Electric energy meter and voltage reference diode power supply circuit

Abstract

The invention relates to an electric energy meter and a voltage reference diode power supply circuit, and belongs to the technical field of electric energy meters. The voltage bootstrap circuit and the temperature compensation circuit are additionally arranged in an existing power supply circuit, a stable power source is provided for the voltage reference diode through the voltage bootstrap circuit, and output drift, caused by temperature changes, of the voltage reference diode is corrected through the temperature compensation circuit; the change of the voltage output value caused by the change of the working current of the voltage reference diode due to the change of the environment temperature is compensated, so that the problem that the voltage reference diode cannot meet the requirements of the electric energy meter due to the fluctuation of the output voltage is solved.

Description

Technical Field

[0001] The invention relates to an electric energy meter and a voltage reference diode power supply circuit, belonging to the technical field of electric energy meters. Background Art

[0002] The 0.01-level standard energy meter is a standard instrument for energy meter traceability. Its voltage sampling circuit and current sampling circuit are converted into digital signals through ADC (analog-to-digital converter). The post-signal processing part runs the energy measurement algorithm to obtain data and information related to the energy. The sampling accuracy of the ADC of the standard energy meter depends on the reference voltage source that provides a quantitative comparison benchmark for it. The accuracy and stability of the reference voltage source play a decisive role in the accuracy and stability of the 0.01-level standard energy meter.

[0003] The reference voltage source circuit of the existing standard electric energy meter is as follows: Figure 1 As shown, VSS is a DC power supply, and Z1 is a voltage reference diode. Its working principle is: the input DC power supply VSS is converted into a stable DC voltage through a low-noise, high-PSRR linear voltage regulator (LDO). This voltage is applied to the voltage reference diode Z1 after passing through the R1 resistor. When the voltage reference diode Z1 works in the reverse breakdown region, the voltage across it is a stable value that basically does not change with temperature. This voltage is provided to the ADC conversion circuit in the electric energy meter as a reference voltage. However, when the ambient temperature changes, the output voltage of the LDO and the resistance value of R1 will change, thereby causing the working current of Z1 to change. For example, when the working current changes by 1 microampere, the Z1 voltage regulation output value changes by ΔV=1μA*Z1's dynamic impedance. If the network impedance of Z1 is 10 ohms, in a 0.01-level high-precision standard electric energy meter, this output voltage fluctuation does not meet the performance index requirements, and thus cannot meet the needs of the electric energy meter. Summary of the invention

[0004] The purpose of the present invention is to provide an electric energy meter and a voltage reference diode power supply circuit to solve the problem that the current voltage reference diode cannot meet the needs of the electric energy meter due to output voltage fluctuations.

[0005] In order to solve the above technical problems, the present invention provides a voltage reference diode power supply circuit, which includes a voltage source voltage stabilizing circuit for providing a stable voltage, and also includes a voltage bootstrap circuit and a temperature compensation circuit. The voltage bootstrap circuit includes an operational amplifier, the second input end of the operational amplifier is connected to the temperature compensation circuit, the first input end of the operational amplifier is connected to the output end of the voltage source voltage stabilizing circuit, the output end of the operational amplifier is used to connect to the voltage reference diode through a first resistor, the first input end of the operational amplifier is also used to connect the voltage reference diode, and the second input end of the operational amplifier is also connected between the output end of the operational amplifier and the first resistor.

[0006] Furthermore, the temperature compensation circuit includes a thermistor and a second resistor connected in parallel. After the thermistor and the second resistor are connected in parallel, one end is grounded and the other end is connected to the second input terminal of the amplifier.

[0007] Furthermore, a voltage regulator tube is arranged between the first input terminal of the operational amplifier and the output terminal of the voltage source voltage regulator circuit.

[0008] Furthermore, a third resistor is connected between the voltage regulator and the first input terminal of the operational amplifier.

[0009] Furthermore, the first input terminal is a non-inverting input terminal, and the second input terminal is an inverting input terminal.

[0010] The present invention also provides an electric energy meter, comprising a voltage reference diode and a voltage reference diode power supply circuit for powering the voltage reference diode, wherein the voltage reference diode power supply circuit comprises a voltage source voltage stabilizing circuit, a voltage bootstrap circuit and a temperature compensation circuit, wherein the voltage bootstrap circuit comprises an operational amplifier, wherein the second input terminal of the operational amplifier is connected to the temperature compensation circuit, the first input terminal of the operational amplifier is connected to the output terminal of the voltage source voltage stabilizing circuit, the output terminal of the operational amplifier is connected to the voltage reference diode via a first resistor, the first input terminal of the operational amplifier is also used to connect the voltage reference diode, and the second input terminal of the operational amplifier is also connected between the output terminal of the operational amplifier and the first resistor.

[0011] Furthermore, the temperature compensation circuit includes a thermistor, a second resistor is connected in parallel at both ends of the thermistor, and after the thermistor and the second resistor are connected in parallel, one end is grounded and the other end is connected to the second input end of the amplifier.

[0012] Furthermore, a voltage regulator tube is arranged between the first input terminal of the operational amplifier and the output terminal of the voltage source voltage regulator circuit.

[0013] Furthermore, a third resistor is connected between the voltage regulator tube and the first input terminal of the operational amplifier.

[0014] Furthermore, the first input terminal is a non-inverting input terminal, and the second input terminal is an inverting input terminal.

[0015] The beneficial effects of the present invention are as follows: as an improved invention, the present invention adds a voltage bootstrap circuit and a temperature compensation circuit to the existing power supply circuit, provides a stable power supply for the voltage reference diode through the voltage bootstrap circuit, corrects the output drift of the voltage reference diode caused by temperature changes through the temperature compensation circuit, and compensates for the change in voltage output value caused by the change in working current of the voltage reference diode caused by the change in ambient temperature, thereby solving the problem that the voltage reference diode does not meet the needs of the electric energy meter due to output voltage fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of an existing voltage reference diode power supply circuit; Figure 2 It is a schematic diagram of a voltage reference diode power supply circuit of the present invention. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0018] The present invention adopts a voltage bootstrap method to provide a stable voltage output to a voltage reference diode, and increases a temperature compensation voltage to compensate for changes in the voltage output value caused by changes in the working current of the voltage reference diode caused by changes in ambient temperature, thereby solving the problem that the voltage reference diode does not meet the needs of the electric energy meter due to output voltage fluctuations.

[0019] Voltage reference diode power supply circuit embodiment The voltage reference diode power supply circuit of the present invention is as follows Figure 2 As shown, it includes a voltage source voltage stabilizing circuit, a voltage bootstrap circuit and a temperature compensation circuit. The voltage bootstrap circuit includes an operational amplifier. The second input terminal of the operational amplifier is connected to the temperature compensation circuit. The first input terminal of the operational amplifier is connected to the output terminal of the voltage source voltage stabilizing circuit. The output terminal of the operational amplifier is used to connect to the cathode of the voltage reference diode through a first resistor. The first input terminal of the operational amplifier is also used to connect the voltage reference diode. The second input terminal of the operational amplifier is also connected between the output terminal of the operational amplifier and the first resistor.

[0020] Specifically, the voltage source voltage regulator circuit adopts a low-noise, high-PSRR linear regulated power supply (LDO). The DC power supply VSS is converted into a stable DC voltage through the LDO. The DC voltage is applied to the voltage reference diode Z1 through the voltage bootstrap circuit to provide normal operating current for the voltage reference diode Z1. The voltage bootstrap circuit adopts an operational amplifier U1, the in-phase input terminal of the operational amplifier U1 is connected to the output terminal of the LDO through a resistor R1 and a voltage regulator tube Z2, and the in-phase input terminal of the operational amplifier U1 is also connected to the cathode of the voltage reference diode Z1; the inverting input terminal of the operational amplifier U1 is connected to a temperature compensation circuit, and the temperature compensation circuit includes a parallel resistor R2 and a thermistor NTC (using a negative temperature coefficient), and the resistor R2 and the thermistor NTC are connected in parallel, one end of which is grounded, and the other end is connected to the inverting input terminal of the operational amplifier U1, and the inverting input terminal of the operational amplifier U1 is also connected to the output terminal of the operational amplifier U1 through a resistor R4 to form a negative feedback circuit of the operational amplifier; the output terminal of the operational amplifier U1 is connected to the cathode of the voltage reference diode Z1 through a resistor R3, the anode of the voltage reference diode Z1 is grounded, and the voltage V on the voltage reference diode Z1 RFE The voltage reference diode Z1 in this embodiment is a Zener voltage reference diode, which can output a stable voltage value when working in the reverse breakdown region.

[0021] The working principle of the voltage reference diode power supply circuit is as follows: when powered on normally, the output voltage of the LDO is V1. After V1 passes through the voltage regulator Z2 and the resistor R1, the voltage drops to V1-Vz2-VR1. That is, at this time, the voltage at the non-inverting input terminal of the operational amplifier U1 is V1-Vz2-VR1, and the voltage of the voltage reference diode Z1 is also V1-Vz2-VR1, where Vz2 is the voltage regulation value of the voltage regulator Z2, and VR1 is the voltage drop of the resistor R1.

[0022] After the power supply is powered on, when the voltage of the voltage reference diode Z1 has not reached its breakdown voltage value, the current flowing through the resistor R1 is relatively small, that is, the voltage drop across R1 can be ignored. The voltage across the voltage reference diode Z1 is V1 - Vz2. If the voltage reaches the breakdown voltage value of the voltage reference diode Z1, the voltage reference diode Z1 enters the breakdown working area. At this time, the current flowing through the voltage reference diode Z1 increases, the current flowing through R1 also increases, and the voltage drop across R1 also increases. By setting the resistance value of the resistor R1, it can be made that V1 - VR1 < Vz2. In this way, the voltage regulator diode Z2 is in the cut-off area. At this time, the output voltage of the LDO is disconnected from the subsequent stage. In this way, the voltage value VREF of the voltage reference diode Z1 is input to the non-inverting input terminal of the operational amplifier U1. The output voltage of the operational amplifier U1 is applied to both ends of the voltage reference diode Z1 after passing through R3, that is, the output of U1 provides a power supply input for the voltage reference diode Z1 after passing through R3. The output of the operational amplifier U1 forms a negative feedback loop through R4, the resistor R2 and the thermistor NTC. The output of the operational amplifier U1 and the output VREF of the voltage reference diode Z1 form a positive feedback loop. The negative feedback loop and the positive feedback loop act together on the power supply loop of the voltage reference diode Z1 to make the circuit work in a stable state.

[0023] After the voltage reference diode Z1 is in the voltage stabilization state, its output voltage VREF provides a stable reference voltage for the non-inverting input terminal (+) of the operational amplifier U1. The voltage at the inverting input terminal (-) of the operational amplifier U1 is in a virtual short state with the voltage at the non-inverting input terminal, that is, the voltages at the two input terminals of the operational amplifier U1 are equal. At this time, the output voltage of the operational amplifier U1 is VREF * (1 + R4 / (R2 / / NTC)). In this way, the voltage applied across the resistor R3 is: VREF * (1 + R4 / (R2 / / NTC)) - VREF. Since the working condition of the minimum temperature coefficient (or zero temperature coefficient) of the reference diode Z1 is related to the current flowing through Z1, at a specific current point, the temperature coefficient of the reference diode Z1 is the smallest. At this time, by setting the resistance value of R3, the current value flowing through Z1 can be made to be in the working condition with the smallest temperature coefficient. The 2DW14A reference diode is selected in this embodiment. The working condition with the smallest temperature coefficient is when the current flowing through it is about 4 mA. Therefore, in this embodiment, by setting the resistance value of R3, the current flowing through it can meet the condition of the smallest temperature coefficient of the reference diode Z1.

[0024] Since the resistance value of NTC is relatively limited, and its resistance change cannot be accurately adjusted, the temperature compensation circuit in this embodiment is implemented by connecting the resistor R2 in parallel with the thermistor NTC. After connecting NTC and R2 in parallel, the resistance range and temperature control range can be accurately adjusted, which is easy to match with the circuit. In general, the temperature characteristic of the voltage reference diode Z1 output (2DW14) is a negative temperature coefficient, and its output voltage VREF decreases as the temperature rises. When R2 is connected in parallel with the resistor NTC (negative temperature coefficient resistor), the resistance of R2 / / NTC decreases as the temperature rises. Since the output voltage of U1 is VREF*(1+R4 / (R2 / / NTC)), as the temperature rises, the output voltage of U1 increases, causing the voltage across R3 to rise, and the current flowing through R3 and Z1 to increase. When the current flowing through Z1 increases, its output voltage VREF increases, thereby compensating for the change in output voltage caused by temperature change.

[0025] Through the voltage reference diode power supply circuit of the present invention, the power supply of the voltage reference diode is provided by its own output voltage, that is, the voltage bootstrap circuit, which supplies power to itself through U1, thereby improving the stability of the power supply and making its output voltage more stable. In addition, a temperature compensation NTC resistor loop is added to further correct the output drift caused by temperature changes. When the domestic 2DW14 reference diode is used, the reference power supply circuit can achieve the technical indicator of temperature coefficient <5ppm, reaching the performance requirements of 0.01 standard electric energy meter.

[0026] Electricity meter embodiment The electric energy meter of the present invention includes a voltage reference diode and a voltage reference diode power supply circuit for powering the voltage reference diode, wherein the voltage reference diode power supply circuit includes a voltage source voltage stabilizing circuit and a voltage bootstrap circuit, the voltage bootstrap circuit includes an operational amplifier, the second input end of the operational amplifier is connected through a temperature compensation circuit, the first input end of the operational amplifier is connected to the output end of the voltage source voltage stabilizing circuit, the output end of the operational amplifier is connected to the cathode of the voltage reference diode through a first resistor, the first input end of the operational amplifier is connected to, and the second input end of the operational amplifier is also connected between the output end of the operational amplifier and the first resistor. The specific working process of the circuit has been described in detail in the embodiment of the voltage reference diode power supply circuit, and will not be repeated here.

Claims

1. A voltage reference diode power supply circuit, comprising a voltage source voltage stabilizing circuit for providing a stable voltage, characterized in that: It also includes a voltage bootstrap circuit and a temperature compensation circuit. The voltage bootstrap circuit includes an operational amplifier. The second input terminal of the operational amplifier is connected to the temperature compensation circuit. The first input terminal of the operational amplifier is connected to the output terminal of the voltage source voltage stabilizing circuit. The output terminal of the operational amplifier is used to connect to the voltage reference diode through the first resistor. The first input terminal of the operational amplifier is also used to connect to the voltage reference diode. The second input terminal of the operational amplifier is also connected between the output terminal of the operational amplifier and the first resistor.

2. The voltage reference diode power supply circuit according to claim 1, characterized in that: The temperature compensation circuit comprises a thermistor and a second resistor which are arranged in parallel. After the thermistor and the second resistor are connected in parallel, one end is grounded and the other end is connected to the second input end of the amplifier.

3. The voltage reference diode power supply circuit according to claim 1, characterized in that: A voltage regulator tube is also arranged between the first input terminal of the operational amplifier and the output terminal of the voltage source voltage regulator circuit.

4. The voltage reference diode power supply circuit according to claim 3, characterized in that: A third resistor is also connected between the voltage regulator tube and the first input terminal of the operational amplifier.

5. The voltage reference diode power supply circuit according to claim 1, characterized in that: The first input terminal is a non-inverting input terminal, and the second input terminal is an inverting input terminal.

6. An electric energy meter, comprising a voltage reference diode and a voltage reference diode power supply circuit for supplying power to the voltage reference diode, characterized in that: The voltage reference diode power supply circuit includes a voltage source voltage regulator circuit, a voltage bootstrap circuit and a temperature compensation circuit. The voltage bootstrap circuit includes an operational amplifier. The second input end of the operational amplifier is connected to the temperature compensation circuit. The first input end of the operational amplifier is connected to the output end of the voltage source voltage regulator circuit. The output end of the operational amplifier is used to connect to the voltage reference diode through a first resistor. The first input end of the operational amplifier is also used to connect the voltage reference diode. The second input end of the operational amplifier is also connected between the output end of the operational amplifier and the first resistor.

7. The electric energy meter according to claim 6, characterized in that: The temperature compensation circuit comprises a thermistor, two ends of the thermistor are connected in parallel with a second resistor, one end of the thermistor and the second resistor are connected in parallel to the ground, and the other end is connected to the second input end of the amplifier.

8. The electric energy meter according to claim 6, characterized in that: A voltage regulator tube is also arranged between the first input terminal of the operational amplifier and the output terminal of the voltage source voltage regulator circuit.

9. The electric energy meter according to claim 8, characterized in that: A third resistor is also connected between the voltage regulator tube and the first input terminal of the operational amplifier.

10. The electric energy meter according to claim 6, characterized in that: The first input terminal is a non-inverting input terminal, and the second input terminal is an inverting input terminal.

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