CN210377196U - Circuit structure for improving current adoption precision by using analog circuit - Google Patents
Circuit structure for improving current adoption precision by using analog circuit Download PDFInfo
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- CN210377196U CN210377196U CN201921206496.2U CN201921206496U CN210377196U CN 210377196 U CN210377196 U CN 210377196U CN 201921206496 U CN201921206496 U CN 201921206496U CN 210377196 U CN210377196 U CN 210377196U
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Abstract
The utility model discloses a circuit structure for improving electric current and adopting precision with analog circuit, its characterized in that: the structure comprises a current sampling module, a temperature sampling module and a precision compensation structure; wherein the precision compensation structure includes: the circuit comprises an operational amplifier A, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6; r1, R2, R3 and R4 are connected to the positive input end of the operational amplifier, the other end of R1 is connected with direct-current voltage, the other end of R2 is connected with the output of the temperature sampling circuit, the other end of R3 is connected with the output of the current sampling circuit, the other end of R4 is grounded, R5 and R6 are connected with the negative input end of the operational amplifier, the other end of R5 is grounded, and the other end of R6 is connected with the output end of the operational amplifier; thus, a voltage adder is constructed.
Description
Technical Field
The utility model relates to a power electronic technology field, concretely relates to improve circuit structure of electric current adoption precision with analog circuit.
Background
In motor controllers, phase currents need to be sampled to achieve more accurate control. The existing current sampling mode mainly comprises resistance sampling and Hall sampling. The resistor sampling has low cost and good applicability, but the method has certain power loss and most importantly, the temperature drift of the high-power precise resistor is very serious. The other Hall sampling mode can measure large current and has small power dissipation, but although the sampling mode carries out certain temperature compensation, the sampling precision of the sampling mode is still influenced by temperature, so that the sampling precision is reduced. Therefore, in any sampling mode, if a high-precision sampling result is obtained, temperature compensation must be performed on the sampling data. Therefore, the utility model provides a method for carrying out temperature compensation through analog circuit and improving current sampling precision.
SUMMERY OF THE UTILITY MODEL
To the phenomenon that the sampling precision received the influence of temperature and took place to drift among the foretell temperature sampling scheme, the utility model provides a method for improving current sampling precision with analog circuit.
The technical scheme of the utility model is that: a circuit structure for improving current adoption accuracy by using an analog circuit comprises a current sampling module, a temperature sampling module and an accuracy compensation structure; wherein the precision compensation structure includes: the circuit comprises an operational amplifier A, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6;
r1, R2, R3 and R4 are connected to the positive input end of the operational amplifier, the other end of R1 is connected with direct-current voltage, the other end of R2 is connected with the output of the temperature sampling circuit, the other end of R3 is connected with the output of the current sampling circuit, the other end of R4 is grounded, R5 and R6 are connected with the negative input end of the operational amplifier, the other end of R5 is grounded, and the other end of R6 is connected with the output end of the operational amplifier; therefore, the voltage adder is formed, the proportional addition of the three voltages is realized, and finally, an accurate compensated current sampling signal is obtained. The results were:
compared with the prior art, the utility model discloses a current sampling module can receive device and circuit structure that the temperature influences by any sampling precision such as sampling resistance or hall element. And converts the collected current information into voltage (or still current) to be output to the precision compensation structure.
The temperature sampling module can be an NTC resistor, a temperature sensitive diode and other temperature sensors sensitive and accurate to temperature, and generates a voltage (or current) signal reflecting environmental temperature information to be transmitted to the precision compensation structure.
The precision compensation structure judges and processes the temperature information acquired by the temperature acquisition module, obtains the voltage (current) required to be compensated at the temperature, calculates the voltage (current) and the voltage (current) signal output by the current sampling module and outputs a voltage (current) signal which linearly reflects the size of the sampled current: vout.
When the temperature sampling module outputs a voltage (current) which is in a linear relation with the temperature, the voltage (current) is input into the precision compensation structure. The precision compensation structure judges a temperature point according to the voltage (current), and then determines the size of the voltage (current) to be compensated according to an error curve of the current sampling module. If the error is linear with the temperature (the error increases linearly with the temperature or decreases linearly with the temperature), a linear superposition compensation mode is adopted.
In this case, the accurate current sampling signal is output as Vout, the sampling signal of the actual current sampling module is Vcs, and the temperature signal is VT, then:
Vout＝Vref+bVcs+cVT
vref is the DC voltage to be compensated, and b and c are coefficients.
If the error curve is positively correlated with the temperature and the output of the temperature sampling module is positively correlated with the temperature, the circuit connected according to the figure 1 can obtain the result, but if the error curve is positively correlated with the temperature and the output of the temperature sampling module is negatively correlated with the temperature, the output of the temperature sampling module and the resistance connected with the output of the temperature sampling module are connected to the negative input end of the cloud amplifier for subtraction. Other cases are also analyzed. If the error and the temperature present the relationship of quadratic, differential, integral, etc., the operational amplifier can be used to build a specific operational circuit to realize the function. These solutions are all within the scope of protection of the present patent.
Drawings
FIG. 1 is a linear superposition compensation circuit structure of the present invention, in which the current sampling error is linear with the temperature;
fig. 2 is a scheme architecture for improving current sampling accuracy of the present invention;
fig. 3 is the sectional compensation circuit structure of the present invention in which the current sampling error is in a nonlinear relationship with the temperature.
Detailed Description
The working principle of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.
The utility model provides a scheme that improves current sampling precision with analog circuit includes several parts of current sampling circuit, temperature sampling circuit, precision compensation structure.
Temperature sampling can be realized by NTC resistance and diode isothermal sensitive devices. Taking the NTC resistor as an example, a reference current (which does not change with temperature) flows through the NTC resistor, and the voltage across the resistor decreases with the increase of temperature, i.e., the linear reaction temperature value. This value can be input into the precision compensation structure, or the voltage can be converted into a voltage which increases with the temperature increase or a current which has a linear relation with the temperature through a certain conversion, addition and subtraction structure, as the case may be.
The current sampling circuit may be implemented with a sampling resistor or a hall element. The voltage (or current) signal reflecting the magnitude of the sampled current is affected by temperature and generates a certain error. May be higher or lower than the actual value.
Before designing the precision compensation structure, the current sampling structure needs to be tested to obtain a relation curve of sampling errors along with temperature changes. It is then determined from the curve how much voltage (or current) should be compensated into the measured signal at a certain temperature to get an actual accurate value. The simplest of these is that the error is linear with temperature. The case of linear errors and the case of non-linear errors are discussed below in two embodiments.
When the error between the output of the current sampling circuit and the actual value is linear, the relationship between the actual value and the sampling value can be expressed as:
Vout＝Vref+bVcs+cVT
vout is voltage which truly reflects the magnitude of sampled current, namely the output of the temperature compensation circuit, Vcs is the output of the current sampling circuit, the information reflected by the voltage contains certain error, VT is a voltage value which is in a linear relation with temperature, Vref is a direct-current voltage value to be compensated, and b and c are coefficients. According to this relation, the precision compensation structure can be designed such that two voltages are proportionally added by a voltage adder as shown in fig. 2. An accurate output value is obtained.
If the error curve is positively correlated with the temperature and the output of the temperature sampling module is positively correlated with the temperature, the circuit connected according to fig. 2 can obtain the result, but if the error curve is positively correlated with the temperature and the output of the temperature sampling module is negatively correlated with the temperature, the output of the temperature sampling module and the resistance connected with the output of the temperature sampling module are connected to the negative input end of the cloud amplifier for subtraction. Other cases are also analyzed. If the error and the temperature present the relationship of quadratic, differential, integral, etc., the operational amplifier can be used to build a specific operational circuit to realize the function.
Because the relation of the sampling error of a specific sampling circuit along with the change of the temperature is very complex, a specific function is difficult to fit, or the error after fitting is still not negligible, namely, a segmented compensation mode which has higher compensation precision, is relatively more flexible and can be more generally applied to various error compensation can be adopted.
In the scheme of sectional compensation, the compensation accuracy is closely related to the number of comparators, for convenience of understanding, taking four comparators in fig. 3 as an example, the output of the temperature sampling circuit is connected to the input end of each comparator, the other input end of the comparator is connected with the reference voltages V1, V2, V3 and V4 … … which are not connected, if the voltage output by the temperature sampling module is the voltage which is increased along with the temperature increase, V1, V2, V3 and V4 … … are sequentially increased according to a certain step size, and otherwise are sequentially decreased. The output of each comparator controls an NMOS tube to be used as a switch, and controls the switch of a reference current, wherein the reference current is the mirror image current of Iref. Taking the first route as an example: the source terminal of MP0 is connected to the power supply and the drain terminal and gate terminal are connected to Iref, forming a self-bias. The gate of the MP0 is connected with the gates of all the back PMOSs to form a current mirror, and the mirror ratio of the current mirror is set according to the step sizes of V1, V2, V3 and V4 … … and the errors of the temperature points represented by the step sizes. The source terminal of MP1 is connected with power voltage. The drain of MP1 is connected to the drain of MN 1. The source of MN1 is connected with the upper end of resistor R12, and the gate of MN1 is connected with the output of comparator COMP1 and is controlled by comparator COMP 1. In the first path, V1 is connected with the positive input end of COMP1, the temperature sampling circuit is connected with the negative input end of COMP1, if the output of the temperature sampling circuit is reduced to be lower than V1 due to temperature rise, the output of the comparator is high, MN1 is conducted, current on MP1 is injected into R12, and the voltage on R12 is increased. So that the value of the error compensation increases. The other circuits are connected according to the circuit, if the temperature rises to a certain value and the error is reduced, the compensated voltage should be reduced, so that the reference voltage corresponding to the temperature point of the temperature sampling circuit should be connected to the negative input end of the comparator, the output of the temperature sampling circuit is connected to the positive input end of the comparator, and when the temperature rises to the point, the current of the circuit is turned off, so that the voltage on the resistor R12 is reduced. The mirror current value of each path is set to the error voltage (set to VN) that should be increased (or decreased) with respect to the previous temperature point divided by R. If the mirror ratio of a certain cry to the reference current is 1: k, and the reference point of the way wants to have an error voltage VN with respect to the previous reference point, then:
I＝K*Iref＝VN/R12
the connection of the inputs of each comparator depends on whether the error compensation should be increased or decreased depending on the point at which the temperature reaches this point.
R12 is first fed with a reference current Iref1, i.e. a dc voltage is first compensated, the specific value is determined according to the error condition, then the current of all branches is fed through R12 to form a total error compensation voltage, which is fed to the positive input terminal of the operational amplifier a 2. The negative input of the operational amplifier a2 is connected to its output and to one end of R7, forming a unity gain negative feedback. The voltage on the R12 is not influenced by the subsequent stage circuit by clamping and isolation of the A2. The output of the current sampling circuit is connected to R8. The other ends of R7 and R8 and R9 are connected to the positive input end of the operational amplifier A1, and the other end of R9 is grounded. The negative input ends of the operational amplifier are connected with R10 and R11, the other end of R10 is grounded, and the other end of R11 is connected with the output of the operational amplifier and serves as the output of the whole system. R7, R8, R9, R10, R11, and an operational amplifier a1 constitute an addition operation circuit as in the previous embodiment, and the compensated error voltage is added to the output of the current sampling circuit to form a precise output.
In order to improve the compensation accuracy of the accuracy compensation structure, it is necessary to decrease the steps between V1, V2, and V3 … … while increasing the number of comparators. The specific situation is adjusted according to the application requirements.
It is to be understood that the invention is not limited to the precise arrangements and components shown above. Various modifications, changes and optimizations may be made to the order of the steps, details and operations of the above methods and structures without departing from the scope of the claims.
Claims (1)
1. A circuit structure for improving current adoption accuracy by using an analog circuit is characterized in that: the structure comprises a current sampling module, a temperature sampling module and a precision compensation structure; wherein the precision compensation structure includes: the circuit comprises an operational amplifier A, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a sixth resistor R6;
r1, R2, R3 and R4 are connected to the positive input end of the operational amplifier, the other end of R1 is connected with direct-current voltage, the other end of R2 is connected with the output of the temperature sampling circuit, the other end of R3 is connected with the output of the current sampling circuit, the other end of R4 is grounded, R5 and R6 are connected with the negative input end of the operational amplifier, the other end of R5 is grounded, and the other end of R6 is connected with the output end of the operational amplifier; the voltage adder is formed in this way, the proportional addition of the three voltages is realized, and finally, an accurate compensated current sampling signal is obtained; the results were:
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| CN201921206496.2U CN210377196U (en) | 2019-07-29 | 2019-07-29 | Circuit structure for improving current adoption precision by using analog circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113867470A (en) * | 2021-10-29 | 2021-12-31 | 西安微电子技术研究所 | Temperature compensation type constant current source unit and current frequency conversion circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113867470A (en) * | 2021-10-29 | 2021-12-31 | 西安微电子技术研究所 | Temperature compensation type constant current source unit and current frequency conversion circuit |
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