Importance

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Abstract

A power converter is provided located in a remote terminal of a telephone system, the telephone system having a central office which powers a plurality of telephone loops with a DC voltage having at least two substantially different levels. The remote terminal power converter derives remote terminal output load voltages including a low voltage regulated supply from the DC voltage provided to the loop from the central office. The remote terminal power converter comprises a synchronous rectifier for providing a predetermined low voltage regulated supply. The remote terminal power converter further comprises a receiving circuit connected to the loop for receiving DC voltage from the central office and supplying a low voltage output for producing the low voltage regulated supply. A switch is associated with the receiving circuit for producing an output signal on the low voltage output, the output signal having sequential charging, flyback, and discontinuous intervals. The discontinuous interval has a variable time duration dependent on at least the voltage level being coupled to the loop by the central office. The synchronous rectifier is coupled between the low voltage output and the low voltage regulated supply and includes a power switching device, and a circuit responsive to the termination of the charging interval for driving the power switching device on. The synchronous rectifier also includes a circuit for sensing a condition indicative of the onset of the discontinuous interval and turning off the power switching device for at least the duration of the discontinuous interval, independent of the time duration of the discontinuous interval.

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First Claim