Bernhard Erdl, founder and CEO of the PULS Group, looks back at 50 years of power supply development.
The market from 1976 to 2026:
The transition from linearly regulated power supplies with 50 Hz transformers to switched-mode power supplies triggered a wave of company formations around the 1970s.
In contrast to series-regulator technology, where the requirements lay more in manufacturing, with large, heavy components, the new technology was more strongly driven by know-how. As a result, practically all companies that had traditionally manufactured their power supplies themselves transferred these tasks to specialists. I would like to recall that IBM was once the world’s largest manufacturer of power supplies, solely for the purpose of meeting the demand in its own mainframe computers.
Although switched technology was originally developed for defence and aircraft, where weight was critical, it first found widespread use in the IT sector. Its first commercial use was in 1972 in HP’s programmable desktop calculator, the HP 9100A (18 kg!). Then, in 1977, the legendary Apple II was introduced and no longer required a fan. Monitors and printers were another major field of application for switched-mode power supplies.
Companies from the USA and Asia were the dominant suppliers: Astec and Boschert for low and medium power levels, Pioneer Magnetics and LH Research for high power levels. In Europe, Gould from Great Britain, with a 5 V/20 A power supply and Unisel near Munich, with a modular concept for 40 W, were widely used.
The strong demand from the IT industry and the high proportion of manual work involved in producing a switched-mode power supply quickly led to a dominant position for Taiwanese companies: Delta Electronics, Lite-On, MeanWell, FSP and PhiHong. They were also able to take rapid advantage of the cost benefits offered by production in China. A large number of companies later emerged directly in China, but they never matched the Taiwanese suppliers. For geopolitical reasons and because of their understanding of the market, they have not achieved the same major success in Europe and the USA. The question is whether Taiwan, too, might belong to China in the foreseeable future and what would happen then.
The dominant form factors at the time included open PCBs, L- or U-shaped brackets, optionally with or without covers, enclosed housings usually with fans and large 5 x 8 x 11-inch (127 x 203 x 279 mm³) subracks. Today, 1U and 2U plug-in units for servers have been standardised. Conduction-cooled power supplies have also been seen more frequently recently.
A typically German format was the Eurocard and German manufacturers accordingly dominated this area: Vero, Schroff, Elba Electric and Haltec. Brandner achieved good success with secondary-side switched regulators as an intermediate technology. In 1978, with my pre-PULS company, Duckert & Erdl, I brought the first switched-mode power supply onto the market. With a particularly low radio-interference level, K klein, it was even approved for use in transmitter installations and thereby dispelled reservations about the new technology. The Eurocard format, however, did not gain worldwide acceptance; it was too expensive and has practically disappeared from the market.
Originally, electronic systems required a large number of voltages at different power levels. Fixed multi-output units could not satisfy many requirements. Modular power supplies were therefore developed, with TDK-Lambda leading the way; different modules could be installed in a carrier frame.
By now, however, the semiconductor industry offers many devices, together with the associated application support, which enable users to generate the required voltages themselves on the board. Since then, the trend has therefore been more towards power supplies with only one or at most two output voltages as the front end and local DC/DC converters with or without galvanic isolation.
Vicor had a very strong influence on this trend. It was nothing less than a sensation when, in the 1980s, the company used a resonant concept to increase the switching frequency, which had previously typically been 30 kHz, to 1 MHz. Vicor’s flat modules, often called ‘chocolate bars’, could be soldered directly into a PCB. However, because these were only DC/DC converters, the user had to build many things around them: EMC filters, rectifiers, electrolytic capacitors and heat sinks. Today, several suppliers offer a range of different sizes and power ratings, used mainly in the DC/DC field.
A completely new concept was to snap the power supply onto the DIN rail. The first products were launched by PULS in 1991, soon followed by Siemens with SITOP. Siemens quickly captured the entire market. From 1997 onwards, PULS focused exclusively on this form factor. Other manufacturers of automation components, such as Phoenix Contact, Weidmüller and Wago, followed. However, they did not start with products they had developed and manufactured themselves but had them produced under contract.
There is no such thing as a single unified market for power supplies; instead, it is highly fragmented. In the IT sector, fan cooling is standard, while in automation it is convection cooling. In terms of service life and product availability, the range extends from 20 years in the industrial sector to four years in the IT sector. The market also differs very clearly in its sales channels.
For this reason, the automation technology and general electronics markets are very separate, served by different suppliers and through different channels. Successful companies in the general field are rarely successful in DIN-rail power supplies and vice versa. DIN-rail power supplies now account for around 25 % of the overall industrial market.
Technology from 1976 to 2026:
Technically, half a century ago, the industry had reached a dead end with a linear regulator and a 50 Hz transformer. Since the linear regulator, as a variable resistor, can only regulate by destroying power, the input voltage for the linear regulator had to be higher than the output voltage even in the worst case. It is like nailing the accelerator pedal of a car to the floor and controlling the speed with the brake. The efficiency of a 5 V power supply was 25 %! After I had developed a linearly regulated multi-output power supply with 600 W, using every technological trick such as transformers with automatic switching of winding taps and current limiting via op-amps, I decided never to develop anything like it again and instead to rely on the new technology.
Fortunately, the semiconductor industry began to offer suitable components for this purpose. Originally developed as bipolar high-voltage transistors for line deflection in televisions, they could also be used to build efficient power supplies. For developers, however, this meant that they had to learn a great deal that was new. How do I drive such a transistor so that it switches quickly and survives? A MOSFET is easy to switch, whereas with a bipolar switch it is an art. With a sophisticated driver circuit, I was able to switch off a 1000 V bipolar transistor in 20 ns, but it was very complex.
Magnetic components were an unfamiliar subject: how do I calculate a high-frequency transformer with its surprising skin-effect and proximity-effect phenomena in the copper winding? Valvo/Philips and Unitrode, now TI, were very helpful with many application notes and training courses. The first Power Conversion Conference (today PCIM) in 1979 was a highlight.
The first MOSFETs arrived in the 1980s. They were a dream for the developer: extremely easy to drive and immune to second breakdown. However, they had high conduction losses.
It was thought that, from a physics perspective, it was not possible to achieve low on-resistance at a high blocking voltage. Then Infineon achieved the breakthrough with the superjunction transistor and broke through the supposed limits of physics.
Fundamentally, progress in power supplies is always an interplay between new components and the better concepts and topologies they enable. One example is the replacement of rectifier diodes by MOSFETs as synchronous rectifiers. Schottky diodes used to be the standard; today it is MOSFETs, whose price has fallen so far that they can be used on a broad scale.
The fall in MOSFET prices also made it possible to move from hard-switching principles to resonant-switching topologies. Although these have higher conduction losses, these can be offset by larger chips, so that the advantages of largely loss-free switching prevail. Flyback, forward and push-pull converters used to be the standard; today it is the LLC converter.
With all these advances, it was possible to increase the efficiency from the 25 % of the series regulator mentioned above to 65 % in the first switched-mode power supplies. For a long time afterwards, 75% was a good value, until efficiencies rose past 85 % and then to well over 90 % today. PULS’s top product today achieves an efficiency of 97 %.
Astonishingly, even after 50 years, tangible progress is still possible. Better components, complex simulation tools and the refinement of every detail result in better products.
Wide-bandgap materials such as SiC and GaN, chip packages that can be cooled from both sides or from the top side, low-cost microcontrollers for complex control schemes, simple current sensors, more compact multilayer ceramic capacitors, better electrolytic capacitors, optimised ferrites and ever more SMD package types are the playground on which developers can play.
I do not expect one great breakthrough; the technology is too mature for that. But progress on many levels has a clear cumulative impact.
The only major next step will be the transition from AC networks to DC networks, as advocated by the Open DC Alliance and now above all by Nvidia. This will make further fundamental improvements in efficiency, size and reliability possible.
All these topics require enormous investment in development. Only companies that have both the volume and the willingness to make that investment will be successful in future. Looking at the table with the many company formations in the 20 years between 1968 and 1988, it is striking that most companies have disappeared or been acquired. Market consolidation will continue and not many new companies will be founded.
Bernhard Erdl, founder and CEO of the PULS Group: “I have been developing and producing power supplies since 1974, writes Bernhard Erdl, founder and CEO of the PULS Group. My first electronic endeavour at school in 1968 was building a laboratory power supply and as power supplies are therefore my professional life, I have far more to tell than this article can accommodate. I therefore ask, in advance, for forgiveness if I have not given every company and every trend the attention they deserve.”
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