Detailed Description
Fig. 1 is a block diagram showing a secondary battery monitoring device 100 according to an embodiment of the present invention.
The secondary battery monitoring device 100 includes: voltage- current conversion circuits 11, 21; selection switches 12, 22; resistance circuits 13, 23; reference voltage circuits 14, 24; switches 15, 16, 25, 26; comparators 17, 18, 27, 28; a current-voltage conversion circuit 31; operational amplifiers 32, 35; MOS transistors 33, 36; resistors 34, 37; a reference voltage circuit 38; and a current mirror circuit 39.
Although not shown, the secondary battery monitoring device 100 includes a control circuit and the like that controls the charge/discharge control switch based on the voltage information and the like of the secondary batteries C1 and C2.
The comparators 17 and 27 are comparators for detecting over-discharge, and the comparators 18 and 28 are comparators for detecting over-discharge. The resistor circuit 13 is connected in series with three resistors 13a, 13b, and 13c having resistance values Ra, Rb, and Rc. The resistor circuit 23 is connected in series with three resistors 23a, 23b, and 23c having resistance values Ra, Rb, and Rc. The reference voltage circuits 14, 24 output a reference voltage vref.
The voltage- current conversion circuits 11 and 21, the current-voltage conversion circuit 31, the operational amplifier 32, the MOS transistor 33, and the resistor 34 are current generation circuits for generating a current Ic for making the node detected by the comparators 17 and 18 (27 and 28) in the resistor circuits 13 and 23 the reference potential of the reference voltage circuits 14 and 24 the same. The operational amplifier 35, the MOS transistor 36, the resistor 37, and the reference voltage circuit 38 are current generation circuits that generate a current Ir for setting the node detected by the comparators 17 and 18 (27 and 28) in the resistor circuits 13 and 23 to a voltage for failure diagnosis.
The voltage-to-current conversion circuit 11 has input terminals connected to both ends of the secondary battery C1, and output terminals connected to the input terminals of the current-to-voltage conversion circuit 31 via the selection switches 12. Both ends of the resistor circuit 13 are connected to both ends of the secondary battery C1, a first output terminal is connected to the inverting input terminal of the comparator 17, and a second output terminal is connected to the non-inverting input terminal of the comparator 18. An output terminal of the reference voltage circuit 14 is connected to a non-inverting input terminal of the comparator 17 and an inverting input terminal of the comparator 18.
The voltage-to-current conversion circuit 21 has input terminals connected to both ends of the secondary battery C2, and output terminals connected to the input terminals of the current-to-voltage conversion circuit 31 via the selection switches 22. Both ends of the resistor circuit 23 are connected to both ends of the secondary battery C2, a first output terminal is connected to the inverting input terminal of the comparator 27, and a second output terminal is connected to the non-inverting input terminal of the comparator 28. An output terminal of the reference voltage circuit 24 is connected to a non-inverting input terminal of the comparator 27 and an inverting input terminal of the comparator 28. Output terminals of the comparators 17, 18, 27, and 28 are connected to input terminals of a control circuit, not shown.
The non-inverting input terminal of the operational amplifier 32 is connected to the output terminal of the current-voltage conversion circuit 31, and the output terminal is connected to the gate of the MOS transistor 33. The source of the MOS transistor 33 is connected to one end of the resistor 34 and the inverting input terminal of the operational amplifier 32.
The non-inverting input terminal of the operational amplifier 35 is connected to the output terminal of the reference voltage circuit 38, and the output terminal is connected to the gate of the MOS transistor 36. A source of the MOS transistor 36 is connected to one end of the resistor 37 and the inverting input terminal of the operational amplifier 35.
The current mirror circuit 39 has an input terminal connected to the drain of the MOS transistor 36 and an output terminal connected to the drain of the MOS transistor 33. The switch 15 is connected between the output terminal of the current mirror circuit 39 and the inverting input terminal of the comparator 17. The switch 16 is connected between the output terminal of the current mirror circuit 39 and the non-inverting input terminal of the comparator 18. Switch 25 is connected between the output terminal of current mirror circuit 39 and the inverting input terminal of comparator 27. Switch 26 is connected between the output terminal of current mirror circuit 39 and the non-inverting input terminal of comparator 28.
The voltage/current conversion circuit 11 (21) converts the voltage of the secondary battery C1 (C2) into a current and inputs the current to the current/voltage conversion circuit 31. The current-voltage conversion circuit 31 converts the current of the voltage-current conversion circuit 11 (21) into a voltage and inputs the voltage to the non-inverting input terminal of the operational amplifier 32. The operational amplifier 32 controls the gate of the MOS transistor 33 so that the voltage generated in the resistor 34 is equal to the voltage of the current-voltage conversion circuit 31. At this time, the current flowing through the resistor 34 is a current proportional to the voltage of the secondary battery, and its value is designated as Ic. The operational amplifier 35 controls the gate of the MOS transistor 36 so that the voltage generated in the resistor 37 is equal to the voltage of the reference voltage circuit 38. At this time, the value of the current flowing through the resistor 37 is Ir.
Next, the failure diagnosis function of the secondary battery monitoring apparatus 100 will be described.
When a failure diagnosis of the circuit monitoring the secondary battery C1 is performed, the selection switch 12 is turned on and the selection switch 22 is turned off. The voltage-current conversion circuit 11 converts the voltage VC1 of the secondary battery C1 into a current, and inputs the current to the current-voltage conversion circuit 31 via the selection switch 12. The current-voltage conversion circuit 31 converts the input current into a voltage VC1, and obtains a current Ic proportional to the voltage VC1 of the secondary battery C1 through the operational amplifier 32 and the resistor 34 and the MOS transistor 33.
Here, the resistance value R34 of the resistor 34 is switched so as to be equal to the upstream side resistance value of the resistor circuit of the comparator to be diagnosed, that is, the resistance value Ra when the comparator 17 is diagnosed, and the resistance value Ra + Rb when the comparator 18 is diagnosed.
Further, the voltage of the reference voltage circuit 38 is also switched according to the diagnosed comparator. The voltage value of the reference voltage circuit 38 outputs a voltage Vud smaller than the reference voltage vref in the case of the diagnostic comparator 17, and outputs a voltage Vod higher than the reference voltage vref in the case of the diagnostic comparator 18.
Further, the resistance value 37 of the resistor 37 is switched to the equivalent input resistance value of the resistor circuit viewed from the input part of the comparator to be diagnosed. Thus, the resistance value 37 is set to 1/{ 1/Ra + 1/(Rb + Rc) } in the case of the diagnostic comparator 17, and to 1/{ 1/(Ra + Rb) + 1/Rc } in the case of the diagnostic comparator 18.
These switches are performed in response to a control signal of a test circuit not shown.
Then, the resistance circuit 13 and the reference voltage circuit 14 are diagnosed by causing currents corresponding to the current Ic flowing through the resistance 34 and the current Ir flowing through the resistance 37 to flow into the resistance circuit 13 or to flow out of the resistance circuit 13.
Next, the operation of the failure diagnosis will be described.
The selection switch 12 is turned on, the resistance value R34 is set to the resistance value Ra, the resistance value 37 is set to 1/{ 1/Ra + 1/(Rb + Rc) }, and the voltage of the reference voltage circuit 38 is set to the voltage Vud. Thus, current Ic is VC1/Ra, and current Ir is Vud { 1/Ra + 1/(Rb + Rc) }.
When the switch 15 is turned on, a current Ic-Ir for failure detection flows from the connection point of the resistor 13a and the resistor 13b through the resistor 34 via the switch 15, and the voltage at the inverting input terminal of the comparator 17 becomes the voltage Vud. At this time, the current Ic makes the potential of the connection point of the resistor 13a and the resistor 13b equal to the potential of the negative electrode of the secondary battery C1, and the current Ir makes the potential of the connection point of the resistor 13a and the resistor 13b higher than the potential of the negative electrode of the secondary battery C1 by the voltage Vud. That is, the voltage Vud can be applied to the inverting input terminal of the comparator 17 regardless of the voltage VC1 of the secondary battery C1.
Here, since the voltage Vud is lower than the reference voltage vref, the comparator 17 detects overdischarge. Therefore, the comparator 17 does not detect the over-discharge, and thus an abnormality that the reference voltage vref becomes low can be detected. In addition, the comparator 17 can detect an abnormality that the resistance value Ra becomes low without detecting over-discharge. Further, the comparator 17 can detect an abnormality that the resistance value Rb or the resistance value Rc becomes high without detecting over-discharge.
Then, the switch 15 is turned off, the resistance value R34 is set to the resistance value Ra + Rb, the resistance value R37 is set to 1/{ 1/(Ra + Rb) + 1/Rc }, and the voltage of the reference voltage circuit 38 is set to the voltage Vod. By setting this, current Ic is VC1/Ra + Rb, and current Ir is Vod { 1/(Ra + Rb) + 1/Rc }.
When the switch 16 is turned on, the current Ir-Ic for failure detection flows from the current mirror circuit 39 to the connection point between the resistor 13b and the resistor 13c via the switch 16, and the voltage at the non-inverting input terminal of the comparator 18 becomes the voltage Vod. At this time, the current Ic makes the potential of the connection point between the resistor 13b and the resistor 13C equal to the potential of the negative electrode of the secondary battery C1, and the current Ir makes the potential of the connection point between the resistor 13b and the resistor 13C higher than the potential of the negative electrode of the secondary battery C1 by the voltage Vod. That is, the voltage Vod can be applied to the non-inverting input terminal of the comparator 18 regardless of the voltage VC1 of the secondary battery C1.
Here, since the voltage Vod is higher than the reference voltage vref, the comparator 18 detects overcharge. Therefore, the comparator 18 does not detect overcharge, and thus an abnormality that the reference voltage vref increases can be detected. In addition, the comparator 18 does not detect overcharge, and thus an abnormality that the resistance value Rc becomes low can be detected. In addition, the comparator 18 does not detect overcharge, and thus an abnormality that the resistance value Ra or the resistance value Rb becomes high can be detected.
In addition, the abnormality that the resistance value Rb becomes low can be detected by which of the comparators 17 and 18 malfunctions when the voltage VC1 of the secondary battery C1 is normal.
When the failure diagnosis of the circuit monitoring the secondary battery C2 is performed, these circuits can be diagnosed in the same manner as described above.
Further, by operating only the voltage-current conversion circuit 11 when the switches 15 and 16 are turned off by the voltage-current conversion circuit 11 operating at the time of diagnosis, it is possible to detect a connection failure at the connection point between the secondary battery C1 and the secondary electric ground C2.
Fig. 2 is a block diagram showing a method of performing failure diagnosis for the circuit for failure diagnosis added in the present embodiment. Hereinafter, a method of performing fault diagnosis of the current generation circuit will be described.
The difference from fig. 1 is that: when the switch 15 or 16 is turned on, the selection switch 12 is turned off and the selection switch 22 is turned on. An external power supply capable of changing voltage is connected to a terminal to which the secondary battery C2 should be connected.
In this state, the voltage of the secondary battery C1 is applied to the resistor circuit 13, and a current for failure detection determined by the current Ic generated by the current generation circuit based on the current of the voltage-current conversion circuit 21 and the current Ir flows. More specifically, as for the current for fault detection, the current Ic-Ir flows out from the resistance circuit 13 when the switch 15 is turned on, and the current Ir-Ic flows into the resistance circuit 13 when the switch 16 is turned on.
In this state, if the voltage of the external power supply is set to be lower than the voltage of the secondary battery C1, the current Ic is smaller than the current generated from the voltage of the secondary battery C1, and therefore the voltage of the inverting input terminal of the comparator 17 is higher than the voltage Vud. Here, when the voltage is higher than the reference voltage Vref, the comparator 17 does not detect overdischarge, and it can be detected that the current generation circuit including the generated currents Ic and Ir of the voltage-current conversion circuit 21 is not in failure. In addition, a failure in which the voltage of the inverting input terminal of the comparator 17 of the resistance circuit 13 excessively drops can be detected.
Similarly, by turning off the switch 15 and turning on the switch 16, the voltage of the external power supply is changed, and a failure of the overcharge detection circuit and a failure of the excessive increase in the voltage of the non-inverting input terminal of the comparator 18 of the resistance circuit 13 can be detected.
Further, by turning on the selection switch 12 and turning off the selection switch 22, and connecting an external power supply capable of changing the voltage to the terminal to which the secondary battery C1 is to be connected, and performing fault diagnosis, it is possible to detect that the current generation circuit including the voltage-current conversion circuit 11 has no fault.
As described above, the secondary battery monitoring device 100 of the present embodiment includes the current generation circuit that generates the current Ic and the current Ir and the current mirror circuit 39, and switches 15 and 16 (25 and 26) are switched so that a desired current flows through the resistance circuit, so that it is possible to detect a failure of the circuit that monitors the secondary battery C1 (C2) regardless of the failure location or the failure mode.
While the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, although an example in which a circuit for detecting overdischarge and a circuit for detecting overcharge are provided is described as a circuit for monitoring a secondary battery, either of them may be provided. In addition, although a circuit for monitoring two secondary batteries connected in series is taken as an example, the present invention can be similarly implemented regardless of whether one secondary battery is used or whether three or more secondary batteries are used. In addition, although the current generation circuit is described as being configured by the operational amplifier, the MOS transistor, and the resistor, the current generation circuit may satisfy the function, and is not limited to this circuit. The resistance values of the resistors of the resistor circuit 13 and the resistor circuit 23 are set to the same value, but the resistance values of the resistors may be different when the voltages of the secondary batteries C1 and C2 are different. In this case, a current generation circuit needs to be additionally provided.
Description of the reference symbols
100 a secondary battery monitoring device; 11. 21 a voltage-to-current conversion circuit; 14. 24, 38 reference voltage circuits; 17. 18, 27, 28 comparators; 31 a current-to-voltage conversion circuit; 32. 35 an operational amplifier; 39 current mirror circuit.