High-power semiconductor laser drive power protection circuit scheme - Power Circuit - Circuit Diagram

1. Introduction

Semiconductor lasers (LDs), renowned for their compact size, lightweight design, high energy conversion efficiency, and extended operational lifespan, have become indispensable in industries such as industrial manufacturing, military applications, and advanced medicine. These lasers operate via current injection as their primary excitation method. The reliability and longevity of the laser largely depend on the performance of the driving power supply. Therefore, designing a power supply that ensures stable performance and dependable operation is crucial.

In recent years, numerous research institutions have focused on developing a series of LD current sources to support the stable functioning of these lasers. However, the inherent sensitivity of semiconductor lasers makes them vulnerable to surge spikes. This necessitates robust surge suppression and current-limiting mechanisms within the driving circuitry. Traditional protection measures like slow-start circuits, transient voltage suppressors (TVS), and current-limiting circuits often fall short when dealing with high-power lasers due to their delicate nature and large operational currents.

This paper proposes a novel protection circuit design for high-power semiconductor lasers. By incorporating dual current-limiting functionality and forced absorption/isolation of surge spikes, this circuit offers superior protection against potential damage. This approach not only extends the laser's operational lifespan but also enhances overall system reliability, making it highly applicable in real-world scenarios.

2. Principle Analysis

2.1 Damage Mechanism of Semiconductor Lasers

Under normal operating conditions, semiconductor lasers exhibit a remarkably long service life. However, adverse operating conditions can lead to rapid performance degradation or even catastrophic failure. Statistical data reveals that sudden failures in semiconductor lasers occur predominantly due to surge-induced breakdowns. Consequently, safeguarding the laser from surges and extending its operational lifetime remains a critical focus in the development of high-power laser driver protection circuits. Key considerations include:

Firstly, ensuring the laser operates within the specified current limits is essential, requiring a robust current-limiting circuit. Secondly, providing a strong surge-absorption circuit is necessary to mitigate grid surges and lightning-induced voltages. Thirdly, given the laser's sensitivity to current fluctuations, a slow-start circuit is indispensable to prevent damage during power-on/off transitions.

2.2 Characteristics of Traditional Protection Circuits

Traditional protection circuits, while effective in certain aspects, have limitations. Adding TVS devices to the primary and secondary sides of the isolation transformer helps suppress excessive voltage spikes, thanks to their rapid response capability. However, the effectiveness of this solution depends heavily on the TVS response speed. Additionally, incorporating a π-type low-pass filter network between the DC power supply and the laser can help filter out surge voltages. While passive filtering methods like this are useful for reducing ripple and absorbing smaller surges, they prove ineffective for handling larger voltage spikes.

Slow-start circuits play a vital role in gradually increasing the voltage supplied to the laser during power-on/off cycles, thereby minimizing the risk of device damage due to abrupt changes. Current-limiting circuits are equally important, though conventional designs typically feature single-stage current limitation, which may not suffice for high-power lasers.

2.3 Features of the Proposed Circuit Design

This new circuit design builds upon the strengths of traditional solutions while addressing their limitations. Firstly, it integrates a soft-start mechanism to prevent device damage during initial power-up. Secondly, a dual current-limiting circuit ensures that the current flowing through the laser remains within safe limits at all times. Thirdly, the use of power MOS transistors enables active surge absorption or isolation, offering enhanced protection against surge-related damage. Finally, the circuit implements a gradual start-stop process to minimize surge generation during laser operation, further safeguarding the device.

In summary, this innovative design represents a significant advancement in semiconductor laser protection technology. By combining multiple protective elements into a cohesive system, it delivers superior performance and reliability, making it a promising solution for modern high-power laser applications.