I have a +5V/+12V dual output power supply. They share a common ground. When no load is connected to 5V, both outputs read 5V/12V by multimeter. As soon as I connect a load (LCD) to 5V line, the multimeter still reads 5V fine, but suddenly starts reading 14V instead of 12V on the other output. The voltage also visibly fluctuates between 14.1V ~ 14.5V. The 5V line does not fluctuate at all. The LCD connected to 5V probably draws less than 300mA at best, which is way below the 3A maximum given from the specification.
Is this behavior normal? Why does the 12V power supply suddenly jump to 14V?
Best Answer
It's because you are ignoring the datasheet and not attaching a minimum load to the outputs.