BATTERY CHARGER CIRCUIT

• US 20040217734A1
• Filed: 04/30/2003
• Published: 11/04/2004
• Est. Priority Date: 04/30/2003
• Status: Abandoned Application

• Current Assignee: Jeckson Electric Company Limited (China Aerospace International Holdings Limited)
• Original Assignee: Jeckson Electric Company Limited (China Aerospace International Holdings Limited)
• Inventors: Shum, King Mo
• Application Number:
  US10/426,215
• Publication Number:
  US 20040217734A1
• Time in Patent Office: Days
• US Class Current: 320/116
• CPC Class Codes: H02J 7/0016 using shunting, discharge or bypass circuits

Abstract

A battery charger having a plurality of series connected sections for serially charging a plurality of rechargeable batteries, for example rechargeable batteries of AA or AAA size. Each charging section includes a charging path for a battery and a parallel bypass path for bypassing a battery when it is fully charged. The charging path and the bypass path of each charging section each include an electrically operable switching device, which devices are preferably MOSFETs. Control circuitry is included to ensure one switching device is off when the other is on. MOSFET switching devices are connected into the circuit in directions to ensure they are not burnt out by the charging currents. A discharge circuit may be included for the batteries to discharge briefly between pulses of charging current thereby providing for “negative pulse charging” of the batteries. The charger provides for improved efficiency of charging in that very little power is consumed by the switching devices in the charging paths.

Claims

1-12. -12. (cancelled)

13. A battery charger having a plurality of series connected charging sections for charging a plurality of rechargeable batteries, each charging section including contacts for contacting the terminals of a battery to be charged,

the charger including a constant current source that is switchable on and off for providing a charging current in pulses, each charging section comprising

(i) a charging path that includes the contacts and a first MOSFET which is connected for the charging current to flow through it in a direction that corresponds to the forward direction of its internal diode and through a battery,

(ii) a by-pass path that includes a second MOSFET which is connected for the charging current to flow through it in a direction that corresponds to the reverse direction of its internal diode, the charger further comprising a discharge path including a switch for opening and closing the discharge path,

and control circuitry for switching the constant current source on and off, for rendering the first and second MOSFETs of each charging section conductive or non-conductive, and for opening and closing the switch of the discharge path,

whereby for charging a battery in a charging section, the first MOSFET of that charging section is rendered conductive and the second MOSFET non-conductive for the charging current to flow through the charging path and not the by-pass path and, during each off period of the pulsed charging current during which period the switch of the discharge path is closed, for a discharge current to flow from the battery to the first MOSFET and through the discharge path, thereby providing negative pulse charging of the battery.

14. The battery charger as claimed in claim 13 wherein the control circuitry provides for any one of the charging sections of the plurality of series connected charging sections to be by-passed by the charging current by rendering the first MOSFET of that charging section non-conductive and the second MOSFET conductive, and wherein the discharge path is structured to include the second MOSFET of a charging section in which the charging current by-passes the battery.

15. The battery charger as claimed in claim 13 wherein the first MOSFET is an N-channel MOSFET and the charging current flows through it in the source to drain direction, and wherein the second MOSFET is an N-channel MOSFET and the charging current flows through it in the drain to source direction.

16. A battery charger having a plurality of series connected charging sections for charging a plurality of rechargeable batteries, wherein each charging section comprises a charging path for a charging current to flow through a battery connected into the charging path, and

a by-pass path for the charging current to by-pass the charging path when a battery connected therein is fully charged,

wherein the charger further includes a discharge path for a discharge current to flow from the plurality of batteries upon cessation of the charging current,

wherein the charging path of each charging section includes an N-channel MOSFET connected such that the charging current flows through the MOSFET from its source terminal to its drain terminal,

wherein the by-pass path of each charging section includes an N-channel MOSFET connected such that the by-passed charging current flows through the MOSFET from its drain terminal to its source terminal,

wherein the charger further includes control circuitry for controlling a voltage applied to the gate terminal of each MOSFET such that when one MOSFET is conductive the other is non-conductive,

whereby

(i) for a battery connected into a charging section and undergoing charging, the MOSFET in the charging path of that charging section is conductive whilst the MOSFET in the by-pass path is non-conductive and, upon cessation of the charging current, the discharge path includes the conductive MOSFET in the charging path of that charging section, and

(ii) for a battery connected into a charging section and fully charged, the MOSFET in the charging path of that charging section is non-conductive whilst the MOSFET in the by-pass path is conductive and, upon cessation of the charging current, the discharge path includes the conductive MOSFET in the by-pass path of that charging section.

17. The battery charger as claimed in claim 16 wherein the charger includes constant current source for providing the charging current and is switchable on and off via the control circuitry, and the discharge path includes a switch for opening and closing the discharge path via the control circuitry, wherein the control circuitry is operable such that when the constant current source is switched off, the switch of the discharge path is closed for a discharge current to flow until the constant current source is switched on accompanied by the switch of the discharge path being opened.

18. A battery charger, comprising:

a plurality of series connected charging sections for charging a plurality of rechargeable batteries, each charging section including contacts for contacting the terminals of a battery to be charged, each charging section including a charging path having the contacts for passage of a charging current through a battery and a by-pass path for the charging current to by-pass the charging path, the charging path and the by-pass path each having in series therewith an electrically operable switching device;

control circuitry for operating the two electrically operable switching devices of each charging section; and

a discharge circuit that can be opened or closed via the control circuitry, wherein;

the control circuitry is operative for the switching device in the charging path of a charging section to be conductive whilst the switching device in the by-pass path of that charging section is non-conductive for passage of the charging current through a battery in the charging path and not through the by-pass path and to prevent any discharge current from the battery from flowing through the by-pass path upon cessation of the charging current,

the control circuitry is operative for the switching device in the charging path of a charging section to be non-conductive whilst the switching device in the by-pass path of that charging section is conductive for the charging current to by-pass a battery in that charging section that is fully charged, and

the discharge circuit may be closed by the control circuitry such that a discharge current is permitted to flow from the battery through the switching device of that charging section and through the discharge circuit when the switching device in the charging path of a charging section is conductive, the switching device in the by-pass path of that charging section is non-conductive, and the charging current ceases.