Light detection circuit with temperature compensation, flight time measurement device and electronic device

Abstract

The present invention relates to a light detection circuit, a time-of-flight measurement device, and an electronic device with temperature compensation. According to one embodiment, a light signal detection circuit may include: a first photodiode; a power supply circuit for providing an operating voltage to the first photodiode so that the first photodiode operates in a reverse overbiased state; and a first feedback loop for generating a first feedback signal based on a first voltage of the first photodiode, wherein the first voltage is associated with the reverse overbias voltage of the first photodiode, and the first feedback signal is provided to the power supply circuit to control the operating voltage so that the first voltage of the first photodiode is close to or equal to a target voltage.

Description

Technical Field

[0001] The present invention relates to an optical signal detection circuit with temperature compensation, a time-of-flight (Tof) measurement device including the optical signal detection circuit, and an electronic device including the time-of-flight measurement device. Background Art

[0002] Time of flight (ToF) measures the time it takes a particle or wave to travel a distance. By measuring the time difference between transmitting a detection signal and receiving the reflected echo signal, and then using the signal's propagation speed in a medium such as air, the distance between the signal source and the detected object can be calculated. ToF measurement technology is used in various applications such as distance measurement, facial recognition, and LiDAR.

[0003] A time-of-flight measurement device generally uses an optical signal such as infrared light, laser light, etc. as a detection signal, and uses a photodiode such as a single-photon avalanche diode (SPAD) to detect a reflected light signal. Figure 1 FIG1 shows an optical signal detection circuit, which includes a switching transistor 101, a SPAD 102, a reading circuit 103 and a DC-DC power supply circuit 110. The DC-DC power supply circuit 110 is used to apply an appropriate operating voltage V to the single photon avalanche diode 102. op , so that the single-photon avalanche diode 102 operates in a reverse over-bias state, that is, the reverse bias voltage (V DD -V op ) is greater than the breakdown voltage V bd Here, the reverse overbias voltage is defined as V eb =V DD -V op -V bd In the reverse over-bias state, the semiconductor depletion region of SPAD 102 absorbs photons and generates electron-hole pairs. Electrons and holes are separated and accelerated under the action of the electric field. If the electric field is large enough and the energy obtained by the electrons or holes is high enough, more electron-hole pairs will be generated through collision ionization, triggering a self-sustaining avalanche. Therefore, a single photon can generate a large signal of several volts or milliamperes in a short time. The reading circuit 103 can apply a control voltage V to the gate of the switching transistor 101, such as a PMOS transistor. bias The switch 101 is turned on and off to control the current flowing through the SPAD 102. The read circuit 103 is also used to read the signal generated by the SPAD 102 and perform necessary processing such as filtering, inversion, amplification, etc. to provide an output signal V out By measuring the signal V out , the arrival time of the photon can be determined, and then the distance between the light source and the detection object can be calculated.

[0004] The breakdown voltage V of the single-photon avalanche diode 102 bd Varies with temperature. Figure 2 The typical curve of the breakdown voltage of the single-photon avalanche diode as a function of temperature is shown in FIG. 1 , and it can be seen that the two are basically in a linear relationship. bd The reverse overbias voltage V on the single-photon avalanche diode changes with temperature. eb The photon detection rate (PDP) of the SPAD, i.e. the probability that a single photon triggers an avalanche, will also change with temperature changes. Therefore, in order to ensure a stable photon detection rate, it is necessary to compensate for the over-bias voltage drift of the SPAD caused by temperature changes.

[0005] Currently, two methods are generally used to perform temperature compensation for the reverse over-bias voltage of a single-photon avalanche diode. The first method is to use a temperature sensor located near the single-photon avalanche diode. Based on the measured temperature, a compensation current is introduced into the DC-DC power supply circuit 110 that powers the single-photon avalanche diode 102. By adjusting the operating voltage V provided by the DC-DC power supply circuit 110 to the single-photon avalanche diode 102, the compensation current is reduced. op To compensate for the reverse over-bias voltage V eb Drift due to temperature changes. The second method is to determine the temperature by measuring the dark count rate (DCR) of a dummy single-photon avalanche diode. The dark count rate is the count rate generated by avalanches caused by thermally excited carriers when no photons are incident, and it increases with increasing temperature. Figure 3 The relationship between the temperature and dark count rate of the single-photon avalanche diode is shown in FIG. As can be seen, as the temperature rises, the dark count rate DCR of the single-photon avalanche diode increases accordingly. Therefore, the temperature of the single-photon avalanche diode 102 can be determined by measuring the DCR, and then the compensation current can be introduced into the DC-DC power supply circuit 110. By adjusting the operating voltage V op To compensate for the reverse over-bias voltage V eb Drift due to temperature changes.

[0006] However, the current temperature compensation scheme still has some defects. For example, the single-photon avalanche diode and the temperature sensor are generally manufactured separately in different chips, and the temperatures of the two are not necessarily the same. Therefore, there may be a certain difference between the temperature value measured by the temperature sensor and the actual temperature value of the single-photon avalanche diode, and the temperature sensor also increases the cost. When the temperature is determined by measuring the dark count rate of a dummy single-photon avalanche diode, the dummy single-photon avalanche diode needs to be shielded to prevent photon incidence, resulting in the need for additional process steps to shield the dummy single-photon avalanche diode during the manufacturing process. In addition, the DC-DC power supply circuit that powers the single-photon avalanche diode may also have output errors, which will also vary with temperature, and traditional temperature compensation schemes cannot compensate for the output errors of the DC-DC power supply circuit.

[0007] Therefore, there is still a need for an improved temperature compensation scheme that can ensure that the single photon avalanche diode has a stable photon detection rate. Summary of the Invention

[0008] This application is filed to address the above and other issues.

[0009] One aspect of the present application provides an optical signal detection circuit, comprising: a first photodiode; a power supply circuit for providing an operating voltage to the first photodiode so that the first photodiode operates in a reverse over-biased state; and a first feedback loop for generating a first feedback signal based on a first voltage of the first photodiode, wherein the first voltage is associated with the reverse over-bias voltage of the first photodiode, and the first feedback signal is provided to the power supply circuit to control the operating voltage so that the first voltage of the first photodiode is close to or equal to a target voltage.

[0010] In some embodiments, the first feedback loop is triggered by an output signal of the optical signal detection circuit, so that when the first photodiode generates a current, the first feedback loop detects a first voltage of the first photodiode to generate the first feedback signal.

[0011] In some embodiments, the first feedback loop detects the first voltage from a first node, the power supply circuit provides the operating voltage to a second node, and the first node and the second node are located on opposite sides of the first photodiode. Alternatively, in some embodiments, the first node and the second node are located on the same side of the first photodiode, the first node is located between the second node and the first photodiode, and the quenching circuit is located between the first node and the second node.

[0012] In some embodiments, the first feedback loop includes: a comparator for comparing the first voltage of the first photodiode with the target voltage; a logic device (Logic) for generating a digital control signal based on the output signal of the comparator; and a current digital-to-analog converter (IDAC) for generating a feedback current based on the digital control signal output by the logic device, as the first feedback signal output by the first feedback loop. The power supply circuit includes a second feedback loop, and the feedback current output by the current digital-to-analog converter is provided to the second feedback loop of the power supply circuit to control the operating voltage output by the power supply circuit.

[0013] In some embodiments, the logic device adjusts the feedback current generated by the current digital-to-analog converter multiple times according to multiple logic levels in the output signal of the comparator, and the adjustment directions of the multiple adjustments are determined by the corresponding logic levels.

[0014] In some embodiments, the first feedback loop includes: an error amplifier (EA) having one input terminal receiving the first voltage of the first photodiode and another input terminal receiving the target voltage, thereby amplifying the voltage difference between the first voltage and the target voltage; and a current generating unit for generating a feedback current based on the voltage difference between the first voltage and the target voltage, as a first feedback signal output by the first feedback loop. The power supply circuit includes a second feedback loop, and the feedback current output by the current generating unit is provided to the second feedback loop of the power supply circuit to control the operating voltage output by the power supply circuit.

[0015] In some embodiments, the current generating unit includes: a resistor, one end of which is connected to the output end of the error amplifier, and the other end is connected to the virtual ground connection point in the second feedback loop of the power supply circuit; or a voltage-controlled current source, an input end of which is connected to the output end of the error amplifier, and an output end is connected to the virtual ground connection point in the second feedback loop of the power supply circuit.

[0016] In some embodiments, the first feedback loop includes a transconductance amplifier having one input receiving the first voltage of the first photodiode, another input receiving the target voltage, and an output providing a feedback current associated with the voltage difference between the first voltage and the target voltage as the first feedback signal. The power supply circuit includes a second feedback loop, and the feedback current output by the current generation unit is provided to the second feedback loop of the power supply circuit to control the operating voltage output by the power supply circuit.

[0017] In some embodiments, the first feedback loop includes an error amplifier (EA) having one input receiving the first voltage of the first photodiode and another input receiving the target voltage to generate a first feedback signal indicating a voltage difference between the first voltage and the target voltage. The power supply circuit includes a controller, and the first feedback signal is provided to the controller to control the operating voltage output by the power supply circuit.

[0018] In some embodiments, the first feedback loop includes: a comparator for comparing the first voltage of the first photodiode with the target voltage; and a logic device for generating a digital control signal based on the output signal of the comparator as the first feedback signal. The power supply circuit includes a controller, and the first feedback signal is provided to the controller to control the operating voltage output by the power supply circuit.

[0019] In some embodiments, the power supply circuit controls the operating voltage outputted by the power supply circuit according to the first feedback signal, so that a difference between the first voltage of the first photodiode and the target voltage is within 10% of the target voltage.

[0020] In some embodiments, the optical signal detection circuit further includes: one or more second photodiodes having the same structure as the first photodiode and powered by the operating voltage provided by the power supply circuit. The first photodiode is configured to control the operating voltage output by the power supply circuit via the first feedback loop during a first time period, and the second photodiode is configured to detect optical signals during a second time period, which is different from the first time period.

[0021] In some embodiments, the first photodiode and the second photodiode are single photon avalanche diodes.

[0022] Another aspect of the present application provides a method for compensating for changes in the reverse over-bias voltage of a photodiode, comprising: using a power supply circuit to provide an operating voltage to the photodiode so that the photodiode operates in a reverse over-bias state; detecting a first voltage of the photodiode, and generating a first feedback signal based on the first voltage and a predetermined target voltage, wherein the first voltage is associated with the reverse over-bias voltage of the photodiode; providing the first feedback signal to the power supply circuit to adjust the operating voltage so that the first voltage of the first photodiode is close to or equal to the target voltage to compensate for changes in the reverse over-bias voltage of the first photodiode.

[0023] In some embodiments, the first feedback signal is a voltage or current signal associated with a difference between the first voltage and the target voltage.

[0024] In some embodiments, the power supply circuit includes a feedback loop for controlling the operating voltage outputted by the power supply circuit, and the first feedback signal is provided to the feedback loop of the power supply circuit.

[0025] In some embodiments, the power supply circuit includes a controller for controlling the operating voltage outputted by the power supply circuit, and the first feedback signal is provided to the controller.

[0026] In some embodiments, detecting the first voltage of the photodiode includes detecting the first voltage of the first photodiode when the photodiode is triggered to generate a current. The first feedback loop detects the first voltage from a first node, the power supply circuit provides the operating voltage to a second node, and the first and second nodes are located on opposite sides of the first photodiode. Alternatively, the first and second nodes are located on the same side of the first photodiode, the first node is located between the second node and the first photodiode, and a quenching circuit is located between the first and second nodes.

[0027] Another aspect of the present application provides a time-of-flight measurement device, comprising: a light source for emitting detection light; the above-mentioned optical signal detection circuit for detecting reflected light generated by the detection object reflecting the detection light; and a processing module for determining the distance between the light source and the detection object based on the time difference between emitting the detection light and receiving the reflected light.

[0028] Another aspect of the present application provides an electronic device, which includes the above-mentioned time-of-flight measurement device.

[0029] The above and other features and advantages of the present invention will become apparent from the following description of specific embodiments with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A circuit diagram of an optical signal detection circuit is shown.

[0031] Figure 2 Graph showing the reverse breakdown voltage of a photodiode as a function of temperature.

[0032] Figure 3 Graph showing the dark count rate of a photodiode as a function of temperature.

[0033] Figure 4 FIG. 1 is a schematic circuit diagram of an optical signal detection circuit with temperature compensation according to an embodiment of the present invention.

[0034] Figure 5 Show Figure 4Schematic diagram of the changes in the cathode voltage and output voltage of the photodiode.

[0035] Figure 6 A schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention is shown.

[0036] Figure 7 A schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention is shown.

[0037] Figure 8 A schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention is shown.

[0038] Figure 9 A schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention is shown.

[0039] Figure 10 A schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention is shown.

[0040] Figure 11 A schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention is shown.

[0041] Figure 12 A flow chart illustrating a method for compensating for a reverse over-bias voltage variation of a photodiode according to an embodiment of the present invention is shown.

[0042] Figure 13 FIG. 4 shows a structural block diagram of a flight time measurement device according to an embodiment of the present invention.

[0043] Figure 14 A structural block diagram of an electronic device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0044] Below, example embodiments according to the present application will be described in detail with reference to the accompanying drawings. Note that the drawings may not be drawn to scale. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments of the present application, and the present application is not limited to the example embodiments described herein.

[0045] Figure 4 FIG. 1 shows a schematic circuit diagram of an optical signal detection circuit with temperature compensation according to an embodiment of the present invention. Figure 4As shown, a photodiode 102 can be used to detect light signals. In some embodiments, the photodiode 102 can be a single photon avalanche diode, but it should be understood that the principles of the present invention can also be applied to other diodes with photodetection capabilities. The cathode node N1 of the single photon avalanche diode 102 can be connected to a voltage V DD The gate of the switch transistor 101 can receive a control voltage V provided by the reading circuit 103. bias To control the on and off of the switch transistor 101. The anode node N2 of the single photon avalanche diode 102 can be connected to the power supply circuit 110 to receive the operating voltage V op Although the power supply circuit 110 is shown as a DC-DC converter, it should be understood that other power supply circuits can also be used. Here, an appropriate voltage V op and V DD , so that the single photon avalanche diode 102 operates in a reverse over-bias state, that is, (V DD -V op ) is greater than the reverse breakdown voltage V of the single photon avalanche diode 102 bd For the convenience of description, the reverse over-bias voltage of the single-photon avalanche diode 102 is defined as V eb =V DD -V op -V bd The reading circuit 103 can read the voltage signal at the cathode node N1 of the single photon avalanche diode 102 and perform necessary processing, such as filtering, inversion, amplification, etc., and then provide an output signal V out .

[0046] The DC-DC power supply circuit 110 used here may be a step-down DC-DC converter that provides a negative voltage, which may include an inductor L1 and a controller 112. The input end of the inductor L1 may receive an input voltage V of, for example, 3.3V. in , and a filter capacitor C1 is provided, the output end of the inductor L1 can provide an output voltage V through the diode D1 op , output voltage V op The voltage V can be a negative voltage, such as -25V, to make the single-photon avalanche diode 102 work in a reverse over-bias state, and a capacitor C2 can be connected in parallel to the output terminal. The controller 112 can control the on and off of a switch (not shown, which can be included in the controller 112) that connects the output terminal of the inductor L1 to the ground. When the switch is turned on, the input voltage V inThe inductor L1 is charged and the capacitor C2 is discharged to the load; when the switch is turned off, the inductor L1 supplies power to the load and charges the capacitor C2. The controller 112 can be a pulse width modulation (PWM) controller, a pulse frequency modulation (PFM) controller, or a pulse step modulation (PSM) controller, which provides the desired output voltage V by modulating the charging and discharging pulse width, frequency, or step of the inductor L1. op As an example of a PWM controller, the controller 112 may adopt a TPS61170 control chip, for example.

[0047] To ensure accurate output voltage V op The DC-DC power supply circuit 110 may further include a feedback loop 114, which can increase the output voltage V op Feedback is sent to the controller 112, so that the controller 112 can op To regulate the charging and discharging process of the inductor L1 to provide an accurate output voltage V op Specifically, the feedback loop 114 may include a voltage divider circuit consisting of at least two resistors R1 and R2, which are connected to the output voltage V op and the power supply voltage V DD The virtual ground node N3 between the resistors R1 and R2 can be connected to the controller 112, which can generate a voltage signal based on the voltage of the virtual ground node N3 (which is proportional to the output voltage V op The ratio depends on the resistance values ​​of resistors R1 and R2) to control the charging and discharging process of inductor L1 to generate the desired output voltage V op It should be understood that the DC-DC converter described here is only an example of the power supply circuit 110 , and the DC-DC converter may have other circuit structures, and the power supply circuit 110 may also adopt other power supply circuits with feedback control.

[0048] Here, the feedback loop 114 can control the output voltage V op , but when the reverse breakdown voltage V bd When the reverse over-bias voltage V of the single-photon avalanche diode 102 changes with temperature, eb The reverse bias voltage V eb With the change of temperature, Figure 4 The circuit shown in FIG. 1 further includes a feedback loop 120 for adjusting the reverse bias voltage V of the single photon avalanche diode 102. ebThe first voltage associated with the power supply circuit 110 is used to generate a feedback signal, and the feedback signal is provided to the power supply circuit 110. The power supply circuit 110 further considers the feedback signal to control the operating voltage V outputted by the power supply circuit 110. op , so that the first voltage of the single photon avalanche diode 102 is maintained at a desired voltage, thereby compensating for the reverse over-bias voltage V eb For the convenience of description, the feedback loop 120 is referred to as a first feedback loop, which provides a first feedback signal; and the feedback loop 114 of the power supply circuit 110 itself is referred to as a second feedback loop, which provides a second feedback signal.

[0049] Continue to refer to Figure 4 The first feedback loop 120 may include a comparator (COMP) 122. One input terminal of the comparator 122 may be connected to the cathode node N1 of the single photon avalanche diode 102 to receive the cathode voltage V cath , the other input terminal can receive the target voltage V level , and the comparator 122 can be output by the output signal V of the optical signal detection circuit out Triggering, so that when the single photon avalanche diode 102 generates photocurrent, the cathode voltage V cath and the target voltage V level For example, when the cathode voltage V cath Greater than the target voltage V level When the comparator 122 outputs a high level, the cathode voltage V cath Less than the target voltage V level When , the comparator 122 outputs a low level, or vice versa.

[0050] The first feedback loop 120 may further include a logic device 124 and a current digital-to-analog converter (IDAC) 126. The logic device 124 may generate a digital control signal based on the comparison result of the comparator 122, and the IDAC 126 may generate a feedback current based on the digital control signal provided by the logic device 124, as the first feedback signal generated by the first feedback loop 120, and provided to the DC-DC power supply circuit 110 to control the operating voltage V outputted by the DC-DC power supply circuit 110. op , which can make the cathode voltage V at the cathode node N1 of the single photon avalanche diode 102 cath Maintained close to or substantially equal to the target voltage V level For example, the cathode voltage V cath and the target voltage V level The difference between the target voltage V level 10% of the range, preferably within the range of 5%, or the cathode voltage V cath and the target voltage V levelThe difference between the two values ​​is within a predetermined range, such as 200 mV, preferably within 100 mV. In some embodiments, the IDAC 126 can provide the first feedback signal generated by it to the second feedback loop 114 of the DC-DC power supply circuit 110, thereby controlling the output of the DC-DC power supply circuit 110 together with the second feedback signal. For example, Figure 4 As shown, the output of the IDAC 126 may be connected to a virtual ground node N3 between the voltage-dividing resistors R1 and R2 in the second feedback loop 114 .

[0051] The logic device 124 can generate a voltage V according to the cathode voltage V provided by the comparator 122. cath and the target voltage V level The comparison results between the two are used to adjust the feedback signal using various algorithms to control the operating voltage V output by the DC-DC power supply circuit 110. op , thereby controlling the cathode voltage V of the photon avalanche diode 102 cath . Figure 5 The binary search algorithm is used to find the cathode voltage V cath The output signal V of the optical signal detection circuit is shown in FIG. out and the cathode voltage V of the photon avalanche diode 102 cath The change curve of the target voltage V level As mentioned above, the output signal V out The comparator 122 is triggered to perform a comparison operation. To illustrate the cathode voltage V when there is no feedback loop 120 cath changes in Figure 5 The target voltage V is applied only during the second trigger. level (Indicated by thick solid line), at this time the cathode voltage V cath Less than the target voltage V level , so the logic device 124 generates a control signal to reduce the cathode voltage V cath Increase the first predetermined amplitude. When the third trigger is triggered, the cathode voltage V of the first predetermined amplitude is increased. cath becomes greater than the target voltage V level , so the logic device 124 generates a control signal to reduce the cathode voltage V cath Reduce the second predetermined amplitude, which may be half of the first predetermined amplitude, so that the cathode voltage V cath Closer to the target voltage V level At the fourth trigger, the cathode voltage V is reduced by a second predetermined amplitude. cath becomes smaller than the target voltage V level , so the logic device 124 generates a control signal to reduce the cathode voltage V cathIncrease the third predetermined amplitude, wherein the third predetermined amplitude may be half of the second predetermined amplitude, so that the cathode voltage V cath Closer to the target voltage V level In this way, the logic device 124 can cath Perform a predetermined number of adjustments, with each adjustment being half the amplitude of the previous adjustment, so that the cathode voltage V cath Close to or substantially equal to the target voltage V level .exist Figure 5 In the example shown in FIG, four adjustments are performed, but it should be understood that an appropriate first adjustment amplitude and adjustment amplitude change ratio may be selected according to accuracy requirements, and more or fewer adjustment times may be used.

[0052] It should also be understood that Figure 5 The binary search algorithm shown is only an example, and other algorithms can also be used to calculate the cathode voltage V cath For example, the cathode voltage V cath Adjust an equal small amount until the comparison result is reversed, which ensures that the cathode voltage V cath and the target voltage V level Of course, other adjustment algorithms can also be used, which will not be listed here one by one.

[0053] As mentioned above, the cathode voltage V of the photon avalanche diode 102 is cath is its reverse overbias voltage V eb Related. Figure 4 and Figure 5 It can be understood that when the photon avalanche diode 102 does not generate photocurrent, its cathode voltage V cath Basically equal to the power supply voltage V DD When the photon avalanche diode 102 triggers the photocurrent, its cathode voltage V cath Equal to the power supply voltage V DD With reverse bias voltage V eb The difference between them, namely V cath =V DD -V eb Therefore, the cathode voltage V cath The change amplitude is basically equal to the reverse overbias voltage V eb As described above, the first feedback loop 120 is used so that the cathode voltage V cath Can be kept close to or equal to the target voltage V level , does not change with temperature, it can make the reverse bias voltage V ebDoes not change with temperature. In other words, the reverse over-bias voltage V eb Temperature compensation.

[0054] exist Figure 4 In the circuit shown, the operating voltage V op and the voltage V fed back by the first feedback loop 120 cath are located on both sides of the single photon avalanche diode 102, namely V op Located on the anode side, V cath Located on the cathode side, but it should be understood that in other embodiments, the operating voltage V op Alternatively, the power supply circuit 110 and the first feedback loop 120 may be located on the cathode side of the single-photon avalanche diode 102, such as at the node N1. The voltage fed back by the first feedback loop 120 may also be located on the anode side, such as at the node N2. Alternatively, the power supply circuit 110 and the first feedback loop 120 may be connected to the same side of the single-photon avalanche diode 102, such as the cathode side or the anode side. These embodiments are described below.

[0055] Figure 6 FIG2 shows a schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention. Figure 4 The embodiment shown is different in that the DC-DC power supply circuit 110 ′ is connected to the cathode node N1 of the single-photon avalanche diode 102 , while the first feedback loop 120 is connected to the anode node N2 of the single-photon avalanche diode 102 .

[0056] Reference Figure 6 The power supply circuit 110' is a boost DC-DC converter circuit that provides a positive voltage, which provides a high voltage V of, for example, +25V. op , so that the single photon avalanche diode 102 operates in a reverse over-biased state. The connection direction of the diode D1 in the power supply circuit 110' is the same as Figure 4 In contrast to the step-down DC-DC converter, the voltage dividing resistors R1 and R2 in the feedback loop 114 are connected between the output voltage Vop and the ground GND, that is, one end of the resistor R2 is grounded. Other aspects of the step-up DC-DC power supply circuit 110' are similar to those of the step-up DC-DC power supply circuit 110'. Figure 4 It should also be understood that the step-down DC-DC converter may also have other circuit structures, and the power supply circuit 110' may also adopt other power supply circuits with feedback control.

[0057] Continue to refer to Figure 6The reading circuit 103 and the feedback loop 120 are connected to the anode node N2 of the single-photon avalanche diode 102, and a quenching circuit 104 may also be provided on the anode side of the single-photon avalanche diode 102. Although not shown, the quenching circuit 104 may include a switching transistor, such as an NMOS transistor, for controlling the current flowing through the single-photon avalanche diode 102. The feedback loop 120 may be connected to Figure 4 The feedback loop 120 shown is substantially the same and a detailed description thereof will not be repeated here.

[0058] exist Figure 6 In the example shown, the feedback loop 120 is based on the anode voltage V anod Generate a feedback signal and provide it to the DC-DC power supply circuit 110'. It can be understood that the anode voltage V anod Also with its reverse overbias voltage V eb Specifically, when the single-photon avalanche diode 102 does not trigger photocurrent, the anode voltage V anod is substantially equal to the ground voltage; when the single photon avalanche diode 102 triggers the photocurrent, the anode voltage V anod The rise is basically equal to the reverse bias voltage V eb Therefore, with Figure 4 The principle is similar to that of the feedback loop 120 to control the operating voltage V output by the DC-DC power supply circuit 110 ′. op , the anode voltage V when the single photon avalanche diode 102 triggers the photocurrent anod Maintained at a predetermined constant level V level , thus the reverse over-bias voltage V eb Perform temperature compensation to prevent it from changing with temperature.

[0059] Figure 7 FIG2 shows a schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention. Figure 6 The embodiment shown differs in that Figure 7 In the embodiment shown, the boost DC-DC power supply circuit 110', the feedback loop 120 and the read circuit 103 are all connected to the same side of the single photon avalanche diode 102, namely the cathode side. Figure 7As shown, the feedback loop 120 and the readout circuit 103 are connected to the cathode node N1 of the single-photon avalanche diode 102, the DC-DC power supply circuit 110' is connected to the cathode-side node N1', the node N1 is located between the node N1' and the single-photon avalanche diode 102, and the quenching circuit 104 is located between the node N1 and the node N1'. In this embodiment, the quenching circuit 104 may include a switching transistor, such as a PMOS transistor, for controlling the current flowing through the single-photon avalanche diode 102.

[0060] exist Figure 7 In the embodiment shown, the feedback loop 120 is based on the cathode voltage V cath Generate a feedback signal and provide it to the DC-DC power supply circuit 110'. It can be understood that when the single photon avalanche diode 102 does not trigger the photocurrent, the cathode voltage V cath Basically equal to the operating voltage V op When the single photon avalanche diode 102 triggers the photocurrent, the cathode voltage V cath The drop is basically equal to the reverse bias voltage V eb , that is, cathode voltage V cath Equal to (V op -V eb ). Therefore, with Figure 4 The principle is similar to that of the feedback loop 120 to control the operating voltage V output by the DC-DC power supply circuit 110 ′. op , the cathode voltage V when the single photon avalanche diode 102 triggers the photocurrent cath Maintained at a predetermined constant level V level , thus the reverse over-bias voltage V eb Perform temperature compensation to prevent it from changing with temperature.

[0061] Figure 8 FIG. 1 is a schematic circuit diagram of an optical signal detection circuit with temperature compensation according to another embodiment of the present invention. Figure 8 In the embodiment of FIG. 1 , the step-down DC-DC power supply circuit 110 , the feedback loop 120 , and the read circuit 103 are all connected to the same side of the single-photon avalanche diode 102 , namely, the anode side. Figure 8 As shown, the feedback loop 120 and the readout circuit 103 are connected to the anode node N2′ of the single-photon avalanche diode 102, the DC-DC power supply circuit 110 is connected to the anode-side node N2, the node N2′ is located between the node N2 and the single-photon avalanche diode 102, and the quenching circuit 104 is located between the node N2′ and the node N2. In this embodiment, the quenching circuit 104 may include a switching transistor, such as an NMOS transistor, for controlling the current flowing through the single-photon avalanche diode 102.

[0062] exist Figure 8 In the example shown, the feedback loop 120 is based on the anode voltage V anod Generate a feedback signal and provide it to the DC-DC power supply circuit 110. It can be understood that the anode voltage V anod Also with its reverse overbias voltage V eb Specifically, when the single-photon avalanche diode 102 does not trigger photocurrent, the anode voltage V anod Basically equal to the operating voltage V op In this embodiment, it has a negative value, such as -25V, and of course it can be set to other appropriate negative values; when the single photon avalanche diode 102 triggers the photocurrent, the anode voltage V anod The rise is basically equal to the reverse bias voltage V eb Therefore, the operating voltage V output by the DC-DC power supply circuit 110 ′ is controlled by the feedback loop 120 . op , the anode voltage V when the single photon avalanche diode 102 triggers the photocurrent anod Maintained at a predetermined constant level V level , can be reverse bias voltage V eb Perform temperature compensation to prevent it from changing with temperature.

[0063] Refer to above Figure 4 、 6 -7 describes different connection methods of the power supply circuit 110 and the feedback loop 120 with respect to the single photon avalanche diode 102, which will be referred to below. Figure 9-11 Describe different embodiments of feedback loops. Figure 9-11 In the embodiment of the present invention, the connection mode of the power supply circuit and the feedback loop is basically the same as that of Figure 4 The embodiments shown are the same, but it should be understood that Figure 9-11 The feedback loop shown can also be used instead of the feedback loop 120. Figure 6-7 In the embodiment shown in FIG. , the description of the repeated parts will be omitted and the main description will be given. Figure 9-11 The parts of the embodiment that are different from the above-mentioned embodiment.

[0064] First refer to Figure 9 , unlike the feedback loop 120, the feedback loop 130 is implemented using an analog circuit, while the feedback loop 120 is implemented using a digital circuit. Figure 9 As shown, the feedback loop 130 includes an error amplifier (EA) 132, whose non-inverting input terminal can receive the target voltage V level The inverting input terminal can receive the cathode voltage V of the single photon avalanche diode 102 cath, or vice versa, to amplify the voltage difference between the two. The error amplifier 132 is also triggered by the output signal Vout of the light signal detection circuit, that is, when the photocurrent is detected, the cathode voltage V cath and the target voltage V level The current generating unit 134 can be based on the cathode voltage V cath and the target voltage V level The voltage difference between the output of the error amplifier 132 and the node N3 generates a feedback current, which is provided as a first feedback signal to the virtual ground node N3 in the second feedback loop 114 of the DC-DC power supply circuit 110. Examples of the current generating unit 134 may include, for example, a voltage-controlled current source or a resistor, which is connected between the output of the error amplifier 132 and the node N3, generates a corresponding current based on the voltage signal output by the error amplifier 132, and provides the current to the node N3.

[0065] In some embodiments, the error amplifier (EA) 132 and the current generating unit 134 can be formed together as a transconductance amplifier. A transconductance amplifier is a voltage-controlled current source that converts an input differential voltage into an output current signal. It has advantages such as good high-frequency performance and high conversion rate. One input terminal of the transconductance amplifier can receive a cathode voltage V cath , the other input terminal can receive the target voltage V level , the output terminal provides the cathode voltage V cath and the target voltage V level The voltage difference between them is correlated to a proportional current signal, for example.

[0066] Refer to above Figure 4 and 9 In the described embodiment, the feedback loops 120 and 130 can be implemented outside the chip of the DC-DC power supply circuit 110 / 110', that is, an off-chip implementation is adopted. For example, the controller 112 of the DC-DC power supply circuit 110 / 110' can use a commercially available off-the-shelf control chip, such as TPS61170, which integrates an error amplifier, a PWM controller, etc. The feedback loop 120 / 130 can provide a feedback signal to the feedback signal pin of the control chip. In other embodiments, the feedback loop 120 / 130 is used to control the reverse over-bias voltage V eb The feedback loop for temperature compensation can also be implemented on-chip, implemented in the control chip of the power supply circuit 110, or can be implemented outside the control chip, but can replace the original second feedback loop 114 of the control chip. Figure 10 and 11 Such an embodiment is described.

[0067] First refer to Figure 10 , which shows the feedback loop 140 implemented by the analog circuit. Figure 10As shown, the feedback loop 140 may include an error amplifier 142, which may be implemented outside the controller 112 or as part of the controller 112. The non-inverting input of the error amplifier 142 may receive the target voltage V level , the inverting input terminal can receive the cathode voltage V cath , and the error amplifier 142 can be output by the output signal V of the optical signal detection circuit out Triggering, so that when the single photon avalanche diode 102 generates photocurrent, it outputs the target voltage V level and cathode voltage V cath The controller 112 can amplify the voltage difference between the target voltage V level and cathode voltage V cath The voltage difference between the two is used to perform pulse width, frequency or step modulation to adjust the output voltage V of the power supply circuit 110. op , thereby making the cathode voltage V cath Close to or substantially equal to the target voltage V level .exist Figure 10 In the embodiment of the present invention, the second feedback loop 114 of the DC-DC power supply circuit 110 itself can be omitted (see Figure 4 ), and only the feedback loop 140 is used to realize the output voltage V op and the cathode voltage V of the single photon avalanche diode 102 cath Control of both.

[0068] Figure 11 1 shows a feedback loop 150 implemented by a digital circuit. Figure 11 As shown, the feedback loop 150 may include a comparator 152 and a logic device 154, which may be implemented outside the controller 112 or as part of the controller 112. Figure 4 Similar to the comparator 122 and logic device 124 described above, the comparator 152 can compare the cathode voltage V cath and the target voltage V level , and outputs a high level or low level signal indicating the comparison result. The logic device 154 can generate a digital control signal based on the comparison result output by the comparator 152, and provide it to the controller 112 as a first feedback signal, so that the controller 112 can adjust the output voltage V of the power supply circuit 110 according to the digital control signal. op , thereby making the cathode voltage V cath Close to or substantially equal to the target voltage V levelAs previously mentioned, the logic device 154 can utilize various algorithms, such as but not limited to a binary search algorithm, to generate a digital control signal based on the comparison result output by the comparator 152. Figure 10 Same, in Figure 11 In the embodiment, the second feedback loop 114 of the DC-DC power supply circuit 110 itself can be omitted (see Figure 4 ), and only the feedback loop 150 is used to realize the output voltage V op and the cathode voltage V of the single photon avalanche diode 102 cath Control of both.

[0069] The embodiments of the feedback loops 120, 130, 140 and 150 are described above, which are based on the output signal V of the optical signal detection circuit. out The cathode or anode voltage of the photodiode 102 is detected when the photodiode 102 generates a photocurrent, and a feedback signal is generated based on the voltage to control the operating voltage V output by the power supply circuit 110 / 110'. op , thereby compensating the reverse over-bias voltage V of the photodiode 102 eb It can be understood that when the feedback loop is triggered to compensate for the reverse over-bias voltage V eb As the temperature changes, the operating voltage V op Then the reverse overbias voltage V eb Therefore, the process is not suitable for using the photodiode 102 to detect light signals to measure, for example, time of flight, because voltage fluctuations may lead to inaccurate measurements. Therefore, in some embodiments, a feedback loop may be triggered in the first time period to perform the above-mentioned temperature compensation. In the second time period after performing temperature compensation, the reverse over-bias voltage V eb When the voltage is stabilized at a certain level, the photodiode 102 can be used to detect the optical signal.

[0070] In some embodiments, the photodiode 102 can be dedicated to the above-mentioned temperature compensation process, and one or more photodiodes for optical signal detection having the same structure as the photodiode 102 can be additionally formed, which are also powered by the power supply circuit 110 / 110'. Here, the photodiode 102 can be referred to as the first compensation photodiode, and the one or more additionally formed photodiodes can be referred to as the second detection photodiode. In the first time period, the first compensation photodiode can be used to perform the above-mentioned temperature compensation process. It should be understood that the first compensation photodiode can be unshielded, and it uses the photocurrent generated by the external light signal to perform the above-mentioned temperature compensation process; or the first compensation photodiode can be a shielded dummy photodiode, which uses the thermal excitation current to perform the above-mentioned temperature compensation process. In the second time period after the temperature compensation process is performed, the compensated power supply circuit can be used to power one or more second detection photodiodes to perform the optical signal detection task.

[0071] Figure 12 A flow chart showing a method for compensating for a reverse over-bias voltage variation of a photodiode according to an embodiment of the present invention is shown. Figure 4-11 Therefore, only a brief description of the method is given here.

[0072] Reference Figure 12 In step 210, a power supply circuit may be used to provide an operating voltage to the photodiode, so that the photodiode operates in a reverse over-bias state.

[0073] In step 220, a first feedback loop can be used to detect a first voltage of the photodiode associated with a reverse overbias voltage, and a first feedback signal can be generated based on the first voltage and a predetermined target voltage. For example, a first voltage value of the photodiode can be detected when the photodiode is triggered to generate a photocurrent. The first feedback loop can detect the first voltage from a first node, the power supply circuit can provide the operating voltage to a second node, and the first node and the second node can be located on opposite sides of the photodiode, respectively. Alternatively, the first node and the second node can be located on the same side of the photodiode, the first node is located between the second node and the photodiode, and the quenching circuit can be provided between the first node and the second node. In some embodiments, the generated first feedback signal can be a voltage or current signal associated with a voltage difference between the first voltage and the target voltage.

[0074] In step 230, a first feedback signal may be provided to the power supply circuit to adjust the operating voltage provided by the power supply circuit so that the first voltage of the photodiode approaches or is substantially equal to the target voltage, thereby compensating for temperature-dependent changes in the reverse overbias voltage of the photodiode. In some embodiments, the power supply circuit may include a second feedback loop for controlling the operating voltage outputted by the power supply circuit, and the first feedback signal may be provided to the second feedback loop of the power supply circuit itself. In some embodiments, the power supply circuit includes a controller for controlling the operating voltage outputted by the power supply circuit, and the first feedback signal may be provided to the controller.

[0075] The optical signal detection circuit described above can be used in, for example, a time-of-flight measurement device. Figure 13 FIG. 3 shows a structural block diagram of a flight time measurement device 300 according to an embodiment of the present invention. Figure 13 As shown, the time-of-flight measurement device 300 may include a light source 320, which may be, for example, a laser light source. A driving circuit 310 may drive the laser light source 320 to emit laser light. A detection circuit 330, which may be, for example, the optical signal detection circuit discussed above, may detect the return light after the laser light emitted by the light source 320 is reflected by an object. A processing module 340 may calculate the time difference between the emission time of the light source 320 and the reception time of the detection circuit 330, i.e., the flight time of the light, and further calculate the distance between the light source 320 and the illuminated object based on the speed of light.

[0076] Figure 13 The time-of-flight measurement device 300 shown can be used to Figure 14 In the electronic device 400 shown. For example, the electronic device 400 can be an electronic device with a camera function, such as a mobile phone, which uses the distance determined by the time-of-flight measurement device 300 to automatically adjust the focus to achieve clear imaging of objects. The electronic device 400 can also be, for example, a vehicle-mounted laser radar, which uses the time-of-flight measurement device 300 to measure the flight time of laser light and thereby determine the distance to objects around the vehicle or perform laser imaging. It is understood that the electronic device 400 can also be any other mobile electronic device.

[0077] The basic principles of the present application have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this application are merely illustrative and not restrictive, and it should not be assumed that these advantages, strengths, and effects are required of each embodiment of this application. In addition, the specific details disclosed above are merely illustrative and facilitating understanding, and are not restrictive. The above details do not limit this application to necessarily being implemented using the above specific details.

[0078] The block diagrams of the devices, devices, equipment, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As will be appreciated by those skilled in the art, these devices, devices, equipment, and systems can be connected, arranged, or configured in any manner. Words such as "include," "comprise," "have," and the like are open-ended words, meaning "including but not limited to," and can be used interchangeably therewith. The words "or" and "and" used herein refer to the words "and / or" and can be used interchangeably therewith, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to," and can be used interchangeably therewith.

[0079] It should also be noted that in the apparatus, device, and method of the present application, each component or each step can be decomposed and / or recombined, and such decomposition and / or recombination should be regarded as equivalent solutions of the present application.

[0080] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0081] The above description has been provided for the purpose of illustration and description. Furthermore, this description is not intended to limit the embodiments of the present application to the forms disclosed herein. Although a number of example aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. An optical signal detection circuit, comprising: a first photodiode; a power supply circuit, configured to provide an operating voltage to the first photodiode so as to enable the first photodiode to operate in a reverse overbias state; as well as a first feedback loop for generating a first feedback signal based on a first voltage of the first photodiode, wherein the first voltage is associated with a reverse overbias voltage of the first photodiode, and providing the first feedback signal to the power supply circuit to control the operating voltage so that the first voltage of the first photodiode is close to or equal to a target voltage; Wherein, the first feedback loop includes: a comparator, configured to compare the first voltage of the first photodiode with the target voltage; a logic device, configured to generate a digital control signal according to an output signal of the comparator; and a current digital-to-analog converter, configured to generate a feedback current according to the digital control signal output by the logic device as a first feedback signal output by the first feedback loop, The power supply circuit includes a second feedback loop, and the feedback current output by the current digital-to-analog converter is provided to the second feedback loop of the power supply circuit to control the operating voltage output by the power supply circuit.

2. The optical signal detection circuit according to claim 1, wherein: The first feedback loop is triggered by an output signal of the optical signal detection circuit, so that when the first photodiode generates a current, the first feedback loop detects a first voltage of the first photodiode to generate the first feedback signal.

3. The optical signal detection circuit according to claim 1, wherein: The first feedback loop detects the first voltage from a first node, the power supply circuit provides the operating voltage to a second node, the first node and the second node are located on opposite sides of the first photodiode, respectively, or The first node and the second node are located on the same side of the first photodiode, the first node is located between the second node and the first photodiode, and a quenching circuit is located between the first node and the second node.

4. The optical signal detection circuit according to claim 1, wherein: The logic device adjusts the feedback current generated by the current digital-to-analog converter multiple times according to multiple logic levels in the output signal of the comparator, and the adjustment directions of the multiple adjustments are determined by the corresponding logic levels.

5. The optical signal detection circuit according to claim 1, wherein: Alternatively, the first feedback loop comprises: an error amplifier having one input terminal receiving the first voltage of the first photodiode and another input terminal receiving the target voltage, so as to amplify a voltage difference between the first voltage and the target voltage; and a current generating unit, configured to generate a feedback current based on a voltage difference between the first voltage and the target voltage as a first feedback signal output by the first feedback loop, The power supply circuit includes a second feedback loop, and the feedback current output by the current generating unit is provided to the second feedback loop of the power supply circuit to control the operating voltage output by the power supply circuit.

6. The optical signal detection circuit according to claim 5, wherein: The current generating unit includes: a resistor, one end of which is connected to the output terminal of the error amplifier, and the other end of which is connected to a virtual ground connection point in the second feedback loop of the power supply circuit; or A voltage-controlled current source has an input end connected to the output end of the error amplifier, and an output end connected to a virtual ground connection point in the second feedback loop of the power supply circuit.

7. The optical signal detection circuit according to claim 1, wherein: Alternatively, the first feedback loop comprises: a transconductance amplifier having one input terminal receiving the first voltage of the first photodiode, another input terminal receiving the target voltage, and an output terminal providing a feedback current associated with a voltage difference between the first voltage and the target voltage as the first feedback signal, The power supply circuit includes a second feedback loop, and the feedback current output by the current generating unit is provided to the second feedback loop of the power supply circuit to control the operating voltage output by the power supply circuit.

8. The optical signal detection circuit according to claim 1, wherein: Alternatively, the first feedback loop comprises: an error amplifier having one input terminal receiving the first voltage of the first photodiode and another input terminal receiving the target voltage to generate the first feedback signal indicating a voltage difference between the first voltage and the target voltage, The power supply circuit includes a controller, and the first feedback signal is provided to the controller to control the operating voltage output by the power supply circuit.

9. The optical signal detection circuit according to claim 1, wherein: Alternatively, the first feedback loop comprises: a comparator, configured to compare the first voltage of the first photodiode with the target voltage; a logic device, configured to generate a digital control signal according to an output signal of the comparator as the first feedback signal, The power supply circuit includes a controller, and the first feedback signal is provided to the controller to control the operating voltage output by the power supply circuit.

10. The optical signal detection circuit according to claim 1, wherein: The power supply circuit controls the operating voltage outputted therefrom according to the first feedback signal, so that a difference between the first voltage of the first photodiode and the target voltage is within 10% of the target voltage.

11. The optical signal detection circuit according to claim 1 , further comprising: One or more second photodiodes, having the same structure as the first photodiode, powered by the operating voltage provided by the power supply circuit, The first photodiode is configured to control the operating voltage output by the power supply circuit through the first feedback loop during a first period, and the second photodiode is configured to detect an optical signal during a second period, which is different from the first period.

12. The optical signal detection circuit according to claim 11, wherein: The first photodiode and the second photodiode are single photon avalanche diodes.

13. A method for compensating for a change in reverse over-bias voltage of a photodiode using the optical signal detection circuit according to any one of claims 1 to 12, comprising: Using a power supply circuit to provide an operating voltage to the photodiode so that the photodiode operates in a reverse overbias state; detecting a first voltage of the photodiode using a first feedback loop, and generating a first feedback signal based on the first voltage and a predetermined target voltage, the first voltage being associated with a reverse overbias voltage of the photodiode; The first feedback signal is provided to the power supply circuit to adjust the operating voltage so that the first voltage of the photodiode is close to or equal to the target voltage to compensate for the change of the reverse over-bias voltage of the photodiode.

14. The method of claim 13, wherein: Detecting a first voltage of the photodiode includes: detecting a first voltage of the photodiode when the photodiode is triggered to generate current, wherein the first feedback loop detects the first voltage from a first node, the power supply circuit provides the operating voltage to a second node, and the first node and the second node are located on opposite sides of the photodiode, respectively; or The first node and the second node are located on the same side of the photodiode, the first node is located between the second node and the photodiode, and a quenching circuit is located between the first node and the second node.

15. A time-of-flight measurement device, comprising: a light source, for emitting detection light; The optical signal detection circuit according to any one of claims 1 to 12, configured to detect reflected light generated by a detection object reflecting the detection light; as well as A processing module is used to determine the distance between the light source and the detection object based on the time difference between emitting the detection light and receiving the reflected light. 16 . An electronic device comprising the time-of-flight measuring device according to claim 15 .

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