This disclosure relates generally to optically-switchable devices, and more particularly, to systems, apparatus, and methods for controlling optically-switchable devices. In some implementations, an apparatus for controlling one or more optically-switchable devices includes a processing unit, a voltage regulator and a polarity switch. The processing unit can generate: a command voltage signal based on a target optical state of an optically-switchable device, and a polarity control signal. The voltage regulator can receive power at a first voltage and increase or decrease a magnitude of the first voltage based on the command voltage signal to provide a DC voltage signal at a regulated voltage. A polarity switch can receive the DC voltage signal at the regulated voltage to maintain or reverse a polarity of the DC voltage signal based on the polarity control signal. The polarity switch can output the DC voltage signal at the regulated voltage and at the polarity based on the polarity control signal to power the optically-switchable device. In some other implementations, the apparatus includes a processing unit, an energy storage device, and first and second voltage regulators.