Abstract: An inverterless uninterruptible power supply includes a battery and a clock circuit that generates a first periodic signal having a first frequency. An AC supply detection circuit generates a line control signal that is un-asserted when an AC supply is capable of supplying power above a predetermined threshold and is asserted when the AC supply is not capable of supplying power above the predetermined threshold. A control gate is responsive to the first periodic signal and to the line control signal. The control gate generates a power control signal. The power control signal is a periodic signal having the first frequency when the line control signal is asserted and is zero when the line control signal is un-asserted. A power transistor is gated by the power control signal, and periodically transfers current from the battery to the load at the first frequency.