Current measurement circuit and method of photoelectric conversion device

Abstract

The invention provides a current measuring circuit and method for a photoelectric conversion device, and the circuit comprises a trans-impedance amplifier which is used for amplifying a current signal of the device and converting the current signal into a voltage signal; the high-pass filtering circuit is used for performing high-pass filtering on the voltage signal; the filter matrix comprises an all-pass filter and a low-pass filter; the first programmed switch is used for selectively outputting an output signal of one of the filter matrixes; the voltage follower is used for following an output signal of the first programmed switch; the subtractor with adjustable gain is used for acquiring the difference between the output signals of the voltage follower and the high-pass filter; the second programmed switch is used for selectively outputting an output signal of one of the high-pass filter, the subtracter and the voltage follower; the ADC module is used for collecting an output signal of the second programmed switch; and the main controller is used for controlling the programmed switch and acquiring a target current measurement value according to an output signal of the ADC module. According to the invention, functions of gain adjustability, bandwidth adjustability and calibration correction can be considered.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric detection technology, and in particular to a current measurement circuit and method for a photoelectric conversion device. Background Art

[0002] A photodiode (PD) is a photoelectric conversion device that converts light into current. It is currently widely used in optical communications, lidar, laser ranging, and other fields. During operation, the PD operates under reverse bias conditions, with the PD's anode (A) connected to the negative power supply and the cathode (C) connected to a positive voltage. Under these conditions, the current flowing through the PD in the absence of light is called dark current, typically in the picoamps or nanoamps range depending on the material. In precision applications, dark current must be measured and calibrated. When light is present, the current flowing through the PD is called photocurrent, which is proportional to the input optical power.

[0003] Depending on product requirements, PDs can be packaged in different forms as discrete devices, or integrated into photonic integrated circuits (PICs) as integrated devices, such as monitor photodiodes (MPDs), which are used to monitor the internal optical path of PICs.

[0004] Regardless of how the PD's form factor changes, PD current measurement is required for both pre-shipment screening and post-delivery product applications. The measurement focus varies at different stages. PD current measurement requirements are primarily categorized into the following three types: 1) Static current measurement: dark current and photocurrent measurement under constant optical power, often seen in PD screening tests before shipment; 2) Dynamic current measurement: high-speed, high-bandwidth photoelectric signal conversion, commonly seen in applications such as optical communications and lidar; 3) Current calibration and correction: Eliminate bias signals such as dark current from the measurement results, which is often seen in precision optical signal measurement applications.

[0005] The circuits required for the three PD current measurement scenarios mentioned above are also different, and usually a dedicated circuit needs to be designed for each scenario. The biggest difference between these circuits is bandwidth. The biggest common point is that they use a trans-impedance amplifier (TIA) as the core to build peripheral circuits to achieve gain and bandwidth control. TIA uses the virtual short and virtual open characteristics of the op amp to amplify the input current by using a very high resistance feedback resistor. The amplification factor of the TIA is the resistance of the feedback resistor, which is usually tens of megahertz (10 7 ) ohms, or even G (10 9 )ohm.

[0006] The following are examples of PD current measurement patent applications published in the past two years, which generally correspond to one of the three measurement requirements mentioned above: Example 1: The patent application with publication number CN117630636A provides a dark current test circuit and system for a PD chip. This circuit corresponds to the aforementioned PD current measurement requirement 1) and is used to measure dark current. Figure 1 As shown in the figure, amplifier U1A and resistors R1-R3 form a TIA, with gain controlled by S1. However, this circuit lacks bandwidth control, meaning it cannot specifically address noise mixed in with the signal. Furthermore, this circuit incorporates analog switch S1 within the TIA. Analog switches typically have leakage currents in the order of picoamps or nanoamps, which are also amplified by the TIA by a factor of a million, resulting in significant offset errors in the circuit's output.

[0007] Example 2: Patent application number CN113670345A provides a low-noise photodetection device for photocurrent signal decomposition. This circuit corresponds to the aforementioned PD current measurement requirement 2) and is used to separate the AC component from the PD current. Figure 2 As shown, this circuit uses two TIAs, comprising amplifiers OPA1 and OPA2. The TIA input stage of OPA2 incorporates a DC-blocking capacitor, C2, to extract the high-frequency component of the PD current. However, this circuit lacks gain control, and its bandwidth is limited to two unadjustable settings. Furthermore, and more importantly, the parallel connection of the two TIA input stages with the PD prevents the two TIAs from having the same gain if the op amp loads are unbalanced or the feedback resistors are unequal. This means that the circuit's output exhibits linearity errors, which become more pronounced with increasing photocurrent.

[0008] Example 3: Patent application number CN209787128U provides a transimpedance amplifier and a transimpedance amplifier circuit, which corresponds to the aforementioned PD current measurement requirement 3) and is used for current calibration and correction. Figure 3 As shown, the essence of this circuit is to add an adjustable bias resistor 122 to the TIA input stage on the basis of the patent application CN117630636A to compensate for the PD dark current. Figure 3 The gain control unit 122 in the patent application CN117630636A corresponds to S1 and R1-R3. However, this circuit still does not have bandwidth control capability, and its DC drift elimination capability depends on the debugging effect.

[0009] It can be seen that the main defect of the existing PD current measurement circuit is that it cannot simultaneously take into account the gain adjustment, bandwidth adjustment, and calibration correction functions, and thus cannot adapt to different PD current measurement scenarios, such as static measurement, dynamic measurement, and calibration correction scenarios. Summary of the Invention

[0010] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a current measurement circuit and method for a photoelectric conversion device, which takes into account the gain adjustment, bandwidth adjustment and calibration correction functions to meet the different current measurement requirements of the photoelectric conversion device.

[0011] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a current measurement circuit for a photoelectric conversion device, comprising: A transimpedance amplifier is used to amplify the current signal of the photoelectric conversion device and convert the amplified current signal into a corresponding voltage signal; A high-pass filter circuit, used for performing high-pass filtering on the voltage signal; a filter matrix, comprising an all-pass filter and a plurality of low-pass filters with different cutoff frequencies, wherein the all-pass filter is used to output the voltage signal, and the low-pass filter is used to perform low-pass filtering on the voltage signal; a first programmable switch, configured to select and output the output signal of the all-pass filter or one of the low-pass filters; a voltage follower, configured to buffer and stabilize the output signal of the first program-controlled switch; a gain-adjustable subtractor, configured to obtain a difference between an output signal of the voltage follower and an output signal of the high-pass filter circuit, and perform gain adjustment on the difference; a second programmable switch, configured to select and output an output signal of one of the high-pass filter circuit, the subtractor, and the voltage follower; an ADC module, configured to perform analog-to-digital conversion on the output signal of the second programmable switch; A main controller is used to control the selection of the first program-controlled switch and the second program-controlled switch, and obtain a target current measurement value of the photoelectric conversion device according to the output signal of the ADC module.

[0012] Preferably, the transimpedance amplifier comprises: a first amplifier, wherein a negative phase input terminal of the first amplifier is connected to the output terminal of the photoelectric conversion device, and a positive phase input terminal of the first amplifier is connected to a bias voltage; A feedback resistor is connected between the negative phase input terminal and the output terminal of the first amplifier.

[0013] Preferably, the transimpedance amplifier further includes a feedback capacitor connected in parallel with the feedback resistor.

[0014] Preferably, the high-pass filter circuit includes: Second amplifier; a high-pass filter connected between the output terminal of the transimpedance amplifier and the non-inverting input terminal of the second amplifier; A balancing resistor is connected between the negative phase input terminal and the output terminal of the second amplifier.

[0015] Preferably, the high-pass filter comprises: a high-pass capacitor connected between the output terminal of the transimpedance amplifier and the non-inverting input terminal of the second amplifier; a high-pass voltage divider resistor connected between the non-inverting input terminal of the second amplifier and ground; The resistance of the balancing resistor is equal to that of the high-pass voltage-dividing resistor.

[0016] Preferably, the voltage follower includes a third amplifier, a positive phase input terminal of the third amplifier is connected to the output terminal of the first programmable switch, and a negative phase input terminal and an output terminal of the third amplifier are connected.

[0017] Preferably, the parameters of the second amplifier and the third amplifier are the same.

[0018] Preferably, the first programmable switch is a single-pole multi-throw switch, which includes a moving end, multiple fixed ends and a control end, one of the fixed ends is connected to the output end of the all-pass filter, and the remaining fixed ends are connected one-to-one with the output ends of each low-pass filter, the moving end is connected to the input end of the voltage follower, and the control end is connected to the main controller.

[0019] Preferably, the subtractor comprises: Fourth amplifier; a first peripheral resistor connected between the output terminal of the high-pass filter circuit and the negative phase input terminal of the fourth amplifier; A second peripheral resistor is connected between the negative phase input terminal and the output terminal of the fourth amplifier; a third peripheral resistor connected between the output terminal of the voltage follower and the non-inverting input terminal of the fourth amplifier; a fourth peripheral resistor connected between the non-inverting input terminal of the fourth amplifier and ground; The second peripheral resistor and the fourth peripheral resistor are adjustable resistors, the first peripheral resistor and the third peripheral resistor have the same resistance value, and the second peripheral resistor and the fourth peripheral resistor have the same resistance value.

[0020] Preferably, the accuracy of the first peripheral resistor, the second peripheral resistor, the third peripheral resistor and the fourth peripheral resistor is better than 0.1%.

[0021] Preferably, the second programmable switch includes three single-pole single-throw switches, the first single-pole single-throw switch is connected between the output end of the high-pass filter circuit and the input end of the ADC module, the second single-pole single-throw switch is connected between the output end of the subtractor and the input end of the ADC module, and the third single-pole single-throw switch is connected between the output end of the voltage follower and the input end of the ADC module, wherein the on and off of the three single-pole single-throw switches are controlled by the main controller.

[0022] Preferably, the low-pass filter is an RC low-pass filter; The main controller is an MCU and an FPGA; and / or, The photoelectric conversion device is a photodiode.

[0023] In a second aspect, the present invention provides a current measurement method for a photoelectric conversion device, applicable to the main controller in the current measurement circuit as described above, and the method is used in a static current measurement scenario, comprising: Controlling the first program-controlled switch to select and output the output signal of the all-pass filter; Controlling the second programmable switch to select and output the output signal of the subtractor to the ADC module; Acquire a target current measurement value of the photoelectric conversion device according to an output signal of the ADC module, wherein the target current measurement value is a static current value of the photoelectric conversion device; In which, in the static current measurement scenario, the output signal of the transimpedance amplifier includes the static current signal of the photoelectric conversion device and the AC electromagnetic interference signal, the high-pass filter is used to output the AC electromagnetic interference signal, and the subtractor is used to subtract the output signal of the transimpedance amplifier from the output signal of the high-pass filter to obtain the static current signal.

[0024] In a third aspect, the present invention provides a current measurement method for a photoelectric conversion device, applicable to the main controller in the current measurement circuit as described above, the method being used in a dynamic current measurement scenario, comprising: controlling the second programmable switch to selectively output the output signal of the high-pass filter circuit to the ADC module, wherein the output signal of the high-pass filter circuit is an AC component in the output signal of the transimpedance amplifier, and the AC component is a dynamic current signal of the photoelectric conversion device; A target current measurement value of the photoelectric conversion device is acquired according to an output signal of the ADC module, where the target current measurement value is a dynamic current value of the photoelectric conversion device.

[0025] In a fourth aspect, the present invention provides a current measurement method for a photoelectric conversion device, applicable to the main controller in the current measurement circuit as described above, wherein the method is used in a current calibration and correction scenario, and comprises performing the following steps once or periodically: When the photoelectric conversion device is shielded from light, the first programmable switch is controlled to select and output the output signal of the all-pass filter, and the second programmable switch is controlled to select and output the output signal of the subtractor, and then a dark current measurement value of the photoelectric conversion device is obtained according to the output signal of the ADC module, wherein, when the photoelectric conversion device is shielded from light, the output signal of the transimpedance amplifier includes the dark current signal of the photoelectric conversion device and an AC electromagnetic interference signal, and the high-pass filter is used to output the AC electromagnetic interference signal, and the subtractor is used to subtract the output signal of the transimpedance amplifier from the output signal of the high-pass filter to obtain the dark current signal; When the photoelectric conversion device passes light, controlling the first programmable switch to select and output the output signal of the low-pass filter with a specified cutoff frequency, and controlling the second programmable switch to select and output the output signal of the voltage follower, and then obtaining a photocurrent measurement value of the photoelectric conversion device according to the output signal of the ADC module; The target current measurement value of the photoelectric conversion device is obtained by subtracting the latest dark current measurement value from the latest photocurrent measurement value, and the target current measurement value is the calibrated photocurrent of the photoelectric conversion device.

[0026] By adopting the above technical solution, the present invention has the following beneficial effects: The present invention adjusts the first programmable switch and the second programmable switch through the main controller, and cooperates with the filter matrix to achieve bandwidth adjustment and automatic calibration. At the same time, by adjusting the gain of the subtractor, gain adjustment can also be achieved. Thus, the circuit and method of the present invention have both bandwidth adjustment, gain adjustment, and automatic calibration correction functions, and can cover the static measurement scenario, dynamic measurement scenario, and precision measurement scenario of the current of the photoelectric conversion device, with flexible control and diverse effects. In addition, by placing bandwidth control and gain control in the post-stage circuit of the transimpedance amplifier, the present invention can also simplify the high-gain transimpedance amplifier as much as possible, thereby reducing the output bias. At the same time, when measuring the quiescent current, the cable between the photoelectric conversion device and the transimpedance amplifier will couple spatial AC noise, thereby introducing AC electromagnetic interference signals, and the interference signals will be amplified by the transimpedance amplifier, resulting in the signal output by the transimpedance amplifier containing a large amount of AC electromagnetic interference signals and a weak quiescent current signal. The present invention uses a subtractor to subtract the output signal of the transimpedance amplifier from the output signal of the high-pass filter to obtain the quiescent current signal, which can make the measured quiescent current more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A circuit diagram of a PD current measurement circuit in a first example of the prior art; Figure 2 is a circuit diagram of a PD current measurement circuit in a second example of the prior art; Figure 3 is a circuit diagram of a PD current measurement circuit in a third example of the prior art; Figure 4 1 is a circuit diagram of a current measurement circuit of a photoelectric conversion device in Example 1 of the present invention; Figure 5 1 is a circuit diagram of a current measurement circuit of a photoelectric conversion device in Example 2 of the present invention; Figure 6 This is a circuit diagram of a current measurement circuit of a photoelectric conversion device in Example 3 of the present invention; Figure 7 This is a circuit diagram of a current measurement circuit of a photoelectric conversion device in Example 4 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] The terms used in this disclosure are for the purpose of describing specific embodiments only and are not intended to limit the disclosure. As used in this disclosure and the appended claims, the singular forms "a," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0030] As previously mentioned, the main drawback of existing PD current measurement circuits is their inability to simultaneously address gain adjustment, bandwidth adjustment, and calibration correction functions, making them incompatible with different PD current measurement scenarios, such as static measurement, dynamic measurement, and calibration correction. For example, the solution described in patent application CN117630636A achieves gain adjustment, but the bandwidth is fixed and cannot be targeted to address input noise. The solution described in patent application CN113670345A achieves AC / DC separation and can be considered as two-band bandwidth, but it lacks gain control and calibration correction capabilities. Furthermore, it uses two TIA shunts to achieve AC / DC separation, which introduces significant linearity errors if circuit parameters become unbalanced. The solution described in patent application CN209787128U, while capable of gain adjustment and calibration correction, lacks bandwidth adjustment and relies on on-site commissioning for calibration results.

[0031] In addition, existing technologies have the following drawbacks: 1) Existing circuits all introduce new devices into the TIA's high-impedance loop. The leakage current introduced by these new devices will be amplified by the TIA by a million times, introducing new bias errors. For example, patent application CN117630636A introduces an analog switch into the TIA's high-impedance loop, patent application CN209787128U introduces an op amp into the TIA's high-impedance loop, and patent application CN113670345B does not ostensibly introduce new devices into the TIA's high-impedance loop, but in essence introduces a new TIA circuit. 2) Implementing bandwidth control in existing circuits requires simultaneous acquisition of multiple ADC (Analog to Digital Converter) modules, which is costly. For example, achieving AC / DC separation in patent application CN113670345B requires two ADCs to simultaneously acquire data: one ADC for the DC component and the other for the AC component.

[0032] In view of this, the present invention provides a current measurement circuit and method for a photoelectric conversion device with programmable bandwidth. This circuit combines gain control, bandwidth control, and automatic calibration and correction, making it adaptable to almost all PD current measurement scenarios, such as static measurement, dynamic measurement, and calibration and correction. Furthermore, the circuit does not add any components to the TIA high-resistance loop, minimizing TIA input stage leakage current. The circuit implements bandwidth control and calibration and correction via analog switches, offering flexible control and diverse effects. The circuit can implement both pre-calibration and real-time online calibration, enabling dark current calibration and correction without manual intervention.

[0033] The present invention is described in detail below by taking a PD (photodiode) as an example of a photoelectric conversion device. However, it should be understood that the present invention does not impose any specific limitation on the type of photoelectric conversion device.

[0034] Example 1 This embodiment provides a current measurement circuit for a photoelectric conversion device. Figure 4 As shown, the circuit mainly includes a transimpedance amplifier 1, a high-pass filter circuit 2, a filter matrix 3, a first programmable switch SW1, a voltage follower 4, a subtractor 5, a second programmable switch SW2, an ADC module 6 and a main controller 7.

[0035] In this embodiment, a transimpedance amplifier 1 is connected to a power supply (PD) and is configured to amplify the PD's current signal and convert the amplified current signal into a corresponding voltage signal Vtia. A high-pass filter circuit 2 is configured to perform high-pass filtering on the voltage signal Vtia. A filter matrix 3 includes an all-pass filter and multiple low-pass filters with different cutoff frequencies. The all-pass filter outputs the voltage signal Vtia, while the low-pass filters perform low-pass filtering on the voltage signal Vtia. A first programmable switch SW1 is configured to select the output signal of the all-pass filter or one of the low-pass filters. A voltage follower 4 is configured to buffer and stabilize the output signal of the first programmable switch SW1. A subtractor 5 is configured to obtain the difference between the output signal of the voltage follower 4 and the output signal of the high-pass filter circuit 2 and to perform gain adjustment on the difference. The gain of the subtractor 5 is adjustable. A second programmable switch SW2 is configured to select the output signal of one of the high-pass filter circuit 2, the subtractor 5, and the voltage follower 4. An ADC module 6 is configured to perform analog-to-digital conversion on the output signal of the second programmable switch SW2. The main controller 7 is used to control the selection of the first program-controlled switch SW1 and the second program-controlled switch SW2 , and obtain the target current measurement value of the photoelectric conversion device according to the output signal of the ADC module 6 .

[0036] The following combination Figure 4 , each module in the circuit of this embodiment is specifically described: In this embodiment, a transimpedance amplifier (TIA) 1 primarily comprises a first amplifier OPA1 and a feedback resistor Rf. The negative input of the first amplifier OPA1 is connected to the output of the power supply (PD), while the positive input is connected to a bias voltage Vbias. Feedback resistor Rf is connected between the negative input and output of the first amplifier OPA1. The transimpedance amplifier 1 amplifies the PD current with an amplification factor equal to the resistance value of Rf. The bias voltage Vbias is typically generated by other DAC circuits and is not discussed in this embodiment. Due to the op amp's virtual short circuit, the PD operates at a reverse bias voltage of Vbias. Adjusting Vbias adjusts the PD bias voltage.

[0037] In addition, the transimpedance amplifier 1 may further include a feedback capacitor Cf connected in parallel with the feedback resistor Rf. Cf and Rf are connected in parallel to compensate for the dynamic performance of the TIA. The capacitance value of Cf depends on the resistance value of Rf and the parasitic parameters of the PD.

[0038] In this embodiment, the high-pass filter circuit 2 includes a second amplifier OPA2, a high-pass filter connected between the output terminal of the transimpedance amplifier 1 and the positive phase input terminal of the second amplifier OPA2, and a balancing resistor Rb connected between the negative phase input terminal and the output terminal of the second amplifier OPA2.

[0039] Preferably, the high-pass filter adopts a first-order RC high-pass filter, which specifically includes: a high-pass capacitor Ch connected between the output end of the transimpedance amplifier 1 and the non-inverting input end of the second amplifier OPA2, and a high-pass voltage divider resistor Rh connected between the non-inverting input end of the second amplifier OPA2 and the ground. Among them, the cut-off frequency of the high-pass filter is The balancing resistor Rb has the same resistance as the high-pass voltage divider resistor Rh, and is used to balance the op amp input bias current. The input signal of OPA2 is the TIA output signal Vtia, and the output signal Vop2 is the AC component contained in Vtia. This component is usually electromagnetic noise in static measurement and an optical switch signal in dynamic measurement.

[0040] In this embodiment, the voltage follower 4 includes a third amplifier OPA3. The non-inverting input terminal of the third amplifier OPA3 is connected to the output terminal of the first programmable switch SW1, and the negative input terminal of the third amplifier OPA3 is connected to the output terminal thereof. The second amplifier OPA2 and the third amplifier OPA3 have the same parameters and preferably use the same operational amplifier model. In this way, the output bias introduced by the operational amplifier itself can be offset in the subtractor 5.

[0041] exist Figure 4In the embodiment shown, the filter matrix 3 is exemplarily shown to include 6 filters, specifically first-order RC low-pass filters, respectively composed of RL1 and CL1, ..., RL6 and CL6, and the cutoff frequency of each RC low-pass filter is , where x = 1 to 6. A set of RC parameters is reserved, with R = 0 and C = NC (no welding). The corresponding filter is an all-pass filter. It should be understood that this embodiment does not impose any specific limitation on the number of filters in filter matrix 3.

[0042] In this embodiment, the first programmable switch SW1 preferably adopts a single-pole multi-throw switch, which specifically includes a moving end, multiple fixed ends and a control end, and one of the fixed ends is connected to the output end of the all-pass filter, and the remaining fixed ends are connected one-to-one with the output ends of each low-pass filter; the moving end is connected to the input end of the voltage follower 4; and the control end is connected to the main controller 7.

[0043] exist Figure 4 In the illustrated embodiment, the first programmable switch SW1 is exemplarily shown as a 1-to-6 single-pole multi-throw switch, i.e., it has one active terminal and six fixed terminals. The six fixed terminals are connected one-to-one to the six filters in the filter matrix 3, so that the output signals of the six filters are selected by SW1 and then transmitted to the voltage follower 4. Obviously, the output signal Vop2 of the voltage follower 4 is the signal after the voltage signal Vtia is filtered by the selected filter. If the selected filter is an all-pass filter, the output signal of the voltage follower 4 is equal to the Vtia signal.

[0044] In this embodiment, the subtractor 5 includes: a fourth amplifier OPA4, a first peripheral resistor Rg1, a second peripheral resistor Rg2, a third peripheral resistor Rg3, and a fourth peripheral resistor Rg4. The first peripheral resistor Rg1 is connected between the output of the high-pass filter circuit 2 and the negative phase input of the fourth amplifier OPA4; the second peripheral resistor Rg2 is connected between the negative phase input and the output of the fourth amplifier OPA4; the third peripheral resistor Rg3 is connected between the output of the voltage follower 4 and the positive phase input of the fourth amplifier OPA4; and the fourth peripheral resistor Rg4 is connected between the positive phase input of the fourth amplifier OPA4 and ground.

[0045] In this embodiment, the second peripheral resistor Rg2 and the fourth peripheral resistor Rg4 are adjustable resistors, and the first peripheral resistor Rg1 and the third peripheral resistor Rg3 have the same resistance value, and the second peripheral resistor Rg2 and the fourth peripheral resistor Rg4 have the same resistance value. The gain of the subtractor 5 is K = Rg2 / Rg1 = Rg4 / Rg3. The input signal of the subtractor 5 is the output signal of OPA2 and OPA3. The output signal of the subtractor 5 is It should be understood that the gain of the subtractor 5 can be adjusted by adjusting the resistance values of the second peripheral resistor Rg2 and the fourth peripheral resistor Rg4.

[0046] Preferably, the accuracy of the first peripheral resistor Rg1, the second peripheral resistor Rg2, the third peripheral resistor Rg3 and the fourth peripheral resistor Rg4 is better than 0.1% to improve the common mode rejection ratio of OPA4.

[0047] In this embodiment, the second programmable switch SW2 includes three single-pole single-throw switches SW21~SW23, and the first single-pole single-throw switch SW21 is connected between the output end of the high-pass filter circuit 2 and the input end of the ADC module 6, the second single-pole single-throw switch SW22 is connected between the output end of the subtractor 5 and the input end of the ADC module 6, and the third single-pole single-throw switch SW23 is connected between the output end of the voltage follower 4 and the input end of the ADC module 6. The on and off of the three single-pole single-throw switches SW21~SW23 are all controlled by the main controller 7.

[0048] In this embodiment, the output signals of the three amplifiers OPA2-OPA4 are selected via the second programmable switch SW2 and fed into the ADC module 6 for acquisition. The ADC module performs analog-to-digital conversion on the acquired signals and outputs corresponding digital signals to the main controller 7. In this embodiment, the main controller 7 can be a general-purpose controller such as an MCU or FPGA, so that the main controller 7 can obtain the target current measurement value of the photoelectric conversion device based on the output signal of the ADC module 6.

[0049] Preferably, all capacitors in the circuit of this embodiment are of NP0 temperature grade to reduce the overall temperature drift of the circuit.

[0050] The working principle of the circuit of this embodiment is described below: 1) In the static current measurement scenario: Close SW22 and open SW21 and SW23.

[0051] For example, when measuring PD dark current, this current is typically very weak (in the picoamp range). However, the cable from the PD to the TIA is often long, and the electromagnetic interference current introduced by this cable is amplified by the TIA. The Vtia signal output by the TIA then contains a significant amount of AC electromagnetic interference and a weak dark current signal. Switch SW1 is set to a filter with R = 0 and C = NC (i.e., an all-pass filter). In this case, Vopa3 = Vtia, Vopa2 = the AC component of Vtia, and Vopa4 = the amplified signal obtained by subtracting Vopa3 from Vopa2. The bandwidth of the entire circuit is close to DC, and the residual AC energy in Vopa4 is minimal, primarily the effective dark current signal. This signal is collected by the ADC module 6 and sent to the main controller 7 for processing, thereby obtaining the PD's quiescent current value.

[0052] 2) Dynamic current measurement scenario: Close SW21 and open SW22 and SW23.

[0053] For example, when measuring the switching photocurrent, the current changes rapidly, requiring a high circuit bandwidth and no DC component. In this case, OPA2 can be considered an AC coupler, and ADC module 6 only collects the AC component of Vtia, which is the dynamic current value of the PD.

[0054] 3) Current calibration scenario: First, close only SW22 to measure the DC component of the current, and then close only SW23.

[0055] For example, in a precise current measurement scenario, the PD can be shielded from light, with only SW22 closed. The measured PD dark current is then stored in the main controller 7. The PD is then allowed to pass light, with only SW23 closed. A suitable filter bandwidth is selected through SW1 for precise current measurement. The main controller 7 then subtracts the dark current from the measured value for calibration. During the measurement process, the PD dark current can also be periodically measured and calibrated based on the latest dark current, achieving real-time online calibration.

[0056] It can be seen that the actions of SW1 and SW2 in the above three measurement scenarios are shown in Table 1 below: Table 1

[0057] Compared with the prior art, the main improvements of the circuit in this embodiment are: 1) This embodiment achieves bandwidth adjustment and automatic calibration by adjusting the first and second programmable switches through the main controller and cooperating with the filter matrix. Gain adjustment can be achieved by adjusting the gain of the subtractor. As a result, the present invention has the functions of adjustable bandwidth, adjustable gain, and automatic calibration and correction. It also has flexible control and achieves various effects, covering static measurement scenarios, dynamic measurement scenarios, and precision measurement scenarios of PD current.

[0058] 2) When measuring static current, such as dark current, the prior art usually directly uses the low-frequency signal in the output signal of the TIA output by the low-pass filter to obtain the dark current. However, the present application uses a subtractor to subtract the output signal of the TIA from the output signal of the high-pass filter to obtain the dark current. This is because the cable from the PD to the TIA is usually long, and this cable will couple spatial AC noise, thereby introducing AC electromagnetic interference signals, and the interference signal will be amplified by the TIA. At this time, the Vtia signal output by the TIA contains a large amount of AC electromagnetic interference signals and weak dark current signals. The AC electromagnetic interference signal can be removed by the subtractor. Therefore, the static current (such as dark current) measured by the present invention is more accurate than that of the prior art.

[0059] 3) The transimpedance amplifier in this embodiment includes only the first amplifier OPA1, the feedback resistor Rf, and the feedback capacitor Cf. No devices are added to the TIA high-impedance loop, thereby minimizing the TIA input stage leakage current and reducing the output bias.

[0060] 4) This embodiment can realize dark current pre-calibration, and can also periodically measure the PD dark current during the measurement process and calibrate the dark current according to the latest dark current, thereby realizing real-time online calibration, and dark current calibration and correction can be achieved without manual intervention and debugging.

[0061] 5) This embodiment only requires four operational amplifiers (OPAs), two sets of analog switches (SWs), and one ADC. This allows for multiple uses on one board, is low-cost, and is simple and easy to implement.

[0062] Example 2 This embodiment provides a current measurement method for a photoelectric conversion device, which is suitable for execution by the main controller 7 provided in Example 1. Figure 5 As shown, the method specifically includes the following steps: S11, control the first programmable switch SW1 to select the output signal of the all-pass filter, that is, SW1 selects the filter with R=0 and C=NC; S12, controlling the second programmable switch SW2 to select the output signal of the subtractor 5 to be output to the ADC module 6, that is, only SW22 in SW2 is closed; S13, obtaining a target current measurement value of the photoelectric conversion device according to the output signal of the ADC module 6, where the target current measurement value is the static current value of the photoelectric conversion device; In the quiescent current measurement scenario, the output signal Vtia of the transimpedance amplifier 1 includes the quiescent current signal of the photoelectric conversion device and the AC electromagnetic interference signal. The high-pass filter 2 is used to output the AC electromagnetic interference signal. The subtractor is used to subtract the output signal Vtia of the transimpedance amplifier 1 from the output signal of the high-pass filter to remove the AC electromagnetic interference signal and obtain the quiescent current signal.

[0063] As can be seen, in this embodiment, since the output signal of the all-pass filter is the output signal Vtia of the transimpedance amplifier 1, and the output signal of the high-pass filter circuit 2 is the AC component of Vtia, after the subtractor 5 subtracts and amplifies the two, the residual AC energy in its output signal Vopa4 is extremely small, and it mainly contains the effective static current signal. This signal is collected by the ADC module 6 and sent to the main controller 7. The target current measurement value obtained by the main controller 7 is the static current value of the photoelectric conversion device. Therefore, the method of this embodiment is suitable for static measurement scenarios of photoelectric conversion devices.

[0064] Example 3 This embodiment provides a current measurement method for a photoelectric conversion device, which is suitable for execution by the main controller 7 provided in Example 1. Figure 6 As shown, the method specifically includes the following steps: S21, controlling the second programmable switch SW2 to select and output the output signal of the high-pass filter circuit 2 to the ADC module (i.e., only SW21 in SW2 is closed), wherein the output signal of the high-pass filter circuit 2 is the AC component of the output signal of the transimpedance amplifier, and the AC component is the dynamic current signal of the photoelectric conversion device; S22 , obtaining a target current measurement value of the photoelectric conversion device according to the output signal of the ADC module 6 .

[0065] In this embodiment, since OPA2 functions as an AC coupler when SW21 is closed, the signal collected by ADC module 6 is the AC component Vtia. This signal is collected by ADC module 6 and sent to main controller 7. The target current measurement value obtained by main controller 7 is the dynamic current value of the photoelectric conversion device. Therefore, the method of this embodiment is suitable for dynamic measurement scenarios of photoelectric conversion devices.

[0066] Example 4 This embodiment provides a current measurement method for a photoelectric conversion device, which is suitable for execution by the main controller 7 provided in Example 1. Figure 7 As shown, the method includes performing the following steps once or periodically: S31: When the photoelectric conversion device is shielded from light, the first programmable switch SW1 is controlled to select outputting the output signal of the all-pass filter (i.e., SW1 selects the filter with R=0 and C=NC), and the second programmable switch SW2 is controlled to select outputting the output signal of the subtractor 5 (i.e., only SW22 of SW2 is closed). Then, the dark current measurement value of the photoelectric conversion device is obtained based on the output signal of the ADC module 6. When the photoelectric conversion device is shielded from light, the output signal of the transimpedance amplifier includes the dark current signal of the photoelectric conversion device and an AC electromagnetic interference signal, and the high-pass filter is used to output the AC electromagnetic interference signal. The subtractor is used to subtract the output signal of the transimpedance amplifier from the output signal of the high-pass filter to remove the AC electromagnetic interference signal and obtain the dark current signal of the PD (S32). When the photoelectric conversion device is light-permeable, the first programmable switch SW1 is controlled to select outputting the output signal of the low-pass filter with a specified cutoff frequency, and the second programmable switch SW2 is controlled to select outputting the output signal of the voltage follower 4 (i.e., only SW23 of SW2 is closed). Then, the photocurrent measurement value of the photoelectric conversion device is obtained based on the output signal of the ADC module 6.

[0067] S33, current calibration can be achieved by subtracting the latest dark current measurement value from the latest photocurrent measurement value to obtain a target current measurement value of the photoelectric conversion device, and the target current measurement value is the calibration photocurrent of the photoelectric conversion device.

[0068] The method of this embodiment is explained below with a specific application example: In this application example, amplifier OPA1 is the ADA4622, amplifiers OPA2 through OPA4 are the OP07C, and the PD specification is G12180-020A. Its typical dark current at 1V reverse bias is 1.5nA. The TIA's Rf is 5MΩ, Cf is 27pF, and the maximum input optical power is 1uW. Precision measurement of the input optical power is desired. The OPA2 peripheral circuit parameters are Ch = 1uF, Rb = Rh = 100kΩ. The high-pass filter cutoff frequency is: The six filter parameters of the input stage of the amplifier OPA3 are shown in Table 2 below: Table 2

[0069] The peripheral resistors of the fourth amplifier OPA4 are Rg1=Rg2=Rg3=Rg4=1k, that is, the gain (ie, amplification factor) of the subtractor 5 is 1.

[0070] For the above application example, the specific implementation process of this embodiment is as follows: First, the PD is shielded from light, SW1 selects the first group of RC filters, SW22 is closed, SW21 and SW23 are opened, and the main controller 7 reads the sampled voltage Vdark of the ADC module 6 and stores it in the internal memory.

[0071] Then, when light enters the PD, SW1 selects the second group of RC filters, closes SW23, opens SW21 and SW22, and the main controller 7 reads the sampled voltage Vlight of the ADC module 6 and subtracts Vdark to obtain the calibrated photocurrent.

[0072] If you want to increase the circuit bandwidth, you can switch SW1 to a filter with a higher cutoff frequency.

[0073] It can be seen that the method of this embodiment is applicable to the current calibration and correction scenario of the photoelectric conversion device.

[0074] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A current measurement circuit for a photoelectric conversion device, characterized in that: include: A transimpedance amplifier is used to amplify the current signal of the photoelectric conversion device and convert the amplified current signal into a corresponding voltage signal; A high-pass filter circuit, used for performing high-pass filtering on the voltage signal; a filter matrix, comprising an all-pass filter and a plurality of low-pass filters with different cutoff frequencies, wherein the all-pass filter is used to output the voltage signal, and the low-pass filter is used to perform low-pass filtering on the voltage signal; a first programmable switch, configured to select and output the output signal of the all-pass filter or one of the low-pass filters; a voltage follower, configured to buffer and stabilize the output signal of the first program-controlled switch; a gain-adjustable subtractor, configured to obtain a difference between an output signal of the voltage follower and an output signal of the high-pass filter circuit, and perform gain adjustment on the difference; a second programmable switch, configured to select and output an output signal of one of the high-pass filter circuit, the subtractor, and the voltage follower; an ADC module, configured to perform analog-to-digital conversion on the output signal of the second programmable switch; A main controller is used to control the selection of the first program-controlled switch and the second program-controlled switch, and obtain a target current measurement value of the photoelectric conversion device according to the output signal of the ADC module.

2. The current measurement circuit according to claim 1, wherein: The transimpedance amplifier comprises: a first amplifier, wherein a negative phase input terminal of the first amplifier is connected to the output terminal of the photoelectric conversion device, and a positive phase input terminal of the first amplifier is connected to a bias voltage; A feedback resistor is connected between the negative phase input terminal and the output terminal of the first amplifier.

3. The current measuring circuit according to claim 2, wherein: The transimpedance amplifier further includes a feedback capacitor connected in parallel with the feedback resistor.

4. The current measuring circuit according to claim 1, wherein: The high-pass filter circuit comprises: Second amplifier; a high-pass filter connected between the output terminal of the transimpedance amplifier and the non-inverting input terminal of the second amplifier; A balancing resistor is connected between the negative phase input terminal and the output terminal of the second amplifier.

5. The current measuring circuit according to claim 4, wherein: The high-pass filter comprises: a high-pass capacitor connected between the output terminal of the transimpedance amplifier and the non-inverting input terminal of the second amplifier; a high-pass voltage divider resistor connected between the non-inverting input terminal of the second amplifier and ground; The resistance of the balancing resistor is equal to that of the high-pass voltage-dividing resistor.

6. The current measuring circuit according to claim 5, wherein: The voltage follower includes a third amplifier, a positive phase input terminal of the third amplifier is connected to the output terminal of the first program-controlled switch, and a negative phase input terminal and an output terminal of the third amplifier are connected.

7. The current measuring circuit according to claim 6, wherein: The parameters of the second amplifier and the third amplifier are the same.

8. The current measuring circuit according to claim 1, wherein: The first programmable switch is a single-pole multi-throw switch, which includes a moving end, multiple fixed ends and a control end. One of the fixed ends is connected to the output end of the all-pass filter, and the remaining fixed ends are connected one-to-one with the output ends of each low-pass filter. The moving end is connected to the input end of the voltage follower, and the control end is connected to the main controller.

9. The current measuring circuit according to claim 1, wherein: The subtractor comprises: Fourth amplifier; a first peripheral resistor connected between the output terminal of the high-pass filter circuit and the negative phase input terminal of the fourth amplifier; A second peripheral resistor is connected between the negative phase input terminal and the output terminal of the fourth amplifier; a third peripheral resistor connected between the output terminal of the voltage follower and the non-inverting input terminal of the fourth amplifier; a fourth peripheral resistor connected between the non-inverting input terminal of the fourth amplifier and ground; The second peripheral resistor and the fourth peripheral resistor are adjustable resistors, the first peripheral resistor and the third peripheral resistor have the same resistance value, and the second peripheral resistor and the fourth peripheral resistor have the same resistance value.

10. The current measuring circuit according to claim 9, wherein: The accuracy of the first peripheral resistor, the second peripheral resistor, the third peripheral resistor and the fourth peripheral resistor is better than 0.1%.

11. The current measuring circuit according to any one of claims 1 to 10, characterized in that: The second programmable switch includes three single-pole single-throw switches, the first single-pole single-throw switch is connected between the output end of the high-pass filter circuit and the input end of the ADC module, the second single-pole single-throw switch is connected between the output end of the subtractor and the input end of the ADC module, and the third single-pole single-throw switch is connected between the output end of the voltage follower and the input end of the ADC module, wherein the on and off of the three single-pole single-throw switches are controlled by the main controller.

12. The current measuring circuit according to any one of claims 1 to 10, characterized in that: The low-pass filter is an RC low-pass filter; The main controller is an MCU and an FPGA; and / or, The photoelectric conversion device is a photodiode.

13. A current measurement method for a photoelectric conversion device, applicable to the main controller in the current measurement circuit according to any one of claims 1 to 12, the method being used in a static current measurement scenario, comprising: Controlling the first programmable switch to select and output the output signal of the all-pass filter; Controlling the second programmable switch to select and output the output signal of the subtractor to the ADC module; Acquire a target current measurement value of the photoelectric conversion device according to an output signal of the ADC module, wherein the target current measurement value is a static current value of the photoelectric conversion device; In which, in the static current measurement scenario, the output signal of the transimpedance amplifier includes the static current signal of the photoelectric conversion device and the AC electromagnetic interference signal, the high-pass filter is used to output the AC electromagnetic interference signal, and the subtractor is used to subtract the output signal of the transimpedance amplifier from the output signal of the high-pass filter to obtain the static current signal.

14. A current measurement method for a photoelectric conversion device, applicable to the main controller in the current measurement circuit according to any one of claims 1 to 12, the method being used in a dynamic current measurement scenario, comprising: controlling the second programmable switch to selectively output the output signal of the high-pass filter circuit to the ADC module, wherein the output signal of the high-pass filter circuit is an AC component in the output signal of the transimpedance amplifier, and the AC component is a dynamic current signal of the photoelectric conversion device; A target current measurement value of the photoelectric conversion device is acquired according to an output signal of the ADC module, where the target current measurement value is a dynamic current value of the photoelectric conversion device.

15. A current measurement method for a photoelectric conversion device, applicable to the main controller in the current measurement circuit according to any one of claims 1 to 12, wherein the method is used in a current calibration and correction scenario, and comprises performing the following steps once or periodically: When the photoelectric conversion device is shielded from light, the first programmable switch is controlled to select and output the output signal of the all-pass filter, and the second programmable switch is controlled to select and output the output signal of the subtractor, and then the dark current measurement value of the photoelectric conversion device is obtained according to the output signal of the ADC module, wherein, When the photoelectric conversion device is shielded from light, the output signal of the transimpedance amplifier includes a dark current signal of the photoelectric conversion device and an AC electromagnetic interference signal, and the high-pass filter is used to output the AC electromagnetic interference signal, and the subtractor is used to subtract the output signal of the transimpedance amplifier from the output signal of the high-pass filter to obtain the dark current signal; When the photoelectric conversion device passes light, controlling the first programmable switch to select and output the output signal of the low-pass filter with a specified cutoff frequency, and controlling the second programmable switch to select and output the output signal of the voltage follower, and then obtaining a photocurrent measurement value of the photoelectric conversion device according to the output signal of the ADC module; The target current measurement value of the photoelectric conversion device is obtained by subtracting the latest dark current measurement value from the latest photocurrent measurement value, and the target current measurement value is the calibrated photocurrent of the photoelectric conversion device.

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