 Apparatus for creating 3D audio imaging over headphones using binaural synthesis |
| Accordingly, it is an object of the present invention to provide an apparatus for creating three-... |
|
| System, apparatus, and method for improving speech quality in multi-party devices |
| A method, system, and apparatus are provided, such that cross talk terms may be removed from speech ... |
|
| Speaker excursion control system |
| OF THE PREFERRED EMBODIMENT Referring initially to FIG. 1, there is shown a sound system which may ... |
|
| Portable information terminal device with radio selective-calling receiver |
| In view of the foregoing, it is an object of the present invention to provide a portable ... |
|
| Digital graphic equalizer |
| An object of the invention is to remedy the major problems of prior digital graphic equalizers and, ... |
|
| Electric artificial larynx |
| It is an object of the present invention which has been made to solve the above problem to provide ... |
|
| Audio reproducing apparatus corresponding to picture |
| In view of such aspects, an object of the present invention is to provide an audio reproducing ... |
|
| Electro-optical device |
| With the above-mentioned problems with such prior arts in view, the present invention has been ... |
|
| Method of transmitting an audio signal |
| What is claimed is: 1. A method of transmitting an analog audio signal in digital form to be ... |
|
| Hot water tank assembly |
| The present invention provides in a first embodiment, a hot water heater for a portable dispenser ... |
|
|
Tracking switchmode power converter for telephony interface circuit
| Details |
Inventors: Boudreaux, Jr., Ralph R.;
Assignee: Adtran, Inc. (Huntsville, AL)
Primary Examiner: Barnie; Rexford
Assistant Examiner:
Attorney, Agent or Firm: Allen, Dyer, Doppelt, Milbrath & Gilchrist, P.A.
A comparator-based switchmode power converter monitors the most negative of the tip and ring line voltages, to control the supply voltage to a SLIC. The voltage applied to the SLIC's power terminals is slightly higher than the sensed voltage for different loop signaling conditions, including loop start, ground start balanced ringing. The switchmode converter includes a comparator coupled to a DC-DC output node downstream of a MOSFET switch installed in a DC supply rail of a source of DC supply voltage, and coupled to a power supply terminal of the SLIC. The comparator is also coupled to a set point node, which is coupled through a voltage offset path to each of tip and ring portions of the telephone line. The comparator functions to control the conductivity of the MOSFET to provide a modulated DC voltage to the SLIC, in accordance with that one of tip and ring loop voltages having the largest magnitude, so as to provide power supply tracking during loop current, superimposed voice signals, loop start, ground start and balanced ringing. |
|
DETAILED DESCRIPTION Pursuant to the present invention, this power consumption problem is substantially diminished by monitoring the line voltage, and using a reduced complexity switchmode power converter to control the voltage supplied to and therefore the voltage drop across the SLIC, so that the voltage applied to the SLIC's power terminals is slightly higher than the sensed voltage.
The voltage margin or headroom across the SLIC is dependent upon the specifics of the SLIC circuitry and is typically on the order of 2-15 V.
In accordance with a non-limiting, preferred embodiment, the reduced complexity switchmode power converter of the present invention is configured to provide power supply tracking during the SLIC's application of loop current and superimposed voice to the loop, and also during loop start, ground start and balanced ringing.
For this purpose, a comparator, which effectively functions as a pulse width modulator of the conductivity path through a MOSFET installed in the power supply rail to the SLIC, has a first input terminal coupled through a voltage divider to a `DC-DC output` node, downstream of a MOSFET switch installed in a (-48V) DC supply rail.
The comparator has a second input terminal coupled through a voltage divider to a `set point` or reference node.
The DC-DC output node is coupled through a post LC filter to the (-) DC power supply terminal of the SLIC.
The set point node is coupled through a Zener diode and a buffer transistor to diodes that connect to the tip and ring lines of the loop, and thereby provide for tracking of the most negative of the tip and ring portions of the loop.
The buffer transistor reduces loading on tip and ring and also removes the effect of the voltage drop through either diode.
The Zener diode provides a prescribed DC voltage offset (e.
g.
, -5V) between the set point node and the most negative of tip and ring, to give the SLIC headroom to operate.
The output of the comparator is coupled to the control gate of a MOSFET, having its source-drain path coupled in circuit with the DC power supply rail and an LC smoothing filter to the DC-DC output node
|
|
Audio Signal Processing 
