Laser diode current driving apparatus

Patent metadata

Field	Value
Publication number	US-11196229-B2
Application number	US-201916440619-A
Country	US
Kind code	B2
Filing date	Jun 13, 2019
Priority date	Jun 21, 2018
Publication date	Dec 7, 2021
Grant date	Dec 7, 2021

Abstract

A driver circuit for a laser diode is configured to pass a current. The circuit includes a charge-pump configured to generate an output boosted positive supply rail voltage. At least one switch is configured to couple the output of the charge-pump to a terminal of the laser diode and to isolate the positive supply rail from the terminal of the laser diode when the charge-pump is enabled.

First claim

What is claimed is:

1. A driver circuit for a laser diode configured to pass a current, the driver circuit comprising:
a drive transistor configured to supply the laser diode with a controllable current;
a regulator configured to control the drive transistor, wherein the regulator comprises an input for indicating a controllable current target value and a forward biased modeled voltage generator configured to model the laser diode;
a charge-pump configured to generate an output boosted positive supply rail voltage;
a first switch circuit configured to couple the output of the charge-pump to the regulator in response to the charge-pump being enabled and couple the positive supply rail to the regulator in response to the charge-pump being disabled; and
a second switch circuit configured to couple the output of the charge-pump to a terminal of the laser diode and to isolate the positive supply rail from the terminal of the laser diode in response to the charge-pump being enabled.

2. The driver circuit as claimed in claim 1 , wherein the second switch circuit is further configured to isolate the output of the charge-pump from the terminal of the laser diode and to couple the positive supply rail to the terminal of the laser diode in response to the charge-pump being disabled.

3. The driver circuit as claimed in claim 1 , further comprising a charge-pump regulator voltage generator configured to supply an input voltage to the charge-pump, wherein the charge-pump regulator voltage generator comprises one of a static charge-pump regulator voltage generator or a dynamic charge-pump regulator voltage generator.

4. The driver circuit as claimed in claim 3 , wherein the dynamic charge-pump regulator voltage generator comprises:
a comparator configured to compare a portion of a controllable current target value and a further forward biased modeled voltage generator configured to model the laser diode; and
a further switch circuit configured to couple the output of the charge-pump to the further forward biased modeled voltage generator in response to the charge-pump being enabled and couple the positive supply rail to the further forward biased modeled modelled voltage generator in response to the charge-pump being disabled.

5. The driver circuit as claimed in claim 1 , wherein the second switch circuit comprises a single switch.

6. The driver circuit as claimed in claim 1 , wherein the second switch circuit comprises a bulk switch.

7. The driver circuit as claimed in claim 6 , wherein the bulk switch comprises:
an inverter configured to receive a charge-pump enable signal and configured to output an inverted charge-pump enable signal;
a first PMOS transistor configured with a gate node coupled to the inverted charge-pump enable signal, a source node coupled to a charge-pump output and a bulk node and drain node coupled to a bulk switch output;
a second PMOS transistor configured with a source node coupled to a lower voltage input and a bulk node and drain node coupled to the bulk switch output;
a third PMOS transistor configured with a drain node coupled to a gate node of the second PMOS transistor, a source node coupled to the charge-pump output, a bulk node coupled to the bulk switch output and a gate node coupled to the inverted charge-pump enable signal; and
a NMOS transistor configured with a drain node coupled to the gate node of the second PMOS transistor, a source node and a bulk node coupled to a ground node and a gate node coupled to the inverted charge-pump enable signal.

8. A range detector comprising:
a laser diode;
a charge-pump configured to generate an output boosted positive supply rail voltage;
a switch circuit configured to couple the output of the charge-pump to a terminal of the laser diode and to isolate the positive supply rail from the terminal of the laser diode in response to the charge-pump being enabled;
clocking circuitry;
a first state machine circuit configured to confirm operations of the clocking circuitry;
a second state machine circuit configured to confirm operations of the charge-pump and switch circuit; and
a third state machine circuit configured to confirm the operations of the charge-pump, wherein the operations of the third state machine circuit are initialized by the operations of the second state machine circuit.

9. The range detector as claimed in claim 8 , wherein the switch circuit is further configured to isolate the output of the charge-pump from the terminal of the laser diode and to couple the positive supply rail to the terminal of the laser diode in response to the charge-pump being disabled.

10. The range detector as claimed in claim 8 , further comprising:
a drive transistor configured to supply the laser diode with a controllable current;
a regulator configured to control the drive transistor, wherein the regulator comprises an input for indicating a controllable current target value and a forward biased modeled voltage generator configured to model the laser diode; and
a further switch circuit configured to couple the output of the charge-pump to the regulator in response to the charge-pump being enabled and couple the positive supply rail to the regulator in response to the charge-pump being disabled.

11. The range detector as claimed in claim 8 , further comprising a charge-pump regulator voltage generator configured to supply an input voltage to the charge-pump, wherein the charge-pump regulator voltage generator comprises one of a static charge-pump regulator voltage generator or a dynamic charge-pump regulator voltage generator.

12. The range detector as claimed in claim 11 , wherein the dynamic charge-pump regulator voltage generator comprises:
a comparator configured to compare a portion of a controllable current target value and a further forward biased modeled voltage generator configured to model the laser diode; and
a further switch circuit configured to couple the output of the charge-pump to the further forward biased modeled voltage generator in response to the charge-pump being enabled and couple the positive supply rail to the further forward biased modeled voltage generator in response to the charge-pump being disabled.

13. The range detector of claim 8 , wherein the switch circuit comprises a bulk switch comprising:
an inverter configured to receive a charge-pump enable signal and configured to output an inverted charge-pump enable signal;
a first PMOS transistor configured with a gate node coupled to the inverted charge-pump enable signal, a source node coupled to a charge-pump output and a bulk node and drain node coupled to a bulk switch output;
a second PMOS transistor configured with a source node coupled to a lower voltage input and a bulk node and drain node coupled to the bulk switch output;
a third PMOS transistor configured with a drain node coupled to a gate node of the second PMOS transistor, a source node coupled to the charge-pump output, a bulk node coupled to the bulk switch output and a gate node coupled to the inverted charge-pump enable signal; and
a NMOS transistor configured with a drain node coupled to the gate node of the second PMOS transistor, a source node and a bulk node coupled to a ground node and a gate node coupled to the inverted charge-pump enable signal.

14. A method for driving a laser diode, the method comprising:
supplying the laser diode with a controllable current using a drive transistor;
controlling the drive transistor with a regulator configured to receive a controllable current target value;
enabling a charge-pump to generate an output boosted positive supply rail voltage;
coupling the output

Assignees

• St Microelectronics Res & Dev Ltd

Inventors

• Lee Denise
• Storm Graeme
• Venugopalan Nair Jalajakumari Aravind
• Alexandropoulos Alexios

Classifications

• H01S5/06835 Primary

  Stabilising during pulse modulation or generation · CPC title

• H02M3/07

  using capacitors charged and discharged alternately by semiconductor devices with control electrode {, e.g. charge pumps} · CPC title

• H01S5/06825

  Protecting the laser, e.g. during switch-on/off, detection of malfunctioning or degradation · CPC title

• H01S5/183

  having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] · CPC title

• G01S17/06

  Systems determining position data of a target · CPC title