Patent ID: 8400070
Filing Date: 2013-03-19
Classification: H02M,H05B

Abstract:
1. An electronic ballast for operating at least one discharge lamp, comprising an input stage and an output stage, the output stage having a first output connection and a second output connection for connecting the at least one discharge lamp, as well as a control input for varying the output power provided between the first output connection and the second output connection, the input stage being configured to provide at its output a DC operating voltage for the output stage, and comprising the following: a first input connection and a second input connection for connecting an alternating supply voltage; an EMC filter; a rectifier, the EMC filter being coupled between the first input connection and the second input connection and the rectifier; a capacitor for providing the DC operating voltage for the output stage; and a power factor correction device that is coupled between the rectifier and the capacitor, the power factor correction device comprising a number n of partial devices for power factor correction that are interconnected in parallel, as well as a control device for controlling the number n of partial devices, the power to be provided at the output of the power factor correction device being a total power currently to be provided, the power to be provided by the partial device i being a currently to be provided partial power of the partial device i; wherein the control device is configured to control at least a first and a second partial device as a function of the currently to be provided total power in such a way that their currently to be provided partial powers differ from one another, and wherein one partial device is configured for a maximum current partial power, the operating point for switching off a first or further partial device being selected as follows in the case of a reduction in the currently to be provided total power: (currently to be provided total power)/(number of active partial devices−1)=factor A*(maximum current partial power), where 0.8<=A<1.