International Business Machines Corporation

Arthur G Black

Larry Mason Ernst

John H Dodge

John R Mazzuca

Carl J Palmucci

Surya K Rao

This invention provides a means for suppressing radiated electromagnetic radiation in high current AC/DC power supplies. This radiation is the result of rectifier diode transient noise which is propagated through the electrical network of the power supply. The transient noise is propagated through the electrical and mechanical connections of the diodes to the transformer secondary. These connections have stray impedance which allows high frequency noise to be propagated through them. The stray impedances can be modulated to suppress the high frequency noise propagation without adding discrete inductor or capacitor elements to the electrical network. The modulation of the stray impedances is accomplished by adjusting the current sharing between rectifier diodes. This is accomplished by splitting the parallel connection between rectifier diodes, and making the connection of the diodes to the transformer secondary at various points along the secondary. The separate impedance of both the transformer and the individual connections will modulate the existing stray impedance to suppress the radiated electromagnetic noise.

Suppression of radiated EMI for power supplies

Control system which measures overshoot or undershoot time of a controlled variable with respect to a set value and adjusts a proportional count if the overshoot or undershoot time period exceeds fixed values. The proportional count is used to control the system output in a proportional manner, such as supplying k out of every n cycles of power, where k represents the proportional count. To prevent excessively long periods of overshoot or undershoot, an overlimit detector provides adjustments of the proportional count when the overshoot or undershoot measured time exceeds an overlimit value. The control system has general applicability but is described in the temperature control of a fuser hot roll such as used in electrophotostatic copiers.

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Red Hook, NY, United States of America

Arthur G Black