Another USB-C power option

Lenovo has a 170W GaN charger with PD 3.0 for about $35 US.

Not a bad alternative to have a spare.

I reckon that’s proprietary to be honest, so wouldn’t output 170W over USB-C.

Mentions PD 3.0 which is 100W max at 20V and Slim-tip which is Lenovo’s equivalent to barrel jack. Most of their gaming laptops and workstations for the last 5 years use slim-tip running 20V at high amperage.

So you’d get 100W max via USB-C, and 170W over slim-tip to a compatible Lenovo with the bundled adapter cable.

We’re looking for PD 3.1 support for the FW16.


PD 3.0 just means PD 2.0 (what is already standard) except allows the end device more granular control over what voltage the power brick outputs. Afaik no Framework product supports PD 3.0 (although all PD 3.0 power bricks also are required to support PD 2.0 which will work).

PD 3.1 is what introduces the much higher charging that the Framework Laptop 16 can take advantage of.

Without PD 3.1 it will be limited to 100w.


That Lenovo charger violates the USB specification. I would avoid that one.

Yup, and even then, PD 3.1 supports 28v, 36v, and 48v @ 5A, which equates to 140W, 180W, and 240W.

Our charger is currently the 36v @ 5A 180W standard. Hopefully we’ll start to see 240W PD 3.1 USB-C power supplies soon. The bundled cable with the 180W charger we have is already rated for 240W, so we just need the brick. :slight_smile:

Elevated Systems did bring up something I didn’t even take into account, which is the inefficency of DC to DC step-down conversion. Our laptops don’t use such high voltages, so it has to step down the voltages back to something it can use. The larger the voltage difference, the less efficient it seems. So a lot of heat generated too. So the 180W PSU after all that conversion means we’re realistically getting about 140-150W of usable power. I dunno how bad it’s going to be when 48v PSUs comes out.

Asus claims the efficiency is 90%, meaning 216w of usable power. They use that as their justification for not using it.

Framework is using the LM5143 chip to handle the conversion, however the datasheet doesn’t specify the efficiency when converting 48V 5A to 20V. The closest it specifies is that converting 48V 5A to 5V is 85% efficient, so presumably converting to 20V would be more efficient.

Doesn’t have to be the case, there are ways of doing highly efficient converters with large voltage ratios. But typically these methods would only be used at the high power end of things.

No, if you check the power supply ratings I think you will find that the rated power is power out of the USB-C connector. Also a mains power supply is probably one of the most efficient forms of SMPS as it uses a transformer to do most of the voltage ratio conversion. At max power output a well designed power supply will be operating at around 95% efficient. This is also a feature of the so-called GaN power supplies, the GaN technology FETs used in the power switching stage are more efficient than straight silicon FETs used previously, thereby gaining added efficiency.

So at the end of that, a 180W power supply/charger will be dissipating 6-7W (I havent worked out the exact figure) and I would expect a very similar figure for a 240W unit once they appear.

The other thing to consider is that this ‘inefficiency’ is external to the laptop, so doesn’t affect how long it will run off battery, only how long it will take to charge the battery, and that is limited by the 1C charge rate for the battery anyway.

@Techie_Zeddie is referring to the usable power after the laptop internally converts the 36V from the charger to the 20V that the laptop operates at internally.

The rated power out of the USB-C connector is before that conversion occurs.

Efficiency of conversion at that stage is affected by a lot more than just the chip used. Frequency of switching, inductor core used, type of wire used for the inductor, does it do synchronous rectification, and finally the PCB layout will all have an effect on the conversion efficiency. But when charging the battery that is the least worrying efficiency point, you have to pick your battles and sort out the ones that have a real effect on the run time of the laptop.

I don’t believe charging the battery is the aspect that anyone has complained about. People are concerned about how when operating at full power the 180W brick is unable to keep up with the load and the battery drains (at a rate of up to ~20W depending on the load).

OK, but that is not a question of efficiency in the power supply. That is just a limitation of the total power the supply is capable of. If the laptop is using more than that power then it is going to draw down the battery as well. This is just the laws of physics, to slightly misquote Startrek.

Essentially FW have acknowledged that this can happen, and so have allowed for a 240W charger, even though the highest power they can actually provide currently is 180W. The problem is that the parts to make a 240W USB-C PD 3.1 charger are not currently available, AIUI. But for most people 180W will be plenty, I certainly don’t expect to run into any problem with running the laptop that hard that the power supply cannot keep up with the power consumption.