Abstract: This application relates to an energy storage device protection circuit for use in a hybrid system supplying power to an active dynamic DC load, such as an electric vehicle drive. The circuit prevents over-discharge of the energy storage device and ensures that the system will be capable of delivering a minimum acceptable level of power to the load, even when the energy storage device is in a low state of charge or other de-rated mode. The hybrid system includes a power generator such as fuel cell capable of supplying at least the average power value requirements of the load and an energy storage device such as a battery or capacitor capable of supplying at least the difference between the peak power requirements of the load and the average power value. A controller is provided for controlling the relative supply of power to the load from the power generator and the energy storage device.

Abstract: A method and apparatus for digitally controlling the average input current of a switch mode power supply are disclosed. In preferred embodiments, the switch mode power supplies are DC-DC converters. One aspect of the invention relates to a method for controlling the switch of a switch mode power supply by digitally sampling the input current once during each power supply switching cycle at a time that is synchronized with the switching cycle. The predetermined time at which the input current is sampled may be midway through the time that the switch is in the “ON” state. This midway time may also be delayed slightly to compensate for delays associated with the switch.