Sampling circuit monitoring voltage across smoothing capacitor - is connected at static inverter DC input to produce switching signal

摘要

The sampling circuit, for e.g. locomotives, samples the voltage across the smoothing capacitor connected to a static inverter DC input. The smoothing capacitor(1) is shunted by the series combination of a discharge registor(6), a zener diode(7) and a variable resistor(8). A voltage divider(10, 11) is connected across the zener diode and variable resistor and its tapping is connected to the non-inverting input of an operational amplifier(9) whose inverting input is connected to the junction between the zener diode and the variable resistor. The operational amplifier drives the LED in an optoelectronic coupler and acts as a switch with hysteresis the phototransistor output voltage is the switch's output.