The protection circuit for the semiconductor laser driving power supply.

The protection circuit for the semiconductor laser driving power supply.

Mar 26, 2021

LD is the laser with current injection as the excitation method. Its life span and working characteristics depend to a large extent on the performance of the driving power supply.


Laser Diode

The nature of the semiconductor laser itself determines its poor surge resistance, which requires high stability of the driving power supply and low surge impact. Therefore, various protection circuits are required in the driving power supply to meet actual requirements. Slow start circuits, TVS (transient suppressor) absorption circuits, current limiting circuits, etc. are usually used to prevent surges and excessive currents.


Semiconductor lasers being used in normal conditions have a long working life. However, under improper working conditions, it will cause rapid deterioration of performance and even failure. Statistics show that the sudden failure of semiconductor lasers is more than half of the probability due to surge breakdown. Therefore, how to protect the semiconductor laser and prolong the life span of the semiconductor laser is an important issue in the development of a high-power semiconductor laser drive power protection circuit.


Analysis of Damage Mechanism of Semiconductor Laser:

1) The laser must work within the limited current, and a safe and reliable current limiting circuit is indispensable.

2) In order to prevent the surge impact of the drive power supply, there must be a relatively strong surge absorption circuit.

3) Since the laser is a sensitive current component, the drive current cannot be directly applied to both ends of the laser. The slow start circuit is also essential for the protection of the laser.


Characteristics of traditional protection circuit:


1) TVS devices are added to the primary and secondary sides of the isolation transformer to use its high-speed response characteristics to suppress excessive grid surge voltage and lightning induced voltage. This kind of measure is more effective, but it is limited by the response speed of TVS. If the response speed does not meet the requirements, the surge impact cannot be well suppressed.


2) Add a π-type low-pass filter network between the DC power supply and the laser to further filter out the surge voltage. If shielded inductors and non-inductive surge absorption capacitors can be used, the performance will be better. This is actually passive filtering, which is effective for reducing power supply ripple and absorbing relatively small surges. But for large surges, this circuit will fail.

3) Add a slow start circuit between the DC power supply and the laser to slowly increase the voltage supplied to the laser to avoid the impact on the device when the power is suddenly turned on or off. At the same time, this action can also avoid the distributed inductance in the circuit. Surge impact. This circuit is essential and effective.

4) Current limiting circuit. This kind of circuit is also indispensable, but the traditional current-limiting circuit is usually a single-channel current-limiting.


Well, with further research and development, circuit design will continue to be optimized.


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