Method for producing a turn-on enable signal

摘要

In order that the input voltage and output voltage (U1, U2; U5) of a converter (5) having standardised appliances (3, 4; 6) can be measured and evaluation electronics (19) can be made available at low potential, a control error signal (U0) and, except during a calibration process, an enable threshold value signal (UF) are used in the comparison of this input voltage and output voltage. For this purpose, input AC voltages (U2, U1), which are detected using AC voltage measurement transformers (3, 4), are fed via rectifiers (12, 11) and a multiplexer (15), which is controlled by a microprocessor (19), to a comparator (17) and are compared there with a converter DC voltage signal (U6) which has been detected by a DC measurement converter (6). Before the comparison, the control error signal (U0) and the enable threshold value signal (UF) are added to this converter DC voltage signal (U6) in an adder (16). A turn-on enable signal (F) is produced when the voltage on an individually switching thyristor (T1-T6) of the converter (5) is at least equal to an enable threshold value voltage. If a load current signal (i8) exceeds a current limit value (iGR), which can be predetermined, after a thyristor has been turned on (S20), the enable threshold value signal (UF) is suppressed and the control error signal (U0) is updated and stored in the microprocessor (19). <IMAGE>