Custom power supply from Excelsys meets EPC Labs' demanding shipborne spec

Compared to alternative designs, the Excelsys solution for EPC reduced the required parts, improved efficiency, and saved space. EPC’s previous design had an AC/DC input module plus filter, 2 full brick DC/DC and 2 half brick DC/DC converters. Excelsys’ configurable modular design enabled consolidation into a single 1U AC input chassis with 4 output modules, with the added benefit of a 20% reduction in cost.

With power sources that can range anywhere from good to poor, shipboard environments can be challenging. The EPC application required a PSU that would tolerate a wide input range of varied quality for use in countries around the world. Excelsys offered a supply with a universal input of 85-265V that filled the bill. EPC’s immediate application was submarine based. Overall size and reliability were of critical concern, as was the quality of the DC outputs when under load. The EPC product required four different outputs to drive the various systems of the recorder. The Excelsys modular system offered the flexibility to build a supply that would deliver a clean source at 150W for the system’s sensitive 3.3-5V logic plus two, independent, high current 24V supplies for operating the system’s thermal printhead. Finally, a third 24V module was used for driving a stepper motor circuit, which is a highly inductive load. The system’s printhead is actually two separate arrays of resistive pixels that demand up to 10A of inrush current each. Average current consumption can run around 8.5A. The average resistance of each element array can be different, so the availability of fully isolated outputs with a wide trim range to balance each side was a major benefit. The superior performance and flat characteristics of the Excelsys modules enabled a reduction of the external surge capacitors from 11000uF to 1000uF with consequent space and cost savings. EPC also manufactures a line of smaller plotters with single-array printheads. Configuring the Excelsys supply for use in these systems was as simple as just removing a module from the chassis.

EPC’s thermal printheads are driven by a unique strobe sequence that produces up to 256 levels of gray per element, with loads pulsed at 100-1000 microseconds at varied duty cycles. To test the power supply, EPC ran worst-case load conditions with highest contrast ratio and under maximum print speeds. Power supply reliability is extremely important for EPC, as a failure can shut down an expensive ocean survey, requiring a trip back to port.

EPC Labs President John Curley comments, “We really like the way Excelsys modular AC/DC supplies are scalable and easily configured for future system designs. Based on the performance and flexibility of the Excelsys system, we will be able to easily plan our design cycles for future products. Our end customers will also be able to easily field upgrade and service an Excelsys modular power supply. Either EPC or our end customers can hold parts in stock for upgrades and scheduled maintenance.”

EPC Labs, Inc. has a 40 year history of manufacturing and selling shipboard Thermal Graphic Recorders and Data Acquisition Systems for use in a wide variety of custom applications including, side-scan sonar, sub-bottom profiling and spectrum analysis of ocean floors and communication surveillance. EPC’s products are used in oceanographic surveys by oil and gas companies, as well as in surveillance applications by military agencies throughout the world. System Application: Data acquisition (normally sonar) with thermal printout on 10 or 20 inch wide paper at 200 dpi (dots per inch) with 2-256 levels of gray, used primarily in shipboard operations.