CN116260402A - Photoelectric detection circuit - Google Patents

Abstract

The application provides a photodetection circuit, including: a photo detection circuit comprising: the sensor comprises a photosensitive sensor, a first transistor, a transimpedance amplifier, a first feedback resistor and a low-pass filter module. The first end of the photosensitive sensor is connected with a power supply, the second end of the photosensitive sensor, the first end of the first transistor, the first end of the transimpedance amplifier and the first end of the first feedback resistor are connected to a first common end, the second end of the transimpedance amplifier is externally connected with a first bias voltage, the third end of the transimpedance amplifier, the second end of the first feedback resistor and the first end of the low-pass filter module are connected to a second common end, and the second end of the low-pass filter module is connected with the second end of the first transistor; the third terminal of the first transistor is grounded. The photoelectric detection circuit provided by the application does not need to convert the low-frequency current signal into a digital signal through the digital circuit, eliminates the current signal generated by ambient light, reduces loop bandwidth, reduces complexity of a signal chain and reduces chip cost.

Description

Photoelectric detection circuit

technical field

The invention relates to the technical field of integrated circuits, in particular to a photoelectric detection circuit.

Background technique

Photoplethysmography (PPG) is a non-invasive detection method for detecting changes in blood volume in living tissue by means of photoelectric means. When the light passes through the skin tissue, the contraction and expansion of the blood vessels cause a certain change in the light signal. When performing PPG detection, it can be detected by the PPG photoelectric detection circuit. The PPG photoelectric detection circuit includes a light source and a photosensitive diode, which can be irradiated by the light source. One side of the living tissue receives the changed light signal after passing through the living tissue through the photosensitive sensor, and then detects the change of blood volume through the current signal generated by the photosensitive sensor.

The traditional PPG photoelectric detection circuit may be affected by ambient light when the light source is irradiating living tissue for detection, resulting in deviations in test results. In order to eliminate the influence of ambient light, the traditional PPG photoelectric detection circuit can be optimized. The optimized circuit includes light source, photodiode, transimpedance amplifier, analog-to-digital converter, digital circuit and low-frequency current source. PPG photoelectric detection circuit The detection principle is that the light source irradiates the living tissue. After the photosensitive sensor receives the light signal, it receives the current signal generated by the photosensitive sensor through the transimpedance amplifier, and converts the analog electrical signal into a digital signal through an analog-to-digital converter. The digital control circuit analyzes the digital signal to obtain a low-frequency electrical signal (that is, the electrical signal generated by ambient light), and then controls the low-frequency current source to generate a reverse low-frequency current signal to offset the ambient light signal.

However, the traditional photoelectric detection circuit needs to convert the low-frequency current signal of ambient light into a digital signal for reverse cancellation, and there is a problem of high loop bandwidth.

Contents of the invention

In order to overcome the technical problem of high loop bandwidth in the prior art, a photoelectric detection circuit that does not need to convert low-frequency current signals of ambient light into digital signals for reverse cancellation is provided.

In a first aspect, the present application provides a photoelectric detection circuit, including: a photosensitive sensor, a first transistor, a transimpedance amplifier, a first feedback resistor, and a low-pass filter module; the first end of the photosensitive sensor is connected to a power supply, and the first end of the photosensitive sensor Two terminals, the first terminal of the first transistor, the first terminal of the transimpedance amplifier and the first terminal of the first feedback resistor are connected to the first common terminal, the second terminal of the transimpedance amplifier is externally connected with the first bias voltage, and the transimpedance amplifier The third terminal of the amplifier, the second terminal of the first feedback resistor and the first terminal of the low-pass filter module are connected to the second common terminal, and the second terminal of the low-pass filter module is connected to the second terminal of the first transistor; the first The third terminal of the transistor is grounded;

The photosensitive sensor is used to receive the test light signal and the ambient light signal emitted by the light source, and convert the test light signal and the ambient light signal into a current signal. The current signal includes: a high-frequency test current signal and a low-frequency ambient current signal;

The transimpedance amplifier is used to receive the current signal, and transmit the voltage signal generated based on the current signal at both ends of the first feedback resistor to the low-pass filter module; the voltage signal includes a high-frequency voltage signal generated based on the test light signal, and a high-frequency voltage signal based on the ambient light low frequency voltage signal generated by the signal;

The low-pass filter module is used to absorb the high-frequency voltage signal in the voltage signal after receiving the voltage signal at both ends of the first feedback resistor, and transmit the low-frequency voltage signal to the first transistor, so that the first transistor generates a reverse low frequency current signal;

The transimpedance amplifier is also used to output a high-frequency electrical signal generated based on the test optical signal after receiving the reverse low-frequency current signal generated by the first transistor.

In one of the embodiments, the low-pass filter module includes: an error amplifier and a first capacitor; the first end of the error amplifier is connected to the third end of the transimpedance amplifier, the second end of the error amplifier, the first end of the first capacitor end and the second end of the first transistor are connected to the third common end, the third end of the error amplifier is externally connected with the second bias voltage; the second end of the first capacitor is grounded; the error amplifier, the first capacitor, the first transistor, the trans The impedance amplifier and the first feedback resistor form a negative feedback loop;

The first capacitor is used to absorb the high-frequency voltage signal transmitted by the error amplifier;

The error amplifier is used to transmit the low frequency voltage signal to the first transistor.

In one of the embodiments, the photodetection circuit further includes a second feedback resistor; the transimpedance amplifier is a differential transimpedance amplifier;

The first common end is respectively connected to the first end of the differential transimpedance amplifier and the first end of the first feedback resistor, and the second end of the differential transimpedance amplifier is connected to the first end of the second feedback resistor and externally connected to the first bias voltage ; The third terminal of the differential transimpedance amplifier, the second terminal of the first feedback resistor and the first terminal of the low-pass filter module are connected to the second common terminal, the fourth terminal of the differential transimpedance amplifier, the second terminal of the second feedback resistor The terminal and the third terminal of the low-pass filter module are connected to the second common terminal; the second terminal of the low-pass filter module is connected to the second terminal of the first transistor; the third terminal of the first transistor is grounded.

In one of the embodiments, the first transistor is an NMOS transistor; the gate of the NMOS transistor is connected to the second end of the low-pass filter module; the drain of the NMOS transistor is connected to the first end of the transimpedance amplifier; the source of the NMOS transistor grounded.

In one of the embodiments, the photodetection circuit further includes a second capacitor, and the second capacitor is connected in parallel with the first feedback resistor.

In a second aspect, the present application provides a photoelectric detection circuit, including: a photosensitive sensor, a second transistor, a transimpedance amplifier, a first feedback resistor, and a low-pass filter module; the first end of the second transistor, the first end of the transimpedance amplifier end, the first end of the first feedback resistor and the first end of the photosensitive sensor are connected to the fourth common terminal, and the second end of the photosensitive sensor is grounded; the second end of the transimpedance amplifier is externally connected with the first bias voltage, and the second end of the transimpedance amplifier The third terminal, the second terminal of the first feedback resistor and the first terminal of the low-pass filter module are connected to the fifth common terminal, the second terminal of the low-pass filter module is connected to the second terminal of the second transistor, and the second terminal of the second transistor The third end is connected to the power supply;

The photosensitive sensor is used to receive the test light signal and the ambient light signal emitted by the light source, and convert the test light signal and the ambient light signal into a current signal; the current signal includes: a high-frequency test current signal and a low-frequency ambient current signal;

The transimpedance amplifier is used to receive the current signal, and transmit the voltage signal generated based on the current signal at both ends of the first feedback resistor to the low-pass filter module; the voltage signal includes a high-frequency voltage signal generated based on the test light signal, and based on the environment Low-frequency voltage signals generated by optical signals;

The low-pass filter module is used to absorb the high-frequency voltage signal in the voltage signal after receiving the voltage signal at both ends of the first feedback resistor, and transmit the low-frequency voltage signal to the second transistor, so that the second transistor generates a reverse low frequency current signal;

The transimpedance amplifier is also used to output a high-frequency electrical signal generated based on the test optical signal after receiving the reverse low-frequency current signal generated by the second transistor.

In one of the embodiments, the low-pass filter module includes: an error amplifier and a first capacitor; the first end of the error amplifier is connected to the third end of the transimpedance amplifier, and the second end of the error amplifier is connected to the first end of the first capacitor. The terminals are respectively connected to the second terminal of the first transistor, and the third terminal of the error amplifier is externally connected to the second bias voltage; the second terminal of the first capacitor is connected to the power supply; the error amplifier, the first capacitor, the second transistor, and the transimpedance amplifier forming a negative feedback loop with the first feedback resistor;

The first capacitor is used to absorb the high-frequency voltage signal transmitted by the error amplifier;

An error amplifier is used to transmit the low frequency voltage signal to the second transistor.

In one of the embodiments, the photodetection circuit also includes a second feedback resistor; the transimpedance amplifier is a differential transimpedance amplifier; the first end of the second transistor, the first end of the differential transimpedance amplifier, the first end of the first feedback resistor terminal, the first end of the differential transimpedance amplifier and the first end of the photosensitive sensor are connected to the fourth common terminal; the second end of the differential transimpedance amplifier is connected to the first end of the second feedback resistor and externally connected to the first bias voltage; The second end of the second feedback resistor is respectively connected with the third end of the differential transimpedance amplifier and the first end of the low-pass filter module; the fourth end of the differential transimpedance amplifier is respectively connected with the second end of the first feedback circuit and the low-pass The third terminal of the filter module is connected; the second terminal of the low-pass filter module is connected with the second terminal of the second transistor; the third terminal of the second transistor is connected with the power supply.

In one embodiment, the first transistor is a PMOS transistor; the second terminal of the low-pass filter module is connected, the drain of the PMOS transistor is connected to the first terminal of the photosensitive sensor; the source of the PMOS transistor is connected to a power supply.

In one of the embodiments, the photodetection circuit further includes a second capacitor, and the second capacitor is connected in parallel with the first feedback resistor.

It can be seen from the above technical solutions that the present application provides a photoelectric detection circuit, including: a photosensitive sensor, a first transistor, a transimpedance amplifier, a first feedback resistor and a low-pass filter module. After receiving the test light signal and the environment light signal emitted by the light source, the photosensitive sensor converts the test light signal and the environment light signal into a high-frequency test current signal and a low-frequency environment current signal. The transimpedance amplifier receives the current signal, and transmits the high-frequency voltage signal generated based on the current signal based on the test light signal and the low-frequency voltage signal generated based on the ambient light signal at both ends of the first feedback resistor to the low-pass filter module. so that the low-pass filter module absorbs the high-frequency voltage signal in the voltage signal after receiving the voltage signal at both ends of the first feedback resistor, and transmits the low-frequency voltage signal to the first transistor, so that the first transistor generates a reverse low-frequency current signal. After receiving the reverse low-frequency current signal generated by the first transistor, the transimpedance amplifier outputs a high-frequency electrical signal generated based on the test light signal, without converting the low-frequency current signal into a digital signal through a digital circuit, and converting the ambient light to a digital signal. The elimination of the current signal reduces the loop bandwidth, reduces the complexity of the signal chain, and reduces the cost of the chip. In addition, compared with the traditional photoelectric detection circuit, the present application eliminates ambient light by simulating direct feedback, and the reaction speed of eliminating ambient light is faster.

Description of drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description serve to explain the principles of the invention.

Fig. 1 is a schematic structural diagram of a traditional photoelectric detection circuit device;

FIG. 2 is a schematic structural diagram of a photoelectric detection circuit in the first embodiment of the present application;

3 is a schematic structural diagram of a photoelectric detection circuit in a second embodiment of the present application;

4 is a schematic structural diagram of a photoelectric detection circuit in a third embodiment of the present application;

5 is a schematic structural diagram of a photoelectric detection circuit in a fourth embodiment of the present application;

6 is a schematic structural diagram of a photoelectric detection circuit in a fifth embodiment of the present application;

FIG. 7 is a schematic structural diagram of the photoelectric detection circuit in the sixth embodiment of the present application;

FIG. 8 is a schematic structural diagram of a photoelectric detection circuit in a seventh embodiment of the present application;

FIG. 9 is a schematic structural diagram of a photoelectric detection circuit in an eighth embodiment of the present application;

FIG. 10 is a schematic structural diagram of a photoelectric detection circuit in a ninth embodiment of the present application;

FIG. 11 is a schematic structural diagram of the photodetection circuit in the tenth embodiment of the present application.

Reference signs:

10-photoelectric detection circuit;

100-photosensitive sensor; 200-first transistor; 300-transimpedance amplifier; 400-first feedback resistor; 500-low-pass filter module; 600-power supply; 700-second feedback resistor; 800-second capacitor; 900- The third capacitor;

210-NMOS transistor; 310-differential transimpedance amplifier; 510-error amplifier; 520-first capacitor;

20-photoelectric detection circuit;

100-photosensitive sensor; 300-transimpedance amplifier; 400-first feedback resistor; 500-low-pass filter module; 600-power supply; 700-second feedback resistor; 800-second capacitor; 900-third capacitor; 1000- second transistor;

310-differential transimpedance amplifier; 510-error amplifier; 520-first capacitor; 1010-PMOS transistor.

Detailed ways

In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, and are not intended to limit the present application.

The serial numbers for components in this application, such as "first", "second", etc., are only used to distinguish the described objects, and do not have any order or technical meaning. The "connection" and "connection" mentioned in this application all include direct and indirect connection (connection) unless otherwise specified. In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", The orientation or positional relationship indicated by "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description , rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and thus should not be construed as limiting the application.

In the present application, unless otherwise clearly specified and limited, a first feature being "on" or "under" a second feature may mean that the first and second features are in direct contact, or that the first and second features are indirect through an intermediary. touch. Moreover, "above", "above" and "above" the first feature on the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. "Below", "beneath" and "beneath" the first feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is less horizontally than the second feature.

The photoelectric detection circuit method can be realized by using a PPG photoelectric detection circuit device. In the commonly used PPG photoelectric detection circuit device, the elimination of ambient light is generally carried out by a digital method. As shown in Figure 1, the traditional photoelectric detection circuit device includes: light source a, photodiode b, transimpedance amplifier module c, analog-to-digital converter d, digital circuit e and low-frequency current source f, the detection principle of PPG photoelectric detection circuit The light source is used to irradiate the living tissue. After receiving the light signal, the photosensitive sensor receives the current signal generated by the photosensitive sensor through a transimpedance amplifier, and converts the analog electrical signal into a digital signal through an analog-to-digital converter. The digital control circuit analyzes the digital signal to obtain a low-frequency electrical signal (that is, the electrical signal generated by ambient light), and then controls the low-frequency current source to generate a reverse low-frequency current signal to offset the ambient light signal. However, in the traditional photoelectric detection circuit device, it is necessary to convert the low-frequency current signal of ambient light into a digital signal for reverse cancellation, and there is a problem of high loop bandwidth. Therefore, how to adopt a photoelectric detection circuit that does not need to convert the low-frequency current signal of ambient light into a digital signal for reverse cancellation has become a research direction.

Based on this, the embodiment of the present application provides a photoelectric detection circuit. The technical solution provided by the embodiment of the present application is as follows, and the technical solution provided by the embodiment of the present application will be described in detail in conjunction with the accompanying drawings.

As shown in FIG. 2 , FIG. 2 is a photodetection circuit 10 provided by the embodiment of the present application, including a photosensitive sensor 100 , a first transistor 200 , a transimpedance amplifier 300 , a first feedback resistor 400 and a low-pass filter module 500 . Wherein, the first end of the photosensitive sensor 100 is connected with the power supply 600, the second end of the photosensitive sensor 100, the first end of the first transistor 200, the first end of the transimpedance amplifier 300 and the first end of the first feedback resistor 400 are connected At the first common end, the second end of the transimpedance amplifier 300 is externally connected with the first bias voltage, the third end of the transimpedance amplifier 300 and the second end of the first feedback resistor 400 are connected to the first end of the low-pass filter module 500 At the second common end, the second end of the low-pass filter module 500 is connected to the second end of the first transistor 500200, and the third end of the first transistor 200 is grounded.

Wherein, the first bias voltage V1 is used to stabilize the voltage value of the first terminal of the transimpedance amplifier 300 .

The photosensitive sensor 100 is used to receive the test light signal and the environment light signal emitted by the light source, and convert the test light signal and the environment light signal into a current signal, and the current signal includes: a high frequency test current signal and a low frequency environment current signal.

It should be noted that the light source may be a high-frequency electrical signal sent by an LED. Optionally, an electrical signal with a frequency greater than 1Khz can be used as a high-frequency current signal. Electrical signals not greater than 1Khz are regarded as low-frequency electrical signals.

During the process of photoelectric detection, since the test environment cannot be completely protected from external light, the photosensitive sensor 100 can receive the test light signal emitted by the light source and the ambient light signal.

The transimpedance amplifier 300 is used to receive the current signal, and transmit the voltage signal generated based on the current signal across the first feedback resistor 400 to the low-pass filter module 500 . Wherein, the voltage signal includes a high-frequency voltage signal generated based on the test light signal, and a low-frequency voltage signal generated based on the ambient light signal.

Wherein, the transimpedance amplifier 300 may adopt a single-input-single-output transimpedance amplifier, a dual-input-single-output transimpedance amplifier, and a differential transimpedance amplifier, etc., which are not limited here.

The low-pass filter module 500 is configured to absorb the high-frequency voltage signal in the voltage signal after receiving the voltage signal at both ends of the first feedback resistor 400, and transmit the low-frequency voltage signal to the first transistor 200, so that the first transistor 200 A reverse low-frequency current signal is generated to offset the low-frequency current signal corresponding to the ambient light signal.

In an optional embodiment, as shown in FIG. 3 , the first transistor 200 may be an NMOS transistor 210 . Wherein, the gate of the NMOS transistor 210 is connected to the second terminal of the low-pass filter module 500 , the drain of the NMOS transistor 210 is connected to the first terminal of the transimpedance amplifier 300 , and the source of the NMOS transistor 210 is grounded.

The transimpedance amplifier 300 is further configured to output a high-frequency electrical signal generated based on the test light signal after receiving the reverse low-frequency current signal generated by the first transistor 200 .

In the embodiment of the present application, since the photodetection circuit 10 includes: a photosensitive sensor 100 , a first transistor 200 , a transimpedance amplifier 300 , a first feedback resistor 400 and a low-pass filter module 500 . After receiving the test light signal and the environment light signal emitted by the light source, the photosensitive sensor 100 converts the test light signal and the environment light signal into a high-frequency test current signal and a low-frequency environment current signal. The transimpedance amplifier 300 receives the current signal, and transmits the high-frequency voltage signal generated based on the current signal generated based on the test light signal and the low-frequency voltage signal generated based on the ambient light signal at both ends of the first feedback resistor 400 to the low-pass filter module 500. After receiving the voltage signal across the first feedback resistor 400, the low-pass filter module 500 absorbs the high-frequency voltage signal in the voltage signal, and transmits the low-frequency voltage signal to the first transistor 200, so that the first transistor 200 generates Reverse low frequency current signal. After receiving the reverse low-frequency current signal generated by the first transistor 200, the transimpedance amplifier 300 outputs a high-frequency electrical signal generated based on the test light signal, without converting the low-frequency current signal into a digital signal through a digital circuit, and converting the ambient light into a digital signal. The generated current signal is eliminated, which reduces the loop bandwidth, reduces the complexity of the signal chain, and reduces the cost of the chip. In addition, compared with the traditional photoelectric detection circuit 10 , the present application eliminates ambient light by simulating direct feedback, and the reaction speed of eliminating ambient light is faster.

In an optional embodiment, as shown in FIG. 4 , the low-pass filter module 500 includes: an error amplifier 510 and a first capacitor 520 . Wherein, the first end of the error amplifier 510 is connected to the third end of the transimpedance amplifier 300, the second end of the error amplifier 510, the first end of the first capacitor 520 and the second end of the first transistor 200 are connected to the third common end, the third end of the error amplifier 510 is externally connected to the second bias voltage, the second end of the first capacitor 520 is grounded, the error amplifier 510, the first capacitor 520, the first transistor 200, the transimpedance amplifier 300 and the first feedback resistor 400 form a negative feedback loop.

It should be noted that the second bias voltage V2 is used to stabilize the voltage value of the third terminal of the transimpedance amplifier 300 .

Wherein, the first capacitor 520 is used to absorb the high-frequency voltage signal transmitted by the error amplifier 510 . It should be noted that the first capacitor 520 and the output impedance of the error amplifier 510 form an RC filter, which can absorb the high-frequency voltage signal transmitted by the error amplifier 510 . Wherein, the output impedance of the error amplifier 510 and the selection of the first capacitor 520 are related to the frequency of the electric signal generated by the light source to be tested.

Wherein, the error amplifier 510 is used to transmit the low frequency voltage signal to the first transistor 200 .

Optionally, the photodetection circuit 10 further includes: a second capacitor 800 connected in parallel with the first feedback resistor 400 .

In this embodiment, since the low-pass filter module 500 includes an error amplifier 510 and a first capacitor 520 . The first capacitor 520 and the output impedance of the error amplifier 510 form an RC filter, which can absorb the high-frequency voltage signal transmitted by the error amplifier 510. , the loop gain of the negative feedback loop formed by the transimpedance amplifier 300 and the first feedback resistor 400 is suppressed, so that the output remains near the input of the error amplifier 510, and then the electrical signal corresponding to the ambient light can be obtained, and the first transistor 200 produces an electrical signal in anti-phase that cancels out ambient light.

In an optional embodiment, as shown in FIG. 5 , the transimpedance amplifier 300 is a differential transimpedance amplifier 310 ; the photodetection circuit 10 further includes a second feedback resistor 700 . Wherein, the first common end is respectively connected with the first end of the differential transimpedance amplifier 310 and the first end of the first feedback resistor 400, the second end of the differential transimpedance amplifier 310 is connected with the first end of the second feedback resistor 700 and The first bias voltage is externally connected. The third end of the differential transimpedance amplifier 310, the second end of the first feedback resistor 400 and the first end of the low-pass filter module 500 are connected to the second common end, the fourth end of the differential transimpedance amplifier 310, the second feedback resistor The second end of 700 and the third end of the low-pass filter module 500 are connected to the second common end, the second end of the low-pass filter module 500 is connected to the second end of the first transistor 200, and the third end of the first transistor 200 grounded.

In this embodiment, the loop gain of the negative feedback loop formed by the error amplifier 510, the first capacitor 520, the first transistor 200, the differential transimpedance amplifier 310 and the first feedback resistor 400 is suppressed so that the output is kept at the error In the vicinity of the input of the amplifier 510, an electrical signal corresponding to the ambient light can be obtained, and the first transistor 200 can generate an antiphase electrical signal to offset the ambient light.

In another optional embodiment, as shown in FIG. 6 , the photodetection circuit 10 further includes: a second capacitor 800 connected in parallel with the first feedback resistor 400 . Optionally, the photodetection circuit 10 further includes a third capacitor 900 connected in parallel with the second feedback resistor 700 . Wherein, the second capacitor 800 can stabilize the voltage of the first feedback resistor 400 . The third capacitor 900 can stabilize the voltage of the second feedback resistor 700 .

The above-mentioned embodiment has described a photoelectric detection circuit 10 , and now uses another photoelectric detection circuit 20 in an application scenario in which the output of the transimpedance amplifier 300300 is grounded. In an optional embodiment, as shown in FIG. 7 , the photodetection circuit 20 includes: a photosensitive sensor 100 , a second transistor 1000 , a transimpedance amplifier 300 , a first feedback resistor 400 and a low-pass filter module 500 .

Wherein, the first terminal of the second transistor 1000, the first terminal of the transimpedance amplifier 300, the first terminal of the first feedback resistor 400 and the first terminal of the photosensitive sensor 100 are connected to the fourth common terminal, and the second terminal of the photosensitive sensor 100 terminal grounding; the second end of the transimpedance amplifier 300 is externally connected with the first bias voltage, the third end of the transimpedance amplifier 300, the second end of the first feedback resistor 400 and the first end of the low-pass filter module 500 are connected to the fifth Common terminal, the second terminal of the low-pass filter module 500 is connected to the second terminal of the second transistor 1000 , and the third terminal of the second transistor 1000 is connected to the power supply 600 .

The photosensitive sensor 100 is used for receiving the test light signal and the environment light signal emitted by the light source, and converting the test light signal and the environment light signal into a current signal. Current signals include: high-frequency test current signals and low-frequency environmental current signals.

Wherein, the first bias voltage V1 is used to stabilize the voltage value of the first terminal of the transimpedance amplifier 300 .

It should be noted that the light source may be a high-frequency electrical signal sent by an LED. Optionally, an electrical signal with a frequency greater than 1Khz can be used as a high-frequency current signal. Electrical signals not greater than 1Khz are regarded as low-frequency electrical signals.

During the process of photoelectric detection, since the test environment cannot be completely protected from external light, the photosensitive sensor 100 can receive the test light signal emitted by the light source and the ambient light signal.

The transimpedance amplifier 300 is used to receive the current signal, and transmit the voltage signal generated based on the current signal across the first feedback resistor 400 to the low-pass filter module 500 . Wherein, the voltage signal includes a high-frequency voltage signal generated based on the test light signal, and a low-frequency voltage signal generated based on the ambient light signal.

Wherein, the transimpedance amplifier 300 may adopt a single-input-single-output transimpedance amplifier, a dual-input-single-output transimpedance amplifier, and a differential transimpedance amplifier, etc., which are not limited here.

The low-pass filter module 500 is configured to absorb the high-frequency voltage signal in the voltage signal after receiving the voltage signal at both ends of the first feedback resistor 400, and transmit the low-frequency voltage signal to the second transistor 1000, so that the second transistor 1000 A reverse low-frequency current signal is generated to offset the low-frequency current signal corresponding to the ambient light signal.

In an optional embodiment, as shown in FIG. 8 , the first transistor 200 is a PMOS transistor 1010; the second end of the low-pass filter module 500 is connected, and the drain of the PMOS transistor 1010 is connected to the first end of the photosensitive sensor 100 connection; the source of the PMOS transistor 1010 is connected to the power supply 600 .

The transimpedance amplifier 300 is further configured to output a high-frequency electrical signal generated based on the test optical signal after receiving the reverse low-frequency current signal generated by the second transistor 1000 .

In the embodiment of the present application, since the photodetection circuit 20 includes a photosensitive sensor 100, a second transistor 1000, a transimpedance amplifier 300, a first feedback resistor 400, and a low-pass filter module 500, the photosensitive sensor 100 receives the test light signal emitted by the light source and The ambient light signal, and convert the test light signal and the ambient light signal into a high-frequency test current signal and a low-frequency ambient current signal. After receiving the current signal, the transimpedance amplifier 300 transmits the voltage signal generated based on the current signal at both ends of the first feedback resistor 400 to the low-pass filter module 500 . Wherein, the voltage signal includes a high-frequency voltage signal generated based on the test light signal, and a low-frequency voltage signal generated based on the ambient light signal. Furthermore, after receiving the voltage signal at both ends of the first feedback resistor 400, the low-pass filter module 500 absorbs the high-frequency voltage signal in the voltage signal, and transmits the low-frequency voltage signal to the second transistor 1000, so that the second transistor 1000 generates an inverse Further, after receiving the reverse low-frequency current signal generated by the second transistor 1000, the transimpedance amplifier 300 outputs a high-frequency electrical signal generated based on the test light signal, without converting the low-frequency current signal through a digital circuit. After converting to a digital signal, the current signal generated by the ambient light is eliminated, which reduces the loop bandwidth, reduces the complexity of the signal chain, and reduces the cost of the chip. In addition, compared with the traditional photoelectric detection circuit 20 , the present application eliminates ambient light by simulating direct feedback, and the reaction speed of eliminating ambient light is faster.

In an optional embodiment, as shown in FIG. 9 , the low-pass filter module 500 includes: an error amplifier 510 and a first capacitor 520; the first end of the error amplifier 510 is connected to the third end of the transimpedance amplifier 300 , the second end of the error amplifier 510 and the first end of the first capacitor 520 are respectively connected to the second end of the first transistor 200, the third end of the error amplifier 510 is externally connected to the second bias voltage; the second end of the first capacitor 520 The end is connected to the power supply 600; the error amplifier 510, the first capacitor 520, the second transistor 1000, the transimpedance amplifier 300 and the first feedback resistor 400 form a negative feedback loop.

It should be noted that the second bias voltage V2 is used to stabilize the voltage value of the third terminal of the transimpedance amplifier 300 .

Wherein, the first capacitor 520 is used to absorb the high-frequency voltage signal transmitted by the error amplifier 510 . It should be noted that the first capacitor 520 and the output impedance of the error amplifier 510 form an RC filter, which can absorb the high-frequency voltage signal transmitted by the error amplifier 510 . Wherein, the output impedance of the error amplifier 510 and the selection of the first capacitor 520 are related to the frequency of the electric signal generated by the light source to be tested.

The error amplifier 510 is used to transmit the low frequency voltage signal to the second transistor 1000 .

In this embodiment, since the low-pass filter module 500 includes an error amplifier 510 and a first capacitor 520 . The first capacitor 520 and the output impedance of the error amplifier 510 form an RC filter, which can absorb the high-frequency voltage signal transmitted by the error amplifier 510, and the low-frequency signal input to the transimpedance amplifier 300 is received by the error amplifier 510, the first capacitor 520, and the second transistor 1000 , the loop gain of the negative feedback loop formed by the transimpedance amplifier 300 and the first feedback resistor 400 is suppressed, so that the output remains near the input of the error amplifier 510, and then the electrical signal corresponding to the ambient light can be obtained, and the second transistor The 1000 produces an electrical signal that is out of phase, canceling out ambient light.

In another optional embodiment, as shown in FIG. 10 , the photodetection circuit 20 further includes a second feedback resistor 700 . The transimpedance amplifier 300 is a differential transimpedance amplifier 310; the first end of the second transistor 1000, the first end of the differential transimpedance amplifier 310, the first end of the first feedback resistor 400, the first end of the differential transimpedance amplifier 310 and The first end of the photosensitive sensor 100 is connected to the fourth common end, the second end of the differential transimpedance amplifier 310 is connected to the first end of the second feedback resistor 700 and connected to the first bias voltage, and the second end of the second feedback resistor 700 Ends are respectively connected with the third end of the differential transimpedance amplifier 310 and the first end of the low-pass filter module 500, and the fourth end of the differential transimpedance amplifier 310 is respectively connected with the second end of the first feedback circuit and the first end of the low-pass filter module 500 The third end is connected; the second end of the low-pass filter module 500 is connected to the second end of the second transistor 1000 , and the third end of the second transistor 1000 is connected to the power supply 600 .

In this embodiment, the loop gain of the negative feedback loop formed by the error amplifier 510, the first capacitor 520, the second transistor 1000, the differential transimpedance amplifier 310 and the first feedback resistor 400 is suppressed, so that the output is kept at the error In the vicinity of the input of the amplifier 510, an electrical signal corresponding to the ambient light can be obtained, and the second transistor 1000 can generate an electrical signal with an opposite phase to offset the ambient light.

In another optional embodiment, as shown in FIG. 11 , the photodetection circuit 20 further includes: a second capacitor 800 connected in parallel with the first feedback resistor 400 . Optionally, the photodetection circuit 20 further includes a third capacitor 900 connected in parallel with the second feedback resistor 700 . Wherein, the second capacitor 800 can stabilize the voltage of the first feedback resistor 400 . The third capacitor 900 can stabilize the voltage of the second feedback resistor 700 .

The technical features of the above embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be It is considered to be within the range described in this specification.

It should be noted that the photoelectric detection circuit provided in the embodiment of the present application can also be applied in the field of smoke detection test to eliminate ambient light.

The above examples only express several implementation modes of the present application, and the description thereof is relatively specific and detailed, but should not be construed as limiting the scope of the patent for the invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the scope of protection of the patent application should be based on the appended claims.

Claims (10)

1. A photoelectric detection circuit, characterized in that, comprising: a photosensitive sensor, a first transistor, a transimpedance amplifier, a first feedback resistor and a low-pass filter module; the first end of the photosensitive sensor is connected to a power supply, and the photosensitive sensor The second terminal of the sensor, the first terminal of the first transistor, the first terminal of the transimpedance amplifier and the first terminal of the first feedback resistor are connected to the first common terminal, and the second terminal of the transimpedance amplifier The first bias voltage is externally connected, the third end of the transimpedance amplifier, the second end of the first feedback resistor and the first end of the low-pass filter module are connected to the second common end, and the low-pass filter The second end of the module is connected to the second end of the first transistor; the third end of the first transistor is grounded; The photosensitive sensor is used to receive the test light signal and the ambient light signal emitted by the light source, and convert the test light signal and the ambient light signal into a current signal, and the current signal includes: a high-frequency test current signal and a low-frequency Ambient current signal; The transimpedance amplifier is configured to receive the current signal, and transmit the voltage signal generated based on the current signal at both ends of the first feedback resistor to the low-pass filter module; the voltage signal includes The high-frequency voltage signal generated by the signal, and the low-frequency voltage signal generated based on the ambient light signal; The low-pass filter module is configured to absorb the high-frequency voltage signal in the voltage signal after receiving the voltage signal at both ends of the first feedback resistor, and transmit the low-frequency voltage signal to the first transistor, so that all The first transistor generates a reverse low-frequency current signal; The transimpedance amplifier is further configured to output a high-frequency electrical signal generated based on the test optical signal after receiving the reverse low-frequency current signal generated by the first transistor. 2. The photoelectric detection circuit according to claim 1, wherein the low-pass filter module includes: an error amplifier and a first capacitor; the first end of the error amplifier and the third end of the transimpedance amplifier The second end of the error amplifier, the first end of the first capacitor and the second end of the first transistor are connected to the third common end, and the third end of the error amplifier is externally connected to the second bias Set the voltage; the second end of the first capacitor is grounded; the error amplifier, the first capacitor, the first transistor, the transimpedance amplifier and the first feedback resistor form a negative feedback loop; The first capacitor is used to absorb the high-frequency voltage signal transmitted by the error amplifier; The error amplifier is used to transmit the low-frequency voltage signal to the first transistor. 3. The photoelectric detection circuit according to claim 1, further comprising a second feedback resistor; the transimpedance amplifier is a differential transimpedance amplifier; The first common terminal is respectively connected to the first terminal of the differential transimpedance amplifier and the first terminal of the first feedback resistor, and the second terminal of the differential transimpedance amplifier is connected to the first terminal of the second feedback resistor. One end is connected and externally connected to the first bias voltage; the third end of the differential transimpedance amplifier, the second end of the first feedback resistor and the first end of the low-pass filter module are connected to the second common end, the fourth end of the differential transimpedance amplifier, the second end of the second feedback resistor and the third end of the low-pass filter module are connected to the second common end; the low-pass filter module The second end is connected to the second end of the first transistor; the third end of the first transistor is grounded. 4. The photoelectric detection circuit according to any one of claims 1-3, wherein the first transistor is an NMOS transistor; the gate of the NMOS transistor is connected to the second end of the low-pass filter module ; The drain of the NMOS transistor is connected to the first end of the transimpedance amplifier; the source of the NMOS transistor is grounded. 5. The photoelectric detection circuit according to any one of claims 1-3, further comprising: a second capacitor connected in parallel with the first feedback resistor. 6. A photoelectric detection circuit, characterized in that, comprising: a photosensitive sensor, a second transistor, a transimpedance amplifier, a first feedback resistor and a low-pass filter module; the first end of the second transistor, the transimpedance amplifier The first end of the first end, the first end of the first feedback resistor and the first end of the photosensitive sensor are connected to the fourth common end, the second end of the photosensitive sensor is grounded; the second end of the transimpedance amplifier The first bias voltage is externally connected, the third terminal of the transimpedance amplifier, the second terminal of the first feedback resistor and the first terminal of the low-pass filter module are connected to the fifth common terminal, and the low-pass filter The second end of the module is connected to the second end of the second transistor, and the third end of the second transistor is connected to a power supply; The photosensitive sensor is used to receive the test light signal and the ambient light signal emitted by the light source, and convert the test light signal and the ambient light signal into a current signal; the current signal includes: a high-frequency test current signal and a low-frequency Ambient current signal; The transimpedance amplifier is configured to receive the current signal, and transmit the voltage signal generated based on the current signal at both ends of the first feedback resistor to the low-pass filter module; the voltage signal includes A high-frequency voltage signal generated by the signal, and a low-frequency voltage signal generated based on the ambient light signal; The low-pass filter module is configured to absorb the high-frequency voltage signal in the voltage signal after receiving the voltage signal at both ends of the first feedback resistor, and transmit the low-frequency voltage signal to the second transistor, so that all The second transistor generates a reverse low-frequency current signal; The transimpedance amplifier is further configured to output a high-frequency electrical signal generated based on the test optical signal after receiving the reverse low-frequency current signal generated by the second transistor. 7. The photoelectric detection circuit according to claim 6, wherein the low-pass filtering module comprises: an error amplifier and a first capacitor; the first end of the error amplifier and the third end of the transimpedance amplifier The second end of the error amplifier and the first end of the first capacitor are respectively connected to the second end of the first transistor, and the third end of the error amplifier is externally connected to the second bias voltage; The second end of the first capacitor is connected to the power supply; the error amplifier, the first capacitor, the second transistor, the transimpedance amplifier and the first feedback resistor form a negative feedback loop; The first capacitor is used to absorb the high-frequency voltage signal transmitted by the error amplifier; The error amplifier is used to transmit the low frequency voltage signal to the second transistor. 8. The photoelectric detection circuit according to claim 6, further comprising a second feedback resistor; the transimpedance amplifier is a differential transimpedance amplifier; the first end of the second transistor, the differential transimpedance The first end of the amplifier, the first end of the first feedback resistor, the first end of the differential transimpedance amplifier and the first end of the photosensitive sensor are connected to the fourth common end; the differential transimpedance amplifier The second terminal is connected to the first terminal of the second feedback resistor and externally connected to the first bias voltage; the second terminal of the second feedback resistor is respectively connected to the third terminal of the differential transimpedance amplifier and the The first end of the low-pass filter module is connected; the fourth end of the differential transimpedance amplifier is respectively connected with the second end of the first feedback circuit and the third end of the low-pass filter module; the low-pass filter The second end of the module is connected to the second end of the second transistor; the third end of the second transistor is connected to the power supply. 9. The photoelectric detection circuit according to any one of claims 6-8, wherein the first transistor is a PMOS transistor; the second end of the low-pass filter module is connected, and the drain of the PMOS transistor It is connected with the first end of the photosensitive sensor; the source of the PMOS transistor is connected with the power supply. 10. The photoelectric detection circuit according to any one of claims 6-8, further comprising: a second capacitor connected in parallel with the first feedback resistor.

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