4 USB Port 12V to 5V car charger
I got it from ebay
- Name: USB Step-down Power Supply
- Material: A5268 chip and copper
- Dimensions:37 * 47 * 18mm
- Current: 5 A maximum
- DC Input: 9-40V
No box or manual was supplied with it.
- Power consumption when idle is 34mA from 12V and 46mA from 24V
- All USB outputs is coded as Apple 2.4A
- Two and two USB outputs are in parallel.
- There is a red led on the circuit board.
- Weight: 31.2g
- Size: 47.3 x 40.1 x 19.2mm
The first output can deliver about 3.3A before it has trouble.
The output below it exactly the same, because they are in parallel.
The 3 output is about 3.2A, it is on the second converter.
And the one below it is exactly the same.
Increasing the voltage to maximum car voltage change the maximum output current very little.
With 24V input the output current was slightly lower, this may be due to heat.
With 0.5A load the output voltage can be maintained down to 7V input.
With 3A load the output voltage can be maintained down to 8V input.
With no load the current consumption is depend on input voltage.
The charger could handle 5A (2.5A on each switcher) for one hour.
The temperature photos below are taken between 30 minutes and 60 minutes into the one hour test.
But not for more than one hour. I tried doing a second run just after the first and the switcher did not like it.
M1: 143.1°C, M2: 102.8°C, M3: 126.0°C, HS1: 148.8°C
It is no surprise if can get into trouble at 2.5A on each output, the temperatures are way to high.
M1: 92.4°C, HS1: 151.6°C
Noise at 0.5A output is 9mV rms and 118mVpp
Noise at 1A output is 27mV rms and 248mVpp
Noise at 2.5A output is 16mV rms and 154mVpp
A closer look
The circuit has a input diode for polarity protection, but it can get very hot when running at full power. Each switcher also has a large diode, I do not know why, because the switcher (A5268) is synchronous and do not need it.
Typical schematic from datasheet.
The charger works, but it gets way to hot at high currents and the high currents are not very high with the number of outputs it has. Only using the top top outputs will keep the load acceptable.
With two USB outputs it would have been fine, but four outputs gives a couple of problems.
The charger was supplied by a reader for review.
Read more about how I test USB power supplies/charger
Compare car chargers and other DC supplied chargers