Yes, I do also remember this time. In some analog music synthesizers developers spent a lot of efforts to achieve proper tracking of the bipolar supply voltages.


Yes, sounds simple, but becomes sophisticated, when the power supply shall provide the combination of

1. 0V output voltage facility,
2. and high output voltages
3. and high load currents
4. and adjustment of current limiting
5. and displaying the settings via galvanometers

It points out very quickly then, that OPamps must be used, which can handle very high supply voltages. It also points out, that the use of these simple monolithic 3pin regulators becomes difficult and will create more problems than solving any.


In the following I want to recommend a voltage controlled design, which supports the displaying of the settings via galvanometers. The idea is to use two identical PSUs, connect them as a biploar voltage source and feed them by identical control voltages, where one of them is galvanically isolated. The control voltages for the output voltage and current limiting are fabricated by the help of 10 turn pots. So, you have the feeling of big knobs. Everything is analog. The settings of output voltage and current limiting, the actual fabricated output voltages and the actual flowing load currents can be visualized by galvanometers.

In the following only one PSU is shown. It's a very simple and widely used scheme and can be found in an application of elektor, for instance. LT1491 must not be exchanged by LM324, because only the LT1491 can withstand supply voltages of up to 44V!

The lower section shows the galvanic isolation of control voltages. Instead of HCNR201 you can also use IL300F. AN additional +15V supply must be fabricated to supply the TLC277. A simple 78L05 can be used for the 5V reference voltage at the 10 turn pots. Of course, you can also use a highly stable reference voltage source.







Kai