Abstract: 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 (Z1, Z2). The counter (Z1) has a greater number of count stages than the counter (Z2). The counter (Z1) is counted upwards or downwards in dependence upon the regulation difference. The counter (Z2) 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 (Z1) and (Z2) in a comparator, the switch on time (ton) for the clock switch (S) is determined.

Abstract: 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 (Z1, Z2). The counter (Z1) has a greater number of count stages than the counter (Z2). The counter (Z1) is counted upwards or downwards in dependence upon the regulation difference. The counter (Z2) is repeatedly counted only in one direction and for example reset by means of a reset signal. By means of comparison the counts of corresponding count stages of the two counters (Z1) and (Z2) in a comparator, the switch on time (ton) for the clock switch (S) is determined.

Abstract: An electronic ballast for at least one gas discharge lamp (LA) comprises a rectifier circuit (2) connectable to an a.c. voltage source (U0), a smoothing circuit (3), connected to the output of the rectifier circuit (2), for generating an intermediate circuit voltage (Uz), and an inverter (4) fed with the intermediate circuit voltage (Uz), at the output of which inverter a connection for the load circuit (5) containing the lamp (LA) is connected. The smoothing circuit (3) is constituted by a switching regulator and the ballast further has a control circuit (6) which detects the intermediate circuit voltage (Uz) and controls a controllable switch (S1) of the switching regulator in dependence upon the value of the intermediate circuit voltage (Uz).

Abstract: An electronic ballast for at least one gas discharge lamp (LA) comprises a rectifier circuit (2) connectable to an a.c. voltage source (Uo), a smoothing circuit (3), connected to the output of the rectifier circuit (2), for generating an intermediate circuit voltage (Uz), and an inverter (4) fed with the intermediate circuit voltage (Uz), at the output of which inverter a connection for the load circuit (5) containing the lamp (LA) is connected. The smoothing circuit (3) is constituted by a switching regulator and the ballast further has a control circuit (6) which detects the intermediate circuit voltage (Uz) and controls a controllable switch (S1) of the switching regulator in dependence upon the value of the intermediate circuit voltage (Uz).