Sensor with photodiode biasing circuit
By incorporating a current source and bias circuit into the photodiode sensor, the problem of parasitic capacitance affecting the photodiode sensor after the light signal stops shining is solved, enabling normal operation of the sensor and detection at a greater distance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ANPEC ELECTRONICS CORPORATION
- Filing Date
- 2021-07-20
- Publication Date
- 2026-06-30
Smart Images
Figure CN122316319A_ABST
Abstract
Description
[0001] This application is a divisional application of application filed on July 20, 2021, with application number 202110821860.1 and entitled "Sensor with Photodiode Bias Circuit", the entire contents of which are incorporated herein by reference. Technical Field
[0002] This application relates to sensors, and more particularly to a sensor with a photodiode bias circuit. Background Technology
[0003] Touchscreen phones are becoming increasingly popular, but because they use touchscreens, users' faces can easily touch the screen during calls, leading to accidental operations. Therefore, optical proximity sensors are typically installed in phones. When the optical proximity sensor detects that light is blocked, the phone's system determines that the user's face is close to the touchscreen and shuts it down to prevent accidental operations caused by face proximity, and also to save battery power during calls.
[0004] First, the transmitter emits a light signal towards the user. This light signal is reflected back to the photodiode, which converts the reflected light energy into a photocurrent. However, due to the parasitic capacitance of the photodiode, the photocurrent first charges this parasitic capacitance, which takes some time. After the light signal reflected back to the photodiode stops illuminating the device, the excessively high voltage after the parasitic capacitance is charged will affect the voltage at the photodiode's cathode. This prevents the cathode voltage from maintaining the desired value, thus hindering the successful sensing of the photocurrent value from a photodiode without illumination. Summary of the Invention
[0005] The technical problem this application aims to solve is to provide a sensor with a photodiode bias circuit, addressing the shortcomings of existing technologies. The sensor includes a photodiode, a first operational amplifier, a first current source, a first transistor, a second transistor, a first current mirror circuit, and a pre-charge capacitor. The anode of the photodiode is grounded. The photodiode is configured to convert light energy passing through it into a photocurrent. A first input terminal of the first operational amplifier is coupled to a reference voltage. A second input terminal of the first operational amplifier is connected to the cathode of the photodiode. A first terminal of the first current source is connected to the cathode of the photodiode. A second terminal of the first current source is grounded. A control terminal of the first transistor is connected to the output terminal of the first operational amplifier. A first terminal of the first transistor is connected to the cathode of the photodiode. A control terminal of the second transistor is connected to the output terminal of the first operational amplifier. The first current mirror circuit includes a third transistor, a fourth transistor, and a fifth transistor. The first terminals of the third, fourth, and fifth transistors are coupled to a shared voltage. The second terminal of the third transistor is connected to the second terminal of the first transistor and the control terminal of the third transistor. The control terminal of the fourth transistor is connected to the control terminal of the third transistor, the second terminal of the fourth transistor, and the control terminal of the fifth transistor. The second terminal of the fifth transistor is connected to the first terminal of the second transistor. The first terminal of the pre-charge capacitor is coupled to the shared voltage. The second terminal of the pre-charge capacitor is connected to the control terminal of the third transistor. The first current source supplies current to charge the pre-charge capacitor to the target voltage value. Then, light shines through the photodiode, and the pre-charge capacitor stores the current information from the previous stage at the control terminal of the third transistor and discharges. The discharge current flows to ground through the first current source. The current value of the second transistor is the output value of the sensor with the photodiode bias circuit.
[0006] In one embodiment, the sensor with photodiode bias circuit further includes a second current source. A first terminal of the second current source is connected to a second terminal of the second transistor. The second terminal of the second current source is grounded.
[0007] In one embodiment, the sensor with photodiode bias circuit further includes a first switching assembly. A first terminal of the first switching assembly is connected to the control terminal of a third transistor. A second terminal of the first switching assembly is connected to both the second terminal of the first transistor and the control terminal of a fourth transistor.
[0008] In one embodiment, the sensor with photodiode bias circuit further includes a second switching assembly. A first terminal of the second switching assembly is connected to a second terminal of the first transistor and a second terminal of the first switching assembly. A second terminal of the second switching assembly is connected to a second terminal of a fourth transistor.
[0009] In one embodiment, the sensor with photodiode bias circuit further includes a first capacitor. A first terminal of the first capacitor is connected to the output terminal of a first operational amplifier. A second terminal of the first capacitor is connected to the cathode of the photodiode.
[0010] As described above, this application provides a sensor with a photodiode bias circuit. A current source is connected to the cathode of the photodiode to provide a path for the parasitic capacitance of the photodiode to discharge. This prevents the high voltage of the parasitic capacitance from affecting the cathode voltage of the photodiode after the photodiode stops receiving light, thus preventing the photodiode from malfunctioning. Notably, the sensor in this application further incorporates a photodiode bias circuit, ensuring that the current sensed by the sensor does not contain the current provided by the bias current source, but only the current sensed by the photodiode.
[0011] To further understand the features and technical content of this application, please refer to the following detailed description and drawings. However, the drawings provided are for reference and illustration only and are not intended to limit this application. Attached Figure Description
[0012] Figure 1 This is a circuit layout diagram of a sensor with a photodiode bias circuit according to the first embodiment of this application.
[0013] Figure 2 The waveform diagram is of the sensor with photodiode bias circuit according to the first embodiment of this application.
[0014] Figure 3 The waveform diagram is of the sensor with photodiode bias circuit according to the first embodiment of this application.
[0015] Figure 4 The waveform diagram is of the sensor with photodiode bias circuit according to the first embodiment of this application.
[0016] Figure 5 The waveform diagram is of the sensor with photodiode bias circuit according to the first embodiment of this application.
[0017] Figure 6 This is a circuit layout diagram of a sensor with a photodiode bias circuit according to the second embodiment of this application.
[0018] Figure 7 This is a schematic diagram showing the flow of the charging current of the pre-charge capacitor of the sensor with photodiode bias circuit according to the second embodiment of this application.
[0019] Figure 8 This is a schematic diagram showing the current flow of a sensor with a photodiode bias circuit according to the second embodiment of this application.
[0020] Figure 9 The waveform diagram is of the sensor with photodiode bias circuit according to the second embodiment of this application.
[0021] Figure 10The waveform diagram is of the sensor with photodiode bias circuit according to the second embodiment of this application.
[0022] Figure 11 The waveform diagram is of the sensor with photodiode bias circuit according to the second embodiment of this application.
[0023] Figure 12 The waveform diagram is of the sensor with photodiode bias circuit according to the second embodiment of this application.
[0024] Figure 13 The graphs are for conventional sensors and sensors with photodiode bias circuits according to embodiments of this application. Detailed Implementation
[0025] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can understand the advantages and effects of this application from the content disclosed in this specification. This application can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this application. Furthermore, the accompanying drawings of this application are for simple illustration only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this application in detail, but the disclosed content is not intended to limit the scope of protection of this application. Additionally, the term "or" used herein may, depending on the actual situation, include any combination of one or more of the associated listed items.
[0026] [First Embodiment]
[0027] Please see Figure 1 This is a circuit layout diagram of a sensor with a photodiode bias circuit according to the first embodiment of this application.
[0028] like Figure 1 As shown, the sensor in this embodiment may include a photodiode PE and a first operational amplifier OPA1. The first input terminal of the first operational amplifier OPA1 is coupled to a reference voltage Vref. The second input terminal of the first operational amplifier OPA1 is connected to the cathode of the photodiode PE. The anode of the photodiode PE is grounded.
[0029] When a transmitter (not shown) emits a light signal towards an object, such as a person, and the signal is reflected back to the photodiode PE, the photodiode PE converts the light energy of the light signal that has passed through it into a photocurrent. However, the parasitic capacitance Cp of the photodiode PE may be charged too high by the photocurrent, causing the photodiode PE to malfunction.
[0030] Therefore, the sensor in this embodiment also includes a first current source CS1. The first terminal of the first current source CS1 is connected to the cathode of the photodiode PE. The second terminal of the first current source CS1 is grounded. The first current source CS1 is configured to assist the parasitic capacitance of the photodiode PE in discharging to ground through the first current source CS1 when the light signal stops illuminating the photodiode PE, thereby reducing the voltage of the parasitic capacitance.
[0031] After adding the first current source CS1, the photocurrent output by the sensor contains not only the photocurrent Is1 induced by the photodiode PE, but also an additional current Id (i.e., the discharge current of the parasitic capacitance Cp and the current supplied by the first current source CS1). However, the current sensed by the sensor should only be the photocurrent Is1 induced by the photodiode PE.
[0032] Therefore, the sensor in this embodiment further includes a first transistor T1, a first current mirror circuit MR1, a second transistor T2, a second operational amplifier OPA2, a second current source CS2, and a third transistor T3.
[0033] The control terminal of the first transistor T1 is connected to the output terminal of the first operational amplifier OPA1. The first terminal of the first transistor T1 is connected to the cathode of the photodiode PE. The second terminal of the first transistor T1 is connected to the input terminal of the first current mirror circuit MR1.
[0034] The output terminal of the first current mirror circuit MR1 is connected to the first terminal of the second transistor T2. The control terminal of the second transistor T2 is connected to the output terminal of the first operational amplifier OPA1. The second terminal of the second transistor T2 is connected to the first terminal of the second current source CS2. The second terminal of the second current source CS2 is grounded.
[0035] In detail, the first current mirror circuit MR1 may include a sixth transistor T6 and a seventh transistor T7. The first terminals of the sixth transistor T6 and the seventh transistor T7 may be coupled to a shared voltage. The second terminal of the sixth transistor T6 is connected to the second terminal of the first transistor T1. The second terminal of the seventh transistor T7 is connected to the first terminal of the second transistor T2. The control terminal of the seventh transistor T7 is connected to the control terminal of the sixth transistor T6.
[0036] If necessary, the first current mirror circuit MR1 may also include an eighth transistor T8, a ninth transistor T9, or both.
[0037] The control terminal of the eighth transistor T8 can be connected to the second terminal of the first transistor T1. The first terminal of the eighth transistor T8 can be connected to the control terminal of the sixth transistor T6 and the second terminal of the ninth transistor T9. The second terminal of the eighth transistor T8 can be grounded.
[0038] The first terminal of the ninth transistor T9 can be coupled to a shared voltage. The second terminal of the ninth transistor T9 can be connected to the control terminals of the sixth transistor T6, the seventh transistor T7, and the first terminal of the eighth transistor T8. The control terminal of the ninth transistor T9 can be coupled to a first control voltage VB1.
[0039] It is worth noting that the first input terminal of the second operational amplifier OPA2, for example, the inverting input terminal, is connected to the node between the first terminal of the first transistor T1 and the cathode of the photodiode PE (hereinafter referred to as the first node). The second input terminal of the second operational amplifier OPA2, for example, the non-inverting input terminal, is connected to the node between the second terminal of the second transistor T2 and the first terminal of the second current source CS2 (hereinafter referred to as the second node).
[0040] The control terminal of the third transistor T3 is connected to the output terminal of the second operational amplifier OPA2. The first terminal of the third transistor T3 is connected to the second node mentioned above. The second terminal of the third transistor T3 is grounded.
[0041] It should be understood that the voltage at the first input terminal of the second operational amplifier OPA2 will be equal to the voltage at the second input terminal of the second operational amplifier OPA2. Furthermore, in this embodiment, the second transistor T2 has the same dimensions and characteristics as the first transistor T1. In this case, the voltage at the first node remains equal to the voltage at the second node. Thus, the current Id at the second terminal of the second transistor T2 (i.e., the current of the second current source CS2) is equal to the current Id of the first current source CS1, making the current Is1 flowing to the first terminal of the third transistor T3 equal to the photocurrent induced by the photodiode PE of the sensor in this embodiment.
[0042] The ratio of the input current to the output current of the first current mirror circuit MR1 can be 1:N, where N is any suitable integer value. In this embodiment, the ratio of the input current to the output current of the first current mirror circuit MR1 is 1:1, so the current Is1 flowing to the first terminal of the third transistor T3 is equal to the photocurrent of the photodiode PE, but this application is not limited thereto.
[0043] If necessary, the sensor in this embodiment may further include a first capacitor C1, a second capacitor C2, or both. The first terminal of the first capacitor C1 can be connected to the output terminal of the first operational amplifier OPA1. The second terminal of the first capacitor C1 can be connected to the cathode of the photodiode PE. The first terminal of the second capacitor C2 can be connected to the output terminal of the second operational amplifier OPA2. The second terminal of the second capacitor C2 can be grounded.
[0044] Additionally, the sensor in this embodiment may also include a fourth transistor T4. The control terminal of the fourth transistor T4 is connected to the output terminal of the second operational amplifier OPA2, and the first terminal of the fourth transistor T4 can be coupled to a shared voltage. The second terminal of the fourth transistor T4 is grounded.
[0045] Furthermore, the sensor in this embodiment may also include a fifth transistor T5. The control terminal of the fifth transistor T5 is connected to the output terminal of the first operational amplifier OPA1. The first terminal of the fifth transistor T5 is connected to the first terminal of the fourth transistor T4. The second terminal of the fifth transistor T5 is coupled to a shared voltage.
[0046] Furthermore, if necessary, the sensor in this embodiment may also include a second current mirror circuit MR2 and a third current source CS3. The input terminal of the second current mirror circuit MR2 is connected to the second terminal of the fifth transistor T5. The current Is1 output by the third current source CS3 (i.e., the output current of the output terminal of the second current mirror circuit MR2) is the current output by the output terminal of the sensor in this embodiment.
[0047] Specifically, the second current mirror circuit MR2 may include a tenth transistor T10 and an eleventh transistor T11. The first terminals of the tenth transistor T10 and the eleventh transistor T11 may be coupled to a shared voltage. The second terminal of the tenth transistor T10 is connected to the second terminal of the fifth transistor T5. The control terminal of the eleventh transistor T11 is connected to the control terminal of the tenth transistor T10. The second terminal of the eleventh transistor T11 serves as the output terminal of the sensor in this embodiment.
[0048] If necessary, the second current mirror circuit MR2 may also include a twelfth transistor T12, a thirteenth transistor T13, or both. The control terminal of the twelfth transistor T12 may be connected to the second terminal of the fifth transistor T5. The first terminal of the twelfth transistor T12 may be connected to the control terminals of the tenth transistor T10 and the eleventh transistor T11. The second terminal of the twelfth transistor T12 is grounded.
[0049] The first terminal of the thirteenth transistor T13 can be coupled to a shared voltage. The second terminal of the thirteenth transistor T13 can be connected to the control terminals of the tenth transistor T10 and the eleventh transistor T11. The control terminal of the thirteenth transistor T13 can be coupled to a second control voltage VB2. The second terminal of the eleventh transistor T11 can be connected to a third current source CS3.
[0050] The ratio of the input current to the output current of the second current mirror circuit MR2 can be 1:N, where N is any suitable integer value, so that the output current of the second current mirror circuit MR2 is amplified to N times the input current of the second current mirror circuit MR2. In this embodiment, the ratio of the input current to the output current of the second current mirror circuit MR2 is 1:1, so the output current Is1 of the sensor in this embodiment is equal to the current Is1 flowing to the first terminal of the third transistor T3, but this application is not limited thereto.
[0051] Please refer to the following: Figures 1 to 5 ,in Figures 2 to 5The waveform diagram is of the sensor with photodiode bias circuit according to the first embodiment of this application.
[0052] like Figures 2 to 5 The rising edge of the light emission time signal TES1 shown is the time when the transmitter begins to emit a light signal toward the object. During the period when the light emission time signal TES1 is at a high level, the transmitter continuously emits a light signal toward the object. For example... Figure 1 The photodiode PE shown converts the light signal reflected back from the object into a photocurrent, and finally the sensor outputs as shown in the figure. Figures 1 to 5 The current Is1 shown is shown.
[0053] like Figures 2 to 5 The point in time when the analog-to-digital processing signal ADS1 transitions from a low level to a high level represents the start-up of the processing circuit connected to the sensor's output (e.g., but not limited to, an analog-to-digital converter). Figure 1 The current signal Is1 output by the sensor shown is processed, for example, converted from analog to digital format. Figures 2 to 5 The operation signal SNS1 shown is the high-level time, representing the time from the start of the transmitter emitting the optical signal to the completion of the signal processing of the current Is1.
[0054] For example, such as Figure 1 The output terminal of the sensor shown (i.e., the second terminal of the eleventh transistor T11) can be connected to a charging capacitor (not shown). Current Is1 charges the charging capacitor, causing it to... Figure 3 and Figure 5 The capacitor voltage signal CVS1 shown indicates a gradual increase in the voltage signal of the charging capacitor. When the voltage of the charging capacitor reaches... Figure 3 and Figure 5 When the reference voltage signal VRS1 is shown, the voltage signal of the charging capacitor is pulled down to a valley value by the processing circuit, so that it can be charged from the valley value to the voltage value of the reference voltage signal VRS1 during the next charging.
[0055] The counter in the processing circuit counts the number of times the charging capacitor is charged and discharged, that is, it counts the number of waveforms of the capacitor voltage signal CVS1, and uses this count to determine the object and the method used. Figure 1 The distance between the electronic devices (e.g., mobile phones) of the sensors shown.
[0056] [Second Embodiment]
[0057] Please see Figures 6 to 8 ,in Figure 6 This is a circuit layout diagram of a sensor with a photodiode bias circuit according to the second embodiment of this application.
[0058] The sensor in this embodiment may include, for example: Figure 6The diagram shows a photodiode PE, a first operational amplifier OPA1, a first current source CS1, a first transistor T1, a second transistor T2, a second current source CS2, and a first current mirror circuit MR11. The same components as in the first embodiment will not be repeated here.
[0059] It is worth noting that the sensor in this embodiment also includes a pre-charge capacitor Cr, which is connected to the first current mirror circuit MR11.
[0060] In detail, the first current mirror circuit MR11 may include a third transistor TR3, a fourth transistor TR4, and a fifth transistor TR5. The first terminals of the third transistor TR3, the fourth transistor TR4, and the fifth transistor TR5 may be coupled to a shared voltage.
[0061] The second terminal of the third transistor TR3 is connected to the second terminal of the first transistor T1 and the control terminal of the third transistor TR3. The control terminal of the third transistor TR3 is connected to the second terminal of the pre-charge capacitor. The first terminal of the pre-charge capacitor Cr can be coupled to a shared voltage. The control terminal of the fourth transistor TR4 can be connected to the control terminal of the third transistor TR3, the second terminal of the fourth transistor TR4, and the control terminal of the fifth transistor TR5. The second terminal of the fifth transistor TR5 is connected to the first terminal of the second transistor T2.
[0062] In addition, the sensor in this embodiment may also include, for example: Figure 6 The first switch assembly SW1 and the second switch assembly SW2 are shown.
[0063] The first terminal of the first switching assembly SW1 can be connected to the control terminal of the third transistor TR3. The second terminal of the first switching assembly SW1 can be connected to the second terminal of the first transistor T1 and the control terminal of the fourth transistor TR4. The first terminal of the second switching assembly SW2 can be connected to the second terminal of the first transistor T1 and the second terminal of the first switching assembly SW1. The second terminal of the second switching assembly SW2 can be connected to the second terminal of the fourth transistor TR4.
[0064] like Figure 7 As shown, before the transmitter emits a light signal toward the object, when no reflected light shines through the photodiode PE, the first switch assembly SW1 is turned on but the second switch assembly SW2 is turned off, and the first current source CS1 supplies current Ih2 to the pre-charge capacitor Cr to charge the voltage of the pre-charge capacitor Cr.
[0065] After the transmitter emits a light signal toward the object for a period of time, the light signal reflected back to the photodiode PE by the object illuminates the photodiode PE. At this time, as shown... Figure 8As shown, the first switching component SW1 is closed while the second switching component SW2 is open. The pre-charge capacitor Cr stores the current information of the previous stage current Ih2 on the control terminal of the third transistor TR3. The third transistor TR3 discharges and the discharge current Ih1=Ih2 flows to the ground terminal through the first current source CS1. At the same time, the photodiode PE senses the photocurrent Is2, which can be provided by the fourth transistor TR4 to generate the current of the first current mirror circuit MR11. This causes the fifth transistor TR5 to output the photocurrent Is2 sensed by the photodiode PE, and the photocurrent Is2 does not include the current of the first current source CS1.
[0066] When the ratio of the input current to the output current of the first current mirror circuit MR11 is 1:N, such as Figure 8 The output current Is2 of the light sensor shown is N times the photocurrent Is2 of the photodiode PE. In this embodiment, N=1, therefore... Figure 8 The output current Is2 of the optical sensor shown is equal to the photocurrent Is2, but this application is not limited thereto.
[0067] Please see Figures 8 to 12 ,in Figures 9 to 12 The waveform diagram is of the sensor with photodiode bias circuit according to the second embodiment of this application.
[0068] like Figures 8 to 12 The rising edge of the light emission time signal TES2 shown is the time when the transmitter begins to emit a light signal toward the object. During the period when the light emission time signal TES2 is at a high level, the transmitter continuously emits a light signal toward the object, such as... Figure 8 The photodiode PE shown converts the light signal reflected back from the object into a photocurrent, and finally the sensor outputs as shown in the figure. Figures 8 to 12 The current Is2 is shown.
[0069] like Figures 9 to 12 The point in time when the analog-to-digital processed signal ADS2 transitions from a low level to a high level represents the start-up of the processing circuit connected to the sensor's output (e.g., but not limited to, an analog-to-digital converter). Figure 8 The output current Is2 of the sensor shown is processed, for example, converted from analog to digital format.
[0070] For example, such as Figure 8 The output terminal of the sensor shown (i.e., the second terminal of the second transistor T2) can be connected to a charging capacitor (not shown). Current Is2 charges the charging capacitor, causing... Figure 10 and Figure 12 The capacitor voltage signal CVS2 shown illustrates the gradual increase in the voltage signal of the charging capacitor. When the voltage of the charging capacitor reaches... Figure 10 and Figure 12 When the reference voltage signal VRS2 is shown, the voltage signal of the charging capacitor is pulled down to a valley value by the processing circuit, so that it can be charged from the valley value to the voltage value of the reference voltage signal VRS2 during the next charging.
[0071] The counter in the processing circuit counts the number of times the charging capacitor charges and discharges, i.e., the number of waveforms of the capacitor voltage signal CVS2, and uses this to estimate the relationship between the object and the capacitor. Figure 8 The distance between the electronic devices (e.g., mobile phones) of the sensors shown.
[0072] Please see Figure 13 The graphs are of a conventional sensor and a sensor with a photodiode bias circuit according to embodiments of this application.
[0073] like Figure 13 As shown, the horizontal axis of the graph represents the distance between the object and the sensor, and the vertical axis represents the count value detected by the sensor. This count value refers to the number of times the charging capacitor has been charged and discharged, as counted by the sensor's counter (e.g., ...). Figure 12 The waveform count of the capacitor voltage signal CVS2 shown is a number of waveforms. This count value is the sensing data of the distance between the object and the electronic device of the sensor (such as a mobile phone).
[0074] It should be understood that the characteristic of a sensor is that it is better to detect distances as far as possible. For example... Figure 13 As shown, traditional sensors can only detect very short distances, up to 5cm. Traditional sensors cannot count to the correct value when the distance between the object and the electronic device exceeds 5cm, thus failing to calculate the accurate distance. In contrast, the sensor of this application can detect distances up to 11cm. Clearly, the sensor of this application has superior characteristics compared to traditional sensors.
[0075] In summary, this application provides a sensor with a photodiode bias circuit. A current source is connected to the cathode of the photodiode to provide a path for the parasitic capacitance of the photodiode to discharge. This prevents the high voltage of the parasitic capacitance from affecting the cathode voltage of the photodiode after the photodiode stops illuminating the light, thus preventing the photodiode from malfunctioning. Notably, the sensor further incorporates a photodiode bias circuit, ensuring that the current induced by the sensor does not contain the current supplied by the current source, but only the current induced by the photodiode. Furthermore, this photodiode bias circuit allows the sensor to rapidly generate an induced current in response to the light signal reflected back to the photodiode.
[0076] The content disclosed above is only a preferred and feasible embodiment of this application and is not intended to limit the claims of this application. Therefore, all equivalent technical changes made based on the content of this application specification and drawings are included in the claims of this application.
Claims
1. A sensor with a photodiode bias circuit, characterized in that, The sensor with photodiode bias circuit includes: A photodiode, wherein the anode of the photodiode is grounded, and the photodiode is configured to convert light energy passing through the photodiode into a photocurrent; A first operational amplifier, wherein a first input terminal of the first operational amplifier is coupled to a reference voltage, and a second input terminal of the first operational amplifier is connected to the cathode of the photodiode; A first current source, the first end of which is connected to the cathode of the photodiode, and the second end of which is grounded; The first transistor has its control terminal connected to the output terminal of the first operational amplifier, and its first terminal connected to the cathode of the photodiode. The second transistor has its control terminal connected to the output terminal of the first operational amplifier. A first current mirror circuit includes a third transistor, a fourth transistor, and a fifth transistor. The first terminals of the third, fourth, and fifth transistors are coupled to a shared voltage. The second terminal of the third transistor is connected to the second terminal of the first transistor and a control terminal of the third transistor. The control terminal of the fourth transistor is connected to the control terminal of the third transistor, the second terminal of the fourth transistor, and the control terminal of the fifth transistor. The second terminal of the fifth transistor is connected to the first terminal of the second transistor. A pre-charge capacitor, the first terminal of which is coupled to the shared voltage, and the second terminal of which is connected to the control terminal of the third transistor; The first current source supplies current to charge the pre-charge capacitor to the target voltage value. Then, light shines through the photodiode. The pre-charge capacitor stores the current information from the previous stage at the control terminal of the third transistor and discharges. The discharge current flows to ground through the first current source. The current at the second terminal of the second transistor is the current sensed by the sensor with the photodiode bias circuit.
2. The sensor with a photodiode bias circuit according to claim 1, characterized in that, The sensor with photodiode bias circuit also includes a second current source, the first end of which is connected to the second end of the second transistor, and the second end of the second current source is grounded.
3. The sensor with a photodiode bias circuit according to claim 1, characterized in that, The sensor with photodiode bias circuit also includes a first switching assembly, a first end of which is connected to the control terminal of the third transistor, and a second end of which is connected to the second terminal of the first transistor and the control terminal of the fourth transistor.
4. The sensor with a photodiode bias circuit according to claim 2, characterized in that, The sensor with photodiode bias circuit further includes a second switching assembly, the first end of which is connected to the second end of the first transistor and the second end of the first switching assembly, and the second end of the second switching assembly is connected to the second end of the fourth transistor.
5. The sensor with a photodiode bias circuit according to claim 1, characterized in that, The sensor with a photodiode bias circuit also includes a first capacitor, the first end of which is connected to the output of the first operational amplifier, and the second end of which is connected to the cathode of the photodiode.