AC-DC power supply

• US 6,031,737 A
• Filed: 09/01/1998
• Issued: 02/29/2000
• Est. Priority Date: 10/24/1995
• Status: Expired due to Fees

• Current Assignee: Aquagas New Zealand Limited
• Original Assignee: Aquagas New Zealand Limited
• Inventors: Green, Andrew William
• Primary Examiner(s): BERHANE, ADOLF D
• Application Number:
  US09/051,991
• Time in Patent Office: 546 Days
• Field of Search: 363/17, 363/34, 363/37, 363/40, 363/44, 363/84, 363/95, 363/56, 363/125, 363/131
• US Class Current: 363/37
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

An AC-DC power supply system for receiving a three phase mains supply and outputting a transformed DC supply. The power supply unit has a rectifier circuit (30) providing an output to a three phase inverter circuit (40) to generate a pseudo AC three phase output of higher frequency than the AC supplied to the rectifier circuit (30). A three phase transformer (60) receives the pseudo AC three phase output and transforms the output to a three phase rectifier circuit (70) to generate the output DC supply. The inverter circuit (40) provides a three leg bridge structure with each leg having a switching device one of which is used to provide a phase reference whereas the other two legs control the relative phase shift on each leg to reduce the phase shift relative to the phase reference on one leg and increase the phase shift relative to the phase reference on the other leg.

Claims

1. An AC-DC power supply comprising:

a three phase rectifier circuit generating a first rectified output in response to an input voltage having an input voltage frequency;

a controlled three phase inverter circuit receiving the first rectified output and generating a pseudo-AC three phase output having a frequency higher than the frequency of the three phase AC supply supplied to the rectifier circuit, wherein the pseudo-AC three phase output is controlled by means of phase shifting;

a three phase transformer receiving said phase shift controlled pseudo-AC three phase output; and

a second three phase rectifier circuit receiving the transformed pseudo-AC three phase output from said transformer and generating the output DC supply, wherein said three phase transformer comprises;

three secondaries each formed from a conductive tube, said conductive tubes being substantially parallel and electrically connected at first end thereof;

three transformer cores, each corresponding to a phase, each in the form of a cylindrical member threaded onto a corresponding said 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. An AC-DC power supply as claimed in claim 1 wherein each said transformer core in the form of a cylindrical member formed from a plurality of ferrite discs, each disc having an aperture therein adapted to accommodate a corresponding cylinder.

3. An AC-DC power supply as claimed in claim 1 wherein said controlled three phase inverter circuit further includes a plurality of switching devices.

4. An AC-DC power supply as claimed in claim 1 wherein said controlled three phase inverter circuit includes switching devices in the form of power transistors.

5. An AC-DC power supply as claimed in claim 1 wherein said frequency of said pseudo-AC three phase output is substantially higher than the input voltage frequency.

6. An AC-DC power supply as claimed in claim 1 wherein said frequency of said pseudo-AC three phase output is greater than or equal to one order of magnitude higher than the input voltage frequency.

7. An AC-DC power supply as claimed in claim 1 wherein said pseudo-AC three phase output is greater than or equal to two orders of magnitude higher than the input voltage frequency.

8. A controllable three phase inverter circuit receiving a DC supply to produce a three phase pseudo AC output supply wherein the inverter comprises:

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 shifting the relative phases of each signal carried by each leg.

9. A controllable three phase inverter circuit as claimed in claim 8 wherein the phase modulation is effected by said at least one switching device of one of the other two legs 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.

10. A soft-switching three phase inverter circuit receiving a DC input supply and generating a pseudo AC three phase output supply wherein said inverter circuit comprises:

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 output supply 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.

11. A method for controlling the output voltage of a three phase inverter circuit comprising the steps of:

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 place 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.

12. An apparatus for the electrolysis of water to liberate hydrogen and oxygen gas, the apparatus comprising:

a cell unit having at least one cathode/anode electrode pair; and

an AC-DC power supply comprising;

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 a pseudo three phase output having a frequency higher than the frequency of the three phase AC supply supplied to said rectifier circuit, wherein the pseudo-AC three phase output is controlled by means of phase shifting;

a three phase transformer receiving the phase shift controlled pseudo-AC three phase output; and

a second three phase rectifier circuit receiving the transformed pseudo-AC three phase output from said transformer and generating the output DC supply, wherein said three phase transformer comprises;

three secondaries each formed from a conductive tube, said 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 said 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.