A wide-range AC voltage frequency detection circuit

Abstract

This invention discloses a wide-range AC voltage frequency detection circuit, comprising: a positive half-wave rectifier-divider circuit for half-wave rectification and voltage division of the positive half-cycle of the AC input voltage to convert it into a low-voltage pulsating signal of the same frequency; an effective voltage detection circuit, including a comparator for comparing the input low-voltage pulsating signal with a preset threshold voltage to generate a square wave signal consistent with the input frequency; and an optocoupler isolation circuit for electrically isolating the generated square wave signal for safe transmission to a processor. This invention enables wide-range AC voltage frequency detection, freeing electrical equipment or systems from dependence on a fixed, ideal power grid environment. It can be applied to industrial environments with large voltage fluctuations, providing reliable support and basis for the safe and stable operation of industrial loads. Furthermore, the circuit described in this invention has advantages such as simple structure, ease of implementation, flexibility, and versatility.

Description

Technical Field

[0001] This utility model relates to a circuit for detecting AC voltage frequency, specifically, to a wide-range AC voltage frequency detection circuit that can adapt to a wide range of input voltage variations, belonging to the field of power electronics and signal processing technology. Background Technology

[0002] In power electronic equipment systems, such as charging piles, inverters, uninterruptible power supplies (UPS), and power lifting equipment, real-time and accurate detection of the input AC voltage frequency is a fundamental and crucial function. The frequency signal is not only an important basis for system synchronization and phase-locking, but also fundamental for assessing power grid quality, implementing voltage protection, and precisely controlling load equipment.

[0003] Furthermore, in critical scenarios such as industrial automation, the voltage amplitude of AC power supplies may fluctuate drastically due to the start-up of large loads (such as a 30% voltage drop when a motor starts) or grid faults. In addition, with the large-scale integration of distributed energy sources such as wind and solar power, the voltage and frequency characteristics of the power grid have become dynamic and complex. Existing research shows that during high-voltage transmission, new energy grid connection, or grid faults, the AC voltage amplitude at monitoring points can vary drastically between 20% and 150% of the rated value. However, existing frequency detection methods (such as zero-crossing detection) typically treat "voltage amplitude" as a relatively stable quantity in their standard design, with a limited dynamic range. Once the input voltage fluctuates widely between tens and hundreds of volts, it will fail due to threshold drift, saturation, loss of lockout, or quantization noise, leading to a significant increase in frequency detection error or even complete loss of lockout, thus posing a safety risk. To solve the technical challenge of reliably and accurately monitoring AC signal frequencies in modern power systems and electronic equipment under wide voltage fluctuation scenarios, it is necessary to develop technologies that can achieve wide-range AC voltage frequency detection. This will be of great significance and value in ensuring the safe and stable operation of industrial loads. Utility Model Content

[0004] In view of the above-mentioned problems and needs of the existing technology, the purpose of this utility model is to provide a wide-range AC voltage frequency detection circuit that can adapt to a wide range of input voltage changes, so as to provide reliable support and basis for ensuring the safe and stable operation of industrial loads.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A wide-range AC voltage frequency detection circuit includes:

[0007] A positive half-wave rectifier and voltage divider circuit is used to perform half-wave rectification and voltage division on the positive half-cycle of the AC input voltage to convert it into a low-voltage pulsating signal of the same frequency.

[0008] An effective voltage detection circuit includes a comparator for comparing an input low-voltage pulsating signal with a preset threshold voltage to generate a square wave signal with the same frequency as the input; and

[0009] Optocoupler isolation circuits are used to electrically isolate the generated square wave signal for safe transmission to the processor.

[0010] One embodiment of the positive half-wave rectifier voltage divider circuit includes a resistor voltage divider circuit and a positive half-wave rectifier circuit.

[0011] In a further embodiment, the resistor divider circuit includes an upper arm resistor and a lower arm resistor, and the upper arm resistor is composed of multiple resistors connected in series.

[0012] In a preferred embodiment, the resistor voltage divider circuit further includes a Zener diode, which is connected in parallel with the lower arm resistor.

[0013] In a further embodiment, the positive half-wave rectifier circuit is composed of a rectifier diode D1 and a return diode D2. The rectifier diode D1 is connected in series between the upper arm resistor and the lower arm resistor. The cathode of the return diode D2 is connected to the node between the upper arm resistor and the anode of the rectifier diode D1. The anode of the return diode D2 is grounded.

[0014] In one embodiment, the effective voltage detection circuit further includes a comparator power supply that independently powers the comparator.

[0015] In one embodiment, the effective voltage detection circuit further includes two threshold voltage divider resistors connected in series with the comparator power supply, and the inverting input terminal of the comparator is connected to the node between the two threshold voltage divider resistors.

[0016] In one embodiment, the effective voltage detection circuit further includes a positive feedback resistor, one end of which is connected to the non-inverting input of the comparator, and the other end of which is connected to the output of the comparator.

[0017] In one embodiment, the effective voltage detection circuit further includes a current-limiting resistor and a clamping diode connected in reverse parallel across the current-limiting resistor, wherein the current-limiting resistor is connected in series between the cathode of the rectifier diode and the non-inverting input of the comparator.

[0018] In one embodiment, the optocoupler isolation circuit is composed of an optocoupler isolation chip and its peripheral resistor.

[0019] In one embodiment, the optocoupler isolation chip is a 6-pin optocoupler isolation gate driver chip.

[0020] In one embodiment, the peripheral resistor includes an input current-limiting resistor and an output voltage-dividing resistor.

[0021] Compared with the prior art, the beneficial technical effects of this utility model are as follows:

[0022] The circuit described in this invention enables the detection of a wide range of AC voltage frequencies, freeing electrical equipment or systems from dependence on a fixed, ideal power grid environment. It can be applied to industrial environments with significant voltage fluctuations, providing reliable support and a basis for the safe and stable operation of industrial loads. Furthermore, by adjusting the resistance value of the threshold voltage divider resistor, the lower limit of the effective signal detection threshold can be easily set to adapt to the signal validity determination requirements of different applications. This gives the circuit strong design flexibility, practicality, and versatility. In addition, the circuit described in this invention also has advantages such as simple structure and ease of implementation, possessing strong industrial practical value. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a wide-range AC voltage frequency detection circuit provided by this utility model;

[0024] Figure 2 This is a schematic diagram of the circuit structure for wide-range AC voltage frequency detection according to an embodiment of this utility model. Detailed Implementation

[0025] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0026] Example

[0027] Depend on Figure 1 As shown, this embodiment provides a wide-range AC voltage frequency detection circuit, including: a positive half-wave rectifier voltage divider circuit 01, an effective voltage detection circuit 02, and an optocoupler isolation circuit 03.

[0028] In this embodiment, the effective voltage detection circuit 02 includes a comparator, and the positive half-wave rectifier voltage divider circuit 01 includes a resistor voltage divider circuit and a positive half-wave rectifier circuit.

[0029] The working principle of the wide-range AC voltage frequency detection circuit described in this embodiment is as follows:

[0030] The high-voltage AC input signal first passes through a positive half-wave rectifier and voltage divider circuit 01 to acquire and divide the positive half-cycle of the AC input voltage, converting it into a low-voltage pulsating signal of the same frequency. Subsequently, the low-voltage pulsating signal is sent to an effective voltage detection circuit 02, where a comparator compares the input low-voltage pulsating signal with a preset threshold voltage, and generates a square wave signal with the same input frequency based on the comparison result. Then, the square wave signal is electrically isolated by an optocoupler isolation circuit 03 to be safely output to the back-end processor 04. Finally, the processor 04 performs frequency calculations and other processing on the acquired square wave signal.

[0031] The specific circuit structure for implementing the wide-range AC voltage frequency detection in this embodiment is as follows: Figure 2 As shown in the figure, L and N are the input terminals of the high-voltage AC signal VIN. Usually, L represents the live wire and N represents the neutral wire.

[0032] Depend on Figure 2 As shown in the figure, in this embodiment, the resistor voltage divider circuit includes an upper arm resistor and a lower arm resistor. The upper arm resistor is composed of R1, R2, R3, R4 and R5 connected in series (but it should be noted that the number of resistors constituting the upper arm resistor is not limited to the 5 shown in the figure, and can be more than 5 or less than 5, depending on the size of the selected resistor and the voltage divider processing requirements. This part is common design knowledge in the field and will not be elaborated here). The lower arm resistor is R6 in the figure.

[0033] In a preferred embodiment, the resistor voltage divider circuit further includes a Zener diode D3 connected in parallel with the lower arm resistor R6. The Zener diode D3 can act as an overvoltage protection clamp to prevent the subsequent circuit from being broken down and burned.

[0034] Then by Figure 2 As shown, in this embodiment, the positive half-wave rectifier circuit is composed of a rectifier diode D1 and a return diode D2. The rectifier diode D1 is connected in series between the upper arm resistor R5 and the lower arm resistor R6. The cathode of the return diode D2 is connected to the node between the upper arm resistor R5 and the anode of the rectifier diode D1. The anode of the return diode D2 is grounded.

[0035] Because alternating current voltage changes alternately with positive and negative values ​​as a sine function, with one half of the waveform being positive and the other half negative, when the voltage is positive (positive half-cycle), the live wire voltage is higher than the neutral wire voltage; when the voltage is negative (negative half-cycle), the live wire voltage is lower than the neutral wire voltage. Therefore, Figure 2In this design, when the AC input voltage is in the positive half-cycle, the current direction is from L→R1~R5→D1→R6→N, and the return diode D2 is in the reverse cutoff state. When it is in the negative half-cycle, the current direction is from N→D2→R5~R1→L, and the rectifier diode D1 is in the reverse cutoff state. This design achieves the goal of only collecting the positive half-cycle of the AC input voltage, and the input half-cycle AC voltage is sequentially processed by the voltage divider of R1~R6 to convert it into a low-voltage pulsating signal of the same frequency.

[0036] Then by Figure 2 As shown, in this embodiment, the effective voltage detection circuit 02 includes, in addition to comparator N1A, a 12V comparator power supply independently powering comparator N1A, and two threshold voltage divider resistors R8 and R9 connected in series with the 12V comparator power supply. The inverting input terminal of comparator N1A (pin 2 in the figure) is connected to the node between the threshold voltage divider resistors R8 and R9. This design not only ensures the stable and reliable operation of comparator N1A but also ensures the generation of a precise and stable preset threshold voltage. This prevents the comparison reference used for input voltage validity detection from being affected by wide variations in the input AC voltage, thereby significantly improving the accuracy and reliability of subsequent frequency calculations by the processor. Furthermore, by adjusting the resistance values ​​of the threshold voltage divider resistors R8 and R9, the lower limit of the detection threshold for the lowest effective signal can be easily set to adapt to the needs of different applications for voltage signal validity determination. This gives the circuit strong design flexibility, practicality, and versatility.

[0037] Then by Figure 2 As shown in the diagram, in this embodiment, the effective voltage detection circuit 02 further includes a positive feedback resistor R10. One end of the positive feedback resistor R10 is connected to the non-inverting input terminal (pin 3 in the diagram) of comparator N1A, and the other end of the positive feedback resistor R10 is connected to the output terminal (pin 1 in the diagram) of comparator N1A. The positive feedback resistor R10 significantly improves the circuit's noise immunity, ensuring that the output signal is a clean and stable square wave.

[0038] Then by Figure 2 As shown, in this embodiment, the effective voltage detection circuit 02 further includes a current-limiting resistor R7 and a clamping diode D4 connected in reverse parallel across the current-limiting resistor R7. The current-limiting resistor R7 is connected in series between the cathode of the rectifier diode D1 and the non-inverting input terminal (pin 3 in the figure) of the comparator N1A. This design prevents current from flowing backward from the non-inverting input terminal (pin 3 in the figure) of the comparator N1A into the rectifier output circuit of the preceding stage, thereby ensuring the normal operation of the circuit and protecting the preceding stage circuit.

[0039] Then by Figure 2As shown, in this embodiment, the optocoupler isolation circuit 03 is composed of an optocoupler isolation chip U1 and its peripheral resistors. In this embodiment, the optocoupler isolation chip U1 is a 6-pin optocoupler isolation gate driver chip, such as Toshiba's TLP5702. Pin 1 is the anode of the light-emitting diode, pin 3 is the cathode of the light-emitting diode, pin 4 is the Vee pin, pin 5 is the Vout pin, pin 6 is the Vcc pin, and pin 2 is a floating pin. The peripheral resistors include an input current limiting resistor (R11 in the figure) and an output voltage divider resistor (R12 and R13 in the figure).

[0040] The working principle of the circuit described in this embodiment is detailed below:

[0041] 1) During the positive half-wave cycle: When the input AC signal VIN is in the positive half-wave cycle and the voltage starts to rise from 0V, the current flows out from the L terminal, passing sequentially through the upper arm resistors R1, R2, R3, R4, and R5, and then through the rectifier diode D1 and the lower arm resistor R6. At this time, the return diode D2 is in the reverse cutoff state; the current flowing through R6 generates a momentary voltage V across R6. R6 The voltage V R6 After passing through the voltage divider network composed of resistors R7 and R10, the voltage is applied to the non-inverting input (pin 3) of comparator N1A. At this time, the voltage at pin 3 is Vin+=V R6 ×R10 / (R7+R10); When the input voltage VIN is low, Vin+ is less than the preset threshold voltage Vref=12V×R9 / (R8+R9) of the inverting input terminal (pin 2) of comparator N1A. The output terminal (pin 1) of comparator N1A is low (close to 0V). After isolation by optocoupler isolation circuit 03, the signal output to the processor is low. As the VIN voltage continues to rise, Vin+ also increases. When Vin+ just exceeds Vref, comparator N1A quickly flips, and its output terminal (pin 1) becomes high (close to its supply voltage, denoted as V). OUT+ After being isolated by optocoupler isolation circuit 03, the signal output to the processor becomes high level; when VIN crosses the peak and begins to drop, causing Vin+ to fall below Vref again, the output of comparator N1A quickly flips back to low level, and the signal output to the processor after being isolated by optocoupler isolation circuit 03 also becomes low level; through this process, in each positive half-wave cycle of the AC signal, as long as its amplitude exceeds the set detection threshold, the circuit will output a corresponding high-level pulse;

[0042] 2) During the negative half-wave cycle: When the input AC signal VIN is in the negative half-wave cycle, current flows out from the N terminal, through the return diode D2, and then through the upper arm resistors R5, R4, R3, R2, and R1 back to the L terminal. During this period, the anode potential of the rectifier diode D1 is lower than the cathode potential, and it is in the reverse cutoff state. Therefore, no current flows through the lower arm resistor R6 during the negative half-wave cycle. R6 Since the voltage is 0V, the voltage at the non-inverting input (pin 3) of comparator N1A is also 0V, which is always lower than Vref. Therefore, the output of comparator N1A remains low throughout the entire negative half-wave cycle.

[0043] As described above, the wide-range AC voltage frequency detection circuit of this invention can accurately convert the input sinusoidal AC signal into a square wave signal of the same frequency. Furthermore, since the power supply for comparator N1A is independent and stable, the threshold voltage Vref generated by this independent power supply will not drift with the wide range variation of the input VIN. This ensures that the flipping moment of comparator N1A is highly consistent in each cycle, thus outputting a square wave signal with neat edges and minimal jitter. After receiving this high-quality square wave signal, processor 04 can accurately calculate the frequency of the input AC power by measuring the time interval between adjacent rising or falling edges and using algorithms such as software filtering, thereby providing reliable support and basis for the safe and stable operation of industrial loads. In addition, the circuit of this invention also has the advantages of simple structure and ease of implementation, and has strong industrial practical value.

[0044] Finally, it should be pointed out that the above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model should be included within the protection scope of the present utility model.

Claims

1. A wide-range AC voltage frequency detection circuit, characterized in that, include: A positive half-wave rectifier and voltage divider circuit is used to perform half-wave rectification and voltage division on the positive half-cycle of the AC input voltage to convert it into a low-voltage pulsating signal of the same frequency. An effective voltage detection circuit includes a comparator for comparing an input low-voltage pulsating signal with a preset threshold voltage to generate a square wave signal with the same frequency as the input. as well as Optocoupler isolation circuits are used to electrically isolate the generated square wave signal for safe transmission to the processor.

2. The wide-range AC voltage frequency detection circuit according to claim 1, characterized in that: The positive half-wave rectifier voltage divider circuit includes a resistor voltage divider circuit and a positive half-wave rectifier circuit.

3. The wide-range AC voltage frequency detection circuit according to claim 2, characterized in that: The resistor divider circuit includes an upper arm resistor and a lower arm resistor, and the upper arm resistor is composed of multiple resistors connected in series.

4. The wide-range AC voltage frequency detection circuit according to claim 3, characterized in that: The resistor divider circuit also includes a Zener diode, which is connected in parallel with the lower arm resistor.

5. The wide-range AC voltage frequency detection circuit according to claim 2, characterized in that: The positive half-wave rectifier circuit is composed of a rectifier diode D1 and a return diode D2. The rectifier diode D1 is connected in series between the upper arm resistor and the lower arm resistor. The cathode of the return diode D2 is connected to the node between the upper arm resistor and the anode of the rectifier diode D1. The anode of the return diode D2 is grounded.

6. The wide-range AC voltage frequency detection circuit according to claim 1, characterized in that: The effective voltage detection circuit also includes a comparator power supply that independently powers the comparator.

7. The wide-range AC voltage frequency detection circuit according to claim 6, characterized in that: The effective voltage detection circuit also includes two threshold voltage divider resistors connected in series with the comparator power supply, and the inverting input terminal of the comparator is connected to the node between the two threshold voltage divider resistors.

8. The wide-range AC voltage frequency detection circuit according to claim 1 or 6, characterized in that: The effective voltage detection circuit also includes a positive feedback resistor, one end of which is connected to the non-inverting input of the comparator, and the other end of which is connected to the output of the comparator.

9. The wide-range AC voltage frequency detection circuit according to claim 1 or 6, characterized in that: The effective voltage detection circuit also includes a current-limiting resistor and a clamping diode connected in reverse parallel across the current-limiting resistor. The current-limiting resistor is connected in series between the cathode of the rectifier diode and the non-inverting input of the comparator.

10. The wide-range AC voltage frequency detection circuit according to claim 1, characterized in that: The optocoupler isolation circuit consists of an optocoupler isolation chip and its external resistors. The optocoupler isolation chip is a 6-pin optocoupler isolation gate driver chip, and the external resistors include an input current limiting resistor and an output voltage divider resistor.

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