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

1 Introduction

Semiconductor lasers (LDs) possess several advantages such as compact size, lightweight, high conversion efficiency, and extended operational lifespan. These attributes have led to their widespread use across industries including industrial applications, military sectors, and medicine. LDs operate via current injection as their excitation mode, meaning their longevity and performance heavily rely on the quality of the driving power supply employed. It is thus crucial to develop a drive power solution that ensures LD technology's requirements are met while maintaining stable and reliable operations. In recent years, numerous research institutions have focused on developing a series of LD current sources to support LD functionality. However, the inherent sensitivity of semiconductor lasers to sudden surges poses significant challenges. To address these issues, various protective measures are integrated into the drive power supply design, such as slow-start circuits, transient voltage suppression (TVS) absorbers, and current-limiting circuits, to mitigate potential damage from surges and excess currents. Nevertheless, conventional methods often fall short when dealing with the high currents associated with powerful semiconductor lasers, which are particularly delicate. This paper proposes a novel high-power device featuring forced absorption or isolation surge protection along with dual current-limiting mechanisms, offering robust safeguards against laser damage and demonstrating promising real-world applicability.

2 Principle Analysis

2.1 Damage Mechanism of Semiconductor Lasers

When functioning correctly, semiconductor lasers exhibit a long operational life. However, improper usage conditions can lead to rapid degradation or even catastrophic failure. Statistical data indicates that sudden failures occur frequently among semiconductor lasers, with surge-induced breakdown being the most common cause. Consequently, devising strategies to safeguard these lasers and prolong their service life remains paramount in advancing high-power semiconductor laser driver protection technologies. Key considerations include:

1) Ensuring operation within specified current limits necessitates a dependable current-limiting circuit.

2) Surge suppression circuits must be robust enough to counteract grid surges and lightning-induced voltages.

3) Due to their sensitivity to current changes, lasers require gradual startup processes to minimize stress during initial power-up or shutdown phases.

2.2 Characteristics of Traditional Protection Circuits

1) Adding TVS components at both primary and secondary transformer stages exploits their fast response times to clamp excessive grid surges and lightning voltages effectively. While effective, this approach depends heavily on the TVS response speed; slower responses may fail to adequately suppress surges.

2) Incorporating a π-type low-pass filter network between the DC source and the laser helps eliminate residual surge voltages. Utilizing shielded inductors and non-inductive surge absorbers enhances performance but proves ineffective against large-scale surges, relying instead on passive filtering techniques that reduce ripple noise rather than absorbing major disturbances.

3) Implementing a slow-start circuit minimizes immediate voltage application upon turning on/off the system, preventing abrupt impacts on connected components and reducing distributed inductance-related surge effects—a critical yet straightforward implementation.

4) Current-limiting circuits play an essential role in protecting against overcurrent scenarios; however, standard designs usually only offer single-level current regulation.

2.3 Unique Features of This Circuit Design

1) Building upon successful aspects of previous designs, this work introduces a soft-start mechanism at power-on to prevent equipment damage during initial startup surges—a concept already well-established in literature, hence briefly outlined here.

2) A dual current-limiting architecture ensures tighter control over current flowing through the semiconductor laser, enhancing reliability under varying load conditions.

3) Power transistors (MOSFETs) serve as switching elements enabling either forced surge absorption or complete isolation, providing enhanced surge protection compared to traditional setups.

4) Gradual startup procedures implemented during both activation and deactivation phases help minimize operational surges, ensuring safer and more consistent laser performance throughout its lifecycle.