Double Pulse Testing Using a Keysight Function Generator

Double pulse testing is a standard method used to characterize the dynamic switching performance of power transistors or power stages in integrated circuits (ICs). This technique is widely used to measure switching losses, voltage overshoots, recovery characteristics, and overall transient behavior under specific conditions. It plays a critical role in designing and optimizing power electronics, especially for high-performance applications such as insulated gate bipolar transistors, metal-oxide-semiconductor field-effect transistors (MOSFETs), and advanced materials like silicon carbide (SiC) and gallium nitride (GaN).

Technically, the double pulse test focuses on analyzing the behavior of power devices during critical switching events: turn-on and turn-off. These events are fundamental in understanding energy losses, thermal stress, and reliability in high-performance applications. For a DC-DC converter IC with integrated MOSFETs as an example, the double pulse test measures switching losses and evaluates voltage spikes during turn-on and turn-off transitions. In addition to the semiconductor industry, electric vehicles, renewable energy systems, industrial automation, aerospace, and other industries depend heavily on insights from design pulse tests for the design and optimization of their systems.

The purposes of the double pulse test include the following:

• Dynamic analysis to capture real-time behavior during fast transitions.
• Efficiency evaluation to quantify the switching losses to enhance power efficiency.
• Reliability testing to identify vulnerabilities like voltage overshoots or diode recovery issues.
• Material comparison to facilitate the comparison of different material technologies and select the best case.

The double pulse test involves applying a controlled sequence of two pulses to the device under test (DUT). The waveform generated simulates real operational conditions, enabling detailed performance characterization. The first pulse magnetizes the load inductor to a target current level for simulating realistic operation. A recovery period follows the first pulse to prevent an incomplete recovery that could distort measurements or damage the DUT. Following the brief off period, the second pulse measures how the device behaves under nominal current flow, capturing critical switching parameters like switching losses, peak voltages, and recovery times.

To run the double pulse test, a function generator is required to supply the gate drive signals. For this application note, we use the Keysight FG33532A function / arbitrary waveform generator along with the 33503B BenchLink Waveform Builder Pro application to generate the double pulse signal.

The function generator used for this double pulse test is part of the Keysight Smart Bench Essentials Plus suite of instruments. This elevated set of basic instruments — power supply, waveform generator, digital multimeter, and oscilloscope — comes with proven pro-level measurement technologies designed to minimize measurement errors resulting from real-world factors to provide the accuracy and precision required for this application. The instruments include large color screen displays and graphical interfaces to visualize, analyze, and share test results quickly.

This application note outlines how to create a double pulse waveform using the BenchLink Waveform Builder Pro application. After generating the waveform, we import it directly into the Smart Bench Essentials Plus function generator. Finally, we observe the created pulses using an oscilloscope.

Double pulse testing provides critical insight into the switching behavior of power devices, enabling designers to optimize efficiency, reliability, and thermal performance. By using the Keysight Smart Bench Essentials Plus function generator, you can generate a standard double pulse signal to characterize your DUT instead of investing in a high-cost pulse generator. This approach makes the double pulse test more accessible and cost-effective while providing precise and reliable measurements.