Electronic ballast and method for operating at least one discharge lamp

An electronic ballast for operating at least one discharge lamp, the electronic ballast comprising:

• an input with a first and a second input connection for coupling to an input voltage;
• a load circuit with an output that comprises a first and a second output connection for coupling to the at least one discharge lamp, the load circuit comprising a bridge circuit with at least a first and a second bridge switch;
• an intermediate circuit capacitor that is coupled to the input of the load circuit, the voltage dropping across the intermediate Circuit capacitor during operation representing the intermediate circuit voltage;
• a transformer that is coupled between the input of the electronic ballast and the intermediate circuit capacitor, the transformer comprising at least one transformer switch;
• a control apparatus for driving the transformer switch and at least the first and the second bridge switch;
• and
• a monitoring apparatus for monitoring at least one value correlated with the input voltage, the monitoring apparatus being coupled to the control apparatus, and the control apparatus being designed to deactivate the driving of the transformer switch upon detection of a deactivation criterion;
• and
• a voltage measuring apparatus for measuring the intermediate circuit voltage, the voltage measuring apparatus being coupled to the control apparatus, the control apparatus being designed to reactivate the driving of the transformer switch after a deactivation phase when the sum of input and intermediate circuit voltage has dropped below a first prescribable threshold value,
• wherein the transformer is an single-ended primary-inductor converter (SEPIC) transformer.