USB Power Delivery (for Set top Boxes) - A dream so close and yet, so far away

This diagram was designed by me around 7 years ago. It’s now showing it’s age, but it was an amazing achievement by then. By now it’s just wrong.

I’ve designed this diagram  on the eve of the approval of the USB Power Delivery standard. It drew on the EU’s Common External Power Supply’s motto: one power supply to rule them all. It took us 7 whole years, and we’re not there yet, but we’re now so close.

Well, it’s also a bit weird, but I’ve worked on Set Top Boxes for most of my professional life, and my whole goal has always been the same: get rid of set top boxes. Now, it’s tremendously obvious for everyone that I’ve thus far failed. Yes, there have been some attempts at it, such as Google’s Chromecast or Amazon’s Firestick, but at the end of the day, if you want live PayTV you stuck with a STB.

However it does t mean we can’t get rid of part of the STB, and in this case, the power supply (also known as PSU).

A bit of history is in order…

Back on 2009, the EU was targeting electronics waste as vacines target viruses: unrelentingly and from all angles. One of the most obvious targets where mobile devices, and specifically the mobile’s battery chargers. From the EU’s perspective, it didn’t make any sense that each mobile phone one would need to use one specific charger, which would become useless the day the mobile phone would be thrown away. This had many daily live implications:

  • If one would need an additional charger, for instance for the office, a specific per-model charger would be needed.
  • Wanna have a quick charge at your friend’s home? though luck…
  • After having bought 2 or 3 chargers, and you buy a new phone? Buy the additional chargers.

It really didn’t make any sense, so the EU, from the top of it’s moral grounds decided to grab a standard which was only making it’s appearance, USB-BC (USB Battery Charge) and made it mandatory for all mobile devices sold within the EU single market. The effect wasn’t felt immediately, but as time passed, the results were obvious and over reaching. Today you can charge your phone everywhere, and depending on your mobile phone (meaning, if not an Apple phone), you don’t even need to bring your cable. People wanting a quick charge at the office or a friend’s home? No problem, just plug it on the laptop USB plug, or at your friend’s phone charger.

However, a clarification is in order. The common charger initiative didn’t call for the micro USB plug, but only compliance with USB-BC, which is why Apple is allowed not to use it on iPhones, but still uses a classic USB type-A plug. It does allow for an iPhone user to use the old charger on an Android device, just by switching cables, which is still far more eco friendly than replacing the whole charger, not to mention user friendly.

It was one of the first EU’s successes on their eco design regulation. Although people were still throwing away phones, they’re now keeping the charger, and reusing it.

Then 2 years latter, the USB-IF realizing the potencial of the technology, and the limitations of USB-BC released the USB-Power Delivery (USB-PD), supporting devices consuming up to 60W, at the time. The current version supports up to 100W. Not that it matters for STBs, but it made a tremendous difference on the standard’s adaption, as it made it possible, and common today for Laptops to adopt this standard for chargers.

This makes makes even a bigger difference for users, both now and on the foreseeable future. First, a laptop charger is nowhere as cheap as a smartphone charger, allowing users to cheaply to replace one, or simple to have a second.

Then, and most importantly, it allows users not to carry one. Why? Because laptops can be treated like any other USB powered device. You charge it simply by plugging it to another less portable, higher powered device. In the case, the monitor. That’s exactly the reason why some monitors offer USB-C hubs. Users may simply plug their laptops to the screen for all charging purposes.

This is the updated diagram. One single cable to rule them all.

This is case of many new generation PC monitors out there such as the Lenovo ThinkVision P24h, which ensures QHD resolution and 45W worth of charging power, simultaneously and using one single USB type-C cable.

The competition: the not-so-vanilla HDMI

Over the years, people leading the HDMI forum have been adding additional features, all making sense, not all achieving adoption, apart from the basic resolution increase, from the original 1080i to the current 8K resolutions.

The first relevant addition was CEC, or Consumer Electronics Control. This by far the most important feature built on top of HDMI, as it allows the different HDMI connected devices to communicate with each other, ir order to make thinks happen, such as turning OFF a STB when the TV is also turned OFF, or most important, setting the right inputs between the STB and the A/V system just because the STB was turned ON. This is today, as has been for the past several years, a mostly supported feature, although not all features are fully supported on all devices. Some actual use cases are fairly well supported in a real interoperable way, such as volume control, or path discovery. HDMI-CEC was already covered on this post.

Then, two more improvements were added, but with far lower adoption rates: Audio Return Channel (HDMI-ARC), and HDMI ethernet channel (HDMI-HEC).

Audio return channel implements a couple of use cases:

  • Allowing the TV as source to stream audio to the A/V system (or any device directly connected to the TV, instead of the A/V system). This also allow non-CEC compatible devices to output audio on the A/V system albeit with very limited control.
  • Dual purpose, low cost, Bluray players which also work as 5.1 A/V players , by only having one single HDMI input/output,

It works by adding a low bitrate link, carrying audio data, at up to 7Mbps on HDMI 1.4, or about 42Mbps on HDMI 2.0. Although 42Mbps may seem significant, it’s still far below the 14.4Gbps supported for video purposes. Because this feature is driven by Blu-ray manufacturers, such as Sony and Samsung, support for this is widespread on all recent models (less than 5 years).


The other significant feature, HDMI ethernet channel, also covers a very significant use case: reduce the number of cables entering the STB, by replacing the ethernet cable by an equivalent link between the device (often a STB or a Blurry Player) and the TV. Strangely enough, bandwidth is limited to fast Ethernet speeds, of 100Mbps, which seems low for 21st century standards. This feature absolutely made sense for some time, until it didn’t…

First and foremost, on the TV end, support for high bandwidth WiFi networks got very common, and specially 802.11ac, which muted the need for a cabled network solution. On the other end, it didn’t allow for any savings: with STBs and Blu-ray players maintaining the ethernet interface, and also started to embed WiFi interfaces. So, it was a good solution looking for a problem to fix.

At the end of the day, support for this is simply non-existing. Haven’t seen one single compatible devices, but then again, haven’t been actively looking for it, for the very same reasons.

Leave a Reply

Back to Top