Electronic circuit and laser scanner

Abstract

Electronic circuit (1) for generating laser pulses for a laser scanner (2), with an input contact (3) for an input voltage, with at least one coil (L1) connected to the input contact (3), with at least one first diode (D1) connected in series with the coil (L1), wherein the first diode (D1) is connected in forward direction for the input voltage, characterized by the fact that at least one switching element (Q1) connected to the cathode of the first diode (D1) is arranged, where a switching path is formed by means of the switching element (Q1), wherein a laser trigger signal (12) can be applied to the gate of the switching element (Q1), wherein an anti-parallel circuit consisting of a laser diode (VCSEL) and a second diode (D2) is connected at one end to the cathode of the first diode (D1) and the switching element (Q1), wherein the antiparallel circuit of the laser diode (VCSEL) and the second diode (D2) is connected at the other end to at least one first capacitor (C1), and the first capacitor (C1) is connected to ground at the other end, wherein an optical laser pulse can be generated at the laser diode (VCSEL) by the laser trigger signal (12) at the switching element (Q1).

Description

[0001] The present invention relates to an electronic circuit for generating laser pulses for a laser scanner according to the preamble of claim 1 and a laser scanner according to the preamble of claim 11.

[0002] Typically, existing solutions offer either a highly fault-tolerant circuit with respect to laser Class 1 classification, eye safety, and unwanted laser emission due to component failure, or a more energy-efficient circuit, i.e., a ratio of input power from the power supply to the power supply of the laser diode. For low-power laser diodes, low energy efficiency is generally acceptable. In newer sensor applications using state-of-the-art, high-power laser diodes, low energy efficiency of the driver circuit can increase the overall power consumption of the sensor by approximately 30-40%. On the other hand, known solutions for more energy-efficient laser driver circuits are significantly more susceptible to component failures, which lead to unwanted laser light emission and thus most likely to violate the laser Class 1 limits.To prevent such a scenario, an increased need for appropriate security detection mechanisms is required, resulting in increased system complexity and higher manufacturing costs.

[0003] The invention provides a solution for an energy-efficient and highly fault-tolerant laser driver circuit to overcome this design compromise.

[0004] The following describes basic concepts of common laser driver circuits: Fig. Figure 1 shows a state-of-the-art high-side driver solution. This concept uses a high-side switching element to conduct a current through the laser diode. This can be an integrated or discrete solution. A short circuit of the driving switching element directly leads to unwanted laser light emission. The pulse width of the trigger signal also directly affects the emission time. Comprehensive detection mechanisms within the driver are required to ensure Class 1 laser compliance. Fig. Figure 2 shows a state-of-the-art resonant capacitive discharge laser driver. A widely used and frequently used laser driver circuit is based on a resonant design consisting of a capacitor, a laser diode, and a low-side switching element. Field-effect transistors are typically used. The capacitor is charged and stores the energy, usually for a single laser pulse. To emit laser light, the switching element is closed, and the capacitor's charge is conducted through the laser diode. The loop inductance of the current loop forms a resonant circuit with the capacitor, thus defining the pulse shape.

[0005] A simple and fault-tolerant way to charge the capacitor is to use a resistor between the input supply and the capacitor. Since the capacitor is almost completely discharged with each shot, the charging efficiency is always around 50%. This concept is still susceptible to short-circuit failure of the switching element. Although the current flow is limited by the resistor, unwanted laser light emission is still possible due to component failure. In practice, a variety of different precharging concepts and the arrangement of these components are used.

[0006] Fig. Figure 3 shows an improved low-side driver design based on a state-of-the-art single-transistor avalanche pulse design. To prevent unwanted laser light emission in the event of a short circuit of the switching element, the capacitance is precharged on the cathode side of the laser diode instead of the anode side.

[0007] An unusual component failure within this design cannot result in unwanted laser emission. The only way to violate the Class 1 laser limits is an incorrect input supply voltage and an incorrect laser trigger signal, for example, an incorrect pulse width and / or an incorrect repetition time. The additional diode in this circuit is optional. The use of this diode is intended to prevent unwanted ringing effects and has no general function related to precharging or laser light emission.

[0008] Fig. Figure 4 shows a state-of-the-art resonant laser driver with high-side boost circuit.

[0009] Another concept is the use of a boost converter topology as a charging circuit. An inductor, a diode, and an additional transistor are added. For precharging, the additional transistor is closed for a defined time. This time defines the voltage to which the capacitance is charged. After the transistor opens, the energy stored in the inductor is amplified within the capacitance by the added diode. An additional voltage is required at the cathode of the laser diode to prevent current from flowing through the laser diode at that moment to charge the transistor's drain-source capacitance. The input voltage is designed to be below the threshold to prevent laser light emission in the event of a short circuit of the switching element. However, this concept is highly susceptible to inaccurate timing of the charging signal and, in particular, to component tolerances.It can therefore be assumed that fast-reacting safety detection mechanisms are required for the application of laser class 1.

[0010] Other concepts are described in patents US11075502B2, US11631961 B2 and US10673204B2, which describe other possible circuits and solutions for driver circuits for laser diodes in a pulsed laser light application.

[0011] Existing solutions typically employ a highly fault-tolerant approach with respect to eye safety and unwanted laser emissions due to component failure. Existing solutions also typically exhibit low energy efficiency with respect to the input power from the power supply to the electrical power supply of the laser diode. Other solutions utilize circuits with higher energy efficiency but also with a higher susceptibility to component failure, thus increasing the need for safety detection mechanisms. The individual disadvantages of currently available solutions were previously discussed. Furthermore, most high-power applications require a high input supply voltage, for example, greater than 60 volts, necessitating additional measures to meet electrical safety standards within the overall system.

[0012] An object of the invention is to provide an improved driver circuit for laser diodes in a pulsed laser light application with a pulse width of a few nanoseconds and high pulse energy with high peak currents.

[0013] The object is achieved according to claim 1 by an electronic circuit for generating laser pulses for a laser scanner, having an input contact for an input voltage, having at least one coil connected to the input contact, having at least one first diode connected in series with the coil, wherein the first diode is connected in the forward direction for the input voltage, wherein at least one switching element connected to the cathode of the first diode is arranged, wherein a switching path is formed by means of the switching element, wherein a laser trigger signal can be applied to the gate of the switching element, wherein an anti-parallel circuit comprising a laser diode and a second diode is connected to the cathode of the first diode and the switching element at one end, wherein the anti-parallel circuit of the laser diode and the second diode is connected to at least one first capacitor at the other end,and the first capacitor is connected to ground at the other end, wherein an optical laser pulse can be generated at the laser diode by the laser trigger signal at the switching element.

[0014] After starting and applying a voltage to the input contact, the first capacitor is charged via the coil, the first diode and the second diode with an input voltage at the input contact.

[0015] The first capacitor is a single capacitor or a series of capacitors to temporarily store the energy required for a single laser shot.

[0016] The switching element is, for example, a switching element with a very fast switching time, capable of carrying a high peak current during the laser pulse, and withstanding a high charging voltage. The switching element is controlled by the external laser trigger signal or control signal at the control signal input. A low-side driver is preferably provided to drive the gate of the switching element used. The switching element conducts only for an extremely limited time when the external laser trigger signal is activated.

[0017] During the first pulse of the laser trigger signal, starting at a first time, the first capacitor is completely discharged through the laser diode and the switching element, generating a first lower laser pulse. At this moment, the voltage level of the laser diode cathode (corresponding to the drain terminal of the switching element) is the same as the ground reference, resulting in a voltage drop from the first capacitor to the switching element equal to the input voltage. A current begins to flow through the coil and the first diode.

[0018] After the switching element is closed, the current through the coil and the first diode continues to rise, charging the first capacitor to the voltage of the second diode, until the voltage level at the laser diode cathode reaches the input voltage at a second time and is now at the same voltage level as the input voltage. From then on, the current through the coil decreases until it reaches 0 amperes again at a third time. During this time, the first capacitor is still charged to a voltage level almost twice the input voltage.

[0019] After the third time, a negative current through the coil is prevented by the first diode, preventing the first capacitor from discharging through the laser diode and the coil. Under real-world conditions, only a slight oscillation remains, which, however, does not lead to unwanted illumination of the laser diode. The first capacitor stores the energy for the next laser pulse with a charging voltage of almost twice the input voltage until the laser trigger signal triggers the circuit again at a fourth time.

[0020] There is also a fundamental difference in the concept of how the switching element is used according to the invention. In a resonant laser driver with a high-side boost circuit and conventional boost converter circuits, the switching element is closed for as long as necessary to increase the current through the inductor, and the switching element is closed to increase the magnetic field within the inductor to a certain value to achieve a charging voltage that is several times the input voltage. By changing the time the switching element is closed, the stored charge on the first capacitor, or the charging voltage, can be controlled.

[0021] The switching element is closed for only a limited time, specifically an extremely limited time—a few nanoseconds—to release the laser light pulse. During this time, no significant current can build up through the inductance and the switching element. But the very short time the switching element is closed is sufficient for the voltage level of the laser diode cathode to be close to 0 volts, triggering the previously described charging current. As long as the switching element is not closed for much longer, the voltage across the first capacitor after charging is almost twice the input voltage, regardless of when the switching element was closed. This means, on the one hand, that the closing time of the switching element eliminates the possibility of directly controlling the charging voltage.On the other hand, it's not possible to generate a voltage higher than twice the input voltage, and thus the maximum energy per pulse is absolutely predictable. No additional safety mechanism, such as high-speed voltage sensing, is required. And the energy per pulse can still be controlled by changing the input supply voltage, which can be measured with a relatively slow voltage sensing.

[0022] To further improve susceptibility to an incorrect pulse width of the laser trigger signal, a coil or inductor can be used where the peak charging current through the coil is close to the saturation current of the inductor type. Even if the pulse width of the laser trigger signal is too large, the coil or inductor is unable to store more magnetic energy and thus prevent overcharging of the first capacitor. Furthermore, the current through the coil rises rapidly, and a simple power switch can detect such a fault situation.

[0023] The laser diode, for example, is a 5J VCSEL laser diode.

[0024] The main advantages of this invention are: A high charging efficiency of up to 97% compared to the conventional RC charging circuit at 50%. The overall efficiency, namely the electrical input power to optical output power, depends on the stated charging efficiency, the power conversion efficiency of the laser diode, and the discharging efficiency, which is primarily determined by the losses within the switching element used.

[0025] Harmful laser emission does not occur in typical component failures, such as a short circuit in the switching element, and thus, no safety detection mechanisms are required within the laser driver circuit. The integrity of the incoming power supply and the laser trigger signal must be ensured at the corresponding modules where they are generated. Hazardous laser light emission can only occur if an input signal is incorrect, i.e., an incorrect supply voltage or incorrect laser trigger signal is present.

[0026] A robust system is available against insufficient accuracy of the pulse width of the laser trigger signal.

[0027] There is no uncritical minimum pulse width and no uncritical switch-off behavior of the switching element.

[0028] Only a relatively low input voltage is required compared to the peak voltage required to generate laser shots. The high voltage is limited to the laser drive circuit, making it easier to meet the requirements of electrical safety standards.

[0029] Stable, repeatable pulse shapes are generated.

[0030] In a further development of the invention, at least one second capacitor connected in parallel to the input contact is arranged.

[0031] The second capacitor is a capacitor or, for example, several bulk capacitors with a much larger capacitance than the first capacitor in order to enable sufficient stabilization of the input voltage at the input contact.

[0032] In a further development of the invention, the switching element is in particular a switching transistor, in particular a field-effect transistor, very particularly a gallium nitride field-effect transistor.

[0033] In contrast to current-controlled bipolar transistors, field-effect transistors are voltage-controlled circuit elements. Control is achieved via the gate-source voltage, which serves to regulate the channel cross-section or charge carrier density—i.e., the semiconductor resistance—in order to switch or control the strength of an electric current.

[0034] Field-effect transistors are particularly suitable for switching high currents. Gallium nitride field-effect transistors are particularly suitable for switching high currents.

[0035] In a further development of the invention, the laser trigger signal is generated by a low-side FET driver. The low-side FET driver is an integrated electronic circuit that controls the power switch, i.e., the switching element.

[0036] A transistor driver, or low-side FET driver, is a circuit that provides the voltage needed to turn a transistor on or off within the required time. It is usually an amplifier with an additional level converter. This makes it possible to switch large loads such as field-effect transistors with a logic output, which is usually operated at 5 or 3.3 V. This driver can operate in analog or digital mode.

[0037] In a further development of the invention, the pulse width of the laser trigger signal is two to three times a calculated laser pulse width in order to ensure a completely discharged second capacitor.

[0038] During the first pulse of the laser trigger signal, starting at a first time, the first capacitor is completely discharged through the laser diode and the switching element, generating a first lower laser pulse. At this moment, the voltage level of the laser diode cathode is the same as the ground reference, resulting in a voltage drop from the second capacitor to the switching element equal to the input voltage. Choosing a pulse width of the laser trigger signal longer than the calculated laser pulse width ensures complete discharge of the first capacitor.

[0039] In a further development of the invention, the capacitance of the second capacitor is at least 500 times greater and in particular 1000 times greater than the capacitance of the first capacitor in order to enable sufficient stabilization of the input voltage at the input contact.

[0040] In a further development of the invention, the switching element is closed by the laser trigger signal for only 5 to 30 nanoseconds, in particular 15 to 20 nanoseconds, in order to release a laser pulse at the laser diode.

[0041] The further development relates to a driver circuit for laser diodes in a pulsed laser light application with a pulse width of a few nanoseconds, in particular 5 to 30 ns and high pulse energy, for example a few µJ per laser shot with high peak currents, for example greater than 100 amperes.

[0042] The switching element is closed for only an extremely limited time, namely a few nanoseconds, to release the laser light pulse. During this time, no significant current can build up through the inductance and the switching element.

[0043] But the very short time the switching element is closed is sufficient for the voltage level of the laser diode cathode to be close to 0 V, triggering the previously described charging current. As long as the switching element isn't closed much longer, the voltage across the capacitor after charging is almost twice the input voltage, regardless of when the switching element was closed. This means, firstly, that the ability to directly control the charging voltage is lost with the closing time of the switching element. Secondly, it's not possible to generate a voltage higher than twice the input voltage, and thus the maximum energy per pulse is absolutely predictable. No additional safety mechanism, such as high-speed voltage measurement, is required.And the energy per pulse can still be controlled by changing the input supply voltage, which can be measured with a relatively slow voltage measurement.

[0044] In a further development of the invention, the energy per laser pulse is adjusted by controlling the input supply voltage.

[0045] The energy per laser pulse can be easily adjusted, controlled or regulated using the input supply voltage used.

[0046] In a further development of the invention, the first capacitor, the laser diode and the switching element form a resonant discharge laser driver.

[0047] This refinement utilizes the principle of the resonant capacitive discharge laser driver and consists of a capacitor, a laser diode, and a switching element. Unlike the conventional solution, however, the charging circuit is connected to the cathode side of the laser driver, while the capacitor is still connected to the anode. To enable current flow for charging, an antiparallel diode is added. This modification overcomes the most critical failure of a short-circuited switching element.

[0048] In a further development of the invention, the coil, the first diode and the switching element form a boost converter circuit.

[0049] To overcome the comparatively low efficiency of 50% with a commonly used charging resistor, a circuit with a common boost converter topology consisting of an inductor, a diode, and a transistor is used. The high-speed switching element of the oscillating drive circuit is used, but it is only closed for a limited time, specifically an extremely limited time, so that, due to the circuit design, a voltage is generated that is only dependent on the input voltage and thus deterministic, which corresponds to almost twice the input voltage.

[0050] The object is further achieved according to claim 11 with a laser scanner having an electronic circuit according to claim 1. A laser scanner has at least one transmitting element and at least one receiving element, as well as a control and evaluation unit for evaluating the time of flight of light beams from the transmitting element via an object to the receiving element. The transmitting element has the laser diode.

[0051] In a further development of the invention, the laser scanner has at least one transmitting element and at least one receiving element, as well as a control and evaluation unit for evaluating the light propagation time of light beams from the transmitting element via an object to the receiving element. A plurality of transmitting elements and a plurality of receiving elements are arranged in a common housing, with the light beams being emitted and / or received in a fan-shaped pattern in different angular directions, with the spacing of the emitted light beams from the transmitting elements increasing with increasing distance from the laser scanner and / or the spacing of the received light beams from the receiving elements decreasing with decreasing distance from the laser scanner. The transmitting elements and receiving elements are arranged, for example, in a row. Angular deflection can be achieved via optics.

[0052] A preferred application is the use of the electronic circuit in a solid-state flash LiDAR sensor of laser class 1.

[0053] According to the further development, the light beams are emitted and received in a fan-shaped pattern in different angular directions, making it easy to examine a surveillance area to determine whether or not objects are present in the surveillance area and where, i.e. at what distance, the objects are present. Furthermore, the objects can be measured, or an environmental contour and any changes to it can be recorded. By emitting the light beams in a fan-shaped pattern and receiving them in a fan-shaped pattern, the surveillance area is monitored within a fan-shaped plane. The laser scanner can be manufactured with a high level of angular accuracy because the transmitting and receiving elements are firmly fixed and the light beams enter the surveillance area directly, without any moving parts. This ensures that every laser scanner adheres to a certain required minimum angular accuracy.

[0054] The laser scanner is therefore simple and inexpensive to construct. Since the laser scanner does not have any moving parts, it is subject to no mechanical wear and tear and has a long service life. For example, a required service life of approximately 20 years can be met with the laser scanner according to the invention.

[0055] Because the laser scanner does not require any moving parts, which can be subjected to acceleration during use in vehicles, for example, the laser scanner according to the invention is less sensitive to vibration and shock loads and can therefore be easily used in mechanically moving objects such as vehicles, especially industrial trucks. Because the laser scanner does not require any moving parts, it can also be designed very compactly.

[0056] In a further development of the invention, the laser scanner comprises at least one transmitting element and at least one receiving element, as well as a control and evaluation unit for evaluating the time of flight of light beams from the transmitting element via an object to the receiving element. A deflection unit is provided for deflecting the transmitted light beams from the transmitting element and / or for deflecting the received light beams for the receiving element.

[0057] The deflection unit means that only a single transmitting element and / or a single receiving element needs to be provided.

[0058] The invention will be explained below with reference to further advantages and features, using exemplary embodiments, with reference to the accompanying drawings. The figures of the drawing show: Fig. 1 a state-of-the-art high-side driver solution; Fig. 2 shows a resonant capacitive discharge laser driver according to the prior art; Fig. 3 an improved low-side driver design based on a state-of-the-art single-transistor avalanche pulse design; Fig. 4 a resonant laser driver with high-side boost circuit according to the state of the art; Fig. 5 an electronic circuit for generating laser pulses for a laser scanner; Fig. 6 an electronic circuit for generating laser pulses for a laser scanner; Fig. 7 a diagram of the occurring signals and voltages and currents; Fig. 8 a laser scanner.

[0059] In the following figures, identical parts are provided with identical reference numerals.

[0060] Fig. Figure 5 shows an electronic circuit 1 for generating laser pulses for a laser scanner, comprising an input contact 3 for an input voltage, at least one coil L1 connected to the input contact, at least one first diode D1 connected in series with the coil L1, wherein the first diode D1 is connected in the forward direction for the input voltage, at least one switching element Q1 connected to the cathode of the first diode D1 is arranged, a switching path being formed by means of the switching element Q1, a laser trigger signal 12 being able to be applied to the gate of the switching element Q1, an anti-parallel circuit comprising a laser diode VCSEL and a second diode D2 being connected at one end to the cathode of the first diode D1 and the switching element Q1, the anti-parallel circuit comprising the laser diode VCSEL and the second diode D2 being connected at the other end to at least one first capacitor C1.and the first capacitor C1 is connected to ground at the other end, wherein an optical laser pulse can be generated at the laser diode VCSEL by the laser trigger signal 12 at the switching element Q1.

[0061] For example, according to Fig. 6 at least one second capacitor C2 connected in parallel to the input contact 3 is arranged.

[0062] After starting and applying a voltage to input contact 3, the second capacitor C2 and the first capacitor C1 are charged via the coil L1, the first diode D1, and the second diode D2 with an input voltage at input contact 3. The first capacitor C1 is a single capacitor or a series of capacitors to temporarily store the energy required for a single laser shot. The second capacitor C2 is a capacitor or, for example, several bulk capacitors with a much larger capacitance than the first capacitor C1.

[0063] The switching element Q1 is, for example, a switching element Q1 with a very fast switching time, capable of carrying a high peak current during the laser pulse and withstanding a high charging voltage. The switching element Q1 is controlled by the external laser trigger signal 12 or the control signal at the control signal input 4. A low-side driver is preferably provided to drive the gate of the switching element Q1 used. The switching element Q1 conducts only for an extremely limited time when the external laser trigger signal 12 is activated with a positive level.

[0064] Fig. 7 shows a diagram of the occurring signals and voltages and currents. The diagram of Fig. Figure 6 shows the laser trigger signal 12, the current through coil L1, the voltage across the first capacitor C1, and the optical signal at the laser diode VCSEL. In particular, relevant times t1, t2, t3, and t4 are shown. VIN denotes the input voltage. Imax denotes a maximum current through coil L1.

[0065] During the first pulse of the laser trigger signal 12, starting at a first time t1 according to Fig. 6, the first capacitor C1 is completely discharged through the laser diode VCSEL and the switching element Q1, generating a first lower laser pulse. At this moment, the voltage level of the laser diode cathode (corresponding to the drain terminal of the switching element Q1) is the same as the ground reference, resulting in a voltage drop from the second capacitor C2 to the switching element Q1 equal to the input voltage. A current begins to flow through the coil L1 and the first diode D1.

[0066] After the switching element Q1 is closed, the current through coil L1 and the first diode D1 continues to rise, charging the first capacitor C1 to the voltage of the second diode D2, until the voltage level at the laser diode cathode reaches the input voltage at a second time t2 and is now at the same voltage level as the second capacitor C2. From then on, the current through coil L1 decreases until it reaches 0 amperes again at a third time t3. During this time, the first capacitor C1 is still charged to a voltage level almost twice the input voltage.

[0067] After the third time t3, a negative current through coil L1 is prevented by the first diode D1, so that the first capacitor C1 is not discharged through the laser diode VCSEL and coil L1. Under real conditions, only a slight oscillation remains, which does not lead to unwanted illumination of the laser diode VCSEL. The first capacitor C1 stores the energy for the next laser pulse with a charging voltage of almost twice the input voltage until the laser trigger signal 12 triggers the circuit again at a fourth time t4.

[0068] The switching element Q1 is closed for only an extremely limited time, namely a few nanoseconds, to release the laser light pulse. During this time, no significant current can build up through the coil L1 and the switching element Q1. However, the very short time in which the switching element Q1 is closed is sufficient for the voltage level of the laser diode cathode to be close to 0 volts, triggering the previously described charging current. As long as the switching element Q1 is not closed for much longer, the voltage across the first capacitor C1 after charging is almost twice the input voltage, regardless of when the switching element Q1 was closed. This means, firstly, that with the closing time of the switching element Q1, the possibility of directly controlling the charging voltage is lost.On the other hand, it's not possible to generate a voltage higher than twice the input voltage, and thus the maximum energy per pulse is absolutely predictable. No additional safety mechanism, such as high-speed voltage measurement, is required. And the energy per pulse can still be controlled by changing the input supply voltage, which can be measured with a relatively slow voltage measurement.

[0069] To further improve susceptibility to an incorrect pulse width of the laser trigger signal, an inductor L1 or inductor can be used, where the peak charging current through the inductor L1 is close to the saturation current of the inductor type. Even if the pulse width of the laser trigger signal is too large, the inductor L1 or inductor L1 is unable to store more magnetic energy and thus prevent overcharging of the first capacitor C1. Furthermore, the current through the inductor L1 rises rapidly, and a simple power switch can detect such a fault situation.

[0070] The VCSEL laser diode, for example, is a 5J VCSEL laser diode.

[0071] Preferably, the switching element Q1 is in particular a switching transistor, in particular a field effect transistor FET-Q1, very particularly a gallium nitride field effect transistor GaN-Q1.

[0072] Preferably, the laser trigger signal 12 is generated by a low-side FET driver. The low-side FET driver is an integrated electronic circuit that controls the power switch, i.e., the switching element Q1.

[0073] A transistor driver, or low-side FET driver, is a circuit that provides the necessary voltage to turn the switching element Q1 on or off within the required time. It is usually an amplifier with an additional level converter. This makes it possible to switch large loads such as field-effect transistors (FET-Q1) with a logic output, which is usually operated at 5 or 3.3 V. This driver can operate in analog or digital mode.

[0074] Preferably, the pulse width of the laser trigger signal 12 is two to three times a calculated laser pulse width in order to ensure a fully discharged first capacitor C1.

[0075] During the first pulse of laser trigger signal 12, starting at a first time t1, the first capacitor C1 is fully discharged through the laser diode VCSEL and the switching element Q1, generating a first lower laser pulse. At this moment, the voltage level of the laser diode cathode is the same as the ground reference, resulting in a voltage drop from the second capacitor C2 to the switching element Q1 equal to the input voltage. Choosing a pulse width of the laser trigger signal 12 longer than the calculated laser pulse width ensures complete discharge of the first capacitor C1.

[0076] Preferably, the capacitance of the second capacitor C2 is at least 500 times greater and in particular 1000 times greater than the capacitance of the first capacitor C1.

[0077] Preferably, the switching element Q1 is closed by the laser trigger signal for only 5 to 30 nanoseconds, in particular 15 to 20 nanoseconds, in order to release a laser pulse at the laser diode VCSEL.

[0078] The further development relates to a driver circuit for laser diodes VCSEL in a pulsed laser light application with a pulse width of a few nanoseconds, in particular 5 to 20 ns and high pulse energy, for example a few µJ per laser shot with high peak currents, for example greater than 100 amperes.

[0079] Preferably, the energy per laser pulse is adjusted by controlling the input supply voltage.

[0080] The energy per laser pulse can be easily adjusted, controlled or regulated using the input supply voltage used.

[0081] Preferably, the first capacitor C1, the laser diode VCSEL and the switching element Q1 form a resonant discharge laser driver.

[0082] However, unlike the conventional solution, the charging circuit is connected to the cathode side of the laser driver, while the capacitor is still connected to the anode. To enable current flow for charging, a second antiparallel diode D2 is added. This change overcomes the most critical failure of a short-circuited switching element.

[0083] Preferably, the coil L1, the first diode D1 and the switching element Q1 form a boost converter circuit.

[0084] To overcome the comparatively low efficiency of 50% with a commonly used charging resistor, a circuit with a common boost converter topology is used, consisting of the coil L1, the first diode D1, and the switching element Q1. The high-speed switching element of the oscillating drive circuit is used, but it is only closed for a limited time, specifically an extremely limited time, so that, due to the circuit design, a voltage is generated that is only dependent on the input voltage and thus deterministic, which corresponds to almost twice the input voltage.

[0085] Examples of concrete values ​​for the components are: C2 = 2x 4.7 uF (~ 10 uF) L1 = 6.8 µH D1 = NEXPERIA PMEG3010 (Schottky diode with low VF) Q1 = EPC EPC2088 (GaN Enhancement Mode Power Transistor) D2 = NEXPERIA PMEG3010 (Schottky diode with low VF) VCSEL = AMS TORONTO (800W 940nm 5J-VCSEL) C1 = 3x 3.9 nF ceramic capacitors (11.7 nF) Input voltage = 25-35 V Gate Driver = TI LMG1020

[0086] Fig. Figure 8 shows a laser scanner 2 with electronic circuits 1. The laser scanner 2 has at least one transmitting element 5 and at least one receiving element 6, as well as a control and evaluation unit 7 for evaluating the time of flight of light rays from the transmitting element 5 via an object to the receiving element 6. The transmitting element 5 has the VCSEL laser diode. Optional lenses 13 are arranged in front of the transmitting elements 5 and the receiving elements 6. For clarity, not all signal connections to the electronic circuits 1 are shown.

[0087] According to Fig.8, a plurality of transmitting elements 5 and a plurality of receiving elements 6 are arranged in a common housing 9, wherein the light beams 11 are emitted and / or received in a fan-shaped manner in different angular directions, wherein the distances between the emitted light beams of the transmitting elements 5 increase with increasing distance from the laser scanner 2 and / or the distances between the received light beams of the receiving elements 6 decrease with decreasing distance from the laser scanner 2. The transmitting elements 5 and receiving elements 6 are arranged, for example, in a row. Angular deflection can be achieved via optics. However, the transmitting elements 5 and receiving elements 6 can also be arranged in the shape of a segment of a circle.

[0088] A preferred application is the use of the electronic circuit 1 in a solid-state flash LiDAR sensor of laser class 1.

[0089] According to the further development, the light beams are emitted and received in a fan-shaped pattern in different angular directions, whereby a surveillance area can be easily examined to determine whether objects 8 are present in the surveillance area or not and at which location, i.e. at what distance, the objects 8 are present. Furthermore, the objects 8 can be measured, or an environmental contour and its changes can be recorded. By emitting the light beams 11 in a fan-shaped pattern or receiving them in a fan-shaped pattern, the surveillance area is monitored within a fan-shaped plane. The transmitting elements 5 and receiving elements 6 are arranged radially symmetrically around the circumference of a cylinder, for example. The laser scanner 2 can be manufactured with a high degree of angular accuracy because the transmitting elements 5 and receiving elements 6 are firmly fixed and the light beams 11 reach the surveillance area directly, without any moving parts.During production of the laser scanner 2, the angular accuracy of the angular directions can be checked and adjusted. This ensures that each laser scanner 2 maintains a certain required minimum angular accuracy.

[0090] For example, in an alternative embodiment, the laser scanner 2 comprises at least one transmitting element 5 and at least one receiving element 6, as well as a control and evaluation unit 7 for evaluating the time of flight of light beams 11 from the transmitting element 5 via an object 8 to the receiving element 6. A deflection unit is provided for deflecting the transmitted light beams of the transmitting element 5 and / or for deflecting the received light beams for the receiving element 6. The transmitting element 5 comprises the laser diode VCSEL.

[0091] Due to the deflection unit, only a single transmitting element 5 and / or a single receiving element 6 needs to be provided. Reference symbol: 1 Electronic circuit 2 laser scanners 3 Input contact 4 Control signal input 5 transmitting element 6 Receiving element 7 Control and evaluation unit 8 Object 9 housings 10 Deflection unit 11 rays of light 12 Laser trigger signal 13 lenses C1 first capacitor L1 coil D1 first diode Q1 switching element VCSEL laser diode D2 second diode C2 second capacitor FET-Q1 field-effect transistor GaN-Q1 gallium nitride field effect transistor QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 11075502B2

[0010] US 11631961 B2

[0010] US 10673204B2

[0010]

Claims

[1] Electronic circuit (1) for generating laser pulses for a laser scanner (2), with an input contact (3) for an input voltage, with at least one coil (L1) connected to the input contact (3), with at least one first diode (D1) connected in series with the coil (L1), wherein the first diode (D1) is connected in the forward direction for the input voltage, characterized by , that at least one switching element (Q1) connected to the cathode of the first diode (D1) is arranged, wherein a switching path is formed by means of the switching element (Q1), wherein a laser trigger signal (12) can be applied to the gate of the switching element (Q1), wherein an anti-parallel circuit comprising a laser diode (VCSEL) and a second diode (D2) is connected to the cathode of the first diode (D1) and the switching element (Q1) at one end, wherein the anti-parallel circuit of the laser diode (VCSEL) and the second diode (D2) is connected at the other end to at least one first capacitor (C1), and the first capacitor (C1) is connected to ground at the other end, wherein an optical laser pulse can be generated at the laser diode (VCSEL) by the laser trigger signal (12) at the switching element (Q1). [2] Electronic circuit (1) according to claim 1, characterized by that at least one second capacitor (C2) connected in parallel to the input contact (3) is arranged. [3] Electronic circuit (1) according to claim 1, characterized by that the switching element (Q1) is a switching transistor, in particular a field effect transistor (FET-Q1), in particular a gallium nitride field effect transistor (GaN-Q1). [4] Electronic circuit (1) according to one of the preceding claims, characterized bythat the laser trigger signal (12) is generated by a low-side driver. [5] Electronic circuit (1) according to claim 2, characterized by that the pulse width of the laser trigger signal (12) is two to three times a calculated laser pulse width in order to ensure a fully discharged first capacitor (C1). [6] Electronic circuit (1) according to claim 2, characterized by that the capacitance of the second capacitor (C2) is at least 500 times greater and in particular 1000 times greater than the capacitance of the first capacitor (C1). [7] Electronic circuit (1) according to one of the preceding claims, characterized by that the switching element (Q1) is closed by the laser trigger signal (12) for only 5 to 30 nanoseconds, in particular 15 to 20 nanoseconds, in order to release a laser pulse at the laser diode. [8] Electronic circuit (1) according to one of the preceding claims, characterized bythat the energy per laser pulse is adjusted by controlling the input supply voltage. [9] Electronic circuit (1) according to one of the preceding claims, characterized by that the first capacitor (C1), the laser diode (VCSEL) and the switching element (Q1) form a resonant discharge laser driver. [10] Electronic circuit (1) according to one of the preceding claims, characterized by that the inductance (L1), the first diode (D1) and the switching element (Q1) form a boost converter circuit, wherein the switching element (Q1) is closed only for a limited time, so that due to the circuit a voltage is generated which is only dependent on the input voltage and thus deterministic and which corresponds almost to twice the input voltage. [11] Laser scanner (2) with at least one transmitting element (5) and at least one receiving element (6) and a control and evaluation unit (7) for evaluating the light propagation time of light beams (11) from the transmitting element (5) via an object (8) to the receiving element (6) with an electronic circuit (1) according to one of claims 1 to 9. [12] Laser scanner (2) according to claim 11, characterized by in that a plurality of transmitting elements (5) and a plurality of receiving elements (6) are arranged in a common housing (9), wherein the light beams (11) are emitted and / or received in a fan-shaped manner in different angular directions, wherein the distances between the emitted light beams (11) of the transmitting elements (5) increase with increasing distance from the laser scanner (2) and / or the distances between the received light beams (11) of the receiving elements (6) decrease with decreasing distance from the laser scanner (2). [13] Laser scanner (2) according to claim 11, characterized by that a deflection unit (10) is provided for deflecting the transmitted light beams of the transmitting element (5) and / or for deflecting the received light beams for the receiving element (6).

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