Power Supply Specifications; Electrical Design Aspects - Hengstler eXtendo X-56 Operating Manual

eXtendo® Thermal Printer Family

5.7. Power Supply Specifications

Selection of a power supply for thermal printers depends upon the printer's application, what
percentage of the printout is black, frequency with which printouts are generated, and more. In
particular, thermal printers draw high currents for very short time periods. The most important
issue is not peak current, but the length of time that the power supply is able to deliver
instantaneous current over its rated maximum, and for how long the print job prints high black
percentages, thereby drawing high current. It is important that the power supply's over-current
system does not shut down the power supply when these brief, high current surges occur.
With that said, we recommend the following power supply specifications for most 24 VDC
applications. Please see the "Technical Specifications" section near the end of this document for
full details on the various voltages available.
DC Output Voltage: 24 volts ± 5%
DC Output Current: 4 amperes (=100 Watts nominal)
Hold Up Time: 20 ms minimum
Current Limitations: 16 amperes minimum

5.8. Electrical Design Aspects

An important aspect of the electrical design is about grounding. The high currents during printing
require a solid grounding concept. Typically, the power supply for the printer and for the computer
are separate units with individual grounding. Therefore, the more important it is to keep both
grounding levels closely together.

It is recommended to locate common groundings as close to the printer power connection as
possible rather than at the power supply location. High currents can generate high voltage shifts
over long supply wires. Such high voltage shifts of up to several Volts may cause high compensation
currents that search way through the communication cable (USB, RS232) from the printer to the
computer leading to distortions in communication or even damage of components.
Part No. D-684-124 Mod. No. 4 270919 HW1 page 22 of 33