Battery charger circuit
First Claim
1. 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, wherein each charging section comprises a charging path that includes 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, wherein the charging path and the by-pass path each include in series therewith an electrically operable FET, and the charger further comprises control circuitry for operating the two electrically operable FETs of each charging section, whereby when the FET in one of the paths is operated to be turned on, the FET in the other of the paths is operated to be turned off, and vice versa.
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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.
33 Citations
20 Claims
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1. 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, wherein each charging section comprises a charging path that includes 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,
wherein the charging path and the by-pass path each include in series therewith an electrically operable FET, and the charger further comprises control circuitry for operating the two electrically operable FETs of each charging section, whereby when the FET in one of the paths is operated to be turned on, the FET in the other of the paths is operated to be turned off, and vice versa.
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3. 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, wherein each charging section comprises a charging path that includes 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,
wherein the charging path and the by-pass path each include in series therewith an electrically operable FET, the charger further comprising control circuitry for operating the two electrically operable FET of each charging section, whereby the control circuitry is operative for (a) the FET in the charging path of a charging section to be conductive whilst the FET 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 when said battery is not fully charged, and (b) the FET in the charging path of a charging section to be non-conductive whilst the FET in the by-pass path of that charging section is conductive for the charging current to by-pass a battery in that charging section when said battery is fully charged.
- 11. A battery charger including a plurality of battery charging sections which are connected in series and a charging current source, wherein said charging section includes at least a first branch and a second branch which are connected in parallel, said first parallel branch includes an electronically controllable bypassing switch, said second parallel branch includes terminals for receiving the positive and negative terminals of a battery and a charging switch which are connected in series, said bypassing switch has a very low impedance when activated or turned-on and a very high impedance when deactivated or turned-off, said charging switch is characterized by a very low-impedance when current flows from said charging section into said battery terminals and a high-impedance when said bypassing switch is activated, said charging switch allows charging current to flow into said battery but substantially prevents discharge of said battery through said charging switch, and wherein both said bypassing switch and said charging switch are FETs.
Specification