At present, electric motor car is widely used in people's life with the advantage of its energy-saving and environmental protection.Along with the development of lithium-ion electric pool technology, lithium ion battery is used to electric automobiles more and more.And in the application of electric motor car, dozens or even hundreds of cell need to be connected to the voltage that reaches required.In order to guarantee the normal work of electric battery, need to carry out real-time security management and monitoring to each monomer lithium ion battery.Wherein, in electric battery, the detection of monomer battery voltage, due to the existence of battery two ends common mode voltage, can not directly directly gather cell voltage, and need to adopt other means to gather.
At present, the technological means often adopting is by being connected with a differential operational amplifier respectively of cell, thereby gathers the voltage of cell is independent, thereby has eliminated the impact of common mode voltage.
But current cell voltage acquisition system still has following problem:
1. do not carry out electrical isolation, security is lower.
2. during voltage detecting, leakage current loss is larger.
Utility model content
In view of this, fundamental purpose of the present utility model is to provide a kind of and can carries out.
For achieving the above object, the utility model provides a kind of cell voltage acquisition system, comprising:
Electric battery, comprises the cell of a plurality of series connection;
Gating unit, for gating cell to be detected;
The first optocoupler, for being converted to current signal by cell voltage to be detected and exporting the first voltage signal of a correspondence;
Signal transfer unit, for passing to the second optocoupler by described voltage signal;
The second optocoupler, for being converted to second voltage signal by transmitting described the first voltage signal coming;
Ratio circuit, can measuring voltage value for described voltage signal is converted to.
Described signal transfer unit is comparer;
Described comparer is for by the second voltage signal formation feedback comparator circuit of the first voltage signal of described the first optocoupler and the second optocoupler, thereby controls described the first voltage and second voltage value is equal.
Described ratio circuit is a voltage follower circuit.
The utility model further provides a kind of cell voltage acquisition system, comprising:
Electric battery, comprises the cell of a plurality of series connection;
The positive pole of described cell is connected to the positive pole of the diode of the first optocoupler by a resistance;
The transistor collector of described the first optocoupler is connected with the negative input of comparer by divider resistance;
The positive input of described comparer is connected to the collector of the triode of the second optocoupler;
The output terminal of described comparer is connected to the positive pole of the diode of the second optocoupler;
The negative pole of the diode of described the second optocoupler is connected to the positive input of proportion operational amplifier by resistance.
Cell voltage acquisition system of the present utility model adopts linear optical coupling as the signal transmission sampling device of isolation and data acquisition system (DAS), so just the voltage of each batteries of front end is isolated; And, the large voltage of battery is dwindled by a certain percentage, to the magnitude of voltage of battery change is informed to controller faithfully.
Below in conjunction with accompanying drawing and embodiment of the present utility model, the technical solution of the utility model is described in further detail.
Figure 1 shows that the System of voltage acquisition schematic diagram according to embodiment of the present utility model.
As shown in Figure 1, cell voltage acquisition system of the present utility model comprises:
Gating unit, it is connected with electric battery, for passing through controller gating cell to be detected;
Voltage acquisition unit, for carrying out voltage acquisition by the cell to be measured of gating unit gating;
Controller, for controlling gating unit action according to the magnitude of voltage of voltage acquisition unit output.
Below in conjunction with Fig. 2 and Fig. 3, describe voltage collection circuit in cell voltage acquisition system of the present utility model in detail.
Figure 2 shows that the module map according to voltage acquisition unit of the present utility model, Figure 3 shows that the particular circuit configurations figure of voltage acquisition unit shown in Fig. 2.
As shown in Figure 2, voltage acquisition unit further comprises the first optical coupling isolation circuit, signal transfer unit, the second optical coupling isolation circuit and ratio circuit.
Wherein, the first optical coupling isolation circuit comprises optocoupler 102 as shown in Figure 3, the positive pole of its light emitting diode is connected to the positive pole of cell by a resistance R 1, by gating circuit 101, be connected with the negative pole of cell, forms loop with the light emitting diode in optocoupler; Wherein, described gating unit can be an optocoupler diode, as shown in Figure 2.
Like this, the input end light emitting diode in optocoupler is converted to current signal 111 by the voltage signal Vin of cell, the phototriode conducting of output terminal;
According to the principle of optocoupler, in the ideal situation, I11 should with 112 relations in direct ratio; But due in normal operation, the current transmission characteristic of optocoupler often cannot reach the proportional relationship under perfect condition, therefore voltage collection circuit of the present utility model has adopted signal transfer unit 104 and the second optocoupler 103 to carry out accurate current delivery, thereby cell voltage can accurately be gathered and measure;
As shown in Figure 3, signal transfer unit 104 can be a comparer, its negative input is connected to the voltage output end B point of the first optocoupler, its positive input is connected to the voltage output end A point of the second optocoupler, for the current signal of the first optical coupling isolation circuit is passed to the second optical coupling isolation circuit; The output of comparer is connected to the light emitting diode positive pole of the second optocoupler 103; Like this, comparer forms a feedback circuit;
Wherein, input end A point and B point are respectively the dividing point to 15v, and when A point voltage VA is greater than B point voltage VB, comparer is just exported higher magnitude of voltage, and when A point voltage VA is lower than B point voltage VB, comparer is just exported lower magnitude of voltage; Thereby the magnitude of voltage of 2 of A, B is consistent;
Diode cathode in the second optocoupler 103 is connected to a Voltage-output transfer resistance R2, thereby by the current signal that transmission is come, converts voltage signal by transmitting the current signal coming to;
Ratio circuit 105, for the voltage signal by the second optical coupling isolation circuit output, by certain proportion, being transformed to can measuring voltage value.Wherein, ratio circuit can, for the scale operation circuit of an operational amplifier, R5, R6 formation, just can obtain required voltage ratio.
Ratio circuit 105 can be the voltage follower circuit of an operational amplifier formation.Can know, according to as above circuit design, when I21=I12, I11=I22; Thereby, (V
2, visible Vo and input voltage are proportional, therefore monomer battery voltage can be gathered and is converted to the magnitude of voltage Vo that can measure.
Figure 4 shows that the concrete chip figure according to cell voltage acquisition system of the present utility model.Wherein, gating unit can adopt optocoupler electron device TLP512, and the first optocoupler and the second optocoupler can adopt two optocoupler electron device TLP512, can adopt dual operational amplifier electron device LM358 device and ratio circuit as a comparison.As can be seen, the monomer battery voltage Vin (V0-V1) by input is converted to output voltage V out to carry out voltage detecting.
According to cell voltage acquisition system of the present utility model, due to the isolation completely in electrical connection of the signal at optocoupler two ends, there is not any relation, so even be short-circuited and can not have any impact to the use of battery yet at the output terminal of optocoupler.And optocoupler is converted to current signal collection by voltage signal, solved common ground problem.
The above, be only preferred embodiment of the present utility model, not in order to limit protection domain of the present utility model.