USH322H - Laser diode power controller - Google Patents

Laser diode power controller Download PDF

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Publication number
USH322H
USH322H US06/757,222 US75722285A USH322H US H322 H USH322 H US H322H US 75722285 A US75722285 A US 75722285A US H322 H USH322 H US H322H
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US
United States
Prior art keywords
laser diode
output
power
laser
pass transistor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US06/757,222
Inventor
Brent S. Simons
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
United States, SUBJECT TO A NONEXCLUSIVE AND ROYALTY-FREE LICENSE WHICH IS HEREBY RESERVED TO CONTRACTOR
US Department of Navy
Original Assignee
US Department of Navy
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by US Department of Navy filed Critical US Department of Navy
Priority to US06/757,222 priority Critical patent/USH322H/en
Assigned to UNITED STATES OF AMERICA SUBJECT TO A NONEXCLUSIVE AND ROYALTY-FREE LICENSE WHICH IS HEREBY RESERVED TO THE CONTRACTOR. reassignment UNITED STATES OF AMERICA SUBJECT TO A NONEXCLUSIVE AND ROYALTY-FREE LICENSE WHICH IS HEREBY RESERVED TO THE CONTRACTOR. ASSIGNMENT OF ASSIGNORS INTEREST. SUBJECT TO LICENSE RECITED THIS INSTRUMENT IS ALSO SIGNED BY ITEK CORPORATION. Assignors: SIMONS, BRENT S.
Application granted granted Critical
Publication of USH322H publication Critical patent/USH322H/en
Abandoned legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • 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
    • H01S5/00—Semiconductor lasers
    • H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
    • H01S5/068—Stabilisation of laser output parameters
    • H01S5/06825—Protecting the laser, e.g. during switch-on/off, detection of malfunctioning or degradation

Definitions

  • This invention relates to an electrical control circuit and more particularly to a laser diode power supply current control circuit.
  • Another object of the present invention is to control the current to a laser diode to maintain a constant current output and be free of transient voltages which might damage the laser diode during turn on and off.
  • Still another object of the present invention is to maintain a constant laser diode power output using a proportional controller which drives a series pass transistor to regulate laser diode current and the intensity of the laser diode output.
  • a laser diode power supply that uses a proportional controller that drives a series pass transistor to regulate laser diode current and the intensity of the laser diode output.
  • the purpose of the controller is to maintain constant laser output power when its unregulated output power would otherwise gradually decrease with age.
  • the laser diode includes a detector that samples light emitted from the laser diode. The output of the detector is amplified and compared to a reference voltage in an integrator. The output of the integrator controls a series pass transistor that varies to power to the laser diode to provide a constant laser diode power output.
  • the controller also includes power limiting and transient voltage protection circuits.
  • FIG. 1 is a pictorial drawing of the laser diode assembly which uses the laser diode power supply controller of the present invention.
  • FIG. 2 is a schematic diagram of the laser diode power supply controller of the present invention.
  • FIG. 1 is shown a pictorial view of the solid-state laser diode assembly 11 which uses the laser diode power supply controller of the present invention.
  • the laser diode assembly of FIG. 1 includes base 13, laser diode 15, photodetector 17, temperature sensor 19, calibration resistor 21 wire bond connection pads 23 and connecting wires 25.
  • Controller 29 includes transimpedance amplifier 31, integrator 33, series pass transistor 35, power source 36, regulator 37, current sense amplifier 39, reference voltage device 41 and transient voltage protection circuit 43.
  • the outputs of laser diode 15 and photodetector 16 are connected to controller 29 as illustrated.
  • the reference voltage for integrator 33 is externally established by variable resistor 45. Circuit grounding and electrical parameters for this embodiment are as illustrated in FIG. 2.
  • An external laser enable signal is applied to one of the inputs to regulator 37.
  • the system requirements of the illustrated embodiment are to provide a control circuit 29 that is capable of driving a 10 milliwatt laser diode which maintains a constant laser output power level by varying the laser drive current as the laser ages.
  • a silicon detector located near the laser provides a current output proportional to laser power for feedback control purposes.
  • the controller has the ability to inhibit laser output by an external control level.
  • the laser diode power supply employs a proportional controller which drives a series pass transistor to regulate laser diode current and thus the intensity of the laser diode output. Since the output power of a laser diode gradually decreases with age, it is necessary to provide a compensation circuit that will maintain constant laser output power over time.
  • the laser diode hybrid 15 contains a small silicon detector 16 mounted directly behind the laser diode chip which samples a small amount of light emitted from the back facet of the laser.
  • the output current of silicon detector 16 is typically around 50 micro-amps for a 10 milliwatt laser. This current is converted to a voltage output by transimpedance amplifier 31.
  • Integrator 33 compares the power sense output voltage of amplifier 31 to a preset reference level, as determined by variable resistor 45 and reference voltage device 41, which sets the desired laser output level of10 milliwatts, for example. Any change in detected light adjusts the laser drive current in the proper direction to maintain a constant output power level.
  • Regulator 37 in this embodiment is an integrated circuit controlled by an external voltage level.
  • An external input (laser enable) from temperature controller 19 prevents the regulator from turning on unless the laser temperature is within 5 degrees of set point.
  • the regulator employs a slow turn on and off circuit to prevent the possibility of voltage transients occurring during power-up and shut down.
  • Current sense amplifier 39 samples the laser drive current and provides a current limit control to regulator 37 which prevents damage to the laser diode.

Abstract

A laser diode power supply that uses a proportional controller that drives series pass transistor to regulate laser diode current and the intensity of the laser diode output. The purpose of the controller is to maintain constant laser output power when its unregulated output power would otherwise gradually decrease with age. The laser diode includes a detector that samples light emitted from the laser diode. The output of the detector is amplified and compared to a reference voltage in an integrator. The output of the integrator controls a series pass transistor that varies to power to the laser diode to provide a constant laser diode power output. The controller also includes power limiting and transient voltage protection circuits.

Description

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electrical control circuit and more particularly to a laser diode power supply current control circuit.
2. Description of the Prior Art
Many different types of current control circuits have been developed for use with electronic equipment. However, the unique problems associated with certain laser diode technology has not been solved with prior circuitry. One of these problems has been that the power output of a laser diode decreases as it ages and it is desirable to maintain a constant power level over its entire life cycle. It is also important that the control circuit have the ability to inhibit laser output by an external control level and be free of transient voltages which might damage the laser diode during turn on and off. The present invention overcomes these difficulties by employing a proportional controller which drives a series pass transistor to regulate laser diode current and thus the intensity of the laser diode output. A silicon detector located near the laser provides a current output proportional to laser power for feedback purposes.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a laser diode power supply controller for maintaining a constant laser output power level by varying the laser drive current as the laser ages.
Another object of the present invention is to control the current to a laser diode to maintain a constant current output and be free of transient voltages which might damage the laser diode during turn on and off.
Still another object of the present invention is to maintain a constant laser diode power output using a proportional controller which drives a series pass transistor to regulate laser diode current and the intensity of the laser diode output.
These and other objectives are accomplished by a laser diode power supply that uses a proportional controller that drives a series pass transistor to regulate laser diode current and the intensity of the laser diode output. The purpose of the controller is to maintain constant laser output power when its unregulated output power would otherwise gradually decrease with age. The laser diode includes a detector that samples light emitted from the laser diode. The output of the detector is amplified and compared to a reference voltage in an integrator. The output of the integrator controls a series pass transistor that varies to power to the laser diode to provide a constant laser diode power output. The controller also includes power limiting and transient voltage protection circuits.
Other advantages and features will become apparent from the following description of the preferred embodiment when considered in conjunction with the accompanying drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial drawing of the laser diode assembly which uses the laser diode power supply controller of the present invention; and
FIG. 2 is a schematic diagram of the laser diode power supply controller of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 is shown a pictorial view of the solid-state laser diode assembly 11 which uses the laser diode power supply controller of the present invention. The laser diode assembly of FIG. 1 includes base 13, laser diode 15, photodetector 17, temperature sensor 19, calibration resistor 21 wire bond connection pads 23 and connecting wires 25.
In FIG. 2 is shown the laser diode power supply controller 29 of the present invention. Controller 29 includes transimpedance amplifier 31, integrator 33, series pass transistor 35, power source 36, regulator 37, current sense amplifier 39, reference voltage device 41 and transient voltage protection circuit 43.
The outputs of laser diode 15 and photodetector 16 are connected to controller 29 as illustrated. The reference voltage for integrator 33 is externally established by variable resistor 45. Circuit grounding and electrical parameters for this embodiment are as illustrated in FIG. 2. An external laser enable signal is applied to one of the inputs to regulator 37.
The system requirements of the illustrated embodiment are to provide a control circuit 29 that is capable of driving a 10 milliwatt laser diode which maintains a constant laser output power level by varying the laser drive current as the laser ages. A silicon detector located near the laser provides a current output proportional to laser power for feedback control purposes. The controller has the ability to inhibit laser output by an external control level. The laser diode power supply employs a proportional controller which drives a series pass transistor to regulate laser diode current and thus the intensity of the laser diode output. Since the output power of a laser diode gradually decreases with age, it is necessary to provide a compensation circuit that will maintain constant laser output power over time.
The laser diode hybrid 15 contains a small silicon detector 16 mounted directly behind the laser diode chip which samples a small amount of light emitted from the back facet of the laser. The output current of silicon detector 16 is typically around 50 micro-amps for a 10 milliwatt laser. This current is converted to a voltage output by transimpedance amplifier 31. Integrator 33 compares the power sense output voltage of amplifier 31 to a preset reference level, as determined by variable resistor 45 and reference voltage device 41, which sets the desired laser output level of10 milliwatts, for example. Any change in detected light adjusts the laser drive current in the proper direction to maintain a constant output power level.
Regulator 37 in this embodiment is an integrated circuit controlled by an external voltage level. An external input (laser enable) from temperature controller 19 prevents the regulator from turning on unless the laser temperature is within 5 degrees of set point. In addition, the regulator employs a slow turn on and off circuit to prevent the possibility of voltage transients occurring during power-up and shut down. Current sense amplifier 39 samples the laser drive current and provides a current limit control to regulator 37 which prevents damage to the laser diode.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that with the scope of the appended claims the invention may be practiced otherwise than as specifically described.

Claims (3)

What is claimed is:
1. A power supply controller for a laser diode including:
(a) a detector for receiving light emitted from the back facet of the laser diode;
(b) an amplifier, an integrator, a reference voltage generator, a power source and a series pass transistor;
(c) the output of said detector being applied to the input of said amplifier, the output of said amplifier being applied to a first input of said integrator, the output of said reference voltage generator being applied to a second input of said integrator, the output of said integrator being applied to the base of said series pass transistor, the output of said power source being passed through said series pass transistor to the power input of said laser diode; whereby
(d) the voltage output of said reference voltage generator is selected to establish a preselected output power from said laser diode and said integrator provides an output signal to said series pass transistor to adjust the power applied to the power input of said laser diode to maintain constant laser output power.
2. The controller of claim 1 including:
(a) a regulator operably connected between said power source and said series pass transistor, said regulator being responsive to a laser enable signal and providing a slow increase of turn-on power and a slow decrease of turn-off power in response to said enable signal.
3. The controller of claim 2 including:
(a) a current sensing device operably connected between said series pass transistor and said laser diode and having its output connected to an input of said regulator to limit the maximum power applied to said laser.
US06/757,222 1985-07-22 1985-07-22 Laser diode power controller Abandoned USH322H (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US06/757,222 USH322H (en) 1985-07-22 1985-07-22 Laser diode power controller

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US06/757,222 USH322H (en) 1985-07-22 1985-07-22 Laser diode power controller

Publications (1)

Publication Number Publication Date
USH322H true USH322H (en) 1987-08-04

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US06/757,222 Abandoned USH322H (en) 1985-07-22 1985-07-22 Laser diode power controller

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5212370A (en) * 1990-11-20 1993-05-18 Ncr Corporation Apparatus and method for extending laser life by discontinuous operation
US5276697A (en) * 1992-11-04 1994-01-04 Eastman Kodak Company Laser diode automatic power control circuit with means of protection of the laser diode
US5396069A (en) * 1993-07-01 1995-03-07 The United States Of America As Represented By The Secretary Of The Air Force Portable monocular night vision apparatus
US5442510A (en) * 1993-06-23 1995-08-15 The United States Of America As Represented By The Secretary Of The Navy Control system for tracking nonlinear systems
US5515392A (en) * 1995-01-05 1996-05-07 Eastman Kodak Company Laser diode control circuit with power supply compensation network
WO1996018138A1 (en) * 1994-12-09 1996-06-13 Psc Inc. Laser drive and control systems useful for laser diode protection
WO1998018184A1 (en) * 1996-10-22 1998-04-30 Maxim Integrated Products, Inc. Laser diode having smooth enable apc circuit
US6185240B1 (en) * 1998-01-30 2001-02-06 Motorola, Inc. Semiconductor laser having electro-static discharge protection
US20040135565A1 (en) * 2002-10-10 2004-07-15 Douma Darin J. Microprocessor controlled boost converter
US20060187980A1 (en) * 2005-02-18 2006-08-24 Yun-Yuan Yeh Thin laser module
US20060291512A1 (en) * 2005-06-24 2006-12-28 Borschowa Lawrence A Apparatus and method for driving laser diodes

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5212370A (en) * 1990-11-20 1993-05-18 Ncr Corporation Apparatus and method for extending laser life by discontinuous operation
US5276697A (en) * 1992-11-04 1994-01-04 Eastman Kodak Company Laser diode automatic power control circuit with means of protection of the laser diode
EP0596357A1 (en) * 1992-11-04 1994-05-11 Eastman Kodak Company Laser diode automatic power control circuit with means of protection of the laser diode
US5442510A (en) * 1993-06-23 1995-08-15 The United States Of America As Represented By The Secretary Of The Navy Control system for tracking nonlinear systems
US5396069A (en) * 1993-07-01 1995-03-07 The United States Of America As Represented By The Secretary Of The Air Force Portable monocular night vision apparatus
WO1996018138A1 (en) * 1994-12-09 1996-06-13 Psc Inc. Laser drive and control systems useful for laser diode protection
US5666045A (en) * 1994-12-09 1997-09-09 Psc Inc. Laser drive and control systems useful for laser diode protection
US5515392A (en) * 1995-01-05 1996-05-07 Eastman Kodak Company Laser diode control circuit with power supply compensation network
WO1998018184A1 (en) * 1996-10-22 1998-04-30 Maxim Integrated Products, Inc. Laser diode having smooth enable apc circuit
US5802089A (en) * 1996-10-22 1998-09-01 Maxim Integrated Products, Inc. Laser diode driver having automatic power control with smooth enable function
US6185240B1 (en) * 1998-01-30 2001-02-06 Motorola, Inc. Semiconductor laser having electro-static discharge protection
US20040135565A1 (en) * 2002-10-10 2004-07-15 Douma Darin J. Microprocessor controlled boost converter
US20060187980A1 (en) * 2005-02-18 2006-08-24 Yun-Yuan Yeh Thin laser module
US20060291512A1 (en) * 2005-06-24 2006-12-28 Borschowa Lawrence A Apparatus and method for driving laser diodes
US7792166B2 (en) 2005-06-24 2010-09-07 Lockheed Martin Corporation Apparatus and method for driving laser diodes
US8170075B1 (en) 2005-06-24 2012-05-01 Lockheed Martin Corporation Method and apparatus for driving laser diodes

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Owner name: UNITED STATES OF AMERICA SUBJECT TO A NONEXCLUSIVE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. SUBJECT TO LICENSE RECITED THIS INSTRUMENT IS ALSO SIGNED BY ITEK CORPORATION.;ASSIGNOR:SIMONS, BRENT S.;REEL/FRAME:004451/0763

Effective date: 19850701

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