How to avoid current overshoot when the laser is powered on?

DC power supplies typically operate in two modes: constant voltage (CV) and constant current (CC), each governed by its own internal control loop. Most power supplies on the market today prioritize the CV loop, which means that when a load is applied, the voltage is controlled first, and the current is managed afterward. While this setup works for many applications, it can lead to issues in situations where precise current control is required, such as in high-speed testing or sensitive device validation. The IT6100B series of high-speed, high-precision programmable DC power supplies introduces a groundbreaking CC/CV priority concept, allowing users to choose which control loop takes precedence based on their specific needs.

This innovative approach gives engineers more flexibility and control over their test environments. With the ability to set the CC loop to a higher priority, the power supply can respond faster during startup, ensuring that current doesn’t overshoot, even at very low levels like 250mA. This feature is especially beneficial for testing delicate components such as lasers, where even a small current spike can cause damage.

In traditional power supplies, the CV loop is always prioritized, which can result in current overshoots during the initial phase of operation. This not only affects the performance of the tested devices but also increases the risk of failure. By contrast, the IT6100B series allows users to switch between CV and CC priorities through an intuitive menu interface, without the need for additional hardware. This makes it a cost-effective solution for multi-domain applications, from basic testing to complex aerospace and industrial systems.

Current priority mode characteristics at startup

Case Study: Laser Testing

In a typical laser testing scenario, the use of a conventional power supply with a voltage-priority mode often results in significant current overshoots. These spikes can be captured using an oscilloscope, showing erratic waveforms that may harm the laser or affect test accuracy. However, with the IT6100B series, the CC loop is given higher priority, allowing the power supply to react quickly and maintain stable current levels right from the start.

Voltage priority characteristics at startup

When the IT6100B is set to CC priority mode, the current rises rapidly but remains under strict control, preventing any unwanted overshoot. This ensures that the laser receives a clean, stable current, reducing the risk of damage and improving test reliability. The following images show the current waveform captured during startup, demonstrating the effectiveness of the CC priority setting.

Current priority characteristics at 5A startup

Current priority characteristics at 2.5A startup

Current priority characteristics at 250mA startup

The test results clearly show the advantages of the CC priority mode. In the voltage-priority mode, current overshoots are common, leading to unstable output. However, with the IT6100B’s CC priority, the system maintains tight control over the current, regardless of whether it starts at milliampere or ampere levels. This ensures consistent and reliable performance, making it ideal for precision testing applications.

The IT6100B series (ranging from 86W to 1200W) offers ultra-fast voltage rise times, with full-load response up to 500μs. It also features a resolution of 0.1mV and 0.01mA, making it suitable for demanding high-precision applications. The built-in USB, RS232, and GPIB interfaces allow for easy integration into automated test systems, while the panel supports list programming for advanced users. Whether you're working on aerospace power modules, medical devices, or industrial equipment, the IT6100B provides a versatile and powerful solution for your testing needs.