Apparatus and method for diagnosing insulation resistance measurement circuit
An apparatus and method for diagnosing an insulation resistance measurement circuit, and more particularly an insulation resistance measurement circuit of a battery cell or a battery module. When diagnosing the state of the insulation resistance measurement circuit, since the voltage ratio based on the measured voltage value of the battery module and the estimated voltage value is used, there is an advantage that the state of the insulation resistance measurement circuit may be diagnosed more diversely and accurately.
1 . An apparatus for diagnosing an insulation resistance measurement circuit, comprising:
a voltage sensor configured to measure a voltage of a battery module having at least one battery cell;
a first diagnosing circuit connected to a positive electrode terminal of the battery module and configured to include a plurality of first diagnosis resistors and a first switch, wherein the first diagnosing circuit is configured to measure a first insulation resistance on a positive side of the battery module, wherein the first insulation resistance is indicative of leakage current on the positive side of the battery;
a second diagnosing circuit connected to a negative electrode terminal of the battery module and configured to include a plurality of second diagnosis resistors, a second switch and a power supply, wherein the second diagnosing circuit is configured to measure a second insulation resistance on a negative side of the battery module, wherein the second insulation resistance is indicative of leakage current on the negative side of the battery; and
a control unit configured to:
calculate an estimated voltage value of the battery module based on a first voltage value calculated based on a first signal received from the first diagnosing circuit and a second voltage value calculated based on a second signal received from the second diagnosing circuit,
calculate a voltage ratio between the calculated estimated voltage value and the voltage of the battery module measured by the voltage sensor,
compare the calculated voltage ratio to a reference ratio,
diagnose a state of the insulation resistance measurement circuit of the battery module according to the comparison of the calculated voltage ratio to the reference ratio, and
control a connection of the battery module along a charging and discharging path of the battery module based on the diagnosis,
wherein the control unit is configured to set the reference ratio as a predetermined ratio range, diagnose the state of the insulation resistance measurement circuit as a failure state when the voltage ratio is not within the predetermined ratio range, and output a diagnostic trouble code corresponding to the failure state, and
wherein after outputting the diagnostic trouble code, the control unit is configured to send a turn-off command to a main switch positioned on a charging and discharging path of the battery module to block a connection of the battery module.
2 . The apparatus according to claim 1 ,
wherein the plurality of first diagnosis resistors include:
a first resistor, a second resistor and a third resistor connected in series between the positive electrode terminal of the battery module and the control unit; and
a fourth resistor having a first end connected to a node between the second resistor and the third resistor and a second end connected to a first ground,
wherein the first switch is connected in series between the first resistor and the second resistor.
3 . The apparatus according to claim 2 ,
wherein the plurality of second diagnosis resistors include:
a sixth resistor, a seventh resistor and an eighth resistor connected in series between the negative electrode terminal of the battery module and the control unit; and
a ninth resistor having a first end connected to a node between the seventh resistor and the eighth resistor and a second end connected to the power supply unit,
wherein the second switch is connected in series between the sixth resistor and the seventh resistor,
wherein the power supply has a first end connected to the ninth resistor and a second end connected to the ground.
4 . The apparatus according to claim 3 ,
wherein the first diagnosing circuit further includes a first capacitor connected in series between the fourth resistor and the ground,
wherein the plurality of first diagnosis resistors further include a fifth resistor connected in parallel to the first capacitor,
wherein the plurality of second diagnosis resistors further include a tenth resistor positioned between the ninth resistor and the power supply and having a first end connected to the second end of the ninth resistor and a second end connected to the power supply, and
wherein the second diagnosing circuit further includes a second capacitor having a first end connected to a node between the ninth resistor and the tenth resistor and a second end connected to the ground.
5 . The apparatus according to claim 1 ,
wherein the control unit is configured to:
estimate a positive electrode voltage value of the battery module based on the first voltage value, a resistance of the plurality of first diagnosis resistors and a resistance of the first switch,
estimate a negative electrode voltage value of the battery module based on a voltage value supplied from the power supply, the second voltage value, a resistance of the plurality of second diagnosis resistors and a resistance of the second switch, and
calculate the estimated voltage value by adding the estimated positive electrode voltage value and the estimated negative electrode voltage value.
6 . The apparatus according to claim 5 , wherein the voltage ratio is calculated using:
R
O
V
=
Vp
+
Vn
Bv
wherein ROV is the voltage ratio, Bv is the voltage of the battery module measured by the voltage sensor, Vp is the estimated positive electrode voltage value, and Vn is the estimated negative electrode voltage value.
7 . The apparatus according to claim 1 ,
further comprising a temperature sensor configured to measure a temperature of the battery module, and
wherein the controller is configured to change the predetermined ratio range based on the temperature of the battery module measured by the temperature sensor.
8 . The apparatus according to claim 7 ,
wherein the control unit is configured to:
increase a size of the predetermined ratio range in response to the measured temperature of the battery module being higher than an upper temperature limit, and
decrease the size of the predetermined ratio range in response to the measured temperature of the battery module being lower than a lower temperature limit.
9 . The apparatus according to claim 1 ,
wherein the controller is configured to estimate a state of charge (SOC) of the battery module and change the predetermined ratio range based on the estimated SOC.
10 . The apparatus according to claim 1 ,
wherein after outputting the diagnostic trouble code, the control unit is configured to send the turn-off command to the main switch only when receiving a main switch turn-off command from outside of the apparatus.
11 . A battery pack, comprising the apparatus according to claim 1 .
12 . A method for diagnosing an insulation resistance measurement circuit, comprising:
measuring, by a voltage sensor, a voltage of a battery module having at least one battery cell;
calculating, by a control unit, an estimated voltage value based on a first voltage value calculated based on a first signal received from a first diagnosing circuit, and a second voltage value calculated based on a second signal received from a second diagnosing circuit, wherein the first diagnosing circuit is configured to measure a first insulation resistance on a positive side of the battery module, wherein the first insulation resistance is indicative of leakage current on the positive side of the battery, wherein the second diagnosing circuit is configured to measure a second insulation resistance on a negative side of the battery module, and wherein the second insulation resistance is indicative of leakage current on the negative side of the battery;
calculating, by the control unit, a voltage ratio between the calculated estimated voltage value and the measured voltage of the battery module;
comparing, by the control unit, the calculated voltage ratio to a reference ratio;
diagnosing, by the control unit, a state of the insulation resistance measurement circuit of the battery module according to the comparison result of the calculated voltage ratio to the reference ratio; and
controlling, by the control unit, a connection of the battery module along a charging and discharging path of the battery module based on the diagnosis,
wherein the method further includes:
setting, by the control unit, the reference ratio as a predetermined ratio range, diagnose the state of the insulation resistance measurement circuit as a failure state when the voltage ratio is not within the predetermined ratio range, and output a diagnostic trouble code corresponding to the failure state; and
after outputting the diagnostic trouble code, sending, by the control unit, a turn-off command to a main switch positioned on a charging and discharging path of the battery module to block a connection of the battery module.