Possible improvement ideas for the new microUSB-based external-power standard for mobile phones

Introduction

As part of the “green ethos”, there has been a rethink concerning powering portable battery-operated devices from external power supplies. One issue that was raised was running a device continuously from a battery charger when the battery was charged. Similarly, every time someone bought a new portable device or upgraded their existing portable device, they would receive an AC adaptor or battery charger as part of the delivery. If they replaced the previous device, they wouldn’t be able to use the external power supply devices that was used with the previous device on the new device unless it was made by the same manufacturer or, in some cases, part of a particular series of devices.

This has led to the idea of powering or charging personal devices via a standard “microUSB” connection that would be use also for wireline-based data transfer. This allowed for a “one-size-fits-all” connection so that the user keeps one external power solution (AC-powered charger, car charger, etc) for their device even if they upgrade the device to a newer model. This avoids the need to junk AC adaptors and car chargers during a phone upgrade, although most of these power supplies are often stored in drawers around the home.

It has also led to devices using “pronounced” visual and audible alerts to let their users know that the battery is fully charged from an external power supply. This is with a view to encourage users to disconnect the device from the external power supply once the battery is full.

External-power-supply operation mode

There are other reasons why we may keep a device plugged in to an external power supply beyond the time required for battery charging. One common reason is part of a practice that has been commonly practiced since the 1960s primarily with portable radios, portable tape recorders, pocket calculators and other electronic devices that were commonly used with disposable dry cells. This is to run the device and use its primary functions from the external power supply, thus conserving battery runtime and allowing the user to use those functions that would compromise the battery runtime, like using the device’s lighting or fast-winding tapes in a portable tape recorder. In some cases, people connect their portable devices to car adaptors that plug in to a vehicle’s cigar-lighter socket so that the device can work from the vehicle’s electrical system while they are under way in the vehicle.

If a phone or other device that is being charged is meant to signal when the battery is full, the device should also have a user-selectable option to simply run from the external power supply rather than the battery when the battery is full and “fall over” to the fully-charged battery when the external power supply is turned off or disconnected. This mode could allow a user to run the phone from the external power as a way of conserving battery runtime and would be more relevant to smartphones and phones that can work as media players, GPS navigation units or handheld games consoles like my Nokia N85 or the Apple iPhone. The message could say “Battery full, Running on external power” as an alternative to a “please disconnect external power” message. As well, the device could show an “external power” icon like a “plug icon” that indicates it is running on the external power. It can also lead to "power-source-dependent” operating modes like the display being brighter and always on when connected to external power.

There could be an extension to the new micro-USB power-supply standard to cover external battery packs that supply power to devices either from common “AA, C or D” batteries or high-capacity rechargeable battery packs. These could signal to the device that they are an external battery pack and the device works as if on its own batteries when they are connected. This would lead to regular battery-mode operation like the display lighting up on demand; and could allow for “power-only, no charging” behaviour if the internal battery is full. It can also allow for the battery-level gauge to show a battery-level reading for either the internal battery or the external battery pack or a “combined” battery-level reading for both battery packs.

Self-powered multi-port USB hubs

I have tried using some self-powered multi-port USB hubs as battery chargers for my Nokia N85 mobile phone but sometimes the phone will treat the USB hub simply as a data uplink rather than a battery charger. I have also seen similar “hit and miss” behaviour with the Apple iPhone or recent-issue Apple iPods.

What needs to happen is that these hubs need to support “battery charger” / “power supply” mode when nothing is connected to the upstream (computer) port and the only thing connected to them is their AC adaptor. They would then need to provide the full power requirement for each of the ports and behave as if they are a power supply. They could switch off power to ports that don’t have anything connected to them so as to conserve energy. The AC adaptor would also have to be rated to provide the full power to each of the ports.

This is because a 7-port self-powered USB hub can appeal to being used as a “charging bar” for multiple personal-electronics devices, thus avoiding the need to use a powerboard to power many mobile-phone chargers.

Similarly, this idea can lead to the development of integrated “power-only” USB hubs that can be built in to various objects, including furniture and vehicles.

Speaking of vehicles, I may have mentioned this before, but there needs to be a reference design for a USB 2.0 or 3.0 self-powered multi-port hub that can work in an automotive environment. This involves support for a reference 5V 2.3A DC power supply circuit that can work from either a 12V or 24V DC power supply like what is found in a vehicle. The reference design should support power regulation so it can handle a “rough” power environment such as power “sags” and “surges” that occur when the engine is started. As well, it could support the concept of “ignition-switch control” where devices could be put in to low-power mode or turned off when the driver removes the key from the ignition switch.

Conclusion

Once these factors are looked at, they can allow us to provide better use of the new standards for operating our smartphones and similar devices in an optimum manner.

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