Leakage circuit and laser radar

Abstract

The embodiment of the utility model provides a bleeder circuit and a laser radar. The bleeder circuit comprises an avalanche photodiode, a shunt module, a switch module and a load circuit. According to the technical scheme, when the light energy is strong and the current generated by the avalanche photodiode exceeds the current generated by the avalanche photodiode in the micro-saturation state, the voltage output to the switch module meets the breakover voltage of the switch module, and the switch module is conducted to discharge the redundant current to the ground until the bottom noise does not bulge; the problem that a signal output to a load circuit fluctuates greatly to generate bottom noise protrusions due to the fact that the avalanche photodiode generates large current due to strong illumination is solved. And meanwhile, when the switch module is not switched on, the current is normally output to the load circuit, so that the small signal is prevented from being discharged, and the quality of the small signal is improved.

Description

Technical Field

[0001] The embodiments of the utility model relate to the technical field of electronic circuits, and in particular to a discharge circuit and a laser radar. Background Art

[0002] LiDAR is a radar system that emits laser beams to detect the position, speed and other characteristic quantities of a target. In actual application scenarios, LiDAR is required to be able to identify the reflectivity of point clouds, high reflection, and low reflection signal strength to identify close-range objects. At present, the methods used to improve the effect of LiDAR point cloud images include: 1. Software adjustment of APD high voltage; 2. Adjustment of the receiving circuit amplification parameters. However, both of the above methods are prone to problems such as signal supersaturation, and some pulse widths are too narrow, and the energy is obviously insufficient, and some reflectivity is prone to low, high reflection shortcomings and other problems.

[0003] To address the signal over-saturation problem, existing technologies often use diode discharge circuits to discharge excess light energy to achieve a slightly saturated state. However, at the same time, small signals are also discharged, which reduces the energy for identifying low-reflective objects. Low-reflective objects with low reflectivity cannot be identified. In addition, the junction capacitance of the diode is too large, the pulse width is too wide, and the software judgment time cannot recover, resulting in a drag phenomenon. Utility Model Content

[0004] The utility model provides a discharge circuit and a laser radar, so that when the current exceeds a threshold value due to signal supersaturation, a switch module is turned on to discharge the excess current; and when the current is lower than the threshold value, the switch module is turned off to prevent small signals from being discharged.

[0005] In a first aspect, an embodiment of the utility model provides a discharge circuit, including an avalanche photodiode, a shunt module, a switch module and a load circuit;

[0006] One end of the avalanche photodiode is connected to an external power supply, and the other end is respectively connected to the input end of the shunt module and the first end of the switch module; the second output end of the shunt module is connected to the control end of the switch module; the second end of the switch module is grounded; the first output end of the shunt module is connected to the load circuit;

[0007] When the current generated by the avalanche photodiode exceeds the preset current value, the voltage at the second output end of the shunt module satisfies the turn-on voltage of the switch module, so that the switch module is turned on, so as to discharge the current output through the second output end of the shunt module to the ground through the second end of the switch module, so that the current output from the first output end of the shunt module is equal to the preset current value;

[0008] When the current generated by the avalanche photodiode does not exceed the preset current value, the voltage at the second output end of the shunt module does not meet the turn-on voltage of the switch module, the switch module is not turned on, and the current output through the first output end of the shunt module is equal to the current generated by the avalanche photodiode.

[0009] Optionally, the shunt module includes a first shunt resistor and a second shunt resistor; the resistance of the first shunt resistor is greater than the resistance of the second shunt resistor;

[0010] One end of the first shunt resistor is connected to the other end of the avalanche photodiode as the input end of the shunt module; the other end of the first shunt resistor is respectively connected to one end of the second shunt resistor and the load circuit; the other end of the second shunt resistor is connected to the control end of the switch module.

[0011] Optionally, the switch module includes a transistor; the first pole of the transistor serves as the first end of the switch module and the input end of the shunt module; the second pole of the transistor serves as the second end of the switch module and is grounded; and the base of the transistor serves as the control end of the switch module and is connected to the first output end of the shunt module.

[0012] Optionally, the shunt module further includes a third shunt resistor; one end of the third shunt resistor is connected to the second end of the switch module, and the other end is grounded.

[0013] Optionally, a filter module is further included, one end of the filter module is connected to the external power supply, and the other end of the filter module is connected to one end of the avalanche photodiode.

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

[0015] One end of the first filter resistor is connected to the external power supply, and the other end is respectively connected to one end of the avalanche photodiode and one end of the capacitor; the other end of the capacitor is grounded.

[0016] Optionally, the load circuit includes a filtering unit and an amplifying unit; the input end of the filtering unit is connected to the first output end of the shunt module; and the output end of the filtering unit is connected to the input end of the amplifying unit.

[0017] Optionally, the amplification unit includes a transimpedance amplifier; the non-inverting input terminal of the transimpedance amplifier is connected to the output terminal of the filtering unit as the input terminal of the amplification unit; the inverting input terminal of the transimpedance amplifier is respectively connected to one end of a first voltage-dividing resistor and a second voltage-dividing resistor; the other end of the second voltage-dividing resistor is connected to the output terminal of the transimpedance amplifier; the other end of the first voltage-dividing resistor is grounded; the positive terminal of the transimpedance amplifier is connected to an external positive power supply; and the negative terminal of the transimpedance amplifier is connected to an external negative power supply.

[0018] Optionally, the filtering unit includes a second filtering resistor and a second capacitor;

[0019] One end of the second filter resistor is connected to the output end of the shunt module, and the other end is connected to one end of the second capacitor; the other end of the second capacitor is connected to the input end of the amplification unit.

[0020] In a second aspect, an embodiment of the utility model further provides a laser radar, comprising a discharge circuit as described in the first aspect.

[0021] The utility model provides a discharge circuit and a laser radar, wherein the discharge circuit comprises an avalanche photodiode, a shunt module, a switch module and a load circuit; one end of the avalanche photodiode is connected to an external power supply, and the other end is respectively connected to an input end of the shunt module and a first end of the switch module; a second output end of the shunt module is connected to a control end of the switch module; a second end of the switch module is grounded; and the first output end of the shunt module is connected to the load circuit; when the current generated by the avalanche photodiode exceeds a preset current value, a voltage at the second output end of the shunt module satisfies a turn-on voltage of the switch module, so that the switch module is turned on, so as to discharge the current outputted through the second output end of the shunt module to the ground through the second end of the switch module, so that the current outputted from the first output end of the shunt module is equal to the preset current value ... When the current generated does not exceed the preset current value, the voltage at the second output end of the shunt module does not meet the turn-on voltage of the switch module, the switch module is not turned on, and the current output through the first output end of the shunt module is equal to the current generated by the avalanche photodiode; the above technical scheme, when the light energy is strong and the current generated by the avalanche photodiode exceeds the current of the avalanche photodiode in a slightly saturated state, the voltage output to the switch module meets its turn-on voltage, the switch module is turned on to discharge the excess current to the ground until the background noise does not rise, thereby solving the problem that the avalanche photodiode generates a large current due to strong light, thereby causing the signal output to the load circuit to fluctuate greatly and cause a background noise rise; at the same time, when the switch module is not turned on, the current is output to the load circuit normally to avoid the discharge of small signals and improve the quality of small signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a circuit structure diagram of a discharge circuit provided by an embodiment of the utility model;

[0023] Figure 2 It is a schematic diagram of the functional modules of a laser radar provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0025] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. It should be noted that the directional words such as "upper", "lower", "left", "right" and the like described in the embodiments of the present invention are described at the angles shown in the accompanying drawings and should not be understood as limitations on the embodiments of the present invention. In addition, in the context, it is also necessary to understand that when it is mentioned that an element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second" and the like are only used for descriptive purposes and do not represent any order, quantity or importance, but are only used to distinguish different components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific circumstances.

[0026] The term "including" and its variations used in the present invention are open inclusions, that is, "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment".

[0027] It should be noted that the concepts such as "first" and "second" mentioned in the present invention are only used to distinguish the corresponding contents, and are not used to limit the order or interdependence.

[0028] It should be noted that the modifications of "one" and "plurality" mentioned in the present invention are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0029] Figure 1 is a circuit structure diagram of a discharge circuit provided by an embodiment of the utility model, referring to Figure 1, the discharge circuit includes an avalanche photodiode D, a shunt module 10, a switch module 20 and a load circuit 30; one end of the avalanche photodiode D is connected to the external power supply VIN, and the other end is respectively connected to the input end of the shunt module 10 and the first end of the switch module 20; the first output end of the shunt module 10 is connected to the control end of the switch module 20; the second end of the switch module 20 is grounded; the second output end of the shunt module 10 is connected to the load circuit 30; when the current generated by the avalanche photodiode D exceeds the preset current value, the voltage at the second output end of the shunt module 10 meets the turn-on voltage of the switch module 20, so that the switch module 20 is turned on, so as to discharge the current output through the second output end of the shunt module 10 to the ground through the second end of the switch module 20; when the current generated by the avalanche photodiode D does not exceed the preset current value, the voltage at the second output end of the shunt module 10 does not meet the turn-on voltage of the switch module 20, the switch module 20 is not turned on, and the current output through the first output end of the shunt module 20 is equal to the current generated by the avalanche photodiode D.

[0030] The preset current value can be understood as a preset current value; for details, refer to Figure 1 The current of the avalanche photodiode D will increase with the increase of light intensity, and will be output to the load circuit 30 through the shunt module 10. When applied to the laser radar, the laser is emitted to the surface of the object to be measured and then reflected back. The intensity of the laser reflected nearby is large, and the intensity of the laser reflected by the distant object is small. There is a downward trend until the laser is reflected on the avalanche photodiode D. As the area of ​​the light spot on the avalanche photodiode D increases, the current of the avalanche photodiode D will become stronger accordingly. However, the current rises to the highest point, and then the current decreases as the light becomes weaker. This decrease, increase, and decrease will produce a background noise bulge. Therefore, the preset current value is set according to the current of the avalanche photodiode D in a slightly saturated state. As a result, when the current generated by the avalanche photodiode D exceeds the preset current value, the voltage at the second output terminal of the shunt module 10 satisfies the turn-on voltage of the switch module 20, and the switch module 20 is turned on. At this time, the current exceeding the preset current is output to the ground through the second output terminal of the shunt module 10, thereby being discharged, and the first output terminal of the shunt module 10 outputs the current of the preset current value to the load circuit 30, so that the avalanche photodiode D reaches a slightly saturated state; when the current generated by the avalanche photodiode D does not exceed the preset current value, the voltage at the second output terminal of the shunt module 10 fails to reach the turn-on voltage of the switch module 20, so that the current of the avalanche photodiode D all passes through the first output terminal of the shunt module 10 to the load circuit 30.

[0031] A discharge circuit provided by an embodiment of the utility model comprises an avalanche photodiode, a shunt module, a switch module and a load circuit; one end of the avalanche photodiode is connected to an external power supply, and the other end is respectively connected to an input end of the shunt module and a first end of the switch module; a second output end of the shunt module is connected to a control end of the switch module; a second end of the switch module is grounded; the first output end of the shunt module is connected to the load circuit; when the current generated by the avalanche photodiode exceeds a preset current value, the voltage at the second output end of the shunt module satisfies the turn-on voltage of the switch module, so that the switch module is turned on, so as to discharge the current outputted through the second output end of the shunt module to the ground through the second end of the switch module, so that the current outputted from the first output end of the shunt module is equal to the preset current value; when the current generated by the avalanche photodiode does not exceed a preset current value, the voltage at the second output end of the shunt module satisfies the turn-on voltage of the switch module, so that the switch module is turned on, so as to discharge the current outputted through the second output end of the shunt module to the ground through the second end of the switch module, so that the current outputted from the first output end of the shunt module is equal to the preset current value; When the current value exceeds the preset value, the voltage at the second output end of the shunt module does not meet the turn-on voltage of the switch module, the switch module is not turned on, and the current output through the first output end of the shunt module is equal to the current generated by the avalanche photodiode. The above technical scheme, when the light energy is strong and the current generated by the avalanche photodiode exceeds the current of the avalanche photodiode in a micro-saturation state, the voltage output to the switch module meets its turn-on voltage, and the switch module is turned on to discharge the excess current to the ground until the background noise does not rise, thereby solving the problem that the avalanche photodiode generates a large current due to strong light, thereby causing the signal output to the load circuit to fluctuate greatly and cause a background noise rise. At the same time, when the switch module is not turned on, the current is output to the load circuit normally to avoid the discharge of small signals and improve the quality of small signals.

[0032] Optionally, the shunt module 10 includes a first shunt resistor R1 and a second shunt resistor R2; the resistance of the first shunt resistor R1 is greater than the resistance of the second shunt resistor R2; one end of the first shunt resistor R1 is connected to the other end of the avalanche photodiode D as the input end of the shunt module 10; the other end of the first shunt resistor R1 is respectively connected to one end of the second shunt resistor R2 and the load circuit 30; the other end of the second shunt resistor R2 is connected to the control end of the switch module 20. The switch module 20 includes a transistor Q; the first pole of the transistor Q is connected to the input end of the shunt module 10 as the first end of the switch module 20; the second pole of the transistor Q is grounded as the second end of the switch module 20; the base of the transistor Q is connected to the first output end of the shunt module 10 as the control end of the switch module 20.

[0033] Specifically, refer to Figure 1As the light becomes stronger, the current generated by the avalanche photodiode D gradually increases, and the current is output to the load circuit 30 through the first shunt resistor R1. When the current exceeds the preset limit, the voltage drop across the second shunt resistor R2 meets the turn-on voltage of the transistor Q. At this time, the transistor Q is turned on, and the current passing through the second shunt resistor R2 is discharged to the ground through the transistor Q. In an optional embodiment of the utility model, a third discharge resistor R3 is also included, which can speed up the current discharge speed, and the size of the discharge current can be determined by the size of the third discharge resistor R3. At the same time, the junction capacitance of the transistor is small and the pulse width is narrow, so there will be no drag point phenomenon, and thus the quality of the point cloud signal will not be affected.

[0034] Optionally, the discharge circuit further includes a filter module 40 , one end of the filter module 40 is connected to an external power source VIN, and the other end of the filter module 40 is connected to one end of the avalanche photodiode D.

[0035] Exemplarily, the filter module 40 includes a filter resistor R4 and a first capacitor C1; one end of the filter resistor R4 is connected to the external power supply VIN, and the other end is respectively connected to one end of the avalanche photodiode D and one end of the first capacitor C1; the other end of the first capacitor C1 is grounded. Specifically, in order to prevent the clutter input by the external power supply VIN and avoid the high-frequency component from causing the avalanche photodiode D to avalanche, the filter module 40 is used to filter out the clutter to obtain the low-frequency component.

[0036] Optionally, the load circuit 30 includes a filter unit 31 and an amplifier unit 32; the input end of the filter unit 31 is connected to the first output end of the shunt module 10; the output end of the filter unit 31 is connected to the input end of the amplifier unit. The amplifier unit 32 includes a transimpedance amplifier TIA; the in-phase input end + of the transimpedance amplifier TIA is connected to the output end of the filter unit 31 as the input end of the amplifier unit 32; the inverting input end - of the transimpedance amplifier TIA is respectively connected to one end of the first voltage-dividing resistor R5 and the second voltage-dividing resistor R6; the other end of the second voltage-dividing resistor R6 is connected to the output end of the transimpedance amplifier TIA; the other end of the first voltage-dividing resistor R5 is grounded; the positive end of the transimpedance amplifier is connected to the external positive power supply VCC+; the negative end of the transimpedance amplifier TIA is connected to the external negative power supply VCC-. The filter unit 31 includes a second filter resistor and a second capacitor C2; one end of the second filter resistor R7 is connected to the output end of the shunt module, and the other end is connected to one end of the second capacitor C2; the other end of the second capacitor C2 is connected to the input end of the amplifier unit.

[0037] Specifically, in an optional embodiment of the utility model, the Vout terminal is connected to the receiving end of the optical fiber communication integrated circuit, so it is necessary to convert the optical signal into a current signal through an avalanche photodiode D, and then convert the current signal into a voltage signal through a transimpedance amplifier TIA. Therefore, after filtering out clutter through a filtering unit, the photocurrent is amplified by an amplification unit and output through the Vout terminal.

[0038] Optionally, the utility model further provides a laser radar, Figure 2 This is a schematic diagram of a functional module of a laser radar provided by an embodiment of the utility model, with reference to Figure 2 , including a signal transmitting module, a receiving module and a signal processing module; since the laser radar includes the discharge circuit in the above embodiment, it has the corresponding beneficial effects of the discharge circuit provided by the embodiment of the utility model, which will not be repeated here.

[0039] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention is described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A discharge circuit, characterized in that: It includes an avalanche photodiode, a shunt module, a switch module and a load circuit; One end of the avalanche photodiode is connected to an external power supply, and the other end is respectively connected to the input end of the shunt module and the first end of the switch module; the second output end of the shunt module is connected to the control end of the switch module; the second end of the switch module is grounded; the first output end of the shunt module is connected to the load circuit; When the current generated by the avalanche photodiode exceeds a preset current value, the voltage at the second output end of the shunt module satisfies the turn-on voltage of the switch module, so that the switch module is turned on, so as to discharge the current output through the second output end of the shunt module to the ground through the second end of the switch module, so that the current output from the first output end of the shunt module is at the preset current value; When the current generated by the avalanche photodiode does not exceed the preset current value, the voltage at the second output end of the shunt module does not meet the turn-on voltage of the switch module, the switch module is not turned on, and the current output through the first output end of the shunt module is equal to the current generated by the avalanche photodiode.

2. The circuit according to claim 1, characterized in that The shunt module includes a first shunt resistor and a second shunt resistor; the resistance of the first shunt resistor is greater than the resistance of the second shunt resistor; One end of the first shunt resistor is connected to the other end of the avalanche photodiode as an input end of the shunt module; The other end of the first shunt resistor is connected to one end of the second shunt resistor and the load circuit respectively; the other end of the second shunt resistor is connected to the control end of the switch module.

3. The circuit according to claim 1, characterized in that The switch module includes a transistor; the first pole of the transistor serves as the first end of the switch module and the input end of the shunt module; the second pole of the transistor serves as the second end of the switch module and is grounded; and the base of the transistor serves as the control end of the switch module and is connected to the first output end of the shunt module.

4. The circuit according to claim 2, characterized in that The shunt module further includes a third shunt resistor; one end of the third shunt resistor is connected to the second end of the switch module, and the other end is grounded.

5. The circuit according to claim 1, characterized in that It also includes a filter module, one end of which is connected to the external power supply, and the other end of which is connected to one end of the avalanche photodiode.

6. The circuit according to claim 5, characterized in that The filtering module includes a first filtering resistor and a first capacitor; One end of the first filter resistor is connected to the external power supply, and the other end is respectively connected to one end of the avalanche photodiode and one end of the capacitor; the other end of the capacitor is grounded.

7. The circuit according to claim 1, characterized in that The load circuit includes a filtering unit and an amplifying unit; the input end of the filtering unit is connected to the first output end of the shunt module; the output end of the filtering unit is connected to the input end of the amplifying unit.

8. The circuit according to claim 7, characterized in that The amplification unit includes a transimpedance amplifier; the non-inverting input terminal of the transimpedance amplifier is connected to the output terminal of the filtering unit as the input terminal of the amplification unit; the inverting input terminal of the transimpedance amplifier is respectively connected to one end of a first voltage-dividing resistor and a second voltage-dividing resistor; the other end of the second voltage-dividing resistor is connected to the output terminal of the transimpedance amplifier; the other end of the first voltage-dividing resistor is grounded; the positive terminal of the transimpedance amplifier is connected to an external positive power supply; and the negative terminal of the transimpedance amplifier is connected to an external negative power supply.

9. The circuit according to claim 7, characterized in that The filtering unit includes a second filtering resistor and a second capacitor; One end of the second filter resistor is connected to the output end of the shunt module, and the other end is connected to one end of the second capacitor; the other end of the second capacitor is connected to the input end of the amplification unit.

10. A laser radar, characterized in that: Comprising the discharge circuit as described in any one of claims 1-9.

Images