The reason for the problems with programmable DC and programmable AC power supplies is that the "insulated amplifier" is easy to choose.

 

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According to the data collected in the field, the content is the current setting value of programmable AC power supply and programmable DC power supply. The performance does not reflect the stability of the output current. After confirming the voltage in each section, it is found that the reference voltage, which must be ensured to be stable, has changed. The culprit was the "insulated amplifier" at the interface between the customer's controller and the programmable AC and programmable DC power supplies.

At that time, I had no experience in using insulated amplifiers, but I thought there should be no problem because my predecessors used them in this way, so I used the same product as ordinary OP amplifiers. After reviewing the specifications of the insulated amplifier, it was found that the offset was larger and the temperature characteristics were worse compared to the normal OP amplifier.

At the same time, in order to reduce the number of amplifiers for programmable AC and programmable DC power supply, the amplifier is used with the gain set on the insulated amplifier. As a result, the offset gain is doubled, which is also one of the reasons for the stability degradation of programmable AC and programmable DC power supplies.

The solutions are: (1) change the insulated amplifier to a product with better stability (2) Use the OP amplifier to gain according to the gain 1 (3) put the OP amplifier for gain into the front of the insulated amplifier (insulated amplifier with high voltage by performing input and output to reduce the effect of offsets).