Relay diagnostic circuit

A relay diagnostic circuit for a plurality of relays connected in series between an electric vehicle power supply end and a load or a charging end, comprising:

• a plurality of voltage divider branches connected to a same reference ground, an isolation unit and a judgment unit, wherein
• each of the voltage divider branches is configured to obtain a voltage of one end of each relay and output the voltage after dividing the voltage;
• the isolation unit is configured to isolate and convert a plurality of divider voltages output from the plurality of voltage divider branches and output the voltages to the judgment unit;
• and
• the judgment unit is configured to compare a comparison information of the divider voltages at two ends of each relay with a corresponding driving state of the relay and obtain a diagnosis result of each relay;
• and wherein the relay diagnostic circuit further comprises a comparison unit configured to compare divider voltages output from the two voltage divider branches at both ends of a same relay, output the comparison information to the isolation unit, and output the comparison information to the judgment unit after the isolation and conversion of the isolation unit the comparison unit comprises a plurality of comparator groups, each comparator group comprises a forward comparator and a reverse comparator, two comparators of a same comparator group correspond to a same relay, output ends of one of the voltage divider branches for obtaining output voltage of the first end of corresponding relay is connected to a positive input end of the forward comparator and a negative input end of the reverse comparator respectively, output ends of the other voltage divider branch for obtaining output voltage of the second end corresponding to the relay is connected to a negative input end of the forward comparator and the positive input end of the reverse comparator, the output ends of the forward comparator and the reverse comparator of each comparator group is connected as a output end of the comparator group, and output ends of each comparator group are connected to input ends of the isolation unit respectively.