Abstract: A power converter using a switching signal having at least three levels of amplitude, one of which amplitude levels has a zero amplitude level during a predetermined switching interval, is provided. The power converter includes a circuit module having first and second input terminals for receiving the switching signal. The circuit module in turn is made up of a first power transistor and second power transistor. Circuitry is electrically coupled to a predetermined one of the power transistors for maintaining a predetermined voltage level across the gate terminal of the predetermined one of the power transistors during the switching interval of zero amplitude. The predetermined voltage level is chosen to enable that predetermined power transistor to continue in a respective "on" state notwithstanding of the presence of the switching interval of substantially zero amplitude.

Abstract: A method and apparatus for maintaining relatively low ripple current in a dc-dc converter while minimizing the size of an inductive line filter utilizes a transformer having at least a pair of secondary windings in which the secondary windings are selected to have different numbers of winding turns depending on the specific design of the ideal duty factor at which the converter will be operated. In addition, the converter is provided with an active pre-load which establishes a continuous conduction current when load current is below some selected minimum value in order to provide control stability during light load conditions without converter oscillations.

Abstract: A pulse width modulated control signal for use in motor control and with power supplies is generated by a dual-mode controller having variable frequency control in a discontinuous current operating mode. The controller also provides control in a continuous current operating mode, and makes a smooth transition therebetween.

Abstract: Messages sent from an earth station to a satellite by a command link are authenticated within the satellite before being executed. Authentication is accomplished by comparing a codeword appended to the message to a codeword generated within the satellite. This codeword is a cryptographic function of the message data and a secret operating key. A key change command from the earth station causes the satellite authenticator to generate a new operating key based a secret master key, a supplemental private code, and a publicly available initialization vector. The codeword appended to the key change command is encrypted in the new key and, if it agrees with a codeword generated by the satellite authenticator, the new key becomes the operating key and the key change function is complete.