DC-supply arrangement for a telecommunication line

Details DC-supply arrangement for a telecommunication line DC-supply arrangement for a telecommunication line

1987-06-17

1989-06-20

Ng, Jin F.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

323224, H04M 1900

Patent

active

048415642

ABSTRACT:
A switched mode DC power supply circuit for a telecommunication line, including a switched converter for charging an output capacitor from a DC source. The converter is controlled by a periodic control signal having a variable duty cycle so as to maintain a selected direct voltage level across the output capacitor. However, due to common mode currents on the telecommunications line, the capacitor may become charged above the selected voltage level even when the duty cycle of the control signal is reduced to zero. Such excess charge is returned to the DC source, without heat dissipation, by providing a further switched converter for coupling the capacitor to the DC source and which is controlled by a second periodic control voltage which is activated when the duty cycle of the first control voltage has been reduced to zero.

REFERENCES:
patent: 3531712 (1970-09-01), Cecchini
patent: 4168477 (1979-09-01), Burchall
patent: 4373117 (1983-02-01), Pierce
patent: 4459537 (1984-07-01), McWhorter
patent: 4546421 (1984-10-01), Bello et al.

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