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Chronology - On 14 July 2016, inventor Newton E. Ball [Newt] filed a provisional patent application covering the DC Transformer. On 14 July 2017 inventor Newton E. Ball [Newt] filed a utility patent application covering the DC Transformer.
Single Sentence Abstract - If an array of driven switches reverses the connection of each winding of a close-coupled, prior art, transformer, simultaneously, and periodically, then the low-frequency response, is extended to include DC, and the transformer-array assembly is, in fact, a DC Transformer.
New Symbol for the Close-coupled Transformer -
This is a new symbol, for a prior art device: The close coupled transformer.
Adding an Array of Driven Switches, Between the Windings and the Ports -
The dashed line actuation of the switches, moves all four arms, up together, then down together. Actuation occurs often enough to prevent saturation in the core.
Retention of Properties - The DC transformer retains the properties of the close-coupled transformer, because it is a transformer, switch connected. The properties include continuous, reversible coupling, and reflection, between the ports, at very high speed. Reflection of voltages is in direct proportion to turns ratio. Reflection of currents is in inverse proportion to turns ratio. Reflection of impedances is in direct proportion to the square of turns ratio.
Signal Analysis - If a DC voltage is impressed at the left port as a source, and a load impedance is connected at the right, then, Initially, with all four arms up, there is no inversion. The voltage induced at the secondary, load side, has the same polarity as the source. At switch actuation [arms down], two inversions are introduced in the port-to-port signal path. The two inversions net to, no inversion, port-to-port. Halfway through, there is one inversion source-to-core. Core to load, there is another inversion. Port to port, that is, source to load, there is always no inversion, or two inversions. Thus the load always tracks th source. From a DC source, a square wave of winding voltage has been created, from the standpoint of the core, a square wave with no DC component. This square wave is synchronously rectified by the switches on the right, to a DC signal at the load port.
Primacy of the Continuous, Reversible, Coupling and Reflection Characteristics - The signal analysis above, is just to help explain, to signal-minded engineers, how a transformer can couple DC. The important characteristic is the fast, reversible, continuous connection between one port and another.
Expansion of the concept to practice - The transformer symbol emphasizes the close coupling, by showing interleaved one-to-one windings on a circular torus core, with switch symbols originated for mechanical switches. The concepts of continuous reversible coupling, and fast reflection, apply with any turns ratio, any number of windings, and with electronic switches utilizing any kind of transistors as switches.