4 USB Port 12V to 5V car charger

DSC_9741

Official specifications: I got it from ebay

DSC_9740

No box or manual was supplied with it.



Measurements

Load%20sweep%2011.6V%20%231

The first output can deliver about 3.3A before it has trouble.

Load%20sweep%2011.6V%20%232

The output below it exactly the same, because they are in parallel.

Load%20sweep%2011.6V%20%233

The 3 output is about 3.2A, it is on the second converter.

Load%20sweep%2011.6V%20%234

And the one below it is exactly the same.

Load%20sweep%2014.6V%20%231

Increasing the voltage to maximum car voltage change the maximum output current very little.

Load%20sweep%2024.0V%20%231

With 24V input the output current was slightly lower, this may be due to heat.

Voltage%20sweep%200.5A%20%231%20input%20current
Voltage%20sweep%200.5A%20%231

With 0.5A load the output voltage can be maintained down to 7V input.

Voltage%20sweep%203.0A%20%231%20input%20current
Voltage%20sweep%203.0A%20%231

With 3A load the output voltage can be maintained down to 8V input.

No%20load%20voltage%20sweep%20%231

With no load the current consumption is depend on input voltage.

Load%20test%205.0A

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.

Load%20test%205.0Ab

But not for more than one hour. I tried doing a second run just after the first and the switcher did not like it.

Temp7122

M1: 143.1C, M2: 102.8C, M3: 126.0C, HS1: 148.8C
It is no surprise if can get into trouble at 2.5A on each output, the temperatures are way to high.

Temp7123

M1: 92.4C, HS1: 151.6C

10ohm

Noise at 0.5A output is 9mV rms and 118mVpp

5ohm

Noise at 1A output is 27mV rms and 248mVpp

2ohm

Noise at 2.5A output is 16mV rms and 154mVpp



A closer look

DSC_9747

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.

DatasheetSchmatics

Typical schematic from datasheet.

DSC_9743 DSC_9742

DSC_9745 DSC_9744


DSC_9748 DSC_9749



Conclusion

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.



Notes

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