A kind of high precision electric current transducer testing circuit
Technical field
The utility model relates to electric automobile power battery system charging and discharging currents detection technique field, specifically a kind of high precision electric current transducer testing circuit.
Background technology
At present, the isolation detection of electric automobile power battery system charging and discharging currents often adopts Hall sampling method.Hall sampling method carries out current sample by Hall current sensor, Hall current sensor is based on magnetic balance type hall principle, i.e. closed loop principle, the magnetic flux that primary current produces concentrates in magnetic circuit by high-quality magnetic core, Hall element is fixed in air gap and detects magnetic flux, through the process of special circuit, the output terminal of Hall current sensor can export the change voltage signal of accurately reflection primary current.The magnetic induction density that output voltage and Hall element are experienced is directly proportional, and magnetic induction density is relevant with primary current and magnetic permeability, and magnetic permeability is generally change, that is, is nonlinear.
Therefore, the output linearity degree of Hall current sensor mainly affects by magnetic permeability is nonlinear, its electric current is higher in the magnetic core unsaturation stage linearity, after magnetic core is in saturation stage, general linear degree is poor, when magnetic field strength increases, its output voltage no longer increases, and have impact on measuring accuracy.Otherwise when changes of magnetic field is not obvious, the change of its output voltage is also relatively little, this situation is when curent change is less, and the change of its output voltage is not obvious, also easily causes measuring error.
In the application process of electric automobile, when flowing through the curent change of wire at hundreds of ampere-hour, use magnetic core and Hall element that a magnetic induction density is relevant, its output voltage linearly changes, and can reflect that current real current changes; When electric automobile is in quiescent operation, master driver no-output, its working current changes at about ± 10 ~ 35A, now, magnetic core and Hall element that if use, aforesaid magnetic induction density is relevant, because its curent change is little, changes of magnetic field is not obvious, and current output voltage resolution is low, truly can not reflect curent change, there is obvious deviation when carrying out SOC statistics, causing larger current accumulation error.
Utility model content
The purpose of this utility model is to provide a kind of high precision electric current transducer testing circuit, the charging and discharging currents of real-time detection electrokinetic cell system, in different current phase, the high precision electric current transducer matched with it is adopted to detect, and by state-detection and signal sampling, obtain current value comparatively accurately, improve sampling precision, reduce current accumulation error.
The technical solution of the utility model is:
A kind of high precision electric current transducer testing circuit, comprises combination magnetoelectricity converting unit, positive threshold comparer, negative sense threshold comparator, OR circuit, output buffer, analog switch and ADC converter; Described combination magnetoelectricity converting unit is made up of compared with the second current sensor of small-range with having first current sensor with relatively large journey, the output terminal of described first current sensor connects the input end of ADC converter by the normally opened contact of analog switch, the output terminal of described second current sensor connects the input end of ADC converter by the normally closed contact of analog switch; The output terminal of described ADC converter connects the input end of late-class circuit;
The in-phase input end of described positive threshold comparer connects the output terminal of the second current sensor, and its inverting input is connected to the first reference voltage, and its output terminal connects the input end of OR circuit; The inverting input of described negative sense threshold comparator connects the output terminal of the second current sensor, and its in-phase input end is connected to the second reference voltage, and its output terminal connects the input end of OR circuit; Described first reference voltage is the voltage that the maximum Limited Current of forward of the second current sensor is corresponding, and described second reference voltage is the voltage that the maximum Limited Current of negative sense of the second current sensor is corresponding; The output terminal of described OR circuit connects the input end of output buffer and the control end of analog switch respectively, and the output terminal of described output buffer connects the input end of late-class circuit.
Described high precision electric current transducer testing circuit, described first current sensor and the second current sensor are fixed in same encapsulation, the range of described first current sensor is-600A ~+600A, and the range of described second current sensor is-60A ~+60A.
Described high precision electric current transducer testing circuit, described first current sensor and the second current sensor all select Hall current sensor.
Described high precision electric current transducer testing circuit, ADG849 type single pole double throw analog switch selected by described analog switch.
As shown from the above technical solution, current sensors different for two ranges is combined in a fixing cavity by the utility model, be packaged into an entirety, the measurement range of each current sensor is given priority to, first current sensor is higher to big current change responsiveness, second current sensor is higher to small area analysis responsiveness, when electric current is among a small circle during change, the magnetic field conversion of the first current sensor is not obvious, show as electric current to change hardly, the change of its output voltage is also very little, and the second current sensor can respond this changes of magnetic field preferably, its output voltage can reflect that current flow changes preferably, and when the range of electric current more than the second current sensor, because magnetic core is close to saturated, electric current is unchanged, its output voltage is also thereupon constant, and now, first current sensor is in optimum linear region of variation, curent change can be reflected preferably, and be converted into the voltage signal of a linear change.By reasonably selecting current variation value, two current sensors are grouped together, and by appropriate circuit design, output voltage passage is selected, the channel voltage chosen is sampled, finally be converted into current current value, precision current can be realized preferably on a large scale in range and measure.
The utility model has that measurement range is wide, fast response time, measuring accuracy are high, the linearity and the advantage such as dynamic property is good, working band is wide, reliability is high, overload capacity is strong, can measure the electric current of random waveform, transient peak electric current and have the signal of wider frequency rate variation range, can be widely used in various needs detects in the applied environment of curent change and measurement and control area.
Accompanying drawing explanation
Fig. 1 is structural schematic block diagram of the present utility model;
Fig. 2 is electrical block diagram of the present utility model;
Fig. 3 is Hall current sensor (wide range) current-voltage change schematic diagram;
Fig. 4 is Hall current sensor (small-range) current-voltage change schematic diagram.
Embodiment
The utility model is further illustrated below in conjunction with the drawings and specific embodiments.
As shown in Figure 1 and Figure 2, a kind of high precision electric current transducer testing circuit, for detecting the charging and discharging currents of electric automobile power battery system, comprise combination magnetoelectricity converting unit 1, positive threshold comparer 2, negative sense threshold comparator 3, OR circuit 4, output buffer 5, single pole double throw analog switch 6 and ADC converter 7.Combination magnetoelectricity converting unit 1 is made up of compared with the second Hall current sensor 12 of small-range with having first Hall current sensor 11 with relatively large journey.ADG849 type simulated switch selected by single pole double throw analog switch 6.
The output terminal of the first Hall current sensor 11 connects the normally opened contact of single pole double throw analog switch 6, the output terminal of the second Hall current sensor 12 connects the normally closed contact of single pole double throw analog switch 6, and the output terminal of the second Hall current sensor 12 also connects the in-phase input end of positive threshold comparer 2, the inverting input of negative sense threshold comparator 3 respectively.The inverting input of positive threshold comparer 2 is connected to the first reference voltage, the in-phase input end of negative sense threshold comparator 3 is connected to the second reference voltage, the output terminal of positive threshold comparer 2 and the output terminal of negative sense threshold comparator 3 are connected to the input end of OR circuit 4, the output terminal of OR circuit 4 is connected respectively to the input end of output buffer 5 and the control end of single pole double throw analog switch 6, the Enable Pin ground connection of output buffer 5, the output terminal of single pole double throw analog switch 6 connects the input end of ADC converter 7, the output terminal of output buffer 5 and the output terminal of ADC converter 7 are connected to microprocessor by SPI interface.
As shown in Figure 3, the measurement range of the first Hall current sensor 11 is-600A ~+600A, when the electric current flowing through wire changes between-600A ~+600A, its output voltage linear change between DC0.25V ~ DC4.75V: when electric current is 0, the magnetic field intensity of the first Hall current sensor 11 periphery is 0, its output voltage corresponds to 1/2 of power supply voltage 5V, i.e. DC2.5V; When curent change scope is 0 ~+600A, corresponding voltage is changed to 2.5V ~ 4.75V, and when electric current is greater than+600A, voltage no longer increases; When curent change scope is-600A ~ 0, corresponding voltage is changed to 0.25V ~ 2.5V, and when electric current is less than-600A, voltage no longer reduces.
As shown in Figure 4, the measurement range of the second Hall current sensor 12 is-60A ~+60A, when the electric current flowing through wire changes between-60A ~+60A, its output voltage linear change between DC0.25V ~ DC4.75V: when electric current is 0, the magnetic field intensity of the first Hall current sensor 11 periphery is 0, its output voltage corresponds to 1/2 of power supply voltage 5V, i.e. DC2.5V; When curent change scope is 0 ~+60A, corresponding voltage is changed to 2.5V ~ 4.75V, and when electric current is greater than+60A, voltage no longer increases; When curent change scope is-60A ~ 0, corresponding voltage is changed to 0.25V ~ 2.5V, and when electric current is less than-60A, voltage no longer reduces.
Positive threshold comparer 2 and negative sense threshold comparator 3 are voltage comparator circuit, wherein, the first reference voltage being connected to the inverting input of positive threshold comparer 2 is forward maximum current deboost, assuming that forward maximum current is restricted to 55A, the voltage of its correspondence is 4.5625V, for the ease of voltage-regulation, this magnitude of voltage is set to 4.5V, corresponding Limited Current is 53.33A, and when forward current is greater than this value, positive threshold comparer 2 exports a high level signal; The second reference voltage being connected to the in-phase input end of negative sense threshold comparator 3 is negative sense maximum current deboost, assuming that negative sense maximum current is restricted to-55A, the voltage of its correspondence is 0.4375V, for the ease of voltage-regulation, this magnitude of voltage is set to 0.5V, corresponding Limited Current is-53.33A, and when negative current is less than this value, negative sense threshold comparator 3 exports a high level signal.
When the electric current flowing through wire is between-53.33A ~+53.33A, output voltage linear change between 0.5V ~ 4.5V of the second Hall current sensor 12, when this voltage-drop loading is to the inverting input of the in-phase input end of positive threshold comparer 2 and negative sense threshold comparator 3, according to the character of comparer, positive threshold comparer 2 and negative sense threshold comparator 3 all no-outputs, OR circuit 4 no-output, thus output buffer 5 exports as low level, now, the output voltage signal of the second Hall current sensor 12 enters single pole double throw analog switch 6 through the normally closed contact of single pole double throw analog switch 6, and enter into ADC converter 7 through single pole double throw analog switch 6, the output voltage signal of the second Hall current sensor 12 changed through it is sent into microprocessor by SPI interface and is processed by ADC converter 7, microprocessor is low level state according to output buffer 5, the voltage signal received is converted into the current value between-53.33A ~+53.33A.
When the electric current flowing through wire is greater than+53.33A or is less than-53.33A, the output voltage of the second Hall current sensor 12 is greater than 4.5V or is less than 0.5V, and now, the magnetic field intensity of the second Hall current sensor 12 is close to saturated, and sample rate current deviation is larger.When forward current is greater than+53.33A, positive threshold comparer 2 exports a high level, when negative current is less than-53.33A, negative sense threshold comparator 3 exports a high level, this level signal sends into OR circuit 4, OR circuit 4 exports a high level signal, as the switch-over control signal of single pole double throw analog switch 6, single pole double throw analog switch 6 is made to realize passage bridge, the normally opened contact be connected with the first Hall current sensor 11 closes, the normally closed contact be connected with the second Hall current sensor 12 disconnects, the output of output buffer 5 is high level simultaneously, now, the output voltage signal of the first Hall current sensor 11 enters single pole double throw analog switch 6 through the normally opened contact of single pole double throw analog switch 6, and enter into ADC converter 7 through single pole double throw analog switch 6, the output voltage signal of the first Hall current sensor 12 changed through it is sent into microprocessor by SPI interface and is processed by ADC converter 7, microprocessor is the state of high level according to output buffer 5, the voltage signal received is converted into the current value between-600A ~+600A.
The above embodiment is only be described preferred implementation of the present utility model; not scope of the present utility model is limited; under the prerequisite not departing from the utility model design spirit; the various distortion that those of ordinary skill in the art make the technical solution of the utility model and improvement, all should fall in protection domain that claims of the present utility model determine.