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Circuit arrangement for deriving a direct voltage from the mains alternating voltage

  • US 4,959,556 A
  • Filed: 02/02/1989
  • Issued: 09/25/1990
  • Est. Priority Date: 02/05/1988
  • Status: Expired due to Fees
First Claim
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1. A circuit arrangement for deriving a direct voltage from an alternating voltage, said circuit arrangement comprising:

  • two input terminals,two output terminals one of which is connected to one of the input terminals,a switching transistor whose main current path is connected between the other input terminal and the other output terminal,a control circuit for controlling the switching transistor, which control circuit includes a thyristor which is connected via a first resistor between the two input terminals, a node between the first resistor and thyristor being connected to a control electrode of the switching transistor, anda time-determining circuit comprising a series arrangement of a second resistor capacitor and a trigger element connected between a gate terminal of the thyristor and a node between said second resistor and capacitor, characterized in that the trigger element comprises a diac, in that the other input terminal is connected to an alternating voltage terminal via a rectifier diode arranged in the forward direction with the main current path of the switching transistor, in that the series arrangement of second resistor and capacitor is connected between the alternating voltage terminal and the one input terminal and in that a diode is coupled across the capacitor in such a way that said diode conducts during the periods when the rectifier diode is blocked.

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