High efficiency AC/DC power supply

• US 8,446,134 B2
• Filed: 03/10/2009
• Issued: 05/21/2013
• Est. Priority Date: 03/10/2008
• Status: Active Grant

• Current Assignee: Tower Semiconductor Limited
• Original Assignee: Techtium Ltd.
• Inventors: Manor, Dror, Lebens, Pascal, Van Rooij, Ronny
• Primary Examiner(s): Vu, Bao Q
• Application Number:
  US12/921,402
• Publication Number:
  US 20110051476A1
• Time in Patent Office: 1,533 Days
• Field of Search: 363/16, 363/41, 363/21.04, 363/21.07, 363/21.12, 363/21.15, 323/222, 323/266, 323/271, 323/282
• US Class Current: 323/271
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/0096 Means for increasing hold-up time, i.e. the duration of time that a converter's output will remain within regulated limits following a loss of input power
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• 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

A power supply for converting AC to a regulated DC output current, utilizing two serial switched mode power supplies, the first providing an intermediate DC output voltage with only moderate ripple properties, this output being input to the second, which operates as a DC/DC converter to provide the desired output with low ripple and good regulation. The diode rectifier assembly has no reservoir/smoothing capacitor, or one of much smaller capacitance than in prior art power supplies. The large resulting rectifier output ripple is overcome by use of the two power supply units, at least the first having a smoothing capacitor at its output. A majority of the energy stored in this capacitor is utilized during each AC half cycle. Such power supplies also provide improved hold-up times. The power supply is also constructed to have low standby power consumption, by use of a double burst configuration.

Claims

1. A power supply for converting an AC supply to a DC output, said power supply comprising:

a rectifier assembly connected to said AC supply, and providing a rectified current;

a first converter inputting said rectified current, and providing a first DC output current at a voltage substantially below that of said AC supply;

a second converter inputting said first DC output current, and providing a second DC output current; and

at least one capacitor disposed at the output of said first converter for reducing the voltage drop of said first DC output current during zero-crossing of said input AC supply,

wherein the capacitance of said at least one capacitor is such that a major part of its stored energy is discharged during every half cycle of said AC supply.

2. A power supply according to claim 1 and wherein said first converter inputs said rectified output current during at least a major part of each half cycle of said AC supply.

3. A power supply according to claim 1, and wherein said rectified current at the input to said first converter has a voltage drop during zero-crossing of the input AC supply, being a significant fraction of its peak voltage.

4. A power supply according to claim 1, and wherein said rectified current at the input to said first converter has a voltage drop during zero-crossing of the input AC supply, being at least 50% of its peak voltage level.

5. A power supply according to claim 1 and wherein said first converter provides an output voltage higher than that of said second converter.

6. A power supply according to claim 5 and wherein said first converter provides an output voltage at least one third higher than that of said second converter.

7. A power supply according to claim 5 and wherein the resulting reduced current flowing in said first converter reduces power dissipation therewithin.

8. A power supply according to claim 5 and wherein said second converter operates with an output to input voltage ratio sufficiently small that said second converter has an efficiency substantially higher than that which would be obtained if said rectified output current were input directly thereto.

9. A power supply according to claim 1, and wherein said at least one capacitor on the output of said first converter has a value such that said first DC output current has a voltage drop during zero-crossing of the input AC supply of at least 25% of the output voltage of said first converter when said power supply is providing a DC output current at its rated level.

10. A power supply according to claim 1, and wherein said at least one capacitor on the output of said first converter has a value such that said first DC output current has a voltage drop during zero-crossing of the input AC supply of at least 50% of the output voltage of said first converter when said power supply is providing a DC output current at its rated level.

11. A power supply according to claim 1, wherein said input by said first converter of rectified current during switch-on of said power supply reduces inrush current sufficiently that said power supply can dispense with the need of inrush current protection.

12. A power supply according to claim 1, wherein the utilization of rectified output current by said first converter over a major part of each cycle of said AC supply is operative to increase the power factor of said power supply.

13. A power supply according to claim 1, wherein said rectifier assembly and said first converter are disposed in a module physically separated from said second converter, and connected thereto by a flexible connection cord.

14. A power supply according to claim 13, wherein said module further comprises said at least one capacitor.

15. A power supply according to claim 13, wherein said module is part of a wall plug receiving AC power from a wall socket, and said second converter is part of a plug for connecting to a load device of said power supply.

16. A power supply according to claim 13, wherein said second converter is disposed within a mobile electronic device.

17. A power supply according to claim 13 further comprising a retractable reel, on which said connection cord is stored when not in use.

18. A power supply comprising:

at least first and second serially connected converters;

a first at least one capacitor connected across the output of said first converter;

a voltage detection element monitoring the voltage on said first at least one capacitor, causing said first converter to enter a sleep mode if said voltage on said first at least one capacitor exceeds a first predetermined level, and arousing said first converter from its sleep mode if said voltage on said first at least one capacitor falls below a second predetermined level;

a second at least one capacitor connected across the output of said second converter; and

a voltage detection element monitoring the voltage on said second at least one capacitor, causing said second converter to enter a sleep mode if said voltage on said second at least one capacitor exceeds a first preselected level, and arousing said second converter from its sleep mode if said voltage on said second at least one capacitor falls below a second preselected level.

19. A power supply according to claim 18 and wherein, when no load current is demanded therefrom, said first converter may be aroused to raise the voltage on said first at least one capacitor to said first predetermined level, and said second converter may be aroused to raise the voltage on said second at least one capacitor to said first preselected level.

20. A power supply according to claim 18 and wherein when no load current is demanded from said power supply, it enters a sleep mode with essentially no operating current expended other than that required to maintain responsivity of said converters to arousal signals, and that lost by component leakage.

21. A power supply according to claim 18 and wherein each one of said first and said second converters is adapted to provide current only down to predefined lower current limits, and wherein if the current drawn from said power supply falls below a second limit, lower than either of said predefined lower current limits of said converters, at least one of said converters enters a sleep mode until aroused to fill its at least one capacitor.

22. A power supply according to claim 21 and wherein said predefined lower current limit of either of said converters is chosen such that it provides current only at a level which maintains a minimum predefined power supply efficiency.

23. A power supply according to claim 21, wherein if the current drawn from said power supply falls below said second limit, said at least one converter provides current in bursts greater than its predefined lower current limit, and enters a sleep mode between bursts.

24. A power supply according to claim 18, wherein said first converter is physically separated from said second converter, said converters being connected by a connection cord.

25. A power supply according to claim 24, wherein said first converter is part of a wall plug receiving AC power from a wall socket, and said second converter is part of a plug for connecting to a load device of said power supply.

26. A power supply according to claim 24, further comprising a retractable reel, on which said connection cord is stored when not in use.

27. A switched mode power supply comprising:

an input for receiving a DC current;

switching circuitry for generating a high frequency AC current from said input DC current;

a high frequency transformer receiving said high-frequency AC current in a primary winding, said transformer having a secondary winding for outputting said high-frequency AC current at a desired voltage level;

a rectifier unit for rectifying said transformed said high-frequency AC current to a DC output current; and

an additional primary winding on said high-frequency transformer coupled magnetically to said secondary winding,

wherein a signal injected onto said secondary winding induces into said additional primary winding a signal electrically isolated from said secondary winding, and usable for control functions in said switched mode power supply.

28. A switched mode power supply according to claim 27, further comprising a rectifier assembly for connecting to an AC mains supply, for providing said DC input current.

29. A switched mode power supply according to claim 28, wherein said DC output current is isolated from said AC mains supply.

30. A switched mode power supply according to claim 28, wherein said DC output current is isolated from said AC mains supply without the need for an optocoupler.

31. A power supply for converting an AC supply to a DC output, said power supply comprising:

a rectifier assembly connected to said AC supply, and providing a rectified current;

a first converter inputting said rectified current, and providing a first DC output current at a voltage substantially below that of said AC supply;

a second converter inputting said first DC output current, and providing a second DC output current; and

at least one capacitor disposed at the output of said first converter for reducing voltage drop in said first DC output current,

wherein the capacitance of said at least one capacitor is such that said voltage drop in said first DC output current is limited so that said power supply continues to provide a predetermined output power level for a predetermined time period following cessation of said AC supply.

32. A power supply according to claim 31, wherein the capacitance of said at least one capacitor is such that a major part of its stored energy is discharged during said predetermined time period during which the power supply continues to provide a predetermined fraction of its output.

33. A power supply according to claim 31, wherein said at least one capacitor is charged to a predetermined constant voltage by said first converter essentially independent of allowable changes in the AC supply voltage.

34. A power supply according to claim 33, wherein said at least one capacitor is charged to a predetermined constant voltage by said first converter essentially independent of which AC supply voltage standard is used.