An apparatus and methods for balancing current in multiple negative
impedance gas discharge lamp loads. Embodiments advantageously include
balancing transformer configurations that are relatively cost-effective,
reliable, and efficient. Embodiments include configurations that are
applicable to an unrestrained number of gas discharge tubes, such as cold
cathode fluorescent lamps. The balancing transformer configuration
techniques permit a relatively small number of power inverters, such as
one power inverter, to power multiple paralleled lamps or paralleled
groups of lamps with balancing transformers coupling the lamps or groups
of lamps in a zigzag topology. One embodiment of a balancing transformer
includes a safety winding which can be used to protect the balancing
transformer in the event of a lamp failure and can be used to provide an
indication of a failed lamp.