What types of applications are most suited for isolated DC-DC converters?
Low power DC-DC converters offer a simple way of deriving multiple system voltages from a higher power AC-DC supply. This technique is commonly known as a “Distributed Power Architecture”, or DPA. Often that larger wattage supply is providing a 24V voltage to drive motors, pumps or other pieces of electrical equipment. Controllers, logic circuits and other electronic devices though, require small amounts of 3.3V, 5V, 12V or 15V power to operate.
In a 19” rack mount system using a DPA approach, bulk AC-DC power supplies, which can be rated to allow for future system expansion, will usually be located at the bottom to keep them cooler. A 12V, 24V or 48V system bus would then be provided to power multiple rack mounted assemblies. This also minimises a service technician’s exposure to potentially harmful high voltage wiring.
From that DC bus, TDK-Lambda’s CC-E series of 1.5W to 10W DC-DC converters can provide local voltages of 3.3V, 5V, 12, 15V, +/-12V and +/-15V. The dual output models can also be connected to generate a 24V or 30V voltage if required, even from a 5V or 12V input.
Inside each assembly, DC-DC converters can be locally placed on the circuit cards, situated close to the devices needing power. This minimises any voltage drop between the converter and the device, and reduces the possibility of any noise pick-up in the wiring, which could cause signal degradation or malfunction. If a part of the circuit is very sensitive to noise, it could be isolated from the system ground using an isolated DC-DC converter.
If an electronic device or circuit is very sensitive to, or its performance can be optimised with a particular supply voltage, DC-DC converters often have a trim function. This allows the output voltage to be adjusted from say 5V to 4.75 – 6.0V using a resistor or external voltage.
If the system has the capability of being expanded in the field with an additional plug-in card, having DC-DC converter(s) located on that card that are powered from the existing DC bus simplifies the field upgrade. The original (base) system power supply will not need to be upgraded to include additional voltages, reducing the upgrade cost.
Portable equipment will use an internal battery with a voltage most suited to power the device that requires the most energy, but again may need a number of other auxiliary voltages to function. Here DC-DC converters are powered directly from the battery and can provide a stable output voltage while the battery is being charged or discharged. Products like the CC-E series of converters are available with 5V, 12V, 24V or 48V nominal inputs. The 24V input model, for instance, can remain in regulation with a maximum deviation of only 80mV over an 18 to 36V input range.
Low power isolated DC-DC converters, in a distributed power architecture, offer a way of simplifying current and future power needs.
For more information about the CC-E series of DC-DC converters, please visit: www.emea.lambda.tdk.com/cc-e