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Circuit arrangement for operating at least a first and a second cascade of LEDs

  • US 10,098,195 B2
  • Filed: 09/10/2015
  • Issued: 10/09/2018
  • Est. Priority Date: 09/17/2014
  • Status: Active Grant
First Claim
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1. A circuit arrangement for operating at least a first and a second cascade of LEDs comprising:

  • an input having a first and a second input connection for coupling to a rectified AC supply voltage;

    a voltage equalization series impedance; and

    at least a first higher and a second lower LED unit, wherein the first LED unit comprises the first cascade of LEDs and the second LED unit comprises the second cascade of LEDs;

    wherein each LED unit further comprises;

    a first diode coupled in series with the respective LED cascade, wherein the coupling point between the first diode and the respective LED cascade is a first node, wherein that connection of the LED cascade that is not coupled to the first diode is a second node, wherein that connection of the first diode that is not coupled to the LED cascade is a third node;

    the series connection of a first capacitor and a second diode, which is coupled between the third node and a fourth node of the circuit arrangement, wherein the coupling point between the first capacitor and the second diode is a fifth node, the anode of the second diode being coupled to the fifth node; and

    a first and a second electronic switch each having a control electrode, a reference-ground electrode and a main electrode, wherein the control electrode of the first electronic switch is coupled to a sixth node, wherein the reference-ground electrode of the first electronic switch is coupled to the fifth node, wherein the main electrode of the first electronic switch is coupled to the control electrode of the second electronic switch, wherein the reference-ground electrode of the second electronic switch is coupled to the third node, wherein the main electrode of the second electronic switch is coupled to the second node;

    wherein the third node of the highest LED unit is coupled to the first input connection, wherein the second node of the lowest LED unit is coupled to the voltage equalization series impedance such that the voltage equalization series impedance is coupled in series between the second node of the lowest LED unit and the second input connection;

    wherein the third node of a respective LED unit that is not the highest LED unit is coupled to the second node of the next highest LED unit;

    wherein the sixth nodes of all LED units are coupled to a DC voltage source;

    wherein in the LED units that are not the lowest LED unit, the fourth node is at any rate a node of the circuit arrangement that is at a lower potential, at least during a prescribable period during the operation of the circuit arrangement, than the respective second node of the respective LED unit.

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