A low temperature drift precision voltage output circuit

Abstract

This invention relates to a low-temperature drift precision voltage output circuit, which can achieve low-temperature drift precision voltage output. It includes a precision reference source circuit, a voltage divider circuit, and a follower circuit. The precision reference source circuit is used for power conversion, generating a 5V reference voltage to provide a 5V reference voltage to the voltage divider circuit. The voltage divider circuit includes a series-connected negative temperature coefficient compensation circuit and a positive temperature coefficient compensation circuit. The 5V reference voltage provided by the precision reference source circuit is divided and temperature drift compensated, and the compensated voltage is output to the follower circuit. The follower circuit follows the voltage output by the voltage divider circuit, outputting a precision voltage. This invention solves the shortcomings of existing precision voltage circuits, such as large temperature drift, low output accuracy, and limited application environments. It can be directly used in applications with a wide operating temperature range of -55℃ to 125℃, with a temperature drift of only within 0.1mV across the entire temperature range and an output accuracy of less than 0.01mV.

Description

Technical Field

[0001] The invention relates to a precision voltage output circuit, which can realize low-temperature drift precision voltage output and can meet the requirements of wide temperature working range and low temperature drift. Background Art

[0002] In precision guided weapon systems, in order to provide accurate voltage to AD conversion circuits for signal comparison and processing, the voltage is generally required to have high precision and low temperature drift characteristics due to the harsh working environment of the system.

[0003] Since the existing circuit has low precision and a large range of high and low temperature variations, it can only meet the working conditions at room temperature. It cannot meet its precision requirements under harsh working environment conditions and cannot be used. It must be improved. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the existing voltage output circuit and provide a voltage output circuit that meets the requirements of high precision and low temperature drift.

[0005] The technical solution to achieve the purpose of the present invention is:

[0006] A low temperature drift precision voltage output circuit, comprising a precision reference source circuit, a voltage divider circuit and a follower circuit;

[0007] The precision reference source circuit is used for power conversion, generates a 5V reference voltage, and provides a 5V reference voltage for the voltage divider circuit;

[0008] The voltage divider circuit includes a negative temperature coefficient compensation circuit and a positive temperature coefficient compensation circuit connected in series; the 5V reference voltage provided by the precision reference source circuit is divided and temperature drift compensated, and the voltage after voltage division compensation is output to the follower circuit;

[0009] The follower circuit follows the voltage output by the voltage divider circuit and outputs a precise voltage.

[0010] Furthermore, the precision reference source circuit includes a precision voltage stabilizing source, and the input and output ends of the precision voltage stabilizing source are grounded via a capacitor respectively.

[0011] Furthermore, the negative temperature coefficient compensation circuit is composed of a negative temperature coefficient thermistor RNT and a conventional resistor connected in series and parallel.

[0012] Further, the conventional resistor includes a first resistor R1, a second resistor R2 and a third resistor R3;

[0013] The third resistor R3 is connected in series with the negative temperature coefficient thermistor RNT and then in parallel with the second resistor R2. One end of the parallel circuit is connected in series with the first resistor R1. The other end of the first resistor R1 is connected to the 5V reference voltage output by the precision reference source circuit. The other end of the parallel circuit is connected to the positive temperature coefficient compensation circuit and serves as the output of the voltage divider circuit.

[0014] Furthermore, the relationship between the resistance and temperature of the negative temperature coefficient thermistor RNT is:

[0015] R=R0 *expB (1 / T–1 / T0)

[0016] Where, R: resistance value at the first ambient temperature T;

[0017] R0: resistance value at the second ambient temperature T0;

[0018] B: Constant of negative temperature coefficient thermistor.

[0019] Furthermore, the positive temperature compensation coefficient circuit is composed of a positive temperature coefficient temperature sensor resistor RPT and a fourth resistor in series, the other end of the positive temperature coefficient temperature sensor resistor RPT is grounded GND, and the other end of the fourth resistor R4 is connected to the negative temperature coefficient compensation circuit as the output of the voltage divider circuit.

[0020] Furthermore, the follower circuit includes an integrated operational amplifier, the voltage output by the voltage divider circuit is input to the non-inverting input terminal of the integrated operational amplifier, the output terminal of the integrated operational amplifier outputs a precision voltage, and at the same time, the output terminal is fed back to the inverting input terminal of the integrated operational amplifier.

[0021] The advantage of the present invention is that it can achieve high-precision voltage output. It solves the shortcomings of existing precision voltage circuits, such as large temperature drift, low output accuracy and limited application occasions. It can be directly used in occasions with a wide operating temperature range of -55°C to 125°C. The temperature drift in the entire temperature range is only within 0.1mV, and the output accuracy is less than 0.01mV. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The invention discloses a circuit block diagram of a low temperature drift precision voltage output circuit.

[0023] Figure 2a The invention discloses a circuit diagram of a precision reference source circuit of a low temperature drift precision voltage output circuit.

[0024] Figure 2b It is the relationship between the output voltage and temperature of the precision reference source circuit.

[0025] Figure 3 The invention discloses a circuit diagram of a voltage divider circuit of a low temperature drift precision voltage output circuit.

[0026] Figure 4a The invention discloses a circuit diagram of a negative temperature coefficient compensation circuit of a low temperature drift precision voltage output circuit.

[0027] Figure 4b It is the relationship between the resistance and temperature of thermistor RNT in the negative temperature coefficient compensation circuit.

[0028] Figure 5a The invention discloses a circuit diagram of a positive temperature coefficient compensation circuit of a low temperature drift precision voltage output circuit.

[0029] Figure 5b It is the curve of the total resistance value of the positive temperature coefficient compensation circuit changing with temperature.

[0030] Figure 6 The invention discloses a circuit diagram of a low temperature drift precision voltage output circuit follower circuit. DETAILED DESCRIPTION

[0031] The implementation of the present solution is described in detail below with reference to the accompanying drawings.

[0032] Depend on Figure 1 As shown, the low temperature drift precision voltage output circuit of this embodiment includes a precision reference source circuit 11 , a voltage divider circuit 12 (including a negative temperature coefficient compensation circuit 13 and a positive temperature coefficient compensation circuit 14 ) and a follower circuit 15 .

[0033] Depend on Figure 2a As shown in the figure, the precision reference source circuit consists of precision voltage regulator U1 and capacitors C1 and C2. The precision reference circuit mainly converts power supply to produce a high-precision, low-temperature drift 5V reference voltage. Its output voltage has high accuracy, the output is 5.000V±0.003V, and the temperature drift is 3ppm / ℃. When the operating temperature is from -55℃ to 125℃, its output voltage drift is 2.7mV. Its output voltage and temperature curve is as follows Figure 2b shown.

[0034] Depend on Figure 3 As shown in the figure, when the operating temperature is from -55℃ to 125℃, since the final output voltage of the follower is a negative temperature coefficient, if there is no temperature compensation, the output drift reaches +8mV when working at -55℃, and the output drift reaches -10mV when working at 125℃, so temperature compensation design is required. The voltage divider circuit is composed of a negative temperature coefficient compensation circuit and a positive temperature coefficient compensation circuit to complete the temperature compensation of the voltage divider circuit.

[0035] Depend on Figure 4aAs shown, the negative temperature coefficient compensation circuit is composed of resistors R1, R2, R3 and negative temperature coefficient thermistor RNT. Resistor R3 is connected in series with negative temperature coefficient thermistor RNT and then connected in parallel with resistor R2. One end of the parallel circuit is connected in series with resistor R1, and the other end of resistor R1 is connected to the +5V voltage output by the precision reference source circuit. The other end of the parallel circuit is connected to the positive temperature coefficient compensation circuit and serves as the voltage divider output of the voltage divider circuit.

[0036] When the operating temperature is from -55℃ to 125℃, the total resistance value decreases linearly with the increase of temperature. The relationship between the resistance value and temperature of thermistor RNT is as follows:

[0037] R=R0 *expB (1 / T–1 / T0) (1)

[0038] Where, R: resistance value at ambient temperature T(K) (K: absolute temperature);

[0039] R0: resistance value at ambient temperature T0 (K);

[0040] B: B constant of the thermistor.

[0041] Depend on Figure 4b As shown, since the relationship between the resistance value and temperature of the thermistor RNT is a negative temperature exponential curve, when B=4100, the RNT at room temperature (25℃) is 1kΩ, the RNT at low temperature (-55℃) becomes 154.92kΩ, and the RNT at high temperature (125℃) becomes 0.0316kΩ. Through its series resistor R3 and then parallel resistor R2, the total resistance of its resistance R2 / / (RNT+R3) shows a negative temperature linear change.

[0042] Depend on Figure 5a As shown in the figure, the positive temperature coefficient compensation circuit is composed of a series resistor R4 and a positive temperature coefficient temperature sensor resistor RPT. The other end of the resistor RPT is grounded to GND, and the other end of the resistor R4 is connected to the negative temperature coefficient compensation circuit as the voltage divider output of the voltage divider circuit. When the operating temperature ranges from -55℃ to 125℃, the total resistance value increases linearly with the increase of temperature. Its temperature change curve is shown in Figure 5b shown.

[0043] Depend on Figure 6 As shown, the precision voltage division value output by the voltage division circuit is input to the follower circuit, and the follower circuit outputs a precision voltage, thereby completing the output of a high-precision voltage. The follower circuit includes an integrated operational amplifier NA, and the precision voltage division value output by the voltage division circuit is input to the non-inverting input terminal of the integrated operational amplifier NA, and the non-inverting input terminal is simultaneously grounded to GND through capacitor C3. The output terminal of the integrated operational amplifier NA outputs a precision voltage, and at the same time, the output terminal is fed back to the inverting input terminal of the integrated operational amplifier NA.

[0044] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low temperature drift precision voltage output circuit, characterized in that: It includes a precision reference source circuit, a voltage divider circuit and a follower circuit; The precision reference source circuit is used for power conversion, generates a 5V reference voltage, and provides a 5V reference voltage for the voltage divider circuit; The voltage divider circuit includes a negative temperature coefficient compensation circuit and a positive temperature coefficient compensation circuit connected in series; the 5V reference voltage provided by the precision reference source circuit is divided and temperature drift compensated, and the voltage after voltage division compensation is output to the follower circuit; The follower circuit follows the voltage output by the voltage divider circuit and outputs a precise voltage; The negative temperature coefficient compensation circuit is composed of a negative temperature coefficient thermistor RNT and a conventional resistor connected in series and parallel; The conventional resistor includes a first resistor R1, a second resistor R2 and a third resistor R3; The third resistor R3 is connected in series with the negative temperature coefficient thermistor RNT and then connected in parallel with the second resistor R2. One end of the parallel circuit is connected in series with the first resistor R1. The other end of the first resistor R1 is connected to the 5V reference voltage output by the precision reference source circuit. The other end of the parallel circuit is connected to the positive temperature coefficient compensation circuit and serves as the output of the voltage divider circuit. The relationship between the resistance and temperature of the negative temperature coefficient thermistor RNT is: R=R0 *expB (1 / T–1 / T0) Where, R: resistance value at the first ambient temperature T; R0: resistance value at the second ambient temperature T0; B: constant of negative temperature coefficient thermistor; The positive temperature compensation coefficient circuit is composed of a positive temperature coefficient temperature sensor resistor RPT and a fourth resistor in series, the other end of the positive temperature coefficient temperature sensor resistor RPT is grounded GND, and the other end of the fourth resistor R4 is connected to the negative temperature coefficient compensation circuit as the output of the voltage divider circuit.

2. The low temperature drift precision voltage output circuit according to claim 1, characterized in that: The precision reference source circuit comprises a precision voltage stabilizing source, and the input and output ends of the precision voltage stabilizing source are grounded respectively through a capacitor.

3. The low temperature drift precision voltage output circuit according to claim 1, characterized in that: The follower circuit includes an integrated operational amplifier, the voltage output by the voltage divider circuit is input to the non-inverting input terminal of the integrated operational amplifier, the output terminal of the integrated operational amplifier outputs a precision voltage, and at the same time, the output terminal is fed back to the inverting input terminal of the integrated operational amplifier.

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