B0505S-1W outputs 5.5v

I am converting an existing mains powered bluetooth speaker into a 'smart network' speaker.
I plan to replace the speaker's existing electronics with an ESP32-LyraT board and then use a Google Chromecast for network connectivity.

The speaker is power by a 10v mains adapter and has a built in USB power port, so i plugged my Chromecast into the USB port and connected it's audio out to the speaker's AUX in.
The result was an awful lot of noise - a ground loop problem caused by both speaker and Chromecast being powered from the same source.

So i bought myself a B0505S-1W, connected the USB power to the B0505S input and connected my Chromecast to the B0505S output.
The Chromecast fails to boot.
A quick check shows the USB power is a steady 5.05v, and the B0505S is outputtting a steady 5.5v.
That 5.5v must be too much for the Chromecast.

I have two questions:

Why does the B0505S-1W output more than the input?

What's a simple fix?
Would a voltage divider be suitable?


Did you read this in the PDF? "In order to ensure the converter can work reliably with high efficiency, the minimum load should not less than 10% rated load when it is used. If
the needed power is indeed small, please parallel a resistor on the output side".

How much load did the device have when you measured the voltage?



No i didn't read that in any pdf, the pdf datasheet i found online was a multipage document that covered a large range of different converters and i didn't spend time reading any of it!

The voltage i reported in my original post was taken with no load on the converter.
I connected the convertor output to an ESP8266 project i had to hand and measured the convertor output and it was a steady 5.03v.
With a 'working load' the converter works perfectly.
That's my first question answered.

I also used a USB power meter to measure the current draw of my Chromecast as it booted, at idle and then as it started to cast a track from Spotify.
The Chromecast peaked at 210mA while booting.
It averaged around 160mA while idle.
And rose to around 180mA while casting.
I need to buy a convertor that can output more than 1W.
That's my second question answered.

Thanks for your help.

You are welcome. Data sheets are created for a purpose!


I received a B0505S-2W in the post this morning and managed to connect it up in reverse!
I fed my 5v source into the convertor's output...

I then corrected everything and measured the voltages.
The 5v source is in fact 5.05v.
Without a load the convertor outputs just over 6v.
I measured with 2 different loads and the output under these loads was 5.4v and 5.7v.

My Chromecast Audio refuses to boot and it's led remains unlit.
I guess it's protection circuitry is protecting it from whatever the convertor is outputting.

Have i fried the B0505S-2W by connecting 5v source to it's output pins?

The peak currents will be higher than the average measured by a multimeter. Digital devices have very bursty current draw.

I'd suggest doubling the rating of the supply and see if that works.