| 摘要 |
A line output circuit has a transistor (TR) whose collector is connected through the primary winding (P) of a transformer (T) to a direct voltage supply terminal (2), the secondary winding (S) of the transformer (T) being connected through a diode (D1) to a terminal (3) at which an EHT supply appears. A diode (D2) shunts the collector-emitter path of transistor (TR) to provide a path for negative going sawtooth current. Two serially connected flyback capacitors (Cf1, Cf2) also shunt the transistor (TR), one capacitor (Cf2) being shunted by a switch (S1). The series arrangement of a linearity correction inductor (L1), a deflection coil (Ly), a further inductor (L2) and a trace capacitor (Ct1) also shunt the transistor (TR), the inductor (L2) and trace capacitor (Ct1) also being shunted by the series arrangement of a further trace capacitor (Ct2), a linearity correction resistor (R) and a switch (S2). With the switches (S1, S2) in the conditions as shown the circuit operates at a high line frequency but in the conditions opposite to that shown, the circuit operates at a lower line frequency, with subsequent change to line drive pulses applied to a terminal (1). The values of the circuit components are chosen such that the ratio of the flyback period to the line period of the sawtooth current generated is the same at both line frequencies while the supply voltage to the deflection coil (Ly) is in part present across the inductor (L2) at the lower frequency to ensure the same scan current at both frequencies. This ensures that with the same supply voltage at terminal (2) the EHT supply voltage and the magnitude of the deflection current through the deflection coil (Ly) are the same at both line frequencies.
|
