DC to DC converter 6-24V to 5V 3A phone car USB charger power supply Regulator

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Official specifications:

I got this converter from ebay (bestgoodbuy).



Measurements

I have tested it for usage in a car, i.e. with a car voltage supply, but I have not simulated electric noise from a car.


Load%20sweep%2014.6V

First test is with the maximum normal voltage in a car.
It stays within tolerances up to about 2A, where it has a loss of nearly 2 watt.

Load%20sweep%2011.6V

Next I do the same test with the minimum voltage you will get in a car, before the battery needs replacement.
Again it works fine up to about 2A.

Voltage%20sweep%200.5A

At 0.5A load the converter works perfectly from 6V and up with about 90% efficiency.

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

It uses up to 0.25A, that will drain a 30Ah battery in about 5 days.

Voltage%20sweep%202.0A

Increasing the current to 2A, the voltage drops to the usb lower limit and the loss increases.
Note: Some of the voltage drop is due to the usb connector and the usb cable.

Voltage%20sweep%202.0A%20input%20current

Input current is close to 1A.

Voltage%20sweep%203.0A

At 3A the converter needs a bit more input voltage before it is stable.
The loss is 3.5 watt, this is a lot of power for the circuit.

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

Input current reaches 1.5A

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It is also interesting how much power the adapter uses when not loaded. This unit here is about 17mA, that would drain a 30Ah battery in about 73 days.

2ohm

At 2 ohm load (2.5A) the noise is about 42mV rms,

10ohm

Increasing the load to 10 ohm (0.5A) increases the noise to 53mV rms.



Conclusion

This adapter delivers a good 5 volt supply, but is missing some safety. For usage in a car I would add a 0.75A polyfuse in series with it.
It does also lack a undervoltage cutout, there is nothing to prevent it from draining the car battery.



Notes

Read more about how I test USB power supplies and chargers