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Using digital to control power: Q&A with iWatt
Michael McManus, DIGITIMES, Taipei [Wednesday 30 January 2013]

When it comes to digital power, iWatt claims that it is the inventor of digital power control for AC/DC. The company notes that its technology allows its customers to eliminate BOM costs by reducing components while adding reliability and enabling smaller designs. Over the past few years, the company has been able to grow its sales 50% a year and it has shipped more than one billion chips since 2007.

In the fourth quarter of 2012, Digitimes had the opportunity to speak with iWatt senior marketing VP Scott Brown about the value of digital in AC/DC power adapters, solid state lighting (SSL) and LED TV back lighting.

Q: The power control business is a very competitive industry. How have you been able to succeed?

A: We are competing with large competitors with large sales forces and large manufacturing capabilities. We win because of our core technology. And while you see a lot of great technologies in the semiconductor industry, the trick is being able to bring it to market. We have shown that we can ramp quickly by leveraging our partnerships. United Microelectronics Corporation (UMC) is our exclusive foundry partner at the moment. We also use Advanced Semiconductor Engineering (ASE) in Taiwan and Shanghai, and Unisem in Malaysia for backend services.

So far we've been focused on 5-10W power and we've been very successful there. We believe we have about strong market share in this segment. We are now moving up to the 10-40W segment and we believe we can retain our share in those markets.

Q: Can you tell us a bit about your core technology?

A: Our core IP is called PrimeAccurate. Basically, our digital technology comes into play through an accurate way of controlling the primary side of an AC-DC power supply. It is unique and patented.

If you look at an AC to DC system - AC on the input, DC on the output - historically, a controller on the secondary side of the transformer would feed back to the primary side via an opto-isolator. With our technology, we eliminate the need for the opto-isolator and the secondary side controller, as well as some other discrete components by digitally analyzing the waveform on the primary side of the transformer. In doing this we can accurately determine not only the voltage but also determine the current on the secondary side.

This combination of primary side control and accurate regulation makes us unique. There are imitators out there but they are not able to achieve our combination of primary side control and accuracy. Some companies may offer primary side controllers. Other companies offer accurate regulation by using a secondary side regulator. We are the only company that can combine those two key attributes into one product, allowing us to offer reduced cost, increased reliability and increased density.

Prime accurate technology is embedded in about 85% of the products that we ship.

Q: Can you elaborate more on your value proposition?

A: In our key areas, whether it is chargers, adapters, or solid state lighting, having an accurate voltage or an accurate current can enable smaller solutions because there is less heat sinking required if you know what your power is going to be. It can also enable faster charging in adapters and brings more reliability to our customers' products.

Our technology also takes it one step further. Any time you can take a component off the board it helps improve reliability. But in particular, eliminating the need for an opto-isolator is a significant improvement. In general, opto-isolators tend to fail sooner than most components in a system. In systems that have to survive surge voltages or systems that are plugged in all the time - networking systems in particular - the weakest link in a surge voltage situation is typically the opto-isolator.

Q: How does your primary side solution compare with competitors offering secondary side regulation? Basically, how good is your solution?

A: Well, for example, looking at voltage out in a constant voltage mode of operation, our tests show we can achieve +/-3%. Even in constant current mode of operation we can achieve +/-5%. This is as good if not better than conventional systems employing secondary side regulation. In fact, particularly for constant current we believe primary side regulation is actually better that secondary side. And if you are willing to use higher precision resistors in a system, we have customers that have achieved +/-2%.

Moreover, as I mentioned previously, we provide a strong value proposition in the networking space as well. We are designed into home gateways, networking equipment, and we have significant share in that market. In areas such as industrial, smart meters and set top boxes, we are looking to replicate that success.

Q: You have also been able to achieve success in the solid state market. How did you extend your coverage to that market?

A: Our value in the charging space is a small, low-cost solution. We noticed the SSL space has the exact set of requirements. They have an AC input, DC output and makers want something small because it has to fit inside a bulb. In the case of retrofit bulbs, you have a very small amount of space to jam everything inside. And like anywhere else, they want something that was low-cost. So the exact same attributes that made us successful in the adapter market were equally applicable in the lighting space.

We initially got into the space by taking our adapter chips and putting them inside light bulb. Having established ourselves, our digital heritage continued to pay dividends. We noticed that it is very difficult for an LED bulb to work with a conventional wall dimmer.

Dimmers weren't designed with an LED in mind; they were designed to be used with a tungsten filament. These dimmers use triac (Triode for Alternating Current) to hack out portions of that AC wave form. That works fine when you are trying to warm up a wire in a vacuum, not so well when you have an LED light.

The main difference is that LEDs react very quickly. Whatever current you inject into an LED, you basically get that same light wave in the output. On the other hand, when you heat up a traditional filament, you can't make it instantaneously cool down. It inherently gives you a nice long time constant when cooling and thus you can smooth out any glitches in the system during the transition. By contrast, LEDs do the exact opposite. But because they react so quickly, LED solutions can enable flicker to make it through into the light spectrum. This can be a real issue. It can be annoying and even if the flicker cannot be noticed with the naked eye, the IEEE has shown that flicker can be produced at a frequency that can induce epileptic fits. Using a digital approach, we are able to digitally eliminate sources of flicker.

Q: You also have an LED solution for TV backlights. Is this based on the same technology you focus on in the solid state lighting segment?

A: The technology we use for LED TV backlights is totally different from our technologies used in other areas but we still leverage our digital heritage. We found that through a digital control mechanism, we can help to balance the voltage mismatch between the LED strings that make up an LED backlight. By balancing the voltage mismatch, we are able to dissipate less power and heat in the driver units themselves, meaning you can get more drivers in a package and that means saving system costs. However, this is a whole new area for us so our share is quite small.

iWatt senior marketing VP Scott Brown

iWatt senior marketing VP Scott Brown
Photo: Michael McManus

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