Solid State Chargers Research and Development Limited Partnership

Other

Solid State Charger Research and Development

Philip A Hoffman

A current pulse producing, current regulating circuit includes a SCR arranged to pass a current pulse once each positive going half wave input supplied thereto. The SCR is controlled by a control circuit free of current feedback and timing circuitry and responsive to the an unfiltered, rectified A.C. input. The control circuit produces a firing signal, which is applied to the control electrode of the SCR, at a point during the downward swing of each positive going half wave input. The control circuit includes a OR function circuit responsive to the unfiltered rectified input applied to the control circuit and to an output from a circuit also responsive to the unfiltered rectified input; the last mentioned circuit having a hysteresis characteristic. The SCR may be operatively associated with a second SCR and arranged to fire it thereby producing higher amplitude current pulses. Battery charging and forming circuits, as well as off-line power supplies, incorporating the current regulating circuit are disclosed. The input to the control circuit may be either a full wave or a half wave rectified A.C. input. Batteries of different types and having different numbers of cells can be accomodated.

Current regulating circuit

A battery charger which includes terminals for connection to an electric power source, an electrical charging circuit and an operative arrangement for connecting at least one rechargeable battery cell in series with the charging circuit across the terminals. The battery charger has a charging circuit which includes a first resistor, a second resistor, a third resistor and a rectifier, constituted by at least one diode, in series. A first transistor, which has a collector-emitter path and a base-emitter path, is operatively connected so that the base-emitter path is connected in parallel with the first resistor. A fourth resistor is provided, the fourth resistor being connected in series with the collector-emitter path of the transistor and the third resistor. In one species, a plurality of additional transistors, connected in Darlington configuration, includes a second transistor and a final transistor, each of the additional transistors having its collector connected to a circuit point between the third resistor and an electrode of the diode. The first transistor and the last transistor in the one species have their emitters connected via a current-limiting PTC fifth resistor which may act as a fuse. The first transistor and the second transistor have their respective collector and base conductively connected. In another species, a field effect transistor, preferably a MOSFET, is used instead of the Darlington configuration. The connection of the third resistor provides internal feedback. The fifth resistor, when in series with the first resistor in the base-emitter circuit, provides external feedback.

A power supply which includes terminals for connection to an electric power source, a storage capacitance, an electrical charging circuit and an operative arrangement for connecting storage capacitance in series with the charging circuit across the terminals. The power supply has a charging circuit which includes a first resistor, a second resistor, a third resistor and a rectifier, constituted by at least one diode, in series. A first transistor, which has a collector-emitter path and a base-emitter path, is operatively connected so that the base-emitter path is connected in parallel with the first resistor. A fourth resistor is provided, the fourth resistor being connected in series with the collector-emitter path of the transistor and the third resistor. In one embodiment, a plurality of additional transistors, connected in Darlington configuration, includes a second transistor and a final transistor, each of the additional transistors having its collector connected to a circuit point between the third resistor and an electrode of the diode. The first transistor and the last transistor have their emitters connected via a current-limiting PTC fifth resistor which may act as a fuse. The first transistor and the second transistor have their respective collector and base conductively connected. The connection of the third resistor provides internal feedback. The fifth resistor, when in series with the first resistor in the base-emitter circuit, provides external feedback. A field-effect transistor, preferably a MOSFET, can replace the Darlington configuration.

Power supply with current regulating circuit

A power supply which includes terminals for connection to an electric power source, a storage capacitance, an electrical charging circuit and an operative arrangement for connecting the storage capacitance in series with the charging circuit across the terminals. The power supply has a charging circuit which includes a first resistor, a second resistor, a third resistor and a rectifier, constituted by at least one diode, in series. A control stage includes a first transistor, which has a collector-emitter path and a base-emitter path. The transistor is operatively connected so that the base-emitter path is connected in parallel with the first resistor. A fourth resistor is provided, the fourth resistor being connected in series with the collector-emitter path of the transistor and the third resistor. In one embodiment, the charging current carrying stage includes a plurality of additional transistors, connected in Darlington configuration, which are controlled by the first transistor which is operatively arranged to be controlled by a signal which corresponds to the D.C. voltage output and is produced by a D.C. voltage sensing circuit and responds to the unfiltered output from the rectifier. An optical coupler is connected between the D.C. output voltage sensing circuit, which may be a Schmidt trigger, and the control stage. A field-effect transistor, preferably a MOSFET, can replace the plurality of transistors in the Darlington configuration.

Regulated power supply with current regulating circuit

A battery charger which includes terminals for connection to an electric power source, an electrical charging circuit and an operative arrangement for connecting at least one rechargeable battery cell in series with the charging circuit across the terminals. The battery charger has a charging circuit which includes a first resistor, a second resistor, a third resistor and a rectifier, constituted by at least one diode, in series. A first transistor, which has a collector-emitter path and a base-emitter path, is operatively connected so that the base-emitter path is connected in parallel with the first resistor. A fourth resistor is provided, the fourth resistor being connected in series with the collector-emitter path of the transistor and the third resistor. A plurality of additional transistors, connected in Darlington configuration, includes a second transistor and a final transistor, each of the additional transistors having its collector connected to a circuit point between the third resistor and an electrode of the diode. The first transistor and the last transistor have their emitters connected via a current-limiting PTC fifth resistor which may act as a fuse. The first transistor and the second transistor have their respective collector and base conductively connected. The connection of the third resistor provides internal feedback. The fifth resistor, when in series with the first resistor in the base-emitter circuit, provides external feedback.

Disclosed is a battery operated hand tool which has incorporated directly into its housing a novel battery charging circuit. The charger normally operates off a conventional household power outlet and comprises a solid state switching circuit for recharging the battery with a series of electrical impulses. In some special cases, it can be operated in a non-switching state. External inductance is eliminated by charging the battery through the hand tool motor.

Battery charging circuit

Disclosed is an improved circuit for recharging batteries. It can be used with alternating current power sources having a wide range of voltage and frequencies and also with low voltage direct current power sources. A transistor switch is connected in a feedback circuit to have, in effect, a variable resistance such that the charging current is high when the source potential is low and decreases to zero as the source potential increases. Charging efficiency is thereby significantly increased.

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Towson, MD, United States of America

Philip A Hoffman