At first glance circuit layout appears quite simple:
FETs on the primary side chop the DC voltage on the input with 100 kHz, plus a small toroidal transformer generates the required voltage and provides isolation. The output voltage is subsequently rectified and smoothed.
Then there's the broad availability of design tools to make things appear relatively easy with a reference design, schematics, a PCB layout, application notes and a bill of materials (BOM).
But like many seemingly attractive solutions, the notion of a design-it-yourself DC/DC converter implemented from basic theory works better on paper than in the real world.
With switching transistors, capacitors, a transformer, rectifier and filter we are in an analog world, where things cannot be viewed as clearly as black or white. These switching transistors, charging capacitors, transformers, inductors and so forth also need to be carefully positioned with regard to one another. The length of PCB tracks, their distance to other tracks, to mass and other components, generates parasitic capacitances and inductances, which cannot be identified in circuit diagrams.
Even if the reference design includes a PCB layout, you have to be very careful if you make any changes to the layout or BOM; an apparently trivial change can adversely affect overall performance.
The transformer can prove quite problematic as well. Its performance is determined primarily by the quality of the ferrite in the core, and its functionality depends on where on the saturation curve the ferrite material operates (as well as its behavior with regard to changing temperatures and frequencies). If operated too close to saturation, it heats up and its magnetic behavior deteriorates. All of this affects efficiency and EMV-compatibility, often requiring a redesign. You also have to consider multiple wire types and gauges, insulation and cores.
So even though the basic layout of a DC/DC converter appears to be quite simple, manufacturers such as RECOM invest 80% of their development time in design optimization and reliability. The 80% figure does not even take into consideration the additional time needed to eliminate noise and meet other customer requirements. And keep in mind a last-minute change in specifications could send you right back to the drawing board.
Plainly stated, it is much easier to buy a proven, reliable module. Why choose modules at all? The concept of distributed power supply systems—the combination of a central switching power supply and localized DC/DC converters—opens the door for efficient, modular design structures. If more power or a different voltage is required to drive the circuit, only the DC/DC converter on the same PCB is affected and not the central power unit itself. Modular systems can be configured more easily, because each module is supplied with a single voltage and the rest is handled "on board" by DC/DC converters. Other motivating factors for using power modules instead of traditional discrete POL designs include benefits with regard to time-to-market, size constraints (modular converters may only need half the space taken up by a discrete assembly), reliability and not having to depend on less-than-certain in-house design capabilities.
Other elements can be addressed satisfactorily by taking the power module route: (1) it saves time, relieving pressure on engineering teams facing time constraints that are reaching an all-time high (designs need to reach market quicker and have shorter redesign windows); (2) it frees up human technical resources, which are also becoming scarce; as (3) analog competency is becoming less common in the face of digital design proficiency; and (4) it allows for the fact that even a perfect design effort can run into problems when tested (certifications are required to achieve global market acceptance) and that can take weeks to resolve.
So it should come as no surprise that the popularity of the modular approach is growing, especially given advances being made in such key design factors as isolation, temperature and efficiency.
Isolation. One of the main features of the majority of RECOM DC/DC converters is their high galvanic isolation capability.
DC/DC converters are typically galvanically isolated between the input and outputs. This galvanic isolation has different construction and voltages. This allows several variations on circuit topography by using a single DC/DC converter. The simplest (functional) isolation can withstand 1,000VDC for one second. Although 1,000VDC sounds impressive, sometimes it is still not sufficient. Medical and IGBT gate drivers demand higher isolation voltage. RECOM's High Isolation converters offer up to 10 times this isolation voltage in compact packages.
For example, in the medical field electrical equipment used on patients must conform to the medical safety standard IEC 60601-1. Often DC/DC converters are used to provide the required safety isolation between the patient and the electrical equipment. Up to now it has been extremely difficult to find compact DC/DC converters with the large air and creepage distances required to meet the definition for reinforced isolation. However RECOM has achieved this with an innovative design and can offer reinforced isolated converters in compact packages with up to 10kVDC isolation.
An industrial temperature range. RECOM's ICE (Innovation in Converter Excellence) technology uses a combination of techniques to minimize internal heat dissipation and maximize the heat transfer to the ambient surroundings. ICE technology converters use high-temperature-grade components to permit a case temperature of +120° C maximum. This allows operation at up to +85° C ambient without the need for fans to blow air over the converter.
With a wide operating temperature range of -40° C to +85° C and a wide input range, products such as the R-78E series are flexible enough to handle everything from battery-operated systems, controls and sensors, positioning systems and robotics, to medical-grade applications, cooling systems and fans, telecommunications, and highly sensitive measurement equipment.
Efficiency. Since the groundbreaking development of a drop-in pin-compatible switching regulator replacement of LM78 linear regulator, module power supplies have become more efficient and more compact than ever. Published data demonstrates this level of efficiency.
Converters in the one-watt range, such as RECOM's popular R1S, reach close to 85% under full load; a 10W converter might even touch 90%. Manufacturers optimize their design such that similar optimized values apply also to the median load range, a feat unlikely to be achieved easily with a discrete solution.
Ask yourself these questions: Will your in-house design be as efficient as an off-the-shelf model? Will the thermal characteristics be as well understood and predictable? Is your knowledge of ferrite cores and EMC filters for the design of DC/DC converters up to the task?
Looking at efficiency in the wider context of power density and mounting space, modular converters feature a much higher packing density than is normally realized on a PCB, thus requiring less than half the space of discrete solutions, an important factor as real estate is not available in abundance on a circuit board.
At this point you might be asking yourself, "But what about the cost? I don't want my purchasing manager to kill me."
Worry not. Total Cost of Ownership means more than a simple cost comparison between the bought-in module and the BOM cost of the discrete design. And thanks to mass production, the prices of converter modules have come down over the past few years so that cost-wise, the internally designed converter is probably not a viable option today, even for large-volume products.
Using modules also holds down inventory costs (different supply amounts per part, different lead times and different vendor sources) plus the production time to lay out all these parts, provide board space for all the components and so forth. Other direct costs include the placement/inspection cost of, perhaps, ten components versus one and the purchasing overhead for these components from multiple manufacturers.
What's more, we have not yet taken into account the unavoidable costs for development and testing. In particular there are EMC tests, as the units must do more than deliver power. They have to meet increasingly stringent safety regulations, electromagnetic/radio-frequency interference (EMI/RFI) standards, efficiency mandates and other objectives. In some specialty applications, such as medical instruments, they also have to keep leakage below a certain threshold and ensure that component failures will not cause life-threatening conditions.
To ensure that its product meets the most stringent international standards, RECOM has its own laboratories where they not only conduct testing but also provide ongoing education. This is coupled with the company's rigorous engineering and research and development department that is continually churning out innovative concepts.
Taken together, what RECOM has to offer is plenty. When the company started to develop its first DC/DC converters more than 25 years ago, nobody could have imagined their widespread use in electronics today. As one of the pioneers in this market, RECOM offers customers what is probably the largest selection of converters on the market, including DC/DC and AC/DC converters in all output powers up to 150 watts plus a broad range of switching regulators and LED drivers. Whether regulated or unregulated, isolated to 10kVDC or laid out for extremely high ambient temperatures of +100° C, RECOM converters offer a suitable option for every application. The selection of size or function is extremely wide, so the company is well positioned to assist you in this process.
Opting for ready-made DC/DC converters from RECOM yields valuable benefits, such as shorter development times, freeing up internal manpower resources and avoiding the risk of failing the EMC tests or other certification procedures
Indeed, as the cost/performance ratio of the DC/DC module becomes more attractive, it is safe to predict that in a few years purchasing converter modules from specialist suppliers will be as common as it is now for operational amplifiers and other logic components. Do-it-yourself will just no longer be viable!
RECOM's giant Austria-based headquarters includes a state-of-the-art EMC lab which features advanced equipment that allows specialized engineers to perform critical tests that play a major role in certifying new electronics products. Learn more about the company's lab here.
Energy-saving modular power supplies are trending, so why should you be using RECOM's modular parts instead of discrete solutions? CEO Karsten Bierstells explains why in this video.
The IoT Does Not Spell Doom for Analog Electronics
It is hard to overstate the current hype surrounding the Internet of Things (IoT). More than a billion intelligent, connected devices already comprise today's IoT, and predictions are that tens of billions of connected objects will appear in the next five to 10 years. According to the market research firm Gartner, we are at the "peak of inflated expectations" when it comes to IoT. Last year the firm placed IoT right at the top of its 2015 Hype Cycle for Emerging Technologies report, featuring technologies that are the focus of attention because of particularly high levels of interest, and those that Gartner believes have the potential "for significant impact."
Because everything related to IoT will be dominated by digitally interconnected devices with local and group intelligence, Steve Roberts, Technical Director of RECOM Engineering GmbH & Co., wonders aloud whether the future will be exclusively binary. He asks: "Will traditionally analog functions be successively replaced by its digital equivalent, with all sensors transmitting their information directly as digital data? Will analog signals be filtered by DSPs, and will "dumb" analog power supplies be exchanged for 'smart' digital power supplies that can intelligently adapt themselves to the load conditions?"
The answer, according to Roberts, seems to be a definitive "no." He further suggests that analog is far from on the way out and that the future of analog is bright and promising within the IoT.
Here is why: Roberts begins by noting that powering all of these devices will require either a single-cell battery or energy scavenging from thermal gradients, vibration and solar energy, or by tapping into the electro-smog of all the other RF networks. All of these energy sources generate either very low or very variable voltages, so, he argues, there will still be a need for boost converters or regulators with high efficiency at very low loads. Add this to the fact that most real-world things consist of signals in the analog domain—even if you want to process the signal in the digital domain, you need analog front-end filters, amplifiers and ADCs. As a result, Roberts concludes, as the IoT gathers momentum, the requirement for very low-power analog circuits will actually increase.
Industry statistics seem to bear this out. Microprocessors with on-board operational amplifiers, pulse-width modulation (PWM) generators and mixed-signal electronics are actually experiencing considerable growth, even as the IoT takes hold, and contrary to what many IoT pundits had expected.