An analog front-end circuit and integrated circuit for AC / DC current separation

Abstract

The present invention provides an analog front-end circuit and integrated circuit for AC and DC current separation detection, and relates to the field of integrated circuits. An injection module receives photocurrent from a photodiode, performs parasitic capacitance isolation on the photocurrent, and transmits the generated stable AC and DC current to a feedback module and the source follower module. The feedback module converts the stable AC and DC current into an AC voltage corresponding to the AC component and transmits it to an integration module, while the AC voltage is output through a low-pass filter. The integration module reverses the AC voltage and applies it to the source follower module to suppress the DC component, separate the AC component and the DC component, and thus obtain an AC voltage and a DC voltage. While detecting the AC signal, the present invention improves the accuracy of the DC signal detection result, and the power consumption and noise of the entire circuit are low. The detection range of the entire analog front-end circuit is configurable, and the control circuit is simple.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and in particular to an analog front-end circuit and an integrated circuit for AC and DC current separation detection. Background Art

[0002] Current analog front-end circuits for detecting weak current signals are designed to separate and detect mixed current signals containing AC and DC signals while simultaneously amplifying the weak current signal. However, due to their circuit structure, when detecting AC signals, these circuits significantly affect the DC signal corresponding to the DC component. This results in poor DC signal detection accuracy, high power consumption, and high noise levels across the entire circuit. Summary of the Invention

[0003] In view of the above problems, the present invention is proposed to provide an analog front-end circuit and integrated circuit for AC and DC current separation detection that solve the above problems or partially solve the above problems.

[0004] A first aspect of an embodiment of the present invention provides an analog front-end circuit for AC and DC current separation detection, the analog front-end circuit comprising: an injection module, a feedback module, an integration module, and a source follower module;

[0005] The injection module receives the photocurrent from the photodiode, performs parasitic capacitance isolation on the photocurrent, and transmits the generated stable AC and DC current to the feedback module and the source follower module, wherein the stable AC and DC current includes an AC component and a DC component;

[0006] The feedback module converts the stable AC and DC currents into an AC voltage corresponding to the AC component and transmits the AC voltage to the integration module. Meanwhile, the AC voltage is output through a low-pass filter.

[0007] The integration module inverts the AC voltage and applies it to the source follower module to suppress the DC component, separate the AC component and the DC component, and thus obtain the AC voltage and the DC voltage.

[0008] Optionally, the feedback module converts the AC component into an AC voltage, amplifies the AC voltage, transmits it to the integration module, and outputs it through a low-pass filter.

[0009] Optionally, the feedback module, the integration module and the source follower module form a negative feedback loop.

[0010] Optionally, the injection module includes: a first PMOS tube and a first operational amplifier;

[0011] The source of the first PMOS tube is connected to the inverting terminal of the first operational amplifier and receives the photocurrent;

[0012] The gate of the first PMOS transistor is connected to the output terminal of the first operational amplifier;

[0013] The drain of the first PMOS tube is connected to the feedback module and the source follower module;

[0014] A non-inverting terminal of the first operational amplifier receives a bias voltage.

[0015] Optionally, the feedback module includes: an adjustable capacitor, a first adjustable resistor, and a second operational amplifier;

[0016] The first end of the adjustable capacitor, the first end of the adjustable first resistor, and the inverting end of the second operational amplifier are all connected to the drain of the first PMOS transistor;

[0017] The second end of the adjustable capacitor is connected to the second end of the adjustable resistor, the output end of the second operational amplifier, and the integration module respectively, and the second end of the adjustable capacitor outputs the AC voltage to the low-pass filter and the integration module;

[0018] The non-inverting terminal of the second operational amplifier receives a reference voltage.

[0019] Optionally, the integration module includes: an integration resistor, an integration capacitor and a third operational amplifier;

[0020] The first end of the integrating resistor is connected to the second end of the adjustable capacitor, the second end of the adjustable resistor, and the output end of the second operational amplifier respectively;

[0021] The second end of the integrating resistor is connected to the second end of the integrating capacitor and the inverting end of the third operational amplifier respectively;

[0022] The first end of the integrating capacitor is connected to the output end of the third operational amplifier and the source follower module respectively;

[0023] The non-inverting terminal of the third operational amplifier receives the reference voltage.

[0024] Optionally, the source follower module includes: a second PMOS transistor and a second adjustable resistor;

[0025] The drain of the second PMOS transistor is connected to the drain of the first PMOS transistor and the inverting terminal of the second operational amplifier respectively;

[0026] The gate of the second PMOS transistor is connected to the first end of the integrating capacitor and the output end of the third operational amplifier respectively;

[0027] The source of the second PMOS tube is connected to the first end of the second adjustable resistor and outputs the DC voltage;

[0028] The second end of the second adjustable resistor is grounded.

[0029] Optionally, by dynamically adjusting the sizes of the first adjustable resistor, the second adjustable resistor, and the adjustable capacitor, the photocurrents of different sizes can be separated into corresponding AC components and DC components;

[0030] By adjusting the sizes of the first adjustable resistor, the second adjustable resistor, the integrating capacitor, the integrating resistor, and the adjustable capacitor, the bandwidth of the analog front-end circuit can be limited under conditions of photocurrents of different sizes.

[0031] Optionally, the magnitude of the AC voltage is detected at the second end of the adjustable capacitor, and the magnitude of the DC voltage is detected at the source of the second PMOS transistor, and the transfer function H(S), high-pass cutoff frequency f2, and low-pass cutoff frequency f1 of the analog front-end circuit are obtained as follows:

[0032]

[0033] Wherein, s represents the generalization of Fourier transform, R1 represents the resistance of the integrating resistor, R2 represents the resistance of the second adjustable resistor, R f represents the resistance of the first adjustable resistor, C1 represents the capacitance of the integrating capacitor, and C f Indicates the capacitance value of the adjustable capacitor.

[0034] A second aspect of an embodiment of the present invention provides an integrated circuit, which includes the analog front-end circuit as described in any one of the first aspects above.

[0035] The analog front-end circuit for AC and DC current separation detection provided by the present invention has an injection module that receives photocurrent from a photodiode, isolates the photocurrent with parasitic capacitance, and transmits the generated stable AC and DC currents to a feedback module and a source follower module; the feedback module converts the AC component into an AC voltage and transmits it to an integration module, while the AC voltage is output through a low-pass filter; the integration module reverses the AC voltage and applies it to the source follower module to suppress the DC component, separate the AC component and the DC component, and thus obtain an AC voltage and a DC voltage.

[0036] The feedback module converts the photocurrent into a voltage signal, amplifies it, and transmits it to the subsequent circuit. The integration module inverts the voltage signal and applies it to the input, suppressing the DC component of the stable AC and DC currents. This achieves separation of the DC and AC components, while limiting the bandwidth of the analog front end and reducing circuit noise. While detecting AC signals, it also improves the accuracy of DC signal detection results. The entire circuit also features low power consumption and low noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0038] Figure 1 This is a schematic diagram of the structure of the analog front-end circuit commonly used to detect AC and DC currents;

[0039] Figure 2 It is a structural diagram of an analog front-end circuit for AC and DC current separation detection according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] The inventors found that the analog front end commonly used to detect AC and DC currents is generally composed of a transimpedance amplifier, an adjustable gain module, and a low-pass filter. Figure 1 Figure 2 shows the structure of a commonly used analog front-end circuit for detecting AC and DC currents. This circuit includes a transimpedance amplifier (TIA), an adjustable gain module (PA), and a low-pass filter (LPF). The TIA converts the weak photocurrent signal into a voltage signal. The PA functions as a high-pass filter, amplifying the converted voltage signal. The low-pass filter (LPF) then limits the signal bandwidth, thereby suppressing noise.

[0042] However, the commonly used analog front-end circuit mentioned above has a significant impact on the DC signal corresponding to the DC component when detecting AC signals, resulting in poor accuracy of DC signal detection results, high power consumption and high noise of the entire circuit.

[0043] In response to the above problems, the inventor creatively proposed an analog front-end circuit for AC and DC current separation detection of the present invention. The analog front-end circuit of the present invention is described in detail below.

[0044] The analog front-end circuit for AC / DC current separation detection proposed in the present invention includes: an injection module, a feedback module, an integration module and a source follower module. The injection module receives the photocurrent from the photodiode, performs parasitic capacitance isolation on the photocurrent, and transmits the generated stable AC / DC current to the feedback module and the source follower module. The stable AC / DC current includes: an AC component and a DC component. Under normal circumstances, due to the parasitic capacitance of the photodiode (generally several hundred pico-farads), it will affect the photocurrent and have a greater impact on the stability of the feedback module, the integration module and the source follower module. Therefore, at the input end of the photocurrent signal, the structure of the injection module is used to isolate the parasitic capacitance, so that the parasitic capacitance of the stable AC / DC current is much smaller than the parasitic capacitance of the photodiode, thereby avoiding affecting the stability of the feedback module, the integration module and the source follower module.

[0045] The feedback module converts the stable AC and DC currents into AC voltages corresponding to the AC components and transmits them to the integration module. The AC voltage is then output through a low-pass filter. The feedback module converts the AC components into AC voltages, amplifies the AC voltage, transmits it to the integration module, and outputs it through a low-pass filter. This facilitates the measurement and subsequent use of the AC voltage.

[0046] The integrator module inverts the AC voltage and applies it to the source follower module to suppress the DC component, separating the AC and DC components to generate AC and DC voltages. Essentially, the feedback module, integrator module, and source follower module form a negative feedback loop, improving the accuracy of DC signal detection results while also reducing power consumption and noise across the entire circuit.

[0047] In order to better illustrate the analog front-end circuit of the present invention, refer to Figure 2 , which shows a schematic structural diagram of a preferred analog front-end circuit in an embodiment of the present invention, Figure 2 It includes: photodiode PD, first PMOS tube M0, first operational amplifier OP1, adjustable capacitor C f , the first adjustable resistor R f , second operational amplifier OP2, integrating resistor R1, integrating capacitor C1, third operational amplifier OP3, second PMOS transistor M1 and second adjustable resistor R2.

[0048] The injection module includes: a first PMOS transistor M0 and a first operational amplifier OP1. The source of the first PMOS transistor M0 is connected to the inverting terminal of the first operational amplifier OP1 and receives the photocurrent from the photodiode PD.

[0049] The gate of the first PMOS transistor M0 is connected to the output terminal of the first operational amplifier OP1; the drain of the first PMOS transistor M0 is connected to the feedback module and the source follower module; the in-phase terminal of the first operational amplifier OP1 receives the bias voltage V BP .

[0050] The feedback module includes: adjustable capacitor C f , the first adjustable resistor R f , the second op amp OP2; adjustable capacitor C f The first end of the adjustable first resistor R f The first end of the operational amplifier OP1 and the inverting end of the second operational amplifier OP2 are both connected to the drain of the first PMOS transistor M0.

[0051] Adjustable capacitor C f The second end of the adjustable resistor R f The second end of the second operational amplifier OP2 and the integration module are connected respectively, and the adjustable capacitor C f The second end of the output AC voltage to the low-pass filter LPF and the integration module. The non-inverting terminal of the second operational amplifier OP2 receives the reference voltage V CM The output of the low-pass filter LPF outputs an AC voltage V out_ac .

[0052] The integration module includes: an integration resistor R1, an integration capacitor C1 and a third operational amplifier OP3. The first end of the integration resistor R1 is connected to the adjustable capacitor C f The second end of the adjustable resistor R f and the output terminal of the second operational amplifier OP2 are respectively connected.

[0053] The second end of the integrating resistor R1 is connected to the second end of the integrating capacitor C1 and the inverting end of the third operational amplifier OP3 respectively; the first end of the integrating capacitor C1 is connected to the output end of the third operational amplifier OP3 and the source follower module respectively; the non-inverting end of the third operational amplifier OP3 receives the reference voltage V CM .

[0054] The source follower module includes: a second PMOS transistor M1 and a second adjustable resistor R2. The drain of the second PMOS transistor M1 is connected to the drain of the first PMOS transistor M0 and the inverting terminal of the second operational amplifier OP2 respectively; the gate of the second PMOS transistor M1 is connected to the first terminal of the integrating capacitor C1 and the output terminal of the third operational amplifier OP3 respectively; the source of the second PMOS transistor M1 is connected to the first terminal of the second adjustable resistor R2, and outputs a DC voltage V out_dc ; The second end of the second adjustable resistor R2 is grounded.

[0055] The feedback module converts the stable photocurrent into a voltage signal and amplifies it to the subsequent circuit, where the DC component is isolated and the AC component is converted into AC voltage through the feedback module. Figure 2At the middle node a, the adjustable capacitor C f The integration module inverts the AC voltage signal and applies it to the input (i.e., the input of the source follower module), suppressing the DC component of the stable photocurrent, thereby separating the DC and AC quantities. AC and DC voltages are obtained.

[0056] The analog front-end circuit of the present invention dynamically adjusts the first adjustable resistor R f , the second adjustable resistor R2 and the adjustable capacitor C f The respective sizes are used to separate the corresponding AC components and DC components of the photocurrents of different sizes.

[0057] The analog front-end circuit of the present invention adjusts the first adjustable resistor R f , the second adjustable resistor R2, the integral capacitor C1, the integral resistor R1 and the adjustable capacitor C f The respective sizes are used to limit the bandwidth of the analog front-end circuit under different photocurrent conditions.

[0058] The AC voltage is at the adjustable capacitor C f The second end ( Figure 2 The DC voltage is detected at the source of the second PMOS tube M1 ( Figure 2 The transfer function H(S), high-pass cutoff frequency f2, and low-pass cutoff frequency f1 of the analog front-end circuit are detected as follows:

[0059]

[0060] Where s represents the generalization of Fourier transform (s=jw, w represents Fourier transform), R1 represents the resistance of the integrating resistor, R2 represents the resistance of the second adjustable resistor, R f represents the resistance of the first adjustable resistor, C1 represents the capacitance of the integral capacitor, and C f Indicates the capacitance value of the adjustable capacitor.

[0061] According to the expression of H(S), the spectrum of the entire analog front-end circuit is a spectrum diagram similar to a bandpass filter. According to the expressions of f1 and f2, it can be seen that by adjusting the first adjustable resistor R f , the second adjustable resistor R2, the integral capacitor C1, the integral resistor R1 and the adjustable capacitor C f The respective sizes are used to limit the bandwidth of the analog front-end circuit under different photocurrents, thereby reducing the noise of the analog front-end circuit.

[0062] Based on the above analog front-end circuit, an embodiment of the present invention further provides an integrated circuit, which includes any of the above analog front-end circuits.

[0063] Through the above examples, the analog front-end circuit provided by the present invention, the injection module receives the photocurrent from the photodiode, isolates the photocurrent with parasitic capacitance, and transmits the generated stable AC and DC currents to the feedback module and the source follower module; the feedback module converts the AC component into an AC voltage and transmits it to the integration module, and the AC voltage is output through a low-pass filter; the integration module reverses the AC voltage and applies it to the source follower module to suppress the DC component, separate the AC component and the DC component, and thus obtain AC voltage and DC voltage.

[0064] The feedback module converts the photocurrent into a voltage signal, amplifies it, and transmits it to the subsequent circuit. The integration module inverts the voltage signal and applies it to the input, suppressing the DC component of the stable AC and DC currents. This achieves separation of the DC and AC components and simultaneously limits the bandwidth of the analog front-end, reducing circuit noise. While detecting AC signals, this improves the accuracy of DC signal detection results. The entire circuit also features low power consumption and noise, a configurable detection range, and a simple control circuit.

[0065] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0066] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. An analog front-end circuit for AC and DC current separation detection, characterized in that: The analog front-end circuit includes: an injection module, a feedback module, an integration module and a source follower module; The injection module receives the photocurrent from the photodiode, performs parasitic capacitance isolation on the photocurrent, and transmits the generated stable AC and DC current to the feedback module and the source follower module, wherein the stable AC and DC current includes an AC component and a DC component; The feedback module converts the stable AC and DC currents into an AC voltage corresponding to the AC component and transmits the AC voltage to the integration module. Meanwhile, the AC voltage is output through a low-pass filter. The integration module inverts the AC voltage and applies it to the source follower module to suppress the DC component, separate the AC component and the DC component, and thus obtain the AC voltage and the DC voltage; Wherein, the feedback module includes: an adjustable capacitor, a first adjustable resistor, and a second operational amplifier; The first end of the adjustable capacitor, the first end of the first adjustable resistor, and the inverting end of the second operational amplifier are all connected to the injection module; The second end of the adjustable capacitor is connected to the second end of the first adjustable resistor, the output end of the second operational amplifier, and the integration module respectively, and the second end of the adjustable capacitor outputs the AC voltage to the low-pass filter and the integration module; The non-inverting terminal of the second operational amplifier receives a reference voltage.

2. The analog front-end circuit according to claim 1, wherein: The feedback module converts the AC component into an AC voltage, amplifies the AC voltage, transmits it to the integration module, and outputs it through a low-pass filter.

3. The analog front-end circuit according to claim 1, wherein: The feedback module, the integration module and the source follower module form a negative feedback loop.

4. The analog front-end circuit according to claim 1, wherein: The injection module includes: a first PMOS tube and a first operational amplifier; The source of the first PMOS tube is connected to the inverting terminal of the first operational amplifier and receives the photocurrent; The gate of the first PMOS transistor is connected to the output terminal of the first operational amplifier; The drain of the first PMOS tube is connected to the feedback module and the source follower module; A non-inverting terminal of the first operational amplifier receives a bias voltage.

5. The analog front-end circuit according to claim 4, wherein: The integration module includes: an integration resistor, an integration capacitor and a third operational amplifier; The first end of the integrating resistor is connected to the second end of the adjustable capacitor, the second end of the first adjustable resistor, and the output end of the second operational amplifier respectively; The second end of the integrating resistor is connected to the second end of the integrating capacitor and the inverting end of the third operational amplifier respectively; The first end of the integrating capacitor is connected to the output end of the third operational amplifier and the source follower module respectively; The non-inverting terminal of the third operational amplifier receives the reference voltage.

6. The analog front-end circuit according to claim 5, characterized in that: The source follower module includes: a second PMOS tube and a second adjustable resistor; The drain of the second PMOS transistor is connected to the drain of the first PMOS transistor and the inverting terminal of the second operational amplifier respectively; The gate of the second PMOS transistor is connected to the first end of the integrating capacitor and the output end of the third operational amplifier respectively; The source of the second PMOS tube is connected to the first end of the second adjustable resistor and outputs the DC voltage; The second end of the second adjustable resistor is grounded.

7. The analog front-end circuit according to claim 6, wherein: By dynamically adjusting the sizes of the first adjustable resistor, the second adjustable resistor, and the adjustable capacitor, the photocurrent of different sizes can be separated into corresponding AC components and DC components; By adjusting the sizes of the first adjustable resistor, the second adjustable resistor, the integral capacitor, the integral resistor, and the adjustable capacitor, the bandwidth of the analog front-end circuit can be limited under conditions of photocurrents of different sizes.

8. The analog front-end circuit according to claim 6, wherein: The magnitude of the AC voltage is detected at the second end of the adjustable capacitor, and the magnitude of the DC voltage is detected at the source of the second PMOS transistor. The transfer function H(S), high-pass cutoff frequency f2, and low-pass cutoff frequency f1 of the analog front-end circuit are obtained as follows: Wherein, s represents the generalization of Fourier transform, R1 represents the resistance of the integrating resistor, R2 represents the resistance of the second adjustable resistor, and R f represents the resistance of the first adjustable resistor, C1 represents the capacitance of the integrating capacitor, and C f Indicates the capacitance value of the adjustable capacitor.

9. An integrated circuit, characterized in that: The integrated circuit includes the analog front-end circuit according to any one of claims 1-8.

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