| 摘要 |
1,121,527. Supply systems for space discharge lamps. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 10 Aug., 1965 [13 Aug., 1964], No. 34186/65. Headings H2F and H2H. [Also in Division H3] A driven inverter of the type in which an output tuned circuit is periodically energized through a thyristor and in which the load comprises discharge tubes or another load which slowly decreases in resistance when the inverter is switched on, comprises a delay element to cause the frequency of the drive to rise to its operating value more slowly than the load resistance decreases. The initial operation at the lower frequency causes the load voltage to be less. The driving oscillator may be of the Colpilts type (Fig. 3, not shown), with its tuning capacitor (49) connected in series with a lamp (50) which renders the capacitor less effective as the lamp warms up. Alternatively, the oscillator may be a multivibrator with thermistors connected in series with the timing resistors. In Fig. 5 the driving oscillator comprises a capacitor 73 charged through timing resistors 74, 75 and 76 and periodically discharged through a blocking oscillator 80, the resulting output being fed to the inverter output stage through an amplifier 90. A time constant circuit 78, 79 renders a transistor 77 conducting after a delay and this short circuits timing resistor 75 to increase the frequency. The Specification describes a push-pull freerunning inverter also having a frequency delay arrangement, but which by omission of the feedback elements is suitable for use as the output stage of a driven inverter in accordance with the invertion. This inverter (Fig. 1) is basically similar to those described in Specifications 978,787 and 1,064,754 and comprises a series tuned circuit consisting of inductor 21 and the capacitive reactance of a parallel tuned output 3, 18. The operating frequency is determined by a feedback circuit comprising a series tuned circuit 22, 23 and a saturating transformer 24, the circuit being shunted by a tuning capacitor 19 in series with a lamp 20. On switching on the inverter the resistance of the lamp rises as the lamp heats up and so the oscillation frequency rises. |
