Adaptive ambient light compensation circuit

Abstract

The application provides an adaptive ambient light compensation circuit, aiming at the ambient light interference problem in a photoelectric measurement system, and realizes high-precision ambient light compensation through an integrated analog circuit. The circuit adopts PMOS, NMOS transistors and various amplifiers, resistors, capacitors and switch elements, and builds a system capable of self-adaptive adjustment and elimination of the influence of ambient light current. Compared with the prior art, the application utilizes adaptive current sinking and replication current technology, effectively expands the ambient light compensation range to 0-5mA, reduces the circuit area and improves the integration. In addition, by optimizing the design of the filter capacitor and resistor, the settling time is further shortened, and the trade-off problem between the filter bandwidth and the settling time is avoided. The adaptive ambient light compensation circuit of the application has a wide application prospect in the photoelectric measurement system, and can significantly improve the measurement dynamic range and accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of analog integrated circuits, and in particular, to an adaptive ambient light compensation circuit. BACKGROUND

[0002] A photodiode plus a trans-impedance amplifier is a common architecture for the front end of a photoelectric measurement system. The photodiode receives a light signal and converts it into a current signal, and the trans-impedance amplifier converts the current signal into a voltage signal. The light signal received by the photodiode usually includes a light signal to be measured and an ambient light signal that can easily cause interference and reduce the dynamic range of the measurement. Therefore, in order to ensure the accuracy of the measurement, an additional circuit is needed to eliminate the ambient light signal.

[0003] Referring to Figure 1 Fig. 1 shows a prior art photoelectric measurement front-end circuit with an ambient light elimination circuit, which includes an amplifier AMP, a feedback resistor Rf, a photodiode PD, and an Nbit IDAC. The photodiode PD is used to receive a light signal and convert it into a current signal. The amplifier AMP and the feedback resistor Rf constitute a trans-impedance amplifier that converts the current signal into a voltage signal. The IDAC represents a current-mode analog-to-digital converter, the input of which is an Nbit digital signal, and the output of which is a current signal. The current output range of the Nbit current-mode analog-to-digital converter is 0~(2 N -1)*ILSB, where ILSB is the minimum unit current that the Nbit current-mode digital-to-analog converter can output.

[0004] Referring to Figure 1 The operation of the prior art circuit shown in Fig. 1 includes two time points. At the first time point, the photodiode only receives ambient light and generates a current IAM, which enters the trans-impedance amplifier and generates a voltage Vout. Vout satisfies the following formula:

[0005] Vout = Vcm + I AM *Rf

[0006] The Nbit input code of the current-mode digital-to-analog converter can change the current entering the transimpedance amplifier until the output Vout of the transimpedance amplifier equals Vcm, at which time the current IDAC of the current-mode digital-to-analog converter equals IAM, that is, the current generated by the photodiode under the excitation of ambient light is all provided by the current-mode digital-to-analog converter and no longer enters the transimpedance amplifier. At the second time, the photodiode receives ambient light and signal light for measurement and generates a current IAM+Iin, wherein IAM is all provided by the current-mode digital-to-analog converter, and only the signal current Iin generated by the photodiode under the excitation of signal light can enter the transimpedance amplifier, so that the purpose of eliminating ambient light and accurately measuring signal light is achieved. Since the current-mode digital-to-analog converter has a limited precision, that is, a minimum output unit current ILSB, the current excited by ambient light through the photodiode cannot be completely eliminated, and the current excited by ambient light often has a large range, so that the current-mode digital-to-analog converter has a large area, which is not conducive to integration.

[0007] Therefore, there is a need to propose a new technical solution to improve the above technical problems. SUMMARY

[0008] In view of the defects in the prior art, the purpose of the present application is to provide an adaptive ambient light compensation circuit.

[0009] The adaptive ambient light compensation circuit provided by the present application comprises a first PMOS transistor MP1, a second PMOS transistor MP2, a third PMOS transistor MP3, a fourth PMOS transistor MP4, a fifth PMOS transistor MP5, a sixth PMOS transistor MP6 and a seventh PMOS transistor MP7.

[0010] The source of the first PMOS transistor MP1 is connected with the source of the second PMOS transistor MP2, a filter capacitor C, the source of the third PMOS transistor MP3 and the drain of an NMOS transistor MN1; the drain of the first PMOS transistor MP1 is connected with a resistor R1 and the source of the fourth PMOS transistor MP4; and the gate of the first PMOS transistor MP1 is connected with the resistor R2 and the resistor R1.

[0011] The source of the second PMOS transistor MP2 is connected with the filter capacitor C, the source of the third PMOS transistor MP3 and the drain of the NMOS transistor MN1; the drain of the second PMOS transistor MP2 is connected with a switch S1 and a switch S4; and the gate of the second PMOS transistor MP2 is connected with the other end of the resistor R2.

[0012] The source of the third PMOS transistor MP3 is connected with the filter capacitor C and the drain of the NMOS transistor MN1; the drain of the third PMOS transistor MP3 is connected with a switch S2 and a switch S3; and the gate of the third PMOS transistor MP3 is connected with a switch S5 and the other end of the filter capacitor C.

[0013] The source of the fourth PMOS tube MP4 is connected with the resistor R1 and the resistor R2; the drain of the fourth PMOS tube MP4 is connected with the drain of the seventh PMOS tube MP7, the current source Is1 and the current source Is2; the gate of the fourth PMOS tube MP4 is connected with the drain of the fifth PMOS tube MP5 and the other end of the current source Is1;

[0014] The source of the fifth PMOS tube MP5 is connected with the switch S2, the switch S4, the switch S6 and the negative electrode of the photodiode PD; the drain of the fifth PMOS tube MP5 is connected with the other end of the current source Is1, and the gate of the fifth PMOS tube MP5 is connected with the gate of the sixth PMOS tube MP6 and the other end of the current source Is2;

[0015] The source of the sixth PMOS tube MP6 is connected with the source of the NMOS tube MN1 and the inverting input end of the amplifier AMP2; the drain and the gate of the sixth PMOS tube MP6 are connected with the other end of the current source Is2;

[0016] The source of the seventh PMOS tube MP7 is connected with the inverting input end of the amplifier AMP1, the switch S1 and the switch S3; the drain of the seventh PMOS tube MP7 is connected with the current source Is1 and the current source Is2; the gate of the seventh PMOS tube MP7 is connected with the output end of the amplifier AMP1.

[0017] Preferably, the other end of the switch S6 is connected with a trans-impedance amplifier, the trans-impedance amplifier at least comprising the amplifier AMP3 and the feedback resistor Rf, for converting the current signal output by the photodiode PD into a voltage signal; the other end of the switch S6 is connected with the inverting input end of the amplifier AMP3 and one end of the feedback resistor Rf; the other end of the feedback resistor Rf is connected with the output end of the amplifier AMP3; the non-inverting input end of the amplifier AMP3 is connected with a preset common mode level Vcm.

[0018] Preferably, the switch S3, the switch S4 and the switch S5 are closed, the switch S1, the switch S2 and the switch S6 are opened, the photodiode PD only receives the ambient light signal, and the adaptive current adjusting circuit completely compensates the current generated by the ambient light signal.

[0019] Preferably, the switch S3, the switch S4 and the switch S5 are opened, the switch S1, the switch S2 and the switch S6 are closed, the photodiode PD simultaneously receives the ambient light and the signal light, the adaptive current adjusting circuit only compensates the current generated by the ambient light signal, and the current generated by the signal light signal enters the trans-impedance amplifier for conversion.

[0020] Preferably, the first PMOS transistor MP1, the second PMOS transistor MP2, the third PMOS transistor MP3, the fourth PMOS transistor MP4, the fifth PMOS transistor MP5, the sixth PMOS transistor MP6 and the seventh PMOS transistor MP7, the NMOS transistor, the resistor R1 and the resistor R2, the filter capacitor C, the amplifier AMP1 and the amplifier AMP2, the current source Is1 and the current source Is2, and the switch S1, the switch S2, the switch S3, the switch S4 and the switch S5 together constitute an adaptive ambient light compensation circuit main body; the amplifier AMP3, the photodiode PD, the feedback resistor Rf and the switch S6 together constitute a photoelectric measurement circuit front-end circuit main body.

[0021] Preferably, the non-inverting input terminal of the amplifier AMP1 is connected to a preset common mode level Vcm, the inverting input terminal is connected to the source of the seventh PMOS transistor, the output terminal is connected to the gate of the seventh PMOS transistor, the drain of the seventh PMOS transistor is connected to the ground, the negative feedback loop formed thereby functions as an adaptive current sink, and the source of the seventh PMOS transistor is clamped to the preset common mode level Vcm; the non-inverting input terminal of the amplifier AMP2 is connected to the preset common mode level Vcm, the inverting input terminal is connected to the source of the NMOS transistor, the output terminal is connected to the gate of the NMOS transistor, the drain of the NMOS transistor is connected to the power supply, and the negative feedback loop formed thereby clamps the source voltage VP of the NMOS transistor to the preset common mode level Vcm.

[0022] Preferably, the ratio of the current source Is1 and the current source Is2 is the same as the ratio of the W / L of the fifth PMOS transistor and the sixth PMOS transistor, so that the gate voltages of the fifth PMOS transistor and the sixth PMOS transistor are the same, and thus the source voltages of the fifth PMOS transistor and the sixth PMOS transistor are equal.

[0023] Preferably, the switch S3, the switch S4 and the switch S5 are closed, the switch S1, the switch S2 and the switch S6 are opened, the photodiode PD only receives ambient light to excite a current Iam, and the first PMOS transistor, the second PMOS transistor, the fourth PMOS transistor, the fifth PMOS transistor, the resistor R2, the switch S4 and the current source Is1 together constitute a loop, the current in the second PMOS transistor is equal to the sum of the current excited by the current source Is1 and the photodiode PD after the loop is stabilized, the W / L of the second PMOS transistor and the third PMOS transistor are the same, so that the current of the third PMOS transistor is a copy of the current of the second PMOS transistor, that is, I = Iam + Is1, and after filtering by the resistor R1 and the filter capacitor C, the current in the third PMOS transistor is a low-noise current.

[0024] Preferably, the switch S3, the switch S4 and the switch S5 are disconnected, the switch S1, the switch S2 and the switch S6 are connected, and the photodiode PD receives not only the current Iam generated by the same ambient light excitation at the first time, but also the current Iin generated by the signal light source excitation; the gate source of the third PMOS tube keeps the same voltage as the first time due to the existence of the filter capacitor, so the current in the third PMOS tube is still the current size Iam+Is1 at the first time; since the current in the photodiode is Iam+Iin, only the current Iin generated by the signal light source exciting the photodiode PD enters the transimpedance amplifier composed of the feedback resistor Rf and the amplifier AMP3, and the current Iam generated by the ambient light exciting the photodiode PD is completely offset by the adaptive ambient light compensation circuit; the adaptive ambient light compensation circuit compensates the current range of 0-5mA generated by the ambient light.

[0025] Preferably, it further comprises a resistor R1, an amplifier AMP4, a resistor R3, a capacitor C2 and an eighth PMOS tube MP8; the non-inverting input end of the amplifier AMP4 is connected to the drain or source of the eighth PMOS tube, the output end and the inverting input end are short-circuited, and one end of the resistor R3 and the capacitor C2 is connected; the other end of the resistor R3 and the capacitor C2 is connected to the gate of the eighth PMOS tube.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The adaptive ambient light compensation circuit of the present application can significantly improve the dynamic range and measurement accuracy of the photoelectric measurement system by accurately compensating the ambient light component in the measured light signal; compared with the prior art, the present application can more effectively eliminate the interference of ambient light, and make the measurement of signal light more accurate;

[0028] 2. The ambient light compensation circuit of the present application can compensate the current range of 0-5mA generated by the ambient light, which basically covers most application scenarios and provides strong support for accurate measurement under different lighting conditions;

[0029] 3. The adaptive ambient light compensation circuit of the present application effectively reduces the required circuit area by optimizing the circuit design, especially the implementation mode of the first resistor R1 (as shown in Figure 3 The design not only reduces the chip space, but also improves the integration of the circuit and reduces the production cost. BRIEF DESCRIPTION OF DRAWINGS

[0030] Other features, objects and advantages of the present application will become more apparent through reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1A photoelectric measurement front-end circuit with an ambient light elimination circuit in the prior art;

[0032] Figure 2 The adaptive ambient light compensation circuit provided by the application is provided with a circuit diagram;

[0033] Figure 3 A schematic diagram of an implementation mode of the resistor R1. DETAILED DESCRIPTION

[0034] The application will be described in detail below with specific embodiments. The following embodiments will help those skilled in the art to further understand the application, but do not limit the application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the application, a number of changes and improvements can be made. These all belong to the protection scope of the application.

[0035] Example 1:

[0036] Reference Figure 2 According to the adaptive ambient light compensation circuit provided by the application, the first PMOS tube MP1, the second PMOS tube MP2, the third PMOS tube MP3, the fourth PMOS tube MP4, the fifth PMOS tube MP5, the sixth PMOS tube MP6 and the seventh PMOS tube MP7 are included.

[0037] The source of the first PMOS tube MP1 is connected with the source of the second PMOS tube MP2, the filter capacitor C, the source of the third PMOS tube MP3 and the drain of the NMOS tube MN1; the drain of the first PMOS tube MP1 is connected with the resistor R1 and the source of the fourth PMOS tube MP4; the gate of the first PMOS tube MP1 is connected with the resistor R2 and the resistor R1;

[0038] The source of the second PMOS tube MP2 is connected with the filter capacitor C, the source of the third PMOS tube MP3 and the drain of the NMOS tube MN1; the drain of the second PMOS tube MP2 is connected with the switch S1 and the switch S4; the gate of the second PMOS tube MP2 is connected with the other end of the resistor R2;

[0039] The source of the third PMOS tube MP3 is connected with the filter capacitor C and the drain of the NMOS tube MN1; the drain of the third PMOS tube MP3 is connected with the switch S2 and the switch S3; the gate of the third PMOS tube MP3 is connected with the switch S5 and the other end of the filter capacitor C;

[0040] The source of the fourth PMOS tube MP4 is connected with the resistor R1 and the resistor R2; the drain of the fourth PMOS tube MP4 is connected with the drain of the seventh PMOS tube MP7, the current source Is1 and the current source Is2; the gate of the fourth PMOS tube MP4 is connected with the drain of the fifth PMOS tube MP5 and the other end of the current source Is1;

[0041] The source of the fifth PMOS tube MP5 is connected with the switch S2, the switch S4, the switch S6 and the negative electrode of the photoelectric diode PD; the drain of the fifth PMOS tube MP5 is connected with the other end of the current source Is1, and the gate of the fifth PMOS tube MP5 is connected with the gate of the sixth PMOS tube MP6 and the other end of the current source Is2;

[0042] The source of the sixth PMOS tube MP6 is connected with the source of the NMOS tube MN1 and the inverting input end of the amplifier AMP2; the drain and the gate of the sixth PMOS tube MP6 are connected with the other end of the current source Is2;

[0043] The source of the seventh PMOS tube MP7 is connected with the inverting input end of the amplifier AMP1, the switch S1 and the switch S3; the drain of the seventh PMOS tube MP7 is connected with the current source Is1 and the current source Is2; the gate of the seventh PMOS tube MP7 is connected with the output end of the amplifier AMP1.

[0044] The photoelectric diode PD is used for receiving the optical signal and converting into the current signal. The other end of the switch S6 is connected with the trans-impedance amplifier, the trans-impedance amplifier at least includes the amplifier AMP3 and the feedback resistor Rf, and is used for converting the current signal output by the photoelectric diode PD into the voltage signal; the other end of the switch S6 is connected with the inverting input end of the amplifier AMP3 and one end of the feedback resistor Rf; the other end of the feedback resistor Rf is connected with the output end of the amplifier AMP3; the non-inverting input end of the amplifier AMP3 is connected with the preset common-mode voltage Vcm.

[0045] The switch S3, the switch S4 and the switch S5 are closed, the switch S1, the switch S2 and the switch S6 are disconnected, the photoelectric diode PD only receives the ambient light signal, and the adaptive current adjusting circuit completely compensates the current generated by the ambient light signal. The switch S3, the switch S4 and the switch S5 are disconnected, the switch S1, the switch S2 and the switch S6 are closed, the photoelectric diode PD simultaneously receives the ambient light and the signal light, the adaptive current adjusting circuit only compensates the current generated by the ambient light signal, and the current generated by the signal light signal enters the trans-impedance amplifier for conversion.

[0046] The first PMOS transistor MP1, the second PMOS transistor MP2, the third PMOS transistor MP3, the fourth PMOS transistor MP4, the fifth PMOS transistor MP5, the sixth PMOS transistor MP6 and the seventh PMOS transistor MP7, the NMOS transistor, the resistor R1 and the resistor R2, the filter capacitor C, the amplifier AMP1 and the amplifier AMP2, the current source Is1 and the current source Is2, and the switch S1, the switch S2, the switch S3, the switch S4 and the switch S5 jointly constitute the main body of the adaptive ambient light compensation circuit; the amplifier AMP3, the photodiode PD, the feedback resistor Rf and the switch S6 jointly constitute the main body of the front-end circuit of the photoelectric measurement circuit.

[0047] The non-inverting input terminal of the amplifier AMP1 is connected with the preset common mode level Vcm, the inverting input terminal is connected with the source of the seventh PMOS transistor, the output terminal is connected with the gate of the seventh PMOS transistor, the drain of the seventh PMOS transistor is connected with the ground, the negative feedback loop formed thereby plays the role of adaptive current sink, and the source of the seventh PMOS transistor is clamped to the preset common mode level Vcm; the non-inverting input terminal of the amplifier AMP2 is connected with the preset common mode level Vcm, the inverting input terminal is connected with the source of the NMOS transistor, the output terminal is connected with the gate of the NMOS transistor, the drain of the NMOS transistor is connected with the power supply, and the negative feedback loop formed thereby clamps the source voltage VP of the NMOS transistor to the preset common mode level Vcm.

[0048] The ratio of the current source Is1 and the current source Is2 is the same as the ratio of the W / L of the fifth PMOS transistor and the sixth PMOS transistor, so the gate voltages of the fifth PMOS transistor and the sixth PMOS transistor are the same, and thus the source voltages of the fifth PMOS transistor and the sixth PMOS transistor are equal.

[0049] When the switches S3, S4 and S5 are closed, the switches S1, S2 and S6 are opened, and the photodiode PD only receives ambient light to generate a current Iam, the first, second, fourth and fifth PMOS and the resistor R2, switch S4 and current source Is1 form a loop, and the current in the second PMOS is equal to the sum of the current source Is1 and the current generated by the photodiode PD after the loop is stable; the W / L of the second and third PMOS is the same, so the current in the third PMOS is a copy of the current in the second PMOS, that is, I=Iam+Is1; and after filtering by the resistor R1 and the filter capacitor C, the current in the third PMOS is a low-noise current. When the switches S3, S4 and S5 are opened, the switches S1, S2 and S6 are closed, and the photodiode PD receives not only the ambient light to generate a current Iam, but also signal light to generate a current Iin; the gate voltage of the third PMOS remains the same as that at the first time due to the filter capacitor, so the current in the third PMOS is still the current at the first time, Iam+Is1; since the current in the photodiode is Iam+Iin, only the current Iin generated by the signal light source exciting the photodiode PD enters the transimpedance amplifier formed by the feedback resistor Rf and the amplifier AMP3, and the current Iam generated by the ambient light exciting the photodiode PD is completely offset by the adaptive ambient light compensation circuit; the adaptive ambient light compensation circuit compensates the current range of the ambient light to be 0-5mA.

[0050] The circuit further comprises a resistor R1, an amplifier AMP4, a resistor R3, a capacitor C2 and an eighth PMOS MP8; the non-inverting input terminal of the amplifier AMP4 is connected to the drain or source of the eighth PMOS, the output terminal and the inverting input terminal are short-circuited, and one end of the resistor R3 and the capacitor C2 is connected; the other end of the resistor R3 and the capacitor C2 is connected to the gate of the eighth PMOS.

[0051] Example 2:

[0052] The adaptive ambient light compensation circuit provided by the application has the advantages that Figure 2The circuit comprises: a first PMOS transistor MP1, a second PMOS transistor MP2, a third PMOS transistor MP3, a fourth PMOS transistor MP4, a fifth PMOS transistor MP5, a sixth PMOS transistor MP6, a seventh PMOS transistor MP7, an NMOS transistor MN1, a first resistor R1, a second resistor R2, a feedback resistor Rf, a first amplifier AMP1, a second amplifier AMP2, a third amplifier AMP3, a filter capacitor C, a first current source Is1, a second current source Is2, a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, and a photodiode PD.

[0053] The first PMOS transistor to the seventh PMOS transistor, the NMOS transistor, the first resistor and the second resistor, the filter capacitor, the first amplifier and the second amplifier, the first current source and the second current source, and the first switch to the fifth switch jointly constitute a main body of an adaptive ambient light compensation circuit; the third amplifier, the photodiode, the feedback resistor, and the sixth switch jointly constitute a main body of a front-end circuit of a photoelectric measurement circuit.

[0054] The non-inverting input end of the first amplifier is connected to a preset common mode level Vcm, the inverting input end is connected to the source of the seventh PMOS transistor, the output is connected to the drain of the seventh PMOS transistor, the drain of the seventh PMOS transistor is connected to the ground, a negative feedback loop is formed, the source of the seventh PMOS transistor is clamped to the preset common mode level Vcm, the non-inverting input end of the second amplifier is connected to the preset common mode level Vcm, the inverting input end is connected to the source of the NMOS transistor, the output is connected to the drain of the NMOS transistor, the drain of the NMOS transistor is connected to the power supply, a negative feedback loop is formed, and the source VP of the NMOS transistor is clamped to the preset common mode level Vcm.

[0055] The ratio of the first current source and the second current source is the same as the ratio of the W / L of the fifth PMOS transistor and the sixth PMOS transistor, so the gate-source voltage of the fifth PMOS transistor and the sixth PMOS transistor is the same, and thus the source voltages of the fifth PMOS transistor and the sixth PMOS transistor are equal.

[0056] The working principle of the adaptive ambient light compensation circuit is as follows:

[0057] At the first time, the third, fourth and fifth switches are closed, the first, second and sixth switches are opened, and the photodiode only receives ambient light to generate a current Iam. The first, second, fourth and fifth PMOS and the second resistor, fourth switch and first current source form a loop. After the loop is stable, the current in the second PMOS is equal to the sum of the current of the first current source and the current of the photodiode. The W / L of the second and third PMOS is the same, so the current of the third PMOS is a copy of the current of the second PMOS, that is, I = Iam + Is1. After filtering through the first resistor and the filtering capacitor, the current in the third PMOS is a low-noise current.

[0058] At the second time, the third, fourth and fifth switches are opened, the first, second and sixth switches are closed, and the photodiode not only receives ambient light to generate a current Iam, but also receives signal light to generate a current Iin. The gate voltage of the third PMOS remains the same as that at the first time due to the presence of the filtering capacitor, so the current in the third PMOS is still the current at the first time, Iam + Is1. Since the current in the photodiode is Iam + Iin, only the current Iin generated by the signal light source exciting the photodiode enters the transimpedance amplifier formed by the feedback resistor and the third amplifier, and the current Iam generated by the ambient light exciting the photodiode is completely offset by the adaptive ambient light compensation circuit. The ambient light compensation circuit can compensate for the current range of 0-5mA generated by the ambient light. Basically, it covers most application scenarios.

[0059] To save area, the first resistor R1 can also be used Figure 3 The implementation mode of the fourth amplifier AMP4, the third resistor R3, the second capacitor C2 and the eighth PMOS MP8. The non-inverting input terminal of the fourth amplifier is connected to the drain or source of the eighth PMOS, the output terminal is short-circuited with the inverting input terminal, and is connected to one end of the third resistor and the second capacitor. The other end of the third resistor and the second capacitor is connected to the gate of the eighth PMOS.

[0060] At the first time, the eighth PMOS gradually changes from the linear region of strong reverse type to weak reverse type, and the impedance gradually changes from low to high, without trade-off between the establishment time and the filtering bandwidth, so that the time at the first time can be reduced, and a large area is not required.

[0061] The analog ambient light compensation mode is adopted, the ambient light compensation range is adaptively adjusted, the compensation range is large, the area is small, and integration is facilitated.

[0062] TIA: transimpedance amplifier

[0063] PD: photodiode

[0064] IDAC: current digital-to-analog converter

[0065] PMOS: P-type transistor

[0066] NMOS: N-type transistor

[0067] trade-off: trade-off

[0068] Those skilled in the art can understand the present embodiment as a more specific description of embodiment 1.

[0069] Those skilled in the art know that, in addition to implementing the system provided by the present application and each device, module, unit thereof in the form of pure computer readable program code, the same function can also be achieved by logically programming the method steps to make the system provided by the present application and each device, module, unit thereof in the form of logic gate, switch, application specific integrated circuit, programmable logic controller and embedded microcontroller. Therefore, the system provided by the present application and each device, module, unit thereof can be considered as a hardware component, and the devices, modules, units included therein for achieving various functions can also be considered as structures within the hardware component; the devices, modules, units for achieving various functions can also be considered as both software modules for implementing the method and structures within the hardware component.

[0070] The specific embodiments of the present application are described above. It needs to be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other without conflict.

Claims

1. An adaptive ambient light compensation circuit, characterized in that: The application relates to a PMOS circuit, which comprises: a first PMOS transistor MP1, a second PMOS transistor MP2, a third PMOS transistor MP3, a fourth PMOS transistor MP4, a fifth PMOS transistor MP5, a sixth PMOS transistor MP6 and a seventh PMOS transistor MP7; a source electrode of the first PMOS transistor MP1 is connected with a source electrode of the second PMOS transistor MP2, a filter capacitor C, a source electrode of the third PMOS transistor MP3 and a drain electrode of an NMOS transistor MN1; a drain electrode of the first PMOS transistor MP1 is connected with a resistor R1 and a source electrode of the fourth PMOS transistor MP4; a gate electrode of the first PMOS transistor MP1 is connected with a resistor R2 and the resistor R1; a source electrode of the second PMOS transistor MP2 is connected with the filter capacitor C, the source electrode of the third PMOS transistor MP3 and the drain electrode of the NMOS transistor MN1; a drain electrode of the second PMOS transistor MP2 is connected with a switch S1 and a switch S4; a gate electrode of the second PMOS transistor MP2 is connected with the other end of the resistor R2; a source electrode of the third PMOS transistor MP3 is connected with the filter capacitor C and the drain electrode of the NMOS transistor MN1; a drain electrode of the third PMOS transistor MP3 is connected with the switch S2 and the switch S3; a gate electrode of the third PMOS transistor MP3 is connected with the switch S5 and the other end of the filter capacitor C; a source electrode of the fourth PMOS transistor MP4 is connected with the resistor R1 and the resistor R2; a drain electrode of the fourth PMOS transistor MP4 is connected with a drain electrode of the seventh PMOS transistor MP7, a current source Is1 and a current source Is2; a gate electrode of the fourth PMOS transistor MP4 is connected with a drain electrode of the fifth PMOS transistor MP5 and the other end of the current source Is1; a source electrode of the fifth PMOS transistor MP5 is connected with the switch S2, the switch S4, the switch S6 and a negative electrode of a photodiode PD; a drain electrode of the fifth PMOS transistor MP5 is connected with the other end of the current source Is1, and a gate electrode of the fifth PMOS transistor MP5 is connected with a gate electrode of the sixth PMOS transistor MP6 and the other end of the current source Is2; a source electrode of the sixth PMOS transistor MP6 is connected with a source electrode of the NMOS transistor MN1 and an inverting input end of an amplifier AMP2; a drain electrode and a gate electrode of the sixth PMOS transistor MP6 are connected with the other end of the current source Is2; a source electrode of the seventh PMOS transistor MP7 is connected with an inverting input end of an amplifier AMP1, the switch S1 and the switch S3; a drain electrode of the seventh PMOS transistor MP7 is connected with the current source Is1 and the current source Is2; a gate electrode of the seventh PMOS transistor MP7 is connected with an output end of the amplifier AMP1.

2. The adaptive ambient light compensation circuit of claim 1, wherein, the other end of the switch S6 is connected with a transimpedance amplifier, the transimpedance amplifier at least comprises an amplifier AMP3 and a feedback resistor Rf, and is used for converting a current signal output by the photodiode PD into a voltage signal; the other end of the switch S6 is connected with an inverting input end of the amplifier AMP3 and one end of the feedback resistor Rf; the other end of the feedback resistor Rf is connected with an output end of the amplifier AMP3; a non-inverting input end of the amplifier AMP3 is connected with a preset common-mode voltage Vcm.

3. The adaptive ambient light compensation circuit of claim 1, wherein, The switch S3, the switch S4 and the switch S5 are closed, the switch S1, the switch S2 and the switch S6 are disconnected, the photodiode PD only receives ambient light signals, and the adaptive current adjusting circuit completely compensates the current generated by the ambient light signals.

4. The adaptive ambient light compensation circuit of claim 1, wherein, The switch S3, the switch S4 and the switch S5 are disconnected, the switch S1, the switch S2 and the switch S6 are closed, the photodiode PD simultaneously receives ambient light and signal light, the adaptive current adjusting circuit only compensates the current generated by the ambient light signals, and the current generated by the signal light signals enters the transimpedance amplifier for conversion.

5. The adaptive ambient light compensation circuit according to claim 1, wherein: The first PMOS tube MP1, the second PMOS tube MP2, the third PMOS tube MP3, the fourth PMOS tube MP4, the fifth PMOS tube MP5, the sixth PMOS tube MP6 and the seventh PMOS tube MP7, the NMOS tube, the resistor R1 and the resistor R2, the filter capacitor C, the amplifier AMP1 and the amplifier AMP2, the current source Is1 and the current source Is2 and the switch S1, the switch S2, the switch S3, the switch S4 and the switch S5 jointly constitute the adaptive ambient light compensation circuit main body; the amplifier AMP3, the photodiode PD, the feedback resistor Rf and the switch S6 jointly constitute the photometric measurement circuit front-end circuit main body.

6. The adaptive ambient light compensation circuit of claim 1, wherein, The non-inverting input end of the amplifier AMP1 is connected with a preset common mode level Vcm, the inverting input end is connected with the source electrode of the seventh PMOS tube, the output end is connected with the gate electrode of the seventh PMOS tube, the drain electrode of the seventh PMOS tube is connected with the ground, the negative feedback loop formed thereby plays the role of adaptive current sinking, and the source electrode of the seventh PMOS tube is clamped to the preset common mode level Vcm; the non-inverting input end of the amplifier AMP2 is connected with the preset common mode level Vcm, the inverting input end is connected with the source electrode of the NMOS tube, the output end is connected with the gate electrode of the NMOS tube, the drain electrode of the NMOS tube is connected with the power supply, and the negative feedback loop formed thereby clamps the source electrode VP of the NMOS tube to the preset common mode level Vcm.

7. The adaptive ambient light compensation circuit of claim 1, wherein, The ratio of the current source Is1 and the current source Is2 is the same as the ratio of the W / L of the fifth PMOS tube and the sixth PMOS tube, so the gate voltages of the fifth PMOS tube and the sixth PMOS tube are the same, and thus the source voltages of the fifth PMOS tube and the sixth PMOS tube are equal.

8. The adaptive ambient light compensation circuit of claim 1, wherein, The switch S3, the switch S4 and the switch S5 are closed, the switch S1, the switch S2 and the switch S6 are disconnected, and the photodiode PD only receives ambient light and then excites to generate a current Iam, the first PMOS, the second PMOS, the fourth PMOS and the fifth PMOS and the resistor R2, the switch S4 and the current source Is1 jointly constitute a loop, the current in the second PMOS tube is equal to the sum of the current excited by the current source Is1 and the photodiode PD after the loop is stabilized; the W / L of the second PMOS tube and the third PMOS tube is the same, so the current of the third PMOS tube is a copy of the current of the second PMOS tube, that is, I=Iam+Is1 is satisfied; and after filtering by the resistor R1 and the filter capacitor C, the current in the third PMOS tube is a low-noise current.

9. The adaptive ambient light compensation circuit of claim 1, wherein, The switch S3, switch S4 and switch S5 are disconnected, the switch S1, switch S2 and switch S6 are closed, and the photoelectric diode PD receives not only the current Iam generated by the same ambient light excitation at the first time, but also the current Iin generated by the signal light source excitation; the gate source of the third PMOS tube remains the same voltage as the first time due to the existence of the filter capacitor, so the current in the third PMOS tube is still the current size Iam+Is1 at the first time; since the current in the photoelectric diode is Iam+Iin, only the current Iin generated by the signal light source excitation photoelectric diode PD difference enters the transimpedance amplifier composed of the feedback resistor Rf and the amplifier AMP3, and the current Iam generated by the ambient light excitation photoelectric diode PD is completely offset by the adaptive ambient light compensation circuit; the ambient light compensation circuit compensates the current range of 0-5mA generated by the ambient light.

10. The adaptive ambient light compensation circuit of claim 1, wherein, It also includes a resistor R1, an amplifier AMP4, a resistor R3, a capacitor C2 and an eighth PMOS tube MP8; the non-inverting input end of the amplifier AMP4 is connected to the drain or source of the eighth PMOS tube, the output end and the inverting input end are short-circuited, and one end of the resistor R3 and the capacitor C2 is connected; the other end of the resistor R3 and the capacitor C2 is connected to the gate of the eighth PMOS tube.

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