Current limited electronic ringing generator

Details Current limited electronic ringing generator Current limited electronic ringing generator

1990-12-10

1993-11-09

Dwyer, James L.

Telephonic communications

Call signal generating

379164, 379252, 379253, H04M 300, H04M 100

Patent

active

052609960

ABSTRACT:
An electronic ringing generator circuit with provision for power efficient current limiting and preservation of sinusoidal or near sinusoidal output waveform under overload conditions. A pulsewidth modulated DC-DC power convertor produces supply voltages for a linear class B power amplifier which has a low frequency low level sinusoidal signal applied to its input through a first controllable attenuator. The DC-DC convertor's reference input is also driven through a second controllable attenuator which is coordinated with the first controllable attenuator. The attenuators are operated in such a way that if the amplifier's output current exceeds a predetermined value, both the input signal and amplifier supply voltages are reduced in a coordinated manner so that simultaneously the output AC waveshape is preserved and the amplifier continues to operate at or very near optimum efficiency. The amplifier may be operated to produce a sinusoidal output (crest factor =1.41) or a slightly clipped sinewave with a specified minimum crest factor less than 1.41.

REFERENCES:
patent: 3927266 (1975-12-01), Stewart et al.
patent: 4211896 (1980-07-01), Ferrieu
patent: 4273964 (1981-06-01), Szpindel
patent: 4341928 (1982-07-01), Stanson et al.
patent: 4611097 (1986-09-01), Grimes
patent: 4656659 (1987-04-01), Chea, Jr.

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