Patent ID: 7592815

Claim:
A leakage detection circuit for an electric vehicle that detects electric vehicle battery pack leakage, the leakage detection circuit comprising: a battery pack including a plurality of batteries connected in series, the battery pack having a high voltage side and a low voltage side; first and second leakage detection switches connected to the high and low voltage sides of the battery pack, respectively; a controller that alternately turns the first and second leakage detection switches ON; a leakage detection resistor group having a midpoint and connected to the battery pack via the first and second leakage detection switches, the midpoint of the leakage detection resistor group being connected to the ground; a voltage detector that detects leakage voltage values in the leakage detection resistor group on the high and low voltage sides relative to the ground; and a calculator that calculates an output of the voltage detector and thus detects leakage, wherein the controller turns the first and second leakage detection switches ON and OFF, respectively, to detect a first leakage voltage value of the leakage voltage values, and turns the first and second leakage detection switches OFF and ON, respectively, to detect a second leakage voltage value of the leakage voltage values so that the calculator detects leakage based on the first and second leakage voltage values, wherein the leakage detection resistor group includes first and second voltage detection resistors and first and second voltage dividing resistors, wherein the first and second voltage detection resistors are connected in series, and a connection midpoint of the first and second voltage detection resistors is connected to the ground, wherein the first voltage dividing resistor joins the first voltage detection resistor to the high voltage side of the battery pack via the first leakage detection switch, and the second voltage dividing resistor joins the second voltage detection resistor to the low voltage side of the battery pack via the second leakage detection switch, and wherein a resistance value of the voltage dividing resistors is larger than a resistance value of the voltage detection resistors.