Other

Cherry Semiconductor Corporation

Richard S Redl

Nathan O Sokal

Robert F Redl

Bela Molnar

A circuit for decreasing the minimum duty ratio of a switching element in a power converter in response to a signal indicating that sensed current exceeds a second threshold. The circuit turns off the switching element when the sensed current exceeds a first threshold. The minimum duty ratio may be decreased, for example by increasing the period of the switching element or by increasing the 'off' time of the switching element. The circuit protects against current runaway.

Overcurrent protection for switching mode power converter

A circuit for enabling current mode control to be used with a capacitively coupled power converter. The circuit includes circuitry for comparing the voltage across a coupling capacitor with its intended voltage and for generating an unbalance signal corresponding to any deviation. The unbalance signal and an inverse of the unbalance signal are alternately provided to the current mode controller to modify the control of two switches or two pairs of switches in the power converter so as to reduce the unbalance.

Current-mode control of capacitively coupled power converters

An umbrella comprises a cover having open and closed positions. A hollow pole supports the cover. An operative wind-up assembly for selectively opening and closing the cover includes a mechanism mounted on the pole. A cable extends from the wind-up mechanism through the inside of the pole for activating the cover. Part of the wind-up mechanism includes a rotatable handle with an interiorly positioned spool. One end of the cable is attached around the spool for winding the cable when the handle is rotated to cause opening of the cover.

Umbrella with improved wind-up handle

A Class E switching-mode dc/dc power converter is obtained by adding a rectifier circuit at the output of a Class E dc/ac power inverter. It can operate at high efficiency at high switching frequencies. Further, the power switch is not subjected to high power dissipation or high second-breakdown stress while it is switching between the 'on' and 'off' states, even if the dc load on the power converter varies over a very wide range, e.g., from open-circuit to short-circuit. The high efficiency is achieved by shaping the waveforms of switch voltage and switch current so that the transitions of those two waveforms are displaced in time from each other. Then the power switch does not experience simultaneously high voltage and high current while switching. High efficiency and low stress on the switch are achieved under all load conditions by interposing a matching network between the output of the Class E dc/ac inverter and the input of the rectifier circuit. That matching network transforms the rectifier input impedance in such a way that the impedance presented to the output of the Class E dc/ac inverter is always in the range which generates switch voltage and current waveforms that yield low power dissipation and low second-breakdown stress during switching, for any value of dc load resistance at the output of the rectifier.

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Midland Park, NJ, United States of America

Richard S Redl