| 摘要 |
1471150 Transistor oscillators THORN ELECTRICAL INDUSTRIES Ltd 18 June 1974 [30 July 1973] 36200/73 Heading H3T [Also in Division H2] In a transistor class C tuned transformer feedback oscillator having a biasing capacitor 19 for the input electrode of a transistor 11, a circuit path 81, 82 is connected to a winding 80 which is coupled to an inductor 20 of a parallel resonant circuit 13 of the tuned transformer such that in operation the circuit 81, 82 provides a potential source of lower voltage than a terminal 14 to which the parallel resonant circuit is connected for discharging the bias capacitor 19 when the transistor 11 is in its non-conductive condition. The oscillator operates similar to Specification 1,308,284. The discharge from capacitor 19 is primarily through resistor 82, diode 81 and auxiliary winding 80 and only to a small extent through resistor 26. The auxiliary winding 80 and diode 81 provide an auxiliary positive rail of lower voltage than the terminal 14 which permits the capacitor 19 to discharge during alternate half cycles without excessive power dissipation. The rate of discharge is set by selecting the value of R82. In a modification (Fig. 2, not shown) a single winding (18a) is used in place of the feedback and auxiliary windings 18, 80, and the positive supply for discharging the biasing capacitor (19a) is provided by a diode (81a) which charges a storage capacitor (84). This discharge rate is adjusted by appropriate selection of the value of a resistor (83). In a further modification (Fig. 3 of the provisional Specification not shown) the lower end of auxiliary winding 80 is connected to 16 via a further winding (86) of the transformer 23. A transformer (Fig. 4, of the provisional Specification not shown) is constructed to provide leakage inductance between a winding section (A) containing windings 20, 18, 80 and a winding section (B) containing windings 24, 24a, 24b and (86) which takes the place of a ballast in a lamp circuit to limit the current through the discharge lamp 60. Windings 80 and (86) are connected in phase opposition so that in the pre-strike interval the discharge voltage across the capacitor 19 is reduced. When the lamp strikes the frequency of the oscillator increases and the output voltage of winding 86 falls to one third of its pre-strike value and the net discharge voltage for capacitor 19 is increased to maintain correct phasing at increased frequency. |
