Electronic ballast and operating method for a gas discharge lamp

摘要

In an electronic ballast the output d.c. voltage (U) of a PFC intermediate circuit ( 3 ) is to be regulated. The intermediate circuit ( 3 ) has a clocked switch (S) which is controlled by a regulation circuit ( 7 ). The regulation circuit ( 7 ) includes two counters (Z 1 , Z 2 ). The counter (Z 1 ) has a greater number of count stages than the counter (Z 2 ). The counter (Z 1 ) is counted upwards or downwards in dependence upon the regulation difference. The counter (Z 2 ) is repeatedly counted only in one direction and for example reset by a reset signal. By comparing the counts of corresponding count stages of the two counters (Z 1 ) and (Z 2 ) in a comparator, the switch on time (t_on) for the clock switch (S) is determined.