Battery charger with charge state detection on the primary side

• US 20070001648A1
• Filed: 06/07/2005
• Published: 01/04/2007
• Est. Priority Date: 06/08/2004
• Status: Active Grant

• Current Assignee: Friwo Gerätebau GmbH
• Original Assignee: Friwo Gerätebau GmbH
• Inventors: Bothe, Michael, Breuch, Georg, Berghegger, Ralf
• Granted Patent: US 7,362,075 B2
• Time in Patent Office: Days
• US Class Current: 320/132
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/007182 in response to battery voltage
• CPC Class Codes: H02J 7/04 Regulation of charging current or voltage
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop

Abstract

The present invention relates to a battery charger for charging a battery. The present invention especially relates to a battery charger comprising a switching power supply controlled on the primary side and a charge monitoring circuit for monitoring the charge state of the battery. For providing an improved battery charger which allows a secure and reliable charging of batteries with a reduction of the circuit complexity, the costs for appliances and the construction size, the charge monitoring circuit is—according to the invention—disposed in the switching circuit on the primary side of the battery charger.

Claims

1. Battery charger for charging a battery

wherein the battery charger (100) comprises a switching power supply (102) controlled on the primary side with at least one converter connected to a switching circuit (106) on the primary side and to a switching circuit (108) on the secondary side, with a regulation and driver circuit (110) for regulating the power transferred to the secondary side (108), and a charge monitoring circuit (104) for monitoring the charge state of the battery,

wherein the charge monitoring circuit (104) is disposed in the switching circuit (106) on the primary side of the battery charger (100).

2. Battery charger according to claim 1, wherein the charge monitoring circuit (104) comprises a temperature detection device (123) for detecting the temperature of the battery (114) and is designed so as to control the power transfer in response to the measured temperature.

3. Battery charger according to claim 2, wherein the temperature detection device (123) comprises a resistor with negative temperature coefficients (116) which is electrically isolated with respect to the battery (114).

4. Battery charger according to at least one of the preceding claims, wherein the charge monitoring circuit (104) comprises a time switching device (122) which terminates the power transfer after a predetermined charging period.

5. Battery charger according to claim 4, wherein the time switching device (122) comprises an oscillator circuit (126) for generating a time pulse.

6. Battery charger according to claim 4, wherein the time switching device (122) is designed so as to generate a time pulse from a mains frequency.

7. Battery charger according to at least one of the preceding claims, wherein the switching power supply (102) comprises a switch on the primary side and a transformer with an auxiliary winding in which, after opening the switch on the primary side, an auxiliary voltage is induced, and wherein the regulation and driver circuit (110) is designed so as to regulate the output voltage and/or the output current of the switching power supply in dependence on the induced auxiliary voltage.

8. Battery charger according to at least one of the preceding claims, wherein the battery charger further comprises a logic circuit (124) for storing values of the output voltage of the switching power supply as actual instant values of the battery voltage and for comparing consecutive actual values, wherein the logic circuit (124) is designed so as to terminate the charging process if the actual value is reduced during several consecutive samplings.

9. Battery charger according to at least one of the preceding claims, wherein the logic circuit (124) is designed so as to cause the regulation and driver circuit (110) after the termination of the charging process to transfer a small charge conservation current to the battery.

10. Battery charger according to at least one of the preceding claims, wherein the charge monitoring circuit (104) is designed so as to monitor the switching frequency of the switch on the primary side and to control the regulation and driver circuit (110) on the basis of the determined switching frequency such that an IU₀U charge characteristic is adjusted.

12. Battery charger according to claim 1, wherein the charge monitoring circuit (104) comprises a temperature detection device (123) for detecting the temperature of the battery (114) and is designed so as to control the power transfer in response to the measured temperature.

13. Battery charger according to claim 2, wherein the temperature detection device (123) comprises a resistor with negative temperature coefficients (116) which is electrically isolated with respect to the battery (114).

14. Battery charger according to claim 1, wherein the charge monitoring circuit (104) comprises a time switching device (122) which terminates the power transfer after a predetermined charging period.

15. Battery charger according to claim 4, wherein the time switching device (122) comprises an oscillator circuit (126) for generating a time pulse.

16. Battery charger according to claim 4, wherein the time switching device (122) is designed so as to generate a time pulse from a mains frequency.

17. Battery charger according to claim 1, wherein the switching power supply (102) comprises a switch on the primary side and a transformer with an auxiliary winding in which, after opening the switch on the primary side, an auxiliary voltage is induced, and wherein the regulation and driver circuit (110) is designed so as to regulate the output voltage and/or the output current of the switching power supply in dependence on the induced auxiliary voltage.

18. Battery charger according to claim 1, wherein the battery charger further comprises a logic circuit (124) for storing values of the output voltage of the switching power supply as actual instant values of the battery voltage and for comparing consecutive actual values, wherein the logic circuit (124) is designed so as to terminate the charging process if the actual value is reduced during several consecutive samplings.

19. Battery charger according to claim 1, wherein the logic circuit (124) is designed so as to cause the regulation and driver circuit (110) after the termination of the charging process to transfer a small charge conservation current to the battery.

20. Battery charger according to claim 1, wherein the charge monitoring circuit (104) is designed so as to monitor the switching frequency of the switch on the primary side and to control the regulation and driver circuit (110) on the basis of the determined switching frequency such that an IU₀U charge characteristic is adjusted.

11. Battery charger for charging a battery

wherein the battery charger (100) comprises a switching power supply (102) controlled on the primary side with at least one converter connected to a switching circuit (106) on the primary side and to a switching circuit (108) on the secondary side, with a regulation and driver circuit (110) for regulating the power transferred to the secondary side (108), and a charge monitoring circuit (104) for monitoring the charge state of the battery,

wherein the charge monitoring circuit (104) is disposed in the switching circuit (106) on the primary side of the battery charger (100).