| 摘要 |
An auxiliary or ballast circuit for high-frequency operation of discharge lamps (E), for example sodium high pressure discharge lamps, provides for controlled inrush or "ON current" by including a thyristor (TH1) or pair of thyristors (TH2, TH3) in the current supply path to the discharge lamp (E) integrated into a combination active filter-voltage step-up circuit. The gate of the thyristor (TH1) or a pair of thyristors (TH2, TH3) is, or are, controlled over a resistance (R2, R3, R4) connected to the output capacitor (C2) of the filter-voltage step-up circuit to fire the thyristor when input voltage goes through null, and the output capacitor (C2) has a predetermined voltage level above the input voltage. The output capacitor (C2), before firing, is charged by a charge control resistor (R1) connected in parallel across the anode-cathode path of the thyristor or thyristors. Thus, a maximum controlled inrush current is provided independent of ambient temperature or temperature of a NTC resistor and not requiring a relay.
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