Abstract: A power conversion array delivers power to a load. The array includes at least four power converters, each of the power converters comprising an output power port for connection to the load and a synchronization port for passing synchronization information. A synchronization medium connected to the synchronization ports of the converters carries the synchronization information among the converters. The synchronization medium defines paths among the synchronization ports such that every synchronization port is connected to every other synchronization port by at least one path that does not include a connection to the synchronization port of any of the other converters. In another aspect, in arrays which include at least three power converters, the synchronizing medium conveys synchronizing information via impedance elements connected to the synchronization ports by coupling conductors, and the path between any pair of coupling conductors includes exactly two impedance elements.

Abstract: A zero-current switching converter converts power from an input source for delivery to a load. In the converter, a switch opens and closes at times of essentially zero current to enable energy transfer back and forth between said input source and said converter. A controller is connected to control the switch to initiate, during a first portion of each of a succession of converter operating cycles, forward energy transfer from said input source; and in at least some of said converter operating cycles, also to initiate reverse energy transfer to said input source at times not contiguous with said first portion.

Abstract: A zero-current switching converter converts power from an input source for delivery to a load. In the converter, a switch opens and closes at times of essentially zero current to enable energy transfer back and forth between said input source and said converter. A controller is connected to control the switch to initiate, during a first portion of each of a succession of converter operating cycles, forward energy transfer from said input source; and in at least some of said converter operating cycles, also to initiate reverse energy transfer to said input source at times not contiguous with said first portion.

Abstract: AC-DC boost switching power conversion apparatus delivers power from a bipolar input voltage source to a load at a unipolar load voltage without including rectifiers directly in the path of the current which is delivered from the input source. By this means the converter exhibits lower power loss in semiconductor diodes and switches than is exhibited by prior art converters which interpose a rectifier between a bipolar source and a DC-DC boost converter. Power processing is performed by circuitry of the kind which includes an inductive element in series with the bipolar input source, shunt paths which include switching elements for recirculating a bipolar shunt current back toward the input source, a controller for turning the switching elements on and off during each of a series of converter operating cycles and rectification elements which are arranged to deliver a unipolar current to the load.

Abstract: AC-DC boost switching power conversion apparatus delivers power from a bipolar input voltage source to a load at a unipolar load voltage without including rectifiers directly in the path of the current which is delivered from the input source. By this means the converter exhibits lower power loss in semiconductor diodes and switches than is exhibited by prior art converters which interpose a rectifier between a bipolar source and a DC-DC boost converter. Power processing is performed by circuitry of the kind which includes an inductive element in series with the bipolar input source, shunt paths which include switching elements for recirculating a bipolar shunt current back toward the input source, a controller for turning the switching elements on and off during each of a series of converter operating cycles and rectification elements which are arranged to deliver a unipolar current to the load.

Abstract: Open-loop means for controlling the speed of a d.c. motor controlled print head moving across a document. A switch couples a first voltage to the d.c. motor to accelerate the print head in a first direction. When the print head reaches the desired velocity, the first voltage is decoupled from the motor and a highly regulated voltage is coupled to the d.c. motor to move the print head at the desired velocity. The switch reverses the voltage polarity at the input terminals of the d.c. motor to decelerate the print head, accelerate it in the opposite direction and maintain the desired velocity as it moves in the reverse direction. Logic means detects the direction of carriage movement and connects the first voltage to the d.c. motor for an interval sufficient to bring the d.c. motor to the desired speed in the shortest practical interval. The second voltage maintains the constant speed until the print head reaches the end of the line.

Abstract: Color control means for selectively positioning one color of a two-color ribbon between a document-supporting platen and a print head having means for selectively impacting the desired ribbon portion against the document, said color control means comprising a color-select solenoid energized by logic circuitry responsive to a print-color signal. The solenoid is energized to a first position to enable characters of a first color to be printed at selected positions along a line. The logic circuitry includes means for selectively deleting the line feed, and delaying the print enable and print head movement signals during a time interval sufficient to allow for the color select solenoid to move the ribbon to the opposite color position at which time the characters of the opposite color are printed.