Laser radar and driving circuit and driving method thereof

Abstract

A laser radar, a driving circuit and a driving method thereof, the driving circuit comprising: a switch control unit for selectively controlling the light emitting device to emit light and stop emitting light; a first monitoring unit for monitoring the light emitting energy of the light emitting device; a second monitoring unit for monitoring the light emitting time of the light emitting device; a safety control unit for controlling the light emitting device to stop emitting light by the switch control unit when the light emitting energy reaches a first threshold value and / or the light emitting time reaches a second threshold value. The technical scheme can reduce the eye safety risk caused by the light emitting of the laser on the basis of ensuring the working efficiency of the laser radar.

Description

Technical Field

[0001] This invention relates to the field of lidar, and in particular to a lidar and its driving circuit and driving method. Background Technology

[0002] In lidar, laser energy exceeding a certain value can cause irreversible damage to human eye tissue. Laser safety standards define laser energy requirements; the laser emitting circuit must ensure that, even in the event of a single-point failure (primarily a switch failure), the emitted laser energy does not exceed the safety threshold for the human eye. The high-side drive circuit of the laser can drive the laser to emit light; its basic principle is as follows... Figure 1 As shown, the high-side drive circuit can be represented as an equivalent model of a switch K1 and a laser L1 connected in series. When switch K1 is on, laser L1 emits light; when switch K1 is off, laser L1 stops emitting light. The pulse width of laser L1 is determined by the on-time of switch K1; for example, the longer the on-time, the wider the pulse width. The energy emitted by the laser is determined by the on-resistance of the switch and the characteristics of the laser itself. When the switch is short-circuited, the laser will continue to emit light, posing a safety risk to the human eye.

[0003] To reduce the eye safety risk caused by short circuits in the high-side drive circuit of the laser, the simplest way is to split the high-side drive switch into two switches connected in series, such as... Figure 2 As shown, laser L1 can only emit light when both switches (K1 and K2) are turned on simultaneously. Therefore, a short circuit in a single switch does not pose a safety risk to the human eye, while a simultaneous short circuit in both switches constitutes a double-point failure, which is typically extremely rare.

[0004] However, in some applications, such as lidar using direct time-of-flight (dTof) ranging, higher laser energy and energy efficiency are preferred. If the switch size is fixed, the on-resistance of two switches connected in series doubles compared to a single switch, leading to a significant decrease in laser energy and energy efficiency, which fails to meet the application requirements of lidar. Summary of the Invention

[0005] The technical problem solved by this invention is to reduce the eye safety risks caused by laser emission while ensuring the working efficiency of lidar.

[0006] To address the aforementioned technical problems, in a first aspect, embodiments of the present invention provide a driving circuit for a lidar, the driving circuit comprising: a switch control unit for selectively controlling the light emitting device to emit light and stop emitting light; a first monitoring unit for monitoring the emitting energy of the light emitting device; a second monitoring unit for monitoring the emitting time of the light emitting device; and a safety control unit for controlling the light emitting device to stop emitting light through the switch control unit when the emitting energy reaches a first threshold and / or the emitting time reaches a second threshold.

[0007] Optionally, the second monitoring unit monitors whether the voltage of the light emitting device reaches the light emission voltage threshold of the light emitting device.

[0008] Optionally, the driving circuit further includes a first resistor connected in parallel with the light emitting device, the first resistor being used to discharge the light emitting device.

[0009] Optionally, the driving circuit further includes: a logic control unit, configured to output a first control signal to the safety control unit when the luminous energy reaches a first threshold and / or the luminous time reaches a second threshold, wherein the safety control unit controls the light emitting device to stop emitting light based on the first control signal.

[0010] Optionally, the second monitoring unit includes: a first comparison subunit, configured to output a first voltage based on a comparison result between the voltage of the light emitting device and a first reference voltage, wherein the first voltage reflects the light emission time of the light emitting device.

[0011] Optionally, the first comparison subunit includes: a first voltage divider subunit for dividing the voltage of the optical emitting device; and a first comparator, wherein the positive input terminal of the first comparator is coupled to the output terminal of the voltage divider subunit, the negative input terminal of the first comparator is connected to the first reference voltage, and the output terminal of the first comparator outputs the first voltage.

[0012] Optionally, the second monitoring unit outputs a monitoring signal when it detects that the emission time has reached a second threshold. The second monitoring unit further includes a second comparison subunit, which is used to output the monitoring signal based on the comparison result between the first voltage and the second reference voltage.

[0013] Optionally, the second comparison subunit includes: a first energy storage subunit for charging or discharging according to the first voltage; and a first control subunit for outputting the monitoring signal when the voltage of the first energy storage subunit is greater than the second reference voltage.

[0014] Optionally, the second monitoring unit further includes: a first filtering subunit, coupled to the output terminal of the first voltage divider subunit, for filtering the voltage after voltage division.

[0015] Optionally, the first control subunit includes: an inverter, the input terminal of which is coupled to the output terminal of the first comparator subunit; a first MOSFET, the gate of which is coupled to the output terminal of the inverter, the source of which is grounded, and the drain of which is coupled to the second terminal of the first energy storage subunit; a second MOSFET, the gate of which is coupled to the output terminal of the inverter, and the source of which is coupled to the second terminal of the first energy storage subunit; an adjustable current source, the first terminal of which is connected to a power supply voltage, and the second terminal of which is coupled to the drain of the second MOSFET; and a second comparator, the positive input terminal of which is coupled to the source of the second MOSFET, the negative input terminal of which is coupled to a second reference voltage, and the output terminal of which outputs the monitoring signal.

[0016] Optionally, the switch control unit includes: a second energy storage unit, a first terminal of which is connected to a power supply voltage and a second terminal of which is grounded; a first switch unit, a first terminal of which is coupled to the first terminal of the second energy storage unit and a second terminal of which is coupled to a light emitting device, the first switch unit being used to selectively drive the light emitting device to emit light using the second energy storage unit; and a second switch unit, the second switch unit being used to selectively discharge the second energy storage unit.

[0017] Optionally, the first monitoring unit monitors whether the voltage at the first terminal of the second energy storage unit reaches the second threshold.

[0018] Optionally, the switch control unit further includes: a third switch unit, the first end of which is connected to the power supply voltage, the second end of which is coupled to the first end of the second energy storage unit, and the first end of the first switch unit, the second end of which is coupled to the anode of the light emitting device.

[0019] Optionally, the second switching unit includes: a third MOS transistor, the gate of which is coupled to the output terminal of the safety control unit, the drain of which is connected to the power supply voltage, and the source of which is grounded.

[0020] Optionally, the second switching unit includes: a fourth MOSFET, the gate of which is connected to a first control signal and the source of which is connected to a first voltage; a fifth MOSFET, the gate of which is connected to a second control signal and the source of which is grounded, and the drain of which is coupled to the drain of the fourth MOSFET; a sixth MOSFET, the gate of which is connected to the second control signal and the source of which is connected to a second voltage, the second voltage being less than the first voltage; and a third MOSFET, the gate of which is coupled to the drain of the sixth MOSFET and the drain of the fourth MOSFET, the drain of which is connected to a power supply voltage and the drain of which is grounded.

[0021] Optionally, the second switching unit further includes: a first driver, the input terminal of which receives a third control signal, and the output terminal of which outputs the first control signal; and a second driver, the input terminal of which is coupled to the output terminal of the safety control unit, and the output terminal of which outputs the second control signal.

[0022] Optionally, the second switching unit further includes a level shifter, the input of which is coupled to the output of the safety control unit, and the output of which outputs the third control signal.

[0023] Optionally, the switch control unit includes a second energy storage unit, which is used to input charge to the light emitting device to control the light emitting device to emit light, and the first monitoring unit monitors the voltage change of the second energy storage unit.

[0024] Optionally, the first monitoring unit includes: a second voltage divider subunit for dividing the power supply voltage to output a voltage divider signal; a digital-to-analog converter for providing a reference voltage; and a third comparator, the negative input of which is connected to the voltage divider signal, and the positive input of which is coupled to the output of the digital-to-analog converter.

[0025] Optionally, the first monitoring unit includes: a second filtering subunit, coupled to the output terminal of the second voltage divider subunit, for filtering the voltage divider signal.

[0026] Secondly, embodiments of the present invention also disclose a driving method for a lidar, the lidar including a light emitting device, the driving method including: monitoring the light emission energy of the light emitting device, and / or monitoring the light emission time of the light emitting device; when the light emission energy reaches a first threshold, and / or the light emission time reaches a second threshold, controlling the light emitting device to stop emitting light.

[0027] Optionally, monitoring the emission time of the light emitting device includes: monitoring whether the voltage of the light emitting device reaches the emission voltage threshold of the light emitting device.

[0028] Thirdly, embodiments of the present invention also disclose a lidar, which includes a light emitting device and the driving circuit.

[0029] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:

[0030] In this invention, the driving circuit for the lidar includes a first monitoring unit and a second monitoring unit. The first monitoring unit monitors the luminous energy of the light emitting device, while the second monitoring unit monitors the luminous duration of the light emitting device. When the luminous energy reaches a first threshold and / or the luminous duration reaches a second threshold, the safety control unit controls the light emitting device to stop emitting light. This embodiment of the invention, by separately monitoring the luminous energy and luminous duration of the high-side driven light emitting device, and controlling the laser to stop emitting light when either reaches its corresponding trigger threshold, minimizes the eye safety risks associated with laser emission. Furthermore, this invention does not increase power consumption, ensuring the luminous energy and energy efficiency of the light emitting device in the lidar.

[0031] Furthermore, the second monitoring unit monitors whether the voltage of the light emitting device reaches the light emission voltage threshold of the light emitting device. Since the light emitting device only emits light when its voltage reaches the light emission voltage threshold, in this invention, the second monitoring unit can monitor the light emission time of the light emitting device by monitoring its voltage and the light emission voltage threshold. In addition, when the switch control unit slowly leaks current to the light emitting device, the second monitoring unit can also detect the abnormality, preventing the light emitting device from emitting light continuously and ensuring the light emission safety of the light emitting device. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the structure of a laser high-side drive circuit in the prior art;

[0033] Figure 2 This is a schematic diagram of another laser high-side drive circuit in the prior art;

[0034] Figure 3 This is a schematic diagram of a driving circuit for lidar provided in an embodiment of the present invention;

[0035] Figure 4 This is a timing diagram of a switch drive signal, voltage, and laser pulse signal provided in an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of another driving circuit for lidar provided in an embodiment of the present invention;

[0037] Figure 6 This is a schematic diagram of the specific structure of a first monitoring unit provided in an embodiment of the present invention;

[0038] Figure 7 This is a schematic diagram of the specific structure of a second monitoring unit provided in an embodiment of the present invention;

[0039] Figure 8 This is a timing diagram of each signal in the second monitoring unit provided in this embodiment of the invention;

[0040] Figure 9 This is a schematic diagram of the specific structure of a second switching unit provided in an embodiment of the present invention;

[0041] Figure 10 This is a flowchart of a driving method for lidar provided in an embodiment of the present invention. Detailed Implementation

[0042] As described in the background section, in some applications, such as lidar using direct time-of-flight (dTof) ranging, higher laser luminous energy and energy efficiency are desirable. If the switch size is fixed, the on-resistance of two switches connected in series doubles compared to a single switch, leading to a significant decrease in laser luminous energy and energy efficiency, which fails to meet the application requirements of lidar.

[0043] The driving circuit of this invention includes a switch control unit for selectively controlling the light emitting device to emit light and stop emitting light; a first monitoring unit for monitoring the emitting energy of the light emitting device; a second monitoring unit for monitoring the emitting time of the light emitting device; and a safety control unit for controlling the light emitting device to stop emitting light through the switch control unit when the emitting energy reaches a first threshold and / or the emitting time reaches a second threshold. In this invention, the driving circuit for the lidar includes a first monitoring unit and a second monitoring unit. The first monitoring unit monitors the emitting energy of the light emitting device, and the second monitoring unit monitors the emitting time of the light emitting device. When the emitting energy reaches the first threshold and / or the emitting time reaches the second threshold, the safety control unit controls the light emitting device to stop emitting light. By monitoring the emitting energy and emitting time separately, and controlling the laser to stop emitting light when either reaches the corresponding trigger threshold, this embodiment of the invention minimizes the eye safety risks caused by laser emission. Furthermore, this invention does not increase power consumption, ensuring the emitting energy and energy efficiency of the lidar.

[0044] Furthermore, the second monitoring unit monitors whether the voltage of the light emitting device reaches the light emission voltage threshold of the light emitting device. Since the light emitting device only emits light when its voltage reaches the light emission voltage threshold, in this invention, the second monitoring unit can monitor the light emission time of the light emitting device by monitoring its voltage and the light emission voltage threshold. In addition, if the leakage current from the switch control unit to the light emitting device is slow, the second monitoring unit can also detect the abnormality, preventing the light emitting device from emitting light continuously and ensuring the light emission safety of the light emitting device.

[0045] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0046] Figure 3 This is a schematic diagram of a driving circuit for lidar according to an embodiment of the present invention.

[0047] Figure 3 The light emitting device L1 can emit light. Specifically, the light emitting device L1 can be a laser, such as a vertical-cavity surface-emitting laser (VCSEL), or any other feasible type of light emitting device. Figure 3 The light emitting device L1 shown is one, but in actual applications, the number of light emitting devices L1 can be multiple, and the embodiments of the present invention do not limit this.

[0048] The driving circuit in this embodiment can also be called a high-side driving circuit, which can drive the laser to emit light.

[0049] In this embodiment, the switch control unit can selectively control the light emitting device L1 to emit light and stop emitting light. Specifically, the switch control unit may include a first switch unit, a second energy storage unit, and a second switch unit. The first switch unit and the second switch unit can be single-pole single-throw switches, such as... Figure 3 As shown in S1 and S2, the second energy storage unit can be a capacitor C1.

[0050] When the light emitting device L1 is operating normally, it drives the first switching unit S1 to conduct and the second switching unit S2 to turn off. Specifically, the power supply VDD first charges the capacitor C1, then the first switching unit S1 conducts, and the capacitor C1 discharges, driving the light emitting device L1 to emit light. The energy emitted by the light emitting device L1 mainly comes from the charge stored on the capacitor C1. The voltage change at node VDD of capacitor C1 (i.e., the voltage change between the stored energy voltage of capacitor C1 and the voltage of capacitor C1 after emission) reflects the emitting energy of the light emitting device L1.

[0051] Therefore, the first monitoring unit 301 can monitor the light emission energy of the light emitting device L1 by monitoring the voltage change on node vdd of capacitor C1. Normally, capacitor C1 is fully charged. Detecting the voltage change at node vdd is actually detecting the difference between the voltage of capacitor C1 when it is fully charged (i.e., the voltage of light emitting device L1 before it emits light) and the voltage of light emitting device L1 after it emits light. Since the voltage of capacitor C1 is fixed when it is fully charged, the voltage change at node vdd can be the voltage of capacitor C1 after light emitting device L1 emits light.

[0052] When the voltage of node Vdd exceeds the set safety threshold, indicating that the luminous energy has reached the first threshold, the system enters an eye safety protection state. The safety control unit 303 then controls the light emitting device L1 to stop emitting light via the switch control unit. Specifically, the safety control unit 303 drives the first switch unit S1 to open and the second switch unit S2 to open, grounding capacitor C1 to GND1, thereby discharging capacitor C1 and reducing the voltage of node Vdd, which in turn reduces the luminous energy of the light emitting device L1, thus controlling it to stop emitting light. In this situation, even if the first switch unit S1 is short-circuited, the light emitting device L1 will not continue to emit light, reducing the eye safety risk posed by laser emission.

[0053] However, when the first switching unit S1 leaks current (i.e., the switch is only slightly burned out, and the short circuit is not severe), it will also leak current to the light emitting device L1 through the first switching unit S1 while charging the capacitor C1. The light emitting device L1 will then continue to emit light at a relatively low intensity. This is because the voltage of the power supply VDD is very high (e.g., 30V), and the equilibrium voltage of capacitor C1 after leakage may be greater than the light emission voltage threshold of the light emitting device L1. At this time, the charging current and discharging current on capacitor C1 will reach equilibrium, and the change in the node VDD voltage will be minimal. The first monitoring unit 301 may not detect that the luminous energy has reached the first threshold, but the light emitting device L1 continues to emit light, which still poses a risk to human eye safety.

[0054] To avoid the above situation, the driving circuit of this embodiment of the invention is further provided with a second monitoring unit 302, which can monitor the light emission time of the light emitting device L1. When the light emission time of the light emitting device L1 reaches the second threshold, the safety control unit 303 can also control the light emitting device L1 to stop emitting light through the switch control unit.

[0055] In one specific embodiment, the second monitoring unit 302 monitors whether the voltage of the light emitting device L1 reaches the light emission voltage threshold of the light emitting device L1. Preferably, the second monitoring unit 302 monitors whether the anode voltage of the light emitting device L1 reaches the light emission voltage threshold.

[0056] Specifically, the light-emitting principle of the light-emitting device L1 dictates that the voltage of the anode Lda needs to be greater than its emission voltage threshold when the light-emitting device L1 emits light. For example, the emission voltage threshold of a 3-layer junction VCSEL laser is approximately 5V. Therefore, the second monitoring unit 302 can directly and accurately determine the emission time of the light-emitting device L1 by monitoring the voltage of the anode Lda. In other words, the duration for which the voltage of the anode Lda reaches the emission voltage threshold is the emission time of the light-emitting device L1.

[0057] Refer to together Figure 4 The switching drive signal for the first switching unit S1 is a square wave signal. When the switching drive signal is high, the first switching unit S1 is turned on, and the voltage of the anode Lda of the light emitting device L1 gradually increases. When the voltage reaches the emission voltage threshold, the light emitting device L1 emits light. After the first switching unit S1 is turned off, the voltage of the anode Lda gradually decreases. When the voltage falls below the emission voltage threshold, the light emitting device L1 stops emitting light. The pulse width of the laser pulse can represent the emission time of the light emitting device L1.

[0058] When the light emitting device L1 is operating normally, capacitor C1 is charged first, then the first switching unit S1 is turned on, and capacitor C1 discharges to drive the light emitting device L1 to emit light. When the first monitoring unit 301 detects that the light emission energy of the light emitting device L1 reaches the first threshold, and / or the second monitoring unit 302 detects that the light emission time reaches the second threshold, the safety control unit 303 controls the light emitting device L1 to stop emitting light. Because a combination of monitoring light emission energy and light emission time is used, even if the leakage current from the switching control unit to the light emitting device is slow and the light emission energy has not reached the first threshold, but the light emitting device continues to emit light, the second monitoring unit can still detect the abnormality by monitoring the light emission time, ensuring the reliability of the monitoring.

[0059] In this embodiment, the safety control unit 303 controlling the light emitting device L1 to stop emitting light means: the safety control unit 303 controls the first switch unit S1 to turn off, controls the second switch unit S2 to turn on, the capacitor C1 is grounded and discharged, and the light emitting device L1 stops emitting light. Correspondingly, the safety control unit 303 controlling the light emitting device L1 to emit light means: the capacitor C1 is charged, the safety control unit 303 controls the first switch unit S1 to turn on, controls the second switch unit S2 to turn off, the capacitor C1 is connected to the light emitting device L1 and discharges, driving the light emitting device L1 to emit light.

[0060] Specifically, to ensure that the voltage of the anode Lda of the light emitting device L1 discharges below the emission voltage threshold, the smaller the capacitance value of the capacitor C1, the better. This is because a smaller capacitance value means a faster discharge rate of capacitor C1, resulting in a relatively shorter emission time for the light emitting device L1. In other words, the emission time of the light emitting device L1 is determined by the discharge rate of capacitor C1 (i.e., the capacitance value of capacitor C1).

[0061] It is understood that the specific values ​​of the first threshold and the second threshold can be set according to the actual application scenario, and the embodiments of the present invention do not impose any restrictions on this.

[0062] In a non-limiting embodiment, due to the parasitic capacitances of the light emitting device L1 and the first switching unit S1, the anode Lda typically has a large parasitic capacitance, and it will take a long time to slowly discharge to 0 after the light emitting device L1 stops emitting light. (See also...) Figure 5 In this embodiment of the invention, a first resistor R1 is provided, which enables the anode Lda to discharge rapidly, thereby correctly reflecting the emission time of the light emitting device L1.

[0063] Specifically, the first end of the first resistor R1 is coupled to the anode of the light emitting device L1 and the input terminal of the second monitoring unit 302, and the second end of the first resistor R1 is grounded.

[0064] It should be noted that the first resistor R1 can also be replaced by a switching device. When the light emission energy reaches the first threshold and / or the light emission time of the light emitting device L1 reaches the second threshold, the safety control unit 303 controls the switching device to turn on, so as to achieve rapid discharge of the anode Lda.

[0065] In a non-limiting embodiment, reference continues... Figure 5 The driving circuit may also include a logic control unit 304. The logic control unit 304 is used to output a first control signal to the safety control unit 303 when the light emission energy reaches a first threshold and / or the light emission time of the light emitting device L1 reaches a second threshold. The safety control unit 303 controls the light emitting device L1 to stop emitting light based on the first control signal.

[0066] In a specific implementation, the logic control unit 304 can be an OR gate. When the first monitoring unit 301 detects that the light emission energy of the light emitting device L1 reaches the first threshold, the first monitoring unit 301 outputs a high-level signal; when the second monitoring unit 302 detects that the light emission time reaches the second threshold, the second monitoring unit 302 outputs a high-level signal.

[0067] When the first monitoring unit 301 detects that the light emission energy of the light emitting device L1 reaches a first threshold and / or the second monitoring unit 302 detects that the light emission time reaches a second threshold, indicating that either the first monitoring unit 301 or the second monitoring unit 302 outputs a high level (1), an OR gate outputs a first control signal. The first control signal can be a high level (1). In response to the first control signal, the safety control unit 303 controls the light emitting device L1 to stop emitting light.

[0068] In one specific embodiment, the switch control unit includes a first switch unit S1, a second switch unit S2, a third switch unit S3, and a capacitor C1. The third switch unit S3 can control the charging of the capacitor C1. Specifically, when the third switch unit S3 is turned on, the power supply VDD charges the capacitor C1; when the third switch unit S3 is turned off, the power supply VDD stops charging the capacitor C1.

[0069] In this embodiment, the safety control unit 303 controlling the light emitting device L1 to stop emitting light means: the safety control unit 303 controls the third switch unit S3 to turn off, controls the first switch unit S1 to turn off, controls the second switch unit S2 to turn on, the capacitor C1 is grounded and discharged, and the light emitting device L1 stops emitting light. Correspondingly, the safety control unit 303 controlling the light emitting device L1 to emit light means: the safety control unit 303 controls the third switch unit S3 to turn on, the capacitor C1 is charged; controls the first switch unit S1 to turn on, controls the second switch unit S2 to turn off, the capacitor C1 is connected to the light emitting device L1 and discharges, driving the light emitting device L1 to emit light.

[0070] In a non-limiting embodiment of the present invention, the input terminal of the first monitoring unit 301 is connected to a power supply voltage. Specifically, it can be directly connected to a power supply voltage, or it can be connected through a third switching unit S3 (e.g., ...). Figure 5 (As shown) Connect the power supply voltage.

[0071] Assume the voltage connected to the input terminal of the first monitoring unit 301 is Vdd. Since the driving voltage of the optical emitting device L1 is usually relatively large, such as 30-40V, while the comparator's withstand voltage is usually 5V, it is necessary to divide Vdd. The first monitoring unit 301 is equipped with a second voltage divider subunit to divide the voltage Vdd connected to the input terminal of the first monitoring unit 301.

[0072] In specific implementation, refer to the following: Figure 6The second voltage divider unit may include capacitors C2 and C4. The first terminal of capacitor C4 is connected to voltage Vdd, and the second terminal of capacitor C4 is coupled to the first terminal of capacitor C2. The second terminal of capacitor C2 is grounded. The second terminal of capacitor C4 and the first terminal of capacitor C2 output a voltage divider signal. Resistor R3 provides DC bias, and voltage VREF is the bias voltage, which also serves as the reference voltage for the digital-to-analog converter (DAC). VREF, as the bias voltage, is used to offset the input signal to the input range of the DAC.

[0073] It should be noted that the second voltage divider unit can also use a resistor voltage divider, that is, capacitors C2 and C4 can be replaced by two resistors respectively, which will not be elaborated here.

[0074] In this embodiment, the first monitoring unit 301 further includes a digital-to-analog converter (DAC) and a third comparator (CMP). The reference voltage output by the DAC is any value between 0 and VREF, where VREF is the bias voltage. The reference voltage output by the DAC serves as a first threshold value, which can be adaptively adjusted. A voltage divider signal is connected to the negative input of the third comparator (CMP), and the positive input of the third comparator (CMP) is coupled to the output of the DAC. When the third comparator (CMP) outputs a high level, it indicates that the first monitoring unit 301 has detected that the voltage change of node vdd exceeds the set threshold. At this time, the safety control unit 303 controls the light emitting device L1 to stop emitting light.

[0075] Furthermore, the first monitoring unit 301 may also include a second filtering subunit for filtering the voltage-divided signal. (Continue referring to...) Figure 6 The second filtering subunit includes resistor R2 and capacitor C3. This subunit filters out glitches and high-frequency noise from the voltage divider signal and inputs it to the negative input of the third comparator CMP. The first monitoring unit 301 monitors node vdd to obtain the light emission energy of the light emitting device L1; therefore, low-pass filtering of the voltage divider signal enables faster signal transmission.

[0076] In a non-limiting embodiment of the present invention, the second monitoring unit 302 may include: a first comparison subunit, configured to output a first voltage based on a comparison result between the voltage of the light emitting device L1 and a first reference voltage, wherein the first voltage reflects the emission time of the light emitting device L1. Thus, a monitoring signal can be output based on the first voltage output by the first comparison subunit, and the safety control unit 303 can control the light emitting device L1 to stop emitting light in response to the monitoring signal.

[0077] Further, please refer to Figure 7The first comparator subunit includes a first voltage divider subunit and a first comparator CMP1. The first voltage divider subunit includes resistors R4 and R5. The first terminal of resistor R5 is grounded, and the second terminal of resistor R5 is coupled to the first terminal of resistor R4. The second terminal of resistor R4 is coupled to the anode lda of the light emitting device L1. The second terminal of resistor R5 and the first terminal of resistor R4 serve as the output terminals of the first voltage divider subunit, outputting the divided voltage.

[0078] The positive input terminal of the first comparator CMP1 is coupled to the output terminal of the voltage divider unit, the negative input terminal of the first comparator CMP1 is connected to the first reference voltage VREF2, and the output terminal of the first comparator CMP1 outputs the first voltage.

[0079] Furthermore, the second monitoring unit 302 also includes a first filtering subunit, which is coupled to the output of the first voltage divider subunit and is used to filter the voltage after voltage division. Please refer to [link / reference needed] for details. Figure 7 The first filter subunit includes resistor R5 and capacitor C5.

[0080] The voltage of the anode Lda of the light emitting device L1 is fed into the positive input terminal of the first comparator CMP1 through a DC voltage divider and low-pass filter circuit composed of resistors R4, R5 and C5, and compared with the first reference voltage VREF2. The width of the digital signal output by the first comparator CMP1 can represent the pulse width of the light emitting device L1, reflecting the duration of the light emitting device L1.

[0081] Furthermore, the second monitoring unit 302 outputs a monitoring signal when it detects that the emission time has reached the second threshold. The second monitoring unit 302 also includes a second comparison subunit, used to output a monitoring signal based on the comparison result between the first voltage and the second reference voltage. Specifically, it outputs a monitoring signal when the first voltage is greater than the second reference voltage, and the monitoring signal can be a high-level signal.

[0082] In one specific embodiment, the second comparison subunit includes a first energy storage subunit and a first control subunit (also referred to as a pulse width comparator). The first control subunit is used to output a monitoring signal when the voltage of the first energy storage subunit is greater than the second reference voltage.

[0083] Specifically, continue to refer to Figure 7 The first control subunit includes an inverter INV, a first MOSFET M1, a second MOSFET M2, an adjustable current source IDAC, and a second comparator CMP2. The first energy storage subunit includes a capacitor C6.

[0084] Specifically, the adjustable current source IDAC controls the charging speed of capacitor C6; that is, the larger the output current, the faster the charging speed, and the shorter the trigger time required for the voltage of capacitor C6 to exceed the second reference voltage VREF3. Therefore, the trigger time can be set according to the current magnitude of the adjustable current source IDAC. This trigger time determines the speed at which the safety control unit 303 activates the protection mechanism, thereby determining the duration of light emission from the light emitting device L1.

[0085] Specifically, the output signals of the first comparator CMP1 and the inverter INV control one of the first MOSFET M1 and the second MOSFET M2 to turn on and the other to turn off. See also... Figure 8 When the output terminal CMP1_OUT of the first comparator CMP1 is high and the inverter INV is low, the second MOSFET M2 is turned on, the first MOSFET M1 is turned off, and the current source IDAC charges the capacitor C6. The voltage at the positive input terminal CMP2+ of the second comparator CMP2 gradually increases. When the voltage at the positive input terminal CMP2+ of the second comparator CMP2 is greater than the second reference voltage VREF3, the output terminal CMP2_OUT of the second comparator CMP2 is high, and the second monitoring unit 302 outputs a monitoring signal, such as a high level. At this time, the safety control unit 303 controls the light emitting device L1 to stop emitting light. Therefore, when the first switching unit S1 leaks current, the light emitting device L1 continues to emit light, and correspondingly, the first comparator CMP1 and the second comparator CMP2 successively output high levels. The safety control unit 303 activates the protection mechanism and controls the light emitting device L1 to stop emitting light.

[0086] Continue to refer to Figure 8 When the output terminal CMP1_OUT of the first comparator CMP1 is low and the inverter INV is high, the first MOSFET M1 is turned on, the second MOSFET M2 is turned off, and capacitor C6 discharges. The voltage at the positive input terminal CMP2+ of the second comparator CMP2 gradually decreases. When the voltage at the positive input terminal CMP2+ of the second comparator CMP2 is less than the second reference VREF3, the output terminal CMP2_OUT of the second comparator CMP2 is low.

[0087] In a non-limiting embodiment, as previously described, reference is also made to... Figure 3 The switch control unit may include a first switch unit S1, a second energy storage unit C1, and a second switch unit S2.

[0088] In another non-limiting embodiment, as described above, reference is also made to... Figure 5 The switch control unit may include a first switch unit S1, a second energy storage unit C1, a second switch unit S2, and a third switch unit S3.

[0089] It should be noted that the first switching unit, the second switching unit, and the third switching unit can be single-pole single-throw switches or other implementable switching devices, such as transistors (PMOS). The second energy storage unit can also be other implementable energy storage devices. This embodiment of the invention does not impose any restrictions on these.

[0090] In one specific embodiment, the second switching unit S2 may include a third MOS transistor, the gate of which is coupled to the output terminal of the safety control unit 303, the drain of which is connected to the power supply VDD, and the source of which is grounded.

[0091] In another specific embodiment, reference is also made to Figure 9 The second switching unit S2 may include a third MOSFET M3, a fourth MOSFET M4, a fifth MOSFET M5, and a sixth MOSFET M6. The gate of the fourth MOSFET M4 is connected to a first control signal, and its source is connected to a first voltage HV. The gate of the fifth MOSFET M5 is connected to a second control signal, its source is grounded, and its drain is coupled to the drain of the fourth MOSFET M4. The gate of the sixth MOSFET M6 is connected to a second control signal, and its source is connected to a second voltage LV, which is less than the first voltage HV. When the third MOSFET M3 is turned on, the Vdd node can be grounded, thereby discharging the Vdd node voltage, i.e., discharging capacitor C1, to control the light emitting device L1 to stop emitting light.

[0092] The first voltage HV can be obtained by dividing the voltage of the power supply VDD. Specifically, it can be obtained by dividing the voltage using resistors R6 and R7. The voltage of the power supply VDD is usually relatively high, for example, 30V. The first voltage HV (e.g., 8V) is obtained by dividing the voltage using resistors R6 and R7. In order to achieve the rapid turn-on of the third MOSFET M3 (e.g., 5V conduction), it needs to be driven by the first voltage HV (gate voltage).

[0093] Furthermore, the second switching unit S2 may include a first driver 902 and a second driver 903. The input terminal of the first driver 902 receives a third control signal, and the output terminal of the first driver 902 outputs a first control signal to control the conduction of the fourth MOSFET M4; the input terminal of the second driver 903 is coupled to the output terminal of the safety control unit 303, and the output terminal of the second driver 903 outputs a second control signal to control the conduction of the fifth MOSFET M5.

[0094] Specifically, the first driver 902 and the second driver 903 may each include multiple inverters. Multiple inverters form a drive, enhancing the driving capability. When the output signal IN of the safety control unit 303 is low, the voltage of the output signal IN is 0V, the fifth MOSFET M5 is turned off, and the sixth MOSFET M6 is turned on; the input voltage of the first driver 902 is the second voltage LV, the fourth MOSFET M4 is turned on, thereby driving the third MOSFET M3 to turn on. The sixth MOSFET M6 prevents the gate of the third MOSFET M3 from being continuously subjected to the first voltage HV, causing it to fail. Instead, it allows the gate of the third MOSFET M3 to be subjected to the first voltage HV for a period of time, after which the voltage drops to the second voltage LV.

[0095] Specifically, when the voltage of the output signal IN is 0V, the fifth MOSFET M5 is turned off, the sixth MOSFET M6 is turned on, and the fourth MOSFET M4 is turned on, since the first voltage HV is higher than the second voltage LV, a current path is formed between the first voltage HV and the second voltage LV. Therefore, the gate of the third MOSFET M3 is first driven by the first voltage HV, and gradually becomes driven by the second voltage LV through discharge.

[0096] When the output signal IN of the safety control unit 303 is high, the voltage of the output signal IN is the second voltage LV, the fifth MOSFET M5 is turned on, the sixth MOSFET M6 is turned off, the input voltage of the first driver 902 is the first voltage HV, the fourth MOSFET M4 is turned off, thereby driving the third MOSFET M3 to turn off.

[0097] In one specific embodiment, continue to refer to Figure 9 The second switching unit also includes a level shifter 901. Specifically, the level shifter 901 can adopt a current mirror circuit to realize level shifting, that is, it can convert the output signal IN with a range of 0-LV into a third control signal with a range of LV-HV, so as to output to the first driver 902 to drive the fourth MOSFET M4 to turn on and off.

[0098] Specifically, when the voltage of the output signal IN at the output terminal of the safety control unit 303 is low, the output voltage of the level shifter 901 is the second voltage LV. When the voltage of the output signal IN at the output terminal of the safety control unit 303 is high, the output voltage of the level shifter 901 is the first voltage HV.

[0099] In this embodiment, the structure of the second switching unit S2 can improve the current capability of the third MOS transistor, thereby increasing the discharge speed of capacitor C1, thus shortening the time until the light emitting device stops emitting light after triggering the human eye safety protection mechanism, and further reducing the human eye safety risk caused by laser emission.

[0100] Please refer to Figure 10This invention also discloses a driving method for lidar. The driving method specifically includes the following steps:

[0101] Step 1001: Monitor the light emission energy of the light emitting device, and / or monitor the light emission time of the light emitting device;

[0102] Step 1002: When the luminous energy reaches the first threshold and / or the luminous time reaches the second threshold, control the light emitting device to stop emitting light.

[0103] It is understood that, in specific implementations, the driving method can be implemented using software programs, which run within a processor integrated into the chip or chip module. This method can also be implemented using a combination of software and hardware; this application does not impose any limitations on this approach.

[0104] In a specific implementation of step 1001, it is possible to monitor whether the voltage of the light emitting device reaches the light emission voltage threshold of the light emitting device.

[0105] This invention also discloses a lidar, which includes at least one light emitting device. The lidar emits detection beams through multiple light emitting devices. The lidar also includes the driving circuit described in any of the foregoing embodiments. The lidar can control the light emitting devices to emit light or stop emitting light through the driving circuit.

[0106] Furthermore, the lidar also includes multiple optical receiving devices; the multiple optical receiving devices are used to receive the echo beams reflected by the detection beams by the obstacles, and the multiple optical receiving devices are respectively arranged corresponding to the multiple optical emitting devices.

[0107] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article indicates that the preceding and following related objects have an "or" relationship.

[0108] In the embodiments of this application, "multiple" refers to two or more.

[0109] The descriptions of "first," "second," etc., appearing in the embodiments of this application are for illustrative purposes and to distinguish the objects being described. They have no order and do not indicate any special limitation on the number of devices in the embodiments of this application, nor do they constitute any limitation on the embodiments of this application.

[0110] In this application, the term "connection" refers to various connection methods, such as direct connection or indirect connection, to achieve communication between devices. This application does not impose any limitations on this.

[0111] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired or wireless means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media.

[0112] In the several embodiments provided in this application, it should be understood that the disclosed methods, apparatuses, and systems can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for example, the division of units is merely a logical functional division, and other division methods may exist in actual implementation; for example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0113] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0114] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can be physically comprised separately, or two or more units can be integrated into one unit. The integrated unit described above can be implemented in hardware or in the form of hardware plus software functional units.

[0115] The integrated unit implemented as a software functional unit described above can be stored in a computer-readable storage medium. This software functional unit, stored in a storage medium, includes several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute some steps of the methods described in the various embodiments of the present invention.

[0116] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A driving circuit for lidar, characterized in that, The lidar includes a light emitting device, and the driving circuit includes: The switch control unit includes: The second energy storage unit is used to input charge into the light emitting device to control the light emitting device to emit light, and A first switching unit is coupled to the light emitting device and the second energy storage unit, and is used to selectively control the light emitting device to emit light and stop emitting light using the second energy storage unit; The first monitoring unit, coupled to the second energy storage unit, is used to monitor the light emission energy of the light emitting device; A second monitoring unit is used to monitor the emission time of the light emitting device. The second monitoring unit and the first monitoring unit are respectively coupled to the two ends of the first switching unit; and A safety control unit is used to control the light emitting device to stop emitting light when the light emission energy reaches a first threshold and / or the light emission time reaches a second threshold, via the switch control unit.

2. The driving circuit according to claim 1, characterized in that, The second monitoring unit monitors whether the voltage of the light emitting device reaches the light emission voltage threshold of the light emitting device.

3. The driving circuit according to claim 1, characterized in that, Also includes: A first resistor is connected in parallel with the light emitting device, and the first resistor is used to discharge the light emitting device.

4. The driving circuit according to claim 1, characterized in that, Also includes: A logic control unit is configured to output a first control signal to the safety control unit when the luminous energy reaches a first threshold and / or the luminous time reaches a second threshold, and the safety control unit controls the light emitting device to stop emitting light based on the first control signal.

5. The driving circuit according to claim 1, characterized in that, The second monitoring unit includes: a first comparison subunit, configured to output a first voltage based on a comparison result between the voltage of the light emitting device and a first reference voltage, wherein the first voltage reflects the emission time of the light emitting device.

6. The driving circuit according to claim 5, characterized in that, The first comparison subunit includes: a first voltage divider subunit, used to divide the voltage of the optical emitting device; A first comparator, the positive input of which is coupled to the output of the voltage divider subunit, the negative input of which is connected to the first reference voltage, and the output of which outputs the first voltage.

7. The driving circuit according to claim 6, characterized in that, The first comparison subunit further includes: a first filtering subunit, coupled to the output terminal of the first voltage divider subunit, for filtering the voltage after voltage division.

8. The driving circuit according to claim 5, characterized in that, The second monitoring unit outputs a monitoring signal when it detects that the emission time has reached a second threshold. The second monitoring unit further includes a second comparison subunit, which is used to output the monitoring signal based on the comparison result between the first voltage and the second reference voltage.

9. The driving circuit according to claim 8, characterized in that, The second comparison subunit includes: a first energy storage subunit, used for charging or discharging according to the first voltage; The first control subunit outputs the monitoring signal when the voltage of the first energy storage subunit is greater than the second reference voltage.

10. The driving circuit according to claim 9, characterized in that, The first control subunit includes an inverter, the input of which is coupled to the output of the first comparison subunit; The first MOS transistor has its gate coupled to the output terminal of the inverter, its source grounded, and its drain coupled to the second terminal of the first energy storage sub-unit. The second MOS transistor has its gate coupled to the output terminal of the inverter, and its source is the second terminal of the first energy storage sub-unit. An adjustable current source, wherein the first terminal of the adjustable current source is connected to a power supply voltage, and the second terminal of the adjustable current source is coupled to the drain of the second MOS transistor; The second comparator has its positive input terminal coupled to the source of the second MOS transistor, its negative input terminal coupled to a second reference voltage, and its output terminal outputting the monitoring signal.

11. The driving circuit according to claim 1, characterized in that, The first monitoring unit monitors the voltage change of the second energy storage unit.

12. The driving circuit according to claim 11, characterized in that, The switch control unit includes: a second energy storage unit, wherein a first terminal of the second energy storage unit is connected to a power supply voltage, and a second terminal of the second energy storage unit is grounded; The first switching unit, wherein a first terminal of the first switching unit is coupled to a first terminal of the second energy storage unit, and a second terminal of the first switching unit is coupled to the light emitting device; and The second switching unit is used to selectively discharge the second energy storage unit.

13. The driving circuit according to claim 12, characterized in that, The first monitoring unit monitors whether the voltage at the first terminal of the second energy storage unit reaches the second threshold.

14. The driving circuit according to claim 12, characterized in that, The switch control unit further includes: a third switch unit, the first end of which is connected to the power supply voltage, the second end of which is coupled to the first end of the second energy storage unit, and the first end of the first switch unit, the second end of which is coupled to the anode of the light emitting device.

15. The driving circuit according to claim 12, characterized in that, The second switching unit includes: a third MOS transistor, the gate of which is coupled to the output terminal of the safety control unit, the drain of which is connected to the power supply voltage, and the source of which is grounded.

16. The driving circuit according to claim 12, characterized in that, The second switching unit includes: a fourth MOS transistor, the gate of which is connected to a first control signal, and the source of which is connected to a first voltage; The fifth MOS transistor has its gate connected to a second control signal, its source grounded, and its drain coupled to the drain of the fourth MOS transistor. The sixth MOS transistor has its gate connected to the second control signal and its source connected to a second voltage, which is less than the first voltage. The third MOS transistor has its gate coupled to the drain of the sixth MOS transistor and the drain of the fourth MOS transistor. The drain of the third MOS transistor is connected to the power supply voltage and is grounded.

17. The driving circuit according to claim 16, characterized in that, The second switching unit further includes: a first driver, wherein a third control signal is input to the input terminal of the first driver, and the first control signal is output to the output terminal of the first driver; The second driver has its input terminal coupled to the output terminal of the safety control unit, and its output terminal outputs the second control signal.

18. The driving circuit according to claim 17, characterized in that, The second switching unit further includes a level shifter, the input of which is coupled to the output of the safety control unit, and the output of which outputs the third control signal.

19. The driving circuit according to claim 1, characterized in that, The first monitoring unit includes: a second voltage divider subunit, used to divide the power supply voltage to output a voltage divider signal; Digital-to-analog converter, the digital-to-analog converter being used to provide a reference voltage; The third comparator has its negative input connected to the voltage divider signal and its positive input coupled to the output of the digital-to-analog converter.

20. The driving circuit according to claim 19, characterized in that, The first monitoring unit includes a second filtering subunit, coupled to the output terminal of the second voltage divider subunit, for filtering the voltage divider signal.

21. A driving method for a lidar, applied to the driving circuit according to any one of claims 1 to 20, characterized in that, The lidar includes a light emitting device, and the driving method includes: monitoring the light emission energy of the light emitting device, and / or monitoring the light emission time of the light emitting device; when the light emission energy reaches a first threshold, and / or the light emission time reaches a second threshold, controlling the light emitting device to stop emitting light.

22. The driving method according to claim 21, characterized in that, The monitoring of the light emission time of the light emitting device includes: monitoring whether the voltage of the light emitting device reaches the light emission voltage threshold of the light emitting device.

23. A lidar, characterized in that, The lidar includes a light emitting device and further includes the driving circuit described in any one of claims 1 to 20.

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