Method and apparatus for soft switched AC power distribution

A method for providing a soft switched AC power distribution circuit, the method comprising the steps of:

• providing a source transformer capable of operating in both flyback and forward modes, the transformer having:
• a first primary winding;
• at least one first secondary intermediate winding;
• and a first core capable of storing energy in a first magnetic field;
• providing at least one load transformer capable of operating in both flyback and forward modes, the at least one load transformer having:
• a second primary winding;
• at least one second secondary winding;
• a second core capable of storing energy in a second magnetic field;
• providing at least one AC to DC converter, the AC to DC converter having;
• at least one rectifier connected to the at least one second secondary winding, polarized such that the rectifier does not conduct when the voltage of the power source is applied to the source transformer primary winding;
• and
• at least one filter capacitor, connected to the at least one rectifier;
• connecting an EMI shielded connection between the at least one first secondary intermediate winding and the second primary winding of the at least one load transformer;
• providing a synchronization control circuit to control current through the first primary winding, the synchronization control circuit having a switching device;
• controlling the time at which current conduction is initiated in the switching device;
• setting a first turns ratio of the source transformer and a second turns ratio of the at least one load transformer such that the natural resonance of the soft switched AC power distribution circuit will allow the voltage across the switching device to collapse to zero without current being conducted in the switching device;
• initiating a first current flow through the first primary winding to induce energy storage in the first magnetic field and the at least one second magnetic field;
• interrupting the first current flow through the first primary winding in order to collapse the first and the at least one second magnetic field;
• transferring energy from the collapsing first and at least one second magnetic field to the at least one AC to DC converter to at least one load, via the EMI shielded connection.

A method for controlling electromagnetic interference (EMI) in a soft switched AC power distribution system, the method comprising the steps of:

• providing a source transformer capable of operating in both flyback and forward modes, wherein the transformer comprises:
• a first primary winding;
• at least one first secondary intermediate winding;
• and
• a first core capable of storing energy in a magnetic field;
• providing at least one load transformer capable of operating in both flyback and forward modes, the load transformer comprising;
• a second primary winding;
• at least one second secondary winding;
• a second core capable of storing energy in a second magnetic field;
• providing at least one AC to DC converter, the at least one AC to DC converter comprising at least one rectifier;
• connecting the at least one AC to DC converter to the second secondary winding polarized such that the at least one rectifier does not conduct when the voltage of the power source is applied to the source transformer primary winding;
• connecting at least one filter capacitor to the at least one rectifier;
• providing an EMI shielded connection between the at least one first secondary intermediate winding and the second primary of the at least one load transformer;
• setting the turns ratios of the transformers such that the natural resonance of the transformers and associated circuitry will cause the voltage across the switching device to collapse to zero without current being conducted in the switching device;
• providing a synchronization control circuit connected to the primary winding, the synchronization circuit comprising;
• a switching device;
• a pulse width modulator for controlling the duration of current flow through the switching device;
• a peak voltage detector coupled to the at least one secondary winding, wherein the peak voltage detector provides a feedback signal, proportional to the output voltages, for input to the pulse width modulator;
• a zero voltage control circuit connected to the switching device and the pulse width modulator, wherein the zero voltage control circuit controls the time at which conduction is initiated in the switching device, such that conduction begins when there is a substantially null voltage across the switching device and substantially null current flow in the at least one second secondary winding of the at least one load transformer;
• initiating current flow through the first primary winding to induce energy storage in the first and the at least one second core;
• interrupting current flow through the first primary winding in order to collapse the first and at least one second transformer's magnetic field;
• and
• transferring energy from the collapsing magnetic fields to at least one load.

A soft switched AC power distribution apparatus for minimizing electromagnetic interference and AC losses in an AC power distribution system, the AC power distribution apparatus comprising:

• a transformer capable of operating in both flyback and forward modes, wherein the transformer comprises:
• a primary winding;
• at least one intermediate secondary winding;
• a synchronization control circuit connected to the primary winding comprising a switching device for controlling current flow through the primary winding;
• a variable reactance connectable to the switching device, wherein the variable reactance is operable to adjust voltage and current rise times in the soft switched AC power distribution apparatus, and wherein the variable reactance is adaptable to store energy resulting from a collapsing magnetic field;
• a pulse width modulator for controlling a duty cycle of the switching device;
• a peak voltage detector connectable to the at least one intermediate secondary winding;
• a logic circuit connectable to the primary winding and the pulse width modulator, the logic circuit operating in conjunction with the peak voltage detector to produce a synchronization signal and a feedback signal, respectively, for input to the pulse width modulator;
• and
• at least one load transformer connectable to the at least one intermediate secondary winding, wherein the at least one load transformer connectable to the at least one intermediate secondary winding is connectable via an EMI shielded connection.

A method for providing soft switched AC power distribution, the method comprising the steps of:

• providing a transformer capable of operating in both flyback and forward modes, wherein the transformer comprises a primary winding and at least one secondary intermediate winding;
• providing a synchronization control circuit for controlling current in the primary winding wherein the synchronization control circuit includes a switch connected to the transformer;
• initiating current flow through the primary winding to induce energy storage in the transformer;
• interrupting current flow through the primary winding in order to collapse the transformer's magnetic field;
• transferring energy from the collapsing magnetic field to the at least one secondary intermediate winding by providing a variable reactance connectable to the primary winding, the variable reactance adaptable to minimize power loss and electromagnetic interference at least one operating condition;
• and
• sensing substantially null voltage across the switch indicating substantial transfer of energy to the at least one secondary intermediate winding, where upon current flow through the primary winding is restored.