IF board of current frequency conversion circuit

Abstract

The utility model relates to an IF board of a current frequency conversion circuit, which is used for compensating conversion frequency values of IF to current at different temperatures. The circuit specifically comprises an integrating circuit, a power amplifying circuit, a logic control chip, an analog switch and a current adjusting module, the integrating circuit receives external input current and current fed back by the analog switch, the integrating circuit is used for integrating the input current and the current fed back by the analog switch, and the integrating circuit is connected with the power amplifying circuit. The power amplification circuit is used for performing power amplification on the integral voltage output by the integral circuit, the power amplification circuit is connected with the logic control circuit, the logic control circuit is connected with the analog switch, the analog switch is connected with the current regulation module, and the logic control circuit controls the output on-off of the current regulation module through the analog switch. According to the utility model, the MCU is used for controlling the positive fine-tuning current source and the negative fine-tuning current source according to the temperature value, so that the influence of temperature on frequency is eliminated, the control process is simple, and the real-time performance is high.

Description

Technical Field

[0001] The utility model belongs to electrical engineering applications, and in particular relates to a temperature compensation circuit for an IF conversion circuit. Background Art

[0002] The IF circuit board, a key component of a strapdown inertial navigation system, converts the accelerometer's current signal into a frequency signal, providing acceleration information to the system. The IF circuit is crucial because a charge-balanced IF circuit can more completely capture the full current information than direct ADC acquisition. Direct ADC acquisition only captures instantaneous values, hindering the accuracy of the inertial navigation system. Since the IF circuit is primarily constructed from discrete analog components, it is highly susceptible to temperature fluctuations. Therefore, achieving high-precision IF circuits requires temperature compensation. Temperature compensation primarily compensates for the frequency difference in the IF current conversion at different temperatures. Utility Model Content

[0003] In view of this, the present invention provides a current-frequency conversion circuit IF board, which is used to compensate the frequency value of the current converted by IF at different temperatures.

[0004] The technical solution of the utility model is:

[0005] A current-frequency conversion circuit IF board includes an integration circuit, a power amplifier circuit, a logic control chip, an analog switch, a current regulation module,

[0006] The integration circuit receives the external input current and the current fed back by the analog switch. The integration circuit is used to integrate the input current and the current fed back by the analog switch. The integration circuit is connected to the power amplifier circuit. The power amplifier circuit is used to power amplify the integrated voltage output by the integration circuit. The power amplifier circuit is connected to the logic control circuit. The logic control circuit is connected to the analog switch. The analog switch is connected to the current regulation module. The logic control circuit controls the output on and off of the current regulation module through the analog switch.

[0007] Furthermore, the current regulation module includes a forward current regulation module, a negative current regulation module, a microcontroller and a temperature sensor; the forward current regulation module includes a positive constant current source and a positive microcurrent source, and the output of the positive current regulation module is the sum of the outputs of the positive constant current source and the positive microcurrent source; the negative current regulation module includes a negative constant current source and a negative microcurrent source, and the output of the negative current regulation module is the sum of the outputs of the negative constant current source and the negative microcurrent source; the temperature sensor is connected to the microcontroller, and the temperature sensor is used to collect the external ambient temperature. The microcontroller is connected to the positive microcurrent source and the negative microcurrent source respectively.

[0008] Furthermore, the analog switch is MAX313ESE.

[0009] Furthermore, the operational amplifier of the integration circuit is selected as CA3140.

[0010] Furthermore, the operational amplifier of the positive and negative constant current sources is selected as OPA2227U.

[0011] Beneficial effects

[0012] 1. The MCU of the utility model controls the positive fine-tuning current source and the negative fine-tuning current source according to the temperature value, thereby eliminating the influence of temperature on the output frequency of the analog switch. The control process is simple and the real-time performance is high.

[0013] 2. Fine-tuning the feedback current through positive and negative micro-current sources will not affect the overall operation of the system.

[0014] 3. Select CA3140 as the operational amplifier of the integration circuit, which has small offset current.

[0015] 4. The operational amplifier of the constant current source is selected as OPA2227U to ensure that the offset voltage is less affected by temperature and has good temperature characteristics, thereby obtaining a more stable current source in the constant current source.

[0016] 5. The analog switch MAX313ESE has a fast switching speed, which can effectively reduce the impact of the switching speed of the analog switch on the nonlinearity of the IF circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 , an implementation method of the present utility model. DETAILED DESCRIPTION

[0018] A current-frequency conversion circuit board (IF) includes an integration circuit, a power amplifier circuit, a logic control chip (CPLD), an analog switch, a positive constant current source, a negative constant current source, a microcontroller (MCU), a temperature sensor, a positive microcurrent source, and a negative microcurrent source. The positive constant current source and the positive microcurrent source constitute a positive current regulation module, the output of which is the sum of the outputs of the positive constant current source and the positive microcurrent source; the negative current regulation module includes a negative constant current source and a negative microcurrent source, the output of which is the sum of the outputs of the negative constant current source and the negative microcurrent source.

[0019] The integration circuit receives the external input current Iin and the current fed back by the analog switch. The integration circuit integrates the sum of the input current Iin and the feedback current. The output integrated voltage is sent to the logic control circuit (CPLD) after power amplification. The logic control circuit controls the analog switch to control the output on and off of the positive constant current source and the negative constant current source.

[0020] The microcontroller (MCU) uses an external temperature sensor to collect ambient temperature data and control the magnitude of the positive and negative microcurrent sources. These are combined with the positive and negative constant current sources, respectively, to control the magnitude of the current ultimately flowing into the integral current.

[0021] When the current Iin enters the integration circuit for integration, the integral output voltage U is obtained from the relationship between the voltage and current of the capacitor:

[0022] According to the differential equation, we can get

[0023]

[0024] In a very small cycle, the input current can be approximately considered constant. By defining u0 as the initial voltage of integration, we can obtain:

[0025]

[0026] When the voltage u, after adjustment by the op amp, exceeds the logic high level of 1.8v of the logic control chip (CPLD), the forward current regulation module is turned on. If it is lower than the logic low level of 0.4v of the logic control chip CPLD, the negative current regulation module is turned on. The conduction duration is Δt. Taking the forward conduction as an example for a simple deduction, assuming that the output current of the forward current regulation module is I z , the conduction frequency is f, assuming I z is constant, then the following relationship holds:

[0027] I′ in =I z ×Δt×f

[0028] It can be seen that when the temperature changes affect the output frequency f, fine-tuning I z The size of f can be kept unchanged.

[0029] The integration circuit is responsible for integrating the input current and the constant current source controlled by the analog switch;

[0030] The power amplifier circuit is responsible for converting the integrated voltage of the integration circuit into a control range suitable for the logic control chip (CPLD);

[0031] The CPLD controls the analog switch based on the detected voltage value after power amplification and conversion, and determines the on and off of the constant current source.

[0032] The positive and negative direction fine-tuning current can output weak current in the microampere level;

[0033] The MCU is responsible for collecting temperature sensor information and calculating and modifying the positive and negative trimming currents using a temperature compensation function. Typically, the interface between the positive and negative trimming currents and the MCU is SPI, but this is not limited to SPI.

[0034] The MCU controls the positive fine-tuning current source and the negative fine-tuning current source according to the temperature value, which belongs to the existing technology. One specific implementation process is as follows:

[0035] 1). Use MCU to control the positive fine-tuning current source to 0, and the negative fine-tuning constant current source to 0.

[0036] 2) Place the IF current board in a temperature chamber, set the temperature chamber at different temperature points, input a constant current Iin, and record the output frequency f of the IF board.

[0037] 3). By analyzing the relationship between output frequency and temperature, establish the relationship function between output frequency and temperature.

[0038] 4) Based on the functional relationship established in step 3, the relationship between temperature and fine-tuning current is set in the MCU. Usually, the proportional gain factor is adjusted based on the functional relationship.

[0039] 5). MCU controls the positive fine-tuning current source and the negative fine-tuning current source according to the temperature value.

Claims

1. A current-frequency conversion circuit IF board, characterized by: Including integration circuit, power amplifier circuit, logic control chip, analog switch, current regulation module, The integration circuit receives the external input current and the current fed back by the analog switch. The integration circuit is used to integrate the input current and the current fed back by the analog switch. The integration circuit is connected to the power amplifier circuit. The power amplifier circuit is used to power amplify the integrated voltage output by the integration circuit. The power amplifier circuit is connected to the logic control circuit. The logic control circuit is connected to the analog switch. The analog switch is connected to the current regulation module. The logic control circuit controls the output on and off of the current regulation module through the analog switch.

2. The current-to-frequency conversion circuit IF board according to claim 1, characterized in that: The current regulation module includes a forward current regulation module, a negative current regulation module, a microcontroller and a temperature sensor; the forward current regulation module includes a positive constant current source and a positive microcurrent source, and the output of the forward current regulation module is the sum of the outputs of the positive constant current source and the positive microcurrent source; the negative current regulation module includes a negative constant current source and a negative microcurrent source, and the output of the negative current regulation module is the sum of the outputs of the negative constant current source and the negative microcurrent source; the temperature sensor is connected to the microcontroller, and the temperature sensor is used to collect the external ambient temperature. The microcontroller is connected to the positive microcurrent source and the negative microcurrent source respectively.

3. A current-to-frequency conversion circuit IF board according to any one of claims 1-2, characterized in that: The analog switch is MAX313ESE.

4. A current-to-frequency conversion circuit IF board according to any one of claims 1-2, characterized in that: The operational amplifier of the integration circuit is CA3140.

5. The current-to-frequency conversion circuit IF board according to any one of claims 1-2, characterized in that: The operational amplifier for the positive and negative constant current sources is OPA2227U.

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