EDITOR’S NOTE
Not your parents’ power supply
The programmable power supply has often been considered an afterthought. You may need to upgrade your communications test set regularly to meet the latest Wi-Fi or 3GPP standards, or you may need a new oscilloscope with higher bandwidth, but when it comes to power supplies, volts are still volts and amps are still amps, right?
If this truism were ever correct, it’s becoming more and more outdated as applications such as the IoT and renewable energy and enabling technologies such as wide-bandgap power semiconductors come to the fore. As Ron Wilcox, senior director of power test engineering at Analog Devices Inc., put it, “Twenty-five years ago, I did not think one would be concerned with microvolts and picoamps in power semiconductor test, but we now find ourselves measuring just those, and often in the face of challenges like > 100 VCM or in noisy environments.”
“Power supplies continue to become more specialized,” said Bill Griffith, who works at product marketing at Keysight Technologies. “Research and design engineers working on the bench want a quiet power supply with multiple outputs and a large display. Bench power supplies need to have a fast transient response to simulate a battery. System engineers want a high-density power supply that requires very little space in their ATE rack.”
Griffith added that engineers can struggle to simulate and characterize real-world devices. “Power supplies often require higher output bandwidth along with better measurement systems for accurately characterizing devices,” he said, adding by way of example, “IoT devices pull current in short bursts that are difficult to measure accurately. Underestimating the power in each burst can lead to overstated run times.”
In addition, “The need to test 2-quadrant devices such as batteries and bidirectional converters and inverters are increasing,” Griffith said. “Having a single solution that can source and sink current simplifies test setups.”
In addition, he said, “For sink-mode applications requiring 5 kW to hundreds of kWs or more, regenerative power supplies provide higher efficiency and a smaller footprint. A regenerative power supply needs less space as it recycles power back to the grid instead of dissipating the power locally.”
EA Elektro-Automatik managing director Eric Turner commented on the benefits wide-bandgap technology brings to power supplies. “EA Elektro-Automatik’s latest generation of SiC switching devices uses magnetic components with distributed air gaps and profile winding technology resulting in a reduction in size that is truly remarkable,” Turner said. He added that control circuitry is continuing to move from analog to digital. “Digital architecture using FPGA-based controls to the amplifier improves load-regulation response and opens the door for additional features like arbitrary waveform generation and advanced measurements,” he said.
Flexibility in a power-supply system can be as important as performance, efficiency, and size. “System flexibility is important since many of the eMobility and renewable applications are in their early stages of development,” said Turner. “Often enough, existing and certainly future requirements are not fully understood, so customers want flexibility and modularity.”
Griffith also sees a need for flexibility. “Most automated tests benefit from a modular solution that allows the customization of individual outputs,” he said. “Modules allow quick reconfiguration to meet the needs of an evolving test plan.”
So if you have some old programmable supplies in your lab, it may be time to reevaluate them with respect to performance and size as well as features like bidirectional operation and reconfigurability. For more, see our reports on power semiconductor test and power supplies and loads in this issue.
Rick Nelson
Contributed Technical Editor