I have a schematic for an amplifier which if supplied a lower voltage will still work as a low-wattage amplifier. In the original circuit this is achieved using a 3-tap transformer:
I would like to "emulate" that 15W/7W switch using some buck conversion circuit.
The high tap giving 238VAC and the lower 173VAC. I have a transformer which gives me 238VAC, and I want to optionally "regulate" that voltage into 173VAC.
I tried searching for buck-converters but there seem to be none in this voltage category.
I thought about using a resistor network as efficiency is not a concern, but as the amplifier can't be treated as resistive that doesn't seem right.
How could I convert 238VAC to 173VAC or DC equivalent 314VDC to 229VDC?
If possible I'd prefer a cheap and simple solution over an efficient one.
Best Answer
Normal buck converters work with DC. Since the transformer just feeds a bridge rectifier all you need to do is to do the variable buck conversion after the rectifier.
If efficiency is not a concern why not just leave it in the 15W setting?
What is the purpose of doing this change? What will it do that it doesn't do now?
This circuit I found looks like it could be adapted to your needs. This is a linear DC voltage regulator. It should be incorporated after C25. It will need a low voltage supply as well to power the opamp. As designed it could go up to ~600V. If you change the value of R7 you can alter the voltage range (470K total would do about 300V). R2 could be reduced to a single 470K as well. M1 should be put on a heatsink appropriate to dissipate 10-15W.
Bartola Valves