Patent EA-001816-B1 (EA)
Title: An ac-dc power supply
Inventor: GREEN ANDREW WILLIAM
IPC: H02M7/217
Filed: 1996-10-24
Abstract: 1. A three phase transformer including: - three secondarys each formed from a conductive tube, the conductive tubes being substantially parallel and electrically connected at a first end thereof; - three transformer cores, each corresponding to a phase, each in the form of a cylindrical member threaded onto a corresponding conductive tube; and - three primary windings each corresponding to a phase, wound so as to pass through the interiors of adjacent pairs of said conductive tubes. 2. A transformer as claimed in Claim 1 wherein the cylindrical members are formed from a plurality of ferrite discs, each disc having an aperture therein adapted to accommodate a corresponding cylinder. 3. A transformer as claimed in Claim 1 or Claim 2 wherein the three conductive tubes form a single turn secondary winding. 4. An AC-DC power supply including a three phase transformer as claimed in any of Claims 1 to 3 receiving a pseudo AC three phase output and further including: - a three phase rectifier circuit generating a first rectified output in response to an input voltage; - a controlled three phase inverter circuit receiving the first rectified output and generating the pseudo AC three phase output; and - a second three phase rectifier circuit receiving the transformed pseudo AC three phase output from the transformer and generating an output DC supply. 5. An AC-DC power supply as claimed in either Claim 4 or Claim 5 wherein said controlled three phase inverter circuit further includes a plurality of switching devices. 6. An AC-DC power supply as claimed in claim 5 wherein said switching devices are power transistors. 7. An AC-DC power supply as claimed in any one of Claims 4 to 6 wherein the controlled three phase inverter circuit includes: - a three leg bridge structure; - each leg of said bridge structure comprising at least one controllable switching device; - at least one switching device of one of said legs forming a phase reference; and - wherein the voltage of the inverter circuit is controlled by means of Phase Modulation. 8. An AC-DC power supply as claimed in Claim 7 wherein the phase modulation is effected by said at least one switching device of the second leg having the relative phase shift controlled with respect to the phase reference; and said at least one switching device of the third leg having the relative phase shift controlled with respect to the phase reference to increase the phase shift relative to the phase reference and thereby controlling the output voltage level of the inverter circuit. 9. An AC-DC power supply as claimed in Claim 7 wherein said inverter circuit includes: - at least two switching devices per phase; - each said switching device having a capacitive element connected in parallel across it and each phase of the inverter output including an inductive element; - a respective capacitive element and inductive element of each phase forming an LC resonant circuit; and - wherein the turn-off of each said switching element is controlled to have a deadtime between switching phases during which time said LC resonant circuit causes the next sequential switching element that is to be turned on to have substantially zero voltage across it at the time of switching. 10. An AC-DC power supply as claimed in any one of Claims 4 - 9, wherein said AC-DC power supply is coupled with a cell unit, the DC output of the power supply connected to at least one cathode/anode electrode pair of the cell unit to cause the electrolysis of water to liberate hydrogen and oxygen gas. 11. A method of generating a DC power supply from a three phase AC power supply including providing a three phase transformer as claimed in any one of Claims 1 to 3, the method including: - rectifying said AC power supply to generate a rectified power supply; - inverting said rectified power supply to generate a pseudo AC three phase supply; - providing said three phase transformer with said pseudo AC three phase supply; and - rectifying an output from said three phase transformer. 12. A method of generating a DC power supply as claimed in Claim 11 wherein said pseudo AC three phase supply is of a frequency higher than said three phase AC power supply. 13. An AC-DC power supply as claimed in any one of Claims 11 or 12 wherein said frequency of said pseudo AC three phase output is greater than at least to one order of magnitude higher than the input voltage frequency. 14. An AC-DC power supply as claimed in any one of Claims 11 or 12 wherein said frequency of said pseudo AC three phase output is greater than at least to two orders of magnitude higher than the input voltage frequency. 15. A method of generating a DC power supply as claimed in Claims 11 to 14 wherein the voltage of said pseudo AC three phase supply is controlled by providing a three phase inverter, and including: - assigning a first phase as a phase reference; - controlling the relative phase shift of one of the other two phases so that the phase difference between the first phase and the one of the other two is reduced; and - controlling the relative phase shift of the third phase so that the phase difference between the third phase and the first phase is increased.