Amplifier circuits, power analyzers and measuring devices

Abstract

The present application discloses an amplifier circuit, a power analyzer and a measuring device. The amplifier circuit includes an operational amplifier, a voltage divider network and a feedback network. The operational amplifier includes a non-inverting input node, an inverting input node and an output node, the non-inverting input node is coupled to a reference voltage; the voltage divider network is coupled between an input signal and an inverting input node, the voltage divider network includes a receiving node, an intermediate node, a first input resistor, a first input capacitor and a second input capacitor, the receiving node is used to receive an input signal, the intermediate node is coupled to the inverting input node, the first input resistor and the first input capacitor are coupled in parallel between the receiving node and the intermediate node, and the second input capacitor is coupled in series between the intermediate node and the reference voltage; the feedback network is coupled between the inverting input node and the output node.

Description

Technical Field

[0001] The present application relates to an electronic circuit, and more particularly to an amplifier circuit and a power analyzer and a measuring device comprising the amplifier circuit. Background Art

[0002] Power analyzers can be used to measure power parameters of power conversion devices such as motors, frequency converters, transformers, etc., such as active power, reactive power, or apparent power. Power analyzers usually include an input stage circuit to convert the high voltage signal of the device under test into a lower voltage signal, which is then input into the analysis circuit for analysis. The structure of the input stage circuit significantly affects the performance of the power analyzer. Summary of the invention

[0003] One of the purposes of the present application is to provide an amplifier circuit with a simple structure.

[0004] According to one aspect of the present application, an amplifier circuit is provided, which includes: an operational amplifier, the operational amplifier including a non-inverting input node, an inverting input node and an output node, the non-inverting input node being coupled to a reference voltage; a voltage divider network, the voltage divider network being coupled between an input signal and the inverting input node, the voltage divider network including: a receiving node, the receiving node being used to receive an input signal; an intermediate node, the intermediate node being coupled to the inverting input node; a first input resistor and a first input capacitor, the first input resistor and the first input capacitor being coupled in parallel between the receiving node and the intermediate node; and a second input capacitor, the second input capacitor being coupled between the intermediate node and the reference voltage; and a feedback network, the feedback network being coupled between the inverting input node and the output node.

[0005] In some embodiments, the feedback network includes one or more feedback branches, each of the feedback branches is coupled between the inverting input node and the output node.

[0006] In some embodiments, the feedback network includes at least one feedback branch including a feedback resistor and a feedback capacitor coupled in parallel to each other.

[0007] In some embodiments, the at least one feedback branch further includes a switch connected in series with the parallel coupled feedback resistor and feedback capacitor.

[0008] In some embodiments, the feedback network includes at least one feedback branch, and the at least one feedback branch includes a switch.

[0009] In some embodiments, the voltage divider network further includes: a second input resistor coupled between the intermediate node and the inverting input node.

[0010] In some embodiments, a product of a capacitance value of the first input capacitor and a resistance value of the first input resistor is equal to a product of a capacitance value of the second input capacitor and a resistance value of the second input resistor.

[0011] In some embodiments, the resistance value of the second input resistor is less than 10% of the resistance value of the first input resistor.

[0012] According to another aspect of the present application, a power analyzer is provided, and the power analyzer includes the amplification circuit as described in the above aspect.

[0013] According to another aspect of the present application, a measuring device is further provided, wherein the measuring device comprises the amplifying circuit as described in the above aspect.

[0014] The above is an overview of the present application, which may be simplified, summarized, and omitted in detail. Therefore, those skilled in the art should recognize that this section is only illustrative and is not intended to limit the scope of the present application in any way. This summary section is neither intended to determine the key features or essential features of the claimed subject matter, nor is it intended to be used as an auxiliary means to determine the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Through the detailed description made below in conjunction with the accompanying drawings and the attached claims, those skilled in the art will more fully and clearly understand the above and other features of the present application. It is understood that these drawings and detailed descriptions only depict several exemplary embodiments of the present application and should not be considered as limiting the scope of the present application. By referring to the accompanying drawings, the content of the present application will be more clearly and detailed.

[0016] Figure 1 FIG. 1 shows a circuit structure diagram of an amplifier circuit 100 according to an embodiment of the present application. DETAILED DESCRIPTION

[0017] In the following detailed description, reference is made to the accompanying drawings which form a part of the specification. In the drawings, similar symbols generally represent similar components unless the context indicates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not intended to be limiting. Other embodiments may be adopted, and other changes may be made without departing from the spirit or scope of the subject matter of the present application. It is understood that various configurations, substitutions, combinations, and designs of various aspects of the present application generally described in the present application and illustrated in the drawings may be made, all of which explicitly constitute a part of the present application.

[0018] refer to Figure 1 , Figure 1 The circuit structure diagram of the amplifier circuit 100 according to an embodiment of the present application is schematically shown.

[0019] like Figure 1 As shown, the amplifier circuit 100 includes an operational amplifier 102, a voltage divider network 104 and a feedback network 106. The operational amplifier 102 includes a non-inverting input node (+), an inverting input node (-) and an output node. In some embodiments, the operational amplifier 102 can be an operational amplifier based on a bipolar junction transistor, an operational amplifier based on a field effect transistor, or an operational amplifier implemented based on other suitable devices.

[0020] The voltage divider network 104 is coupled to the input signal V in and the inverting input node of the operational amplifier 102 for the input signal V in The voltage divider network 104 can sample the input signal V with a voltage divider coefficient corresponding to its circuit structure. in The voltage is divided and the amplitude is smaller than the input signal V in The sampling signal V s .

[0021] The feedback network 106 is coupled between the inverting input node and the output node of the operational amplifier 102, and together with the voltage divider network 104, the operational amplifier 102 is configured as an inverting amplifier circuit. Compared with the in-phase amplifier circuit, the inverting amplifier circuit can more easily achieve a circuit amplification gain less than 1, and there is no need to add a switch or relay with a higher withstand voltage in the voltage divider network 104 in order to switch the circuit amplification gain, which makes the structure of the amplifier circuit 100 simple and the volume smaller. For a power analyzer or similar electrical measuring device, the smaller circuit amplification gain of the inverting amplifier circuit can reduce the input voltage of a larger amplitude (for example, an AC voltage of 220V) to an amplitude range suitable for the electronic measuring device (for example, less than or equal to 12V, or less than or equal to 5V); in addition, when switching such a smaller circuit amplification gain, the inverting amplifier circuit only needs a small low-voltage switch; therefore, the operational amplifier using the inverting amplifier circuit structure is particularly suitable for portable electronic measuring devices. In addition, the smaller circuit amplification gain is also conducive to achieving a wide bandwidth output.

[0022] In some embodiments, the feedback network 106 may include one or more feedback branches, and each feedback branch is individually coupled between the inverting input node and the output node. When the feedback network 106 includes multiple feedback branches, the multiple feedback branches are connected in parallel with each other. These feedback branches may have the same or different feedback coefficients. Optionally, each feedback branch may be coupled with a switch for controlling the closing or opening of the feedback branch. In this way, by controlling the closing or opening state of the switch of each feedback branch, the circuit gain of the amplifier circuit 100 can be adjusted to adapt to the input signal V in In some embodiments, each feedback branch may include a feedback resistor and a feedback capacitor coupled in parallel to each other, wherein the feedback resistor may be used to determine the feedback gain of the feedback branch, and the feedback capacitor may be used to: low-pass filter to filter out high-frequency noise that may affect the measurement; ensure the stability of the amplification circuit; and cooperate with the second input capacitor C which will be described in detail below. in2 Together, they ensure the flatness of the frequency response characteristics of the amplifier circuit. In some embodiments, the feedback capacitor may have a smaller capacitance value, such as 1 picofarad to 200 picofarads, or other suitable capacitance values. In some embodiments, the resistance value of the feedback resistor may be 100 ohms to 500 kiloohms, or other suitable resistance values.

[0023] Specifically, Figure 1 As shown, the voltage divider network 104 includes a receiving node IN, an intermediate node IMN, a first input resistor R in1 , the first input capacitor C in1 and the second input capacitor C in2Among them, the receiving node IN is used to receive the input signal V in ; The intermediate node IMN is coupled to the inverting input node of the operational amplifier 102; The first input resistor R in1 and the first input capacitor C in1 The second input capacitor C is coupled in parallel between the receiving node IN and the intermediate node IMN; in1 The intermediate node IMN and the reference voltage V ref The feedback network 106 is coupled between the inverting input node and the output node OUT of the operational amplifier 102. Figure 1 As shown, the feedback network 106 includes one or more feedback branches, each of which includes feedback resistors R coupled in parallel with each other. f and feedback capacitor C f , and further includes a switch S for controlling the closing or opening of the feedback branch. In some embodiments, the in-phase input node is coupled to a reference voltage V ref . Figure 1 The amplifier circuit shown can be based on the input signal V in The voltage generates an output signal V out , where the second input capacitor C in2 It plays a major role in obtaining a flat frequency response characteristic, and its capacitance value is usually relatively large (for example, several thousand picofarads or other suitable capacitance values). It can be seen that the output of the operational amplifier 102 does not directly drive the second input capacitor C in2 , which can improve the stability of the amplifier circuit 100 itself. In addition, the amplifier circuit 100 has only a single-stage amplification, which is not only conducive to reducing the circuit volume, but also can effectively avoid the noise introduced into the circuit by multi-stage amplification.

[0024] For an AC input signal V in The voltage division coefficient of the voltage division network 104 depends on the first input capacitor C in1 and the second input capacitor C in2 Specifically, the sampling signal V generated at the intermediate node IMN s It can be expressed by the following equation (1):

[0025]

[0026] exist Figure 1 In the illustrated embodiment, the voltage divider network 104 further includes a second input resistor R in2 , the second input resistor R in2is coupled between the intermediate node IMN and the inverting input node of the operational amplifier 102. Due to the virtual short characteristic of the operational amplifier, the non-inverting input node and the inverting input node can be considered to have the same potential, that is, the potential of the non-inverting input node is equal to the reference voltage V ref Based on this, assuming that the reference voltage V ref When is zero, the circuit transfer function of the amplifier circuit 100 is expressed by the following equation (2) (the value of the feedback capacitor in the feedback network is not considered):

[0027]

[0028] Among them, R fi Indicates the resistance value of the feedback resistor coupled in the selected feedback branch. Depending on the specific circuit operation, R fi Can be the selected R f1 To R fn One of these feedback resistors R f1 To R fn Parallel combination (multiple feedback branches are selected to be closed).

[0029] It can be seen that for a high frequency AC input signal, the circuit amplification gain of the amplifier circuit 100 is affected by the second input resistor R in2 The resistance value of the second input resistor R is affected, and the larger the resistance value, the smaller the circuit amplification gain. In some embodiments, the second input resistor R in2 The resistance value of the second input resistor R in2 The resistance value is smaller than the first input resistor R in1 In some embodiments, the first input resistor R in1 The resistance value of the second input resistor R in2 The resistance value of may be 1 kilo-ohm to 500 kilo-ohm (eg, 10 kilo-ohm), or other suitable resistance values.

[0030] Since the inverting input node is considered to be coupled to the reference voltage V ref , also assuming that V ref When the input impedance R of the amplifier circuit 100 is zero, in It is expressed by the following equation (3):

[0031]

[0032] In some embodiments, the first input capacitor C in1 The capacitance value and the first input resistor R in1 The product of the resistance values ​​of the second input capacitor C in2The capacitance value and the second input resistor R in2 This can reduce the number of poles in the amplifier circuit 100. From equation (3), we know that the input impedance R in The change with frequency is flat, that is, the frequency response curve of the amplifier circuit 100 is made flatter. In addition, when the first input capacitor C in1 The capacitance value and the first input resistor R in1 The product of the resistance values ​​of the second input capacitor C in2 The capacitance value and the second input resistor R in2 When the product of the resistance values ​​is obtained, it can be seen from the above equation (2) that the gain H of the amplifier circuit 100 is equal to Therefore, the gain of the amplifier circuit 100 is flat.

[0033] In some embodiments, corresponding to the first input resistor R in1 and the second input resistor R in2 The resistance value of the first input capacitor C in1 The capacitance value of the second input resistor C in2 The capacitance value of may be 100 pico-farads to 50 kilo-farads (eg, 1000 pico-farads), or other suitable capacitance values.

[0034] In some embodiments, the amplifier circuit shown in the embodiment of the present application can be used in a power analyzer or other measuring device. In particular, the amplifier circuit shown in the embodiment of the present application can be used in a portable power analyzer or measuring device, for example, as an input stage circuit of the portable power analyzer or measuring device to sample voltage. It can be understood that for a power analyzer, in addition to Figure 1 The amplifier circuit for sampling voltage shown in the figure may also include a current sampling circuit for sampling current, which may be, for example, an inductor or other similar current sampling or sensing circuit. By calculating the sampled current and the sampled voltage, the power analyzer may obtain the power of the device under test.

[0035] Those of ordinary skill in the art can understand and implement other changes to the disclosed embodiments by studying the specification, the disclosed content, the drawings and the appended claims. In the claims, the word "comprising" does not exclude other elements and steps, and the words "a" and "an" do not exclude the plurality. In the actual application of this application, a part may perform the functions of multiple technical features cited in the claims. Any reference signs in the claims should not be construed as limiting the scope.

Claims

1. An amplifier circuit, characterized in that: The amplifying circuit comprises: an operational amplifier, the operational amplifier comprising a non-inverting input node, an inverting input node, and an output node, the non-inverting input node being coupled to a reference voltage; A voltage divider network is coupled between the input signal and the inverting input node, and the voltage divider network comprises: A receiving node, the receiving node is used to receive an input signal; an intermediate node coupled to the inverting input node; a first input resistor and a first input capacitor coupled in parallel between the receiving node and the intermediate node; a second input capacitor coupled between the intermediate node and the reference voltage; and a second input resistor coupled between the intermediate node and the inverting input node, wherein a product of a capacitance value of the first input capacitor and a resistance value of the first input resistor is equal to a product of a capacitance value of the second input capacitor and a resistance value of the second input resistor; and A feedback network is coupled between the inverting input node and the output node.

2. The amplifier circuit according to claim 1, characterized in that: The feedback network includes one or more feedback branches, each of which is coupled between the inverting input node and the output node.

3. The amplifier circuit according to claim 1, characterized in that: The feedback network includes at least one feedback branch including a feedback resistor and a feedback capacitor coupled in parallel to each other.

4. The amplifier circuit according to claim 3, characterized in that: The at least one feedback branch further includes a switch connected in series with the parallel-coupled feedback resistor and feedback capacitor.

5. The amplifier circuit according to claim 1, characterized in that: The feedback network includes at least one feedback branch, and the at least one feedback branch includes a switch.

6. The amplifier circuit according to claim 1, characterized in that: The resistance value of the second input resistor is less than 10% of the resistance value of the first input resistor.

7. A power analyzer, characterized in that: The power analyzer comprises the amplification circuit according to any one of claims 1 to 6.

8. A measuring device, characterized in that: The measuring device comprises an amplifying circuit as claimed in any one of claims 1 to 6.

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