Reducing the Cost of Satellite Power Systems

­

The whole dynamic of satellite building is changing at the moment as the industry moves to developing satellites that orbit closer to earth. Previously, most satellites operated at higher orbits which allowed greater coverage of the earth, whether that coverage was to take images, relay communications information or any other task. Often the orbit would be at, or very close to, 35,786 km, a height that would allow the satellite to be in sync with the earth’s orbit and remain over a single geographical location. At this height, and other high and medium orbits, there is a large amount of radiation that requires the components that made up the satellites to be heavily protected. It is an expensive process, which needed very expensive, large and heavy satellites with many redundant systems to try to ensure that the satellite would stay in orbit for a period of time that would allow it to repay the initial investment.

Now, primarily due to advances in communications technology, that philosophy has moved to having much smaller, lighter and cheaper satellites orbiting much closer to earth. To get around the lack of coverage offered at that low altitude, they work in constellations of hundreds, or often thousands of satellites. This has led to a huge increase in the number of satellites in orbit – from 830 in 2003 up to 9,115 in 2023, according to Statista. There are no signs of the industry slowing down and research by Goldman Sachs suggests that the number could increase to around 70,000 by the end of this decade.

Each satellite can easily communicate with other satellites in the constellation, or to ground stations, meaning that the coverage is enlarged to even the whole surface of the earth at times. As the orbits are much lower, at between 800 and 2,000km for low-earth orbit (LEO) satellites, the dangers posed by radiation are much less, and additionally, as the satellites are much cheaper and more manouevrable, the drawbacks of a failure are much less, as its coverage can be replaced easily by other satellites in the constellation.

The new strategy of satellite manufacturers has meant that the heavily radiation hardened components traditionally used for the industry are now overkill in the vast majority of cases. The hardening of these devices is usually classified using two metrics, the total ionizing dose (TID) that signals the protection afforded to the component from a constant background radiation, and the single event effect (SEE) figure is its protection from a single event.

Amit Gole, Product Marketing Manager at Microchip explained “The key difference between traditional satellites and LEO ones is that the protection required from both TID and SEE is almost halved. Lower orbiting satellites do not face the same levels of radiation that are found in deep space. TID is an important figure that signifies protection from the constant bombardment of particles, which leads to a gradual degradation of semiconductor, changing the parameters of the device over a period of time. SEE is kind of one bullet shot that could happen if something like a cosmic ray hits the circuit. If it hits, then the circuit can't function. There are different types of single events, but the danger is higher when you are in deep space, as compared to a low orbit”.

Microchip has recently launched a family of power converters that has been designed for use in LEO satellites. The new, highly efficient, 50W LE50-28 range features TID protection to 50 krad (Si) and protection from SEE events of up to 37 MeVcm²/mg, which compares to the 100 krad TID and 82 MeVcm2/mg SEE rating of the company’s existing range of satellite products.

The devices in the new family are intended to take the output of the solar panels on the satellite and convert from a 28V input taken either directly from the solar panels, or from an initial converter for 120V systems, to a range of voltages from 28V to 3.3V. These outputs then supply power to the components and subsystems in the satellite. The new devices are available in both single and triple output variants and can be paralleled and synchronized up to four times to provide 200W output power. Manufactured in a 3.055” x 2.055” X 0.55” package, the converters weigh only 120g. Although they are intended for less critical tasks than their higher orbit counterparts, they are still manufactured using the same processes to provide excellent durability, leading to a MTBF figure of 1 million hours. They are also designed to comply with Mil-Std-883,-202 and -461. Without the heavier radiation protection, the new converters are also much cheaper to buy than traditional components for satellite applications. 

One major differentiator between these new devices and those from its competitors is that Microchip’s products are not hermetically sealed. Gole explains the advantages that brings by saying, “Most designs use a hermetically sealed case, which has the major drawback that, if something goes wrong in a production process, the entire production batch has to be thrown out. From an operational perspective, that could delay the schedule of the program. In Microchip’s packaging, there are six screws that allow easy access. The design is a simple mechanical assembly. If something goes wrong, and a particular component in the module needs replaced, it can be simply done, keeping the schedule on track. The non-hermetically sealed case also ,akes it easy for us to provide derivatives. For example, if a customer wants a custom design, say 5.5V output instead of 5V, we don't need to have completely different design, we can simply change components in the package”.

https://www.microchip.com/en-us/product/le50-28-28s