Lab PSU 0-30V /10A – Part 9

One important issue is that we maintain stable out voltage during changing load. The diagram above show my current test setup using a cheap lab PSU from ZHAOXIN. To be honest this cost ca 60.- USD and the same in P&P to Norway.

The Thaoxin is set to Output 12.3V. The BasicPI Analogue Regulator is set to 5V. The variable load is a homemade resistor array build by 5W 0.47R Cement resistors ranging from 0.47R to 8×0.47R.

To assist on heat dissipation I mounted a 12V fan a few cm from the TIP3055’s and wow – this soundless fan do it’s job well. But as I increased load current I noticed that it dropped in speed. I also note that the Voltage out on the Analogue regulator vary with +/- 0.5V. But the display on the Zhaoxin still show 12.3V – so I mounted a voltmeter to check.

What I see annoy me – the Zhaoxin PSU is not reliable – as soon as I apply ca 4R load (current ca 1.6A) it drops to ca 9V. My own analogue regulator hold it’s ground better by increasing the voltage a little. If I increase further the Thaoxin continues to drop it’s voltage.

The display still show 12.3V giving no indication that the voltage out actually have dropped to 8ich V out. ZHAOXIN Lab PSU is not very reliable – firstly it drops With load and secondly it show an incorrect out voltage under load.

As for my own voltage out I also notice that I have a calibration issue – my Multimeter show that my own voltage out is far more stable than my mounted V/A meter indicate. I also have an issue that as the Input voltage drop to 7ich Voltage the regulator need ca 4V of it’s own. The encouraging part here is that I thought this Lab PSU would compete to much with cheap Asian one’s, but looking at the result I realize that my own will hold it’s ground much better under load – wow!

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