This disclosure includes novel ways of implementing a power supply that powers a load. More specifically, a power supply includes a bidirectional power converter and a controller. The controller monitors a magnitude of an input voltage supplied from an input voltage source to a load. Based on a magnitude of the input voltage, the controller switches between a first mode of operating the bidirectional power converter to charge an energy storage resource using (a portion of power provided by) the input voltage and a second mode of producing a backup voltage from the energy storage resource to power the load as a substitute to the input voltage such as when the input voltage is below a threshold value.