Laser receiving circuit and laser radar

Abstract

The utility model proposes a laser receiving circuit and a laser radar, the laser receiving circuit comprises an avalanche photodiode, a bias voltage generation circuit, an amplification circuit and a compensation circuit, the avalanche photodiode is driven by a negative bias voltage to carry out photoelectric conversion on a received laser pulse and generate an avalanche current, and the avalanche current is transmitted to the amplification circuit. When interference of ambient light or strong reflected light emitted by the laser emission circuit is received, the compensation circuit generates compensation current opposite to avalanche current based on voltage echo signals output by the amplification circuit, input signals of the amplification circuit are reduced, saturation of the amplification circuit is avoided, the dynamic range of the amplification circuit is enlarged, and the receiving sensitivity of the amplification circuit is improved. And the ranging accuracy and the environmental adaptability of the laser radar are improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of laser radar, and in particular relates to a laser receiving circuit and a laser radar. Background Art

[0002] LiDAR ranging systems are increasingly used in application scenarios such as unmanned driving. LiDAR determines distance information and reflectivity based on the time difference between laser emission and laser reception.

[0003] Among them, avalanche photodiodes, as commonly used photodetectors in laser radars, can detect weak light signals using the avalanche effect of photogenerated carriers, and have the advantages of high performance and high sensitivity. In actual application scenarios, when the laser emitted by the laser radar itself illuminates an object with a high emissivity at close range, the reflected signal will cause the avalanche photodiode to produce a strong avalanche effect, leading to saturation of the subsequent amplifier and affecting the ranging results. At the same time, ambient light generated by sunlight and other laser emitting devices will also cause similar effects. Utility Model Content

[0004] The utility model aims to provide a laser receiving circuit, aiming to solve the problem that the traditional laser receiving circuit has signal saturation due to interference from ambient light or strong reflected light emitted by itself, thus affecting the distance measurement accuracy.

[0005] A first aspect of an embodiment of the utility model provides a laser receiving circuit, comprising:

[0006] an avalanche photodiode, configured to receive a laser pulse and output an avalanche current after being powered on;

[0007] a bias voltage generating circuit connected to the anode of the avalanche photodiode and configured to output a negative bias voltage to the avalanche photodiode, wherein the avalanche current is a negative current;

[0008] an amplifier circuit connected to the cathode of the avalanche photodiode and configured to amplify the avalanche current and output an amplified voltage echo signal;

[0009] The compensation circuit is respectively connected to the output end and the input end of the amplifier circuit, and is configured to compare the voltage echo signal with a first reference voltage, and output a compensation current to the input end of the amplifier circuit when the voltage echo signal is greater than the first reference voltage, so as to perform superimposed compensation for the avalanche current, and the compensation current is a positive current.

[0010] Optionally, the compensation circuit includes:

[0011] A filter circuit connected to the output end of the amplifier circuit, configured to filter the clutter signal in the voltage echo signal and output the filtered voltage echo signal;

[0012] an integration circuit connected to the filtering circuit and configured to compare the filtered voltage echo signal with the first reference voltage and convert it into a compensation voltage;

[0013] The voltage-to-current conversion circuit is connected to the output end of the integration circuit and the input end of the amplifier circuit, and is configured to convert the compensation voltage into the compensation current.

[0014] Optionally, the filtering circuit includes a first resistor and a first capacitor;

[0015] The first end of the first resistor is connected to the output end of the amplifier circuit, the second end of the first resistor and the first end of the first capacitor are connected together to form the output end of the filter circuit, and the second end of the first capacitor is grounded.

[0016] Optionally, the integration circuit includes a first comparator and a second capacitor;

[0017] The non-inverting input terminal of the first comparator constitutes the input terminal of the integration circuit, the inverting input terminal of the first comparator is connected to the first terminal of the second capacitor and is used to input the first reference voltage, and the output terminal of the comparator and the second terminal of the second capacitor are connected together to constitute the output terminal of the integration circuit.

[0018] Optionally, the voltage-current conversion circuit includes a second resistor;

[0019] The first end and the second end of the second resistor constitute the input end and the output end of the voltage-current conversion circuit respectively.

[0020] Optionally, the bias voltage generating circuit includes:

[0021] A power circuit is configured to output a negative voltage signal;

[0022] A switch circuit connected to the power supply circuit, triggered by a first switch signal to turn on and output the negative voltage signal, and triggered by a second switch signal to turn off and stop outputting the negative voltage signal;

[0023] An energy storage circuit is connected to the output end of the switch circuit and the anode of the avalanche photodiode, and is configured to receive the negative voltage signal to charge and store energy, and output a negative voltage to the avalanche photodiode;

[0024] A sampling circuit is connected to the energy storage circuit and the switching circuit, and is configured to sample the output voltage of the energy storage circuit, compare the sampled voltage sampling signal with a second reference voltage, and output the first switching signal or the second switching signal to adjust the output voltage of the energy storage circuit to be equal to the negative bias voltage.

[0025] Optionally, the switch circuit includes a first electronic switch tube, a second electronic switch tube, a third electronic switch tube, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a third capacitor;

[0026] The first end of the first electronic switch tube is grounded, and the control end of the first electronic switch tube constitutes the control end of the switch circuit. The second end of the first electronic switch tube, the first end of the third resistor and the first end of the fourth resistor are connected, the second end of the third resistor, the first end of the third capacitor and the first end of the second electronic switch tube are commonly connected and connected to a positive power supply, the second end of the third capacitor is grounded, the second end of the fourth resistor is connected to the control end of the second electronic switch tube, the second end of the second electronic switch tube, the control end of the third electronic switch tube and the first end of the fifth resistor are commonly connected, the second end of the fifth resistor, the first end of the third electronic switch tube and the first end of the sixth resistor are commonly connected, the second end of the sixth resistor constitutes the input end of the switch circuit, the second end of the third electronic switch tube and the first end of the seventh resistor are connected to constitute the output end of the switch circuit, the second end of the seventh resistor, the first end of the eighth resistor and the first end of the ninth resistor are commonly connected, the second end of the eighth resistor is connected to the sampling circuit, and the second end of the ninth resistor is grounded.

[0027] Optionally, the energy storage circuit includes a tenth resistor, a fourth capacitor, a fifth capacitor and a diode;

[0028] The first end of the fourth capacitor and the first end of the tenth resistor are connected together to form the input end of the energy storage circuit, the second end of the fourth capacitor is grounded, the second end of the tenth resistor, the first end of the fifth capacitor and the cathode of the diode are connected, the second end of the fifth capacitor is grounded, and the anode of the diode forms the input end of the energy storage circuit.

[0029] Optionally, the sampling circuit includes an eleventh resistor, a twelfth resistor, a thirteenth resistor, a sixth capacitor, a seventh capacitor, a second comparator and an inverter;

[0030] The input end of the inverter and the first end of the eleventh resistor are connected to form the input end of the sampling circuit, the output end of the inverter, the second end of the eleventh resistor and the non-inverting input end of the second comparator are connected, the inverting input end of the second comparator, the first end of the twelfth resistor and the first end of the thirteenth resistor are connected, the second end of the twelfth resistor is connected to the first end of the sixth capacitor, the second end of the sixth capacitor is connected to the output end of the second comparator to form the output end of the sampling circuit, the second end of the thirteenth resistor is connected to the first end of the seventh capacitor and is used to input the second reference voltage, and the second end of the seventh capacitor is grounded.

[0031] A second aspect of an embodiment of the utility model proposes a laser radar, comprising a laser transmitting circuit and the laser receiving circuit as described above.

[0032] Compared with the prior art, the embodiments of the utility model have the following beneficial effects: the above-mentioned laser receiving circuit includes an avalanche photodiode, a bias voltage generating circuit, an amplifying circuit and a compensation circuit; the avalanche photodiode performs photoelectric conversion on the received laser pulse under the drive of a negative bias voltage and generates an avalanche current; when receiving interference from ambient light or strong reflected light emitted by the laser transmitting circuit, the compensation circuit generates a compensation current that is antiphase to the avalanche current based on the voltage echo signal output by the amplifying circuit, reduces the input signal of the amplifying circuit, avoids saturation of the amplifying circuit, improves the dynamic range and receiving sensitivity of the amplifying circuit, and improves the ranging accuracy and environmental adaptability of the laser radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 A schematic diagram of the first structure of a laser receiving circuit provided by an embodiment of the utility model;

[0035] Figure 2 A second structural schematic diagram of a laser receiving circuit provided in an embodiment of the utility model;

[0036] Figure 3 A circuit diagram of an amplifier circuit and a compensation circuit provided in an embodiment of the utility model;

[0037] Figure 4 A circuit diagram of a switch circuit and an energy storage circuit provided in an embodiment of the utility model;

[0038] Figure 5 A circuit diagram of a sampling circuit provided by an embodiment of the utility model;

[0039] Figure 6 A schematic diagram of the structure of a laser radar provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present utility model, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] The first aspect of the embodiment of the utility model provides a laser receiving circuit 200, such as Figure 6 As shown, the laser receiving circuit 200 is arranged correspondingly to the laser emitting circuit 100. The laser emitting circuit 100 can select the corresponding laser emitting component and laser driving circuit. The laser emitting component is used to receive electricity and emit laser signals. The laser driving circuit is connected to the laser emitting component and is used to trigger the output of driving power to the laser emitting component according to the driving signal. The laser driving circuit can select a charging and discharging circuit of a corresponding structure. The charging and discharging circuit charges and discharges according to the received driving signal, and controls the laser emitting component to emit laser pulses at a corresponding angle according to the corresponding timing.

[0043] The laser receiving circuit 200 is used to receive the laser pulse emitted by the laser emitting circuit 100 and convert it into a voltage echo signal SIGNAL. The voltage echo signal SIGNAL is output to the back-end processing circuit or controller, and the processing circuit or controller determines the distance information and reflectivity of the object to be measured 1 according to the voltage echo signal SIGNAL.

[0044] In order to avoid the interference of strong reflected light from the ambient light or the laser emitting circuit 100, which may cause the saturation of the amplifier circuit 30, reduce the ranging accuracy and affect the sensitivity of the laser radar, in this embodiment, Figure 1 As shown, the laser receiving circuit 200 includes:

[0045] The avalanche photodiode 10 is configured to receive laser pulses and output avalanche current after being powered on;

[0046] The bias voltage generating circuit 20 is connected to the anode of the avalanche photodiode 10 and is configured to output a negative bias voltage APD_HV to the avalanche photodiode 10, and the avalanche current is a negative current;

[0047] The amplifier circuit 30 is connected to the cathode of the avalanche photodiode 10 and is configured to amplify the avalanche current and output the amplified voltage echo signal SIGNAL;

[0048] The compensation circuit 40 is respectively connected to the output end and the input end of the amplifier circuit 30, and is configured to compare the voltage echo signal SIGNAL with the first reference voltage VREF1, and output a compensation current to the input end of the amplifier circuit 30 when the voltage echo signal SIGNAL is greater than the first reference voltage VREF1, so as to perform superimposed compensation for the avalanche current, and the compensation current is a positive current.

[0049] In this embodiment, the bias voltage generating circuit 20 is used to generate a negative bias voltage APD_HV that meets the working requirements of the avalanche photodiode 10. The avalanche photodiode 10 avalanches and breaks down under the drive of the negative bias voltage APD_HV, and converts the received light signal into an avalanche current, wherein the avalanche current is a negative current signal, which can be a negative current pulse signal or a negative continuous current signal. For example, when receiving a laser pulse with an intensity less than a preset intensity, the avalanche photodiode 10 generates an avalanche effect, performs photoelectric conversion on the laser pulse, and outputs a current pulse signal, or, when receiving ambient light with an intensity greater than a preset light intensity, the avalanche photodiode 10 performs photoelectric conversion on the received ambient light, and outputs a continuous current signal.

[0050] After the avalanche current is amplified by the amplifier circuit 30, a voltage echo signal SIGNAL of a positive voltage is output. When the laser emitted by the laser radar itself irradiates an object with a high reflectivity at a close distance or strong ambient light, the avalanche current output by the avalanche photodiode 10 becomes larger. Correspondingly, the voltage echo signal SIGNAL output by the amplifier circuit 30 exceeds the threshold, resulting in signal saturation. At this time, the compensation circuit 40 obtains the voltage echo signal SIGNAL of the amplifier circuit 30, and converts the voltage echo signal SIGNAL into a compensation current, and feeds the compensation current back to the output end of the amplifier circuit 30. The compensation current is a positive current. The positive current compensation current is superimposed and compensated with the negative current avalanche current to offset part of the avalanche current, thereby reducing the input signal of the amplifier circuit 30, avoiding saturation of the amplifier circuit 30, improving the dynamic range and receiving sensitivity of the amplifier circuit 30, and improving the ranging accuracy and environmental adaptability of the laser radar.

[0051] Among them, the compensation current is positively correlated with the absolute value of the avalanche current, that is, when the absolute value of the avalanche current is larger, the compensation current is larger, and when the absolute value of the avalanche current is smaller, the compensation current is smaller, and the effective current after the superposition of the compensation current and the avalanche current is less than or equal to the critical threshold of the input signal of the amplifier circuit 30, wherein the critical threshold of the input signal of the amplifier circuit 30 means that when the input current signal is less than or equal to the critical threshold, the output signal of the amplifier circuit 30 is unsaturated, and when the input current signal is greater than the critical threshold, the output signal of the amplifier circuit 30 is saturated.

[0052] The compensation circuit 40 compares the voltage echo signal SIGNAL with a preset value and outputs a compensation current of a corresponding magnitude to compensate for the avalanche current, thereby reducing and offsetting part of the avalanche current, thereby reducing the input signal of the amplifier circuit 30 and avoiding saturation of the amplifier circuit 30.

[0053] Similarly, when the laser receiving circuit 200 does not receive interference from ambient light or strong reflected light emitted by the laser emitting circuit 100, the avalanche current generated by the avalanche photodiode 10 is less than the critical threshold of the input signal of the amplifier circuit 30, and the amplifier circuit 30 is not saturated. At this time, the compensation circuit 40 does not output the compensation current, and the input signal of the amplifier circuit 30 is the avalanche current generated by the avalanche photodiode 10.

[0054] The compensation circuit 40 may adopt a corresponding comparison circuit, a signal conversion circuit, etc. In an optional embodiment, as shown in FIG. Figure 2 As shown, the compensation circuit 40 includes:

[0055] The filter circuit 41 is connected to the output end of the amplifier circuit 30 and is configured to filter the clutter signal in the voltage echo signal SIGNAL and output the filtered voltage echo signal SIGNAL;

[0056] The integration circuit 42 is connected to the filter circuit 41 and is configured to compare the filtered voltage echo signal SIGNAL with the first reference voltage VREF1 and convert it into a compensation voltage;

[0057] The voltage-to-current conversion circuit 43 is connected to the output terminal of the integration circuit 42 and the input terminal of the amplifier circuit 30 , and is configured to convert the compensation voltage into a compensation current.

[0058] In this embodiment, the filter circuit 41 is used to implement a filtering function to filter the clutter signal mixed in the voltage echo signal SIGNAL to prevent the clutter signal from interfering with subsequent signal comparison and conversion, resulting in errors in the output compensation current.

[0059] When the laser emitted by the laser radar itself irradiates an object with high reflectivity at a close distance or strong ambient light, the avalanche current output by the avalanche photodiode 10 becomes larger. Correspondingly, the voltage echo signal SIGNAL output by the amplifier circuit 30 exceeds the threshold, resulting in signal saturation. At this time, the integration circuit 42 obtains the voltage echo signal SIGNAL of the amplifier circuit 30 through the filter circuit 41, and converts the voltage echo signal SIGNAL into a compensation voltage. Then, the voltage-current conversion circuit 43 converts the compensation voltage into a compensation current, and the compensation current is fed back to the output end of the amplifier circuit 30. The compensation current is a positive current. The compensation current of the positive current is superimposed and compensated with the avalanche current of the negative current to offset part of the avalanche current, thereby reducing the input signal of the amplifier circuit 30, avoiding saturation of the amplifier circuit 30, improving the dynamic range and receiving sensitivity of the amplifier circuit 30, and improving the ranging accuracy and environmental adaptability of the laser radar.

[0060] Among them, the compensation voltage changes in a positive correlation with the voltage echo signal SIGNAL, and the compensation current changes in a positive correlation with the compensation voltage, that is, when the absolute value of the avalanche current is larger, the voltage echo signal SIGNAL is larger, the difference between the voltage echo signal SIGNAL and the first reference voltage VREF1 is larger, the compensation voltage is larger, and correspondingly, the compensation current is larger; and when the absolute value of the avalanche current is smaller, the voltage echo signal SIGNAL is smaller, the difference between the voltage echo signal SIGNAL and the first reference voltage VREF1 is smaller, the compensation voltage is smaller, and correspondingly, the compensation current is smaller.

[0061] When the avalanche current does not exceed the critical threshold of the input signal of the amplifier circuit 30, the amplifier circuit 30 is not saturated, and when the voltage echo signal SIGNAL is equal to the first reference voltage VREF1, the compensation voltage is zero, and correspondingly, the compensation current is zero. At this time, no current compensation is performed.

[0062] The integration circuit 42 compares the voltage echo signal SIGNAL with the first reference voltage VREF1 and outputs a compensation voltage of corresponding magnitude, and converts the avalanche current with positive correlation variation generated by the voltage-to-current conversion circuit 43 for compensation, thereby reducing and offsetting part of the avalanche current, thereby reducing the input signal of the amplifier circuit 30 and avoiding saturation of the amplifier circuit 30.

[0063] That is, when the laser receiving circuit 200 does not receive interference from ambient light or strong reflected light emitted by the laser emitting circuit 100, the avalanche current generated by the avalanche photodiode 10 is less than the critical threshold of the input signal of the amplifier circuit 30, and the amplifier circuit 30 is not saturated. At this time, the integration circuit 42 does not output a compensation voltage, and the voltage-current conversion circuit 43 has no compensation current output. The input signal of the amplifier circuit 30 is the avalanche current generated by the avalanche photodiode 10.

[0064] The filter circuit 41 may adopt corresponding filter capacitors, optical couplers, etc., the integration circuit 42 may adopt corresponding comparator structures, and the voltage-current conversion circuit 43 may adopt corresponding resistors, electronic switch tubes, etc. In an optional embodiment, as Figure 3 As shown, the filter circuit 41 includes a first resistor R1 and a first capacitor C1;

[0065] The first end of the first resistor R1 is connected to the output end of the amplifier circuit 30 , the second end of the first resistor R1 and the first end of the first capacitor C1 are connected together to form the output end of the filter circuit 41 , and the second end of the first capacitor C1 is grounded.

[0066] The integration circuit 42 includes a first comparator U2 and a second capacitor C2;

[0067] The positive input terminal of the first comparator U2 constitutes the input terminal of the integration circuit 42, the negative input terminal of the first comparator U2 is connected to the first terminal of the second capacitor C2 and is used to input the first reference voltage VREF1, and the output terminal of the comparator and the second terminal of the second capacitor C2 are connected together to form the output terminal of the integration circuit 42.

[0068] The voltage-current conversion circuit 43 includes a second resistor R2;

[0069] The first end and the second end of the second resistor R2 constitute the input end and the output end of the voltage-current conversion circuit 43 respectively.

[0070] The amplification circuit 30 includes a signal amplifier U1, which can be a transimpedance amplifier or an operational amplifier. The input end of the signal amplifier U1 is connected to the cathode of the avalanche photodiode 10 through the eighth capacitor C8, and the avalanche current generated by the avalanche photodiode 10 is converted into a voltage echo signal SIGNAL, and outputted through the output end. The first resistor R1 in the filtering circuit 41 is directly connected to the output end of the signal amplifier U1 or through the eighteenth resistor and the nineteenth resistor, and the voltage echo signal SIGNAL is filtered.

[0071] When the laser emitted by the laser radar itself irradiates an object with high reflectivity at a close distance or strong ambient light, the avalanche current output by the avalanche photodiode 10 becomes larger. Correspondingly, the voltage echo signal SIGNAL output by the amplifier circuit 30 exceeds the threshold, resulting in signal saturation. At this time, the filtered voltage echo signal SIGNAL is output to the positive input terminal of the first comparator U2 in the integration circuit 42, and the voltage echo signal SIGNAL is compared with the first reference voltage VREF1 input to the inverting input terminal of the first comparator U2. The comparison signal of the corresponding size of the first comparator U2 is the compensation voltage. Then, the second resistor R2 of the voltage-current conversion circuit 43 converts the compensation voltage into a compensation current, and the compensation current is fed back to the output terminal of the amplifier circuit 30. The compensation current of the positive current is superimposed and compensated with the avalanche current of the negative current to offset part of the avalanche current, thereby reducing the input signal of the amplifier circuit 30, avoiding saturation of the amplifier circuit 30, improving the dynamic range and receiving sensitivity of the amplifier circuit 30, and improving the ranging accuracy and environmental adaptability of the laser radar.

[0072] When the avalanche current does not exceed the critical threshold of the input signal of the amplifier circuit 30, the amplifier circuit 30 is not saturated, and the voltage echo signal SIGNAL is equal to the first reference voltage VREF1, the first comparator U2 does not output the compensation voltage, and correspondingly, the compensation current is zero. At this time, no current compensation is performed.

[0073] That is, when the laser receiving circuit 200 does not receive the interference of the ambient light or the strong reflected light emitted by the laser emitting circuit 100, the avalanche current generated by the avalanche photodiode 10 is less than the critical threshold of the input signal of the amplifier circuit 30, and the amplifier circuit 30 is not saturated. At this time, the first comparator U2 does not output the compensation voltage, and the second resistor R2 has no compensation current output. The input signal of the amplifier circuit 30 is the avalanche current generated by the avalanche photodiode 10.

[0074] The bias voltage generating circuit 20 may adopt a corresponding voltage source, a power conversion circuit, etc. In an optional embodiment, as shown in FIG. Figure 2 As shown, the bias voltage generating circuit 20 includes:

[0075] The power supply circuit 21 is configured to output a negative voltage signal;

[0076] The switch circuit 22 is connected to the power supply circuit 21, and is triggered by the first switch signal to turn on and output a negative voltage signal, and is triggered by the second switch signal to turn off and stop outputting the negative voltage signal;

[0077] The energy storage circuit 23 is connected to the output end of the switch circuit 22 and the anode of the avalanche photodiode 10, and is configured to receive a negative voltage signal to charge and store energy, and output a negative voltage to the avalanche photodiode 10;

[0078] The sampling circuit 24 is connected to the energy storage circuit 23 and the switching circuit 22, and is configured to sample the output voltage of the energy storage circuit 23, compare the sampled voltage sampling signal SAMPLE with the second reference voltage VREF2, and output a first switching signal or a second switching signal to adjust the output voltage of the energy storage circuit 23 to be equal to the negative bias voltage APD_HV.

[0079] In this embodiment, the switch circuit 22 is turned on and off according to the switch signal output by the sampling circuit 24 , and charges the energy storage circuit 23 or cuts off the charging and energy storage.

[0080] During specific operation, the sampling circuit 24 samples the output voltage of the energy storage circuit 23 and compares it with the second reference voltage VREF2. During initial charging, the voltage sampling signal SAMPLE corresponding to the output voltage of the energy storage circuit 23 is less than the second reference voltage VREF2, indicating that the output voltage of the energy storage circuit 23 has not reached the negative bias voltage APD_HV required for the avalanche photodiode 10 to work. The sampling circuit 24 outputs a first switching signal, the switching circuit 22 is turned on, and the negative voltage signal output by the power supply circuit 21 charges and stores energy in the energy storage circuit 23 until the output voltage of the energy storage circuit 23 reaches the negative bias voltage APD_HV. The sampling circuit 24 outputs a second switching signal to control the switching circuit 22 to turn off, so that the energy storage circuit 23 stops charging and storing energy.

[0081] Alternatively, when the voltage sampling signal SAMPLE corresponding to the output voltage of the energy storage circuit 23 is greater than the second reference voltage VREF2 during the charging process, it indicates that the output voltage of the energy storage circuit 23 is too large and exceeds the negative bias voltage APD_HV required for the avalanche photodiode 10 to work. At this time, the sampling circuit 24 outputs the second switch signal to control the switch circuit 22 to turn off, so that the energy storage circuit 23 stops charging and storing energy, and after the energy storage circuit 23 discharges for a preset period of time, when the output voltage of the energy storage circuit 23 drops to a preset voltage, the first switch signal is re-output to control the switch circuit 22 to turn on, and charging continues, thereby realizing the charge and discharge control of the energy storage circuit 23, so that its output voltage is stabilized at the negative bias voltage APD_HV required for the avalanche photodiode 10 to work.

[0082] Among them, the switch circuit 22 can adopt a switch device with controlled on and off or a plurality of switch structures, the power supply circuit 21 can adopt a boost circuit, a buck circuit and other structures, and the energy storage circuit 23 can adopt an energy storage battery, an energy storage capacitor and other structures. In order to simplify the circuit structure and reduce the design cost, in an optional embodiment, as Figure 5As shown, the switch circuit 22 includes a first electronic switch tube Q1, a second electronic switch tube Q2, a third electronic switch tube Q3, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9 and a third capacitor C3;

[0083] The first end of the first electronic switch tube Q1 is grounded, and the control end of the first electronic switch tube Q1 constitutes the control end of the switch circuit 22. The second end of the first electronic switch tube Q1, the first end of the third resistor R3 and the first end of the fourth resistor R4 are connected. The second end of the third resistor R3, the first end of the third capacitor C3 and the first end of the second electronic switch tube Q2 are connected in common and connected to the positive power supply. The second end of the third capacitor C3 is grounded. The second end of the fourth resistor R4 is connected to the control end of the second electronic switch tube Q2. The second end of the second electronic switch tube Q2, the control end of the third electronic switch tube Q3 and the first end of the fifth resistor R5 are connected in common. The second end of the fifth resistor R5, the first end of the third electronic switch tube Q3 and the first end of the sixth resistor R6 are connected in common. The second end of the sixth resistor R6 constitutes the input end of the switch circuit 22. The second end of the third electronic switch tube Q3 and the first end of the seventh resistor R7 are connected to constitute the output end of the switch circuit 22. The second end of the seventh resistor R7, the first end of the eighth resistor R8 and the first end of the ninth resistor R9 are connected in common. The second end of the eighth resistor R8 is connected to the sampling circuit 24, and the second end of the ninth resistor R9 is grounded.

[0084] The energy storage circuit 23 includes a tenth resistor R10, a fourth capacitor C4, a fifth capacitor C5 and a diode D1;

[0085] The first end of the fourth capacitor C4 and the first end of the tenth resistor R10 are connected together to form the input end of the energy storage circuit 23, the second end of the fourth capacitor C4 is grounded, the second end of the tenth resistor R10, the first end of the fifth capacitor C5 and the cathode of the diode D1 are connected, the second end of the fifth capacitor C5 is grounded, and the anode of the diode D1 forms the input end of the energy storage circuit 23.

[0086] In this embodiment, the first electronic switch tube Q1 receives the switch signal output by the sampling circuit 24. When the voltage sampling signal SAMPLE corresponding to the output voltage of the energy storage circuit 23 is less than the second reference voltage VREF2, it indicates that the output voltage of the energy storage circuit 23 does not reach the negative bias voltage APD_HV required for the avalanche photodiode 10 to work. The sampling circuit 24 outputs the first switch signal. When the first switch signal is received, the first electronic switch tube Q1 is turned off, the second electronic switch tube Q2 receives a high level, and the second electronic switch tube Q2 is turned off. At the same time, the third electronic switch tube Q3 receives a low-level negative voltage signal through the second electronic switch tube Q2, and the third electronic switch tube Q3 is controlled to be turned on. The negative voltage signal input by the power supply circuit 21 is output to the energy storage circuit 23 through the third electronic switch tube Q3. The fourth capacitor C4 and the fifth capacitor C5 of the energy storage circuit 23 are charged and stored. The terminal voltage of the fifth capacitor C5 is the output voltage of the energy storage circuit 23, and the output voltage is output to the avalanche photodiode 10 through the diode D1.

[0087] And when the voltage sampling signal SAMPLE corresponding to the output voltage of the energy storage circuit 23 is greater than the second reference voltage VREF2, it indicates that the output voltage of the energy storage circuit 23 exceeds the negative bias voltage APD_HV required for the avalanche photodiode 10 to work, and the sampling circuit 24 outputs a second switching signal. When the first electronic switch tube Q1 receives the second switching signal, the first electronic switch tube Q1 is turned on, the second electronic switch tube Q2 receives a low level and is controlled to be turned on, and the third electronic switch tube Q3 receives a high level and is controlled to be turned off. At this time, the negative voltage signal input by the power supply circuit 21 is cut off from being output to the energy storage circuit 23, and the energy storage circuit 23 cuts off charging.

[0088] The sampling circuit 24 indirectly samples the output voltage of the energy storage circuit 23 through the tenth resistor R10, the fourth capacitor C4, the seventh resistor R7 and the ninth resistor R9.

[0089] The sampling circuit 24 may be a comparator or the like. In an optional embodiment, Figure 6 As shown, the sampling circuit 24 includes an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a sixth capacitor C6, a seventh capacitor C7, a second comparator U4 and an inverter U3;

[0090] The input end of the inverter U3 and the first end of the eleventh resistor R11 are connected to form the input end of the sampling circuit 24, the output end of the inverter U3, the second end of the eleventh resistor R11 and the non-inverting input end of the second comparator U4 are connected, the inverting input end of the second comparator U4, the first end of the twelfth resistor R12 and the first end of the thirteenth resistor R13 are connected, the second end of the twelfth resistor R12 and the first end of the sixth capacitor C6 are connected, the second end of the sixth capacitor C6 and the output end of the second comparator U4 are connected to form the output end of the sampling circuit 24, the second end of the thirteenth resistor R13 and the first end of the seventh capacitor C7 are connected and used to input the second reference voltage VREF2, and the second end of the seventh capacitor C7 is grounded.

[0091] In this embodiment, since the terminal voltages of the fourth capacitor C4 and the fifth capacitor C5 are negative voltages, in order to achieve voltage comparison of the same polarity, the voltage sampling signal SAMPLE output by the eighth resistor R8 is first inverted by the inverter U3, and the positive-phase voltage sampling signal SAMPLE is output to the positive-phase input terminal of the second comparator U4. The second reference voltage VREF2 is output to the inverting input terminal of the second comparator U4 after being divided by the thirteenth resistor R13 and the twelfth resistor R12, and is compared with the positive-phase voltage sampling signal SAMPLE.

[0092] When the positive-phase voltage sampling signal SAMPLE corresponding to the output voltage of the energy storage circuit 23 is less than the second reference voltage VREF2, it indicates that the output voltage of the energy storage circuit 23 has not reached the negative bias voltage APD_HV required for the avalanche photodiode 10 to work, and the sampling circuit 24 outputs a first switching signal of a low-level signal. When the first switching signal is received, the switch circuit 22 is controlled to be turned on, and the negative voltage signal input by the power supply circuit 21 is output to the energy storage circuit 23 through the third electronic switch tube Q3. The energy storage circuit 23 is charged and stores energy, and the output voltage of the energy storage circuit 23 is output to the avalanche photodiode 10 through the diode D1.

[0093] When the positive-phase voltage sampling signal SAMPLE corresponding to the output voltage of the energy storage circuit 23 is greater than the second reference voltage VREF2, it indicates that the output voltage of the energy storage circuit 23 exceeds the negative bias voltage APD_HV required for the avalanche photodiode 10 to work, and the sampling circuit 24 outputs a high-level second switching signal, and the switch circuit 22 is controlled to be turned off. At this time, the negative voltage signal input by the power supply circuit 21 is cut off from being output to the energy storage circuit 23, and the energy storage circuit 23 stops charging.

[0094] Corresponding to the type of the switch signal output by the sampling circuit 24, in an optional embodiment, the first electronic switch tube Q1 is an NMOS tube or an NPN transistor, and the second electronic switch tube Q2 and the third electronic switch tube Q3 are PMOS tubes or PNP transistors.

[0095] Compared with the prior art, the embodiments of the utility model have the following beneficial effects: the above-mentioned laser receiving circuit 200 includes an avalanche photodiode 10, a bias voltage generating circuit 20, an amplifier circuit 30 and a compensation circuit 40. The avalanche photodiode 10 performs photoelectric conversion on the received laser pulse under the drive of the negative bias voltage APD_HV and generates an avalanche current. When receiving interference from ambient light or strong reflected light emitted by the laser transmitting circuit 100, the compensation circuit 40 generates a compensation current that is antiphase to the avalanche current based on the voltage echo signal SIGNAL output by the amplifier circuit 30, reduces the input signal of the amplifier circuit 30, avoids saturation of the amplifier circuit 30, improves the dynamic range and receiving sensitivity of the amplifier circuit 30, and improves the ranging accuracy and environmental adaptability of the laser radar.

[0096] The utility model also proposes a laser radar, such as Figure 6 As shown, the laser radar includes a laser transmitting circuit 100 and a laser receiving circuit 200. The specific structure of the laser receiving circuit 200 refers to the above embodiment. Since the laser radar adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0097] Among them, the laser receiving circuit 200 is arranged corresponding to the laser transmitting circuit 100. The laser transmitting circuit 100 transmits a laser pulse to the object to be tested 1, and the laser pulse reflected from the object to be tested 1 is output to the laser receiving circuit 200. The laser receiving circuit 200 converts the laser pulse signal into a voltage echo signal SIGNAL after photoelectric conversion, DC isolation processing and transimpedance amplification. The laser receiving circuit 200 also includes a processing circuit. The processing circuit can also further amplify, detect and process the voltage echo signal SIGNAL, and determine the distance information and / or reflectivity based on the processed voltage echo signal SIGNAL. At the same time, the processing circuit can also be used to output the first reference voltage and the second reference voltage mentioned above.

[0098] In an optional embodiment, the laser emitting circuit 100 includes a laser emitting component and a laser driving circuit. The laser emitting component can use a corresponding laser. The laser is configured to emit laser pulses upon power reception. The laser driving circuit is connected to the laser and is used to trigger the output of driving power to the laser according to a driving signal.

[0099] The laser driving circuit can select a charging and discharging circuit of a corresponding structure, and the charging and discharging circuit performs charging and discharging according to the received driving signal, and controls the laser to emit laser pulses at a corresponding angle according to a corresponding timing.

[0100] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A laser receiving circuit, characterized in that: include: an avalanche photodiode, configured to receive a laser pulse and output an avalanche current after being powered on; a bias voltage generating circuit connected to the anode of the avalanche photodiode and configured to output a negative bias voltage to the avalanche photodiode, wherein the avalanche current is a negative current; an amplifier circuit connected to the cathode of the avalanche photodiode and configured to amplify the avalanche current and output an amplified voltage echo signal; The compensation circuit is respectively connected to the output end and the input end of the amplifier circuit, and is configured to compare the voltage echo signal with a first reference voltage, and output a compensation current to the input end of the amplifier circuit when the voltage echo signal is greater than the first reference voltage, so as to perform superimposed compensation for the avalanche current, and the compensation current is a positive current.

2. The laser receiving circuit according to claim 1, characterized in that: The compensation circuit comprises: A filter circuit connected to the output end of the amplifier circuit, configured to filter the clutter signal in the voltage echo signal and output the filtered voltage echo signal; an integration circuit connected to the filtering circuit and configured to compare the filtered voltage echo signal with the first reference voltage and convert it into a compensation voltage; The voltage-to-current conversion circuit is connected to the output end of the integration circuit and the input end of the amplifier circuit, and is configured to convert the compensation voltage into the compensation current.

3. The laser receiving circuit according to claim 2, characterized in that: The filter circuit includes a first resistor and a first capacitor; The first end of the first resistor is connected to the output end of the amplifier circuit, the second end of the first resistor and the first end of the first capacitor are connected together to form the output end of the filter circuit, and the second end of the first capacitor is grounded.

4. The laser receiving circuit according to claim 2, characterized in that: The integration circuit includes a first comparator and a second capacitor; The non-inverting input terminal of the first comparator constitutes the input terminal of the integration circuit, the inverting input terminal of the first comparator is connected to the first terminal of the second capacitor and is used to input the first reference voltage, and the output terminal of the comparator and the second terminal of the second capacitor are connected together to constitute the output terminal of the integration circuit.

5. The laser receiving circuit according to claim 2, characterized in that: The voltage-current conversion circuit includes a second resistor; The first end and the second end of the second resistor constitute the input end and the output end of the voltage-current conversion circuit respectively.

6. The laser receiving circuit according to claim 1, characterized in that: The bias voltage generating circuit comprises: A power circuit configured to output a negative voltage signal; A switch circuit connected to the power supply circuit, triggered by a first switch signal to turn on and output the negative voltage signal, and triggered by a second switch signal to turn off and stop outputting the negative voltage signal; An energy storage circuit is connected to the output end of the switch circuit and the anode of the avalanche photodiode, and is configured to receive the negative voltage signal to charge and store energy, and output a negative voltage to the avalanche photodiode; A sampling circuit is connected to the energy storage circuit and the switching circuit, and is configured to sample the output voltage of the energy storage circuit, compare the sampled voltage sampling signal with a second reference voltage, and output the first switching signal or the second switching signal to adjust the output voltage of the energy storage circuit to be equal to the negative bias voltage.

7. The laser receiving circuit according to claim 6, characterized in that: The switch circuit includes a first electronic switch tube, a second electronic switch tube, a third electronic switch tube, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a third capacitor; The first end of the first electronic switch tube is grounded, and the control end of the first electronic switch tube constitutes the control end of the switch circuit. The second end of the first electronic switch tube, the first end of the third resistor and the first end of the fourth resistor are connected, the second end of the third resistor, the first end of the third capacitor and the first end of the second electronic switch tube are commonly connected and connected to a positive power supply, the second end of the third capacitor is grounded, the second end of the fourth resistor is connected to the control end of the second electronic switch tube, the second end of the second electronic switch tube, the control end of the third electronic switch tube and the first end of the fifth resistor are commonly connected, the second end of the fifth resistor, the first end of the third electronic switch tube and the first end of the sixth resistor are commonly connected, the second end of the sixth resistor constitutes the input end of the switch circuit, the second end of the third electronic switch tube and the first end of the seventh resistor are connected to constitute the output end of the switch circuit, the second end of the seventh resistor, the first end of the eighth resistor and the first end of the ninth resistor are commonly connected, the second end of the eighth resistor is connected to the sampling circuit, and the second end of the ninth resistor is grounded.

8. The laser receiving circuit according to claim 6, characterized in that: The energy storage circuit includes a tenth resistor, a fourth capacitor, a fifth capacitor and a diode; The first end of the fourth capacitor and the first end of the tenth resistor are connected together to form the input end of the energy storage circuit, the second end of the fourth capacitor is grounded, the second end of the tenth resistor, the first end of the fifth capacitor and the cathode of the diode are connected, the second end of the fifth capacitor is grounded, and the anode of the diode forms the input end of the energy storage circuit.

9. The laser receiving circuit according to claim 6, characterized in that: The sampling circuit includes an eleventh resistor, a twelfth resistor, a thirteenth resistor, a sixth capacitor, a seventh capacitor, a second comparator and an inverter; The input end of the inverter and the first end of the eleventh resistor are connected to form the input end of the sampling circuit, the output end of the inverter, the second end of the eleventh resistor and the non-inverting input end of the second comparator are connected, the inverting input end of the second comparator, the first end of the twelfth resistor and the first end of the thirteenth resistor are connected, the second end of the twelfth resistor is connected to the first end of the sixth capacitor, the second end of the sixth capacitor is connected to the output end of the second comparator to form the output end of the sampling circuit, the second end of the thirteenth resistor is connected to the first end of the seventh capacitor and is used to input the second reference voltage, and the second end of the seventh capacitor is grounded.

10. A laser radar, characterized in that: The invention comprises a laser transmitting circuit and a laser receiving circuit as claimed in any one of claims 1 to 9.

Images