Hello. I am new to Electronics and need some advice. One of my school projects demands that I rectify and transform 120vac to 90vdc. It is very important that the voltage remain constant and only the current be variable. Any ideas?

 

1)Use a transformer to reduce the voltage then use a rectifier to rectify it.
2)Post school assignments in the Homework Forum.

 

Generally that is known as a DC constant voltage power supply, or just a power supply. 90 volts is well above what is typically used but not excessively so.

When I just Googled "90 volt power supply schematic" I did get several relevant hits. You might also want to try some of the semiconductor manufacturers. I know National Semiconductor ([ulr=www.national.com]www.national.com[/url) (now owned by TI) has an area where you can enter your specs and they will supply a complete design.

And welcome to the forums!