Patent ID: 8134301
Filing Date: 2012-03-13
Classification: H02M,H05B

Abstract:
1. An electronic ballast for a discharge lamp with a step-up converter, which has a storage inductor, a diode, an intermediate circuit capacitor and a switching element, wherein: the electronic ballast is designed to switch off the switching element in the step-up converter when a maximum current value of the current flowing through the switching element is reached, and wherein the electronic ballast has a hold circuit with a timing element, which hold circuit is designed to set the timing element when the switching element is switched off, and to switch on the switching element if a time determined by the timing element has elapsed, wherein the hold circuit has: a threshold value element for switching the switching element and for setting the timing element, with a signal, which corresponds to the current through the switching element, being supplied to a control input of the threshold value element, and with the hold circuit being designed to switch off the switching element via the threshold value element when the maximum current through the switching element, which current is determined by the threshold value of the threshold value element, is reached and to set the timing element via the threshold value element wherein the hold circuit has: a hold switch, a first voltage divider with two impedances, whose center tap is connected to the control input of the threshold value element, with the switching path of the hold switch and the voltage divider being connected in series, with the hold circuit being designed to switch on the hold switch via the threshold value element when the maximum current through the switching element is reached, with the result that a current flows through the first voltage divider, and the potential at the control input of the threshold value element being set via the center tap of the first voltage divider in such a way that the switching element remains switched off.