/diy/ - Do It Yourself

Fun trick of the day: digitally controlling any four-terminal adjustable voltage regulator by current injection.
MCP4725 is a rail-to-rail voltage DAC and MCP6001 is a rail-to-rail CMOS op amp, both selected for size and low cost. Iout connects to the feedback node of the regulator along with the usual resistive voltage divider.
The upper right portion of the schematic is a voltage controlled current source referenced to Vcc. The gave is driven to yield Iout = (Vcc - Vdac) / R1, or 50µA/V. Iout replaces some part of the current flowing through R4. The output voltage is therefore Vfb + ((Vfb / R5) - Iout)(R4). With the 100µA Ifb in this example and the Vfb of 1.25V, the input has (3.3V - 1.25V - Vds(on)) ~= 2V of useful width, and so only the uppermost 2/3.3V = 2482 codes are usable, yielding an output range of 1.25-12.5V and an output resolution of 4mV.
Three-terminal regulators might be usable with this scheme as well, if the current source is inverted to the lower rail and bias current is accounted for.

>>1288538
If nothing else, magnetic regulation seems to be a good way to keep the regulator robust against strong electric fields, lightning strikes, and other hostile events, and to prevent destruction of the attached equipment.