Battery charger circuit with low standby power dissipation

• US 6,339,314 B1
• Filed: 12/27/2000
• Issued: 01/15/2002
• Est. Priority Date: 12/27/2000
• Status: Expired due to Fees

• Current Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Original Assignee: Philips Electronics North America Corporation (Koninklijke Philips N.V.)
• Inventors: Bruning, Gert W.
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Tibbits, Pia
• Application Number:
  US09/749,712
• Time in Patent Office: 384 Days
• Field of Search: 320/108, 320/122, 320/128, 307/30, 307/38, 307/126, 307/112
• US Class Current: 320/128
• CPC Class Codes: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters
• CPC Class Codes: H02J 9/005 using a power saving mode for copiers G03G15/5004
• CPC Class Codes: H02J 9/007 Detection of the absence of a load
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y04S 20/20 End-user application control systems

Abstract

The invention concerns an electronic circuit for reducing the current consumption of a transformer (1). This circuit comprises a control circuit in the secondary circuit of the transformer (1) and a switch (2), controlled by the control circuit, in the primary circuit of the transformer (1) for separating the primary circuit of the transformer (1) from the power supply (3). The control circuit comprises a detector (6) for detecting the no-load state of the transformer (1). If the transformer (1) is in the no-load state, the switch (2) on the primary side is opened at least temporarily.

Claims

1. A battery charger circuit for controlling a current through a primary winding of a transformer comprising:

a triggerable electronic switch having a gate terminal and first and second terminals through which an alternating current is supplied, the triggerable electronic switching allowing current to flow to the transformer when there is a load and preventing current from flowing to the transformer when there is no load;

a sensing element coupled between the second terminal of the triggerable electronic switch and the primary winding of the transformer;

a capacitive element coupled to the second terminal of the triggerable electronic switch;

a threshold detector having an input and an output, the input of the threshold detector coupled to the gate terminal of the triggerable electronic switch to allow current to flow to the gate terminal of the triggerable electronic switch at a predetermined voltage of the capacitive element;

a load detector circuit coupled to the sensing element to sense the current flowing through the sensing element; and

a switching element to allow the capacitive element to be charged when a first current is sensed by the load detection circuit and to prevent the capacitive element from charging when a second current is sensed by the load detection circuit.

2. The battery charger circuit of claim 1, wherein the triggerable electronic switch comprises one of a triac and a bi-directional switch.

3. The battery charger circuit of claim 1, wherein the threshold detector comprises a diac.

4. The battery charger circuit of claim 1, wherein the switching element comprises a transistor.

5. The battery charger circuit of claim 1, wherein the predetermined voltage is a breakdown voltage of the threshold detector.

6. The battery charger circuit of claim 1, further comprising a resistor coupled to the gate terminal of the triggerable electronic switch and the in put of the threshold detector.

7. The battery charger circuit of claim 1, further comprising a power supply to p provide current to the first terminal of the triggerable electronic switch.

8. The battery charger circuit of claim 1, wherein the first current includes a load current and a magnetizing current and the second current only includes the magnetizing current.

9. A battery charger circuit comprising:

a transformer having a primary winding and a secondary winding;

a triggerable electronic switch to provide a charging current when a load is connected to the secondary winding and to shut off the charging current when the load is disconnected from the secondary winding;

a sensing element connected between the triggerable electronic switch and the primary winding; and

a threshold detector coupled to the sensing element to trigger the triggerable electronic switch to a conductive state when a voltage of the threshold detector reaches a predetermined value and to maintain said conductive state when a load current is flowing through said sensing element.

10. The battery charger circuit of claim 9, wherein the triggerable electronic switch includes one of a triac switch and a bi-directional switch.

11. The battery charger circuit of claim 9, wherein the threshold detector comprises a diac.

12. The battery charger circuit of claim 9, further comprising a capacitive element coupled to the threshold detector.

13. The battery charger circuit of claim 9, further comprising a switching element coupled to the threshold detector.

14. The battery charger circuit of claim 9, further comprising a load detection circuit coupled to threshold detector.

15. A battery charger circuit comprising:

a switching element;

a sensing element connected in series between the switching element and a primary winding of a transformer; and

a control circuitry for rendering the switching element conductive when a load current is flowing through the sensing element and for rendering the switching element non-conductive when the load current is not flowing through the sensing element.

16. The battery charger circuit of claim 15 further comprising a bypass device coupled to the control circuitry.

17. The battery charger circuit of claim 15 wherein the control circuitry comprises a threshold detector.

18. The battery charger circuit of claim 15 wherein the control circuitry comprises a timing circuit.

19. The battery charger circuit of claim 15 wherein the control circuitry comprises a trigger device.

20. The battery charger circuit of claim 15 wherein the control circuitry comprises a threshold detector coupled to a triggering device and a timing circuit.

21. The battery charger circuit of claim 15, wherein said load current is greater than a magnetizing current, said magnetizing current flowing through said primary winding when a load is not connected to a secondary winding of said transformer.

22. A method of charging a load comprising:

providing current to charge a capacitive element;

rendering a threshold switch conductive when a voltage of the capacitive element reaches a predetermined voltage to supply a latching current through the threshold switch;

rendering a triggerable electronic switch conductive in response to the latching current to provide a primary current in a primary winding of a transformer;

sensing the primary current at predetermined intervals to determine whether there is a load;

maintaining the triggerable electronic switch in a conductive position when the primary current includes a load current plus a magnetizing current; and

opening the triggering electronic switch to interrupt the primary current for a predetermined interval when the primary current only consists of the magnetizing current.

23. The method of claim 22 wherein the triggerable electronic switch is one of a triac switch and a bi-directional switch.

24. The method of claim 22 wherein the threshold detector comprises a diac.

25. The method of claim 22, wherein said load current is greater than a magnetizing current, said magnetizing current flowing through said primary winding when the load is not connected to a secondary winding of said transformer.

26. A method to reduce standby current comprising:

defining a current path in series with a primary winding of a transformer;

sensing a current flowing through the current path;

allowing the current to flow to the primary winding when the current includes a load current and a magnetizing current; and

preventing the current from flowing to the primary winding when the current includes only a magnetizing current.

27. The method of claim 26, wherein said load current is greater than a magnetizing current, said magnetizing current flowing through said primary winding when a load is not connected to a secondary winding of said transformer.