Laser driver
A laser driver is described which comprises a resonant circuit having an inductor and a DC blocking capacitor. A biasing voltage reference is operably coupled to the inductor. A controller is operable for controlling the resonant circuit for selectively connecting the inductor between high and low impedance. The DC blocking capacitor is operable for connecting to a laser diode.
1. A laser driver comprising:
a resonant circuit having an inductor and a DC blocking capacitor;
a biasing voltage reference operably coupled to the inductor;
and a controller operable for controlling the resonant circuit for selectively connecting the inductor to ground; wherein the DC blocking capacitor is operable for connecting to a laser diode,
wherein the controller comprises a switch such that when the switch is closed, a path is provided from the inductor to ground, and when the switch is open, the path to ground is isolated from the inductor; and
wherein the switch comprises a Gallium Nitride transistor.
2. A laser driver as claimed in claim 1 ; wherein when the inductor is connected to the high impedance at least one of terminals of the inductor is connected to an open circuit.
3. A laser driver as claimed in claim 1 ; wherein when the inductor is connected to the low impedance at least one of terminals is shorted to ground.
4. A laser driver as claimed in claim 1 ; wherein the controller is configured to repetitively switch the inductor between high and low impedance.
5. A laser driver as claimed in claim 4 ; wherein the inductor has a value in the range of 1 nH to 50 nH.
6. A laser driver as claimed in claim 5 ; wherein the DC blocking capacitor has a value in the range of 10 pF to 1 nF.
7. A laser driver as claimed in claim 4 ; wherein an induced laser driver current is generated by the resonant circuit.
8. A laser driver as claimed in claim 7 ; wherein the induced laser driver current is a pulse signal.
9. A laser driver as claimed in claimed claim 8 ; wherein the width of each pulse of the pulse signal is less than or equal to 1 ns.
10. A laser driver as claimed in claim 8 ; wherein the width of each pulse of the pulse signal is in the range of 100 ps to 2 ns.
11. A laser driver as claimed in claim 1 ; wherein the DC blocking capacitor is operable for connecting to an anode of the laser diode.
12. A laser driver as claimed in claim 11 ; wherein a cathode of the laser diode is operably coupled to ground.
13. A laser driver as claimed in claim 1 ; wherein the DC blocking capacitor is operable for connecting to a cathode of the laser diode.
14. A laser driver as claimed in claim 11 ; wherein the anode of the laser diode is operably coupled to ground.
15. A laser driver as claimed in claim 11 ; wherein the biasing voltage reference is operable to provide a positive bias voltage.
16. A laser driver as claimed in claim 15 ; wherein the positive bias voltage is in the range of 10 V to 50 V.
17. A laser driver as claimed in claim 14 ; wherein the biasing voltage reference is operable to provide a negative bias voltage.
18. A laser driver as claimed in claim 1 ; further comprising a control voltage reference which is operable for selectively opening and closing the switch.
19. A laser driver as claimed in claim 18 ; wherein the control voltage reference is operable to provide a pulsed voltage reference.
20. A laser driver as claimed in claim 1 ; wherein the biasing voltage reference biases the inductor with a voltage level in the range of 10 V to 50 V.
21. A laser driver as claimed in claim 1 ; wherein an induced EMF voltage is generated across the inductor.
22. A laser driver as claimed in claim 21 ; wherein the induced EMF voltage opposes the biasing voltage reference until a steady state DC voltage value is reached.
23. A laser driver as claimed in claim 1 ; wherein the controller repetitively cycles the switch between open and closed states.
24. A laser driver as claimed in claim 23 ; wherein the time period of the open state in the cycle is ≥10 nanoseconds.
25. A laser driver as claimed in claim 24 ; wherein the time period of the closed state in the cycle is 10 to 100 nanoseconds.
26. A laser driver as claimed in claim 25 ; wherein the time period of the open and closed states is substantially equal.
27. A laser driver as claimed in claim 1 ; wherein the controller is configured to apply a pulsed drive signal to the switch for controlling thereof.
28. A laser driver as claimed in claim 1 ; wherein when the switch is closed a DC current that was flowing through the inductor is unable to stop abruptly thereby generating a back EMF across the inductor and an induced current generated by the back EMF is diverted through DC current blocking capacitor C 1 and the laser diode.
29. A laser driver as claimed in claim 1 ; wherein the resonant circuit resonates at a frequency 1/(2π(LC)½) which determines a pulse width of the induced current pulse injected into the laser driver.
30. A laser driver as claimed in claim 29 ; wherein the pulse width of the induced current is tuned by appropriate selection of the inductor and DC blocking capacitor values.
31. A laser driver as claimed in claim 1 ; further comprising a protection diode operable for protecting the laser diode against reverse polarity when the resonant circuit is resonating.
32. A laser driver as claimed in claim 1 ; wherein the controller comprises a MOSFET driver.
33. A laser driver as claimed in claim 32 ; wherein the MOSFET driver is operable to drive the Gallium Nitride transistor with a pulse signal having positive and negative components.
34. A laser driver as claimed in claim 33 ; wherein the maximum value of the pulse signal corresponds to the maximum gate source voltage range of the Gallium Nitride transistor.
35. A laser driver as claimed in claim 33 ; wherein the pulse signal is in the range of −6V to +6V.
36. A laser driver as claimed in claim 33 ; wherein the pulse signal has a duty cycle of 0.1% or less.
37. A laser driver as claimed in claim 36 ; wherein the pulse signal has a pulse width of 100 ns or less.
38. A laser driver as claimed in claim 1 ; wherein the maximum reverse gate source voltage of the transistor corresponds to a Gate Source junction value when the transistor is driven into depletion causing the drain source current to turn off abruptly.
39. A LiDAR device comprising:
a laser driver as claimed in claim 1 ;
a laser operably coupled to the laser driver; and
an optical detector.
40. A LiDAR device as claimed in claim 39 ; wherein the optical detector comprises a Geiger mode detector.
41. A LiDAR device as claimed in claim 39 ; wherein the optical detector comprises a SiPM detector.
42. A LiDAR device as claimed in claim 39 ; wherein the optical detector comprises a single photon avalanche diode (SPAD).