Taming the Nanosecond Beast: Without Accurate GaN/SiC Dynamic Testing, EV Range is Just a Guess

Key Takeaway: Without This Test, Next-Generation Technology Stalls

Imagine a traditional silicon power device (MOSFET) as a slightly slow-reacting water faucet. When you turn it off, the water flow stops gradually. While some water (energy) is wasted during this process, the operation is smooth. Now, picture a GaN or SiC device as a massive sluice gate that can slam shut in a millionth of a second. This incredible speed saves enormous amounts of energy, but just like slamming a gate causes a violent "water hammer" effect, it induces destructive voltage spikes (overshoot) and oscillations (ringing) in the circuit. If engineers cannot see and quantify this nanosecond "water hammer" with precision tools, they cannot design reliable circuits to control it. The result is catastrophic: poor efficiency at best, and outright device failure at worst. In short, without advanced dynamic characterization technology, we cannot harness the power of GaN and SiC, and goals like extending EV range or boosting server efficiency will remain unattainable.

The Technology Explained: Principles and Unprecedented Challenges

Yesterday's Bottleneck: Why Traditional Methods Are No Longer Sufficient

In the age of silicon, switching speeds were in the microsecond range and frequencies were relatively low. Engineers could use standard high-voltage differential probes with an oscilloscope to get a decent picture of switching behavior. The minor effects of the probe on the circuit and ambient noise were not the primary concern.

The arrival of GaN and SiC, however, compressed switching times by a factor of 10 to 100, plunging measurements into the nanosecond domain. This created three critical, show-stopping challenges:

1. Massive Common-Mode Voltage Interference: When a GaN device switches in an 800V EV battery system, the entire measurement loop is "contaminated" by this rapidly changing voltage. This is like trying to measure a tiny ripple in a glass of water while standing on the deck of a violently pitching ship. The ship's violent motion (the common-mode voltage) completely overwhelms a traditional differential probe, making it impossible to see the ripple (the true differential signal).

2. Probe's "Parasitic Capacitance" Effect: Any probe that touches a circuit adds a tiny amount of capacitance. In a slow system, this is a negligible "leak." But at the ultra-high switching speeds of GaN/SiC, this tiny leak becomes a gaping hole, significantly altering the device's actual switching behavior. The measurement becomes "visible but not accurate" because you are no longer observing the device's true performance.

3. The Challenge of Probing in Tight Spaces: To maximize performance, GaN/SiC circuit layouts are extremely compact, often leaving no ideal probing points. Safely and accurately connecting to a signal in a small space filled with high voltages and high-frequency noise is a major engineering feat in itself.

What Are the Core Principles of the Test?

To evaluate the dynamic performance of GaN/SiC devices accurately and repeatably in a lab setting, the industry has adopted a standardized method called the Double-Pulse Test (DPT).

The principle of DPT is to break down a complete switching cycle into two observable events:

1. The First Pulse (Establishes a Condition): A relatively long pulse is sent to turn on the device under test (DUT). The purpose of this pulse is to build up a target current in the circuit's inductor, simulating a real-world load condition. When this pulse ends, the device turns off, but the inductor current continues to flow through a diode.

2. The Second Pulse (The Measurement Event): After a very brief interval, a second, much shorter pulse is fired. This is the pulse of interest for measurement. On its rising edge, we can precisely observe the device's turn-on characteristics under a known current. On its falling edge, we observe the turn-off characteristics.

By analyzing the voltage (Vds) and current (Id) waveforms captured by the oscilloscope during this second pulse, engineers can calculate all critical dynamic parameters: switching times, energy loss, voltage/current overshoot, and ringing. This methodology provides a robust and repeatable way to characterize device performance.

This image illustrates the critical waveforms from a GaN/SiC power semiconductor Double-Pulse Test (DPT), essential for accurate dynamic switching characterization. The oscilloscope display (top) clearly shows the gate-source voltage (Vgs), drain-source voltage (Vds), and drain current (Ids) transitions, emphasizing the turn-on and turn-off events during the second pulse. The interface on the right demonstrates how automated software facilitates standard-compliant (e.g., JEDEC) measurements to analyze switching times and energy losses, a crucial step for ensuring the reliable operation of high-efficiency power conversion systems. (Image Source: Tektronix)

The Breakthrough of the New Generation of Test

To solve the aforementioned challenges and perform a perfect DPT, T&M technology has made a revolutionary leap, centered on fiber-optic isolation.

• Light Replaces Electricity to Isolate Interference: Pioneered by technologies like Tektronix's IsoVu probes, this approach converts the electrical signal at the probe tip into an optical signal, transmits it through a fiber-optic cable, and converts it back to an electrical signal at the oscilloscope. Because light is completely immune to electromagnetic interference, this creates an absolutely stable "bridge of light" between the pitching ship (the high common-mode circuit) and the observer (the oscilloscope). This provides an incredibly high Common Mode Rejection Ratio (CMRR), perfectly filtering out noise and allowing engineers, for the first time, to see the true nanosecond signal.
  

• Extremely Low Probe Loading: These new isolated probes have very low input capacitance, minimizing their impact on the DUT. This ensures the measurement is accurate and that "what you see is what you get."
  

• High Bandwidth & High-Resolution Oscilloscopes: To capture nanosecond details, the oscilloscope itself must have at least 1 GHz of bandwidth. Furthermore, to accurately calculate energy loss, the scope needs a 10-bit or 12-bit high-resolution ADC to discern millivolt-level details while measuring hundreds of volts.

Industry Impact & Applications

The Complete Validation Blueprint: From R&D to Mass Production

Challenge 1: Device Characterization in R&D

In the R&D phase, semiconductor companies (e.g., Infineon, Wolfspeed) and system designers need to perform exhaustive dynamic characterization of GaN/SiC dies and modules.

• Core Test Tools and Technical Requirements:

  • A high-bandwidth oscilloscope (1 GHz+), fiber-optically isolated differential probes, high-bandwidth current probes, and an Arbitrary Function Generator (AFG) to create the precise double pulse. The pursuit here is ultimate measurement accuracy. The probe's CMRR, bandwidth, and low input capacitance are the key specifications that determine success or failure.

Challenge 2: In-System Integration and Validation

Power system engineers must validate device performance within the final product (e.g., an EV inverter) and optimize the gate driver and layout design to suppress overshoot and ringing.

• Core Test Tools and Technical Requirements:

  • The tools are similar to R&D, but the emphasis is on stable measurements in a noisy, real-world electromagnetic environment. The focus is on analyzing the interaction between the device and the surrounding circuit, such as optimizing the gate drive waveform to achieve the best trade-off between switching loss and EMI.

Challenge 3: Quality and Throughput in Mass Production

On the production line, a full DPT is not feasible. The goal shifts to screening qualified devices or modules in seconds.

• Core Test Tools and Technical Requirements:

  • Automated Test Equipment (ATE) is central. The comprehensive DPT from the lab is abstracted into a few key parameter checks, such as Rds(on) under specific conditions and switching times. Establishing a strong correlation between lab and production measurements is critical for ensuring consistent product quality.

King of Applications: Which Industries Depend on It?

Accurate GaN/SiC dynamic testing is the foundation upon which several trillion-dollar industries are being built:

• Electric Vehicles (EVs): Directly impacts the efficiency of the traction inverter (motor drive), on-board charger (OBC), and DC-DC converters. Higher efficiency means longer range, faster charging, and lighter cooling systems.

• AI Data Centers & Servers: The efficiency of Power Supply Units (PSUs) is a key factor in a data center's total energy cost (PUE). Every 1% efficiency gain saves enormous amounts in electricity and cooling expenses.

• Renewable Energy: Solar inverters and wind turbine converters rely on efficient power conversion to feed maximum energy into the grid. GaN and SiC significantly reduce the energy lost during this conversion process.

The Road Ahead: Adoption Challenges and the Next Wave

The primary challenge today is to transition complex lab-grade test setups into easier-to-use and more cost-effective integrated solutions. The next wave will be integration and intelligence. Test instruments will evolve from mere measurement tools to complete characterization suites with built-in, automated test programs compliant with international standards (like JEDEC), capable of performing a full analysis and generating reports with a single click. Furthermore, as GaN devices become more integrated (e.g., driver and transistor on a single chip), the need for non-invasive probing technologies for micro-scale spaces will become a new R&D hotspot.

An Investor's Perspective: Why the "Shovel-Selling" Business Merits Attention

In the global wave of electrification and green energy, GaN/SiC manufacturers are the dazzling gold miners. However, they also face fierce competition and the risks of technological disruption. The T&M companies providing GaN/SiC test solutions are the ones selling the most essential, high-precision "prospecting equipment" for this gold rush.

The value of this business lies in:

1. An Extremely High Technology Barrier: Only a handful of companies in the world can develop a probe that combines kilovolts of isolation with gigahertz of bandwidth and femtofarads of input capacitance. This capability is built on deep expertise in optics, materials science, and RF engineering.

2. Enabling the Entire Value Chain: From chip design and module packaging to system integration and final production, every link in the value chain depends on accurate dynamic testing. T&M companies are the enablers of the entire ecosystem.

3. Long-Term Demand Tied to Megatrends: As long as the push for higher efficiency, smaller size, and greater power density continues, the demand for testing ever-faster, higher-voltage power devices will only grow. This is a durable market tied directly to the global energy transition.

Therefore, to follow these T&M companies is to grasp the most fundamental and solid technological pulse of the electrification era. When power semiconductors switch too fast for the naked eye to see, the companies that provide the "eyes" to see and tame them hold undeniable value.