Pulse Generator Circuit, Related Systems, and Methods

Abstract

Embodiments of the present disclosure relate to pulse generator circuits, related systems, and methods. An exemplary pulse generator circuit includes a first electronic switch coupled between a first node and a second node, and a second electronic switch coupled between the second node and a reference node. An LC resonant circuit including an inductor and a capacitor is coupled between the first node and the reference node, and a charging circuit arrangement includes another inductor in a current flow path between a power supply node and an intermediate node in the LC resonant circuit. During a sequence of switching cycles, a drive circuit arrangement of the electronic switches repeats a charging time interval, in which the capacitor in the LC resonant circuit is charged via the charging circuit, and a pulse generation time interval, in which a pulsed current is provided to a load via the first node and the second node. The charging time interval and the pulse generation time interval are interleaved with an oscillation time interval, in which the LC resonant circuit oscillates at a resonant frequency.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of Italian Application No. 102020000016396, filed Jul. 7, 2020, which is hereby incorporated herein by reference. Technical Field

[0003] This description relates to pulse generator circuits. One or more embodiments are suitable for a pulse generator circuit for driving a laser diode. Background Art

[0004] Pulse generator circuits can be used in various applications, such as power transistors and drivers, laser diode drivers, for example in LIDAR (Light Detection And Ranging or Laser Imaging Detection And Ranging) systems which are increasingly used in the automotive industry.

[0005] In the pulse generators discussed above, a resonant tank can be used to generate pulses, which includes a capacitor that is recharged during operation.

[0006] In recharging the resonant tank capacitor, short recharging times and limited power dissipation are thus desirable features of such pulse generators. Summary of the Invention

[0007] One or more embodiments can relate to related systems. For example, a LIDAR system for use in the automotive industry includes one or more laser diodes, which can be an example of such a system.

[0008] One or more embodiments can relate to related methods.

[0009] In one or more embodiments, the resonant tank capacitor can be charged using a charging inductor, which can significantly reduce power dissipation compared to resistive charging.

[0010] One or more embodiments can utilize the resonance of the charging inductor, which can involve controlling the value of the capacitor voltage at a certain moment at a voltage lower or higher than the supply voltage.

[0011] One or more embodiments contribute to the accurate and non-dissipative charging of the resonant tank capacitor used, for example, to generate sub-nanosecond current pulses in a laser for LIDAR applications.

[0012] One or more embodiments can include a voltage regulation block that has the function of charging the resonant tank capacitor in a fast and non-dissipative manner.

[0013] In one or more embodiments, the current flowing through the laser diode is linked to the charging voltage of the capacitor.

[0014] One or more embodiments may include a circuit topology (somewhat similar to a DC-DC converter) that can be synchronized with resonant tank activation. This is in contrast to a DC-DC converter topology that involves a closed loop with feedback on the output current and has the purpose of generating a constant current equal to the amplitude of the current flowing through an array of laser diodes (e.g., vertical cavity surface emitting lasers or VCSEL diodes).

[0015] One or more embodiments may provide one or more of the following advantages:

[0016] Low power dissipation, which contributes to miniaturization and efficiency,

[0017] Accurate charging control of the resonant tank,

[0018] Accurate control of the laser current,

[0019] Which contributes to integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The features and advantages of the embodiments will become apparent from the following detailed description of their actual implementation, shown by way of non-limiting examples in the drawings, wherein:

[0021] Figure 1 and Figure 2 is an exemplary circuit diagram of the resistive charging of a capacitor in a resonant tank in a pulse generator;

[0022] Figure 3 is a general exemplary circuit diagram of the non-dissipative charging of a capacitor in a pulse generator resonant tank;

[0023] Figure 4A is an exemplary circuit diagram of an open-loop implementation of the non-dissipative charging of a capacitor;

[0024] Figure 4B is in Figure 4A an illustrative diagram of the possible temporal behavior of signals that may occur in the implementation of;

[0025] Figure 5A is an exemplary circuit diagram of a closed-loop implementation of the non-dissipative charging of a capacitor;

[0026] Figure 5B is in Figure 5A an illustrative diagram of the possible temporal behavior of signals that may occur in the implementation of;

[0027] Figure 6A is an exemplary circuit diagram of a continuous current implementation of the non-dissipative charging of a capacitor;

[0028] Figure 6B is an illustrative diagram of the possible temporal behavior of signals that can occur in the implementation of Figure 6A ;

[0029] Figure 7A is an exemplary circuit diagram of the clamping and discontinuous inductor current implementation of the non-dissipative charging of a capacitor;

[0030] Figure 7B is an illustrative diagram of the possible temporal behavior of signals that can occur in the implementation of Figure 7A ; and

[0031] Figure 8 is a representation of a possible integration of a laser driver including a pulse generator circuit according to an embodiment of the present description. DETAILED DESCRIPTION

[0032] In the following description, for the purpose of enabling a deep understanding of the embodiments, various specific details are illustrated. Embodiments can be provided without one or more specific details, or other methods, components, materials, etc. can be used. In other cases, known structures, materials, or operations are not shown or described in detail so as not to obscure the various aspects of the embodiments.

[0033] In the framework of the present description, the reference to "an embodiment" or "one embodiment" means indicating that a specific configuration, structure, or feature described with respect to the embodiment is included in at least one embodiment. Thus, phrases such as "in an embodiment" or "in one embodiment" that can be represented at various points in the present description do not necessarily refer to the same embodiment. In addition, specific conformations, structures, or features can be combined in any appropriate manner in one or more embodiments.

[0034] The headings / references used herein are for convenience only and thus do not delimit the scope or extent of protection of the embodiments.

[0035] Throughout the drawings, the same parts, elements, or components are designated by the same reference numerals, and in order not to increase the burden of this detailed description, the detailed description of each drawing will not be repeated.

[0036] Similarly, in the present description, for simplicity, the same name can be used to indicate a certain circuit node or line and the signal appearing on that node or line.

[0037] Figure 1 An embodiment of a pulse generator circuit is shown, such as the circuit described in Italian Patent Application No. 102019000029132 and the corresponding US Patent Application No. 17 / 123,712.

[0038] Figure 1The figure illustrates a pulse generator circuit that serves as a driver circuit for a laser diode LD.

[0039] As shown in the figure, the pulse generator circuit includes a high-side electronic drive switch HSD and a low-side electronic drive switch LSD.

[0040] These switches can be transistors, such as field-effect transistors, preferably GaN (gallium nitride) transistors, because they can have switching times in the range of 100 ps.

[0041] The laser diode LD is generally an example of an electrical load that is intended to be applied a pulsed signal. Thus, the load exemplified by the laser diode LD can be an element different from the pulse generator.

[0042] As shown in the figure:

[0043] The high-side electronic drive switch HSD is coupled between a first node 10 and a second node 12.

[0044] The low-side electronic drive switch LSD is coupled between the second node 12 and a reference node (e.g., ground GND), and

[0045] The electrical load is coupled between the first node 10 and the second node 12.

[0046] In the exemplary case of the laser diode LD considered herein, the anode and cathode of the laser diode LD are respectively coupled to the first node 10 and the second node 12.

[0047] Two driver circuits 141, 142 are shown coupled to the control electrodes (the gate in the case of a field-effect transistor) of the switches HSD and LSD.

[0048] An LC resonant tank including an inductor Lr and a capacitor Cr connected in series is provided to be coupled between the first node 10 and the reference node GND.

[0049] As shown in the figure, the inductor Lr is arranged intermediate the first node 10 of the resonant tank circuit and an intermediate node 16, and the capacitor Cr is arranged intermediate the node 16 and the reference node GND.

[0050] A charging resistor Rcharge is coupled between a regulated voltage node at voltage VCC and the intermediate node 16 in the resonant circuit Lr, Cr.

[0051] The two driver circuits 141, 142 are configured to be operated so as to alternately turn on (switch closed and conducting) and turn off (switch open and non-conducting) the drive switches 141, 142, thereby applying drive pulses to the load (e.g., to produce pulsed laser operation of the laser diode LD) asFigure 1 shown schematically on the left - hand side, where the laser - activation LA and the resonator - tank - driving RTD are illustrated with reference to a common time (abscissa) scale t.

[0052] For example, Italian Patent Application No. 102019000029132 / US Patent Application No. 17 / 123,712 (cited) discloses a solution in which the driver circuit means 141, 142 are configured to cyclically repeat the following steps during a sequence of switching cycles:

[0053] For a first time interval, close the first electronic switch HSD and open the second electronic switch LSD, where the first node 10 and the second node 12 are short - circuited, and the capacitor Cr in the LC resonant circuit Lr, Cr is charged via a charging circuit;

[0054] For a following second time interval, close the first electronic switch HSD and close the second electronic switch LSD, where the first node 10 and the second node 12 are short - circuited, and the LC resonant circuit Lr, Cr oscillates at a resonant frequency (identified by the time constant Tr = 2π*(Lr*Cr) 1 / 2 );

[0055] For a following third time interval, open the first electronic switch HSD and close the second electronic switch LSD, where the LC resonant circuit Lr, Cr supplies a pulsed current to the load (here the laser diode LD) via the first node 10 and the second node 12; and

[0056] For a following fourth time interval, close the first electronic switch HSD and the second electronic switch LSD, where the first node 10 and the second node 12 are short - circuited, and the LC resonant circuit Lr, Cr oscillates at a resonant frequency.

[0057] In the circuit exemplified as Figure 1 shown, the current supplied by the LC resonant circuit Lr, Cr oscillates at a given maximum current value, and when the current supplied by the LC resonant circuit Lr, Cr reaches a threshold (maximum) current value, the driver circuit means 141, 142 can be controlled to start the third time interval.

[0058] In the circuit exemplified as Figure 1 shown, the duration of the second time interval can be selected in the range between 90% and 110% of a quarter of the resonant period of the LC resonant circuit Lr, Cr, preferably between 95% and 105%.

[0059] In the circuit exemplified as Figure 1 shown, the current supplied by the LC resonant circuit Lr, Cr oscillates at a maximum current value, and the associated control circuit means can be configured to:

[0060] Receive data indicating the requested current amplitude to be provided to two output terminals 10, 12; and

[0061] Determine the duration of a second time interval based on the data indicating the requested current amplitude.

[0062] In the circuit illustrated as Figure 1 shown, when the current provided by the LC resonant circuit Lr, Cr reaches zero, the associated control circuit means may be configured to start a first time interval.

[0063] It should be further understood that the embodiments herein mainly consider the charging control of the resonant tank Lr, Cr in a pulse generator, rather than having the operational details as previously recited, and thus no more detailed description is required herein.

[0064] As Figure 1 illustrated, the solution uses a resonant tank Lr, Cr to generate (very) fast current pulses to an electrical load, such as a laser diode (e.g., for LIDAR applications).

[0065] The current amplitude of the laser pulse is fixed by the energy stored in the resonant tank. Thus, the accurate control of the laser current pulse amplitude involves the time when the resonant tank is activated, controlling the amount of charge on the capacitor Cr. This in turn involves recharging the capacitor of the resonant tank with an exact voltage value when the resonant tank is activated.

[0066] Therefore, fast recharging plays a role in facilitating the activation of the laser LD at a high activation frequency.

[0067] Fast capacitor charging in turn hinders precise voltage control. Additionally, high-frequency charging can lead to high power dissipation in the charging circuit.

[0068] As Figure 1 illustrated, the capacitor is charged via a reference voltage source VCC and a resistor Rcharge.

[0069] The resistance value of Rcharge can be selected to be high enough to avoid interference with the resonant tank, where Vcc / Rcharge is (much) less than the peak current Ipeak.

[0070] Therefore, when it is desired to activate the laser at a high frequency, charging Cr can become a key factor: a small resistance value of Rcharge is beneficial for fast (re)charging, which in fact conflicts with the use of the resonant tank to combat interference as previously discussed.

[0071] As Figure 2 illustrated, the problem can be solved, where in association with Figure 1Related discussed parts, elements, or components are designated by the same reference symbols.

[0072] As Figure 2 Illustrated, the capacitor Cr is charged using a "commutating" resistor Rcharge, so that a small value of Rcharge can be used to obtain a fast charge of Cr without disturbing the resonant tank.

[0073] As Figure 2 Shown, the charging switch CS (which can also be a transistor such as a field effect transistor) is arranged between VCC and Rcharge. The switch CS can be controlled (i.e., made to alternately conduct and not conduct) by a corresponding driver circuit 143 coupled to the control electrode (the gate in the case of a field effect transistor) of the switch CSl.

[0074] As Figure 2 As represented by the left - hand side schematic, the driver 143 can be actuated in a synchronous manner with drivers 141 and 142, where the timing of the charging process CRC of Cr is exemplified with reference to a common time (abscissa) scale t together with the laser activation LA and the resonant tank drive RTD.

[0075] Figure 2 The solution can be advantageous because a low value of Rcharge contributes to a fast charge of Cr (e.g., 1 / (Rcharge*Cr) can be less than 3 * laser pulse frequency.

[0076] Additionally, when the switch CS is off, Rcharge has no effect on the resonant circuit.

[0077] Therefore, Figure 2 The solution illustrated in can be sufficient for laser pulse frequencies in the 100 kHz range.

[0078] Additionally, it can be noted that if, by virtue of Figure 2 the solution, Cr is resistively charged, the energy dissipated in the switch CS and Rcharge is essentially the same as the energy involved in charging the capacitor, which is equal to the energy lost during resonant tank activation. This results in the lost energy being equal to the energy dissipated in the switch CS and the energy lost in the resonant tank.

[0079] The power dissipation in the switch is equal to these lost energies multiplied by the resonant tank activation frequency (or the frequency of the laser pulse).

[0080] If it is envisaged that the laser activation frequency is in the range of 500 kHz, the power dissipation in the switch CS can be as high as several watts, and the power dissipation in the laser driver system is essentially doubled.

[0081] It should be noted that high power dissipation may be undesirable for various reasons:

[0082] Proper cooling may involve a large heat sink, where achieving good thermal coupling between the laser driver and the heat sink represents a key point.

[0083] Due to the high power dissipation concentration, it may be difficult to miniaturize the laser driver.

[0084] Since the total power dissipation of the laser driver may double (twice the energy dissipation in the resonant tank), the efficiency may be low.

[0085] For very high laser frequencies (e.g., 500 kHz), the power dissipation may become excessively high.

[0086] One or more embodiments may address the problems discussed above along the lines of the idea of a non-dissipative charging solution for Cr as illustrated by the general terms in Figure 3 .

[0087] In Figure 3 (and in the following figures), the same parts, elements, or components of the parts, elements, or components discussed in connection with Figure 1 and Figure 2 are designated by the same reference symbols, and for the sake of brevity, the corresponding detailed descriptions will not be repeated.

[0088] It should be noted that the embodiments herein mainly consider the charging control of the resonant tank Lr, Cr in the pulse generator, rather than other details of the circuit operation (opening / closing switches HSD and LSD): for the purposes herein, this circuit operation can be kept corresponding to the cyclic operation, including subsequent first, second, third, and fourth time intervals, as traced in connection with Figure 1 above.

[0089] In short, the circuit generally exemplified in Figure 3 may include drive circuitry (141, 142 – see also Figure 8 14 therein) for a first electronic switch HSD and a second electronic switch LSD, configured to repetitively cycle during a switch cycle sequence:

[0090] A charging time interval (see the first time interval traced previously in connection with Figure 1 ), where the first electronic switch HSD is closed and the second electronic switch LSD is open, and the capacitor Cr in the LC resonant circuit Lr, Cr is charged via a charging circuit 100;

[0091] A pulse generation time interval (following the charging time interval – see the Figure 1in combination with the third time interval (retrospectively), in which the first electronic switch HSD is open and the second electronic switch LSD is closed, and the LC resonant circuit Lr, Cr supplies a pulsed current towards the load (here the laser diode LD) via the first node 10 and the second node 12.

[0092] The oscillation time interval (see previously in combination with Figure 1 the second and fourth time intervals (retrospectively)) is interleaved with the charging time interval and the pulse generation time interval; in the oscillation time interval, both the first electronic switch HSD and the second electronic switch LSD are closed, and the LC resonant circuit Lr, Cr oscillates at the resonant frequency.

[0093] In Figure 3 the solution schematically illustrated in, the capacitor Cr in the resonant tank is charged using the switching circuit 100, which can essentially be similar to a DC-DC converter coupled between the node VCC and the node 16 for the purpose of recharging the capacitor Cr with minimum power dissipation.

[0094] References to DC-DC converters indicate that a person skilled in the art can use any known DC-DC converter topology (buck, boost, buck-boost, resonant, to mention only a few examples) as a model for the circuit 100, and furthermore, it can be understood that the circuit 100 embodies a specific topology that can be synchronized with the activation of the resonant tank.

[0095] In this regard, it should be noted that although certainly advantageous, synchronous operation (i.e., synchronizing the PWM signal with the resonant tank activation frequency) is not mandatory; furthermore, the switching frequency can be different from the resonant tank activation frequency. In fact, it is possible to generate a charging current for Cr with a frequency different from (e.g., higher than) the resonant tank activation frequency, as this does not involve synchronization with the resonant tank.

[0096] For the purposes of this document, it can essentially be noted that in Figure 3 the drive circuit means (141, 142 - see also 14 in Figure 8 is configured to act on the first electronic switch HSD and the second electronic switch LSD in order to repeat the switching cycle including the charging time interval (see previously in combination with Figure 1 the first time interval (retrospectively)), in which the first electronic switch HSD is closed and the second electronic switch LSD is open, and the capacitor Cr in the LC resonant circuit Lr, Cr is charged using an inductor (L Charge) capable of resonating with the capacitor.

[0097] The manner considered herein is suitable for being implemented according to different options. These different options can be synchronized with the resonator tank activation in order to facilitate reaching a desired value of the charging voltage VCr on the capacitor Cr in coordination with the resonator tank (theoretically, at the exact moment when the resonator tank is activated).

[0098] The following various such options will be discussed:

[0099] Non-dissipative charging control of Cr in open loop ( Figure 4A and Figure 4B );

[0100] Non-dissipative charging control of Cr in closed loop ( Figure 5A and Figure 5B );

[0101] Non-dissipative charging control of Cr with continuous current ( Figure 6A and Figure 6B );

[0102] Non-dissipative charging control of Cr with clamped and discontinuous inductor current ( Figure 7A and Figure 7B );

[0103] First turning to non-dissipative charging control of Cr in open loop, Figure 4A FIG. illustrates a charging switch circuit 102 including an H (half) - bridge, which H (half) - bridge includes a first electronic switch 102a and a second electronic switch 102b (as described, these can be transistors such as field - effect transistors, for example, like GaN transistors).

[0104] Switches 102a, 102b are alternately driven on and off (in the case of field - effect transistors, see converter 102c coupled to the control electrode (gate of switch 102b)) to drive an inductor (LCharge) with a square - wave voltage Vswitch, which inductor is coupled between the mid - point 106 of the bridge and the capacitor Cr.

[0105] As illustrated, by comparing the charging voltage of Cr (i.e., VCr) with a threshold voltage generated in a manner known per se (a fixed threshold 108 in the Figure 4B illustrated case), comparator 104 can generate a (PWM - modulated) square - wave voltage to drive the switch circuit 102 so that the PWM signal is synchronized with the resonator tank activation.

[0106] The value of LCharge can be selected such that the average current Icharge through the inductor LCharge is greater than 0, where the ripple is less than the average value, thereby obtaining current control in continuous mode.

[0107] Thus, the capacitor Cr is charged using the current Icharge, where the value of Icharge (and thus the charging speed of Cr) is a function of the threshold voltage 108. Since the resonant tank activation frequency is constant, the value of V Cr at the moment when the resonant tank is activated (i.e., the charging voltage of Cr) will be a function of the (fixed) voltage threshold 108.

[0108] Figure 4B The diagrams of, with reference to a common abscissa time scale, illustrate the possible time behaviors:

[0109] The voltage V Cr across Cr, plotted with reference to the threshold 108 and the desired charging voltage Cr CV (upper diagram), and

[0110] The charging current Icharge, plotted with reference to the on - off cycle of Vswitch (lower diagram, where the resonant tank activation is verified at RTA).

[0111] It can be noted that after several cycles after startup, the charging switch 102 is synchronized with the resonant tank activation, and the value of V Cr remains substantially stable when the tank is activated.

[0112] In the arrangement as Figure 4A illustrated, the turn - off threshold and component values can be designed so as to have a resonator voltage equal to VCC at ignition activation.

[0113] In the arrangement as Figure 4A illustrated, the charging inductor L Charge operates in continuous conduction mode.

[0114] For example, the peak current in the charging inductor can be 1.6 A, with an average value of 1.3 A, which is sufficient to recharge the resonator Lr, Cr in the applications discussed above.

[0115] These are of course only exemplary values, mentioned without limiting the intention of the embodiments.

[0116] Figure 5A and Figure 5B with reference to the non - dissipative charging control of Cr in a closed - loop configuration.

[0117] Figure 5A The circuit of is substantially the same as Figure 4A the circuit of, except that a variable threshold 108’ is introduced in order to define the value of the Cr charging voltage via the comparator 104.

[0118] A variable threshold 108’ can be generated (in a manner known per se) such that it is linked to (closed-loop) feedback parameters, commonly denoted as FB. For example, these feedback parameters can include V Cr itself or parameters linked to V Cr, such as - by way of example - the current in the resonant tank and / or the power emitted by the laser diode.

[0119] The variable threshold such as 108’ facilitates the continuous regulation of Vcr and / or defines a calibration procedure.

[0120] Figure 5B The diagrams, referring to a common abscissa time scale, illustrate possible time behaviors:

[0121] The voltage V Cr across Cr, plotted with reference to the threshold 108’ and the desired charging voltage Cr CV (upper diagram), and

[0122] The charging current Icharge, plotted with reference to the on-off cycle of Vswitch (lower diagram, where the activation of the resonant tank is verified at RTA).

[0123] In the arrangement illustrated as in Figure 5A the closed-loop regulation turns off the threshold so that the resonator voltage equals VCC upon ignition activation.

[0124] In the arrangement illustrated as in Figure 5A the charging inductor L Charge operates again in continuous conduction mode.

[0125] Here again, the peak current in the recharge inductor can be 1.6 A, with an average value of 1.3 A. As described, this is sufficient for the recharge resonator Lr, Cr in the applications described above.

[0126] Similarly, these are merely exemplary values, mentioned without limiting the intent of the embodiments.

[0127] Figure 6A and Figure 6B refers to the non-dissipative charging control of Cr with continuous current in a circuit configuration using only the charging inductor (i.e., L Charge) coupled between VCC and Cr.

[0128] The inductor L Charge resonates with the capacitor Cr, where oscillations are generated by the activation of the resonant tank.

[0129] In the circuit illustrated as in Figure 6A the inductance value of the inductor L Charge can be selected such that the resonance frequency of the LC resonator including LCharge and Cr is (far) lower than the resonant tank activation frequency. Thus, the current in the inductor will flow again in continuous mode.

[0130] This choice of the inductance value of the inductor L Charge can also be advantageous for other implementations illustrated herein.

[0131] Figure 6A The diagrams of illustrate possible time behaviors with reference to a common abscissa time scale:

[0132] The voltage V Cr across Cr, plotted with reference to the voltage VCC (upper diagram), and

[0133] the charging current Icharge (lower diagram, where the resonant tank activation is verified at RTA).

[0134] Figure 6A shows that, after several resonant tank activation cycles, the value of V Cr reaches a steady value at the moment of resonant tank activation.

[0135] In a configuration such as illustrated in Figure 6A a value of VCC = 6V can result in a resonator voltage equal to 11V at ignition activation.

[0136] Additionally, in this case, the recharge inductor operates in continuous conduction mode, where the possible values of the peak current and the average current are respectively equal to 1.66 and 1.58, also properly charging the resonator.

[0137] Once again, these figures are only exemplary values, mentioned without limiting the intent of the embodiments.

[0138] Figure 7A and Figure 7B refer to Cr non-dissipative charge control with clamped and discontinuous inductor current.

[0139] By direct comparison with Figure 2 in a solution such as illustrated in Figure 7A the charging inductor L Charge is controlled for charging by a charging switch CS (which can be, for example, a combination of an H (half) bridge or an electronic switch and a recycling diode D1).

[0140] As illustrated in b of Figure 7A the clamping diode D2 is connected between the capacitor Cr and the regulated voltage VCC.

[0141] The clamping diode D2 helps to recover the excess energy to the reference voltage.

[0142] When the switch CS is off (non-conductive), the diode D1 helps with the (re)circulation of the current in the inductor L Charge.

[0143] In a solution such as illustrated in Figure 7AIn the solution illustrated, the value of the charging inductor LCharge can be determined such that the resonant frequency identified by LCharge and Cr is approximately 4 times the frequency corresponding to the desired charging time of the capacitor (i.e., the charging voltage reaches the desired peak at 1 / 4 of the resonant frequency).

[0144] This helps to charge the capacitor Cr in a time that is essentially 1 / 4 of the resonant period (the charging time should desirably be lower than or equal to the activation frequency of the resonant tank).

[0145] For example, the value of Vcr can reach Vcro + 2 x (VCC - Vcro), where Vcro is the value of Vcr when the charging switch CS is activated.

[0146] When using a regulated clamping voltage that is less than Vcro + 2 x (VCC - Vcro), the charging value of Vcr will reach the regulated value and be clamped by that value.

[0147] Figure 7B The diagrams of

[0148] the voltage VCr across Cr, plotted with reference to the clamping voltage CV (upper diagram), and

[0149] the charging current Icharge, plotted with reference to the on - off cycle of Vswitch (lower diagram, where the activation of the resonant tank is verified at RTA), illustrate the possible time behavior with reference to a common abscissa time scale.

[0150] As Figure 7A illustrated in

[0151] the solution helps to set the value of VCr within one cycle.

[0152] Figure 8 is a diagram that illustrates the possible circuit integration, for example, in a LIDAR system for automotive use, of the previously discussed ( Figure 6A the solution of

[0153] In Figure 8 the reference numeral 14 indicates the high - side and low - side drive switches HSD and LSD as a whole, integrated with the driver circuits previously designated as 141, 142 and the associated controller circuitry configured to receive a (differential) input signal between the input nodes INH and INL. Such an integrated component can be powered by the supply voltage VCC.

[0154] Italian Patent Application No. 102019000029132 / US Patent Application No. 17 / 123,712 (cited repeatedly) discloses an arrangement including a resonant tank, e.g., Lr, Cr, and two switches. When the two switches are turned on (conductive), the resonant tank exchanges the energy stored in Cr with the energy stored in Lr. When Vcr = 0, the energy and current in Lr reach their maximum values. When the HSD switch (in parallel with the load - here the diode LD) is turned off, the current flowing in Lr will flow into the load, and the switching speed (di / dt) will depend on the inductance in the relevant commutation loop.

[0155] This topology allows for very low inductance because the commutation loop including (only) the switches and the load can be very short, and the associated stray inductance can be reduced to below the 100 pH range.

[0156] Figure 8 It is illustrated that the solution as disclosed herein further helps to have a "short" commutation loop (enclosed by the dashed line) between the high - side driving switch HSD and the laser diode LD and a "long" resonant loop Lr, Cr, where LCharge is coupled between the resonant tank and the regulated voltage VCCreg.

[0157] Compared with the resistive solution as Figure 1 and Figure 2 illustrated therein, the inductive charging circuit arrangement as illustrated herein is found to reduce the power dissipation involved in the recharge of the resonant tank capacitor Cr by more than 10 times while retaining the possibility of achieving the peak current I Peak value, where the peak current I Peak is a function of VCCreg*(Cr / Lr) 1 / 2 and the oscillation time constant Tr of the resonant tank is given by 2π*(Lr*Cr) 1 / 2 .

[0158] In fact, the corresponding integrated circuit (IC) can include the control of the resonant tank, with laser activation, along with the charging control. This helps to control the amplitude of the current in the laser.

[0159] In a conventional topology, it is basically infeasible to measure the current in the laser due to the difficulty in achieving reliable current sensing with a 1 ns response time.

[0160] The IC contemplated herein can i) measure the current in the resonant tank in the frequency range of 2 MHz (Tr = 500 ns), and based on this measurement, ii) generate a feedback signal to control V Cr, where V Cr is linked to the maximum value of the current I Lr in the inductor Lr (the current is such that the load LD cannot exceed I Lr ).

[0161] An inductive charging circuit device as exemplified herein can contribute to the control of L Charge and Cr resonance and a well-controlled charging voltage for Cr.

[0162] Relying on resonance, a control voltage can be provided higher or lower than the power supply voltage, where the circuit operates a buck-boost converter.

[0163] The continuous current operation of L Charge can contribute to reducing the peak current in the charging switch so that such a charging switch can be easily integrated in an IC, which in turn contributes to integrating the Cr charging control circuit device in a laser driver IC.

[0164] For example, a circuit device as exemplified herein can contribute to a compact implementation of a 4-channel laser driver and integrated gallium nitride (GaN) transistors in a PCB layout.

[0165] A pulse generator circuit as exemplified herein can include:

[0166] A first node (e.g., 10) and a second node (e.g., 12) configured to apply a pulse signal to an electrical load (e.g., LD) coupled therebetween;

[0167] A first electronic switch (e.g., HSD) coupled between the first node and the second node;

[0168] A second electronic switch (e.g., LSD) coupled between the second node and a reference node (e.g., GND);

[0169] An LC resonance circuit (e.g., Lr, Cr) including an inductor (e.g., Lr) and a capacitor (e.g., Cr) connected in series with an intermediate node (e.g., 16) therebetween, and the LC resonance circuit is coupled between the first node and the reference node;

[0170] A charging circuit device (e.g., 100) coupled between a power supply node (e.g., VCC) and the intermediate node in the LC resonance circuit.

[0171] A drive circuit device (e.g., 14, 141, 142) for the first electronic switch and the second electronic switch, the drive circuit device being configured to repeat switching cycles in a sequence of switching cycles including a charging time interval in which the first electronic switch closes and the second electronic switch opens, and the capacitor in the LC resonance circuit is charged via the charging circuit device,

[0172] wherein the charging circuit device includes another inductor (e.g., L Charge) in a current flow line between the power supply node and the intermediate node in the LC resonance circuit.

[0173] In a pulse generator circuit as exemplified herein, the charging circuit means may consist of (only) another inductor in the current flow path between the power supply node and the intermediate node in the LC resonant circuit.

[0174] In a pulse generator circuit as exemplified herein,

[0175] the drive circuit means of the first electronic switch and the second electronic switch may be configured to activate the LC resonant circuit at an activation frequency,

[0176] the other inductor and capacitor in the LC resonant circuit may resonate at a resonance frequency lower than the activation frequency of the LC resonant circuit.

[0177] In a pulse generator circuit as exemplified herein, the charging circuit means may include:

[0178] a comparator (e.g., 104), configured to perform a comparison between the charging voltage (e.g., V Cr) of the capacitor in the LC resonant circuit and a charging threshold (e.g., 108, 108’), and

[0179] a charging switch (e.g., 102), arranged in the current flow path between the power supply node and the other inductor, and the charging switch may be activated according to the comparison result at the comparator to couple the other inductor to the power supply node.

[0180] In a pulse generator circuit as exemplified herein, the charging threshold may include a variable threshold (e.g., 108’).

[0181] In a pulse generator circuit as exemplified herein, the variable threshold may be variable according to the charging voltage of the capacitor in the LC resonant circuit or a parameter linked thereto.

[0182] In a pulse generator circuit as exemplified herein, the charging circuit means may include:

[0183] a charging switch (e.g., 102), arranged in the current flow path between the power supply node (e.g., VCCreg) and the other inductor, and the charging switch (e.g., 143) can be controllably activated to couple the other inductor to the power supply node,

[0184] a clamping diode (e.g., D2), connected between the power supply node and the intermediate node (e.g., 16) in the LC resonant circuit.

[0185] In a pulse generator circuit as exemplified herein, the inductor (e.g., Lr) and capacitor (e.g., Cr) in the LC resonant circuit may be respectively coupled to:

[0186] between the first node and the intermediate node, and

[0187] Between the intermediate node and the reference node.

[0188] A pulse operating system as exemplified herein (i.e., a system configured for pulse operation) may include:

[0189] A pulse generator circuit as exemplified herein, and

[0190] An electrical load (e.g., an LD), coupled between a first node and a second node.

[0191] In a pulse operating system as exemplified herein, the electrical load may include one or more laser diodes (e.g., an LD).

[0192] A method of operating a pulse generator circuit or a pulse operating system as exemplified herein may include cyclically driving a first electronic switch and a second electronic switch during a switching cycle sequence:

[0193] A charging time interval, in which the first electronic switch is closed and the second electronic switch is open, and the capacitor in the LC resonant circuit is charged via a charging circuit.

[0194] A pulse generation time interval, in which the first electronic switch is open and the second electronic switch is closed, and the LC resonant circuit provides a pulsed current to the electrical load via the first node and the second node.

[0195] An oscillation time interval is interleaved with the charging time interval and the pulse generation time interval; wherein in the oscillation time interval, both the first electronic switch and the second electronic switch are closed, and the LC resonant circuit oscillates at a resonant frequency.

[0196] Without prejudice to the basic principles, the details of the construction and embodiments may vary widely from what is purely described and illustrated herein by way of example, without thereby departing from the scope of the embodiments.

[0197] The extent of protection is determined by the appended claims.

Claims

1. A pulse generator circuit, comprising: A first node and a second node, configured to apply a pulse signal to an electrical load coupled between the first node and the second node; A first electronic switch, coupled between the first node and the second node; A second electronic switch, coupled between the second node and a reference node; An LC resonant circuit, including an inductor and a capacitor connected in series, having an intermediate node between the inductor and the capacitor, the LC resonant circuit being coupled between the first node and the reference node; A charging circuit arrangement, including another inductor in a current flow path between a power supply node and the intermediate node in the LC resonant circuit; and Driver circuit means for the first electronic switch and the second electronic switch, the driver circuit means being configured to repeat switching cycles in a switching cycle sequence, the switching cycle sequence including: A charging time interval, in which the first electronic switch is closed and the second electronic switch is open, and the capacitor in the LC resonant circuit is charged via the charging circuit; Wherein the charging circuit arrangement includes: A comparator, configured to perform a comparison of a charging voltage of the capacitor in the LC resonant circuit with a charging threshold; and A charging switch, arranged in the current flow path intermediate the power supply node and the other inductor, the charging switch being activatable according to a result of the comparison at the comparator to couple the other inductor to the power supply node; Wherein the driver circuit means for the first electronic switch and the second electronic switch activates the LC resonant circuit at an activation frequency; and The capacitor and the other inductor in the LC resonant circuit resonate at a frequency lower than the activation frequency of the LC resonant circuit.

2. The pulse generator circuit according to claim 1, wherein the switching cycle sequence further comprises: A pulse generation time interval, in which a pulse current is provided to the electrical load via the first node and the second node, and An oscillation time interval, interleaved with the charging time interval and the pulse generation time interval, in which the LC resonant circuit oscillates at a resonant frequency.

3. The pulse generator circuit according to claim 2, wherein the drive circuit means is configured to activate the LC resonant circuit at the activation frequency higher than the resonant frequency during the oscillation time interval.

4. The pulse generator circuit according to claim 1, wherein the charging threshold includes a variable threshold.

5. The pulse generator circuit according to claim 4, wherein the variable threshold is variable according to the charging voltage of the capacitor in the LC resonant circuit or a parameter associated with the charging voltage.

6. The pulse generator circuit according to claim 1, wherein the charging circuit means comprises: A charging switch, arranged in the current flow path intermediate the power supply node and the other inductor, the charging switch being controllably activatable to couple the other inductor to the power supply node; And A clamping diode, connected between the power supply node and the intermediate node in the LC resonant circuit.

7. The pulse generator circuit according to claim 1, wherein: The inductor in the LC resonant circuit is coupled between the first node and the intermediate node; and The capacitor in the LC resonant circuit is coupled between the intermediate node and the reference node.

8. A pulse operating system, comprising: A pulse generator circuit, including: A first node and a second node, configured to provide a pulse signal; A first electronic switch, coupled between the first node and the second node; A second electronic switch, coupled between the second node and a reference node; An LC resonant circuit, including an inductor and a capacitor connected in series, having an intermediate node between the inductor and the capacitor, the LC resonant circuit being coupled between the first node and the reference node; A charging circuit device, including another inductor in a current flow path between a power supply node and the intermediate node in the LC resonant circuit; and Drive circuit means for the first electronic switch and the second electronic switch, the drive circuit means being configured to repeat switching cycles in a switching cycle sequence, the switching cycle sequence including: A charging time interval, in which the first electronic switch is closed and the second electronic switch is open, and the capacitor in the LC resonant circuit is charged via the charging circuit; and An electrical load, coupled between the first node and the second node; Wherein the charging circuit device includes: A comparator, configured to perform a comparison of the charging voltage of the capacitor in the LC resonant circuit with a charging threshold; and A charging switch, arranged in the current flow path between the power supply node and the other inductor, the charging switch being activatable according to the result of the comparison at the comparator to couple the other inductor to the power supply node; Wherein the drive circuit means for the first electronic switch and the second electronic switch activates the LC resonant circuit at an activation frequency; and The capacitor and the other inductor in the LC resonant circuit resonate at a frequency lower than the activation frequency of the LC resonant circuit.

9. The pulsed operating system according to claim 8, wherein the electrical load includes at least one laser diode.

10. The pulsed operating system according to claim 8, wherein the switching cycle sequence further includes: A pulse generation time interval, in which a pulsed current is provided to the electrical load via the first node and the second node, and An oscillation time interval, interleaved with the charging time interval and the pulse generation time interval, in which the LC resonant circuit oscillates at a resonant frequency.

11. The pulsed operating system according to claim 10, wherein the drive circuit means is configured to activate the LC resonant circuit at an activation frequency higher than the resonant frequency of the LC resonant circuit.

12. The pulsed operating system according to claim 8, wherein the charging threshold includes a variable threshold.

13. The pulsed operating system according to claim 12, wherein the variable threshold is variable according to the charging voltage of the capacitor in the LC resonant circuit or a parameter associated with the charging voltage.

14. The pulsed operating system according to claim 8, wherein the charging circuit means includes: A charging switch, arranged in the current flow path between the power supply node and the other inductor, the charging switch being controllably activatable to couple the other inductor to the power supply node; And A clamping diode, connected between the power supply node and the intermediate node in the LC resonant circuit.

15. The pulsed operating system according to claim 8, wherein: The inductor in the LC resonant circuit is coupled between the first node and the intermediate node; and The capacitor in the LC resonant circuit is coupled between the intermediate node and the reference node.

16. A method of operating a pulse generator circuit, the pulse generator circuit including: A first node and a second node; A first electronic switch, coupled between the first node and the second node; A second electronic switch, coupled between the second node and the reference node; drive circuit means for the first electronic switch and the second electronic switch; An LC resonant circuit, the LC resonant circuit including an inductor and a capacitor connected in series, having an intermediate node between the inductor and the capacitor, the LC resonant circuit being coupled between the first node and the reference node; And a charging circuit device, the charging circuit device including another inductor in a current flow path between a power supply node and the intermediate node in the LC resonant circuit, the method including cyclically repeating during a switching cycle sequence: During a charging time interval, closing the first electronic switch and opening the second electronic switch, thereby charging the capacitor in the LC resonant circuit via the charging circuit; During the pulse generation time interval, the first electronic switch is turned off and the second electronic switch is turned on, so as to supply a pulse current to the electrical load through the LC resonant circuit via the first node and the second node; During the oscillation time interval interleaved with the charging time interval and the pulse generation time interval, the first electronic switch and the second electronic switch are turned on, so as to cause the LC resonant circuit to oscillate at a resonant frequency; Compare the charging voltage of the capacitor in the LC resonant circuit with a charging threshold; And According to the result of the comparison, activate a charging switch in the current flow line arranged between the power supply node and the other inductor to couple the other inductor to the power supply node; wherein the driving circuit means of the first electronic switch and the second electronic switch activate the LC resonant circuit at an activation frequency; and The capacitor and the other inductor in the LC resonant circuit resonate at a frequency lower than the activation frequency of the LC resonant circuit.

17. The method according to claim 16, further comprising: During the oscillation time interval, activate the LC resonant circuit at the activation frequency higher than the resonant frequency.

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