DEFLECTION SUPPLY VOLTAGE FEEDBACK CONTROL IN CONJUNCTION WITH FREQUENCY CHANGE

摘要

A video display (10) includes a scanner (100) operable at a first frequency (H1) and a higher second frequency (H2). A switchmode power supply (SMPS) (32) drives a transformer (T1) with three secondaries (T1S1b, T1S1a and T1S2). First and second rectifiers & filters ((CR107, CR108) and (F101, F102)) are associated with the first and second secondaries. A rectifier is coupled to the third secondary (T1S1b) and by way of a switch (K2) to the first filter (F101). Feedback from the first filter (F101) controls the SMPS (32). In a first operating mode, the scanner (100) is operated at the first frequency, the switch is open, the scanner supply (SCAN +) is a first voltage from the first filter (F101), and ancillary equipment is supplied with a third voltage by the second filter (F102). In a second operating mode, the scanner (100) is operated at the second frequency, the switch (K2) is closed, the scanner supply (SCANB +) is a second voltage, higher than the first, from the first filter (F101), and ancillary equipment is supplied with the same third voltage.