A window controller for controlling one or more optically switchable windows, the window controller comprising: a processing unit configured (a) to generate a command voltage signal (V DCmnd, V ACmnd) based at least in part on a target optical state of an optically switchable window, and (b) to generate a polarity control signal (V Polar); a drive circuit operable to receive the command voltage signal (V DCmnd, V ACmnd) from the processing unit, the drive circuit comprising: a voltage regulator configured (i) to receive power at a first voltage (V Dwn2) and (ii) to increase or decrease a magnitude of the first voltage (V Dwn2) based on the command voltage signal (V DCmnd, V ACmnd), to provide first and second regulated voltage signals (V P1, V P2); and a polarity switch configured to receive the first and second regulated voltage signals (V P1, V P2), to maintain or reverse a polarity of an effective voltage (V Eff) by utilizing the polarity control signal (V Polar), which polarity of the effective voltage (V Eff) is determined using the difference between the first and second regulated voltage signals (V P1, V P2), and to output the first and second regulated voltage signals (V P1, V P2) at the polarity based on the polarity control signal (V Polar) to power the optically switchable window, wherein the first and second regulated voltage signals are output onto a power distribution line (1934, 1936) that couples the optically switchable window with a controller; a power circuit configured to provide power to the processing unit and the drive circuit; and a feedback circuit configured to supply the processing unit with one or more feedback signals (V Feed) based on one or more voltage compensation feedback signals (V Comp) based on a voltage drop detected along the power distribution line (1934, 1936), wherein the processing unit is configured to modify the command voltage signal (V DCmnd, V ACmnd) based on the one or more feedback signals (V Feed). a processing unit configured (a) to generate a command voltage signal (V DCmnd, V ACmnd) based at least in part on a target optical state of an optically switchable window, and (b) to generate a polarity control signal (V Polar); a drive circuit operable to receive the command voltage signal (V DCmnd, V ACmnd) from the processing unit, the drive circuit comprising: a voltage regulator configured (i) to receive power at a first voltage (V Dwn2) and (ii) to increase or decrease a magnitude of the first voltage (V Dwn2) based on the command voltage signal (V DCmnd, V ACmnd), to provide first and second regulated voltage signals (V P1, V P2); and a polarity switch configured to receive the first and second regulated voltage signals (V P1, V P2), to maintain or reverse a polarity of an effective voltage (V Eff) by utilizing the polarity control signal (V Polar), which polarity of the effective voltage (V Eff) is determined using the difference between the first and second regulated voltage signals (V P1, V P2), and to output the first and second regulated voltage signals (V P1, V P2) at the polarity based on the polarity control signal (V Polar) to power the optically switchable window, wherein the first and second regulated voltage signals are output onto a power distribution line (1934, 1936) that couples the optically switchable window with a controller; a voltage regulator configured (i) to receive power at a first voltage (V Dwn2) and (ii) to increase or decrease a magnitude of the first voltage (V Dwn2) based on the command voltage signal (V DCmnd, V ACmnd), to provide first and second regulated voltage signals (V P1, V P2); and a polarity switch configured to receive the first and second regulated voltage signals (V P1, V P2), to maintain or reverse a polarity of an effective voltage (V Eff) by utilizing the polarity control signal (V Polar), which polarity of the effective voltage (V Eff) is determined using the difference between the first and second regulated voltage signals (V P1, V P2), and to output the first and second regulated voltage signals (V P1, V P2) at the polarity based on the polarity control signal (V Polar) to power the optically switchable window, wherein the first and second regulated voltage signals are output onto a power distribution line (1934, 1936) that couples the optically switchable window with a controller; a power circuit configured to provide power to the processing unit and the drive circuit; and a feedback circuit configured to supply the processing unit with one or more feedback signals (V Feed) based on one or more voltage compensation feedback signals (V Comp) based on a voltage drop detected along the power distribution line (1934, 1936), wherein the processing unit is configured to modify the command voltage signal (V DCmnd, V ACmnd) based on the one or more feedback signals (V Feed).