High-precision AC voltage DC component detection circuit

Abstract

The invention discloses a high-precision alternating-current voltage direct-current component detection circuit which comprises a capacitance-resistance voltage division circuit, a differential amplification circuit, a second-order RC filter circuit, a voltage following and lifting circuit and an AD voltage clamping circuit which are arranged in sequence. The invention aims to improve the detection precision of the direct-current voltage in the alternating-current output voltage of the energy storage converter and feed back the detected accurate direct-current voltage amplitude to the CPU to carry out closed-loop control on the system output voltage so as to achieve the purpose of reducing the direct-current component in the alternating-current output voltage of the energy storage converter.

Description

Technical Field

[0001] The invention relates to the technical field of AC voltage detection circuits, and in particular to a high-precision AC voltage DC component detection circuit. Background Art

[0002] When the energy storage inverter is operated in off-grid mode, it is used as a voltage source. The DC component in the AC voltage it outputs will have a significant impact on the subsequent power transformer and load equipment. Excessive DC components can cause problems such as DC bias, magnetic saturation, and excessive losses in the transformer and load. Therefore, it is necessary to detect and correct the DC component in the output AC voltage.

[0003] The detection of the DC voltage component in the output AC voltage of the off-grid energy storage converter is a relatively common detection. The existing detection circuit is implemented by a resistor voltage divider circuit + amplifier circuit + filter circuit + signal conditioning circuit. Because the AC voltage output by the converter itself has a large amplitude (above 220Vac), in order to convert the voltage into an amplitude that can be detected by the CPU, the detection circuit needs to first perform a large-scale resistor voltage divider on the converter output voltage, and the voltage divider ratio will reach 100:1 or even higher. In this process, the DC voltage with a very small amplitude (<0.5%Un) will be divided together. The DC voltage amplitude after voltage division will be less than ±20mV, so it is necessary to amplify the DC voltage again to the reasonable detection voltage amplitude range of the CPU (0~3V) and then send it to the CPU for detection. In the entire circuit, the DC voltage is first reduced by a large proportion and then amplified by a large proportion, which makes the detection of the DC voltage have a large error. At the same time, the circuit has poor anti-interference ability because the amplitude of the DC voltage after large-scale voltage division is too small. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a high-precision AC voltage DC component detection circuit to solve the problem of detection error of the DC voltage component of the AC voltage output by the converter, improve the detection accuracy of the DC voltage, and complete the closed-loop control of the output AC voltage through a high-precision DC voltage detection signal, so as to achieve the purpose of reducing the DC voltage component in the output AC voltage.

[0005] In order to solve the above technical problems, the present invention provides a high-precision AC voltage DC component detection circuit, including a capacitor-resistor voltage divider circuit arranged in sequence, including a first resistor, a second resistor and a first capacitor, and adjusting the capacitance of the first capacitor and the resistance of the first resistor and the second resistor can realize the adjustment of the voltage division ratio of the AC voltage, and the DC voltage will not be attenuated, so as to achieve the effect of reducing the AC voltage amplitude but not changing the DC voltage amplitude;

[0006] A differential amplifier circuit includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a second capacitor, a third capacitor, a first operational amplifier, a first diode, and a second diode. The circuit amplification factor is set according to the DC voltage sampling range, and the voltage after the capacitor and resistor voltage divider circuit is scaled proportionally. At the same time, the first diode and the second diode play the role of clamping the amplitude of the common-mode voltage input of the operational amplifier;

[0007] A second-order RC filter circuit, comprising an eighth resistor, a ninth resistor, a fourth capacitor and a fifth capacitor, for filtering out the AC component in the voltage after differential amplification, and retaining only the DC voltage;

[0008] The voltage following and raising circuit includes a tenth resistor, a second operational amplifier, an eleventh resistor, and a twelfth resistor. The DC voltage after being filtered by the second-order RC filter circuit in the previous stage is raised by the follower to raise the voltage to an effective detection voltage range of 0-3V.

[0009] The AD voltage clamping circuit includes a thirteenth resistor, a sixth capacitor, and a third diode, and is used to filter out high-frequency interference signals and clamp the input CPU voltage to prevent abnormal voltage amplitude from damaging the CPU device.

[0010] Furthermore, the input source of the circuit adopts an AC output voltage, and the output end of the circuit is connected to the CPU.

[0011] Furthermore, in the capacitor-resistor voltage divider circuit, the characteristic of the capacitor itself that it passes AC and blocks DC is utilized to generate different equivalent impedances Rac and Rdc for AC voltage and DC voltage, where Rac=1 / (2πfc) and Rdc=∞.

[0012] Beneficial effects of the present invention: The circuit of the present invention utilizes the different impedance characteristics of capacitors to DC voltage and AC voltage to achieve different conversion ratios of AC voltage and DC voltage;

[0013] A larger AC voltage sampling ratio can meet the requirements of high AC voltage input and sampling, while a smaller DC voltage sampling ratio can ensure the detection accuracy of DC voltage. At the same time, since the DC voltage is not attenuated by a large proportion at the front end of the circuit, the subsequent circuit does not need to be amplified again, and the circuit implementation is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural block diagram of the present invention.

[0015] Figure 2 It is a circuit structure diagram of the present invention.

[0016] Explanation of the numbers in the figure: R1, the first resistor; R2, the second resistor; R3, the third resistor; R4, the fourth resistor; R5, the fifth resistor; R6, the sixth resistor; R7, the seventh resistor; R8, the eighth resistor; R9, the ninth resistor; R10, the tenth resistor; R11, the eleventh resistor; R12, the twelfth resistor; R13, the thirteenth resistor; C1, the first capacitor; C2, the second capacitor; C3, the third capacitor; C4, the fourth capacitor; C5, the fifth capacitor; C6, the sixth capacitor; D1, the first diode; D2, the second diode; D3, the third diode; U1, the first operational amplifier; U2, the second operational amplifier. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0020] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0021] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0022] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0023] Reference Figure 1 to Figure 2As shown, an embodiment of a high-precision AC voltage DC component detection circuit of the present invention includes a capacitor-resistor voltage divider circuit arranged in sequence, including a first resistor R1, a second resistor R2 and a first capacitor C1. In the capacitor-resistor voltage divider circuit, the characteristics of the capacitor itself passing AC and blocking DC are utilized to generate different equivalent impedances Rac and Rdc for AC voltage and DC voltage, Rac=1 / (2πfc), Rdc=∞, and the voltage division ratio of the AC voltage can be adjusted by adjusting the capacitance of the first capacitor C1 and the resistance values ​​of the first resistor R1 and the second resistor R2. At the same time, the DC voltage will not be attenuated, thereby achieving the effect of reducing the amplitude of the AC voltage but not changing the amplitude of the DC voltage; a differential amplifier circuit includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a second capacitor C2, a third capacitor C3, a first operational amplifier U1, a first diode D1, and a second diode D2. The circuit amplification factor is adjusted according to the DC voltage. The current voltage sampling range is set, and the voltage after the capacitor-resistor voltage divider circuit is scaled proportionally. At the same time, the first diode D1 and the second diode D2 play the role of clamping the amplitude of the common-mode voltage input of the operational amplifier; the second-order RC filtering circuit includes an eighth resistor R8, a ninth resistor R9, a fourth capacitor C4 and a fifth capacitor C5, which are used to filter out the AC component in the voltage after differential amplification and only retain the DC voltage; the voltage following and lifting circuit includes a tenth resistor R10, a second operational amplifier U2, an eleventh resistor R11, and a twelfth resistor R12. The DC voltage after filtering by the second-order RC filtering circuit in the front stage is raised after the follower, and the voltage is raised to an effective detection voltage range of 0-3V; the AD voltage clamping circuit includes a thirteenth resistor R13, a sixth capacitor C6, and a third diode D3, which are used to filter out high-frequency interference signals and clamp the input CPU voltage to prevent abnormal voltage amplitudes from damaging CPU devices.

[0024] The input source of the circuit adopts an AC output voltage, and the output end of the circuit is connected to the CPU.

[0025] Simple description; Capacitor-resistor voltage divider circuit: It uses capacitor and resistor voltage divider mode, and takes advantage of the characteristics of capacitor itself that it passes AC and blocks DC, so it can effectively divide the AC voltage while completely retaining the DC component in the AC output voltage;

[0026] Differential amplifier circuit: effectively design the differential amplifier circuit ratio according to the amplitude after voltage division and the sampling AD value range;

[0027] Second-order RC filter circuit: The second-order RC filter circuit is used to effectively filter out the AC voltage component in the previous stage sampling voltage, leaving only the DC voltage component;

[0028] Voltage follower circuit: Add a voltage follower circuit to play an isolation and protection role;

[0029] Voltage boost circuit: DC voltage itself has positive and negative amplitudes, and the sampled positive and negative voltages need to be boosted. At this time, all DC voltage sampling values ​​within the detection range are converted into signals within the amplitude of 0-3V and then transmitted to the CPU for sampling;

[0030] AD voltage clamping circuit: If the DC voltage amplitude in the output AC voltage is too large, the detected AD amplitude will be too high and exceed the CPU detection range. Therefore, a voltage clamping circuit is needed to protect the CPU.

[0031] The above-described embodiments are only preferred embodiments for fully illustrating the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or changes made by those skilled in the art based on the present invention are within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A high-precision AC voltage DC component detection circuit, characterized in that: The invention comprises a capacitor-resistor voltage divider circuit which is arranged in sequence, comprising a first resistor (R1), a second resistor (R2) and a first capacitor (C1). By adjusting the capacitance of the first capacitor (C1) and the resistance of the first resistor (R1) and the second resistor (R2), the voltage division ratio of the AC voltage can be adjusted, and the DC voltage will not be attenuated, thereby achieving the effect of reducing the AC voltage amplitude but not changing the DC voltage amplitude; A differential amplifier circuit comprises a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a sixth resistor (R6), a second capacitor (C2), a third capacitor (C3), a first operational amplifier (U1), a first diode (D1), and a second diode (D2); the circuit amplification factor is set according to a DC voltage sampling range, and the voltage after the capacitor-resistor voltage divider circuit is scaled proportionally; meanwhile, the first diode (D1) and the second diode (D2) play a role in clamping the amplitude of the common-mode voltage input of the operational amplifier; A second-order RC filter circuit, comprising an eighth resistor (R8), a ninth resistor (R9), a fourth capacitor (C4) and a fifth capacitor (C5), for filtering out the AC component in the voltage after differential amplification and retaining only the DC voltage; The voltage following and raising circuit includes a tenth resistor (R10), a second operational amplifier (U2), an eleventh resistor (R11), and a twelfth resistor (R12). The DC voltage after being filtered by the second-order RC filter circuit in the previous stage is raised after passing through the follower, and the voltage is raised to an effective detection voltage range of 0-3V; The AD voltage clamping circuit includes a thirteenth resistor (R13), a sixth capacitor (C6), and a third diode (D3), which is used to filter out high-frequency interference signals and clamp the input CPU voltage to prevent abnormal voltage amplitude from damaging the CPU device.

2. The high-precision AC voltage DC component detection circuit according to claim 1, characterized in that: The input source of the circuit adopts an AC output voltage, and the output end of the circuit is connected to the CPU.

3. The high-precision AC voltage DC component detection circuit according to claim 1, characterized in that: In the capacitor-resistor voltage divider circuit, the capacitor's characteristic of passing AC and blocking DC is used to generate different equivalent impedances Rac and Rdc for AC voltage and DC voltage, Rac = 1 / (2πfc), Rdc = ∞.

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