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With the large number of companies now making Gallium Nitride (GaN) based power supplies like SlimQ for USBC PD style power supplies, decided to try one for my Rock Pi X sbc. The switching frequency is usually 50% higher than Silicon Power MOSFET devices. The SlimQ SMPS is extremely quiet running the sbc. The PD style power supplies are auto-voltage, so the device tells the SMPS what voltage it wants, 5v, 9v, 12v or 18v. Small ones are typically 45 watt capable and the USBC cables can be rated up to 100 watts.

Since companies are now making GaN based Class D amps that I find to sound very good and they are simpler in design due to the higher switching frequencies, and the devices are getting less expensive, I am switching over to using them with my audio devices that need a DC power supply.

Interesting times for SMPS power supplies coming.

I just ordered a 19V-90W MeanWell Hospital grade (low leakage) SMPS adapter for the NUC7i5BNK running Roon ROCK a couple days ago to replace the stock power 65W power supply. So just looked at CUI computer GaN SMPS adapters on Digikey, smallest at around 200W, hefty price (~$200). Something to keep an eye on though as more are built and the price gets more competitive. I have a pair of Pass ACAs I built that uses 120W MeanWell SMPS adapters, that might be a good place to try out a couple of GaN adapters in the future if they are lower noise.

Anyway, very interesting. It would be nice not to have to build power supplies. The GaN adapters might work pretty well for GM70 filament supplies.

David

They have a campaign going now for a SlimQ 240watt GaN SMPS supply. This one has a coaxial DC connector for laptops along with USB ports. Probably 12-19VDC. It is $89, so they are getting lower in price.

Rich,

How does GaN based switching PS compare to LPS for audio usage?

Shashi

To me lower noise, lower impedance and less sag due to the higher switching frequency, in this case about 750KHz, 50% higher than silicon power MOSFET's. Much less heat generated as the supply is 94% efficient. And power factor corrected to keep noise low. Not happening in any LPS design.

I'm building a post power supply linear filter for use with the switcher on my NUC. It uses the same philosophy I use in the power supplies for my preamp. There is some input filtration, then a large choke and finally stepped output filtration. I'll be taking scope traces of the power going into the NUC directly from the power supply and then after the filter is in place. IN the meantime, I'm including the schematic. David Berning suggested I use a soft start because he found some of the switchers look at a large capacitive load as a short and will not start. It consists of a p channel enhancement Mosfet with an RC circuit on the gate to provide the soft turn on of the Mosfet. There is also a 0.5 ohm resister in series with one of the caps to add some damping. If it works, it would essentially be a universal filter that could be used with any PS, whether a switcher or linear. Note that the choke is rated at 10 ADC and has a DCR of less than .05 ohms so assuming substantial wire in the rest of the circuit, voltage drop should be negligible.

Tom

I am thinking of trying the SMPS into a bank of Supercaps. Just have a series resistor or light bulb with a parallel switch between the SMPS and Supercap. Have the switch open to charge the cap and when charged turn the switch on. Load problem for startup solved and if HF noise is still present use the same parallel monolithic cap array. Easy to find ones up to about 16VDC and some up to 20VDC if you series more. At 500F each, with six in series still 83F of capacitance in series.

I always understood that SMPS do not like see alot of capacitance. It acts as a dead short.

Only until the caps are charged. That is why I have the Mosfet soft start. BTW. the drain to source resistance of the Mosfet when on is specified as a maximum of 0.02 ohms so typical is probably half that. It is rated at 75 amps and I got a pack of 10 on amazon for $9 with free shipping.

https://www.amazon.com/BOJACK-IRF4905-T ... s9dHJ1ZQ==

Tom

The switch and resistor will work but with the low on resistance of the Mosfet it is probably in the range of the switch and it is completely automatic with no switch bounce. Even if you had a power dropout and the caps discharged, when the power comes back on the soft start will work.