PULSE GENERATOR CIRCUIT, RELATED LASER SYSTEM AND METHOD

Abstract

An embodiment pulse generator circuit is configured to apply a current pulse to two output terminals. The pulse generator circuit comprises an LC resonant circuit comprising an inductance and a capacitance connected in series between a first node and a negative input terminal. The pulse generator circuit comprises a charge circuit configured to charge the capacitance via a supply voltage, a first electronic switch configured to selectively short-circuit the two output terminals, a second electronic switch configured to selectively connect the two output terminals in parallel with the LC resonant circuit, and a control circuit configured to drive the first and the second electronic switch.

Claims

1. A pulse generator circuit comprising: positive and negative input terminals for receiving a supply voltage; two output terminals for providing a current pulse to a load; an LC resonant circuit comprising an inductance and a capacitance connected in series between a first node and the negative input terminal, wherein the LC resonant circuit has a given resonant period; a charge circuit configured to charge the capacitance via the supply voltage; a first electronic switch connected between the two output terminals and configured to selectively short-circuit the two output terminals as a function of a first drive signal; a second electronic switch configured to selectively connect the two output terminals in parallel with the LC resonant circuit as a function of a second drive signal; and a control circuit configured to generate the first and the second drive signals in order to repeat the following steps during each switching cycle of a sequence of switching cycles: for a first time-interval, close the first electronic switch and open the second electronic switch, wherein the two output terminals are disconnected from the LC resonant circuit and wherein the capacitance is charged via the charge circuit; for a following second time-interval, close the first electronic switch and close the second electronic switch, wherein the two output terminals are connected in parallel with the LC resonant circuit and the two output terminals are short-circuited, and wherein the LC resonant circuit oscillates with the given resonant period; for a following third time-interval, open the first electronic switch and close the second electronic switch, wherein the two output terminals are connected in parallel with the LC resonant circuit and wherein the LC resonant circuit provides a current to the two output terminals; and for a following fourth time-interval, close the first electronic switch and close the second electronic switch, wherein the two output terminals are connected in parallel with the LC resonant circuit, wherein the two output terminals are short-circuited, and wherein the LC resonant circuit oscillates with the given resonant period.

2. The pulse generator circuit according to claim 1, wherein the current provided by the LC resonant circuit oscillates with a given maximum current value and wherein the control circuit is configured to start the third time-interval in response to the current provided by the LC resonant circuit reaching the given maximum current value.

3. The pulse generator circuit according to claim 1, wherein a duration of the second time-interval is selected in a range between 90% and 110% of one-fourth of the given resonant period.

4. The pulse generator circuit according to claim 1, wherein the current provided by the LC resonant circuit oscillates with a given maximum current value and wherein the control circuit is configured to: receive data identifying a requested current amplitude to be provided to the two output terminals; and determine a duration of the second time-interval as a function of the data identifying the requested current amplitude.

5. The pulse generator circuit according to claim 1, wherein the control circuit is configured to start the first time-interval in response to the current provided by the LC resonant circuit reaching zero.

6. The pulse generator circuit according to claim 1, wherein a duration of the fourth time-interval is selected such that a sum of a duration of the second, third and fourth time-intervals is in a range between 90% and 110% of the given resonant period.

7. The pulse generator circuit according to claim 1, wherein a duration of the third time-interval is selected in a range between 500 ps and 20 ns.

8. The pulse generator circuit according to claim 1, wherein the first and second electronic switches are connected in series between the first node and the negative input terminal, and wherein the two output terminals are connected to the first node and an intermediate node between the first and second electronic switches, respectively.

9. The pulse generator circuit according to claim 1, wherein the first and second electronic switches are connected in series between the first node and the negative input terminal, and wherein the two output terminals are connected to an intermediate node between the first and the second electronic switch and the negative input terminal, respectively.

10. The pulse generator circuit according to claim 1, wherein the inductance is connected to the first node and the capacitance is connected to the negative input terminal, and wherein the charge circuit comprises a resistance and a third electronic switch connected between a positive supply terminal and an intermediate node between the inductance and the capacitance.

11. The pulse generator circuit according to claim 1, further comprising: a plurality of the first electronic switches connected in series, wherein respective output terminals are connected to each of the plurality of first electronic switches; or a plurality of third electronic switches, each third electronic switch configured to connect respective output terminals in parallel with the first electronic switch.

12. A laser system, comprising: a pulse generator circuit comprising: positive and negative input terminals for receiving a supply voltage; two output terminals for providing a current pulse to a load; an LC resonant circuit comprising an inductance and a capacitance connected in series between a first node and the negative input terminal, wherein the LC resonant circuit has a given resonant period; a charge circuit configured to charge the capacitance via the supply voltage; a first electronic switch connected between the two output terminals and configured to selectively short-circuit the two output terminals as a function of a first drive signal; a second electronic switch configured to selectively connect the two output terminals in parallel with the LC resonant circuit as a function of a second drive signal; and a control circuit configured to generate the first and the second drive signals; and a laser diode connected to the two output terminals.

13. The laser system according to claim 12, wherein the laser system is a light detection and ranging (LiDAR) system having a transmitter section comprising: one or more pulse generator circuits configured to apply current pulses to a plurality of laser diodes; a micro-electromechanical system (MEMS) mirror with associated control circuit; a receiver portion comprising a plurality of optical sensors with an associated measurement circuit; and a control and processing circuit configured to control the one or more pulse generator circuits and the control circuit associated with the MEMS mirror, and to receive and process data received from the measurement circuit.

14. A method of operating a pulse generator circuit comprising positive and negative input terminals for receiving a supply voltage; two output terminals for providing a current pulse to a load; an LC resonant circuit comprising an inductance and a capacitance connected in series between a first node and the negative input terminal, wherein the LC resonant circuit has a given resonant period; a charge circuit configured to charge the capacitance via the supply voltage; a first electronic switch connected between the two output terminals and configured to selectively short-circuit the two output terminals as a function of a first drive signal; and a second electronic switch configured to selectively connect the two output terminals in parallel with the LC resonant circuit as a function of a second drive signal; the method comprising repeating the following steps during a sequence of switching cycles: for a first time-interval, closing the first electronic switch and opening the second electronic switch, to disconnect the two output terminals from the LC resonant circuit, and to charge the LC resonant circuit via the charge circuit; for a following second time-interval, closing the first electronic switch and closing the second electronic switch, to connect the two output terminals in parallel with the LC resonant circuit, to short-circuit the two output terminals, and to oscillate the LC resonant circuit with the given resonant period; for a following third time-interval, opening the first electronic switch and closing the second electronic switch, to connect the two output terminals in parallel with the LC resonant circuit, and to provide, by the LC resonant circuit, a current to the two output terminals; and for a following fourth time-interval, closing the first electronic switch and closing the second electronic switch, to connect the two output terminals in parallel with the LC resonant circuit, to short-circuit the two output terminals, and to oscillate the LC resonant circuit with the given resonant period.

15. The method according to claim 14, further comprising: oscillating the current provided by the LC resonant circuit with a given maximum current value; and starting the third time-interval in response to the current provided by the LC resonant circuit reaching the given maximum current value.

16. The method according to claim 14, further comprising selecting a duration of the second time-interval to be in a range between 90% and 110% of one-fourth of the given resonant period.

17. The method according to claim 14, further comprising: oscillating the current provided by the LC resonant circuit with a given maximum current value; receiving data identifying a requested current amplitude to be provided to the two output terminals; and determining a duration of the second time-interval as a function of the data identifying the requested current amplitude.

18. The method according to claim 14, further comprising starting the first time-interval in response to the current provided by the LC resonant circuit reaching zero.

19. The method according to claim 14, further comprising selecting a duration of the fourth time-interval such that a sum of a duration of the second, third and fourth time-intervals is in a range between 90% and 110% of the given resonant period.

20. The method according to claim 14, further comprising selecting a duration of the third time-interval to be in a range between 500 ps and 20 ns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The embodiments of the present disclosure will now be described with reference to the annexed plates of drawings, which are provided purely to way of non-limiting example and in which:

[0026] The features and advantages of the present invention will become apparent from the following detailed description of practical embodiments thereof, shown by way of non-limiting example in the accompanying drawings, in which:

[0027] FIG. 1 shows a circuit schematic of a pulse generator circuit;

[0028] FIGS. 2A, 2B, 2C, 2D and 2E show a circuit schematic of a first embodiment of a pulse generator circuit;

[0029] FIGS. 3A, 3B, 3C and 3D show embodiments of the switching states of the pulse generator circuit of FIG. 2;

[0030] FIG. 4 shows an embodiment of drive signals used in the pulse generator circuit of FIG. 2;

[0031] FIGS. 5 and 6 shows exemplary waveforms of the pulse generator circuit of FIG. 2;

[0032] FIG. 7 shows schematically an embodiment of an integrated circuit layout able to implement the pulse generator circuit of FIG. 2;

[0033] FIG. 8 shows a circuit schematic of a second embodiment of a pulse generator circuit;

[0034] FIGS. 9A, 9B and 9C shows embodiments of the switching states of the pulse generator circuit of FIG. 8;

[0035] FIG. 10 shows an embodiment of drive signals used in the pulse generator circuit of FIG. 8;

[0036] FIG. 11 shows a circuit schematic of a third embodiment of a pulse generator circuit;

[0037] FIG. 12 shows a circuit schematic of a fourth embodiment of a pulse generator circuit;

[0038] FIGS. 13 and 14 show embodiments of integrated circuits comprising a pulse generator circuit according to the present disclosure; and

[0039] FIG. 15 shows a laser system comprising one or more pulse generator circuits according to the present disclosure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0040] In the ensuing description, various specific details are illustrated aimed at enabling an in-depth understanding of the embodiments. The embodiments may be provided without one or more of the specific details, or with other methods, components, materials, etc. In other cases, known structures, materials, or operations are not shown or described in detail so that various aspects of the embodiments will not be obscured.

[0041] Reference to an embodiment or one embodiment in the framework of this description is meant to indicate that a particular configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment. Hence, phrases such as in an embodiment, in one embodiment, or the like that may be present in various points of this description do not necessarily refer to one and the same embodiment. Moreover, particular conformations, structures, or characteristics may be combined in any adequate way in one or more embodiments.

[0042] The references used herein are only provided for convenience and hence do not define the sphere of protection or the scope of the embodiments.

[0043] In FIGS. 2 to 15 described below, parts, elements or components that have already been described with reference to FIG. 1 are designated by the same references used previously in these figures. The description of these elements has already been made and will not be repeated in what follows in order not to burden the present detailed description.

[0044] FIG. 2A shows an embodiment of a pulse generator circuit 20a, such as a laser diode driver.

[0045] In the embodiment considered, the pulse generator circuit 20a comprises:

[0046] a positive and a negative supply terminal 200 and 202 configured to receive a DC supply voltage Vcc, wherein the negative terminal 202 represents a reference voltage, such as ground; and

[0047] a positive and a negative output terminal 204 and 206 configured to be connected to a load 30 for providing an output current Iout to the load 30.

[0048] For example, in various embodiments, the load 30 is a laser diode D, i.e. the laser diode D is connected (e.g., directly) between the terminals 204 and 206. Generally, the pulse generator circuit 20a and optionally the laser diode D may be integrated in an integrated circuit. Accordingly, in this case, the integrated circuit may comprise two power supply pads (of the die of the integrated circuit) or pins (of a respective package of the integrated circuit) connected to the terminals 200/202, and optionally (if the diode D is not integrated in the integrated circuit) and two further pads or pins for connection to the diode D.

[0049] In the embodiment considered, the pulse generator circuit 20a comprises:

[0050] an LC resonant circuit comprising an inductor Lr and a capacitor Cr connected (e.g., directly) in series between a node 210 and the terminal 202, wherein e.g., the inductor Lr is connected to the node 210 and the capacitor Cr is connected to the terminal 202;

[0051] a charge circuit 220 configured to charge the capacitor Cr;

[0052] a first electronic switch S1 (having a current-path) connected (e.g., directly) between the node 210 and a node 212 connected (e.g., directly) to the terminal 206, i.e. the electronic switch S1 is connected in parallel with the load 30 and is thus configured to selectively short-circuit the output terminals 204/206, i.e. the load 3o; and

[0053] a second electronic S2 (having a current-path) connected (e.g., directly) in series between the node 212 and the terminal 202, i.e. the second electronic S2 is configured to selectively connect the output terminals 204/206, i.e. the load 30, in parallel with the LC resonant circuit Lr/Cr; and

[0054] a control circuit 208a configured to generate drive signals DRV1 and DRV2 for the control terminals of the electronic switches S1 and S2.

[0055] For example, FIGS. 2B, 2C, 2D and 2E show possible embodiments of charge circuits 220a, 220b, 220c and 220d.

[0056] In general, the charge circuit 220 is configured to charge the capacitor Cr via the supply voltage Vcc. For example, the charge circuit 220 may be connected (e.g., directly):

[0057] between the terminal 200 and the node 210, thereby charging the capacitor Cr through the inductor Lr, or

[0058] preferably, between the terminal 200 and the intermediate node between the node 210, thereby directly charging the capacitor Cr.

[0059] For example, FIG. 2B shows an embodiment of a charge circuit 220a, wherein a resistance R is connected (e.g., directly) between the terminal 200 and the capacitor Cr, e.g., between the terminal 200 and the intermediate node between the inductor Lr and the capacitor Cr.

[0060] Thus, in this case, the capacitor Cr is charged when the voltage V.sub.cr at the capacitor is smaller than the supply voltage Vcc.

[0061] In various embodiments, the charge circuit 220 is configured to selectively charge the capacitor Cr when the electronic switch S2 is opened.

[0062] For example, FIG. 2C shows an embodiment of a charge circuit 220b, wherein a resistance R and an electronic switch SR are connected (e.g., directly) in series between the terminal 200 and the capacitor Cr, e.g., between the terminal 200 and the intermediate node between the inductor Lr and the capacitor Cr.

[0063] As shown in FIGS. 2D and 2E, such an electronic switch SR may be implemented with a controllable electronic switch, such as a FET, or a diode.

[0064] Accordingly, the control circuit 208a may be configured to also generate the drive signal for the electronic switch SR. For example, this drive signal may correspond to the inverted version of the dive signal DRV2 for the electronic switch S2.

[0065] In various embodiments, the resistance R may be a parasitic resistance or may be implemented with a resistor. For example, in various embodiments the resistance R is in a range between 0.1 ohm and 300 ohm. In general, when the electronic switch SR is used, the resistance may also be small (e.g., between 0.02 Ohm and 10 Ohm), because the electronic switch SR may be used to decouple the LC resonant circuit. For example, in this case, the resistance R may also correspond to the switch-on resistance of the electronic switch SR. Conversely, in the absence of an electronic switch SR, the resistance R should be greater (e.g., between 100 Ohm and 300 Ohm) in order to decouple the oscillation of the LC resonant circuit from the supply voltage.

[0066] In various embodiments, the inductor Lr and the capacitor Cr may be external with respect to the integrated circuit of the pulse generator circuit 20a. For example, the inductor Lr and the capacitor Cr may be connected in series between the pins/pads of such an integrated circuit which are connected to the terminals 204 and 202 of the pulse generator circuit 20a.

[0067] In various embodiments the inductance of the inductor Lr is in a range between 1 nH to 1 uH, preferably between 5 and 50 nH, and the capacitance of the capacitor Cr is in a range between 100 nF to 10 uF, preferably between 200 and 800 nF.

[0068] In various embodiments, the electronic switches may be Field-Effect Transistors (FET), such as Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFET) or preferably Gallium nitride (GaN) transistors. Accordingly, the control circuit 208a may be configured to generate drive signals DRV1 and DRV2 for the gate terminals of the FETs S1 and S2. For this purpose, the control circuit 208a may comprise FET driver circuits for generating the drive signals DRV1 and DRV2, such as a high-side driver for the FET S1 and a low-side driver circuit for the FET S2.

[0069] For example, in various embodiments, the electronic switches S1 and S2 are n-channel FET. Accordingly, in this case, the drain terminal of the FET S1 is connected (e.g., directly) to the terminal 204/node 210, the source terminal of the FET S1 is connected (e.g., directly) to the terminal 206/node 212, the drain terminal of the FET S2 is connected (e.g., directly) to the terminal 206/node 212 and the source terminal of the FET S2 is connected (e.g., directly) to the terminal 202.

[0070] FIG. 4 shows in this respect an embodiment of the drive signals DRV1 and DRV2 generated by the control circuit 208a, and FIGS. 3A, 3B, 3C and 3D show the respective switching states of the pulse generator circuit 20a.

[0071] Specifically, during/for a first time-interval T.sub.1 (see also FIG. 3A), the control circuit 208a closes the first electronic switch S1 (e.g., by setting the signal DRV1 to high) and opens the second electronic switch S2 (e.g., by setting the signal DRV1 to low), whereby the load 30/diode D is short-circuited. Moreover, the resonant circuit Lr/Cr is connected via the charge circuit 220, such as a resistance R, to the supply voltage Vcc, whereby the capacitor Cr is charged.

[0072] At an instant t, (end of the interval T.sub.1) the control circuit 208a closes the first electronic switch S1 (e.g., by setting the signal DRV1 to high) and closes the second electronic switch S2 (e.g., by setting the signal DRV1 to high). Thus, during/for a following second time-interval T.sub.2 (see also FIG. 3B) the load 30/diode D is short-circuited, and also the resonant circuit Lr/Cr is short circuited, which thus oscillates with a given resonant frequency Fr:

Fr=1/(2{square root over (Lr Cr)})(1)

[0073] At an instant t.sub.2 (end of the interval T.sub.2) the control circuit 208a opens the first electronic switch S1 (e.g., by setting the signal DRV1 to low) and closes the second electronic switch S2 (e.g., by setting the signal DRV1 to high). Thus, during/for a following third time-interval T.sub.3 (see also FIG. 3C), the load 30/diode D is connected in in parallel with the resonant circuit Lr/Cr, and is thus powered via the current i.sub.CR flowing through the resonant circuit Lr/Cr. Thus, the time-interval T.sub.3 represents the switch-on interval T.sub.ON of the load 30.

[0074] At an instant t.sub.3 (end of the interval T.sub.3) the control circuit 208a closes the first electronic switch S1 (e.g., by setting the signal DRV1 to high) and closes the second electronic switch S2 (e.g., by setting the signal DRV1 to high). Thus, during/for a following fourth time-interval T.sub.4 (see also FIG. 3D), the load 30/diode D and also the resonant circuit Lr/Cr are short circuited, whereby the resonant circuit oscillates with the resonant frequency Fr.

[0075] At an instant t.sub.4 (end of the interval T.sub.4) the control circuit 208a closes the first electronic switch S1 (e.g., by setting the signal DRV1 to high) and opens the second electronic switch S2 (e.g., by setting the signal DRV1 to low), whereby the load 30/diode D is short-circuited. Moreover, the resonant circuit Lr/Cr is connected via the charge circuit 220, such as a resistance R, to the supply voltage Vcc, whereby the capacitor Cr is charged.

[0076] Thus, by closing the electronic switch S2 after a time-interval T.sub.1/at a next instant t.sub.1 the control circuit 208a may start a new cycle comprising the phases T.sub.2, T.sub.3 and T.sub.4.

[0077] FIG. 5 shows in this respect embodiments of the waveforms of:

[0078] the drive signals DRV1 and DRV2,

[0079] the voltage V.sub.Cr at the capacitor Cr and the current i.sub.Cr flowing through the capacitor Cr, i.e. the current flowing through the LC resonant circuit;

[0080] the current i.sub.S1 flowing through the (current path) of the electronic switch S1;

[0081] the voltage V.sub.S1 at the electronic switch S1;

[0082] the output current iout, i.e. the current flowing through the load 30/laser diode D.

[0083] As mentioned before, in various embodiments, the electronic switches S1 and S2 may be FET. Accordingly, in this case, the current is, corresponds to the drain-source current of the FET S1, and the voltage Vs, corresponds to the drain-source voltage of the FET S1. Moreover, FIG. 5 shows for this case also a possible waveform of the gate-source voltage V.sub.GS1 generated at the gate terminal of the FET S1 in response to the drive signal DRV1.

[0084] FIG. 6 shows in the context of a plurality of switching cycles embodiments of waveforms of:

[0085] the drive signals DRV1 and DRV2,

[0086] the current i.sub.S1 flowing through the (current path) of the electronic switch S1;

[0087] the voltage V.sub.S2 at the electronic switch S1;

[0088] the output current iout, i.e. the current flowing through the load 30/laser diode D.

[0089] the output voltage Vout, i.e. the voltage at the load 30/laser diode D.

[0090] Thus, in the embodiments described with respect to the operation shown in FIGS. 5 and 6, the drive signals DRV1 and DRV2 are pulsed signals having given switching durations T.sub.SW1=T.sub.ON1+T.sub.OFF1 and T.sub.SW2=T.sub.ON2+T.sub.OFF2, with T.sub.SW1=T.sub.SW2. Specifically, in various embodiments:

[0091] the switch-on time T.sub.ON1 of the switch S1 (e.g., when the drive signal DRV1 is set to high) corresponds to T.sub.1+T.sub.2+T.sub.4, and the switch-off time T.sub.OFF1 of the switch S1 (e.g., when the drive signal DRV1 is set to low) corresponds to T.sub.3=T.sub.ON; and

[0092] the switch-on time T.sub.ON2 of the switch S2 (e.g., when the drive signal DRV2 is set to high) corresponds to T.sub.2+T.sub.3+T.sub.4, and the switch-off time T.sub.OFF2 of the switch S2 (e.g., when the drive signal DRV2 is set to low) corresponds to T.sub.1.

[0093] In various embodiments, the switch-on time T.sub.ON2 of the electronic switch S2 corresponds (approximately) to a multiple of a period Tr=1/Fr of the oscillation, i.e.:

T.sub.ON2=i.Math.1/Fr(2)

[0094] where i is a positive integer number. Specifically, in various embodiments, i corresponds to one, i.e. T.sub.ON2=1/Fr.

[0095] The inventors have observed that the electronic switch S2 may be opened in this way at zero current, i.e. at the instants when the current is, is zero. Moreover, the voltage V.sub.Cr reaches in this case its maximum value, thereby improving the recharging of the capacitor Cr. Generally, also an approximate value of the switch-on time T.sub.ON2 may be used. For example, in various embodiments, the actual switch-on time T.sub.ON2 used by the control circuit 208a may be in a range between 90% and 110% of the ideal value T.sub.ON2 shown in equation (2), preferably between 95% and 105%.

[0096] Thus, in various embodiments, the charge circuit 220, such as a resistance R (optionally connected via a switch SR to the capacitor Cr), charges the capacitor Cr during the time interval T.sub.1 substantially to the value of the supply voltage Vcc.

[0097] Next, the control unit 208a closes the switch S2 for a duration T.sub.ON2 close to 1/Fr (or a multiple thereof), where Fr=1/(2 Lr Cr) is the resonant frequency of the LC resonant circuit. Accordingly, the values Vcc, Lr and Cr define the resonant peak current i.sub.max flowing through the LC resonant tank:

i.sub.max={square root over (Cr/Lr)}.Math.Vcc(3)

[0098] The control unit 208a opens then the switch S1 for the time-interval T.sub.OFF1=T.sub.3=T.sub.ON. For example, in various embodiments, the time T.sub.ON corresponds to the desired laser diode pulse current duration. Specifically, when the electronic switch S1 is opened, the current provided by the LC resonant circuit is forced to flow immediately through the output terminals 204/206, i.e. the load 30/laser diode D.

[0099] Thus, by controlling the duration of the interval T.sub.2, the control unit 208a may select the value of the current i.sub.out to be provided to the load 30/laser diode D. For example, in various embodiments, the duration of the time interval T.sub.2 corresponds to the instants when the resonant current i.sub.Cr reaches its peak value i.sub.m, e.g.:

T.sub.2=Tr=1/(4Fr)(4)

[0100] Generally, also an approximate value of the above time T.sub.2 may be used. For example, in various embodiments, the actual switch-on time T.sub.2 used by the control circuit 208a may be in a range between 90% and 110% of the value T.sub.2 shown in equation (4), preferably between 95% and 105%.

[0101] In various embodiments, the time T.sub.2 is constant (even though this time may be settable/programmable) in order to generate pulses with the same current value.

[0102] When the control circuit 208a then closes the switch S1 at the instant t.sub.3 (end of interval T.sub.3), the load 30/laser diode D is short-circuited and the current iout goes to zero. In parallel, the LC resonant circuit continues to oscillate until the control circuit 208a opens the electronic switch S2. As mentioned before, the control unit 208a may open the electronic switch S2 at the instants when the current i.sub.CR crosses zero.

[0103] Once the electronic switch S2 is opened, the capacitor Cr is recharged via the charge circuit 220. As mentioned before, due to the additional time interval T.sub.4 (which permits to obtain a duration T.sub.ON2 close to 1/Fr) the capacitor Cr may already be recharged in part with the residual energy stored in the resonant loop.

[0104] Accordingly, in the embodiment considered, the inductor Lr essentially implements a current source. This is particularly useful for diodes, such a laser diodes D, insofar as diodes require rather a requested current than a requested voltage. Moreover, this permits that the supply voltage Vcc is smaller than the voltage-drop of the laser diode D because the current i.sub.Cr will flow through the diode regardless the value of the voltage-drop.

[0105] FIG. 7 shows a possible embodiment of a printed circuit layout adapted to be used to mount the electronic switches S1/S2, the diode D, and the control circuit 208a.

[0106] In the embodiment considered, the electronic switches are FETs. Specifically, the electronic switch S1 comprises a gate terminal GT.sub.1, at least one source terminal ST.sub.1 and at least one drain terminal DT.sub.1. Similarly, the electronic switch S2 comprises a gate terminal GT.sub.2, at least one source terminal ST.sub.2 and at least one drain terminal DT.sub.2.

[0107] Accordingly, the printed circuit board may comprise:

[0108] a first metallic area/track MA.sub.1 for connecting the gate terminal GT.sub.1 to the terminal of the control circuit 208a providing the drive signal DRV1;

[0109] a second metallic area/track MA.sub.2 for connecting the drain terminal DT.sub.1 to the terminal 204/anode of the diode D;

[0110] a third metallic area/track MA.sub.1 for connecting the source terminal ST.sub.1 to the terminal 206/cathode of the diode D and the drain terminal DT.sub.2;

[0111] a fourth metallic area/track MA.sub.4 for connecting the gate terminal GT.sub.2 to the terminal of the control circuit 208a providing the drive signal DRV2; and

[0112] a fifth metallic area/track MA.sub.5 for connecting the source terminal ST.sub.2 to the terminal 202, such as a ground pin of the control circuit 208a.

[0113] In general, the components S1, S2, D and/or 208a may have a respective package with pins or may be mounted directly on the PCB, or by using chip-on-chip technology. For example, just to provide a dimensional reference, such electronic switches (without package) may have a width W in the range of 1 mm.

[0114] Generally, also other circuit arrangements may be used, which comprise:

[0115] an LC resonant circuit comprising an inductor Lr and a capacitor Cr connected in series;

[0116] a charge circuit 229 configured to charge the capacitor Cr via the supply voltage Vcc, such as the resistor R and/or an electronic switch SR connected between the supply voltage Vcc and the capacitor Cr;

[0117] a first electronic switch S1 configured to selectively short-circuit the output terminals, i.e. the load 30/laser diode D;

[0118] a second electronic switch S2 configured to selectively connect the output terminals, i.e. the load 30/laser diode D, to the LC resonant circuit; and

[0119] a control circuit 208a configured to control the switching of the first and second electronic switch S1 and S2 with the following sequence of time intervals:

[0120] during a first time-interval T.sub.1, close the first electronic switch S1 and open the second electronic switch S2;

[0121] during a second time-interval T.sub.2, close the first electronic switch S1 and close the second electronic switch S2;

[0122] during a third time-interval T.sub.1, open the first electronic switch S1 and close the second electronic switch S2; and

[0123] during a fourth time-interval T.sub.4, close the first electronic switch S1 and close the second electronic switch S2.

[0124] For example, FIG. 8 shows an embodiment wherein a different connection is used.

[0125] Specifically, in the embodiment considered, the pulse generator circuit 20a comprises again:

[0126] a positive and a negative supply terminal 200 and 202 configured to receive the DC supply voltage Vcc, wherein the negative terminal 202 represents again a reference voltage, such as ground;

[0127] a positive and a negative output terminal 204 and 206 configured to be connected to the load 30 for providing an output current Iout to the load 30/laser diode D;

[0128] an LC resonant circuit comprising an inductor Lr and a capacitor Cr connected (e.g., directly) in series between a node 210 and the terminal 202;

[0129] a charge circuit 220, e.g., implemented with a resistance R connected (e.g., directly) between the terminal 200 and the intermediate node between the inductor Lr and the capacitor Cr;

[0130] two electronic switches S1 and S2, such as (n-channel) FET, connected (e.g., directly) between the node 210 and the terminal 202.

[0131] In FIG. 2, the output terminals 204 and 206 were connected (e.g., directly) to the node 210 and the intermediate node 212 between the electronic switches S1 and S2. Accordingly, the (high-side) electronic switch S1 was configured to short-circuit the output terminals 204 and 206, i.e. the load 30, and the (low-side) electronic switch S2 was configured to connect the output terminals 204 and 206, i.e. the load 30, in parallel with the LC resonant circuit.

[0132] Conversely, in the embodiment considered, the output terminals 204 and 206 are connected (e.g., directly) to the intermediate node 212 between the electronic switches S1/S2 and the terminal 202, respectively. Accordingly, the low-side switch (connected between the node 212 and the terminal 202) is now configured to short-circuit the output terminals 204 and 206, i.e. the load 30, and corresponds thus now to the electronic switch S1. Conversely, the high-side electronic switch is now configured to connect the output terminals 204 and 206, i.e. the load 30, in parallel with the LC resonant circuit (i.e. between the node 210 and the terminal 202) and corresponds thus now to the electronic switch S2.

[0133] FIG. 10 shows in this respect an embodiment of the drive signals DRV1 and DRV2 generated by the control circuit 208a, and FIGS. 9A, 9B, 9C show the respective switching states of the pulse generator circuit.

[0134] Specifically, as shown in FIG. 10, the drive signals DRV1 and DRV2 generated by the control circuit 208a correspond to the drive signals shown in FIG. 4 (except for the voltage levels in order to e.g., generate the required gate-source voltages). Accordingly, the respective description concerning the time-intervals T.sub.1, T.sub.2, T.sub.3 and T.sub.4 apply also to the embodiment shown in FIG. 8.

[0135] For example, FIG. 9A shows the switching state for the time-interval T.sub.1 (electronic switch S1 closed and electronic switch S2 opened). FIG. 9B shows the switching state for the time-intervals T.sub.2 and T.sub.4 (electronic switches S1 and S2 closed). Finally, FIG. 9C shows the switching state for the time-interval T.sub.3 (electronic switch S1 opened and electronic switch S2 closed).

[0136] In various embodiments, the pulse generator circuit 20a may also be configured to sequentially apply pulses to a plurality of loads, such as a number N of laser diodes D.sub.1, D.sub.2 . . . D.sub.N.

[0137] For example, FIG. 11 shows an embodiment, wherein the laser diodes D.sub.1, D.sub.2 . . . D.sub.N are connected in series between the node 212 and the terminal 202.

[0138] In the embodiment considered, the pulse generator circuit 20a comprises:

[0139] a positive and a negative supply terminal 200 and 202 configured to receive the DC supply voltage Vcc, wherein the negative terminal 202 represents again a reference voltage, such as ground;

[0140] an LC resonant circuit comprising an inductor Lr and a capacitor Cr connected (e.g., directly) in series between the node 210 and the terminal 202;

[0141] a charge circuit 220, e.g., implemented with a resistance R connected (e.g., directly) between the terminal 200 and the intermediate node between the inductor Lr and the capacitor Cr;

[0142] an electronic switch S2 configured to connected the node 212 to the LC resonant circuit, i.e. the electronic switch S2 is configured to connected the series connection of laser diodes D.sub.1, D.sub.2 . . . D.sub.N in parallel with the LC resonant circuit, i.e. between the node 210 and the terminal 202;

[0143] N electronic switches S1.sub.1 . . . S1.sub.N, wherein each of the N electronic switches S1.sub.1 . . . S1.sub.N is configured to short-circuit a respective laser diode D.sub.1 . . . D.sub.N;

[0144] a control circuit 208a configured to generate the drive signal DRV2 for the electronic switch S2 and drive signals DRV1 . . . DRV1.sub.N for the electronic switches S1.sub.1 . . . S1.sub.N.

[0145] Specifically, in the embodiment considered, the drive signal DRV2 corresponds to the drive signal DRV2 described in the foregoing. Moreover, the control circuit 208a may be configured to apply the drive signal DRV1 described in the foregoing during each switching cycle to a respective single switch or plurality of switches S1.sub.1 . . . S1.sub.N, i.e. in general to a respective subset of the switches S1.sub.1 . . . S1.sub.N. Accordingly, a current pulse can be applied to one or more laser diodes D.sub.1 . . . D.sub.N when one or more switches S1.sub.1 . . . S1.sub.N are opened during the time interval T.sub.3 of a given switching cycle. With this solution it is thus possible to apply a current pulse to a plurality of laser diodes either at the same time or during different switching cycles. For example, in the way the pulse generator circuit 20a may apply a current pulse sequentially to all laser diodes, by opening sequentially during N switching cycles always a different electronic switch S1.sub.1 . . . S1.sub.N.

[0146] Conversely, FIG. 12 shows an embodiment, wherein the laser diodes D.sub.1 . . . D.sub.N are connected in parallel between the node 212 and the terminal 202. Moreover, each electronic switch has connected in series a respective electronic switch S3.sub.1 . . . S3.sub.N, i.e. each of the diodes D.sub.1 . . . D.sub.N is connected with a respective electronic switch S3.sub.1 . . . S3.sub.N between the node 212 and the terminal 202.

[0147] In the embodiment considered, the pulse generator circuit 20a comprises again:

[0148] positive and a negative supply terminal 200 and 202 configured to receive the DC supply voltage Vcc, wherein the negative terminal 202 represents again a reference voltage, such as ground;

[0149] an LC resonant circuit comprising an inductor Lr and a capacitor Cr connected (e.g., directly) in series between a node 210 and the terminal 202;

[0150] a charge circuit 220, e.g., implemented with a resistance R connected (e.g., directly) between the terminal 200 and the intermediate node between the inductor Lr and the capacitor Cr;

[0151] an electronic switch S2 configured to connected the node 212 to the LC resonant circuit, i.e. the electronic switch S2 is configured to connect the parallel connection of laser diodes D.sub.1, D.sub.2 . . . D.sub.N in parallel with the LC resonant circuit, i.e. between the node 210 and the terminal 202;

[0152] an electronic switch S1 configured to short-circuit the parallel connection of laser diode D.sub.1 . . . D.sub.N; and

[0153] a control circuit 208a configured to generate the drive signals DRV1 and DRV2 for the electronic switches S1 and S2 and drive signals DRV3.sub.1 . . . DRV3.sub.N for the electronic switches S3.sub.1 . . . S3.sub.N.

[0154] Specifically, in the embodiment considered, the drive signals DRV1 and DRV2 correspond to the drive signals described in the foregoing, thereby generating during each time interval T.sub.3 of the switching cycles a current pulse. Moreover, the control circuit 208a may be configured to generate the drive signals DRV3.sub.1 . . . DRV3.sub.N in order to close during each switching cycle a respective single switch S3.sub.1 . . . S3.sub.N or plurality of switches S3.sub.1 . . . S3.sub.N. Accordingly, a current pulse can be applied to one or more laser diodes D.sub.1 . . . D.sub.N when one or more switches S3.sub.1 . . . S3.sub.N are closed during the time interval T.sub.3 of a given switching cycle. With this solution it is thus again possible to apply a current pulse to a plurality of laser diodes either at the same time or with different timing. For example, in the way the pulse generator circuit 20a may again apply a current pulse sequentially to all laser diodes, by closing sequentially during N switching cycles always a different electronic switch S3.sub.1 . . . S3.sub.N.

[0155] In general, the solutions shown in FIGS. 11 and 12 may similarly be used when the diodes D.sub.1 . . . D.sub.N are connected between the node 210 and the node 212. In this case, only the position of the electronic switches S1 and S2 have to be inverted. For example, for the case shown in FIG. 11, the electronic switch S2 could be connected between the node 212 and the terminal 202, and the electronic switches S1.sub.1 . . . S1.sub.N could be connected between the node 210 and the node 212, wherein a respective laser diode D.sub.1 . . . D.sub.N is connected in parallel with each electronic switch S1.sub.1 . . . S1.sub.N.

[0156] In general, each of the laser diodes D mentioned in the foregoing could also be implemented with a plurality of laser diodes connected in parallel or preferably in series.

[0157] As described in the foregoing, the pulse generator circuit 20a and optionally the load 30/laser diodes D may be integrated in an integrated circuit.

[0158] For example, FIG. 13 shows an embodiment, wherein the integrated circuit comprises pads/pins 204 and 206 for connection to an external diode D.

[0159] Moreover, FIG. 13 highlights that such an integrated circuit may comprise a communication interface 216, such as an Inter-Integrated Circuit (I2C) or Serial Peripheral Interface (SPI), connected to one or more pads/pins 214 of the integrated circuit. For example, the control circuit 208a may be configured to use this communication interface 216 in order to receive control commands CTRL and/or send diagnostic data DIAG. For example, the control commands CTRL may include instruction indicating whether a current pulse should be applied to the diode D and/or data identifying the amplitude of the current pulse, e.g., data identifying the duration of the time interval T.sub.2. Conversely, the diagnostic data DIAG may comprise data indicating the amplitude of the current pulse applied to the diode D. For example, for this purpose the pulse generator circuit 20a may comprise a current sensor connected in series with the diode D, the switch S2 or with the RC resonant circuit.

[0160] Similarly, FIG. 14 shows that the integrated circuit may also be connected to a plurality of external diodes D.sub.1 . . . D.sub.N, such as an array or matrix of laser diodes as they are often used in LiDAR systems. For example, in FIG. 14, the integrated circuit comprises a pad/pin 204 and a plurality of pads/pins 206.sub.1 . . . 206.sub.N for connection to external diodes D.sub.1 . . . D.sub.N.

[0161] FIG. 15 shows an embodiment of an electronic system comprising a pulse generator circuit 20a as described in the foregoing. Specifically, in the embodiment considered, the electronic system is a LiDAR system comprising:

[0162] a transmitter portion 42 comprising:

[0163] one or more pulse generator circuits 20a configured to apply current pulses to a plurality of laser diodes, e.g., according to a given timing scheme;

[0164] a Micro-Electro-Mechanical Systems (MEMS) mirror 420 having associated a respective control circuit 422 in order to send actuation commands to the MEMS mirror 420 and optionally to receive position data from the MEMS mirror 420;

[0165] a receiver portion 44 comprising a plurality of optical sensors 440, such as photo diodes D.sub.R, configured to provide a signal to a respective measurement circuit 442; and

[0166] a control and processing circuit 40 configured to provide control information to the pulse generator circuits 20a and the control circuit 422 associated with the MEMS mirror 420, and to receive and process the data received from the measurement circuit 440.

[0167] In various embodiment, the control and processing circuit 40 may be configured to exchange data COM with another electronic circuit, such as in order to send the processed data, e.g., data being indicative of the distance of one or more objects from the LiDAR system.

[0168] Accordingly, one or more of the described embodiments have the following advantages:

[0169] a fast switching with rise and fall times in the 100 ps range may be obtained, which permits the generation of current pulses with a duration in the ins range (e.g., the duration of the time-interval T.sub.3 may be selected in a range between 50 ps and 20 ns, preferably between 1 ns and 2 ns) with a current amplitude i.sub.max selected in a range between 5 A and 20 A, preferably between 10 A and 50 A.

[0170] an easy control of the amplitude of the current pulse is possible by adapting the duration of the time interval T.sub.2;

[0171] the switching loop may be implemented directly in an integrated circuit, which permits to reduce parasitic inductances inside the commutation loop, e.g., below 0.1 nH; and

[0172] the value of the supply voltage Vcc may be smaller than laser diode voltage drop.

[0173] Of course, without prejudice to the principle of the invention, the details of construction and the embodiments may vary widely with respect to what has been described and illustrated herein purely by way of example, without thereby departing from the scope of the present invention, as defined by the ensuing claims.