Temperature compensated reference voltage source

Abstract

The utility model relates to a temperature compensation reference voltage source, and belongs to the technical field of reference voltage sources. The reference voltage source comprises a power supply circuit, a reference voltage stabilizing circuit, a temperature compensation circuit and an output voltage fine tuning circuit, the reference voltage stabilizing circuit comprises a reference diode, and the reference diode is connected with the output end of the power supply circuit through the temperature compensation circuit and used for providing stable output voltage; the temperature compensation circuit is used for adjusting the current provided for the reference diode according to the environment temperature so as to compensate the temperature coefficient of the reference diode; the output voltage fine adjustment circuit adopts a voltage division circuit, and the output voltage of the reference diode is adjusted by adjusting the resistance value of a voltage division resistor on the voltage division circuit, so that the output voltage reaches the set precision. The problem that in the prior art, the output voltage precision and the voltage temperature coefficient of a reference voltage source cannot reach the standard at the same time is solved.

Description

Technical Field

[0001] This utility model relates to a temperature-compensated reference voltage source, belonging to the technical field of reference voltage source technology. Background Technology

[0002] As the standard instrument for energy meter traceability, the accuracy and stability of the 0.01-class standard energy meter are key performance indicators. The voltage and current sampling circuits of the standard energy meter convert the input voltage and current signals into digital signals via an ADC (analog-to-digital converter). The subsequent signal processing section runs the energy metering algorithm to obtain energy-related data and information. In the circuit of the standard energy meter, the sampling accuracy of the ADC depends on the reference voltage source that provides the quantization comparison benchmark.

[0003] The reference voltage sources for the ADC converters of existing 0.01-class standard energy meters are mainly: bandgap reference voltage sources and embedded Zener reference voltage sources.

[0004] The bandgap voltage reference source utilizes the positive temperature coefficient of VBE and the negative temperature coefficient of ΔVBE of the transistor for compensation. By summing these factors, it outputs a temperature-independent reference voltage. Its basic schematic diagram is shown below. Figure 1 As shown, however, the temperature coefficient of most current bandgap reference voltage source chips is between 10ppm / ℃ and 100ppm / ℃, which does not meet the requirement of less than 5ppm / ℃, and the accuracy of their output voltage is also greater than ±0.02%.

[0005] Embedded Zener voltage references primarily utilize the voltage regulation characteristics of diode reverse Zener breakdown. High-precision embedded Zener voltage reference devices include the LTZ1000, whose internal schematic diagram is shown below. Figure 2 As shown, pin 1 is the positive terminal of the internal heater; pin 8 is the collector of the temperature-sensing transistor Q2; pin 3 is the cathode of the internal reference diode; pin 5 is the collector of the compensation transistor; pin 2 is the negative terminal of the internal heater; pin 6 is the base of the temperature-sensing transistor; pin 4 is the anode of the internal substrate and the reference diode; and pin 7 is the emitter of the compensation transistor. The LTZ1000 reference voltage source has a temperature coefficient of 0.02ppm / ℃, making it one of the most stable Zener reference voltage sources globally. However, its output voltage accuracy is greater than 2%, and it is largely monopolized by foreign manufacturers, resulting in high costs and difficulty in procurement. Utility Model Content

[0006] The purpose of this invention is to provide a temperature-compensated reference voltage source to solve the problem that the output voltage accuracy and voltage temperature coefficient of the reference voltage source in the prior art cannot be met at the same time.

[0007] To achieve the above objectives, the solution of this utility model includes:

[0008] This invention discloses a temperature-compensated reference voltage source, comprising a power supply circuit for supplying power to the reference voltage source circuit, a reference voltage regulator circuit, a temperature compensation circuit, and an output voltage fine-tuning circuit. The reference voltage regulator circuit includes a reference diode, which is connected to the output terminal of the power supply circuit through the temperature compensation circuit to provide a stable output voltage. The temperature compensation circuit adjusts the current supplied to the reference diode according to the ambient temperature to compensate for the temperature coefficient of the reference diode. The output voltage fine-tuning circuit employs a voltage divider circuit, adjusting the output voltage of the reference diode by adjusting the resistance value of the voltage divider resistors on the voltage divider circuit to achieve the set accuracy.

[0009] Furthermore, the temperature compensation circuit includes a thermistor with a negative temperature coefficient.

[0010] Furthermore, the temperature compensation circuit also includes a first ordinary resistor and a second ordinary resistor. A thermistor with a negative temperature coefficient is connected in series with the second ordinary resistor and then connected in parallel across the first ordinary resistor. The first ordinary resistor is connected to the output terminal of the power supply circuit. The first ordinary resistor is a metal foil resistor, and the second ordinary resistor is a metal film resistor.

[0011] Furthermore, the voltage divider circuit includes an upper voltage divider circuit and a lower voltage divider circuit, which are connected in series, and the connection point of the upper and lower voltage divider circuits is the output terminal of the voltage divider circuit.

[0012] Furthermore, the upper voltage divider circuit consists of two ordinary resistors connected in parallel; the lower voltage divider circuit consists of two ordinary resistors connected in parallel and then connected in series with one ordinary resistor.

[0013] Furthermore, the thermostatic circuit is attached to the reference diode on the copper substrate. The thermostatic circuit is used to control the temperature of the copper substrate on which the reference diode is attached, so that the reference diode operates in a constant temperature environment.

[0014] Furthermore, the constant temperature circuit includes a temperature sampling circuit and a heating circuit. The temperature sampling circuit is used to collect the temperature of the copper substrate, and the heating circuit is used to adjust the temperature of the copper substrate according to the temperature collected by the temperature sampling circuit, so that the reference diode operates in a constant temperature environment.

[0015] Furthermore, it also includes an output driving circuit, which includes an operational amplifier. One input terminal of the operational amplifier is connected to the output terminal of the voltage divider circuit, and the output terminal of the operational amplifier is connected to the subsequent stage circuit to provide driving current to the subsequent stage circuit.

[0016] The beneficial effects of this invention are as follows: As an improved invention, this temperature-compensated reference voltage source mainly includes a reference voltage regulator circuit, a temperature compensation circuit, and an output voltage fine-tuning circuit. The reference voltage regulator circuit includes a reference diode, which is connected to the output terminal of the temperature compensation circuit to provide a stable output voltage. The temperature compensation circuit can decrease its resistance when the ambient temperature rises, increasing the current supplied to the reference diode and thus increasing the output voltage of the reference diode to compensate for the negative temperature coefficient of the reference diode, which decreases when the temperature rises. Alternatively, when the ambient temperature falls, its resistance can be increased to decrease the current supplied to the reference diode, thus decreasing the output voltage of the reference diode to compensate for the negative temperature characteristic of the reference diode, which increases when the temperature falls. The output voltage fine-tuning circuit uses a voltage divider circuit, adjusting the output voltage of the reference diode by adjusting the resistance of the voltage divider resistors to achieve the set accuracy. Therefore, this invention solves the problem that the output voltage accuracy and voltage temperature coefficient of the reference voltage source in the prior art cannot be simultaneously met. Attached Figure Description

[0017] Figure 1 It is a bandgap reference voltage source;

[0018] Figure 2 This is the schematic diagram of the LTZ1000 reference voltage source chip;

[0019] Figure 3 This is a schematic diagram of the reference voltage source for temperature compensation of this utility model. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be described in a clear and complete manner below with reference to the accompanying drawings and embodiments.

[0021] The present invention is based on the fact that the temperature-compensated reference voltage source includes a reference voltage regulator circuit, a temperature compensation circuit, and an output voltage fine-tuning circuit. The reference diode of the reference voltage regulator circuit is used to provide a stable output voltage. The temperature compensation circuit adjusts the current supplied to the reference diode according to changes in the environment to compensate for the negative temperature characteristics of the reference diode. Then, the output voltage of the reference diode is adjusted by adjusting the resistance value of the voltage divider resistor of the output voltage fine-tuning circuit so that the output voltage reaches the set accuracy.

[0022] An example of a temperature-compensated reference voltage source:

[0023] like Figure 3The diagram shows a schematic of a temperature-compensated reference voltage source according to this invention. It mainly includes a power supply circuit, a reference voltage regulator circuit, a temperature compensation circuit, and an output voltage fine-tuning circuit. The power supply circuit provides operating power to the reference voltage source circuit. The reference voltage regulator circuit includes a reference diode, which is connected to the output terminal of the power supply circuit through the temperature compensation circuit to provide a stable output voltage. The temperature compensation circuit adjusts the current supplied to the reference diode according to the ambient temperature to compensate for the temperature characteristics of the reference diode's output voltage, ensuring that the temperature coefficient of the output voltage is less than 1ppm / ℃ within the operating temperature range of a standard energy meter (between 10℃ and 40℃), meeting the temperature coefficient requirement. The output voltage fine-tuning circuit uses a voltage divider circuit. By adjusting the resistance value of the voltage divider resistor, the output voltage of the reference diode is adjusted, providing high-precision output to the subsequent circuits, achieving an output voltage accuracy of 0.001%, meeting the output voltage accuracy requirement. The specific working principle is as follows:

[0024] Power supply circuit: Implemented by a low-noise, high-PSRR domestically produced LDO: GM1200 chip. Its output voltage is set by RSET, which is a 100kΩ metal film resistor with 0.1% accuracy and a temperature coefficient of 25ppm / ℃. The LDO's input voltage VSS is 12V, and the output DC voltage is 10V. The 10V DC output provides a stable power supply for the subsequent reference diode.

[0025] The reference voltage regulator circuit is implemented using a domestic Zener reference diode 2DW14. Its output voltage regulation value is between 5.9V and 6.5V, with a typical value of 6.2V and a maximum current of 30mA. The temperature characteristic of its output voltage is -5ppm / ℃. In this embodiment, the current supplied to the reference diode Z1 is approximately (10V-6.2V) / 500kΩ≈8mA (where 500kΩ is the resistance value of R1).

[0026] Temperature compensation circuit: A temperature compensation resistor network is formed by a negative temperature coefficient thermistor NTC1, resistor R1 (first general-purpose resistor), and resistor R2 (second general-purpose resistor). The input of this temperature compensation resistor network is connected to the output of the power supply circuit, and the output of the temperature compensation resistor network is connected to the reference voltage regulator circuit. NTC1 is 10kΩ with a thermal index B of 3435; R1 is a 500kΩ metal foil resistor with a resistance accuracy of 0.01% and a temperature coefficient of 5ppm / ℃; R2 is a metal film resistor, whose resistance value is fine-tuned according to the temperature characteristics of the reference voltage regulator circuit output. (The reason why R1 uses a metal foil resistor and R2 uses a metal film resistor is mainly because metal foil resistors have good stability and temperature characteristics, but are more expensive. Therefore, using a metal foil resistor for R1 provides a stable operating current to the reference diode Z1, while using a metal film resistor for R2 saves cost and allows for fine-tuning of the operating current of the reference diode.) When the ambient temperature varies between 10℃ and 40℃, the resistance of the temperature compensation resistor network varies between 488.5Ω and 473Ω. As the temperature rises, the resistance of the temperature compensation resistor network decreases, increasing the current supplied to the reference voltage regulator circuit, thus increasing the output voltage of the reference voltage regulator circuit. This compensates for the negative temperature coefficient of the reference diode, which causes its voltage to decrease as the temperature rises, ensuring that the output voltage of the reference diode is less than a temperature coefficient of 1ppm / ℃. Conversely, as the temperature decreases, the resistance of the temperature compensation resistor network increases, decreasing the current supplied to the reference voltage regulator circuit, thus decreasing the output voltage of the reference voltage regulator circuit. This compensates for the negative temperature coefficient of the reference diode, which causes its voltage to increase as the temperature decreases, ensuring that the output voltage of the reference diode is less than a temperature coefficient of 1ppm / ℃.

[0027] As another implementation method, the temperature compensation circuit can also be implemented using only a negative temperature coefficient thermistor (NTC), and its working principle is similar to that of the temperature compensation circuit mentioned above.

[0028] The output voltage fine-tuning circuit consists of upper voltage divider resistors R3 and R4 and lower voltage divider resistors R5 to R7. The upper voltage divider resistors R3 and R4 are connected in parallel; adjusting their parallel values ​​adjusts the upper voltage divider resistance. The lower voltage divider resistors R5 and R6 are connected in parallel and then in series with R7; adjusting the parallel resistance of R5 and R6, as well as the resistance of the series resistor with R7, adjusts the lower voltage divider resistance. The upper and lower voltage divider circuits are connected in series, and their series connection point is the output terminal of the output voltage fine-tuning circuit. Through fine adjustment of R3 to R7, the 6.2V output voltage of the reference diode can be adjusted to 0.001% of its rated output value, such as 3.3V. Alternatively, other voltage divider circuit structures can be used as other implementation methods.

[0029] Furthermore, to stabilize the operating temperature of the reference diode at around 45°C, this embodiment also includes a 45°C constant temperature circuit. This circuit is attached to the copper substrate along with the reference diode. The constant temperature circuit includes a temperature sampling circuit and a heating circuit. The temperature sampling circuit collects the temperature of the copper substrate, and the heating circuit adjusts the temperature of the copper substrate based on the temperature collected by the temperature sampling circuit, ensuring that the copper substrate circuit operates at 45°C ± 0.1°C, thereby providing a stable operating environment for the reference diode. Alternatively, a temperature controller or heat sink can be used to achieve constant temperature control.

[0030] In the output voltage fine-tuning circuit, considering the need to provide a large current output to drive the subsequent load, this embodiment also includes an output drive circuit. The output drive circuit is implemented by a non-inverting follower U1 composed of a domestically produced low-noise operational amplifier SGM8557. One input terminal of the operational amplifier is connected to the output terminal of the voltage divider circuit, and the other input terminal is connected to the output terminal of the operational amplifier. The output terminal of the operational amplifier is connected to the subsequent circuit. Its function is to isolate the preceding circuit and provide a 30mA drive current for the subsequent circuit.

Claims

1. A temperature-compensated reference voltage source, comprising a power supply circuit, said power supply circuit being used to supply power to a reference voltage source circuit, characterized in that, It also includes a reference voltage regulator circuit, a temperature compensation circuit, and an output voltage fine-tuning circuit. The reference voltage regulator circuit includes a reference diode, which is connected to the output terminal of the power supply circuit through the temperature compensation circuit to provide a stable output voltage. The temperature compensation circuit is used to adjust the current supplied to the reference diode according to the ambient temperature to compensate for the temperature coefficient of the reference diode. The output voltage fine-tuning circuit adopts a voltage divider circuit, and the output voltage of the reference diode is adjusted by adjusting the resistance value of the voltage divider resistor on the voltage divider circuit to achieve the set accuracy.

2. The temperature-compensated reference voltage source according to claim 1, characterized in that, The temperature compensation circuit includes a thermistor with a negative temperature coefficient.

3. The temperature-compensated reference voltage source according to claim 2, characterized in that, The temperature compensation circuit also includes a first ordinary resistor and a second ordinary resistor. The negative temperature coefficient thermistor is connected in series with the second ordinary resistor and then in parallel across the first ordinary resistor. The first ordinary resistor is connected to the output terminal of the power supply circuit. The first ordinary resistor is a metal foil resistor and the second ordinary resistor is a metal film resistor.

4. The temperature-compensated reference voltage source according to claim 1, characterized in that, The voltage divider circuit includes an upper voltage divider circuit and a lower voltage divider circuit, which are connected in series, and the connection point of the upper and lower voltage divider circuits is the output terminal of the voltage divider circuit.

5. The temperature-compensated reference voltage source according to claim 4, characterized in that, The upper voltage divider circuit consists of two ordinary resistors connected in parallel; the lower voltage divider circuit consists of two ordinary resistors connected in parallel and then connected in series with one ordinary resistor.

6. The temperature-compensated reference voltage source according to claim 1, characterized in that, It also includes a temperature control circuit, which is attached to the reference diode on a copper substrate. The temperature control circuit is used to control the temperature of the copper substrate on which the reference diode is attached, so that the reference diode operates in a constant temperature environment.

7. The temperature-compensated reference voltage source according to claim 6, characterized in that, The constant temperature circuit includes a temperature sampling circuit and a heating circuit. The temperature sampling circuit is used to collect the temperature of the copper substrate, and the heating circuit is used to adjust the temperature of the copper substrate according to the temperature collected by the temperature sampling circuit, so that the reference diode operates in a constant temperature environment.

8. The temperature-compensated reference voltage source according to claim 1, characterized in that, It also includes an output drive circuit. The output drive circuit includes an operational amplifier, one input terminal of which is connected to the output terminal of the voltage divider circuit. The output of the operational amplifier is connected to the subsequent circuit, providing drive current to the subsequent circuit.

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