Combined Overvoltage/Overcurrent Detector
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Both overvoltage and overcurrent faults are detected by a single detector circuit. A DC load current IL passes through a current sense resistor 1 (Fig. 1) to a load 2. The resistance of the resistor 1 is less than 1 ohm, for example, but this creates a potential difference VS-VO . VS is sampled by a divider, which is composed of resistors 3 and 4, with a threshold voltage, VTH, between the resistors 3 and 4 being supplied to a comparator 5 at its inverting input. VO is connected to the comparator 5 at its non-inverting input through a resistor 6. Each of the resistors 3 and 6 is substantially the same resistance, about 1K ohm, for example. When there is an overcurrent condition so that IL increases beyond its threshold, VO drops so that VTH exceeds VO .