| 摘要 |
A signal generating circuit for ballast control of discharge lamps. A ballast control apparatus for an electric discharge lamp (1) comprises a first series circuit including a first winding (5) of an Ac supply voltage transformer (4), a first winding (7) of a ballast transformer (8), a lamp current sensing resistor (11) and the lamp (1). A current sensing transformer (13) has a first winding (12) parallel to the resistor (11). A second winding (16, 9, 14) of the supply voltage transformer (4), the ballast transformer (8) and the current sensing transformer (13) are connected in a second series circuit. A signal voltage proportional to lamp power is derived by adding together the voltages included in the three series-connected second windings (9, 16, 14). A second signal voltage proportional to lamp voltage is derived across the series combination of the second windings (9, 16) of the ballast transformer (8) and the supply voltage transformer (4). The voltage induced in the second winding (14) of the current sensing transformer (13) is proportional to lamp current. A signal voltage indicative of the condition of the lamp load can be derived across the second winding (9) of the ballast transformer (8). These three signal voltages are used to control a DC/AC inverter (2) that energizes the lamp (1) via the supply voltage transformer (4). Fig. 1. |
