Current regulation dynamics of Atten APS3005S

This article documents a simple test to ascertain whether the current regulation dynamics of are good enough to use for testing strings of LEDs as found in much modern lighting


The APS3005S is a linear bench top power supply 0-30VDC at 0-5A with adjustable voltage and current regulation… so called constant voltage and constant current modes.

A pair of 900mm long small gauge (0.5mm^2) hook up leads were used to apply a short circuit to the power supply, and current was set to 0.1A. The resistance and inductance of these leads will to some extent limit the peak current.

The short circuit was removed and the power supply set to 30V out.

The short was reapplied and the current captured with a current probe. The current probe calibration is 1mV/10mA.

Above, the peak current is 6680*0.1=66.8A, that is 668 times the set value.

Adjusting the open circuit voltage to 5V, the test was rerun.

Above, the peak current is 2040*0.01=20.4A, that is 204 times the set value.

There are signs that this power supply has a substantial capacitor across its output terminals, and that it can supply a substantial current spike independently of the constant current setting.


The constant current mode of operation has a significant delay in regulating current to the set value. The transient peak may be very much larger than the set value and I^2*t may be sufficient to destroy medium power (eg 0.5W 5730) LEDs as used in much LED lighting.

The power supply would be safer to use for this purpose with an external current limit resistor that does effectively prevent such a spike.

A better alternative may be a tester designed for testing such LED strings.