Vol.9, No.2

VXIplug&play Member Profile

Introducing Kepco

Q What business is Kepco engaged in?
A Kepco is engaged in the standard off-the-shelf merchant power supply business. I use those qualifiers because this business has many other niches - custom, captive supplier, build-to-order, and so on. We build both instrumentation power supplies and modular products that are integrated into larger products.

Our instrumentation power supplies have long featured programmability of both the voltage and current settings. Not too many years ago, programmability meant the ability to recognize and respond to an analog signal in the fashion of an amplifier. Kepco's analog-programmable power supplies were unique, offering a fast-responding output that allowed them a relatively wide bandwidth.

Most power supplies use a large output capacitor to provide an energy storage and to filter out ripple and noise components. Our specialty was creating a product that could function without such a capacitor. The reward to our customers was a fast-programmable output that could follow a rapid sequence of test settings - or Beethoven, depending on the source of the programming.

In 1975, we began building digital interfaces for our analog-programmable models to enable them to communicate on the GPIB. From that point, we developed modules with two different interfaces. For stand-alone applications, a single-address multiple instrument serial bus was developed that could fan out a single GPIB address to as many as 27 different power supplies. This serial bus is capable of long-range data transmission up to 300 meters.

Fifty-four different power supplies (both unipolar and bipolar) ranging from 100 watts to 1000 watts and from 0-6 volts to 0-150 volts all interface on this serial bus. The bipolar models can be configured as VXI-controlled electronic loads. We also manufacture a number of front ends. One is a PC card, several can take instruction from a single GPIB address, and yet another plugs into a VXI card cage to communicate with a Slot 0 controller. This mix provides our customers with a number of voltage rails with whatever host runs their system.

A typical system will consist of three, four, or even more separate power supplies, each one stimulating a different part of the device or system under test. One popular housing is a 4U rack that can accommodate up to 9 plug-in, 200-watt power supplies running off a single VXI interface.

Kepco's power supplies are external to the card cage for two reasons. Thermal concern is probably the most obvious. No matter how efficiently they are designed, power supplies are substantial dissipaters of heat. If a group of four to five 1000-watt supplies could somehow be crammed into a VXI cage, they would soon cook everything else inside! The second consideration is to place the power as closely as possible to the device under test. With our long range serial bus, the supplies can be remote from the controller. This location near their load minimizes the losses that are inherent with the resistive nature of their connection. In a well-ventilated enclosure, other parts of the system are not stressed by this approach.

Q What technologies and products are headed to the VXI market through Kepco? A Kepco uses both linear control and switch-mode control technologies. In linear (series-pass) control, the output may be incremented by the controller with high resolution, very low noise, and high speed. The newer switch-mode technology offers a higher efficiency, which also translates into smaller size and lighter weight.

Kepco's switch-mode technology also offers the user a wide-range universal AC input (85-264) VAC, enabling it to work in North America, Europe, and Asia without selectors. Our designs also incorporate PFC (Power Factor Correction) technology, which forces the AC input to conduct continuously rather than at the sine crest. This reduces distortion induced as harmonics on the power mains. This feature is driven by the European EN60555-2 directive, to which the entire power supply industry is bound.

Q Does anything differentiate Kepco from the host of other power supply companies? A Significant power supply companies number over 300 in the USA alone, a figure that increases by as many as 200 if you add Europe and Asia to the picture. Altogether, perhaps 1,000 companies worldwide identify themselves as power supply makers. Many of these are "niche" suppliers, and a great number are custom (bring me your requirements) producers that concentrate on high volume applications. Another significant group is captive to the parent equipment maker.

Relatively few companies bother with the instrument power supply business, and most of those produce low-end bench power for schools, labs, and test benches. Only a handful of players concentrate on the precision programmable power market. And Kepco is one of these.

Yes, we also make power for the telecom market, fault tolerant power for mission-critical applications, and modular power for industrial and commercial OEMs. But our focus is on the automated test market and the special requirements that distinguish such products.

Typically, our instrument-grade power supplies have very high closed-loop gain to reduce the stabilization error from source and load changes to levels that are almost beyond measure. Our power supplies are controlled digitally with 12-bit resolution (0.0244%). A typical linear unit is intrinsically stable to better than 0.001%. Recently, we have announced support for a 16-bit digital interface. The first products that will feature this new support will be our 100 to 400-watt BOP (Bipolar Operational Power supplies).

Q What do you see as Kepco's role in the future of VXI? A We would like to see the VXI market expand. As a member of the VXIplug&play Systems Alliance, Kepco will continue supporting the initiatives of that group.

Many functions that were once considered hardware are now executed as software. As our power supplies shrink in size, it becomes increasingly difficult for us to incorporate physical controls, knobs, keypads, displays, and LEDs on these miniaturized panels. Soft panels based on LabView and LabWindows offer the solution.

In summary, we anticipate a steady growth in the VXI segment of the market for programmable instrumentation power, and we plan to remain a viable player.

Paul Birman holds a BSEE from Brooklyn Polytechnic Institute, now a part of New York University. His military service was spent at the U.S. Army's Redstone arsenal during the post-Sputnik development of the Saturn rocket. He has spent 41 years in the power supply business, 37 of them with Kepco. Paul retired mid-year 1998.

For more information on Kepco's VXI bus products, visit the company website at www.kepcopower.com

Kepco's TMA VXI-27 occupies a single size C slot in a VXI card cage. Its serial bus output can drive as many as 27 individual power supplies which may be sited as far as 300 M (1000 ft.) from the controller. The power supplies include series BOP 4-quadrant models which range in power up to 400 watts.

Series MST plug-in modules provide up to 200 watts each and up to 9 modules mount in a 4U x 19" rack. Series MAT linear power supplies provide up to 1080 watts. TMA VXI-27 also drives Kepco's MBT power supplies rated at 360 watts. All of these power supplies are digitally controlled using a single address multiple instrument bus based on IEEE 1118. This enables the VXI controller card to interact fully with the power supplies, sending setting commands and receiving back the actual voltage and current readings.