Enhanced Avionics

Power supply weight reduction, efficiency improvements, reliability improvements, hot-swap-ability and load sharing are the top concerns for aviation electronics (avionics) designers today. In the race to create safer, lighter, more fuel-efficient aircraft, every component must be considered, even the smallest electronic chip.

Efficiency is in the (Re)Design
Orchid Technologies Engineering & Consulting is an electronic hardware and firmware design and development company. Their primary business is to design custom electronic products for a variety of clients around the country. The company specializes in conceptualizing and developing solutions for their clients as well as redesigning previous or current projects to enable the avionics system to be as efficient, safe, and light as possible.

“A product may have been in an airplane for the last 10 or 15 years, and that airplane may still be in the air for another 10 years,” explains Paul Nickelsberg, president, Orchid Technologies. “Subsystems need to be redesigned and we’re doing that all the time, and in aviation, the name of the name of the game is making them lighter.”

One of the areas that Orchid Technologies addresses is the battery systems. For instance, a current project, a primary energy system for a 747 aircraft, weighs 200 lb at the start. It was designed about 35 years ago, but needs some updates to meet today’s standards. According to Nickelsberg, the part could probably be S as large and at least ½ as heavy as its current size and weight. But reducing the size may not be the solution they’re looking for.

“So often with situations like that, we don’t want to make it smaller, because it’s going into somewhere that it fits,” he says. “But we do want to make it lighter, and that’s always a winner. The envelope is fixed and the form fit and function is fixed, but the weight can be removed and sometimes the reliability can be improved.”

In circumstances such as this, it is often Orchid’s challenge to reduce the weight but keep the size of the part. A primary way of reducing weight is switching battery technologies and the electronics to control them. Previously, backup power supplies were lead-acid based, and housed in stainless steel or some other heavy metal. Lead-acid batteries are rather heavy, and weight could be reduced by switching to lithium-ion batteries.

Teamwork
About 10 years ago, Orchid selected Linear Technology, Corp., a manufacturer of a broad line of  high performance power controllers, as one of its primary vendors.. The two companies have continued to work together to bring efficient power supply designs to the market.

“Battery-charge cycling, power path control, ideal diode load sharing components, Field-Effect Transistor (FET) drivers – all of these components play a part in modern power system design,” states Joe Silk, area sales manager at Linear Technology. “We happily recommend Orchid Technologies to our power supply and analog component customers. Orchid has had a lot of experience using Linear Technology’s products.”

It’s not uncommon for Orchid to partner with Linear Technology to create parts that enable aerospace applications to yield more efficient results.

“As good as Linear Technology’s parts are, when you’re working day-to-day with them, it’s often the case we think of features that that they may not have thought of. If they’re trying to see how the market might respond, we can often offer some insight into that,” Nickelsberg says. “But I really think it’s a two-way street. They’re extremely helpful to us in suggesting a particularly well-suited device, maybe something we haven’t seen. And the other way around, we’re useful to them in showing them applications that they may not have thought of.”

Orchid also works with other vendors in a similar way. It is their practice to work hand-in-hand with other companies to brainstorm and create the best answers for the avionics market.

Currently, Orchid is using Linear Technology’s components in a project involving a battery controller that handles up to 12 high current lithium ion batteries. The system is responsible for turning the batteries on and off and making sure that no one batter gets overly discharged. These high-energy systems may contain as much as two 2,000W units in an application.

“At these power levels, the switching components want to be efficient, because if they’re not, they get hot,” Nickelsberg explains. “In confined spaces, as this particular case is, we would quickly see temperature rise in an inefficient design.”

Batteries must be efficient to maintain a healthy temperature, as well as to allow the battery to last longer. In order to get all of the energy out of a battery without wasting any of it, one must have power supplies that are achieving 90% efficiency or higher, according to Nickelsberg.

For the large, 2,000W application, Orchid’s customer was concerned about. They  required Orchid to keep the heat down. But the customer’s original design concept was wasting about 20W – 25W in heat.

“Though they didn’t much care that their efficiency was low, the heat would have been unacceptable because everything would have been too warm. So we went from about 25W of wasted heat energy to about 2W,” Nickelsberg explains.

To achieve this result, Orchid changed the architecture of the customer’s designs by using the base idea and improving upon it. Most of their business is custom work such as this.

Improving Reliability
It is common for avionics engineers to de-rate a component to improve the overall reliability. That is, if there is a part that is required to operate at 100V and the part needs to be highly reliable, a component that operates at 200V or 300V may be put in its stead.

“By over-specifying the part, we achieve improved reliability,” Nickelsberg says. “This is very common. In a highly reliable design, one will often sacrifice cost, weight or size to make it reliable.”

Hot-swapping is another reliability-enhancing feature, which gives the ability to install or remove a component while it is still in the “on” position. In some situations, Orchid has designed redundant power supplies, meaning that there might be two in the system, and any one can be removed without shutting the entire piece of equipment down.

“Let’s say you’re on the Space Shuttle and you’re cruising around the moon, and one of your power supplies dies – the important one. In a redundant or hot-swappable situation, you can simply remove one and replace it with a good one on the shelf, and never experience loss of service,” Nickelsberg says. “You could imagine that in critical applications, that matters.”

Lithium in Avionics
Lithium batteries have been around for several years, but improvements in the chemistries are making them safer; the chemistry together with protection circuitry is improving. Batteries exist that can operate over very wide temperature ranges and delivers high currents, making lithium batteries ideal for aviation applications. Some batteries are able to operate at -30°C to -40°C, and similarly on the high end, at 125°C.

“I’ve always thought it’s hardest on the cold side, because so many things happen that you don’t expect,” Nickelsberg muses. “When things get hot, your mind understands hot. But when things get cold, it’s surprising what breaks – it’s often not what you think it would be. New lithium batteries seem to work better in regards to these breakages.”

Through the integration of lithium batteries in their designs in conjunction with smart teamwork and brainstorming, Orchid Technologies is able to re-design and/or customize avionics systems to ensure better efficiency and reliability.

Orchid Technologies Engineering & Consulting, Inc.
Maynard, MA
orchid-tech.com

Linear Technology
Milpitas, CA
linear.com