Programmed start circuit for ballast

摘要

A programmed start ballast circuit is presented having a mode control circuit to selectively switch an inverter output load to control operation for cathode preheating, step dimming and/or anti-arcing operation.

主权项

1. A programmed start ballast circuit for powering at least one light source, the ballast circuit comprising:
a DC circuit operative to provide a DC output at first and second DC output terminals; an inverter circuit operatively coupled to the DC circuit to convert the DC output to produce an AC output to power at least one light source, the inverter comprising:
a first capacitance and a second capacitance coupled in series between the first and second DC output terminals and joined with one another at a first intermediate node,a first switching device and a second switching device coupled in series between the first and second DC output terminals and joined with one another at a second intermediate node, anda first transformer with a first primary winding coupled between the second intermediate node and a third intermediate node; a second transformer with a second primary winding coupled between the first and third intermediate nodes; and a mode control circuit operative in a first mode to selectively couple the third intermediate node with one of the first and second DC output terminals to reduce a voltage potential across the second primary winding, and in a second mode to disconnect the third intermediate node from the second DC output terminal.