# US 2021/0242659 A1 · Resonant laser driver

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- Number: US 2021/0242659 A1
- Document ID: US20210242659A1
- Status: Published application
- Kind: A1
- Application number: 16/781,652
- Filed: 2020-02-04
- Published: 2021-08-05
- Earliest claimed: 2020-02-04
- Assignees: Analog Devices International Unlimited Company
- Applicants: Analog Devices International Unlimited Company
- Inventors: Jiannan Huang; Frank M. Yaul; Jonathan Ephraim David Hurwitz; Nicolas Le Dortz; Junhua Shen
- Web page: https://patentgrep.com/patent/US20210242659A1

## CPC

- H01S 5/0427: {for applying modulation to the laser}
- H05B 45/30: Driver circuits
- G01S 7/4911: Transmitters
- H05B 45/39: Circuits containing inverter bridges
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

A laser emitter circuit comprises a laser diode; a driver circuit configured to generate a drive signal; and a resonant circuit coupled to the driver circuit and the laser diode, wherein the resonant circuit is configured to use the drive signal of the driver circuit to generate a continuous wave sinusoidal drive signal to drive the laser diode.

## Claims

### Claim 1

A laser emitter circuit comprising:
a laser diode;
a driver circuit configured to generate a drive signal; and
a resonant circuit coupled to the driver circuit and the laser diode, wherein the resonant circuit is configured to use the drive signal of the driver circuit to generate a continuous wave sinusoidal drive signal to drive the laser diode.

### Claim 2 (depends on 1)

The laser emitter circuit of claim 1, including:
a bias circuit coupled to the laser diode; and
wherein the driver circuit is configured to generate a drive signal with significant energy at substantially a resonant frequency of the resonant circuit, and the resonant circuit is configured to produce the continuous wave sinusoidal drive signal from the drive signal and includes:
a capacitive circuit element coupled in series to the drive circuit; and
an inductive circuit element arranged in series to the capacitive circuit element and the laser diode.

### Claim 3 (depends on 2)

The laser emitter circuit of claim 2, wherein the driver circuit is configured to generate a square wave drive signal and the resonant circuit is configured to produce the continuous wave sinusoidal drive signal from the square wave drive signal.

### Claim 4 (depends on 1)

The laser emitter circuit of claim 1, including an amplitude tuning circuit configured to adjust a circuit supply of the driver circuit to adjust an amplitude of continuous wave sinusoidal drive signal.

### Claim 5 (depends on 4)

The laser emitter circuit of claim 4,
wherein the driver circuit includes a pre-driver circuit that includes a buffer circuit to provide a square wave drive signal as the drive signal; and
wherein the amplitude tuning circuit includes a voltage regulator circuit with a tunable output voltage provided as a circuit supply to the buffer circuit.

### Claim 6 (depends on 5)

The laser emitter circuit of claim 5, wherein the amplitude tuning circuit includes a pull up assist transistor coupled to an output of the voltage regulator circuit, wherein the pull up assist transistor is only activated during a transition of an input signal to the buffer circuit.

### Claim 7 (depends on 1)

The laser emitter circuit of claim 1, including:
a bias circuit coupled to one of a cathode or an anode of the laser diode, wherein the bias circuit includes:
a bias inductance coupled to the laser diode; and
a current mirror coupled to bias inductance.

### Claim 8 (depends on 1)

The laser emitter circuit of claim 1, wherein the resonant circuit is tunable to adjust a resonant frequency of the resonant circuit to a frequency of the drive signal.

### Claim 9 (depends on 8)

The laser emitter circuit of claim 8, wherein the resonant circuit includes a tunable capacitance circuit.

### Claim 10 (depends on 9)

The laser emitter circuit of claim 9, wherein the tunable capacitance circuit includes multiple capacitive circuit elements and at least one switch circuit, and wherein a capacitive circuit element coupled to the at least one switch circuit is greater than the parasitic capacitances of the switch circuit when the switch circuit is in an off state.

### Claim 11

A laser diode drive circuit comprising:
a driver circuit configured to generate drive signal;
a resonant circuit having an input coupled to an output of the driver circuit and having an output for coupling to a laser diode, wherein the resonant circuit is configured to produce a continuous wave sinusoidal drive signal from the drive signal to drive the laser diode; and
a bias circuit including a bias inductance for coupling to the laser diode.

### Claim 12 (depends on 11)

The laser diode drive circuit of claim 11, wherein the bias circuit includes a current mirror circuit including a first current mirror branch and a second current mirror branch, wherein the first current mirror branch is coupled to the bias inductance.

### Claim 13 (depends on 11)

The laser diode drive circuit of claim 11, including the laser diode, and wherein the resonant circuit includes:
a capacitive circuit element coupled in series to the driver circuit; and
an inductive circuit element arranged in series to the capacitive circuit element and the laser diode.

### Claim 14 (depends on 13)

The laser diode drive circuit of claim 13, wherein the resonant circuit is tunable to adjust a resonant frequency of the resonant circuit to a frequency of the drive signal.

### Claim 15 (depends on 11)

The laser diode drive circuit of claim 11, wherein the resonant circuit includes an inductive circuit element, and wherein at least one of the bias inductance or the inductive circuit element of the resonant circuit are implemented using one or more bond wires of an integrated circuit that includes the laser diode.

### Claim 16 (depends on 11)

The laser diode drive circuit of claim 11, including an amplitude tuning circuit configured to adjust a circuit supply of the driver circuit to adjust an amplitude of continuous wave sinusoidal drive signal.

### Claim 17 (depends on 16)

The laser diode drive circuit of claim 16, wherein the amplitude tuning circuit includes a voltage regulator circuit having a tunable output voltage provided as a circuit supply to the driver circuit.

### Claim 18 (depends on 11)

The laser diode drive circuit of claim 11, including a second drive circuit configured to generate second drive signal and a second resonant circuit coupled to the second drive circuit and having an output for coupling to the laser diode, wherein the second resonant circuit is configured to produce a second continuous wave sinusoidal drive signal from the second drive signal to drive the laser diode.

### Claim 19

A method of operating a laser emitter of a time of flight sensor, the method comprising:
generating a drive signal using a driver circuit;
producing, using a resonant circuit, a continuous wave sinusoidal drive signal from the square wave drive signal; and
driving the laser diode using the continuous wave sinusoidal drive signal.

### Claim 20 (depends on 19)

The method of claim 19, including biasing the operating current of the laser diode using a bias inductance coupled to the laser diode and a current mirror coupled to the bias inductor.

### Claim 21 (depends on 19)

The method of claim 19, wherein the driver circuit includes a pre-driver circuit and a main driver circuit, and the method further includes adjusting a circuit supply of one of the pre-driver circuit or the main driver circuit to adjust the amplitude of the continuous wave sinusoidal drive signal.

### Claim 22 (depends on 19)

The method of claim 19, including tuning the resonant frequency of the resonant circuit to the frequency of the drive signal.