General Electric Company

A123 Systems LLC

Thomas Farkas

Emad Andarawis Andarawis

Naresh Kesavan Rao

George A Farrall

C Michael Hoff

Timothy A Taubert

Gordon Alexander Grigor

David O Wharmby

Peter Gottlieb

A battery system comprises a first battery unit; a DC voltage bus; a second battery unit electrically connected to the DC voltage bus; a current-limiting component; and switching circuitry for connecting the first battery unit to the DC voltage bus, where the switching circuitry is configured to electrically connect the first battery unit to the DC voltage bus either directly or through a current-limiting component, depending on an operating parameter of the first battery unit.

Battery balancing system

A sensing circuit for a triac dimmable gas discharge lamp ballast uses the duty cycle of the output waveform of a conventional triac dimmer as the parameter representing a set point for controlling the degree of clamping applied to the ballast circuit, and thus the amount of light produced by a fluorescent lamp. The sensing circuit may include a comparator that receives a rectified output waveform of a triac dimmer and produces output pulses corresponding in width to the duty cycle of the waveform, and a capacitor averaging the values of the pulses produced by the comparator to produce a set point signal representing a dimming level of the lamp. A triac dimmable ballast circuit using this sensing circuit has reduced sensitivity to line voltage and a wide mechanical range over which the light level of the fluorescent lamp is controlled by the user. The sensing circuit also enables a preheat timing circuit that eliminates the timing capacitor of prior art preheating circuits. A gas discharge lamp ballast and a method for its operation are also disclosed.

Sensing and control for dimmable electronic ballast

A ballast includes a resonant load circuit having a resonant inductance and a resonant capacitance. The load circuit couples a.c. current to a gas discharge lamp. A self-oscillating complementary converter circuit of the ballast induces a.c. current in the resonant load circuit. The converter circuit includes a pair of switches serially connected between a d.c. voltage bus and a reference bus. Respective reference nodes of the switches are interconnected at a common node through which the induced a.c. current flows, and respective control nodes of the switches are substantially directly interconnected. A gate drive circuit controls the switches. The gate drive circuit includes a drive winding connected to the control nodes. The drive winding is mutually coupled to the resonant inductance for sensing current therein, and an inductor is serially connected to the drive winding and to the common node. A clamping circuit is directly coupled across terminals of the inductor of the gate drive circuit and controls voltage across the inductor in response to an error signal. The error signal represents the difference between a user-selectable signal and a feedback signal that represents a time-averaged value of a lamp operating parameter. The ballast circuit of the invention allows a user to adjust the output of the lamp while it operates. The ballast circuit improves over conventional ballast circuits by eliminating a bulky mutually coupled winding, thereby reducing ballast mass and volume.

Self-oscillating dimmable gas discharge lamp ballast

An electrodeless gas discharge lamp includes a vitreous envelope containing a discharge medium. An excitation coil is positioned in relation to the vitreous envelope so as to excite the discharge medium therein. The excitation coil is adapted to be driven by an RF oscillator. The excitation coil has first and second ends and is effective for exciting the discharge medium to emit light with electromagnetic fields that are generated by the excitation coil. The excitation coil includes a first wire wound generally helically from the first end to the second end in a first helical direction to form first winding turns, and further includes a second wire wound generally helically from the first end to the second end in second helical direction opposite to that of the first helical direction to form second winding turns. Preferably, a generally cylindrical former is provided for holding the first and second wires between the first and second ends of the coil. Such former includes a positioning arrangement for maintaining specific positions of the first and second wires with respect to each other along the former.

Growing community of inventors

Marlborough, MA, United States of America

Thomas Farkas