13-01-2016 | | By Rob Hoeben
The market for RF power transistors has been dominated by mobile communications infrastructure applications for many years but advancement in LDMOS-based transistors and packaging technologies are helping drive innovation in a number of markets.
One of these markets, and one that we feel is a big opportunity, is cooking appliances, and specifically those replacing the magnetron. First commercialised in 1947, the microwave oven has relied on the magnetron as its energy source. Now a very mature product, little innovation has taken place to improve the cooking and heating experience for users. Consumers have learnt to tolerate the hot and cold spots that most microwave ovens create in food but the pressure is now building for manufacturers to provide a faster, more uniform cooking experience.
Appliance manufacturers are trying to remove magnetron elements from their ovens and replace them with a solid-state power source. There are several reasons for this, size being a major factor but also this approach yields more control over output power, frequency and phase, all of which can significantly improve the distribution of heat inside the oven. In fact, the move to solid-state cooking is as dramatic as the move from analogue to digital television.
And using another television analogy, we believe that the technology tipping point towards solid-state cooking adoption has been reached in much the same way as television manufacturers went from the CRT to flat LCD/LED displays.
The move to solid-state cooking however is not just about using new component technology.
At Ampleon we embrace the need for a new ecosystem to drive innovation across the whole white goods value chain. This premise is behind us becoming a founding member of the RF Energy Alliance in 2014, something that we continue to be actively involved in. We are working with major OEMs to make sure we get the RF power technology right through to working with other key suppliers such as design houses, cable makers and other module manufacturers. For engineers the challenge will be learning a new set of skills on top of what they know about using magnetrons.
Naturally, it is also not only about understanding the use of RF energy for cooking applications, but that of defrosting and baking too.
Another application that we believe has a lot of potential is plasma lighting. The specific growth segments are those of high lumen lighting, typically those lights you find in sports stadiums and airports where they are mounted on high masts, and that of lighting used for horticultural growing applications such as used in greenhouses.
These applications, and several others, all require a full spectrum light source, something that LED luminaires cannot cater for either in terms of light output (lumens) or in spectrum. Sodium lamps have typically been used for horticultural applications but with their natural daylight spectrum availability, plasma lights can be a complete replacement for direct sunlight.
The reliability of plasma lamps, due mostly to the lack of lighting elements prone to mechanical stress, coupled with their high output make them an ideal choice for high mast applications. It is early days but we already have a number of trials running with leading universities involved in horticulture research.
The third and final application of note is plasma ignition technology used as a replacement for automotive engine spark plugs. This is still very much in its infancy but it is one of those that could rapidly gain momentum. With plasma you achieve a much better mixture between the air and fuel resulting in a more efficient ignition that also results in less toxic gases. This approach is forecast to yield fuel economy improvements in the order of 5%. Such savings are viewed as significant in automotive terms.
From the technology perspective it has to be said that LDMOS has been a successful process technology for RF power, and one that we continue to invest in. Creating modular, pallet-based, integrated applications such as a 50-ohm in/50 ohm out amplifier will help white goods manufacturers become comfortable incorporating RF energy into their designs.
To that end we look to identify partners to work with us so that our mutual customers don’t have to concern themselves with technical topics such as power design, matching and ignition requirements. In particular, one key challenge in the use of RF energy for cooking, is the load – the food being cooked – is badly defined and changes during cooking requires an extremely robust amplifier. Hand in hand with application robustness is power efficiency. Living in an era where we have all become conscious of the need for energy efficiency, the need to heat and cook food in the most power and time efficient manner is a key consideration.