LIGHT LOAD DETECTOR AND DC FAN ABNORMALITY DETECTOR

PURPOSE:To obtain a light load detector having low power loss by connecting a diode in parallel with a current detection resistor. CONSTITUTION:A parallel circuit of a current detection resistor RS and a diode D is connected between a DC power source E and a load. When the load current is low, the majority of the load current flows through the current detection resistor RS. Consequently, the voltage across the current detection resistor RS produced through the current flowing through the current detection resistor RS is proportional to the load current, and the voltage is compared with a threshold voltage in order to detect a light load. When the load current exceeds a predetermined level, the load current starts to shunt to the diode D, thus maintaining the current flowing through the current detection resistor RS at a constant level. Overload can be detected by comparing the voltage across the diode D with the threshold value. At this time, power loss of the current detection resistor is low.