Other

Cherry Semiconductor Corporation

Nathan O Sokal

Richard S Redl

Bela Molnar

A flyback charger for an energy-storage capacitor has a controller for causing the energy-storage pulses of current in the transformer primary winding and the energy-delivery pulses of current in the transformer secondary winding to be nearly flat-topped. The controller includes a peak-current-commanding current-mode control or a valley-current-commanding current-mode control which controls the duration of a switching circuit on and off interval, respectively, responsive to the current flowing in the transformer primary winding and secondary winding, respectively. A feed-forward controller controls the duration of the switching circuit off and on interval, respectively, in response to the voltage provided by the secondary winding and D-C supply voltage, respectively. When using the valley-current-commanding current-mode controller, there may be a fixed duration of the switching circuit on interval.

Flyback charging with current mode controlled flyback converter

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

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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Lexington, MA, United States of America

Nathan O Sokal