Avionics and Defense Display

Since the early 1980s, the often well over 100 analog measuring instruments used in old aircraft cockpits had been increasingly replaced by modern displays, allowing the pilots to see the most important parameters at a glance. Warnings are also shown on these displays and no longer by flashing warning lights.

However, to ensure safe flight operations, these LCD or LED monitors must be quite robust to operate reliably even under extreme environmental conditions. 

As in all aircraft applications, the weight of a device also plays an important role, and developers must ensure that all components are as light as possible. For a new series of displays, a customer was looking for a standard, easy-to-implement power supply solution with the following specifications:

The complete system also had to meet the harsh environmental conditions specified in MIL-STD-810F. A combination of P-DUKE’s MCF-028008-001, an EMI filter and transient protection module, the RED60-24S12W DC/DC converter module generating a 12V bus plus further downstream DC-DC converters for other voltages was selected as it meets all of the customers’ requirements.

The MCF-028008-001 has built-in active transient protection, limiting the output voltage to 36Vmax, and an EMI filter meeting the requirements of MIL-STD-461G. In addition, the module also provides inrush current limiting, reverse polarity protection, plus several other protection circuitries.

It is a plug-and-play solution with no need for any design or qualification work, and it helped the customer to keep NRE costs as low as possible. The RED60-24S12W DC/DC converter has an input voltage range of 9 – 36V. Unlike most converters from other manufacturers, which work only down to 16V, the P-DUKE's module provides full output power even when the supply voltage drops to 12V during initial engagement (MIL-STD-1275). It can deliver up to 60W, and in this application, it is used to generate a 12V bus.

The CPU board needs the typical 12V supply voltage as onboard voltage regulator modules (VRM) generate the low supply voltage for the processor and memories. The various LCD displays need either 3.3V or 5V, and depending on the size of the display, the required power ranges from 15W to 25W.

P-DUKE’s DOH30-12T, a non-isolated DC/DC converter, is ideal for these requirements, as with just one resistor connected to the trim pin, the output voltage can be set to 5V or 3.3V.

To avoid any interference with other equipment in the aircraft, the 3.3 and 5V supply voltages for video and signal interfaces are generated by lower-power, isolated DC/DC converters from P-DUKE’s EDL03 family. This series is available with various output voltages, and if other voltages are required in the future, they can be achieved by just replacing a module without any PCB redesign. 

All modules used in the application are qualified for the harsh environmental conditions defined in MIL-STD-810F, and with a total weight of just 78g, this power supply solution represents only 1 -2 % of the total weight of a complete display unit. Since all modules come from one manufacturer, they all work together seamlessly. Together with the front-end module, which is qualified for avionics applications, the customer received a plug-and-play solution that could be integrated into the various displays with minimal design effort.

Block diagram:

Products:

MCF-028: DC front‑end EMI filter and transient protection module (5–15A); MIL‑STD‑461G and MIL‑STD‑1275E compliant. Provides surge suppression, reverse polarity protection, and hiccup‑mode overload defense for military, aerospace, and railway systems.

RED60W: 60W isolated DC‑DC converter with 3kV isolation and 4:1 wide input range (9–160V); 88–94% efficiency and adjustable output trim. Remote ON/OFF, multiple heat sink options, and comprehensive protection. EN50155/EN45545‑2 railway and industrial compliant.

DOS30/ DOH30: Programmable 3.3–15W DC‑DC converter (SMD/SIP) with adjustable output (0.8–5.5V) and 92–93% efficiency. Features current share, sequencing delay, and multi‑unit parallel capability. Ideal for industrial, telecom, and data center applications.

EDL03: 3W isolated DC‑DC module with 1600V isolation and 4:1 wide input (4.5–75V); 75–86% efficiency and 75mVp‑p ripple. Auto‑recovery short‑circuit protection and compact DIP packaging for industrial control and communications.