History of the transformer

From the late 1800s, when theatres wanted a method of dimming their new lighting systems, to the mid 1900s when people wanted to be able to control the speed of their model train sets, right through to modern day telecommunication applications, people have needed a means of controlling voltage from a standard mains supply. These systems have come a long way since the manual operated systems of the 1800s, but the basic concept of the transformer has always been integral to the development of electrical and electronic sub-systems.

The transistor obviously provided great advantages to the world of electronics as we know it today, but it was the invention of the MosFet that really enabled the transformer to move on in the 1980s.

Not only do transformers provide a means for output voltage control, they are often also required to bestow current limiting features within a system, for safety reasons. The size of these transformer units is inversely proportional to the switching frequency at which they operate: the higher the frequency; the smaller the transformer. In addition, smaller transformers are able to provide higher efficiencies.

Historically, the capabilities and size of these units were limited by the frequency that the switching transistors were able to operate at, 20kHZ being the best one could expect. However, MosFets smashed this barrier apart, offering switching frequencies in excess of 250kHZ. Thus the limiting step of low switching frequencies had been removed from transformer design. This, in turn, was now replaced by the next limiting step: namely the physical design of the traditional ‘wire-wound’ transformer itself.

It is Planar transformers that overcome this new limiting step, resolving many of the problems of traditional wire-wound transformers. Not only do planar transformers provide significant reductions in the size and weight of your transformer design, but they also offer significantly improved efficiencies and much simpler manufacturing methods.

The name planar implies that the geometry of these transformers is more of a two-dimensional component, rather than the traditional three-dimensional wire-wound equivalents. Planar technology comprises two major design features that distinguish it from the old-fashioned ‘wire-wound’ transformers:

	The windings are replaced by ‘flat’ copper foil lead frames, and can even be embedded into a printed circuit board
	These flat windings are then mounted between thin, very lightweight, ferrite cores

Further to the obvious size and weight advantages, planar transformers also provide performance benefits through being electrically closer to an ideal component than their wire-wound counterparts. All practical magnetic components introduce detrimental effects into the circuit in which they operate, which an ‘ideal’ component would not. Planar components, being closer to an ‘ideal’ component than their wire-wound counterparts, remove the limiting factors in the performance of such circuits. They can often also save on additional components that may otherwise be required to overcome such problems.

Furthermore, unlike other planar transformer designs in the marketplace, Himag Solutions has rejected the need for bobbins. It has been shown that the use of bobbins result in poor thermal paths from the windings, this has the effect of increasing the operating temperature by some 10^oC. Himag Solutions has developed a new method of insulation to eliminate the need for these bobbins, and hence avoid the negative effects that they bring.