Sine wave excitation circuit for magnetic flux type current sensor

Abstract

The utility model relates to a sine wave excitation circuit for a magnetic flux type current sensor. The device comprises a square wave generator used for generating a square wave signal; the resonant oscillator is connected with the square wave generator, at least generates sine wave signals of fundamental frequency based on the square wave signals generated by the square wave generator and loads the generated sine wave signals to the magnetic core, and the frequency of the fundamental frequency is consistent with the frequency of the square wave signals; the excitation signal sampling feedback circuit is connected with the square-wave generator and is adaptively connected with the magnetic core, so that a magnetic core excitation signal adaptively connected with the magnetic core is sampled and then transmitted to the square-wave generator, and the excitation signal sampling feedback circuit comprises a signal conditioning circuit and a peak detection circuit. According to the utility model, the magnetic core can be effectively modulated, and the noise is lower.

Description

Technical Field

[0001] This utility model relates to an excitation circuit, and more particularly to a sinusoidal excitation circuit for a flux current sensor. Background Technology

[0002] Flux-type current sensors offer high accuracy in current measurement. They are closed-loop feedback, zero-flux current sensors capable of measuring both DC and AC currents. Generally, flux-type current sensors can include magnetically modulated current sensors or fluxgate current sensors.

[0003] When a flux-type current sensor measures current, it primarily relies on the magnetic saturation of an internal magnetic core through alternating excitation. To achieve this alternating excitation saturation, a magnetic modulator is typically used to modulate the core. The magnetic modulator outputs an excitation waveform, which is often a square wave, trapezoidal wave, or triangular wave. While these waveforms are easy to generate, they all have abrupt changes in slope. When this excitation waveform is applied to the coil of the flux-type current sensor, it causes abrupt changes in the core state, leading to increased Barkhausen magnetic noise and increasing the noise of the magnetic modulator, making it difficult to meet the practical requirements for core modulation. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a sinusoidal excitation circuit for a flux current sensor, which can effectively modulate the magnetic core and has low noise.

[0005] According to the technical solution provided by this utility model, a sinusoidal excitation circuit for a flux current sensor is provided, the sinusoidal excitation circuit comprising:

[0006] A square wave generator is used to generate square wave signals.

[0007] A resonant oscillator is connected to a square wave generator and generates a sinusoidal signal with at least the fundamental frequency based on the square wave signal generated by the square wave generator. The generated sinusoidal signal is then loaded onto a magnetic core, wherein the frequency of the fundamental frequency is consistent with the frequency of the square wave signal.

[0008] An excitation signal sampling feedback circuit is connected to a square wave generator and a magnetic core adapter to sample the magnetic core excitation signal of the connected magnetic core and transmit it to the square wave generator. The excitation signal sampling feedback circuit includes a signal conditioning circuit and a peak detection circuit.

[0009] The resonant oscillator includes a resonant operational amplifier OA1, wherein...

[0010] The non-inverting input of the resonant oscillation operational amplifier OA1 is grounded, the inverting input of the resonant oscillation operational amplifier is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to one end of capacitor C2 and the output terminal of the square wave generator.

[0011] The other end of capacitor C2 is connected to the output of resonant oscillation operational amplifier OA1 and one end of capacitor C3. The other end of capacitor C3 forms the output of resonant oscillator, which is then connected to the first end of the magnetic core.

[0012] The second end of the magnetic core is grounded through the magnetic core current sensing resistor.

[0013] It also includes an amplitude control unit for regulating the amplitude state of a sinusoidal signal, wherein the output of the square wave generator is adapted to the resonant oscillator through the amplitude control unit.

[0014] The amplitude control unit includes a first voltage divider resistor and a second voltage divider resistor, wherein,

[0015] One end of the first voltage divider resistor is connected to the output terminal of the square wave generator, and the other end of the first voltage divider resistor is connected to one end of the second voltage divider resistor, capacitor C1, and capacitor C2.

[0016] Of the first voltage divider resistor and the second voltage divider resistor, at least the first voltage divider resistor shall be configured as an adjustable resistor.

[0017] It also includes a frequency control unit for regulating the frequency state of a sinusoidal signal, wherein the frequency control unit is adapted and connected to the resonant oscillation operational amplifier OA1.

[0018] The frequency control unit includes a frequency control resistor, wherein...

[0019] One end of the frequency control resistor is connected to the inverting input of the resonant oscillation operational amplifier OA1, and the other end of the frequency control resistor is connected to the output of the resonant oscillation operational amplifier OA1.

[0020] The frequency control resistor is an adjustable resistor.

[0021] The peak detection circuit is connected to the first end of the magnetic core, and the signal conditioning circuit is connected to the second end of the magnetic core.

[0022] The signal conditioning circuit and the peak detection circuit are connected to the square wave generator through the ADC circuit.

[0023] The signal conditioning circuit includes a signal conditioning operational amplifier OA2, wherein...

[0024] The non-inverting input of the signal conditioning operational amplifier OA2 is connected to a reference voltage unit, wherein the reference voltage unit includes resistors R7 and R8. One end of resistor R7 and one end of resistor R8 are both connected to the non-inverting input of the signal conditioning operational amplifier OA2, the other end of resistor R8 is grounded, and the other end of resistor R7 receives the reference voltage VREF.

[0025] The inverting input of the signal conditioning operational amplifier OA2 is connected to one end of resistor R5, one end of resistor R6, and one end of capacitor C4;

[0026] The other end of resistor R5 is connected to the second end of the magnetic core, and the other end of resistor R6 and the other end of capacitor C4 are both connected to the output of signal conditioning operational amplifier OA2.

[0027] The output of the signal conditioning operational amplifier OA2 is connected to a square wave generator via an ADC circuit.

[0028] The peak detection circuit includes a voltage follower, a detection current-limiting resistor, and a peak lock-in unit connected in sequence.

[0029] The voltage follower is connected to the first end of the magnetic core.

[0030] The peak lock unit is connected to the square wave generator via an ADC circuit.

[0031] The voltage follower includes a detector operational amplifier OA3, wherein...

[0032] The non-inverting input of the detector operational amplifier OA3 is connected to the first end of the magnetic core, the inverting input of the detector operational amplifier OA3 is connected to the output terminal of the detector operational amplifier OA3, and the output terminal of the detector operational amplifier OA3 is connected to the detector current limiting resistor.

[0033] The peak lock-in unit includes a peak lock-in diode and a peak lock-in capacitor. The anode of the peak lock-in diode is connected to the detector current-limiting resistor, and the cathode of the peak lock-in diode is connected to one end of the peak lock-in capacitor, forming the output terminal of the peak detection circuit.

[0034] The other end of the peak lock-in capacitor is grounded.

[0035] The advantages of this invention are: it uses a square wave generator to generate a square wave signal, and a resonant oscillator to convert the square wave signal into a sine wave signal, so that the generated sine wave signal can be used to excite the magnetic core. This improves the convenience of generating a sine wave signal to excite the magnetic core, and has lower noise, improving the performance of exciting the magnetic core, thereby improving the accuracy of current measurement by the flux current sensor.

[0036] The excitation state of the magnetic core by the sine wave signal can be determined by the excitation signal sampling feedback circuit. The amplitude and frequency of the sine wave signal can be adjusted by the amplitude control unit and the frequency control unit, thereby further improving the excitation state of the magnetic core by the sine wave signal, so that the magnetic core can be in a better working state. Attached Figure Description

[0037] Figure 1 This is a circuit diagram of one embodiment of the sinusoidal excitation circuit of this utility model.

[0038] Figure 2 This is a circuit schematic diagram of one embodiment of the signal conditioning circuit of this utility model.

[0039] Figure 3 This is a circuit diagram of one embodiment of the peak detection circuit of this utility model. Detailed Implementation

[0040] The present invention will be further described below with reference to the specific accompanying drawings and embodiments.

[0041] To effectively modulate the magnetic core and achieve low noise, this invention provides a sinusoidal excitation circuit for a flux-type current sensor. Specifically, the sinusoidal excitation circuit includes:

[0042] A square wave generator is used to generate square wave signals.

[0043] A resonant oscillator is connected to a square wave generator and generates a sinusoidal signal with at least the fundamental frequency based on the square wave signal generated by the square wave generator. The generated sinusoidal signal is then loaded onto a magnetic core, wherein the frequency of the fundamental frequency is consistent with the frequency of the square wave signal.

[0044] An excitation signal sampling feedback circuit is connected to a square wave generator and a magnetic core adapter to sample the magnetic core excitation signal of the connected magnetic core and transmit it to the square wave generator. The excitation signal sampling feedback circuit includes a signal conditioning circuit and a peak detection circuit.

[0045] It should be noted that the sine wave excitation circuit is used to generate the excitation flux current sensor's core. Since neither the sine wave nor its derivative has abrupt change points, the sine wave signal generated by the sine wave excitation circuit can achieve better excitation effect and lower magnetic noise.

[0046] To improve the ease of generating sine waves, in one embodiment of this invention, a square wave signal is first generated using a square wave generator. As described above, square wave signals are easy to generate; therefore, the square wave generator can employ commonly used methods, such as using a microprocessor, which allows the generation of square wave signals. The square wave signal generated by the square wave generator can then be used to generate a sine wave signal using a resonant oscillator. In other words, a sine wave signal can be generated by resonant oscillation of the square wave signal. Generally, the sine wave signal generated by the resonant oscillator is the fundamental frequency. When the sine wave signal is the fundamental frequency, the frequency of the sine wave is consistent with the frequency of the square wave signal.

[0047] Generally, a flux-type current sensor includes a sensing magnetic core and a compensation magnetic core. The compensation magnetic core is used to compensate for the flux of the sensing magnetic core. In order to improve the compensation effect, it is generally necessary to ensure that the performance of the compensation magnetic core is consistent with that of the sensing magnetic core. The method of compensation of the sensing magnetic core by the compensation magnetic core can be consistent with existing technology, and will not be elaborated here.

[0048] Understandably, due to the influence of the manufacturing process, it is difficult to guarantee the consistency between the compensation core and the induction core, which often diverges within a wide range. This requires the excitation circuit to be adapted according to the characteristics of the core, and to adjust the excitation frequency and excitation amplitude, so that the core can work in the best state.

[0049] In practice, after the sine wave signal is applied to the magnetic core, the excitation signal can be sampled by the excitation signal sampling feedback circuit and fed back to the square wave generator. If the square wave generator uses a microprocessor, the state of the sampled excitation signal can be compared and judged. For example, the excitation state of the current sine wave signal on the magnetic core can be judged, thereby determining whether the magnetic core is working in the optimal state. The method of judging whether the magnetic core is working in the optimal state can be consistent with the existing technology, and will not be elaborated here.

[0050] In one embodiment of this utility model, the resonant oscillator includes a resonant operational amplifier OA1, wherein...

[0051] The non-inverting input of the resonant oscillation operational amplifier OA1 is grounded, the inverting input of the resonant oscillation operational amplifier is connected to one end of capacitor C1, and the other end of capacitor C1 is connected to one end of capacitor C2 and the output terminal of the square wave generator.

[0052] The other end of capacitor C2 is connected to the output of resonant oscillation operational amplifier OA1 and one end of capacitor C3. The other end of capacitor C3 forms the output of resonant oscillator, which is then connected to the first end of the magnetic core.

[0053] The second end of the magnetic core is grounded through the magnetic core current sensing resistor.

[0054] Figure 1 An embodiment of a resonant oscillator is shown in the figure. Figure 1 In the diagram, T1 is the magnetic core, which is composed of... Figure 1 The illustrated embodiment controls the resonant oscillator to form a capacitive three-point oscillator. Of course, the resonant oscillator can also employ other circuit configurations, specifically designed to generate a sine wave signal from a square wave signal. Furthermore, the resonant oscillator generally includes other necessary components, which will be described below.

[0055] In one embodiment of the present invention, an amplitude control unit for controlling the amplitude state of a sine wave signal is further included, wherein the output terminal of the square wave generator is adapted to be connected to the resonant oscillator through the amplitude control unit.

[0056] Specifically, the amplitude adjustment unit can be used to adjust the amplitude of the sinusoidal signal generated by the resonant oscillator. After the amplitude of the sinusoidal signal is adjusted, a better excitation state can be achieved according to the characteristics of the magnetic core.

[0057] In one embodiment of this utility model, the amplitude control unit includes a first voltage divider resistor and a second voltage divider resistor, wherein...

[0058] One end of the first voltage divider resistor is connected to the output terminal of the square wave generator, and the other end of the first voltage divider resistor is connected to one end of the second voltage divider resistor, capacitor C1, and capacitor C2.

[0059] Of the first voltage divider resistor and the second voltage divider resistor, at least the first voltage divider resistor shall be configured as an adjustable resistor.

[0060] Figure 1 In the diagram, resistor R1 is the first voltage divider resistor, and resistor R2 is the second voltage divider resistor. The first voltage divider resistor is adjustable; adjusting its value adjusts the amplitude of the sine wave signal. The first voltage divider resistor can also be a fixed resistor, in which case the amplitude of the sine wave signal is not adjustable. When the first voltage divider resistor is adjustable, it can be adjusted manually or by a square wave generator. When adjusting the value of the first voltage divider resistor, the excitation state of the magnetic core T1 can be observed. When the excitation state is optimal, the resistance value of the first voltage divider resistor can be determined and maintained.

[0061] In one embodiment of the present invention, a frequency control unit for regulating the frequency state of a sine wave signal is further included, wherein the frequency control unit is adapted and connected to the resonant oscillation operational amplifier OA1.

[0062] As can be seen from the above description, the frequency of the sine wave signal can be adjusted by the frequency control unit, such as from the fundamental frequency to other frequency states, so as to meet the excitation requirements of the magnetic core T1.

[0063] In one embodiment of this utility model, the frequency control unit includes a frequency control resistor, wherein...

[0064] One end of the frequency control resistor is connected to the inverting input of the resonant oscillation operational amplifier OA1, and the other end of the frequency control resistor is connected to the output of the resonant oscillation operational amplifier OA1.

[0065] The frequency control resistor is an adjustable resistor.

[0066] Figure 1 In this diagram, resistor R3 is the frequency control resistor. It can be understood that different resistance values ​​of the frequency control resistor will produce sinusoidal signals of corresponding frequencies. Of course, the frequency control resistor can also be a resistor with a fixed resistance value; in this case, the frequency of the sinusoidal signal is fixed. It should be noted that the resistance value of the frequency control resistor can be adjusted manually or by a square wave generator using a microprocessor. During adjustment, the resistance value can be determined by observing the excitation state of the magnetic core T1.

[0067] In one embodiment of this invention, the peak detection circuit is connected to the first end of the magnetic core, and the signal conditioning circuit is connected to the second end of the magnetic core.

[0068] The signal conditioning circuit and the peak detection circuit are connected to the square wave generator through the ADC circuit.

[0069] Figure 1 In the diagram, magnetic core T1 is grounded through a core current sampling resistor, and resistor R4 is the core current sampling resistor. When the square wave generator uses a microprocessor, the signal conditioning circuit and peak detection circuit should be connected to the square wave generator through an ADC circuit. That is, after ADC (analog-to-digital conversion), the square wave generator using a microprocessor can process the excitation signal state of the sampling feedback, such as performing the comparison and judgment processing mentioned above. Of course, after the comparison and judgment processing, the corresponding resistance values ​​of the first voltage divider resistor and / or the frequency control resistor can be adjusted.

[0070] In one embodiment of this utility model, the signal conditioning circuit includes a signal conditioning operational amplifier OA2, wherein...

[0071] The non-inverting input of the signal conditioning operational amplifier OA2 is connected to a reference voltage unit, wherein the reference voltage unit includes resistors R7 and R8. One end of resistor R7 and one end of resistor R8 are both connected to the non-inverting input of the signal conditioning operational amplifier OA2, the other end of resistor R8 is grounded, and the other end of resistor R7 receives the reference voltage VREF.

[0072] The inverting input of the signal conditioning operational amplifier OA2 is connected to one end of resistor R5, one end of resistor R6, and one end of capacitor C4;

[0073] The other end of resistor R5 is connected to the second end of the magnetic core, and the other end of resistor R6 and the other end of capacitor C4 are both connected to the output of signal conditioning operational amplifier OA2.

[0074] The output of the signal conditioning operational amplifier OA2 is connected to a square wave generator via an ADC circuit.

[0075] Figure 2 An embodiment of a signal conditioning circuit is shown in the figure. Figure 2 In the illustrated embodiment, capacitor C4 serves as a low-pass filter and also acts as an anti-aliasing filter for the connected ADC circuit.

[0076] In practical implementation, when the square wave generator uses a microprocessor, the aforementioned ADC circuit can be formed by a built-in ADC module. Since the built-in ADC circuit can only receive positive voltages and cannot measure negative voltages, it is necessary to shift and scale the positive and negative current acquisition signals on the magnetic core current sampling resistor upwards to the positive voltage range allowed by the ADC circuit. In one embodiment of this invention, voltage shifting can be achieved through a reference voltage (VREF). The voltage shifting method can be... Figure 2 And the above explanation. Specifically, when R6 / R5 = R7 / R8, then:

[0077] In one embodiment of this utility model, the peak detection circuit includes a voltage follower, a detection current-limiting resistor, and a peak locking unit connected in sequence, wherein...

[0078] The voltage follower is connected to the first end of the magnetic core.

[0079] The peak lock unit is connected to the square wave generator via an ADC circuit.

[0080] Specifically, since the peak detection circuit is connected to the first end of the magnetic core T1, and the sine wave signal is also loaded onto the first end of the magnetic core T1, the peak detection circuit can detect the peak value of the sine wave signal as the excitation signal and transmit the detected peak value to the square wave generator.

[0081] In one embodiment of this invention, the voltage follower includes a detector operational amplifier OA3, wherein...

[0082] The non-inverting input of the detector operational amplifier OA3 is connected to the first end of the magnetic core, the inverting input of the detector operational amplifier OA3 is connected to the output terminal of the detector operational amplifier OA3, and the output terminal of the detector operational amplifier OA3 is connected to the detector current limiting resistor.

[0083] The peak lock-in unit includes a peak lock-in diode and a peak lock-in capacitor. The anode of the peak lock-in diode is connected to the detector current-limiting resistor, and the cathode of the peak lock-in diode is connected to one end of the peak lock-in capacitor, forming the output terminal of the peak detection circuit.

[0084] The other end of the peak lock-in capacitor is grounded.

[0085] Figure 3 The diagram illustrates a circuit schematic of one embodiment of the detection circuit. Resistor R9 is the detection current-limiting resistor, D1 is the peak-locked diode, and capacitor C5 is the peak-locked capacitor. The diagram also shows an embodiment where the peak-locked capacitor is connected in parallel with resistor R10. In this embodiment, the peak value is always locked in a positive state, ensuring that it can be transmitted via the ADC circuit to the microprocessor-based square wave generator. Of course, other circuit configurations can be used for peak detection, which can be selected according to specific needs; these will not be illustrated here.

Claims

1. A sinusoidal excitation circuit for a flux-type current sensor, characterized in that, The sine wave excitation circuit comprises: a square wave generator for generating a square wave signal; a resonant oscillator connected to the square wave generator and generating at least a sine wave signal of a fundamental frequency based on the square wave signal generated by the square wave generator, and loading the generated sine wave signal to a magnetic core, wherein the frequency of the fundamental frequency is consistent with the frequency of the square wave signal; an excitation signal sampling feedback circuit connected to the square wave generator and adaptively connected to the magnetic core to transmit the magnetic core excitation signal sampled by the adaptively connected magnetic core to the square wave generator, wherein the excitation signal sampling feedback circuit comprises a signal conditioning circuit and a peak detection circuit.

2. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 1, characterized by: The resonant oscillator comprises a resonant oscillation operational amplifier OA1, wherein the non-inverting terminal of the resonant oscillation operational amplifier OA1 is grounded, the inverting terminal of the resonant oscillation operational amplifier is connected to one end of a capacitor C1, the other end of the capacitor C1 is connected to one end of a capacitor C2 and the output terminal of the square wave generator; the other end of the capacitor C2 is connected to the output terminal of the resonant oscillation operational amplifier OA1 and one end of a capacitor C3, and the other end of the capacitor C3 forms the output terminal of the resonant oscillator, so as to connect the output terminal of the formed resonant oscillator to the first end of the magnetic core; the second end of the magnetic core is grounded through a magnetic core current detection resistor.

3. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 2, characterized by: Further comprising an amplitude regulation unit for regulating the amplitude state of the sine wave signal, wherein the output terminal of the square wave generator is adaptively connected to the resonant oscillator through the amplitude regulation unit.

4. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 3, characterized by: The amplitude regulation unit comprises a first voltage dividing resistor and a second voltage dividing resistor, wherein one end of the first voltage dividing resistor is connected to the output terminal of the square wave generator, and the other end of the first voltage dividing resistor is adaptively connected to one end of the second voltage dividing resistor, the capacitor C1 and the capacitor C2; at least the first voltage dividing resistor is configured as a variable resistor among the first voltage dividing resistor and the second voltage dividing resistor.

5. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 2, characterized by: Further comprising a frequency regulation unit for regulating the frequency state of the sine wave signal, wherein the frequency regulation unit is adaptively connected to the resonant oscillation operational amplifier OA1.

6. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 5, characterized by: The frequency regulation unit comprises a frequency regulation resistor, wherein one end of the frequency regulation resistor is connected to the inverting terminal of the resonant oscillation operational amplifier OA1, and the other end of the frequency regulation resistor is connected to the output terminal of the resonant oscillation operational amplifier OA1; the frequency regulation resistor is a variable resistor.

7. The sinusoidal excitation circuit for a fluxgate current sensor according to any one of claims 2 to 6, characterized in that: The peak detection circuit is connected to the first end of the magnetic core, and the signal conditioning circuit is connected to the second end of the magnetic core, wherein the signal conditioning circuit and the peak detection circuit are respectively connected to the square wave generator through an ADC circuit.

8. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 7, characterized by: The signal conditioning circuit comprises a signal conditioning operational amplifier OA2, wherein the non-inverting terminal of the signal conditioning operational amplifier OA2 is connected to a reference voltage unit, wherein the reference voltage unit comprises a resistor R7 and a resistor R8, one end of the resistor R7 and one end of the resistor R8 are both connected to the non-inverting terminal of the signal conditioning operational amplifier OA2, the other end of the resistor R8 is grounded, and the other end of the resistor R7 receives a reference voltage VREF; the inverting terminal of the signal conditioning operational amplifier OA2 is connected to one end of a resistor R5, one end of a resistor R6 and one end of a capacitor C4; The other end of the resistor R5 is connected with the second end of the magnetic core, and the other end of the resistor R6 and the other end of the capacitor C4 are connected with the output end of the signal conditioning operational amplifier OA2; The output end of the signal conditioning operational amplifier OA2 is connected with the square wave generator through the ADC circuit.

9. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 7, characterized by: The peak detection circuit comprises a voltage follower, a detection current limiting resistor and a peak locking unit connected in sequence, wherein The voltage follower is connected with the first end of the magnetic core, The peak locking unit is connected with the square wave generator through the ADC circuit.

10. The sinusoidal excitation circuit for a magnetic flux type current sensor according to claim 9, characterized by: The voltage follower comprises a detection operational amplifier OA3, wherein The non-inverting input terminal of the detection operational amplifier OA3 is connected with the first end of the magnetic core, the inverting input terminal of the detection operational amplifier OA3 is connected with the output end of the detection operational amplifier OA3, and the output end of the detection operational amplifier OA3 is connected with the detection current limiting resistor; The peak locking unit comprises a peak locking diode and a peak locking capacitor, wherein the anode of the peak locking diode is connected with the detection current limiting resistor, the cathode of the peak locking diode is connected with one end of the peak locking capacitor, and the other end of the peak locking capacitor is connected with the ground. The other end of the peak locking capacitor is connected with the ground.

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