Universal battery charger

• US 5,270,635 A
• Filed: 02/14/1992
• Issued: 12/14/1993
• Est. Priority Date: 04/11/1989
• Status: Expired due to Fees

• Current Assignee: Solid State Chargers Incorporated
• Original Assignee: Solid State Chargers Incorporated
• Inventors: Frey, Douglas R., Hoffman, Philip K.
• Primary Examiner(s): HICKEY, ROBERT
• Application Number:
  US07/838,853
• Time in Patent Office: 669 Days
• Field of Search: 320/21, 320/18, 320/57, 320/59
• US Class Current: 320/122
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 7/02 for charging batteries from ac mains by converters

Abstract

A battery charger of the driven blocking oscillator type includes a three-winding transformer. The primary winding is connected in series with the collector-emitter path of a switching transistor. The secondary winding is connected in series with the collector-emitter path of a sense transistor which responds to the current flowing through the switching transistor. The tertiary winding is connected in series with the battery, series-connected batteries or series-connected battery packs sought to be recharged, via a diode, which may be connected in parallel with a capacitor. No smoothing capacitor is provided across the battery or batteries. The battery or batteries are charged by current pulses and discharge through the tertiary winding to repolarize the diode (and capacitor if present). The secondary winding is poled, with respect to the tertiary winding so that the blocking oscillator is driven by energy from the battery or batteries. The battery charger can operate over a wide range of input voltages with high efficiency, making it useful worldwide. The charger is effective to charge batteries and series connections thereof over a wide range of battery voltages. The charger will only function if at least one rechargeable battery is in circuit for charging. The charger may include circuitry for automatically taking substantially charged batteries or battery out of the charge path.

Claims

1. A battery charger for charging a plurality of batteries defining part of a charging path and connected in series with a source of charging current, the charger comprising means for delivering charging current pulses to the plurality of batteries via the charging current path, and respective means responsive to respective terminal voltages of respective ones of the batteries for removing individual ones of the batteries from the charging current path whenever said individual ones of the batteries is or becomes substantially fully charged, wherein said means for delivering charging current pulses to the batteries includes a common transformer winding and respective diodes connected in series with respective ones of the batteries and respective capacitors connected in parallel with said respective diodes.

2. The battery charger according to claim 1, wherein said means for delivering charging current comprises a blocking oscillator.

3. The battery charger according to claim 2, wherein said blocking oscillator is of the driven type.

4. the battery charger according to claim 1, wherein the circuits across the individual batteries are free of any smoothing capacitor.

5. A battery charger for charging a plurality of batteries defining part of a charging path and connected in series with a source of charging current, the charger comprising means for delivering charging current pulses to the plurality of batteries via the charging current path, and respective means responsive to respective terminal voltages of respective ones of the batteries for removing individual ones of the batteries from the charging current path whenever said individual ones of the batteries is or becomes substantially fully charged, and wherein said means for delivering charging current pulses to the batteries includes a common transformer winding and respective diodes connected in series with respective ones of the batteries.

6. The battery charger according to claim 5, wherein said means for delivering charging current comprises a blocking oscillator.

7. The battery charger according to claim 5, wherein said blocking oscillator is of the driven type.

8. The battery charger according to claim 5, wherein the circuits across the individual batteries are free of any smoothing capacitor.