Abstract: Aspects of the disclosure relate generally to uninterruptible power supply (“UPS”) units for systems requiring back up power. The UPS units include driving circuitry for controlling charging and allowing discharging of a battery. The driving circuitry includes a controller as well as a pair of switches. The MOSFETs includes a charging and a discharging MOSFET in series with the battery operating as a bidirectional switch. When the UPS unit is connected to an AC power supply, the controller regulates the current through the charging MOSFET switch based on feedback from a feedback device in order to charge the battery. If AC power is lost, the controller goes into saturation, switching the discharging MOSFET to a on condition and allowing the battery to discharge. The transitions from AC to battery power and vice versa are automatically achieved via the controller.