US 5,317,497 AGranted

Internally excited, controlled transformer saturation, inverter circuitry

AssigneeLoctite Luminescent Systems, Inc.

InventorRonald E. Belek

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Abstract

An inverter circuit for providing an AC driver voltage for a capacitive load from a DC input voltage. The circuit uses a pair of balanced transistors supplying a split primary winding of a transformer, a feedback winding thereof being coupled thereto to supply a feedback signal to the transistor inputs. Resistors are used to optimize inverter efficiency by adjusting transformer saturation and the DC bias of the drive transistors. A capacitor is connected across the two primaries to provide harmonic suppression an aid in starting the inverter. A second capacitor, connected from base to collector of the transistors opposite the transistor with DC bias being introduced, provides suppression of undesirable high frequencies which will occur if this capacitor is not present. The AC output is supplied from the secondary winding of the transformer.

Claims9

Dependent claims

An inverter circuit for providing a low harmonic content AC output driver voltage for an electroluminescent lamp, from a DC voltage source, said inverter circuit comprising

a transformer saturation control circuit which includes
means for controlling a DC and an AC feedback drive to a pair of balanced transistors having input and output electrodes;
a transformer having
a split primary winding having a first capacitance connected across said primary winding and connected to the output electrodes of said transistors;
a feedback winding coupled to said primary winding for supplying said AC feedback drive to the input electrodes of said transistors;
and
an output secondary winding coupled to said primary winding for providing an AC output driver voltage to said electroluminescent lamp;
and
a second capacitance connected between the input and output electrodes of one of said transistors;
said transformer saturation control circuit thereby suppressing the harmonic content of the AC output driver voltage.

7 more elements

Dependencies are inferred from the claim text.