Isolated voltage detection circuit

Abstract

An isolated voltage detection circuit comprises a sampling end and an input circuit which is connected with the sampling end and converts the sampling end into an output voltage V +; the reference circuit adopts a triangular wave generator and is used for generating a reference voltage V-; the comparison circuit comprises a comparator U4A, and the two input ends of the comparator U4A are connected with the output end of the input circuit and the output end of the reference circuit respectively; the control end of the switching circuit is connected with the output end of the comparator U4A, and the on and off of the switching circuit are controlled by the output level of the comparator U4A; and the isolation circuit comprises an optocoupler U3 and is used for strong and weak current isolation, a light emitting end of the isolation circuit is connected with the switching circuit, one pin of a receiving end of the isolation circuit is used as a detection end, and different duty ratios of waveforms output by the detection end can be converted into corresponding voltage values by the MCU. Isolation of strong current and weak current is achieved through the isolation circuit, and the voltage detection circuit has the advantages of being high in response speed, high in precision and high in anti-interference performance and is suitable for various voltage detection scenes needing strong current and weak current isolation.

Description

Technical Field

[0001] The utility model specifically relates to an isolated voltage detection circuit. Background Art

[0002] The voltage detection circuit is an important component circuit for product protection. For some high-voltage fields, the voltage detection circuit cannot directly detect high voltage. Generally, a transformer is used to step down the relatively high AC voltage signal and convert the relatively high AC voltage signal into a DC signal that can be recognized by a microcontroller, and then corresponding detection is carried out. However, in the above detection scheme, the stepped-down AC voltage signal is prone to a lot of interference, such as spikes, oscillations, etc., which affects the detection result. If the AC voltage signal is rectified, regulated, and filtered, since the equipment and components required in the corresponding process are relatively complex, the detection cost of detecting the relatively high AC voltage signal in the prior art is relatively high. At the same time, since the detection process involves too many equipment and components, the probability of failure in the detection process is increased, thereby increasing the implementation cost and implementation difficulty of the scheme and reducing the detection efficiency and detection reliability of the scheme. Summary of the Utility Model

[0003] Aiming at the deficiencies existing in the prior art, the purpose of the utility model is to provide an isolated voltage detection circuit.

[0004] To achieve the above purpose, the utility model provides the following technical solutions:

[0005] An isolated voltage detection circuit, which includes:

[0006] A sampling terminal

[0007] An input circuit, connected to the sampling terminal and converting it into an output voltage V+;

[0008] A reference circuit, which uses a triangular wave generator to generate a reference voltage V-;

[0009] A comparison circuit, which includes a comparator U4A, and its two input terminals are respectively connected to the output terminal of the input circuit and the output terminal of the reference circuit;

[0010] A switch circuit, whose control terminal is connected to the output terminal of the comparator U4A, and is controlled to conduct and cut off by the output level of the comparator U4A;

[0011] An isolation circuit, which includes an optocoupler U3 for isolating strong and weak electricity, and its light-emitting end is connected to the switch circuit, and one pin of its receiving end is used as a detection end, and different duty cycles of the waveform output by the detection end can be converted into corresponding voltage values by the MCU.

[0012] A first filter circuit is provided between the sampling end and the input circuit.

[0013] The input circuit is a voltage follower.

[0014] A second filter circuit is provided between the output end of the input circuit and comparator U4A.

[0015] The triangular wave generator includes an integrator connected to comparator U4A, comparators U4B and U4C for adjusting the waveform rise and fall of the integrator, and their peripheral circuits.

[0016] The integrator includes operational amplifier U2C. The output end of operational amplifier U2C is connected to the input end of comparator U4A. A capacitor C6 is connected in parallel between the negative input end and the output end of operational amplifier U2C. The negative input end of operational amplifier U2C is also connected to the connection node of resistor R13 and resistor R18. Resistor R13 is connected to power supply VM. Resistor R18 is connected to the output end of comparator U4C. The positive input end of operational amplifier U2C is connected to the positive input end of comparator U4C. The positive input end of operational amplifier U2C is also connected to power supply VM through resistor R15 and grounded through resistor R17 respectively. The output end of operational amplifier U2C is also connected to the negative input end of comparator U4B.

[0017] A voltage dividing circuit for providing a comparison reference is provided between the negative input end of comparator U4C and the positive input end of comparator U4B.

[0018] A third filter circuit is provided between the reference circuit and comparator U4A.

[0019] The switch circuit includes triode Q1. The base of triode Q1 is connected to the output end of comparator U4A. The collector of triode Q1 is grounded. The emitter of triode Q1 is connected to power supply VM. The collector and emitter of triode Q1 are respectively connected to the two pins of the light emitting end of optocoupler U3. The collector of triode Q1 is connected to power supply VM through pull-up resistor R3.

[0020] A hysteresis resistor R5 is connected in parallel between the positive input end and the output end of comparator U4A.

[0021] The beneficial effects of the present utility model: The isolation between strong and weak electricity is realized through the isolation circuit. At the same time, the level of the comparison output of the input circuit and the reference circuit is used by the comparison circuit to control the isolation circuit, so that the isolation circuit outputs waveforms with different duty cycles. The MCU processes the duty cycle of the waveform to obtain the corresponding voltage. It has the characteristics of high response speed, high precision and strong anti-interference ability, and is suitable for various scenarios of voltage detection that require isolation between strong and weak electricity. Description of the Drawings

[0022] Figure 1 This is the circuit schematic diagram of the present utility model.

[0023] Figure 2 This is the logic block diagram of Embodiment 1 of the present utility model.

[0024] Figure 3 This is the logic block diagram of Embodiment 2 of the present utility model. Detailed implementation manners

[0025] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without making creative efforts shall fall within the protection scope of the present utility model.

[0026] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present utility model are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0027] As Figure 1 shown, the present utility model discloses an isolated voltage detection circuit, which includes:

[0028] Sampling terminal 1, which is used to connect to the point to be sampled, can collect voltage signals and can also be used to collect analog signals;

[0029] Input circuit 2, connected to the sampling terminal 1 and converting it into an output voltage V+;

[0030] Reference circuit 7, which uses a triangular wave generator to generate a reference voltage V-;

[0031] Comparison circuit 3, which includes a comparator U4A, and its two input terminals are respectively connected to the output terminal of the input circuit 2 and the output terminal of the reference circuit 7;

[0032] Switching circuit 4, whose control terminal is connected to the output terminal of the comparator U4A and is controlled to conduct and cut off by the output level of the comparator U4A;

[0033] Isolation circuit 5, which includes an optocoupler U3 for isolating strong and weak electricity, and its light emitting end is connected to the switching circuit 4, and one pin of its receiving end is used as the detection terminal 6. Different duty cycles of the waveform output by the detection terminal can be converted into corresponding voltage values by the MCU.

[0034] Since the PWM signal has a fixed frequency and the duty cycle changes with the measured voltage, the MCU can accurately calculate the corresponding voltage value by measuring the change in the duty cycle. This characteristic of the PWM signal makes the process of processing and reading the signal simple and efficient, while also reducing the errors that may occur during data transmission.

[0035] At the same time, the PWM signal can be effectively isolated through an optocoupler component with low cost and high reliability, thus ensuring that the signal is not affected by interference and noise during transmission to the main control MCU.

[0036] After the sampling voltage VI is filtered and followed, the comparison reference V+ is obtained; the operational amplifier U2C and C6 form an integrator, and together with the comparator U4B, U4C and the surrounding RC components, a triangular wave generator is constituted. After filtering, the comparison reference V- is obtained; as Figure 1 shown, when V+ is higher than V-, the comparator U4A outputs a low level, the triode Q1 is turned off, the optocoupler U3 is turned on, and VO outputs low; conversely, when V+ is lower than V-, VO outputs high; when VI changes, VO obtains a rectangular wave with different duty cycles. The MCU processes different duty cycles to obtain the corresponding detected voltage value, achieving the purpose of voltage detection.

[0037] A first filtering circuit 8 is provided between the sampling terminal 1 and the input circuit 2. The first filtering circuit 8 is an RC filtering circuit composed of a resistor R7 and a capacitor C2, which directly filters the sampling voltage VI.

[0038] The input circuit 2 is a voltage follower, which includes an operational amplifier U2B. The positive input terminal of the operational amplifier U2B is connected to the RC filtering circuit. A resistor R11 and a capacitor C5 are connected in parallel between the negative input terminal and the output terminal of the operational amplifier U2B, and the three together constitute a voltage follower.

[0039] A second filtering circuit 9 is provided between the output terminal of the input circuit 2 and the comparator U4A. The second filtering circuit 9 is an RC filtering circuit composed of a resistor R8 and a capacitor C3, which filters the voltage output by the voltage follower.

[0040] The triangular wave generator includes an integrator 71 connected to the comparator U4A, comparators U4B and U4C for adjusting the waveform rise and fall of the integrator 71 and their peripheral circuits.

[0041] The integrator 71 includes an operational amplifier U2C. The output terminal of the operational amplifier U2C is connected to the input terminal of a comparator U4A. A capacitor C6 is connected in parallel between the negative input terminal and the output terminal of the operational amplifier U2C. The capacitor C6 is an integrating capacitor and forms an integrator with the operational amplifier U2C. The negative input terminal of the operational amplifier U2C is also connected to the connection node of a resistor R13 and a resistor R18. The resistor R13 is connected to a power supply VM, and the resistor R18 is connected to the output terminal of a comparator U4C. The positive input terminal of the operational amplifier U2C is connected to the positive input terminal of the comparator U4C. The positive input terminal of the operational amplifier U2C is also connected to the power supply VM through a resistor R15 and grounded through a resistor R17 respectively. The output terminal of the operational amplifier U2C is also connected to the negative input terminal of a comparator U4B.

[0042] The comparator U4B and the comparator U4C are used to adjust the rise and fall of the integral waveform and determine the upper and lower vertices of the triangular wave.

[0043] Among them, the resistors R15 and R17 are voltage-dividing resistors, which provide a comparison reference for the comparator U4C.

[0044] A voltage-dividing circuit for providing a comparison reference is provided between the negative input terminal of the comparator U4C and the positive input terminal of the comparator U4B. This voltage-dividing circuit is composed of a voltage-dividing resistor R14 and a resistor R20, and is used to provide a comparison reference for the two comparators.

[0045] A filter capacitor C7 is connected in parallel between the positive input terminal of the operational amplifier U2C and the positive input terminal of the comparator U4C. At the same time, a current-limiting resistor R16 is connected in series between the output terminal of the operational amplifier U2C and the negative input terminal of the comparator U4B, and a current-limiting resistor R19 is connected in series between the output terminal of the comparator U4B and the negative input terminal of the comparator U4C.

[0046] A third filter circuit 10 is provided between the reference circuit 7 and the comparator U4A. The third filter circuit 10 is an RC filter circuit composed of a resistor R12 and a capacitor C4, which filters the reference triangular wave.

[0047] The switch circuit 4 includes a triode Q1. The base of the triode Q1 is connected to the output terminal of the comparator U4A. The collector of the triode Q1 is grounded. The emitter of the triode Q1 is connected to the power supply VM. The collector and emitter of the triode Q1 are respectively connected to the two pins of the light-emitting end of an optocoupler U3. The collector of the triode Q1 is connected to the power supply VM through a pull-up resistor R3.

[0048] The switch circuit 4 can also adopt a thyristor control circuit or a field-effect transistor switch circuit.

[0049] Among them, a current-limiting resistor R4 and a resistor R9 are respectively connected in series to the emitter and base of the triode Q1, which play a role in protecting the triode Q1 and the optocoupler.

[0050] Meanwhile, the existence of resistor R3 can ensure that when the output of comparator U4A is not at a low level, transistor Q1 is in a conducting state.

[0051] A hysteresis resistor R5 is connected in parallel between the positive input terminal and the output terminal of the comparator U4A. The existence of the hysteresis resistor R5 can prevent the output of the comparator U4A from jittering at the comparison critical point.

[0052] Embodiment 1

[0053] As Figure 2 shown, this application is used for bus voltage detection. After converting three-phase electricity into direct current, the converted voltage is sampled through the voltage detection circuit proposed by the present utility model, and the output VO is processed by the MCU.

[0054] Embodiment 2

[0055] As Figure 3 shown, this application is used for external analog quantity acquisition. It can be directly connected to the output terminal of the external analog quantity acquisition circuit, and the MCU processes the output waveform to obtain the corresponding analog quantity.

[0056] The embodiments should not be regarded as a limitation to the present utility model, but any improvement based on the spirit of the present utility model should be within the protection scope of the present utility model.

Claims

1. An isolated voltage detection circuit, characterized in that: It includes: Sampling terminal (1), Input circuit (2), connected to the sampling terminal (1) and converting it into an output voltage V+; Reference circuit (7), which uses a triangular wave generator to generate a reference voltage V-; Comparator circuit (3), which includes a comparator U4A, and its two input terminals are respectively connected to the output terminal of the input circuit (2) and the output terminal of the reference circuit (7); Switching circuit (4), whose control terminal is connected to the output terminal of the comparator U4A and is controlled to conduct and cut off by the output level of the comparator U4A; Isolation circuit (5), which includes an optocoupler U3 for strong and weak electrical isolation, and its light emitting end is connected to the switching circuit (4), and one pin of its receiving end is used as a detection terminal, and different duty cycles of the waveform output by the detection terminal can be converted into corresponding voltage values by the MCU.

2. An isolated voltage detection circuit according to claim 1, characterized in that: A first filter circuit (8) is provided between the sampling terminal (1) and the input circuit (2).

3. An isolated voltage detection circuit according to claim 1 or 2, characterized in that: The input circuit (2) is a voltage follower.

4. An isolated voltage detection circuit according to claim 3, wherein: A second filter circuit (9) is provided between the output terminal of the input circuit (2) and the comparator U4A.

5. An isolated voltage detection circuit according to claim 1, wherein: The triangular wave generator includes an integrator (71) connected to the comparator U4A, comparators U4B and U4C for adjusting the waveform rise and fall of the integrator (71) and their peripheral circuits.

6. An isolated voltage detection circuit according to claim 5, characterized in that: The integrator (71) includes an operational amplifier U2C. The output terminal of the operational amplifier U2C is connected to the input terminal of the comparator U4A. A capacitor C6 is connected in parallel between the negative input terminal and the output terminal of the operational amplifier U2C. The negative input terminal of the operational amplifier U2C is also connected to the connection node of a resistor R13 and a resistor R18, and the resistor R13 is connected to the power supply VM. The resistor R18 is connected to the output terminal of the comparator U4C. The positive input terminal of the operational amplifier U2C is connected to the positive input terminal of the comparator U4C, and the positive input terminal of the operational amplifier U2C is also connected to the power supply VM through a resistor R15 and grounded through a resistor R17 respectively. The output terminal of the operational amplifier U2C is also connected to the negative input terminal of the comparator U4B.

7. An isolated voltage detection circuit according to claim 6, characterized in that: A voltage dividing circuit for providing a comparison reference is provided between the negative input terminal of the comparator U4C and the positive input terminal of the comparator U4B.

8. An isolated voltage detection circuit according to claim 1, 5, 6 or 7, characterized in that: A third filter circuit (10) is provided between the reference circuit (7) and the comparator U4A.

9. An isolated voltage detection circuit according to claim 1, 5, 6 or 7, characterized in that: The switching circuit (4) includes a triode Q1. The base of the triode Q1 is connected to the output terminal of the comparator U4A. The collector of the triode Q1 is grounded. The emitter of the triode Q1 is connected to the power supply VM. The collector and emitter of the triode Q1 are respectively connected to the two pins of the light emitting end of the optocoupler U3, and the collector of the triode Q1 is connected to the power supply VM through a pull-up resistor R3.

10. An isolated voltage detection circuit according to claim 1, characterized in that: A hysteresis resistor R5 is connected in parallel between the positive input terminal and the output terminal of the comparator U4A.

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