Switchmode power converters for telephone subscriber line interf

Details Switchmode power converters for telephone subscriber line interf Switchmode power converters for telephone subscriber line interf

1995-02-16

1999-09-28

Zele, Krista

Telephonic communications

Subscriber line or transmission line interface

379252, 379324, 379351, 379353, 379373, 379401, 379413, 379418, 363 41, 327114, 327172, H04M 300, H04M 100, H02M 112, H03K 522, H03K 301

Patent

active

059600756

ABSTRACT:
A power converter forming part of a telephone subscriber line interface circuit selectively generates a ringing signal waveform, for supply to the line, or a supply voltage for a driver circuit for providing loop current on the line. First and second fixed frequency PWM signals are used to control the power converter, and hence the voltage which it generates, for the ringing signal waveform and the supply voltage respectively. The first PWM signal enables the power converter to provide a high power level needed for ringing signals. The second PWM signal has a lower frequency, and hence results in lower switching losses and power dissipation, and a lower duty cycle, suitable for the lower power level needed for the supply voltage, and is conveniently produced by masking pulses of the first PWM signal. The frequency of the second PWM signal is greater than 270 kHz, to avoid transmitting spectral energy to the line below this frequency.

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patent: 5323461 (1994-06-01), Rosenbaum et al.
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