the rated current range is 0.05mA, and the nonlinear error is less than 0.18%.

[0052] After building the test circuit, the following table shows the test results of input DC ±50A and output 50mA bias current as shown in Table 2:

[0053]

[0054]

[0055] Table 2 50mA bias current output and input comparison table

[0056] In summary, the DC sensor circuit with arbitrary bias current output can be realized in both theoretical and practical tests.

[0057] Although the present invention is described herein with reference to the illustrative embodiments of the present invention, the above embodiments are only preferred embodiments of the present invention, and the embodiments of the present invention are not limited to the above embodiments. It should be understood that those skilled in the art can design many other modifications and embodiments, which will fall within the scope and spirit of the principles disclosed in this application.

Claims

1. A DC current sensor circuit with arbitrary bias current output, characterized in that: It includes a precision voltage stabilizing circuit, a magnetic sensitive detection circuit, a voltage comparison and push-pull output circuit and a bias circuit which are connected in sequence, wherein: A precision voltage stabilizing circuit, used to convert the input voltage into the working voltage of the magnetic sensitive detection circuit; A magnetic sensitive detection circuit is used to detect the magnetic field strength in the open coil and generate a signal to output to the voltage comparison and push-pull output circuit; Voltage comparison and push-pull output circuit for generating zero-point bias current; A bias circuit, used for generating a bias current, wherein the bias current is superimposed with the zero-point bias current to serve as an output of the DC current sensor; The bias circuit includes a primary bias current regulating resistor connected to the input voltage, the primary bias current regulating resistor is connected in series with an anti-reverse diode D2 and then connected to the first end of the primary winding of the transformer T1, and the second end of the primary winding of the transformer T1 is grounded; the first end of the secondary winding of the transformer T1 is connected to the output end of the voltage comparison and push-pull output circuit, and the second end of the secondary winding of the transformer T1 serves as the output end of the DC current sensor; The voltage comparison and push-pull output circuit includes an operational amplifier, a power tube Q1 and a power tube Q2. The positive input terminal and the negative input terminal of the operational amplifier are respectively connected to the two output terminals of the magnetic sensitive detection circuit. The voltage input positive terminal of the operational amplifier is connected to the voltage VCC through an anti-reverse diode D1. The output terminal of the operational amplifier is connected to one end of the secondary winding of the transformer T1 through a resistor R11, and the voltage input negative terminal of the operational amplifier is connected to the output terminal of the DC current sensor through an anti-reverse diode D3. The power tube Q1 and the power tube Q2 are push-pull connected. A resistor R12 is connected in series between the emitter of the power tube Q1 and the emitter of the power tube Q2. The collector of the power tube Q1 is connected to the voltage input positive terminal of the operational amplifier. The collector of the power tube Q2 is connected in series with a resistor R13 and then connected to the voltage input negative terminal of the operational amplifier. The base of the power tube Q1 and the base of the power tube Q2 are connected to the node between the operational amplifier and the resistor R11. The magnetic sensitive detection circuit includes a Hall chip U1B and a peripheral resistor. When the detected current passes through the open coil, the Hall chip U1B in the air gap of the open coil detects the change in magnetic flux of the magnetic ring, and superimposes a voltage value proportional to the change in magnetic flux on the basis of the zero-point output voltage. When the magnetic lines pass vertically through the front of the Hall chip U1B, the Hall chip U1B will output a positive change in voltage, that is, ΔV>0; otherwise, it will output a negative voltage change, that is, ΔV<0.

2. The DC current sensor circuit with arbitrary bias current output according to claim 1, characterized in that: The operational amplifier is a dual-power rail-to-rail operational amplifier.

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