In a switching power supply including a step-up transformer having primary and secondary windings, wherein in each successive cycle of operation, during a first period of time a voltage pulse is applied across the primary winding for causing forward current in the secondary to flow through a shuttle capacitor and output capacitor connected in series with the secondary winding at this time, for charging the output capacitor to a voltage level approaching the voltage across the series circuit of the shuttle capacitor and secondary winding, and in an immediately following second period of time terminating the voltage pulse across the primary winding, and allowing flyback energy in the secondary winding to charge and be captured only by the shuttle capacitor for transfer to the output capacitor during the next cycle of operation.

Power supply having combined forward converter and flyback action for high efficiency conversion from low to high voltage

A power feed system for telephone and/or information technology terminals (1) is connected to a transmission and remote power feed link (4) of the terminal and comprises a switch mode power supply unit (7) connected to the wires of the link and a regulator (8) at the output of the switch mode power supply unit which supplies at least part of the power required by the terminal and which includes a circuit to ensure progressive starting of the switch mode power supply unit when the terminal is powered up via the link.

Power feed system for telephone and/or information technology terminals

A multifilar transformer apparatus and winding method where first and second windings are bifilar wound around a core for NA turns, the first, second, third, and fourth windings are quadfilar wound around the core for NB turns, and the first and second windings are again bifilar wound around the core for NC turns. Winding symmetry is preserved and a turns ration of (NA+NB+NC):2NB is achieved.

Multifilar transformer apparatus and winding method

In a power supply device in which a switching
means for controlling power supply to the input winding
of a transformer is connected to a resonance capacitor
connected to the input winding of the transformer so as
to obtain a predetermined DC voltage at an output
capacitor connected to the output winding of the
transformer in accordance with switching of the
switching means, the device has a leakage transformer
as the transformer, and a control means for controlling
switching of the switching means, and the control means
is controlled by the output voltage from the second
output winding of the transformer, has a means for
producing resonance between the resonance capacitor and
a leakage inductance between the input winding and
first output winding of the leakage transformer upon
switching of the switching means, and delays the rise
timing of the terminal voltage of the switching means
using that means to reduce losses upon switching of the
switching means.

Power supply device

A power supply circuit for use with telecommunication subscriber lines provides a substantially constant power output over one range of load impedances and a substantially constant voltage output over a range of load impedances greater than a critical impedance. The circuit employs a transformer which includes a sense winding for sensing output voltage across the load. For load impedances below the critical value, the current into the primary of the transformer is controlled by means of a current sensing device sensing the amount of primary current. However, for load impedances greater than the critical impedance the output of the sense winding controls and current to the primary is reduced to avoid the output voltage from rising substantially even in the event of an open circuit load condition. In one embodiment, a supervisory circuit provides a signal indicative of the on-hook and off-hook states of the subscriber line by sensing primary current flow. In an alternate embodiment, a supervisory circuit provides an indication of the on-hook and off-hook states of the subscriber line in response to a signal derived from the sense winding voltage.

Power supply with regulated output voltage

A floating battery feed circuit (10) comprising a switching-mode, flyback power converter (200) wherein a capacitor (C3) connected to a converter transformer winding (201) develops a relatively low voltage used to energize the converter control circuitry (100). The converter control circuitry prevents the operation of the battery feed circuit unless the voltage developed by the capacitor is above a predetermined magnitude. The power converter advantageously operates in only a constant-power mode regardless of loop impedance.

Robert Charles Hudson

Papers

Floating battery feed circuit