Patent ID: 8994285
Filing Date: 2015-03-31
Classification: H05B

Abstract:
1. An electronic ballast for operating at least one discharge lamp, comprising an input having a first and a second input connection for coupling to a DC supply voltage; an output having a first and a second output connection for coupling to the at least one discharge lamp; an inverter having a bridge circuit with at least one first and one second electronic switch and a control device for controlling at least the first and the second electronic switch such that the first and the second electronic switch are alternately rendered conducting at a first frequency, wherein the first and the second switch are connected in series between the first and the second input connection, wherein the first electronic switch is coupled to the first input connection and the second electronic switch to the second input connection, wherein a first bridge midpoint is implemented between the first electronic switch and the second electronic switch; a current measuring device for measuring the current at least through the second electronic switch; a lamp choke which is connected in series between the first bridge midpoint and the first output connection; at least one trapezoidal capacitor which is connected in parallel with one of the two electronic switches; and at least one coupling capacitor for coupling the load; wherein the control device is coupled to the current measuring device and is designed to render the second electronic switch conducting a) if a predefinable negative threshold value of the current through the second electronic switch is exceeded when the first electronic switch is rendered nonconducting or b) if the predefinable negative threshold value of the current through the second electronic switch is not exceeded after the first electronic switch has been rendered nonconducting after a predefinable time; wherein the control device is configured to increase the first frequency in case b).