Monolithically integrated switching circuit for regulating the luminous power of a laser diode

• US 20030138010A1
• Filed: 11/01/2002
• Published: 07/24/2003
• Est. Priority Date: 05/02/2000
• Status: Abandoned Application

• Current Assignee: IC-Haus GmbH
• Original Assignee: IC-Haus GmbH
• Inventors: Herz, Manfred
• Application Number:
  US10/276,136
• Publication Number:
  US 20030138010A1
• Time in Patent Office: Days
• US Class Current: 372/38.02
• CPC Class Codes: H01S 5/042 Electrical excitation ; Circuits therefor monolithically integrated laser drive components H01S5/0261
• CPC Class Codes: H01S 5/06825 Protecting the laser, e.g. during switch-on/off, detection of malfunctioning or degradation
• CPC Class Codes: H01S 5/0683 by monitoring the optical output parameters

Abstract

The invention relates to a monolithic integrated circuit for controlling the light power of a laser diode optically coupled to at least one photodiode. Laser diodes are sensitive semiconductor components which can be destroyed in particular when current/voltage transients occur. It is an object of the invention, therefore to provide a monolithic integrated circuit for controlling the light power of a laser diode which can comprehensively protect a connected laser diode against destruction. To that end, the circuit has first terminals (40, 42, 44, 46, 48) for connecting at least one laser diode (50) and for connecting at least one photodiode (60) optically coupled thereto, an integrated device (90, 100) for controlling the control current of at least one connected laser diode (50), second terminals (20, 22) for applying a supply voltage, and an integrated device (150) connected to the second terminals and serving to suppress current and/or voltage transients.

Claims

1. A monolithic integrated circuit (10) for controlling the light power of a laser diode (50) optically coupled to at least one photodiode (60), having

first terminals (40, 42, 44, 46, 48) for connecting at least one laser diode (50) and for connecting at least one photodiode (60) optically coupled thereto,

an integrated device (90, 100) for controlling the control current of at least one connected laser diode (50),

second terminals (20, 22) for applying a supply voltage, and having an integrated device (150) connected to the second terminals and serving to suppress current and/or voltage transients.

2. The monolithic integrated circuit as claimed in claim 1, which has an integrated recovery device (120), which is connected antiparallel with respect to a connected laser diode (50).

3. The monolithic integrated circuit as claimed in claim 1 or 2;

which has a first integrated detector (145) for detecting the magnitude of the control current fed to a connected laser diode (50) for controlling the light power.

4. The monolithic integrated circuit as claimed in one of claims 1 to 3, which has a second integrated detector (140) for detecting the temperature within the circuit.

5. The monolithic integrated circuit as claimed in claim 3 or 4, which has an integrated switching device (110), which, responding to the output signals of the first and/or second detector (140, 145), limits the control current fed for controlling the light power of the laser diode (50) to a predetermined value.

6. The monolithic integrated circuit as claimed in claim 5, which has a storage device (130) assigned to the switching device (110) and serving to store predetermined states, represented by the output signals of the first and/or second detector, in order to permanently activate the switching device for limiting the control current to the predetermined value.

7. The monolithic integrated circuit as claimed in claim 6, wherein,

responding to a renewed application of the supply voltage to the second terminals (20, 22), the content of the storage device (130) is cleared in order to deactivate the switching device (110).

8. The monolithic integrated circuit as claimed in claim 6 or 7, wherein the storage device (130) is an RS flip-flop.

15. The monolithic integrated circuit as claimed in one of claims 1 to 14, wherein the integrated device for controlling the control current of at least one connected laser diode (50) contains a differential amplifier (90), whose first input is provided for connection to a photodiode (60), whose second input is connected to a reference voltage source (95) and whose output is connected to the input of a power driver (100) which supplies the controlled control current for controlling the light power of a connected laser diode (50).

9. A monolithic integrated circuit (10) for controlling the light power of a laser diode (50) optically coupled to at least one photodiode (60), having

first terminals (40, 42, 44, 46, 48) for connecting at least one laser diode and for connecting at least one photodiode (60) optically coupled thereto,

an integrated device (90, 100) for controlling the control current of at least one connected laser diode (50),

second terminals (20, 22) for applying a supply voltage, and having an integrated switching device (110), which, responding to the deviation of at least one monitored signal from a predetermined desired value, limits the control current fed for controlling the light power of the laser diode (50) to a predetermined value.

10. The monolithic integrated circuit as claimed in claim 9, which has a first integrated detector (145) for monitoring a first signal which indicates that a predetermined magnitude of the control current fed to a connected laser diode (50) for controlling the light power has been exceeded.

11. The monolithic integrated circuit as claimed in claim 9 or 10, which has a second integrated detector (140) for monitoring a second signal which indicates that a predetermined temperature within the circuit has been exceeded.

12. The monolithic integrated circuit as claimed in one of claims 9 to 11, which has a storage device (130) assigned to the switching device (110) and serving to store at least one state, represented by the at least one monitored signal, in order to permanently activate the switching device (110) for limiting the control current to the predetermined value.

13. The monolithic integrated circuit as claimed in claim 12, wherein, responding to a renewed application of a supply voltage to the second terminals (20, 22), the content of the storage device (130) is cleared in order to deactivate the switching device (110).

14. The monolithic integrated circuit as claimed in claim 12 or 13, wherein the storage device (130) is an RS flip-flop.