Two-stage isolated high-voltage sampling circuit

Abstract

The utility model discloses a two-stage isolated high-voltage sampling circuit, which comprises a high-voltage side resistance voltage division circuit, a first-stage optical coupler isolation circuit, an operational amplifier processing circuit, a voltage following circuit, a second-stage optical coupler isolation circuit and a low-voltage output circuit. The first-stage optical coupler isolation circuit comprises an optical coupler I, the operational amplifier processing circuit comprises a virtual short and virtual off analysis operational amplifier, and the second-stage optical coupler isolation circuit comprises an optical coupler II; the first optocoupler and the second optocoupler adopt optocouplers of the same model, and output resistance of emitting electrodes of the optocouplers is consistent. The output end of the low-voltage side output circuit is connected with the single-chip microcomputer. A low-voltage system of the control circuit part and a high-voltage system of the power circuit part can be isolated from each other through two-stage optical coupler isolation, and through two-stage optical coupler isolation, the isolation effect is more stable, and the anti-interference capability is stronger; meanwhile, the utility model has the advantages of few electronic devices, simple circuit, low cost and the like.

Description

Technical Field

[0001] This utility model relates to a high-voltage sampling circuit, and more particularly to a two-stage isolated high-voltage sampling circuit. Background Technology

[0002] Currently, high-voltage isolation voltage sampling plays a crucial role in power systems, industrial control, and new energy fields. Its development has gone through several stages with continuous technological advancements. Early high-voltage isolation voltage sampling primarily employed electromagnetic transformers, such as electromagnetic voltage transformers. These transformers operate based on the principle of electromagnetic induction, offering high accuracy and stability, but their large size, heavy weight, and magnetic saturation issues limit their application in some high-frequency and high-current scenarios. With the development of semiconductor technology, sampling methods based on the principle of resistive voltage division emerged. This method has a relatively simple structure, but suffers from significant power losses in the voltage dividing resistors and severe temperature drift.

[0003] Related key technologies;

[0004] In recent years, optical isolation technology has been increasingly widely used in high-voltage isolation voltage sampling. For example, optocouplers based on the photoelectric effect can meet the requirements of high-voltage isolation voltage sampling accuracy, reliability, and safety, while also achieving good electrical isolation. They have advantages such as wide bandwidth, fast response speed, and good insulation performance. At the same time, the development of digital signal processing technology has made the processing and transmission of sampled signals more accurate and efficient.

[0005] Existing technology 1:

[0006] Controlled by the principle of series resistor voltage divider sampling, this circuit uses series resistors to reduce voltage, achieving precise voltage sampling control. Series resistor voltage divider sampling offers high precision and is simple to implement, making it suitable for most sampling circuits. In high-voltage power supplies, sampling the output voltage and transmitting it to the low-voltage control terminal is crucial. To avoid mutual interference between high and low voltage signals, electrical isolation is required between the high and low voltage sides of the sampled voltage. Currently, commonly used isolation methods include transformer isolation, capacitor isolation, and optocoupler isolation. Linear optocoupler isolation can achieve analog signal isolation, and with a carefully designed isolation circuit, high-precision signal isolation can be achieved.

[0007] Disadvantages of existing technology 1:

[0008] In the application of series resistor voltage divider sampling technology, the additional power consumption is relatively high, which reduces the overall power operation and affects the sampling results. Although transformer isolation has a high voltage level, it is bulky and has limited bandwidth; capacitor isolation has high efficiency, but requires the signal frequency to be significantly higher than the noise frequency.

[0009] In view of the above, this utility model is hereby proposed. Utility Model Content

[0010] The purpose of this invention is to provide a two-stage isolated high-voltage sampling circuit to solve the aforementioned technical problems in the prior art.

[0011] The objective of this utility model is achieved through the following technical solution:

[0012] The two-stage isolated high-voltage sampling circuit of this utility model includes a high-voltage side resistor divider circuit, a first-stage optocoupler isolation circuit, an operational amplifier processing circuit, a voltage follower circuit, a second-stage optocoupler isolation circuit, and a low-voltage output circuit.

[0013] Compared with the prior art, the two-stage isolation high-voltage sampling circuit provided by this utility model fully isolates high and low voltages, reduces noise interference, prevents voltage spikes, and has fewer components and a simpler circuit. While ensuring high voltage sampling accuracy, it can improve the safety and reliability of the system. Attached Figure Description

[0014] Figure 1 A schematic diagram of a two-stage isolated high-voltage sampling circuit provided in an embodiment of this utility model.

[0015] Figure 2 This is a schematic diagram of the high-voltage isolation sampling circuit according to an embodiment of the present invention.

[0016] Figure 3 This is a block diagram of the high-voltage isolation sampling circuit according to an embodiment of the present invention.

[0017] Figure 4 This is a simulation diagram of the high-voltage isolation sampling circuit according to an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments, which do not constitute a limitation on the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0019] First, the following explanations are provided for the terms that may be used in this article:

[0020] The term "and / or" means that either or both can be achieved simultaneously. For example, X and / or Y means that it includes both "X" or "Y" as well as the three cases of "X and Y".

[0021] The terms “including,” “comprising,” “containing,” “having,” or other similar semantic descriptions should be interpreted as non-exclusive inclusion. For example, “including a technical feature element (such as raw material, component, ingredient, carrier, dosage form, material, size, part, component, mechanism, device, step, process, method, reaction conditions, processing conditions, parameter, algorithm, signal, data, product or article of manufacture, etc.)” should be interpreted as including not only the expressly listed technical feature element, but also other technical feature elements that are not expressly listed and are well-known in the art.

[0022] The term "composed of" excludes any technical features not expressly listed. When used in a claim, it closes the claim to exclude all technical features other than those expressly listed, except for associated conventional impurities. If the term appears only in a clause of a claim, it limits the claim to the elements expressly listed in that clause; elements recited in other clauses are not excluded from the overall claim.

[0023] The contents not described in detail in the embodiments of this utility model are existing technologies known to those skilled in the art. Where specific conditions are not specified in the embodiments of this utility model, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this utility model whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0024] The two-stage isolated high-voltage sampling circuit of this utility model includes a high-voltage side resistor divider circuit, a first-stage optocoupler isolation circuit, an operational amplifier processing circuit, a voltage follower circuit, a second-stage optocoupler isolation circuit, and a low-voltage output circuit.

[0025] The first-stage optocoupler isolation circuit includes optocoupler one U1, the operational amplifier processing circuit includes "virtual short and virtual open" analysis operational amplifier U3A, and the second-stage optocoupler isolation circuit includes optocoupler two U2;

[0026] The optocoupler U1 and optocoupler U2 use the same type of optocoupler, and their emitter output resistance is the same.

[0027] The output terminal of the low-voltage side output circuit is connected to the microcontroller (MCU).

[0028] In summary, the two-stage isolation high-voltage sampling circuit of this utility model uses linear optocouplers to achieve high- and low-voltage isolation transmission of the sampling voltage. While ensuring accurate sampling of the DC bus voltage output from the power circuit of the switching power supply, the two-stage optocoupler isolation effectively isolates the low-voltage system of the control circuit from the high-voltage system of the power circuit. Furthermore, the two-stage optocoupler isolation provides more stable isolation and stronger anti-interference capabilities. Additionally, the high-voltage isolation sampling circuit of this utility model has advantages such as fewer electronic components, simpler circuitry, and lower cost.

[0029] To more clearly demonstrate the technical solution and effects provided by this utility model, the following detailed description of the embodiments of this utility model is provided with reference to specific examples.

[0030] Example 1

[0031] like Figure 1 As shown:

[0032] A high-voltage isolation sampling circuit for a switching power supply includes a high-voltage side resistor divider circuit, a first-stage optocoupler isolation circuit, an operational amplifier processing circuit, a voltage follower circuit, a second-stage optocoupler isolation circuit, and a low-voltage output circuit.

[0033] like Figure 2 The diagram shown is a schematic of the high-voltage isolation sampling circuit of this utility model.

[0034] like Figure 3 The diagram shown is a block diagram of the high-voltage isolation sampling circuit of this utility model.

[0035] In this embodiment of the invention, the emitter output resistor values ​​of optocouplers U1 and U2 are identical. Applying the "virtual short, virtual open" principle to analyze operational amplifier U3A, the "virtual open" condition indicates that the current at both the positive and negative inputs of U3A is zero, while the "virtual short" condition indicates that the voltages at the positive and negative inputs of U3A are equal. Therefore, the emitter voltages of the internal transistors in optocouplers U1 and U2 are equal. With identical external output resistors, the emitter voltage currents of the internal transistors in U1 and U2 are also equal. A key technical parameter of optocouplers is the current transfer ratio (CTR), which is the ratio of the current flowing through the internal LED to the current flowing through the internal transistor. Since U1 and U2 use the same type of optocoupler, their CTRs are equal. This leads to the conclusion that the current flowing through the internal LEDs of optocouplers U1 and U2 is equal, meaning the currents through the high-voltage side voltage divider resistor and the low-voltage side output resistor are equal. The high-voltage input side voltage is the sum of the total voltage across the voltage divider resistors and the diode voltage drop, while the low-voltage output side voltage is the voltage across the low-voltage output resistor. Since the currents are equal, it can be deduced that the high-voltage and low-voltage sides have a linear relationship. The voltage output from the low-voltage side to the microcontroller unit (MCU) has a definite linear function relationship with the high-voltage side voltage, thus completing the accurate acquisition of the high-voltage voltage on the low-voltage side.

[0036] like Figure 4 The figure shown is a simulation diagram of the high-voltage isolation sampling circuit of this utility model. The simulation data is recorded in Table 1:

[0037] Table 1: Simulated High and Low Voltage Side Voltage Data Records

[0038] High voltage input side Low voltage output side Current transfer ratio 500V 1V 500％ 600V 1.2V 500％ 700V 1.4V 500％ 800V 1.6V 500％ 900V 1.8V 500％ 1000V 2V 500％

[0039] The beneficial effects of this utility model's technical solution are:

[0040] The high-voltage isolation sampling circuit proposed in this invention mainly isolates high and low voltage through a two-stage optocoupler isolation circuit. Isolation in electronic circuits, especially in high-voltage sampling circuits, is crucial for protecting low-voltage side components. An optocoupler, also known as an opto-isolator, has an LED at the input that emits light when current flows through it; at the output, it has a photosensitive element that detects the light emitted by the LED and responds accordingly. It combines two basic functions: signal transmission and electrical isolation. The main characteristic of an optocoupler is that there is no direct electrical connection between the input and output. The only connection is the light emitted by the LED, which allows signals to be transmitted between different parts of the isolated circuit without electrical conduction, allowing signals to be transmitted from one side to the other without direct electrical contact. This function is crucial for protecting sensitive low-voltage control circuits from high voltage, noise, or potential damage, avoiding the risk of high-voltage damage or noise interference to the low-voltage side of the sampling circuit. Isolation in high-voltage sampling circuits also plays a more important role: firstly, preventing voltage spikes, as direct electrical connections in switching power supply applications can damage low-voltage control circuits. Optocouplers provide isolation, ensuring that voltage spikes do not cross into the sensitive areas of the switching power supply sampling circuit system. Secondly, they reduce noise. Sampling circuits require high accuracy and are therefore sensitive to noise interference. Noise on the high-voltage side can interfere with the signal and affect the performance of sensitive components, leading to inaccurate sampling. Optocouplers cut off the electrical path, preventing noise transmission and better guaranteeing voltage sampling accuracy. Optocoupler isolation also prevents ground loops. In high-voltage sampling systems, the high-voltage power circuit and the low-voltage control circuit have different ground potentials. Direct connection between these parts can create ground loops, causing interference or even damage. Optocouplers ensure isolation between the high- and low-voltage circuits while still allowing data or control signal transmission.

[0041] As the requirements for accuracy, reliability, and safety in high-voltage isolation voltage sampling continue to increase, new materials and technologies are being explored and applied. For example, advanced packaging technologies are being used to improve isolation performance and stability. In the future, high-voltage isolation voltage sampling technology will continue to develop towards higher precision, smaller size, lower power consumption, wider bandwidth, and greater intelligence to meet increasingly complex and diverse application needs.

[0042] Key technical features of this utility model:

[0043] A high-voltage isolation sampling circuit was designed to fully isolate high and low voltages, minimize noise interference, prevent voltage spikes, and has few components and a simple circuit design. While ensuring high voltage sampling accuracy, it can improve the safety and reliability of the system.

[0044] The above description is merely a preferred embodiment of this utility model, but the scope of protection of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this utility model should be included within the scope of protection of this utility model. Therefore, the scope of protection of this utility model should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of this utility model and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A two-stage isolated high-voltage sampling circuit, characterized in that, The circuit comprises a high-voltage side resistance voltage dividing circuit, a first-stage optocoupler isolation circuit, an operational amplifier processing circuit, a voltage follower circuit, a second-stage optocoupler isolation circuit and a low-voltage side output circuit. The first-stage optocoupler isolation circuit comprises an optocoupler one (U1), the operational amplifier processing circuit comprises a "virtual short virtual open" analysis operational amplifier (U3A), and the second-stage optocoupler isolation circuit comprises an optocoupler two (U2). The optocoupler one (U1) and the optocoupler two (U2) apply the same model optocoupler, and the emitter output resistances are consistent.

2. The two-stage isolated high-voltage sampling circuit of claim 1, wherein, The output end of the low-voltage side output circuit is connected with a single-chip microcomputer.

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