CIO Quick-Charge-3

Purchased from the official CIO store a few months ago.

There are no issues with usage, but there is a faint buzzing sound when charging.
I contacted the manufacturer, and they stated that:
The sound is generated by electromagnetic induction,
and it is an unavoidable phenomenon due to the product's design to silence startup sounds. It does not affect safety during normal use.

↓↓↓ Below is from the official website ↓↓↓↓
Compact with a foldable plug! Convenient portable fast charger, QC3.0 compatible, USB-A 3 ports.
The first port is independent with QC3.0 and supports up to 18W. The second and third ports are equipped with SmartIC to optimize charging efficiency within 12W.

Model Number: Quick-Charge-3
JAN: 4589406022718 (Black)
Size: Approx. 2.6 x 5.4 x 4.5 cm
Weight: Approx. 80g
Port Configuration: 3 ports
USB-A x3
Input: 100-240V 50/60Hz
Output: USB-A1 6-6.5V=3A, 6.5-9V=2A, 9-12V=1.5A
USB-A2/A3 5V=2.4A (12W Max) with SmartIC
Fast Charging Standard: QC3.0
AC Plug: 90° swing